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• Cattle performance and welfare are prone to be negatively affected by heat stress. • Shade is the primary heat stress mitigation method in feedlots. • Heat stress mitigation methods improved the growth performance of feedlot cattle. • Heat stress mitigation methods reduced the environmental footprints of feedlot cattle. • Heat stress mitigation methods improved the economic outcome of feedlot cattle. The increase in average global temperatures presents a challenge for the beef industry, especially in the feedlot sector where heat stress is a major animal welfare and economic concern. Shade is one of the most practical methods to mitigate heat stress in feedlot cattle. An experiment was conducted as a completely randomized design with 1 560 Bos indicus bulls (initial BW=287 kg) where three shade structure types were used to investigate the effects of different heat stress mitigation methods on cattle growth performance, environmental, and economic outcomes using live animal data, and a partial lifecycle assessment using the Integrated Farm System Model. The live animal portion of the experiment was done once a year over a 2-year period with three pen replications per treatment per year (n = 6 per treatment). Four shade structures used were conventional shade (SC ; steel shade 1.8 m2 of shade/animal), double conventional shade (DS ; steel shade 3.6 m2 of shade/animal), dome structures without fans (DSA ; 8.5 m2/animal with 98% solar radiation blocked), and domes with fans (DCA ; DSA plus three large sized low-speed fans). Each pen held 65 bulls in an area of 570 m2. Live animal data were analyzed as a completely randomized design using the GLM procedure of SAS (version 9.4) with shade type as fixed effect, pen as the experimental unit, and repetition (year) considered a random effect. Cattle housed under DCA had 22 and 20 kg heavier final body BW (P < 0.05) compared to those housed under SC and DS, respectively. Final BW of DCA and DSA cattle were similar (P > 0.05). Average daily gain, feed efficiency, and hot carcass weight were greater (P < 0.05) for cattle housed under DCA compared to the rest of the shade types. Dry matter intake was not affected (P > 0.05). When treatment results were extrapolated to the annual feedlot turnover of 209,700 animals, cattle in DSA and DCA versus SC and DS had 3–8% reductions in greenhouse gas and ammonia emission intensities. Compared to SC, DCA increased profitability by $29.66/animal, followed by DSA and DS with profit increases of $5.79 and $8.90/animal, respectively. Overall, the implementation of advanced shade structures improved cattle performance and profitability while reducing the environmental impact of beef production. [ABSTRACT FROM AUTHOR]

Farm animal welfare assessment protocols enable the capture and reporting of information to address any concerns raised by the industry or the public alike. To underpin commercial protocols, research to address validity, repeatability, and practicality, including studies to determine appropriate sampling methodology, is needed. For protocols that adopt an animal outcome-based approach, including the proposed protocol for Australian lot-fed cattle, appropriate sampling is required to ensure validity of observations. The aim of this study was to determine optimal timing and frequency of pen-side assessments. The proposed welfare assessment protocol was applied at four time points for 208 sample pens at four feedlots during a seven-month period. To determine the effect of time of day, the number of behavioural measures were reduced using Principal Component (PC) analysis, and then a Generalized Linear Mixed Model applied to consider relevant resource and environmental factors. Three primary components of cattle behaviour and demeanour were identified. PC 1 (17.61 % of total variation in the observed cattle behaviour) related to activity and rest, with cattle most active at 08:00 h and 17:00 h, and least active at 14:00 h. PC 2 (10.15 % variation) related to engagement with environment and feeding. At 17:00 h more cattle were observed to express positive welfare outcomes, such as engagement and feeding behaviours. PC 3 (7.07 % variation) captured behaviour and demeanour that reflected cattle mental state, but minimal variation was identified related to time of day. PC 1–3 varied by feedlot and visit number, and PC 1 scores also differed by cattle feeding program. Results indicate that to capture variation in cattle activity and rest, repeated assessments at two key time points; early-morning and early afternoon, are required for accurate pen-side welfare assessments of lot-fed cattle. These findings suggest further refinement of the welfare assessment protocol for lot-fed cattle is recommended to facilitate commercial adoption. • A novel animal welfare assessment protocol for lot-fed cattle was piloted. • Cattle showed repeatable patterns in behaviour that informed welfare. • The protocol successfully captured indicators of negative and positive welfare. • Pen-side behaviour assessments should occur both early-morning and mid-afternoon. [ABSTRACT FROM AUTHOR]

Though contact networks are important for describing the dynamics for disease transmission and intervention applications, individual animal contact and barriers between animal populations, such as fences, are not often utilized in the construction of these models. The objective of this study was to use contact network analysis to quantify contacts within two confined pens of feedlot cattle and the shared "fenceline" area between the pens at varying temporal resolutions and contact duration to better inform the construction of network-based disease transmission models for cattle within confined-housing systems. Two neighboring pens of feedlot steers were tagged with Real-Time Location System (RTLS) tags. Within-pen contacts were defined with a spatial threshold (SpTh) of 0.71 m and a minimum contact duration (MCD) of either 10 seconds (10 s), 30 seconds (30 s), or 60 seconds (60 s). For the fenceline network location readings were included within an area extending from 1 m on either side of the shared fence. "Fenceline" contacts could only occur between a steer from each pen. Static, undirected, weighted contact networks for within-pen networks and the between-pen network were generated for the full study duration and for daily (24-h), 6-h period, and hourly networks to better assess network heterogeneity. For the full study duration network, the two within-pen networks were densely homogenous. The within-pen networks showed more heterogeneity when smaller timescales (6-h period and hourly) were applied. When contacts were defined with a MCD of 30 s or 60 s, the total number of contacts seen in each network decreased, indicating that most of the contacts observed in our networks may have been transient passing contacts. Cosine similarity was moderate and stable across days for within pen networks. Of the 90 total tagged steers between the two pens, 86 steers (46 steers from Pen 2 and 40 steers from Pen 3) produced at least one contact across the shared fenceline. The total network density for the network created across the shared fenceline between the two pens was 17%, with few contacts at shorter timescales and for MCD of 30 s or 60 s. Overall, the contact networks created here from high-resolution spatial and temporal contact observation data provide estimates for a contact network within commercial US feedlot pens and the contact network created between two neighboring pens of cattle. These networks can be used to better inform pathogen transmission models on social contact networks. [ABSTRACT FROM AUTHOR]

Bovine respiratory disease (BRD) is an important health and economic burden to the cattle industry worldwide. Three bacterial pathogens frequently associated with BRD (Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni) can possess integrative and conjugative elements (ICEs), a diverse group of mobile genetic elements that acquire antimicrobial resistance (AMR) genes (ARGs) and decrease the therapeutic efficacy of antimicrobial drugs. We developed a duplex recombinase polymerase amplification (RPA) assay to detect up to two variants of ICEs in these Pasteurellaceae. Whole genome sequence analysis of M. haemolytica, P. multocida, and H. somni isolates harbouring ICEs revealed the presence of tnpA or ebrB next to tet (H), a conserved ARG that is frequently detected in ICEs within BRD-associated bacteria. This real-time multiplex RPA assay targeted both ICE variants simultaneously, denoted as tetH _ tnpA and tetH _ ebrB , with a limit of detection (LOD) of 29 (95% CI [23, 46]) and 38 genome copies (95% CI [30, 59]), respectively. DNA was extracted from 100 deep nasopharyngeal swabs collected from feedlot cattle on arrival. Samples were tested for ICEs using a real-time multiplex RPA assay, and for M. haemolytica, P. multocida, H. somni, and Mycoplasma bovis using both culture methods and RPA. The assay provided sensitive and accurate identification of ICEs in extracted DNA, providing a useful molecular tool for timely detection of potential risk factors associated with the development of antimicrobial-resistant BRD in feedlot cattle. • Identified two integrative and conjugative elements (ICEs) variants in Pasteurellaceae. • Detection of ICE in Pasteurellaceae by recombinase polymerase amplification (RPA). • Potential to identify cattle at high risk of developing antimicrobial-resistant BRD. [ABSTRACT FROM AUTHOR]

Although cattle can synthesize vitamin C (VC) endogenously, stress may increase VC requirements above the biosynthetic threshold and warrant supplementation. This study investigated the effects of a VC injection delivered before or after a long-distance transit event on blood parameters and feedlot performance of beef steers. Fifty-two days prior to trial initiation, 90 newly weaned, Angus-based steers from a single source were transported to Ames, IA, USA. On day 0, 72 steers (356 ± 17 kg) were blocked by BW and randomly assigned to intramuscular injection treatments (24 steers/treatment): saline injection pre- and post-transit (CON), VC (Vet One, Boise, ID, USA; 5 g sodium ascorbate/steer) injection pre-transit and saline injection post-transit (PRE) or saline injection pre-transit and VC injection post-transit (POST). Following pre-transit treatment injections, steers were transported on a commercial livestock trailer for approximately 18 h (1675 km). Post-transit (day 1), steers were sorted into pens with one GrowSafe bunk/pen (4 pens/treatment; 6 steers/pen). Steers were weighed on day 0, 1, 7, 30, 31, 56 and 57. Blood was collected from 3 steers/pen on day 0, 1, 2 and 7; liver biopsies were performed on the same 3 steers/pen on day 2. Data were analyzed as a randomized complete block design (experimental unit = steer; fixed effects = treatment and block) and blood parameters were analyzed as repeated measures. A pre-transit VC injection improved steer average daily gain from day 7 to 31 (P = 0.05) and overall (day 1 to 57; P = 0.02), resulting in greater BW for PRE-steers on day 30/31 (P = 0.03) and a tendency for greater final BW (day 56/57; P = 0.07). Steers that received VC pre- or post-transit had greater DM intake from day 31 to 57 (P = 0.01) and overall (P = 0.02) v. CON-steers. Plasma ascorbate concentrations were greatest for PRE-steers on day 1 and POST-steers on day 2 (treatment × day; P < 0.01). No interaction or treatment effects were observed for other blood parameters (P ≥ 0.21). Plasma ferric-reducing antioxidant potential and malondialdehyde concentrations decreased post-transit (day; P < 0.01), while serum non-esterified fatty acids and haptoglobin concentrations increased post-transit (day; P < 0.01). In general, blood parameters returned to pre-transit values by day 7. Pre-transit administration of injectable VC to beef steers mitigated the decline in plasma ascorbate concentrations and resulted in superior feedlot performance compared to post-transit administration. [ABSTRACT FROM AUTHOR]

Feeding cattle with on-pasture supplementation or feedlot diets can increase animal efficiency and system profitability while minimizing environmental impacts. However, cattle system profit margins are relatively small and nutrient supply accounts for most of the costs. This paper introduces a nonlinear profit-maximizing diet formulation problem for beef cattle based on well-established predictive equations. Nonlinearity in predictive equations for nutrient requirements poses methodological challenges in the application of optimization techniques. In contrast to other widely used diet formulation methods, we develop a mathematical model that guarantees an exact solution for maximum profit diet formulations. Our method can efficiently solve an often-impractical nonlinear problem by solving a finite number of linear problems, that is, linear time complexity is achieved through parametric linear programming. Results show the impacts of choosing different objective functions (minimizing cost, maximizing profit and maximizing profit per daily weight gain) and how this may lead to different optimal solutions. In targeting improved ration formulation on feedlot systems, this paper demonstrates how profitability and nutritional constraints can be met as an important part of a sustainable intensification production strategy. [ABSTRACT FROM AUTHOR]

• Faecal cortisol metabolites' relation with body temperature and behaviour was studied. • Faecal cortisol metabolites were related to indicators of heat stress. • Faecal cortisol metabolites were positively correlated with body surface temperature. • Faecal cortisol metabolites were positively correlated with standing, panting and drinking. • Respiration rate was the best indicator of the heat stress in cattle. Feedlot cattle are at times exposed to high environmental temperatures. Faecal cortisol metabolites were related to possible indicators of heat stress that could be measured under field conditions: respiratory dynamics (respiration rate), body surface temperature and adaptive behaviours, such as water consumption, posture (standing, lying), and activity (eating, drinking and rumination). Twelve (12) yearling Black Angus steers were divided into two treatment groups: a hot treatment (HOT ; n = 6) and a thermoneutral-treatment (TN ; n = 6) and individually housed in a climate-controlled facility at The University of Queensland, Australia. In the TN treatment, all animals were exposed to an ambient temperature of 20.34 ± 0.25 °C, relative humidity 71.51 ± 3.26% and Temperature humidity index (THI) 66.91 ± 0.33 throughout. In the HOT treatment group, environmental conditions were exposed to different climatic phases from thermoneutral to hot conditions, where they remained for 7 d, and then returned to TN conditions in the recovery period. The dry bulb ambient temperature (T A) and relative humidity (RH) in the pens of cattle in the HOT treatment were increased from 28 °C (daily maximum ambient temperature) and 45% RH at 0700 h to a daily maximum T A and RH of 35 °C (daily maximum ambient temperature) and 50% (THI 77) at 1100 h, which was maintained until 1600 h, after which it declined until it reached the baseline at 2000 h. In both treatments, there was a significant decrease in faecal cortisol metabolite concentration from the start to the end of the experiments they adapted to the experimental facility. The concentration of faecal cortisol metabolites was greater in the HOT treatment, compared to the TN treatment during the heat exposure period, but there was no difference in the transition or recovery periods. Respiration rate was greater in the HOT treatment during heat exposure, and it increased with ambient dry bulb temperature above 26 °C, the latter being the upper critical temperature. Although positive correlations were detected between faecal cortisol metabolites and body surface temperature measurements, particularly the shoulder and rump, as well as standing time, panting score and drinking, a stepwise regression found that faecal cortisol metabolites were only significantly correlated with one variable, respiration rate. It is concluded that respiration rate is the best indicator of the stress induced by hot conditions for cattle. [ABSTRACT FROM AUTHOR]

• Different roughage: concentrate ratio affect the intake of feedlot lambs. • Sorghum silage compared to Transvala grass hay provides higher feeding efficiency. • Diets with a higher ratio of concentrate provide greater weight gain in lambs. • Different types of roughage do not affect the carcass characteristics of lambs. • Lambs fed lower roughage: concentrate ratio diets had improvements in meat quality. This study proposes to investigate the production performance of lambs fed diets containing different roughage sources and formulated with different roughage-to-concentrate ratios (R:C). A total of 108 castrated male Santa Inês lambs aged 3–6 months, at an average body weight of 26.1 kg ± 5.6 kg were used. The experiment was set up as a randomized block design with a 2 × 3 factorial arrangement represented by two R:C ratios (400:600 or 600:400 g/kg, dry matter basis) and two roughage sources [transvala grass (Digitaria decumbens Stent cv. Transvala) hay or sorghum (Sorghum bicolor) silage], or a combination of the two sources. Six diets were tested, namely, Diet 1–400 g/kg hay +600 g/kg concentrate; Diet 2–400 g/kg silage +600 g/kg concentrate; Diet 3–200 g/kg hay +200 g/kg silage +600 g/kg concentrate; Diet 4–600 g/kg hay +400 g/kg concentrate; Diet 5–600 g/kg silage +400 g/kg concentrate; and Diet 6–300 g/kg hay +300 g/kg silage +400 g/kg concentrate. The concentrate was composed of ground corn, soybean meal, urea and a mineral mixture. The diets with the lower R:C ratio (400:600 g/kg DM) provided the highest intakes of dry matter and other nutritional components as well as increased animal performance and carcass yield parameters. Better feed efficiency was observed in the lambs fed the silage-containing diets. In conclusion, the tested roughage sources can be used in lamb diets, and the roughage level of 400 g/kg DM maximizes feed efficiency in lambs. When using hay in the diet formulation, higher weight gain rates are achieved with a R:C ratio of 400:600 g/kg; for diets formulated with silage, in turn, the recommended R:C ratio for increased weight gain is 600:400 g/kg. Thus, depending on the availability of roughage, the producer may choose one of the sources and associate it with the most adequate proportion of concentrate to maximize the performance of feedlot lambs. [ABSTRACT FROM AUTHOR]

The enrichment of meat with selenium is important to improve the intake of selenium by humans. The effects of supranutritional doses of sodium selenite or selenium-enriched yeast on performance, carcass characteristics and meat quality were evaluated using 63 Nellore cattle in a completely randomized design with two sources (sodium selenite and selenium-enriched yeast), three levels (0.3, 0.9 and 2.7 mg Se/kg DM) and control treatment (without addition of selenium). Final body weight ( BW ), average daily gain, dry matter intake and gain to feed ratio (G : F) at the end of 84 days of supplementation were not influenced by treatments (P >0.05). Values of pH, ribeye area, back fat thickness and marbling score were also not influenced by treatments (P >0.05). Dressing percentage was greater (P =0.02) in Nellore cattle supplemented with organic Se (58.70%) compared to animals supplemented with inorganic Se (57.94%). Hot carcass weight increased (P =0.05) with the increasing of Se levels in the diet. Colour, shear force (SF), cooking and drip loss remained unchanged (P >0.05); however thiobarbituric acid reactive substances was 15.51% higher with inorganic Se compared with organic Se. The selenium concentration in the meat of animals receiving organic selenium was higher (P <0.001) than that of animals receiving sodium selenite, at all levels (0.3; 0.9 and 2.7 mg/kg DM). The meat of animals receiving 2.7 mg of organic Se/kg of DM presented concentration of 372.7 μg Se/kg in the L.dorsi muscle, and the intake of 150 g of this meat by humans provides approximately 100% of the recommended Se intake (55 μg Se/day for adults). Therefore, the use of supranutritional doses of 2.7 mg Se/kg of DM, regardless of source, is a way of naturally producing selenium-enriched meat without compromising performance, carcass characteristics and quality of Nellore bovine meat. [ABSTRACT FROM AUTHOR]

• Epidemiology of ovine respiratory complex in lambs offers differences between the farm and the feedlot. • Ovine respiratory complex increases its importance according to the age of the lambs. • Ovine respiratory complex acts as a silent disease, with high number of asymptomatic animals. Ovine respiratory complex is one of the main diseases affecting lambs in many countries. Similar to other multifactorial diseases, it is highly influenced by the combination of the different factors that influence the animal, such as the environment, the production system in which they are reared or the host factors themselves. For this reason, epidemiological data of this disease are variable according to the risk factors present in each region and even in each flock. In order to understand the different options available at farm level for the epidemiological study of the ORC, the authors present results from five different studies carried out during the last years in sheep meat production systems in Spain. These studies make different approaches to the measurement of the importance of the ORC, ranging from the assessment of clinical cases and observation of lesions during necropsy to more complete analysis such as data collection on condemnations at the slaughterhouse. This practical approach should allow to analyse in a simple way the incidence of the disease in a farm and its maximum risk moments of presentation, which will be absolutely essential to design preventive plans adjusted to each situation. [ABSTRACT FROM AUTHOR]

• Zilpaterol hydrochloride increases performance and hot carcass weight, regardless of gender. • Zilpaterol hydrochloride increases muscle deposition and dressing percentage. • Meat quality and overall tenderness was not affected by zilpaterol hydrochloride. This study aimed to determine the effects of zilpaterol hydrochloride (ZH) on feedlot performance, carcass traits, feeding behavior and meat quality characteristics of Nellore steers and bulls. This study was conducted at the São Paulo State University (UNESP) feedlot, Botucatu Campus, Brazil. Seventy-two 18-month-old Nellore cattle from the same cattle herd, 36 steers and 36 bulls, were selected for this study. The experiment had a randomized block design based on the animals' initial BW, in a 2 × 2 factorial arrangement of treatments, in which the factors were ZH addition to the diet (0 or 7.5 mg of ZH/ kg of feed 20 d prior to slaughter; ZILMAX® MSD Animal Health, São Paulo, SP, Brazil) and gender (bulls or steers). The 24 pens were considered the experimental units in this study, and each treatment was replicated six times (n = 3 per pen). Cattle were fed for 112 days, and the addition of 7.5 mg of ZH/ kg of feed was done for 20 d prior to slaughter (from day 90 to day 109). A withdrawal period of three days before slaughter was respected (from day 110 to 112). During the period of ZH supplementation, cattle fed ZH presented greater final BW (516.45 vs. 512.50 kg; P ≤ 0.001), ADG (1.73 vs. 1.32 kg; P ≤ 0.001), and improved G:F by 38.1% (0.187 vs. 0.135; P ≤ 0.001), when compared to cattle not fed ZH. Nellore steers receiving ZH reduced DMI by 9% when compared to steers not fed ZH (P = 0.04); however, Nellore bulls had similar intake regardless of ZH supplementation. Overall, cattle receiving ZH improved G:F by 6.6% (0.161 vs. 0.151; P = 0.03) and increased final LM area (79.32 vs. 76.30 cm2; P = 0.04), HCW (292.75 vs. 280.00 kg; P < 0.001), and dressing percentage (56.68 vs. 55.14; P < 0.001). The interaction between ZH supplementation and gender was observed (P = 0.02) for 12th rib fat daily gain in which steers decreased their rate of fat deposition when fed ZH, but no effect was observed for bulls. A significant increase was observed (4743.12 vs. 4286.23 µm2; P = 0.03) in the average area of Semitendinosus muscle fibers of cattle supplemented with ZH; however, no main effect of ZH supplementation was observed for final marbling (P = 0.27) or shear force (P = 0.20). Overall, ZH increased performance and hot carcass weight of Nellore cattle regardless of gender. In addition, supplementation of ZH lead to similar feedlot performance and meat quality between Nellore steers fed ZH and Nellore bulls not consuming ZH. [ABSTRACT FROM AUTHOR]

Highlights • Intake during week 7 can be used to detect pens of greatest performance potential. • Intake during week 7 may help to identify pens with health or management anomalies. • Cattle with greatest performance had greater dry matter intake fluctuation in kg. Abstract The objectives of this study were: 1) To identify which specific week or weeks at the beginning of feeding period was most closely correlated with intake of net energy for gain (NEg) and dry matter (DM) for the full feedlot period of 140–180 d, and 2) to determine how various performance measurements were correlated with intake during this selected time frame. The database was compiled from one commercial feedlot, contained 2,495 pens of steers and 1,637 pens of heifers representing a total of 485,458 animals. Diets had similar composition across a 6 years period. Responses in intake of DM and NEg for the full finishing period were tested separately by including gender, initial body weight (BW) and days on feed as covariates in PROC NLIN of SAS. The PROC CORR was used to determine the correlation between intakes of DM and NEg early in the feedlot period with intake of DM and NEg for the entire finishing period. Intake periods of interest included individual weeks or the combination of weeks 5–12. Among the individual weeks, intakes of DM and NEg during week 7 were correlated most closely with intakes of DM and NEg across the entire finishing period for steers (r = 0.72) and heifers (r = 0.66). Based on mean DM intake during week 7, pens were grouped into quartiles: Top, High, Lower and Lowest. Pens of steers and heifers within the Top ¼ group during week 7 had greater (P < 0.05) final BW and average daily gain (ADG) across the full feeding period than pens of steers and heifers in other quartiles. However, G:F for steers within the Top ¼ group was lower than for pens in the Lower ¼ and Lowest ¼ groups. Pens of cattle within the Lowest ¼ group had more sick head days (P < 0.05) and greater death loss (P < 0.05) than pens of cattle of the Top ¼ group. Pens of cattle within the Top ¼ group had greater (P < 0.05) week-to-week DM intake fluctuation expressed in kg for both steers and heifers. Mean DM intake during week 7 can be utilized as an index to detect pens with the greatest potential of ADG and should help to identify pens with health or management anomalies so that proper corrective actions might be taken. [ABSTRACT FROM AUTHOR]

Rehydration and ensiling are methods to processing and preserving corn grains by which starch digestibility, nutrient availability, animal performance, and meat quality can be improved. The objective of this study was to evaluate the effect of the substitution of ground corn by rehydrated ground corn silage (RGCS) in high-concentrate diets for feedlot lambs on performance, carcass traits, and meat quality. Forty Santa Inês non-castrated male lambs were used, with an initial average body weight of 21 ± 2.8 kg (mean ± standard error) and an age of approximately 4 months. Lambs were distributed in a completely randomized design, corresponding to five treatments and eight repetitions. The treatments consisted of substitute RGCS for ground corn at levels of 0, 250, 500, 750, and 1000 g/kg of dry matter (DM) in the concentrate. The sampling and data collection (experimental period) lasted 64 days. At the end of the experimental period, the animals were subjected to a solid fast, followed by slaughter. To evaluate meat quality, both longissimus lumborum muscle were collected. The substitution of ground corn by RGCS in high-concentrate diets did not alter (P > 0.05) the meat pH, cooking losses, tenderness, juiciness, aroma, and global acceptance of meat from feedlot lambs. However, the ground corn substitution by RGCS increased linearly lightness (P = 0.016), redness (P = 0.005), yellowness (P = 0.026), and flavor (P = 0.018) of the meat. On the other hand, the shear force was linearly reduced (P = 0.003). The ground corn substitution by RGCS had no effect (P > 0.05) on the fatty acid profile and the hypocholesterolemic to hypercholesterolemic fatty acid ratio of the lambs' meat. Therefore, considering the current results, ground corn can be completely replaced by rehydrated ground corn silage in high-concentrate diets for feedlot lambs. • Rehydrated Ground Corn Silage (RGCS) can replace 100% of the ground corn (GC) in lamb diet concentrate. • Performance and carcass traits are not affected by the GC substitution for RGCS. • The meat physicochemical traits were not affected by the substitution of GC by RGCS. • The fatty acid profile and meat quality were similar when RGCS substituted GC. • Meat sensory analysis revealed that the substitution of GC for RGCS increased its taste. [ABSTRACT FROM AUTHOR]

Highlights • Moxidectin efficacy was higher than ivermectin treatment in an anthelmintic resistance context. • Cooperia L 3 was particularly reduced in post-treatment coprocultures after high doses of moxidectin. • A high dose of moxidectin avoided weight losses related to ivermectin-resistance in feedlot, where reinfection is unlikely. Abstract We evaluated the comparative plasma disposition kinetics and efficacy of moxidectin (MXD), administered by the intraruminal (IR) or subcutaneous (SC) route at two different dosage levels (0.2 and 1 mg/kg) in feedlot calves. Additionally, the efficacy was compared to an ivermectin (IVM, SC administration) treated group. This study was divided into two separate studies, the "Pharmacokinetic (PK) study" and the "Efficacy study". The "PK study" involved 24 calves free of gastrointestinal nematodes (GIN), which were allocated into 4 groups (n = 6) and treated with MXD by either the SC or the IR route at the therapeutic (MXD SC0.2, MXD IR0.2, respectively) or at fivefold the therapeutic dose (MXD SC1.0, MXD IR1.0 , respectively). Blood samples were collected from 3 h up to 14 days post-treatment. MXD concentrations in plasma samples were analyzed by HPLC. The "Efficacy study" included 125 calves naturally infected with GIN, which were allocated into five experimental groups (n = 25 each); the same four MXD-treated groups described for the "PK study", and an additional group treated by the SC route with IVM (IVM SC0.2). The efficacy of IVM given at its therapeutic dose and the different MXD groups at the therapeutic and fivefold the therapeutic dose was calculated by analysis of the individual efficacy using the package eggCounts-2.1-1' on the R software environment, version 3.5.0 (R Core Team, 2018). Daily weight gain (DWG) was also measured over the first 47 days of the fattening cycle. Independently of the administration route, MXD peak plasma concentration (C max) and area under the concentration-time curve (AUC) were higher in groups treated with the higher dose (1.0 mg/kg), whereas a longer time to reach C max (T max) was observed after the IR treatments. The observed MXD efficacies were 85% (MXD SC0.2), 94% (MXD SC1.0), 84% (MXD IR0.2) and 99% (MXD IR1.0), at day +27. At day +27, all MXD-treated groups showed higher efficacies than the group having received IVM (45%). The post-treatment Cooperia spp. L 3 counts were particularly low in the groups MXD SC1.0 and MXD IR1.0. All of the groups treated with MXD showed better DWG than the IVM SC0.2 group (P = 0.01). Dose and administration route modifications effectively improved the anthelmintic and productive performance of MXD. A high dose of MXD improved the control of IVM-resistant GIN in feedlot calves. However, this practice must be taken with caution, since MXD resistance could rapidly emerge, especially in grazing cattle. [ABSTRACT FROM AUTHOR]

Abstract This paper presents techno-economic assessment of a closed-loop integrated system combining ethanol plant, feedlot, and biodigester in the Canadian Prairies. Triticale is the primary feedstock for ethanol production. Wet distiller's grains (WDG) and thin stillage from the ethanol plant is used as feed for feedlot beef cattle. Feedlot manure is used to produce methane via anaerobic digestion (AD), for subsequent conversion to electricity and heat through a combined heat and power generation facility. Three scenarios and two system scales were investigated. Total investment in the integrated system was $38–54 (small scale) and $132–237 million (large scale). The results showed that only one scenario in a large scale case has potential to generate profit; in this case, only the feedlot generated positive net present value (NPV) due to savings in feed cost of feeding WDG. Both the ethanol plant and biodigester generated negative returns under the integrated system. Co-locating a feedlot with an ethanol plant enhances ethanol plant profitability along with generation of extra revenue from feedlot operations. Compared to the non-integrated feedlot, the integrated feedlot saves $71.51 in feed cost per cow when cattle are fed 25% WDG. Electricity and heat from the biodigester could only supply 7–20% and 46–71% of the demand of the ethanol plant respectively. Sensitivity analysis tested key factors affecting the profitability of the subsystems. The ethanol plant generates profit under higher ethanol prices. However, NPV for all biodigesters is negative, even under favourable changes in investment and electricity prices. The study also showed that incorporating straw into ethanol fermentation and biogas production was not economically profitable in comparison with single triticale grain fermentation and manure digestion. Overall results suggest need for more policy support to improve economics of anaerobic digesters under current conditions, in the context of clean technology strategies. Highlights • Economic analysis of an integrated ethanol-feedlot-biodigester system is presented. • Sensitivity analysis was conducted for each subsystem. • Utilizing WDG improves overall economics of the integrated system. • Adding straw in co-fermentation and co-digestion was not economically profitable. • Biodigesters cannot make profit without established co-product markets. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Highlights • Lambs offered WSC ad libitum had a greater ADG, off-test, and hot carcass weight. • Lambs offered WSC had greater G:F and lower feed costs per gain compared to AP. • Lambs offered WSC had lighter total GI tract weights compared to lambs offered AP. • Limit-feeding WSC decreased BF and visceral fat in lambs compared to ad libitum WSC. Abstract The objective of the present study was to assess energy source, level, and sex of the lamb, on the growth, performance, and carcass characteristics of long-fed lambs (218 days on feed and 294 days of age). Ewe (n = 24) and wether (n = 24) lambs were blocked by sex and stratified by initial weight to pens containing four lambs within a pen, with two pens of each sex assigned to each of the three dietary treatments. The three diets offered were ad libitum access (WSC100) to whole shelled corn (WSC), 85% access of the ad libitum WSC diet (WSC85), and ad libitum access to alfalfa pellets (AP). Lambs offered WSC100 had greater (P < 0.05) ADG when compared with lambs offered WSC85 or AP, which resulted in a greater (P < 0.05) final body weight (93.6, 83.4, 86.0 kg, respectively). Lambs offered AP had a greater (P < 0.01) DMI when compared with lambs offered WSC100 or WSC85. Wether lambs had a greater final body weight (90.6 vs. 87.5 kg; P < 0.05), ADG (P < 0.05), and DMI (P < 0.01) when compared with ewe lambs. Lambs offered WSC had a greater (P < 0.01) G:F and a lower (P < 0.01) feed cost per unit of gain when compared with lambs offered AP. Lambs offered WSC100 had a greater final body weight (P < 0.05), hot carcass weight (HCW; P < 0.05) and visceral fat weight (P < 0.01) compared with lambs offered AP or WSC85. Lambs consuming WSC100 or WSC85 had a lighter reticulum (P < 0.01), omasum (P < 0.01), small (P < 0.01) and large intestine (P < 0.05), cecum (P < 0.05), and total tract weight (P < 0.01), but a greater (P < 0.05) amount of kidney fat compared with lambs offered AP. Wether lambs had a greater (P < 0.05) HCW, but a lighter (P < 0.05) small intestine weight when compared with ewe lambs. Lambs offered WSC100 had a greater final body weight (P < 0.01) and produced carcasses with a greater HCW (P < 0.01), backfat thickness (P < 0.05), body wall thickness (P < 0.01), yield grade (P < 0.05), and marbling score (P < 0.05) when compared with carcasses from lambs offered AP or WSC85. However, carcasses from lambs offered WSC100 had a lower percentage of boneless closely trimmed retail cuts (P < 0.05) when compared with carcasses from lambs offered AP or WSC85. Both WSC100 and WSC85 diets produced lamb carcasses with greater (P < 0.01) dressing percentages and kidney fat weights when compared with carcasses from lambs offered AP. Wether lamb carcasses had a greater final body weight, HCW, dressing percentage, and BWT when compared with ewe lamb carcasses. Overall, lambs offered WSC100 or WSC85 grew faster and more efficiently with a lower feed cost of gain. Lambs offered WSC100 and WSC85 also had a lower total digestive tract weight compared with lambs offered AP. However, feeding WSC100 produced carcasses with greater amounts of fat in multiple fat depots when compared with lambs offered AP or WSC85. [ABSTRACT FROM AUTHOR]

Mycoplasma bovis can be a bacterial inhabitant of the upper respiratory tract of healthy bovines. In body regions other that the upper respiratory tract however, M. bovis is associated with a number of clinical syndromes such as bovine respiratory disease (BRD). This study used two enzyme-linked immunosorbent assays to assess the sero-status of M. bovis -specific antibodies in Australian feeder cattle at the time of feedlot induction and at approximately 42 days on feed (follow-up). The apparent sero-prevalence of M. bovis -specific antibody at induction was estimated to be 3.5% (95% confidence interval [CI] 2.0–5.0%, 47/1354) and 25.3% (95% CI 21.9–28.8%, 343/1354) at follow-up. Exposure to M. bovis between induction and follow-up as demonstrated by an increase in serum antibodies was estimated to be 19.4% (95% CI 16.2–22.6%, 261/1349). Risk factors associated with sero-positivity at feedlot induction included the region where animals were 28 days prior to induction and saleyard exposure at least 27 days prior to induction. Risk factors associated with a sero-increase between induction and follow-up included breed, source region and access to water shared with an adjoining pen of animals. Of these, shared pen water was considered the most important (odds ratio [OR] 3.3, 95% CI 1.5–7.4, p = 0.003). Animals exposed to M. bovis between induction and follow-up were at a substantially increased risk of BRD (OR 2.2, 95% CI 1.4–3.4, p = 0.001). This is the first Australian study that has identified risk factors for M. bovis sero-positivity and sero-increase and shown an association between sero-increase and the risk of BRD in the feeder cattle population. These findings suggest that M. bovis is a significant pathogen in the Australian feeder cattle population. In addition, identification of defined risk factors associated with an increased risk of exposure to M. bovis can assist in the development of targeted control measures to reduce the economic impact of M. bovis associated disease and BRD in feeder cattle. [ABSTRACT FROM AUTHOR]

Highlights • Co-mingling at an auction market did not influence airways bacterial communities. • Bacterial diversity in the nasopharynx decreased after feedlot placement. • Relative abundance of Mycoplasma significantly increased after feedlot placement. • Composition of nasopharyngeal bacterial communities differed between feedlots. Abstract The objective was to study effects of transportation to and co-mingling at an auction market on nasopharyngeal and tracheal bacterial communities of feedlot cattle. Two groups of 30 Angus-cross heifers were studied from weaning to 28 d after arrival at a feedlot. For each group, half the heifers were either transported directly to a feedlot after weaning (RANC) or transported to and co-mingled at an auction market for 24 h before being placed in a feedlot (AUCT). Deep nasal swabs (DNS) and trans-tracheal aspirates (TTA) were collected at weaning (d0) and at on-arrival processing at the feedlot (d2). At 7 (d9) and 28 d (d30) after arrival, DNS were repeated. The DNA was extracted from DNS and TTA and the V4 region of the 16S rRNA gene sequenced (MiSeq). Alpha diversity analysis did not reveal differences between AUCT and RANC. However, bacterial diversity decreased over time in the nasopharynx, especially at d9. Although beta-diversity was not different between AUCT and RANC, interval after arrival and feedlot where heifers were placed affected composition of the nasopharyngeal bacterial communities. In both groups, a large increase in Mycoplasma was observed after arrival; in one group, Mycoplasma bovis was dominant at d9 and remained dominant until d30. However, in the other group, Mycoplasma dispar dominated at d9 and was replaced by Moraxella at d30. We concluded that transportation to and co-mingling at an auction market for 24 h did not significantly influence diversity or composition of nasopharyngeal or tracheal bacterial communities. [ABSTRACT FROM AUTHOR]

This study was conducted at beef cattle feedlots, over two years in southern Alberta Canada, and focused on deriving the ammonia, methane, nitrous oxide and carbon dioxide emissions from two feedlots from June/July to October. Line-averaging sensors were used to measure ambient gas concentrations in the vicinity of the feedlots, and an inverse dispersion method was used to calculate emissions. Results show that ammonia and methane emissions were consistent with that measured from other studies. Both feedlots lost about 40% of the nitrogen feed intake as ammonia. The emission of nitrous oxide, when compared on a greenhouse gas bases, was similar to the methane emission. A diet difference between feedlots coincided with a slight difference in feedlot methane emission. There was good agreement between previously reported ammonia and methane emission rates and those derived in our feedlot study. Further evaluation of the underlying relationships causing variation in emissions should follow. A key to understanding emissions at commercial feedlots is to fully engage the management data available. [ABSTRACT FROM AUTHOR]

Forty-eight bulls with an initial body weight (BW) of 408.4 ± 22.2 kg (age = 21 ± 2 months) were used in a randomized complete block design arranged in a 2 × 2 factorial design. The treatments were diets without virginiamycin (VM−) or with virginiamycin, at 25 mg/kg of dry matter (DM, VM+), and diets without crude glycerin (CG−) or with crude glycerin, at 100 g/kg DM (CG+). The cold carcass weight and cold carcass dressing (P ≤ 0.05) was greater in bulls fed crude glycerin diets. Total unsaturated fatty acids (UFA) were 6.08% higher, and cooking weight loss was 10% lower in bulls fed CG+ diets, compared to bulls fed CG− diets (P = 0.0081). Crude glycerin at 100 g/kg DM could be a suitable replacement for VM, as it led to a slight increase in UFA deposition in meat. However, simultaneous administration of VM and CG did not positively affect performance and carcass traits of feedlot Nellore cattle. [ABSTRACT FROM AUTHOR]

Natural pastures constitute a large proportion of the feed resource base for meat and milk production in Sub-Saharan Africa. However, there is increasing use of agro-industrial by-products, especially those that are cereal-based as supplementary feedstuff to grazing animals and in diets under semi-intensive and intensive production systems. This study evaluated the influence of feeding systems on rumen environment, degradability and passage kinetics. Six Ankole x Friesian F1 crossbred steers weighing 339 ± 29 kg (about two years of age), each fitted with permanent rumen cannula were used in a replicated 3 × 3 Latin square design (n s = 2). Two steers were allocated per period to one of three feeding systems i.e. (1) sole grazing (control), (2) control plus concentrate supplement (composition g/kg DM: 375 maize bran, 559 brewer's spent grain, 62.5 molasses and 3.75 NaCl), and (3) feedlot systems where steers were fed total mixed ration (TMR) comprising g/kg DM: 200 maize stover, 300 maize bran, 447 brewers’ spent grain, 50 molasses and 3 NaCl. Data was collected on rumen pH, ammonia-nitrogen (NH 3 -N), volatile fatty acids (VFA) and degradability of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF). Rumen pH was lowest (P < 0.001) at feedlot (5.3) but highest (P < 0.001) under sole grazing (6.2). Rumen NH 3 -N ranged between 62.8 and 120 mg/l and was higher (P < 0.001) in sole grazing than in grazing but supplemented steers and those at the feedlot. Total VFA concentration for sole grazing steers (124 mmol/Mol) was higher (P < 0.05) than values observed under feedlot (102 mmol/Mol) while grazing but supplemented steers showed an intermediate value (108 mmol/Mol), not differing significantly from the two other systems. Molar proportion of acetate was higher (P < 0.001) in grazing steers compared to values for either grazing but supplemented or those under feedlot while the reverse was true for propionate. The degradation characteristics of DM, CP and NDF were generally higher in sole grazing steers. Although, in most cases, the influence of feeding system on degradability was dependent on the type of feedstuff, feeding systems did not influence total mean retention time. The high extent of DM, CP and fiber degradation in grazing steers compared to supplemented and feedlot steers demonstrates that forage diversity under grazing positively influences degradability. However, attention to the nature and fermentation characteristics of proteins and carbohydrate sources and how they modify rumen environment in different production systems is needed to improve utilization of supplements and TMR. [ABSTRACT FROM AUTHOR]

Peripheral lymph nodes (LNs) located in the fatty tissues of beef carcasses have been shown to harbor Salmonella and, thus, potentially contaminate ground beef. Salmonella prevalence within LNs is known to differ among feedlots. Two South Texas feeding operations (identified as locations A and B) known to harbor salmonellae in the feedlot environment, while historically producing cattle with opposing rates (one ''high'' and one ''low'') of Salmonella prevalence in LNs, were used in this study. To determine whether this difference was due to cattle source or factors associated with different stages of feeding, weanling steers of common and known origin were followed through normal feeding stages at both operations. Eighty Angus-sired beef steers were harvested at each of four feeding stages: 1, postweaning; 2, background or stocker; 3, 60 days on feed; and 4, 120 days on feed. Left and right subiliac and superficial cervical LNs (n¼ 304) were collected from each carcass, and similar node types were pooled by animal (n¼152). Results showed a difference (P < 0.05) in prevalence of Salmonella in bovine lymph nodes between location A and location B and among feeding stages in location B. Salmonella was not isolated from any feeding stage 1 (postweaning) or location A LN samples. Within location B, there was an increase in Salmonella prevalence as cattle moved into later stages of feeding: at 22.2% (4 of 18), 77.8% (14 of 18), and 94.4% (17 of 18) for feeding stages 2, 3, and 4, respectively. Although the reasons for the differences seen between feeding operations and for increased Salmonella prevalence in LNs at later feeding stages remain unexplained, these results indicate that factors other than cattle source are likely influencing Salmonella prevalence in LNs. [ABSTRACT FROM AUTHOR]

There is increasing interest in methods for the habituation of feral rangeland goats to intensive farming conditions. We tested whether there were production performance and behavioural differences between groups of rangeland goats in an intensive farming system that were either exposed to a high degree of human interaction (HI, n = 60) or low degree of human interaction (LI, n = 60) over 3 weeks. In the HI group, a stockperson entered the pens twice daily and calmly walked amongst the goats for 20 mins. In the LI group, a stockperson only briefly entered the pens to check water/feed (daily/weekly). At the end of each week the goats were weighed and drafted into 12 subgroups of 10 animals (i.e. 6 sub-groups per treatment). Each sub-group was then tested for agonistic behaviour, avoidance of humans, and flight response. During the flight response test video footage was collected and later used for analysis using Qualitative Behavioural Assessment (QBA). For QBA analysis, the videos of each group, taken each week, were shown in random order to 16 observers who used their own descriptive terms to score the groups’ behavioural expression. There was a significant interaction between treatment and time on body mass (F 3,174 = 5.0; P < 0.01), agonistic behaviour (F 3,12 = 4.3; P < 0.05) and flight speed (F 3,12 = 3.9; P < 0.05), with the HI group having significantly higher average body mass ( P < 0.05), fewer agonistic events ( P < 0.05), and a slower flight speed ( P < 0.05) than the LI group after the three weeks. Two main QBA dimensions of behavioural expression were identified by Generalised Procrustes Analysis. QBA dimension 1 scores differed between treatments ( P < 0.05); HI goats scored higher on QBA dimension 1 (more ‘calm/content’) compared to LI goats (more ‘agitated/scared’). QBA dimension 1 scores were significantly negatively correlated with the number of agonistic contacts (R s = −0.62, P < 0.01), and flight speed (R s = −0.79, P < 0.001), and significantly positively correlated with body mass (R s = 0.68, P < 0.001) of the goats over the 3 weeks of the experiment. QBA dimension 2 scores were not significantly different between treatments or over time. Findings from this study support the hypothesis that production performance and behavioural measures can distinguish behavioural changes in rangeland goats that were likely a result of habituation to human interaction in an intensive feedlot. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of the energy restriction of gestation of adult ewes from day 45 to day 115 on lamb live performance parameters, carcass and meat traits. In experiment I, dietary energy was restricted at 70% of the metabolizable energy (ME) requirements, after which ewes were re-fed ad libitum until lambing. In experiment II, dietary energy was restricted at 60% of the ME requirements, and ewes were re-fed to ME requirements until lambing. All ewes grazed together from the end of the restriction periods to weaning. Lambs were weaned and lot fed until slaughter. Feed intake, weight gain and feed efficiency were recorded, and body fat thickness and ribeye area (REA) were measured in the longissimus thoracis muscle. After slaughter, carcass weight and yield, fat depth, carcass and leg length, and frenched rack and leg weights and yields were determined. Muscle fiber type composition, Warner-Bratzler shear force, pH and color were determined in the longissimus lumborum muscle. In experiment I, energy restriction followed by ad libitum feeding affected lamb birth weight (P<0.05); however, no effects (P>0.05) were observed on later BW, REA, BF or carcass traits. Lambs born to non-restricted-fed ewes had higher (P<0.05) weight and yield of the frenched rack cut and their meat tended (P=0.11) to be tender compared with that of lambs from restricted ewes. The percentage of oxidative muscle fibers was lower for lambs born to non-restricted ewes (P<0.05); however, no effects of ewe treatment were observed on other muscle fiber types. For experiment II, energy restriction followed by ME requirements feeding, affected (P<0.01) pre-weaning live weight gain, weaning and final weights. Lambs from restricted ewes had higher (P<0.05) feed intake as % of leg weight and a trend to be less efficient (P=0.16) than lambs from unrestricted dams. Ribeye area and BF were not influenced by treatment. Treatment significantly affected slaughter weight, but had no effects on carcass yield and traits or on meat traits. The results obtained in both experiments indicate submitting ewes to energy restriction during gestation affects the performance of their progeny but the final outcome would depend on the ewe’s re-feeding level during late gestation and the capacity of the offspring to compensate the in utero restriction after birth. [ABSTRACT FROM PUBLISHER]

A decision-support, modeling tool is developed that can project future cattle growth patterns in a feedlot based on a low dimensionality dataset available at the start of the feeding process. This work adapts the predictive performance of two well-known statistical machine modeling tools, gradient boosting and random forest regression, to predict future cattle growth. Time series analysis techniques are then used to create an ensemble method that further improves prediction accuracy from individual modeling outputs. Hierarchical clustering techniques are used to leverage projected growth patterns to increase group homogeneity when assigning cattle to different feeding pens. Finally, a profit maximization method is developed that estimates the optimal time each individual cattle should remain in the system under different revenue and cost estimates. The purpose of this work is to incentivize the implementation of modern statistical learning tools in cattle management operations, especially within low-to-mid scale operations that traditionally rely on the expertise of its workers and have limited cattle and process information. Access to ‘off-the-shelf’ statistical learning tools, requiring minimal user-interaction, not only enhances prediction accuracy but helps automate operational decisions. This results in higher process efficiencies and improved standardization practices, while also helping identify profit opportunities. Finally, integrating these components into a single operating framework allows the tool to adapt to changes in data characteristics, which is especially important within non-standardized processes. We show the application of this tool through a case study implementation on a mid-scale operation in the northwestern state of Sonora, Mexico. From our case-study results, it was found that the modeling tool can satisfactorily predict growth patterns based on a low-dimensional set. It also can also capture historic decision-making when segmenting cattle into homogenous groups during their feeding process. Furthermore, it can help identify profit opportunities when estimating optimal cattle system times under varying market conditions. [ABSTRACT FROM AUTHOR]

This study investigated the potential to produce premium grade (>22 kg carcass weight and fat score 2–4 [10–20 mm GR range]) Australian lambs using feeds available in late spring to summer to meet a growing demand from growing international and local markets. Second cross lambs (Poll Dorset × [Border Leicester × Merino]) were fed either: lucerne pasture (Lucerne, Medicago sativa L.); annual ryegrass ( Lolium rigidum Gaud.) with sub-clover pasture ( Trifolium subterranean L.) (Ryegrass); a combination of annual ryegrass based pasture and a commercial finisher pellet (RyeFeedlot) or a commercial finisher pellet (Feedlot). Lambs were weaned, adapted to diet for 2 weeks and fed for a further 6 weeks. For the RyeFeedlot treatment, pellets were offered at 300 g/day/head from week 1–4 and then at 500 g/day/head from week 5–8. After 8 weeks of feeding, lambs were transported to a commercial abattoir, slaughtered and carcass traits assessed. Chemical analyses of the feedstuffs showed, estimated metabolisable energy (ME) concentration was highest for the Feedlot ration, intermediate for RyeFeedlot and Ryegrass and lowest for Lucerne, while crude protein (CP) concentration was highest for Lucerne, intermediate for Feedlot and lowest for RyeFeedlot and Ryegrass. Despite lower (P < 0.05) DMI, ME and CP intake, lambs on the Ryegrass treatment grew faster ( P < 0.05), achieved heavier body weight ( P < 0.04) and carcass weight ( P < 0.002) than RyeFeedlot fed lambs. Feed efficiency (feed per gain) was higher (P < 0.001) for Ryegrass and Lucerne than for Feedlot and RyeFeedlot treatments. Daily DM and ME intakes were greater ( P < 0.05) for lambs offered the Feedlot treatment than those fed the Lucerne treatment, but carcass weights and carcass yield (dressing%) did not differ between these groups. Carcass weight ( P < 0.002) was lowest for lambs offered the RyeFeedlot treatment compared with all other groups. Dressing percentage was higher ( P < 0.001) for lambs fed Lucerne and Feedlot treatments compared with lambs fed RyeFeedlot and Ryegrass treatments. On average, lambs from the RyeFeedlot treatment produced carcasses suitable for the lighter end of the local market (18 kg), while Feedlot and Lucerne treatments produced carcasses suitable for export markets (22 kg), however lambs fed the Ryegrass treatment produced carcasses with >18 kg but less than 22 kg required for the Australian national market. The number of lambs reaching 22 kg carcass weight was 63, 54, 44 and 9% for Lucerne, Feedlot, Ryegrass and RyeFeedlot treatments, respectively and 0, 8, 0 and 22%, respectively were below 18 kg. The results demonstrate that lucerne based pastures have the potential to consistently produce premium grade carcasses for growing export and local markets similar to feedlot rations. [ABSTRACT FROM AUTHOR]

The effects of three dietary energy treatments on the feedlot production characteristics of Boer goats were investigated, along with the time spent under feedlot conditions. A total of 66 goat kids with an average weight of 22.2 ± 3.51 kg were housed in individual pens at Elsenburg research farm. At the start of the trial, the goats were randomly allocated to one of three finisher diets that vary in energy content; low, medium and high energy (11.3, 12.0, and 12.7 MJ ME/kg feed, respectively). The goats were divided further into groups of about 15 goats that were slaughtered at a registered abattoir after 40, 76, 112 and 146 days in the feedlot. During the trial period, goats were supplied their respective trial diets ad libitum . Orts were weighed back once a week in order to determine feed intake. Growth was monitored by weighing the goats weekly. The live weights of the goats increased linearly (20.939 + 0.191 x , where x represents days in feedlot) throughout the trial period. Overall, goats on the high energy diet had the lowest growth rate (202.0 g/day versus 221.9 and 234.9 g/day for goats on the low and medium diets, respectively; P < 0.05). This may be as a result of the high starch content affecting the rumen environment and thus the utilization of nutrients for growth. Goats fed the low and medium energy diets presented the higher feed intakes (1236.4 and 1168.6 versus 1002.4 g/day for low, medium and high energy diets, respectively; P < 0.01). A tendency was observed for the feed conversion ratio (FCR) of goats on the high energy diet to be lower than that of the low and medium energy diets (P = 0.06), while the FCR of the goats did not vary with time spent in the feedlot (P = 0.40). Goats on the low energy diet had a lower dressing out percentage (45.8%, compared to 46.1 and 47.1%, for the low medium and high energy diets, respectively). This may be attributed to the higher proportion of fibre in the feed, which increases the gut fill and affects the digestibility of the feed. It was also observed that goats were able to adjust their level of feed intake in response to the amount of energy supplied in the diet. It is suggested that the diet with a medium energy content (12.0 MJ ME/kg feed) closely resembles the requirements of Boer goats for growth and exhibits the best production characteristics. [ABSTRACT FROM AUTHOR]

Lambs are commonly weaned around 60 d of age in the Eastern United States, but this age is also a time for lambs to apply long-term feeding strategies learned from adult animals. There is minimal evidence on how weaning strategies may affect long-term adaptation of feeding behavior. The objective of this study was to assess the effect of social and environmental factors at weaning on short- (3 d post-weaning) and long-term (8 wk post-weaning) feeding, lying, and standing idle behavior of lambs on pasture or in a feedlot. Two experiments tested this objective: Experiment 1 investigated social dynamics at time of weaning for lambs housed on pasture, and Experiment 2 investigated the effect of weaning into a feedlot compared to a pasture environment. At 60 d of age, 72 crossbred twin lambs were assigned to one of four treatments: lambs weaned and placed with similar-aged lambs onto pasture (W); lambs weaned and placed with similar-aged lambs and non-related adult ewes onto pasture (SF); lambs that remained with their dam on pasture (E); and lambs weaned and placed with similar-aged lambs into a feedlot (FL). Each treatment had three replicates with six lambs/replicate. Behavioral data were collected with instantaneous scan sampling for 15 h/d for 55 d. During the first 3 d after weaning in Experiment 1, W lambs spent more time standing than SF lambs (P = 0.03), and all lambs decreased standing idle time over the 3 d (P < 0.0001). During the 8 wks after weaning, W and SF lambs spent more time grazing (P = 0.03) and less time lying (P = 0.02) compared to E lambs. In Experiment 2, feeding time of FL lambs increased on d 3 compared to d 1 and 2 (P < 0.05). However, there was no effect of week on feeding, lying, or standing time over the long-term period (P > 0.05). When the time-budgets of lambs from both experiments were compared, W lambs spent 39.2% more time grazing compared to the amount of time that FL lambs spent feeding. Results suggest that keeping non-related adult ewes (SF) with weaned lambs did not influence the grazing and lying behavior of lambs on pasture. Lambs that stayed with their dams and were weaned later (E) had the lowest grazing time, likely because they are still receiving milk. Lambs in the feedlot environment increased their time spent feeding in the first few days, suggesting an initial adaptation to stress after weaning. [ABSTRACT FROM AUTHOR]

A total of 127 Nellore bulls classified as low and high residual feed intake (RFI), from three selection lines, were evaluated in five experiments aiming to identify associations between RFI, carcass, and meat quality traits. Feedlot performance, carcass traits, and meat quality of Longissimus muscle were evaluated. A mixed model including the fixed effects of RFI class, selection line, interaction between RFI class and selection line, and age at slaughter as a covariate, and the random effects of diet within experiment and experiment was used, with means compared by the t -test. Feed intake average difference was 0.962 kg/day; low RFI animals consumed 0.479 kg/day less feed and high RFI animals consumed 0.483 kg/day more feed than expected. No differences between RFI classes were detected for most of studied variables, demonstrating the absence of unfavorable associations between RFI and carcass and meat quality traits. Low RFI Nellore animals use feed efficiently and produce good quality carcasses and meat. [ABSTRACT FROM AUTHOR]

The objective of the study was to compare ad libitum or restricted access of whole shelled corn (WSC) versus ad libitum alfalfa pellets, and sex of the lamb, on lamb growth and performance. Ewe (n = 48) and wether (n = 48) lambs were blocked by sex and stratified by initial weight to pen. The three diets offered were ad libitum access of a WSC diet, 85% access of ad libitum WSC diet, or an ad libitum access of an alfalfa pellet diet. There were four lambs per pen, and eight replicate pens per dietary treatment. Ewe and wether lambs were removed from the study when pens reached an average weight of 59.0 and 63.5 kg, respectively. Average daily gain (ADG) of lambs offered the ad libitum WSC diet was greater (P < 0.05) than lambs offered the restricted WSC and alfalfa pellet diets, which resulted in fewer (P < 0.01) days on feed for lambs offered ad libitum WSC. Lambs offered alfalfa pellets had a greater (P < 0.01) daily dry matter intake (DMI) than lambs offered the WSC diets. Wether lambs had greater (P < 0.01) daily DMI when compared with ewe lambs. Gain to feed ratio was greatest (P < 0.01) for lambs offered ad libitum access to WSC, followed by lambs offered restricted WSC, and lambs offered the alfalfa pellet diet. The cost of whole shelled corn was $0.15/kg, the cost of alfalfa pellets was $0.60/kg, and the cost of supplements was $0.51/kg on an as-fed basis. The resulting feed cost of gain was greatest (P < 0.01) for lambs offered alfalfa pellets, followed by lambs offered restricted WSC, and lastly lambs offered ad libitum WSC. Lambs offered the WSC diets produced a greater hot carcass weight (HCW; P < 0.01) and greater (P < 0.01) dressing percent when compared with lambs offered alfalfa pellets. Lambs consuming ad libitum WSC had a greater amount (P < 0.05) of kidney fat when compared with lambs consuming a restricted diet of WSC or ad libitum access to alfalfa pellets. Lambs consuming either of the WSC diets produced a greater (P < 0.05) amount of visceral fat when compared with lambs offered alfalfa pellets. Lambs offered alfalfa pellets had greater tissue weight of the reticulum (P < 0.05), omasum (P < 0.01), and total digestive tract (P < 0.05), consistent with the lower dressing percentage observed. Lambs offered WSC had greater (P < 0.05) backfat and body wall thicknesses, loin marbling scores, and yield grades (P < 0.01) when compared with lambs offered alfalfa pellets. Wether lambs had a greater (P < 0.05) final BW and HCW when compared with ewe lambs. Overall, lambs offered ad libitum WSC grew more efficiently at a lower cost of gain while producing carcasses with greater amounts of fat, whereas lambs offered alfalfa pellets had a lower dressing percentage and a greater total digestive tract weight. [ABSTRACT FROM AUTHOR]

The effects of differing post-weaning management systems applied during the wet season were evaluated on the performance of 108 young Nelore ( Bos taurus indicus ) bulls finished on grasslands or feedlot system during the dry season. In Exp. 1, three grazing heights (15 cm, 25 cm, and 35 cm) of Brachiaria brizantha (Hochst ex A. Rich) Stapf Marandu were evaluated during the wet season with bulls receiving 0.3% of body weight (BW) in supplementary feed. In Exp. 2, supplementation levels were decreased as grazing heights were increased such as: (1) low height (15 cm) and high supplementation (0.6% BW) (LH–HS); (2) moderate height (25 cm) and moderate supplementation (0.3% BW) (MH–MS); or (3) high height (35 cm) with no supplementation (HH–NS). In both experiments, at the end of the wet season, a half of the bulls were finished on grasslands and receiving 1.0 kg/100 kg BW of dietary supplementation while the remaining bulls were placed in a feedlot system. A non-linear regression test was applied (linear plateau) to estimate the point of stabilization of DMI on feedlot. The experimental design was completely randomized in a factorial arrangement 3 (post-weaning system) × 2 (finishing systems), consisting of three replicates (lots of three bulls) per treatment ( n = 18, each Exp.). In the Exp. 1, the post-weaning system using 35 cm of grazing height had greater BW ( P = 0.04) through the finishing phase in comparison with bulls grazing 15 cm of grazing height. However, the ADG during the initial 21 days of the finishing phase was changed by grazing height used during the post-weaning phase ( P = 0.004), and by finishing system ( P = 0.007). The post-weaning system did not alter the carcass weight ( P = 0.63), but the bulls finished on grasslands exhibited greater carcass weight ( P = 0.02) than bulls finished on feedlot. In the Exp. 2, non-supplemented bulls (HH-NS) took a longer time (± 10%) to DMI stabilization on feedlot ( P < 0.01). There were no changes in the carcass weight caused by post-weaning system ( P = 0.84), or by finishing system ( P = 0.14). The evaluated systems combining increasing grazing height and decreasing supplementation level during the post-weaning phase can be used during the wet season according to the economic background or production target, once these systems do not influence the finishing phase. [ABSTRACT FROM AUTHOR]

The objective of the current study was to determine the effects of maternal MP restriction or supplementation during late gestation on male offspring feedlot performance, carcass characteristics, and nitrogen retention. In yr 1, maternal dietary treatments were applied at d 100 of gestation, were similar in total energy, and contained: 60MP1 : 60% of MP requirements; 80MP1 : 80% of MP requirements; and 100MP1 : 100% of the MP requirements on a DM basis during late gestation. In yr 2, maternal dietary treatments were similar in total energy and contained: 60MP2 : 60% of MP requirements; 100MP2 : 100% of the MP requirements; and 140MP2 : 140% of MP requirements on a DM basis during late gestation. In yr 1, there was no effect ( P ≥ 0.14) of maternal dietary treatment on initial BW, final BW, ADG, G:F, or morbidity. There was a quadratic effect ( P = 0.04) for days on feed, with the 80MP1 lambs being on feed longer than the 60MP1 and 100MP1 lambs. A quadratic effect ( P = 0.05) was also observed for DMI, with the 80MP1 wethers consuming less feed than the 60MP1 and 100MP1 wethers. There was no effect ( P ≥ 0.06) of maternal MP intake during late gestation on the carcass characteristics or the majority of N balance parameters of initial BW, DM, NDF, ADF, or N digestibility, daily fecal N excretion, or daily N balance of wethers in yr 1. However, daily urinary N excretion per unit of initial BW was linearly reduced ( P = 0.02) as MP intake increased and daily digested N retained increased linearly ( P = 0.04) as maternal MP increased. There was a treatment × day interaction ( P = 0.004) for serum urea N concentrations. The 60MP1 wethers had greater serum urea N concentrations on d 16, 18, 19, and 20 ( P ≤ 0.04) than 80MP1 and 100MP1 wethers; and on d 17 ( P = 0.05) compared with 80MP1 wethers. In yr 2, there was no effect ( P ≥ 0.18) of maternal dietary treatment on initial BW, final BW, ADG, G:F, or morbidity. There was a linear increase ( P = 0.04) in DMI as maternal MP increased from 60 to 140% of MP requirements. Carcass characteristics ( P ≥ 0.29) and N balance parameters ( P ≥ 0.24) in yr 2 were not affected by ewe MP intake during late gestation. These results suggest that maternal MP intake above or below requirements during late gestation may not affect wether feedlot performance or carcass characteristics. [ABSTRACT FROM AUTHOR]

Results obtained from a nationwide longitudinal study were extended to estimate the population-level effects of selected risk factors on the incidence of bovine respiratory disease (BRD) during the first 50 days at risk in medium-sized to large Australian feedlots. Population attributable fractions (PAF) and population attributable risks (PAR) were used to rank selected risk factors in order of importance from the perspective of the Australian feedlot industry within two mutually exclusive categories: ‘intervention’ risk factors had practical strategies that feedlot managers could implement to avoid exposure of cattle to adverse levels of the risk factor and a precise estimate of the population-level effect while ‘others’ did not. An alternative method was also used to quantify the expected effects of simultaneously preventing exposure to multiple management-related factors whilst not changing exposure to factors that were more difficult to modify. The most important ‘intervention’ risk factors were shared pen water (PAF: 0.70, 95% credible interval: 0.45–0.83), breed (PAF: 0.67, 95% credible interval: 0.54–0.77), the animal’s prior lifetime history of mixing with cattle from other herds (PAF: 0.53, 95% credible interval: 0.30–0.69), timing of the animal’s move to the vicinity of the feedlot (PAF: 0.45, 95% credible interval: 0.17–0.68), the presence of Bovine viral diarrhoea virus 1 (BVDV-1) in the animal’s cohort (PAF: 0.30, 95% credible interval: 0.04–0.50), the number of study animals in the animal’s group 13 days before induction (PAF: 0.30, 95% credible interval: 0.10–0.44) and induction weight (PAF: 0.16, 95% credible interval: 0.09–0.23). Other important risk factors identified and prioritised for further research were feedlot region, season of induction and cohort formation patterns. An estimated 82% of BRD incidence was attributable to management-related risk factors, whereby the lowest risk category of a composite management-related variable comprised animals in the lowest risk category of at least four of the five component variables (shared pen water, mixing, move timing, BVDV-1 in the cohort and the number of animals in the animal’s group-13). This indicated that widespread adoption of appropriate interventions including ensuring pen water is not shared between pens, optimising animal mixing before induction, timing of the animal’s move to the vicinity of the feedlot, and group size prior to placing animals in feedlot pens, and avoiding BVDV-1 in cohorts could markedly reduce the incidence of BRD in medium-sized to large Australian feedlots. [ABSTRACT FROM AUTHOR]

Most commercial software for implementation of structural equation models (SEM) cannot explicitly accommodate outcome variables of binomial nature. As a result, SEM modeling strategies of binomial outcomes are often based on normal approximations of empirical proportions. Inferential implications of these approximations are particularly relevant to health-related outcomes. The objective of this study was to assess the inferential implications of specifying a binomial variable as an empirical proportion (%) in predictor and outcome roles in a SEM. We addressed this objective first by a simulation study, and second by a proof-of-concept data application on beef feedlot morbidity to bovine respiratory disease (BRD). We simulated data on body weight at feedlot arrival (AW), morbidity count for BRD (Mb), and average daily gain (ADG). Alternative SEMs were fitted to the simulated data. Model 1 specified a directed acyclic causal diagram with morbidity fitted as a binomial outcome (Mb) and as a proportion (Mb_p) predictor. Model 2 specified a similar causal diagram with morbidity fitted as a proportion for both outcome and predictor roles within the network. Structural parameters for Model 1 were accurately estimated based on the nominal coverage probability of 95 % confidence intervals. In turn, there was poor coverage for most morbidity-related parameters under Model 2. Both SEM models showed adequate empirical power (>80 %) to detect parameters not equal to zero. Model 1 and Model 2 produced predictions that were reasonable from a management standpoint, as determined by calculating the root mean squared error (RMSE) through cross-validation. However, interpretability of parameter estimates in Model 2 was impaired due to the model misspecification relative to the data generation. The data application fitted SEM extensions, Model 1 * and Model 2 * , to a dataset from a group of feedlots in the Midwestern US. Models 1 * and 2 * included explanatory covariates, specifically percent shrink (PS), backgrounding type (BG), and season (SEA). Lastly, we tested if AW exerted both direct and BRD-mediated indirect effects on ADG using Model 2 *. In Model 1 * , mediation was not testable due to the incomplete path from morbidity as a binomial outcome through Mb_p as a predictor to ADG. Model 2 * supported a minor morbidity-mediated mechanism between AW and ADG, though parameter estimates were not directly interpretable. Our results indicate normal approximation to a binomial disease outcome in a SEM may be a viable option for inference on mediation hypotheses and for predictive purposes, despite limitations in interpretability due to inherent model misspecification. [ABSTRACT FROM AUTHOR]

• Implanted Santa Gertrudis steers had increased chute scores and rectal temperatures. • A high intensity implant protocol increased hip height in Angus steers. • Average daily gain increased by 29% with a high intensity implant protocol. • Average daily gain increased by 26% with a moderate intensity implant protocol. • A moderate intensity implant protocol improved economic return in both breed types. Recent research has suggested that different cattle breed types may respond differently to anabolic implant protocols of varying intensity. Therefore, the purpose of this research was to compare anabolic implant protocols in feedlot steers of 2 different breed types. Sixty steers were stratified by weight and breed in a 2 × 3 factorial design examining 2 different breeds: Angus (AN; n=38) or Santa Gertrudis influenced (SG; n=22), and 3 implant strategies: no implant (CON; n=20), a moderate intensity implant protocol (d0 implant: Revalor-G, d56 implant: Revalor-IS, d112 implant: Revalor-S; MI; n=20), or a high intensity implant protocol (d0 implant: Revalor-IS, d56 implant: Revalor-S, d112 implant: Revalor-200; HI; n=20). Steers were randomly placed into pens equipped with GrowSafe bunks to collect dry matter intake and feeding behavior. All animals were fed the same diet. Weight, chute score, exit velocity, serum, rectal temperature, hip height and 12th rib fat thickness were collected approximately every 28 d over a 196 d period. Serum urea nitrogen (SUN) was evaluated as well. Total average daily gain was increased (P < 0.0001) in both the HI and MI steers compared to the CON steers by 29.4% and 26%, respectively. A treatment × breed interaction was observed (P < 0.0001) for hip height, with AN-CON steers being shorter (P < 0.0007) than AN-HI, SG-CON, SG-MI, and SG-HI steers. A breed × treatment interaction was observed (P < 0.004) for chute score and rectal temperature, with SG-HI and SG-MI steers having increased chute scores (P < 0.001) when compared to AN-HI, AN-MI, AN-CON, and SG-CON throughout the course of the trial. Additionally, SG-HI and SG-MI steers had an increased rectal temperature (P < 0.004) compared to AN-HI, AN-MI, AN-CON, and SG-CON steers. A breed effect was observed (P = 0.002) for SUN with AN steers having increased (P = 0.002) SUN concentration compared to SG sired steers, in addition to a treatment effect (P < 0.0001), with CON steers having a higher (P < 0.0001) SUN concentration than MI and HI steers, regardless of breed. The MI implant protocol increased net return per head, on average, by $97.28, regardless of breed, while the HI implant protocol increased net return by only $80.84. Taken together, despite the cattle breed types responding differently to the different anabolic implant protocols at times, a moderate intensity anabolic implant protocol was optimal in this experiment for steers raised in a temperate climate. [ABSTRACT FROM AUTHOR]

• The use of antibiotics for bovine respiratory disease is questioned among consumers. • Dietary microbials may be an alternative to antibiotic use in high-risk cattle. • Dietary microbials seem beneficial for health and growth performance in cattle. • Many factors affect the health and performance of cattle entering the feedlot. • Further research is needed to assess responses of cattle to DFM. The objective of this study was to evaluate the effects of a supplemental probiotic-prebiotic blend (P-PB) on newly received beef cattle during the first 21 and 42 d after feedlot arrival. Crossbred steers (n=258; BW = 250 ± 11.4 kg) were received at the Texas A&M AgriLife Research Feedlot in Bushland, TX. Steers (n=240) were stratified by average initial BW (d -1, d -0) and allocated to 1 of 2 weight blocks and 1 of 3 dietary treatments. The control treatment (CON) received a pellet without P-PB. Treatment 2 received a pellet with P-PB from d 0 to 21 and then the CON pellet from d 22 to 42 (P-PB21). Treatment 3 received the P-PB pellet from d 0 to 42 (P-PB42). Following the 42-d receiving period, treatment pellets were removed and replaced with steam flaked corn for the remainder of the finishing period. If DMI was < 6.35 kg/steer daily, the P-PB pellet was included at 8.75% of the diet. If DMI was ≥ 6.35 kg/steer daily, the P-PB pellet was included at 6.25% of the diet. Body weight was measured on d 21 and d 42 of the feeding period. Statistical analysis for the randomized complete block design was analyzed using SAS 9.4. Pen was the experimental unit with 10 per treatment. There were no treatment effects between d 0 to 42 for body weight (BW), average daily gain (ADG), gain to feed (G:F), and dry matter intake (DMI) (P ≤ 0.99). No differences were observed for percent morbidity or mortality (P ≤ 0.65) from d 0 to 42. P-PB did not impact LM area, rib fat, marbling score, USDA QG or YG (P ≤ 0.99), while CON had a greater DP (P ≤ 0.05) and tended to have a greater hot carcass weight (P = 0.09). While results remained similar between treatments, there were no negative effects on cattle health and performance during the first 42 days after receiving. [ABSTRACT FROM AUTHOR]

The objective of this study was to use meta-analytical methods to evaluate the effects of nutritional strategies on the reduction of enteric methane emission in feedlot sheep. Additionally, this study aimed to evaluate interrelationships among diet composition, intake and digestibility of nutrients, rumen parameters, rumen microbial population, nitrogen metabolism and enteric methane production in sheep. The dataset was composed by 45 peer-reviewed publications with 102 treatment means. The strategies to mitigate enteric methane emission were evaluated by examining the weighted mean difference between control treatment (diets containing no additives and/or any other strategies to mitigate methane emission) and reduced-methane treatment (diets containing strategies to mitigate methane emission: protozoa-free, nitrate, lipids, saponins, essential oils and tannins). The interaction of factors associated with diet composition, nutrient intake and digestibility, rumen parameters on methane emission from sheep depends on how methane production is expressed (Production=CH 4 g/d vs Yield= CH 4 g/kg DMI). Lipids inclusion to diets reduced methane production in 6.28 g/d and 5.87 g CH 4 /kg of DMI. Oil inclusion in amounts greater than 20 g oil/day reduced methane production (CH 4 g/d). Lipid inclusion to diets presented the greatest effectiveness in reducing methane emission in sheep fed TMR diets containing different forage: concentrate ratios. Tannins inclusion to diets reduced methane production in 1.22 g/d CH 4 and 2.61 gCH 4 /kg of DMI, presenting long-term effect on methane emission. Tannins effects on methane production were greater in sheep fed high-forage total mixed rations. Rumen defaunation (protozoa-free) and essential oils inclusion to diets had no effects on methane production. Although methane production reduced with saponin and nitrate inclusion to diets, further studies are needed to confirm their effects on methane emission and better elucidate factors interacting with the response of sheep to saponins and nitrate supplementation. • Methane production (CH4 g/d) vs Yield (CH4 g/kg DMI) influences the interaction between diet composition, nutrient intake and digestibility, rumen parameters. • Lipids are more effective in reducing methane emission in sheep feedlot. • Tannins have a long-term effect on reducing methane production. [ABSTRACT FROM AUTHOR]

The eddy covariance (EC) technique has been extensively used in several sites around the world to measure energy fluxes and CO 2 exchange at the ecosystem scale. Recent advances in optical sensors have allowed the use of the EC approach to measure other trace gases (e.g. CH 4 , NH 3 and N 2 O), which has expanded the use of eddy covariance for other applications, including measuring gas emissions from livestock production systems. The main objectives of this study were to assess the performance of a closed-path EC system for measuring CH 4 , CO 2 , and H 2 O fluxes in a beef cattle feedlot and to investigate the spatial variability of eddy covariance fluxes measured above the surface of a feedlot using an analytical flux footprint analysis. A closed-path EC system was used to measure CH 4 , CO 2 , and H 2 O fluxes. To evaluate the performance of this closed-path system, an open-path EC system was also deployed on the flux tower to measure CO 2 and H 2 O exchange. The performance assessment of the closed-path EC system showed that this system was suitable for EC measurements. The frequency attenuations, observed for the closed-path system CO 2 and CH 4 cospectra in this study, are in agreement with results from previous instrument comparison studies. For the water vapor closed-path cospectra, larger attenuations were likely caused by water vapor molecule interaction with the sampling tube walls. Values of R 2 for the relationship between H 2 O and CO 2 fluxes, measured by open-path and closed-path systems, were 0.94–0.98, respectively. The closed-path EC system overestimated the CO 2 by approximately 5% and underestimated the latent heat fluxes by about 10% when compared with the open-path system measurements. Measured CH 4 and CO 2 fluxes during the study period from the feedlot averaged 2.63 μmol m −2 s −1 and 103.8 μmol m −2 s −1 , respectively. Flux values were quite variable during the field experiment and the footprint analysis was useful to interpret flux temporal and spatial variation. This study shows indication that consideration of atmospheric stability condition, wind direction and animal movement are important to improve estimates of CH 4 emissions per pen surface or per head of cattle. [ABSTRACT FROM AUTHOR]

Heat stress in feedlot cattle is known to reduce their performance. The challenge comes in determining reliable predictors of current and near-future changes in thermal status and performance. A 42-d study, using crossbred ( Bos taurus ) steers was conducted during summer months (July through August) to identify best environmental determinants of rumen temperature (T rumen ) and feed intake (FI) in feedlot cattle with access to shade. A further goal was to define the relationship between T rumen and FI. Shade coverage was approximately 50%, and all animals were provided standard feedlot diets and water ad libitum. Intraruminal telemetric boluses recorded T rumen several times each hour. Ear tags, telemetrically connected to a feed monitoring system, provided FI data using RFID technology. Data loggers recorded ambient conditions in sun and shade, along with black globe temperature. Regression analyses identified daylight black globe and air temperatures in shade, with one hour delays, as the best predictors of T rumen . Prediction of FI was much less reliable. Unexpectedly, T rumen was not superior to ambient variables in predicting FI. Maximum daily temperature humidity index, calculated using BG in sun with a 5-d lag, was the best significant predictor of FI. These results indicate for feedlot cattle that although air temperature alone in the shade may be the best predictor of T rumen in the heat, black globe temperature in the sun may be a better determinant of feed intake over time. Additional studies are needed to verify the delayed FI response which seems unusually long. [ABSTRACT FROM AUTHOR]

This study examined the effects of floor space and feeder space on the feeding behaviour, growth and stress physiology of lambs, at different times, over a 6-week period in a finishing feedlot. A total of 640 lambs in four time replicates (160 lambs per replicate) were studied in four 40-lamb intensive finishing systems (feedlots) for 6 weeks over a 16-month period. The lambs were Merino wethers with live weight at the commencement of the experiment of 28.3 (s.d. = 2.4) kg. The effects of two factors, pen floor space (2 and 5 m 2 /lamb) and feed trough space (4 and 10 cm/lamb) were examined in a factorial arrangement. Measurements taken on individual lambs during the experimental period included: feeding behaviour and displacements at the feeder in the feedlot during weeks 1, 2 and 6, lying behaviour during week 3, weekly live weights and cortisol concentrations in weeks 1 and 6. Weekly feed intake for each group of lambs was also record. Trough space of 4 cm compared to 10 cm per lamb reduced average lamb feed intake in all weeks of the 6-week period (a reduction of 1.2 (s.e. = 0.53) kg/hd in week 1, 1.3 (s.e. = 0.62) kg/hd in week 2, weekly average of 0.9 (s.e. = 0.17) kg/hd over weeks 3–6; P = 0.05, P = 0.06 and P = 0.0004, respectively). However, weight gain only differed significantly during the first week in the feedlot (average of 0.2 vs 1.1 (s.e.d. = 0.35) kg for 4 cm vs 10 cm/lamb of provided trough space, P = 0.03). At all observed times within the 6-week period, lambs with the reduced feed trough space spent less total time feeding (P < 0.05) with less feeding bouts (P < 0.05). There was no effect of feed trough space on lying time or cortisol concentrations. Floor space did not affect feeding and lying behaviour, feed intake, weight gain or cortisol concentrations. In conclusion, increasing feed trough space from 4 to 10 cm/lamb increased feed intake and live weight gain through an increase in the number of feeding bouts and the total time feeding. This indicates that the trough space recommendations in the Australian Model Code of Practice (sheep) of 2 cm/lamb are too low for maximum lamb feed intake and live weight. No effects of increasing floor space from 2 to 5 m 2 /lamb were found, however the growth rates in general were low suggesting that the environment in the feedlot may have been sub-optimal. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of the Dorper breed on the growth performance, feed efficiency, carcass and meat traits when crossbred with Santa Inês sheep raised under an intensive production system in the northeastern region of Brazil. Twenty-four lambs were used in this trial under a fully randomized design. The lambs were housed and creep fed until weaning at 62 days of age. After weaning, they were sent to a feedlot for finishing with a high-energy diet until slaughter, which occurred when the lambs attained a 3 mm thickness of subcutaneous fat. The Dorper crossbred lambs exhibited a higher daily gain (223.8 g/day) than the Santa Inês pure lambs (168.1 g/day) and attained the slaughter fat thickness (132 days) more quickly. Significant differences were observed between the crosses and the Santa Inês lambs in terms of the carcass weight, rib eye area, carcass and leg compactness indexes, weight and dressing of commercial cuts and the muscle:bone ratio. According to the results obtained under the described experimental conditions, at the same maturity level, the growth performance, the age at slaughter and the main carcass characteristics were conclusively improved by crossbreeding of the Santa Inês ewes with the Dorper rams, making the use of local sheep breeds possible, to efficiently meet the needs of the domestic market. [ABSTRACT FROM AUTHOR]

Two studies were conducted to determine the effects of floor or bedding type on lamb performance, carcass characteristics, and visceral organ mass. In Exp. 1, seventy-two early weaned Targhee × Hampshire ram lambs (initial BW = 35.2 kg) were used in a randomized complete block design experiment to determine the effects of floor type and bedding with lambs fed an 80% concentrate diet. The types of flooring investigated were expanded metal, dirt with a sand top-dress, and dirt with straw bedding. Flooring type affected DMI (P < 0.001), with lambs on expanded metal consuming the least (1.23 kg/day), lambs on straw consuming the most (1.28 kg/day), and lambs on sand being intermediate (1.25 kg/day). The differences in DMI resulted in lambs on expanded metal having a lower (P < 0.05) ADG than lambs on straw (0.26 vs. 0.28 kg/day, respectively). Lambs bedded with straw had greater (P < 0.05) total digestive tract mass compared to lambs on expanded metal flooring. No significant differences were found for lamb carcass characteristics due to flooring type. In Exp. 2, ninety-two Dorset × Hampshire lambs (initial BW = 31 kg) were used in a randomized complete block design experiment to determine the effects of bedding, dirt with a sand top-dress, and dirt with straw bedding, on animal performance with alfalfa silage and corn-based growing and finishing diets, respectively. Lambs were allotted to pens based on sex (wethers = 46 and ewes = 46) and initial BW (small or large), with 11 or 12 lambs per pen. Lambs bedded with straw had significantly greater (P < 0.05) ADG, DMI, and G:F compared with lambs bedded with sand during the growing period. However, lambs bedded with sand had significantly greater G:F (P < 0.05) compared to lambs bedded with straw during the finishing period. [ABSTRACT FROM AUTHOR]

Feedlots concentrate large volumes of manure and effluents that contain high concentrations of nitrate, among other constituents. If not managed properly, pen surfaces run-off and lagoons overflows may spread those effluents to surrounding land, infiltrating into the soil. Soil nitrate mobilization and distribution are of great concern due to its potential migration towards groundwater resources. This work aimed at evaluating the migration of nitrate originated on feedlots effluents in a fine-textured soil under field conditions. Soil water constituents were measured during a three-year period at three distinct locations adjacent to feedlot retention lagoons representing different degrees of exposure to water flow and manure accumulation. A simple statistical analysis was undertaken to identify patterns of observed nitrate and chloride concentrations and electrical conductivity and their differences with depth. HYDRUS-1D was used to simulate water flow and solute transport of Cl − , NO 4 + N, NO 3 − N and electrical conductivity to complement field data interpretation. Results indicated that patterns of NO 3 − N concentrations were not only notoriously different from electrical conductivity and Cl − but also ranges and distribution with depth differed among locations. A combination of dilution, transport, reactions such as nitrification/denitrification and vegetation water and solute uptake took place at each plots denoting the complexity of soil-solution behavior under extreme polluting conditions. Simulations using the concept of single porosity-mobile/immobile water (SP-MIM) managed structural controls and correctly simulated — all species concentrations under field data constrains. The opposite was true for the other two locations experiencing near-saturation conditions, absence of vegetation and frequent manure accumulation and runoff from feedlot lagoons. Although the results are site specific, findings are relevant to advance the understanding of NO 3 − N dynamics resulting from FL operations under heavy soils. [ABSTRACT FROM AUTHOR]

The production of lamb meat is a large and important industry in Australia. Variability and seasonality of the climate and the demand for a consistent product (in terms of weight and age) have led to an increase in the use of feedlot systems for finishing lambs. While most lambs acclimatise to this environment, an estimated 5–20% may suffer from inanition or shy feeding, but there is little direct information available on associated physiological stress. This exploratory study examined relationships between temperament, feeding behaviour, social interactions and cortisol concentrations in lambs in the first 2 weeks in an intensive finishing system (feedlot). Lambs in two 20-lamb feedlots (with 2 m 2 floor space/animal) were studied. Prior to entry to the feedlot, the lambs were subjected to a temperament test (Isolation Box Test) in which activity was measured. Weight gain, general activity, lying time, time at the feeder, number of feeding bouts, displacement at the feeder and plasma cortisol concentrations in weeks 1 and 2 in the feedlot were recorded. A parsimonious general linear model was developed to relate the logarithm of cortisol concentration in weeks 1 and 2 to all other measurements. In week 1 cortisol was most elevated if the lamb’s activity in the feedlot (number of steps) was low (P = 0.000025) and also for those lambs that fed more frequently (P = 0.0010). Higher levels of activity in the temperament test were associated with higher cortisol concentrations in week 1 when the lamb was not displaced from the feeder. However there was an interaction with the number of displacements (P = 0.0016), leading to little effect when a displacement occurred. In week 2 higher cortisol concentrations were associated with higher growth (P = 0.040) which may be a reflection of the positive association between cortisol and feeding bouts in week 1. This study demonstrates relationships between cortisol concentrations, activity in the temperament test, feeding bouts, displacements at the feeder and activity in the first week and growth in the second week in the feedlot. A better understanding of these behaviour and stress relationships early in the feedlot may be useful in identifying strategies to protect vulnerable animals in feedlots. [ABSTRACT FROM AUTHOR]

Two trials were conducted to evaluate the effects of silage crop and levels of dietary crude protein (CP) in Nellore beef cattle. The experimental diets consisted of Stylosanthes (StS) or corn silage (CS) with two levels of dietary CP, 110 and 130 g CP/kg diet on a dry matter (DM) basis. The forage to concentrate ratio was 50:50 on a DM basis. In Experiment 1, the four bulls that were used had an average initial body weight (BW) of 450 ± 37.9 kg, and were surgically cannulated in the rumen and abomasum. The bulls were assigned to a 4 × 4 Latin square with a 2 × 2 factorial design of treatments, and four 16-d periods. During this experiment, we collected ruminal fluid, abomasal digesta, feces, urine, and blood. In addition, the kinetic parameters of DM, CP, and neutral detergent fiber (NDF) degradation were estimated. In Experiment 2, 40 bulls with an average initial BW of 374 ± 16.5 kg were distributed into a 2 × 2 factorial in a randomized design with ten replicates. The trial lasted for 99 d and was divided into a 15-d period for adaptation and an 84-d period for data collection. The intake and digestibility of nutrients as well as animal performance were evaluated in Experiment 2. The potentially degradable fractions of DM, CP, and NDF of StS were lower than CS (P < 0.004). The diets containing StS showed lower ruminal digestibility of organic matter (OM) and lower total tract digestibility of OM, CP, and NDF than diets containing CS (P < 0.050). The StS-based diets showed higher values for ruminal pH in comparison with CS-based diets (P = 0.010). The ruminal NH 3 –N concentration was higher for the level of 130 g CP/kg diet in comparison with the 110 g CP/kg diet (P < 0.001). The dietary CP level affected urea nitrogen in blood (P < 0.001) and urine (P = 0.017), which were higher in the diets containing StS and CS at the level of 130 g CP/kg diet. The diets containing StS showed a higher intake of DM, OM, CP, NDF, and indigestible neutral detergent fiber (iNDF) than diets containing CS (P < 0.008). However, the amount of digested nutrients (kg/d) was similar between treatments (P > 0.050). The silage crop and dietary CP levels had no effect on productive performance (P > 0.050), but the StS-based diet tended to decrease feed efficiency (P = 0.085). Thus, StS, as well as the level of 110 g CP/kg diet, can be used to feed finishing beef cattle. [ABSTRACT FROM AUTHOR]