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Forty-eight Pelibuey × Katahdin male intact lambs (25.12 ± 3.79 kg LW) were used in a 70-d growing-finishing trial. Dietary treatments consisted of total mixed corn-based diet supplemented with: (1) no feed additives (Control); (2) 150 mg of essential oils blend plus 0.10 mg of 25-hydroxy-Vit-D3/kg diet offered throughout the 70-d experimental period (EOD3); (3) Control diet fed during the first 35 days and zilpaterol hydrochloride (ZH) supplementation at 6 mg/kg diet offered during the final 35 days of the experiment (32 days with ZH with a withdrawal 3-d before harvest), and (4) basal diet supplemented with EOD3 during first 35 days finishing, and EOD3 in combination with ZH (EOD3 + ZH) during the subsequent 32-days with ZH withdrawal 3 days before harvest. The temperature-humidity index during the experiment averaged 80.4 ± 3.2. There were no treatment interactions ( p > 0.20) on growth performance and carcass measures. Supplemental EOD3 did not affect ( p = 0.43) dry matter intake (DMI), but increased ( p < 0.01) carcass adjusted average daily gain (ADG, 9.2%), gain efficiency (GF, 6.7%), and observed vs. expected dietary net energy for maintenance (NE m , 4.8%) and for gain (NE g , 6.4%). Supplemental ZH did not affect dry matter intake (DMI, p = 0.50) but increased ( p < 0.01) carcass adjusted ADG (14.5%), GF (13%) and observed vs. expected dietary NE m (9%) and NE g (11.7%). Compared to control lambs, the combination of both additives increased ADG (24.9%), GF (21.2%), and observed vs. expected dietary NE m and NE g (14.2% and 18.9%, respectively). There were no treatment interactions on carcass characteristics, visceral organ mass, or on gene expression of IGF1, IGF2 and mTOR in longissimus muscle (LM). Supplemental EOD3 increased hot carcass weight (HCW; 4.0%, p < 0.01) but did not affect other carcass measures. Supplemental EOD3 decreased (3%, p = 0.03) intestine mass weight (g intestine/kg empty body weight). Supplemental ZH increased HCW (6%, p < 0.01), dressing percentage (1.7%, p = 0.04), and LM area (9.7%, p < 0.01), and decreased kidney-pelvic-fat percentage (16.2%, p < 0.01), fat thickness (14.7%, p = 0.03), and visceral fat. Compared to controls, the combination of EOD3 with ZH increased HCW (10.2%). It is concluded that growth performance responses to supplemental EOD3 and ZH are additive. Both supplements can be fed in combination without detrimental effects on expected benefits when fed separately. In addition, ZH supplementation improves carcass traits.

The objective was to examine the effects of metabolizable protein (MP) and ruminal-protected methionine supplementation on growth performance of Holstein steer calves during the initial feedlot growing phase (112 d). One hundred eighty Holstein steer calves (122 ± 7 kg) were blocked by weight and assigned to 30 pens (6 steers per pen). Five treatments were applied: 1) control, a diet based on steam-flaked corn containing urea and dry distillers grains plus solubles as supplemental N sources with no amino acid addition; 2) control diet plus blood meal supplementation; 3) diet from treatment 2, with 0.064% Smartamine M (70% methionine; Adisseo, Alpharetta, GA) supplementation; 4) diet from treatment 2 with 0.096% Smartamine M supplementation; 5) diet from treatment 2 with 0.128% Smartamine M supplementation. All diets were formulated to exceed the estimated MP requirements. The estimated metabolizable lysine, as well as methionine, was deficient in the control diet. Blood meal was added to the control diet to meet estimated lysine requirements (diet 2), the other diets had increasing concentrations of supplemental methionine. Supplemental MP enhanced (10%, P  < 0.02) interim and overall 112-d average daily gain (ADG). Additional effects of supplemental methionine on ADG were not appreciable ( P  > 0.10). Supplemental MP did not affect ( P  > 0.10) dry matter intake (DMI) during the first 56-d period; however, it tended to increase ( P  = 0.08) DMI during the subsequent 56-d period. Overall, supplemental MP or methionine had no appreciable effect (P > 0.10) on DMI. Supplemental MP improved ( P  < 0.01) gain efficiency and estimated dietary net energy (NE) values during the initial 56-d period (11 and 7%, respectively) and overall (7 and 4%, respectively). Supplemental MP did not affect ( P  > 0.10) gain efficiency during the second 56-d period, although it tended to enhance ( P  = 0.08) estimated dietary NE. Supplemental methionine did not appreciably affect ( P  > 0.10) gain efficiency or estimated dietary NE. Therefore, adding MP to cover the estimated limiting amino acid supply in diets may enhance the gain efficiency and dietary energetics of growing Holstein calves. However, amino acid addition supplementation beyond the requirements may not produce extra productive performance of steer calves., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The objective of the current study was to evaluate the effects of tannin and monensin supplementation in feedlot diets and breed (Holstein vs. Angus × Holstein) on growth performance, energetic efficiency, and carcass characteristics. Eighty purebred Holstein calves (HOL; initial body weight (BW) = 130 ± 5 kg) and 80 Angus × Holstein calves (AXH; initial BW = 129 ± 6 kg) were blocked by initial BW and randomly assigned to 40 pens. Dietary treatments consisted of a steam-flaked corn-based diet supplemented with (1) no feed additive (CON); (2) 30 mg of monensin/kg of dry matter (DM; MON; Rumensin 90, Elanco, Greenfield, IN); (3) 1.5 g tannin)/kg of DM (TAN; ByPro, 70% condensed tannin, SilvaFeed, Indunor, S.A., Buenos Aires, Argentina); (4) M + T, the combination of MON plus TAN dietary treatments. Data were analyzed as a randomized complete block in a 2 × 4 factorial arrangement of treatments, using pens as experimental units. There were no interactions (P > 0.05) between feed additives and breed. Supplemental MON increased (P ≤ 0.04) initial 112-d BW and gain efficiency. However, there were no dietary treatment effects (P > 0.10) on overall growth performance. Monensin supplementation decreased (P = 0.04) minimum daily ruminal temperature compared with other dietary treatments during July, but TAN did not affect ruminal temperature. Holstein steers had greater (P = 0.04) overall DM intake compared with AXH, with no difference (P = 0.19) in overall ADG, leading to increased (P < 0.01) gain efficiency for AXH compared with HOL. Dietary net energy for maintenance and gain, based on growth performance, were greater (P ≤ 0.01) for AXH vs HOL. Compared with HOL, AXH steers had greater (P ≤ 0.01) carcass weight, dressing percentage, kidney, pelvic, and heart fat, 12th rib fat thickness, longissimus area, and preliminary yield grade. Holstein steers had lower (P ≤ 0.04) minimum average ruminal temperature during June compared with AXH, with no differences (P ≥ 0.14) between breeds during July or August. Results indicate that feed additives did not appreciably affect steer growth performance and carcass characteristics, but crossbred AXH steers had greater growth performance, efficiency of dietary energy utilization, and carcass quality measures compared with HOL. This study observed a reduction (4.7%) in maintenance energy expenditure in AXH compared with HOL, implying in maintenance energy coefficient of 0.086 vs 0.082 for HOL and AXH, respectively., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

With the aim of evaluating the effect of combining an antibiotic ionophore with plant extracts and probiotics on the productive efficiency (performance and carcass) during the last phase of lamb fattening, 24 Pelibuey × Katahdin male lambs (38.47 ± 3.92 kg, initial weight) were fed with a high-energy diet during for 56 days, and assigned, under a complete randomized block design experiment to one of the following supplement treatments: (1) 28 mg of monensin/kg diet DM supplemented alone (MON), (2) combination of MON plus 2 g/kg diet of a product contained Bacillus subtilis 2.2 × 10 8 CFU kg diet DM (MON + BS), (3) combination of MON + BS plus 300 mg essential oils/kg diet DM (MON + BS + EO), and (4) BS alone. At the end of the feeding trial (56-d), lambs were slaughtered and carcass variables were measured. Compared to the rest of the treatments, combining MON with BS improved dietary NE by 3.4% and the efficiency of utilization of dietary energy consumed. Inclusion of EO in the MON + BS combination resulted in a similar average daily weight gain (ADG) and feed efficiency (GF) when compared with MON + BS, but showed a lower dietary net energy (NE), hot carcass weight, and dressing percentage. Lambs receiving BS alone showed greater average ADG and dry matter intake (DMI) than lambs receiving MON + BS + EO, but similar feed GF and dietary NE. There were no treatment effects on tissue composition, whole cut, or visceral organ mass. It was concluded that combining probiotics with the ionophore monensin can improve the efficiency of dietary energy utilization in the last phase of finishing. Probiotics supplemented alone result in greater ADG without a difference in dietary energy efficiency when compared with MON alone. Inclusion of EO in the MON + BS combination did not show advantages; on the contrary, it reduced carcass weight and dressing percentage. It is necessary to further research the potential complementary effects of combining diverse sources of natural additives with synthetic antibiotics.

Supplementation with natural additives such as essential oils (EO) or probiotics has resulted in comparable growth performance to that of supplemental monensin in fattening lambs in hot environments. Supra-supplementation levels of vitamin D3 improved the carcass weight and dressing percentage of steers fattened under tropical conditions. We hypothesized that certain combinations of these natural additives could be complementary. For this reason, a feeding trial was carried out using 48 Pelibuey × Katahdin non-castrated male lambs (107 ± 14 d age; 17.9 ± 2.51 kg LW). Lambs were fed an 88:12 concentrate to forage ratio basal diet supplemented (dry matter basis, DMI) with: (1) no additive (CON); (2) 28 mg monensin/kg diet (MON); (3) 150 mg of essential oils containing a combination of thymol, eugenol, vanillin, guaiac, and limonene plus 0.12 mg vitamin D3 (EO + D3)/kg diet; and (4) 300 mg of essential oils containing a combination of carvacrol and cynamaldehyde plus 2 g probiotic (2.2 × 10 8 CFU of bacillus subtilis/kg diet, EO + BS). Lambs were grouped by initial weight and assigned within six weight groupings to 24 pens (2 lambs/pen, 6 replicas per treatment) in a randomized complete block design. The experiment lasted 121 days. Daily maximal THI exceeded the 80 "danger or "emergency" range for 119 days of the 121 days of the trial. Lambs supplemented with MON had similar DMI, growth performance, and dietary energetics to those of CON lambs. Lambs supplemented with EO + BS had a greater (9.2%, p ≤ 0.05) average daily gain (ADG) than the CON and MON groups due to enhanced (10.2%, p ≤ 0.05) dry matter intake. Thus, gain efficiency (GF) and estimated dietary energy were similar for CON, MON, and EO + BS. Lambs receiving EO + D3 had similar (0.254 vs. 0.262 kg/d) ADG but a lower DMI (8%, p < 0.05) compared with EO + BS lambs. Consequently, GF and estimated dietary net energy were greater (4.9 and 3.7%, respectively; p ≤ 0.05) for EO + D3 lambs. Even when ambient heat load was elevated, the efficiency of utilization of dietary energy (observed-to-expected dietary net energy) was close to 1.00 (0.992) expected for EO + D3 lambs. In contrast, efficiency of energy utilization was depressed by -4.4% for lambs on the other treatments. Compared with the other treatments, lambs receiving EO + D3 had greater longissimus muscle area (5.6%, p < 0.05) and lower kidney pelvic fat (21.8%, p ≤ 0.05). There were no treatment effects on shoulder tissue composition or whole cuts (expressed as % of cold carcass weight). Compared to CON, lambs that were fed with natural additives showed 3.5% lower ( p ≤ 0.05) intestine mass. All supplemental additives decreased visceral fat mass, which was minimal with EO + D3 treatment. Combinations of essential oils with vitamins or probiotics were superior to antibiotic monensin in finishing diets for feedlot lambs. Combining EO with probiotics promoted DM intake and gain but not gain efficiency, while combining EO with vitamin D3 supra-supplementation increased dietary energy efficiency and improved some carcass characteristics in lambs fattening under high ambient heat loads.

This study evaluates the partial replacement of steam-flaked corn (SFC) with increasing dried distillers grains plus solubles (DDGS) levels in growing-finishing diets for calf-fed Holstein steers. Two experiments were conducted. In trial 1, 100 Holstein calves (136 ± 7 kg) were used to evaluate the effect of DDGS as a metabolizable protein source on cattle growth performance, and dietary energetics of calf-fed Holstein steers during the initial 111 d growing phase. Four dietary levels of DDGS were evaluated (10, 15, 20, and 25%, dry matter basis), replacing SFC (flake density, 0.31 kg/L). In trial 2, four Holstein steers (368 ± 20 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of ruminal and total tract digestion of organic matter (OM), neutral detergent fiber, nitrogen (N), and indispensable amino acid supply to the small intestine. The increasing level of DDGS did not affect ( P ≥ 0.13) average daily gain, gain efficiency, and estimated dietary net energy values. Replacement of SFC with increasing levels of DDGS decreased (linear; P = 0.01) ruminal OM digestion. There was no treatment effect on the flow of microbial nitrogen to the small intestine ( P = 0.34) and ruminal microbial efficiency ( P = 0.79). However, increasing levels of DDGS in the diet increased (linear; P ≤ 0.04) flow of methionine, histidine, phenylalanine, threonine, leucine, isoleucine, and valine but did not affect ( P = 0.74) intestinal supply of lysine. Increasing DDGS in the diet increased (linear, P < 0.01) flow of N to the small intestine but decreased (linear; P < 0.01) ruminal N efficiency. Replacing SFC with DDGS increased intake and amino acid leaving the abomasum. Still, this effect was not sufficient to increase the growth performance of calf-fed Holstein during the first 111 d on feed., (Published by Oxford University Press for the American Society of Animal Science 2023.)

Evaluation of the effects of feeding NutraGen supplement (NutraGen, NTG; Phibro Animal Health, Teaneck, NJ, USA) on growth performance, energetic efficiency, carcass characteristcs, and characteristics of digestion in calf-fed Holstein steers fed a conventional growing-finishing diet. Trial 1 evaluated growth performance, dietary energetics and carcass characteristics. Two hundred Holstein steer calves (134 ± 5 kg) were blocked by initial body weight (BW) and randomly assigned to 40 pens (5 steers/pen). Dietary treatments consisted of a steam-flaked corn-based growing-finishing diet supplemented with 0, 0.2, 0.4, or 0.6% NTG (DM basis). In trial 2, four Holstein steers (170 ±6 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square experiment to evaluate digestibility and ruminal characteristics using the treatments from trial 1. Compared to non-supplemented cattle, NTG increased BW (2.0%, P = 0.02) and tended to increase ADG (3.6%, P = 0.07) during the initial 56 d period. However, there were no treatment effects on overall growth performance and efficiency of dietary energy utilization after the first 56 days ( P > 0.10). Supplementation of NTG increased (linear effect; P ≤ 0.03) longissimus muscle area and kidney, pelvic, and heart fat. There was no effect ( P ≥ 0.05) of NTG supplementation on other carcass characteristics, liver abscess incidence, or liver abscess scars. Supplementation decreased the molar proportion of ruminal propionate ( P = 0.05) and tended to increase acetate:propionate molar ratio ( P = 0.09). However, there was no effect of NTG supplementation on ruminal and total tract diet digestion. NTG increased performance of Holstein steers during the first 56 d on feed in the feedlot. In addition, the steers had an increase in KPH fat and LM area, indicating that the additive induced change in metabolism of the steers., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Carvalho, Latack, Ferraz Junior, Flores, Sanchez-Cruz, Montaño and Zinn.)

The objective of this study was to evaluate the influence of supplemental flavomycin on cattle growth performance, carcass characteristics, diet digestibility, and ruminal fermentation characteristics of calf-fed Holstein steers. One hundred Holstein steers (123 ± 7 kg) were balanced by weight and assigned to 20 pens. Dietary treatments consisted of a steam flaked corn-based diet supplemented with (dry matter basis): 1) control, no feed additive; 2) 6.6 mg/kg flavomycin; 3) 13.2 mg/kg flavomycin, and 4) 30 mg/kg monensin (MON). There were no treatment effects ( P ≥ 0.17) on live weight, average daily gain (ADG), and gain efficiency. Flavomycin did not affect dry matter intake (DMI; P ≥ 0.24). Flavomycin supplementation did not affect ( P ≥ 0.37) the ratio of observed vs. expected DMI. However, MON decreased ( P = 0.02) observed vs. expected DMI by 3.7%. There were no treatment effects ( P ≥ 0.44) on ruminal pH or temperature. Flavomycin did not affect ( P ≥ 0.13) carcass characteristics and liver abscess among steers. Four Holstein steers (463 ± 20 kg) with ruminal cannulas were used in 4 × 4 Latin square experiment to study treatment effects on site and extent of digestion, ruminal pH, and volatile fatty acid (VFA) molar proportions. Dietary treatments were the same as experiment 1. Flavomycin tended to increase (linear effect, P = 0.07) ruminal organic matter (OM) digestion, associated with increased (linear effect, P < 0.01) ruminal starch digestion. Supplementing flavomycin at 13.2 mg/kg decreased net microbial N synthesis (quadratic effect, P = 0.03). Compared with control, MON tended to increase ( P = 0.10) ruminal neutral detergent fiber (NDF) digestion and increased ( P < 0.01) ruminal starch digestion. Monensin did not affect ( P = 0.39) net microbial N synthesis, but decreased ( P = 0.01) ruminal degradation of feed nitrogen (N). There were no treatment effects ( P > 0.10) on total tract apparent digestion of DM, OM, NDF, and starch. Flavomycin decreased ruminal pH (quadratic effect, P < 0.01) measured 4 h postprandial. Compared with control, MON increased ruminal pH ( P = 0.03). Flavomycin increased (linear effect, P = 0.03) ruminal propionate molar proportion and decreased (linear effect, P ≤ 0.04) ruminal molar proportions of acetate and butyrate, and decreased (linear effect, P = 0.02) acetate:propionate molar ratio and estimated methane production. We conclude that supplementing flavomycin at 6.6 or 13.2 mg/kg had no major effects on cattle growth performance, carcass characteristics, diet digestibility, and ruminal fermentation characteristics., (Published by Oxford University Press for the American Society of Animal Science 2023.)

Bans on the use of ionophores in several regions of the world has led to a need to identify alternative feed additivies to be added in cattle diets. Essential oil blends have been identified as a potential alternative to ionophores in feedlot diets. The objective of this study was to evaluate the effects of a supplemental a blend of essential oils and 25-hydroxyvitamin D3 on growth performance, energetic efficiency, and carcass characteristics in calf-fed Holstein steers. Ninety Holstein steer calves (123 ± 7 kg; 4 months old) were randomly assigned to 18 pens (5 steers/pen; 6 pens/treatment). Dietary treatments consisted of a steam-flaked corn-based diet supplemented with (DM basis): (1) no additives (CON); (2) 30 mg/kg DM of monensin (MON); (3) 200 mg/kg DM of a mixture of essential oils plus 25-hydroxyvitamin D3 (EO+HYD). There were no treatment effects ( P > 0.05) on initial, intermediate and final cattle live weight; moreover, cattle had similar ( P > 0.05) average daily gain (ADG) and dry matter intake (DMI) among dietary treatments. However, during the first 112 days of feed, calf-fed Holstein steers supplemented with EO+HYD had a greater ( P ≤ 0.05) gain to feed ratio (G/F) than cattle fed the control diet but similar ( P > 0.05) G/F to cattle supplemented with MON. However, there was no effect ( P > 0.05) of dietary treatments on 112 to 286 d and the overall G/F ratio of calf-fed Holstein steers. Calf-fed Holstein steers supplemented with EO+HYD had greater ( P ≤ 0.05) estimated net energy for maintenance (NEm) and net energy for gain (NEg) based on cattle growth performance than cattle fed the CON diet. Cattle supplemented with MON had an intermediate and similar ( P > 0.05) NEm and NEg compared to the other two dietary treatments. However, when observed vs. expected NEm and NEg were calculated, cattle supplemented with MON and EO+HYD had greater efficiency of dietary energy utilization than cattle fed the CON diet. Calf-fed Holstein steers supplemented with MON had greater ( P < 0.05) fat thickness than EO+HYD supplemented steers, and both were intermediate ( P ≥ 0.05) to that of cattle fed the CON diet. There were no other effects ( P > 0.05) on kidney, pelvic and heart fat, longissimus area, marbling score, and retail yield. The health status of cattle and liver abscesses or liver scars at slaughter were similar ( P > 0.05). We conclude that supplementing calf-fed Holstein steers with MON or EO+HYD for over 285 days increased dietary net energy utilization for maintenance and gain of the diet by 3 and 4%, respectively, compared to non-supplemented steers., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Latack, Carvalho and Zinn.)

Ninety crossbreed bulls (349.5 ± 8.25 kg initial weight) were used in an 87day trial to compare the effects of a blend of essential oils plus 25-hydroxy-Vit-D3 (EO + HyD) versus the combination of monensin with virginiamycin (MON + VM) on feedlot growth performance and carcass characteristics. Dietary treatments (nine replicates/treatment) were supplemented with 40 mg/kg diet dry matter of MON + VM (equal parts) or with 120.12 mg/kg diet dry matter of a combination of standardized mixture of essential oils (120 mg) plus 0.12 mg of 25-hydroxy-vitamin-D3 (EO + HyD). There were no treatment effects on dry matter intake (DMI, p = 0.63). However, the coefficient of variation in day-to-day DMI was greater for EO + HyD than for MON + VM (11.4% vs. 3.88%, p = 0.04). There were no treatment effects (p ≥ 0.17) on daily weight gain, gain-to-feed ratio, and estimated dietary net energy. Cattle supplemented with EO + HyD had greater Longissimus muscle area (7.9%, p < 0.01) and estimated retail yield (1.6%, p = 0.03), and tended to have heavier (1.7%, p = 0.10) carcass weight. Differences among treatments in dressing percentage, fat thickness, kidney−pelvic−heart fat, and marbling score were not appreciable (p > 0.10). It is concluded that growth performance response and dietary energetic are similar for finishing cattle supplemented with EO + HyD vs. MON + VM. However, compared with MON + VM, supplementation with EO + HyD during the finishing phase may improve carcass Longissimus area and carcass yield.

In calf-fed Holstein steers, the early growing phase is characterized by very high relative dry matter intake (DMI) accompanied with lower-than-expected efficiency of energy utilization. Although fat is commonly supplemented in growing-finishing diets, the comparative feeding value has not been investigated during the initial receiving-growing period. Eighty-four Holstein calves (127.7 ± 2.1 kg body weight) were used to evaluate the effects of including 3.5% of supplemental yellow grease (YG) in the diet on characteristics of growth performance and dietary energy utilization of calves during the early growth phase. Morbidity and mortality were not affected by dietary treatments. Yellow grease supplementation did not affect DMI, but tended to increase average daily gain (4.6%; P = 0.07), and increased ( P ≤ 0.03) gain efficiency (5.8%) and dietary net energy for maintenance (NE m ) and gain (NE g ) by 4.1% and 5.3%, respectively. Based on performance data, the estimated NE value of supplemental YG was 4.67 and 3.68 Mcal/kg for NE m and NE g , respectively. These values are consistent with current tabular values assigned for vegetable oils (4.75 and 3.51 Mcal/kg), but markedly less (16.6%) than NE m value assigned for YG (5.60 Mcal NEm/kg; NASEM, 2016. Nutrient requirements of beef cattle . 8th ed. Washington (DC): National Academy Press.)., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)

In experiment 1, 150 calf-fed Holstein steers (119 ± 6 kg) were used to evaluate the effects of level of supplemental condensed tannin (0, 14, and 28 g/kg diet DM) in a conventional steam-flaked corn-based growing-finishing diet on feedlot growth performance. There were no treatment effects on growth performance during the initial 56-d period. However, during the subsequent 56-d period, supplemental condensed tannin tended to increase average daily gain (ADG; linear effect, P = 0.09). The increase in ADG was consistent with the tendency for increased dry matter intake (DMI; linear effect, P = 0.08). Hence, differences in gain efficiency during the second 56-d period were not appreciably affected ( P = 0.80). Supplemental condensed tannin did not affect overall (112-d) ADG, DMI, gain efficiency, or dietary NE. In a second experiment, six Holstein steers (179.4 ± 7.9 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 × 3 Latin square design to evaluate treatment effects on characteristics of ruminal and total tract digestion. Treatments were the same as in Trial 1. Tannin supplementation decreased (linear effect, P = 0.03) ruminal OM digestion and tended to decrease (linear effect, P = 0.06) ruminal feed N degradation. Tannin supplementation decreased (linear effect, P = 0.03) ruminal pH, but did not affect ( P > 0.20) ruminal molar proportions of volatile fatty acids and estimated methane production. In current study, supplemental tannin had marginal effects on overall growth performance of calf-fed Holstein steers, but reduced ruminal, postruminal, and total tract nitrogen digestion., (Published by Oxford University Press on behalf of the American Society of Animal Science 2022.)

Objective: Evaluate the effect of arrival weight on feedlot growth performance and carcass characteristics of Holstein steers of similar age., Material and Methods: Three hundred calf-fed Holstein steers (age 113 ± 1-day) were distributed in a completely randomly unbalanced design and divided into five categories (105, 112, 117, 123, and 129 kg) of shrunk initial weight (SIW). Calves were weighed on days 1, 112, 224, and 361. Calves were fed steam-flaked corn-based diets. Growth performance and dietary energy were evaluated for each period and the study as a whole (1-361-day)., Results: During the rearing period, average daily gain (ADG) increased (linearly effect, p < 0.01) with increasing birth weight. Birthweight was positively associated ( p < 0.05) with feedlot arrival weight ( R 2 = 0.47) and final harvest weight ( R 2 = 0.36). Overall ADG increased ( p < 0.01) with increasing SIW. Dry matter intake increased linearly during the first 224-day but quadratically during the last 137 days. Overall, there was a quadratic effect ( p < 0.05) of SIW on gain-to-feed and observed-to-expected dietary NE, with lower efficiencies (4%) for steers in both the lightest and heaviest SIW. Hot carcass weight, Longissimus muscle area, marbling score, and fat thickness increased (linear effect, p ≤ 0.03) as SIW increased, whereas kidney-pelvic-heart fat and yield-grade were unaffected., Conclusions: The initial arrival weight influences the growth performance, energetic efficiency, and carcass characteristics of Holstein steers of similar age. The effect is more pronounced in the lighter (<112 kg) steers., Competing Interests: No potential conflict of interest was reported by the authors., (Copyright: © Journal of Advanced Veterinary and Animal Research.)

One hundred sixty-eight Holstein steer calves (133.4 ± 7.9 kg) were used to evaluate the influence of virginiamycin (VM) supplementation on cattle growth performance and liver abscess incidence, and the effect of feeding 100% vs. 87% of metabolizable protein (MP) requirements during the initial 112 d on growth performance, efficiency of energy utilization, and carcass characteristics. Steers were balanced by weight and assigned to 28 pens (6 steers/pen). During the initial 112-d feeding period, dietary treatments consisted of two levels of MP (100% vs. 87% of expected requirements) supplemented with or without 22.5 mg/kg VM in a 2 × 2 factorial arrangement. There were no VM × MP supplementation interactions ( P  ≥ 0.14) on any of the parameters measured in both experiments. Calf-fed Holstein steers supplemented with VM increased ( P  ≤ 0.03) overall average daily gain (ADG), feed efficiency (G:F), observed/expected net energy (NE) values for maintenance and gain, and final body weight (BW). Cattle fed VM also increased ( P  ≤ 0.04) carcass weight, dressing percent, and longissimus muscle area. However, there was no effect ( P  ≥ 0.22) of VM supplementation on any other carcass characteristics. Calf-fed Holstein steers fed 100% MP requirements during the initial 112-d feeding period had greater ( P  ≤ 0.02) ADG, G:F, observed/expected NE values for maintenance and gain, and live BW compared with steers fed 87% of the expected MP requirements. However, there was no effect ( P  ≥ 0.17) of MP supply during the initial 112-d period on overall (342 d) growth performance measurements. The incidence of liver abscesses was low (averaging 7.7%) and not affected by dietary treatments. We conclude that, independent of MP supplies, supplemental VM enhances overall growth performance and efficiency of energy utilization of calf-fed Holstein steers., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.)

The aim of this trial was to test the effects of the use of eubiotics (pro- and prebiotics) alone or in combination in the diet of lambs finished under subtropical climate conditions. For this purpose, 40 Pelibuey × Katahdin lambs (29.5 ± 4.8 kg initial live weight) were used in a 93 day growth-performance experiment. Dietary treatments consisted of a cracked corn-based finishing diet supplemented with (1) no eubiotics (control), (2) 3 g of probiotics (live Saccharomyces cerevisiae , SC), (3) 3 g of prebiotics (mannan oligosaccharide plus b-glucans, MOS), and (4) a combination of 1.5 g of SC and 1.5 g of MOS (SC+MOS). Throughout the study, the average temperature humidity index (THI) was 78.60. Compared to controls, supplementation with SC or MOS, alone did not affect average daily gain (ADG), but enhanced feed efficiency by 5.6% and 6.9% (gain-to-feed ratio, G:F) and dietary net energy by 4.6% and 5.9%, respectively. Compared to controls, SC+MOS enhanced ADG (10%), G:F (9.5%), and dietary net energy (7.2%). Lambs fed SC+MOS had also greater ADG, G:F, and dietary net energy compared to lambs fed SC alone. When compared to MOS, the combination enhanced ADG (10.4%, p = 0.04). This effect could be attributed to the increased dry matter intake (7.6%, p = 0.06), as neither G:F nor dietary energy was significantly affected. Compared with controls and SC, supplementation with MOS alone and SC+MOS increased kidney-pelvic-heart fat, while SC supplementation tended ( p = 0.08) to reduce 4.1% the relative intestinal mass (as a proportion of empty body weight) when compared to controls. Treatment effects on the other carcass measures were not significant. In the present study, supplemental probiotics and/or prebiotics improved dietary energetic efficiency in lambs finished under subtropical climatic conditions. The combination of probiotics with prebiotics reinforced this positive effect.

Objective: To evaluate the influence of the unsaturated to saturated ratio of fatty acids (FAs) reaching the duodenum on postruminal digestion of FAs, mainly focused on stearic acid (C18:0)., Materials and Methods: Six Holstein steers [208 ± 3 kg initial live weight (LW)] with cannulas in the abomasum and proximal duodenum were used in a replicated 3 × 3 Latin square design. Steers were fed a fixed amount of a basal steam-flaked corn-based diet containing 8% supplemental fat and were daily infused via abomasum with 0, 67, and 165 gm oleic acid (C18:1). The experiment lasted for 42 days., Results: The daily total FA (TFA) intake (dietary FA intake plus abomasal infusion of oleic acid) represented a 1.78, 2.10, and 2.56 gm TFA/kg LW ratio. The unsaturated to saturated ratio of FAs entering the duodenum increased ( p < 0.01) as level C18:1 infusion into the abomasum increased. Infusion of C18:1 tended (quadratic component, p = 0.07) to improve postruminal TFA digestion, being maximal for the 67 gm/day infusions. This increase in TFA digestion was due to increased (quadratic component, p = 0.03) postruminal C18:0 digestion (postruminal digestion of the other FAs was not different, p ≥ 0.13)., Conclusion: Increasing the unsaturated to saturated ratio of FAs entering the small intestine will enhance intestinal C18:0 digestion. This positive effect is expected to be more likely beneficial when FA intake is high (and thus, the duodenal flow of FA is high), but this benefit looks diminished when the quantity of TFA reaching the intestine exceeds the proportion of 2.13 gm FA/kg LW., Competing Interests: No potential conflict of interest was reported by the authors., (Copyright: © Journal of Advanced Veterinary and Animal Research.)

Two experiments were conducted to compare a supplemental blend of essential oils alone (EO) or combined with enzymes (EO + ENZ) versus virginiamycin (VM), on characteristics of growth performance (Exp. 1) and digestion (Exp. 2) in finishing lambs. Lambs were fed a high-energy finishing diet supplemented with: (1) no supplement (control); (2) 150 mg supplemental EO; (3) 150 mg supplemental EO plus 560 mg alpha-amylase (EO + ENZ); and 4) 25 mg VM. Compared with the control, growth performance response to EO and VM were similar, enhancing (5.7%, p < 0.05) feed efficiency and observed dietary net energy. Compared with control, supplementation with EO + ENZ tended ( p = 0.09) to increase dry matter intake (6.8%), improving ( p < 0.05) weight gain and feed efficiency (10.4 and 4.4%, respectively). Dietary energy utilization was greater (2.7%, p < 0.05) for EO and VM than EO + ENZ. Treatment effects on the carcass and visceral mass were small, but additive supplementation decreased ( p ≤ 0.03) the relative weight of the intestines. There were no treatment effects on measures of digestion nor digestible energy of the diet. Supplemental EO may be an effective alternative to VM in high-energy finishing diets for feedlot lambs. Combination EO + ENZ may further enhance dry matter intake, promoting increased weight gain.

Objective: The objective of this experiment was to evaluate the effect of shade allocation and shade plus fan on growth performance, dietary energy utilization and carcass characteristics of feedlot cattle under tropical ambient conditions., Methods: Two trials were conducted, involving a total of 1,560 young bulls (289±22 kg BW) assigned to 24 pens (65 bulls/pen and 6 pens/treatment). Pens were 585 m2 with 15 m fence line feed bunks. Shade treatments (m2 shade/animal) were: i) limited shade (LS) to 1.2 m2shade/animal (LS1.2); ii) limited shade to 2.4 m2 shade/animal (LS2.4); iii) total shade (TS) which correspond to 9 m2/animal, and iv) total shade equipped with fans (TS+F). Trials lasted 158 and 183 days. In both studies, the average weekly maximum temperature exceeded 34°C., Results: Increasing shade allocation tended (p = 0.08) to linearly increases average daily gain (ADG), and dry matter intake (DMI, quadratic effect, p = 0.03). This effect was most apparent between LS1.2 and LS2.4. Shade allocation, per se, did not affect gain efficiency or estimated dietary net energy (NE). Compared with TS, TS+F increased (p<0.05) ADG, gain efficiency, and tended (p = 0.06) to increase dietary NE. There was a quadratic effect of shade on longissimus area and marbling score, with values being lower (p<0.01) for LS2.4 than for LS1.2 or TS. Likewise, marbling score was lower for TS+F than for TS. Percentage kidney, pelvic, and heart (KPH) linearly decreased with increasing shade. In contrast, KPH was greater for TS than for TS+F., Conclusion: Providing more than 2.4 m2 shade/animal will not further enhance feedlot performance. The use of fans in combination with shade increases ADG and gain efficiency beyond that of shade, alone. These enhancements were not associated with increased DMI, but rather, to an amelioration of ambient temperature humidity index on maintenance energy requirement.

Objective: We compare the effects of three different approved sources of supplemental zilpaterol on growth-performance responses and carcass characteristics of finishing lambs., Methods: Twenty four Pelibuey×Katahdin lambs (46.75±2.43 kg) were used in a 33-day feeding trial. Lambs were fed a dry rolled corn-based finishing diet. Treatments consisted of the non-supplemental basal diet (Control) versus the basal diet supplemented with 125 mg zilpaterol/kg of diet (as fed basis) from three commercial sources marketed in Mexico: Zilmax (ZIL), Grofactor, and Zipamix., Results: Compared to controls, zilpaterol (ZH) supplementation did not affect dry matter intake (DMI), but increased carcass adjusted daily weight gain (ADG, 36.7%), gain efficiency (34.2%), and dietary net energy (26.0%), and decreased (23.4%) the ratio of observed:expected DMI. Compared to controls, supplemental ZH increased hot carcass weight (6.4%), dressing percentage (3.2%), m. longissimus thoracis (LM) area (15.6%), and shoulder muscle:fat ratio (28.7%), but decreased kidney-pelvic-heart fat, and fat thickness. Supplemental ZH increased 10.9% and 14.3% whole cut weight of loin and leg, respectively, and the proportion (as percentage of cold carcass weight) of leg (4.3%). These increases were reflected in greater forequarter and hindquarter weights. Lambs fed ZH increased (4.6%) empty body weight (EBW) and reduced (14.7%) liver/spleen weight (as g/kg EBW). Likewise, ZH supplementation tended (p = 0.08) to lower (8.9%) visceral fat. Growth performance, energetic efficiency, hot carcass weight, dressing percentage, LM area and whole cuts were not different across supplemental ZH sources. However, compared with non-supplemented controls, only ZIL appreciably decreased carcass fat distribution, including fat thickness, percentage kidney pelvic and heart fat, shoulder fat, and visceral fat., Conclusion: Supplemental ZH increases ADG, gain efficiency, carcass dressing percentage, and LM area. The magnitude of these responses was similar among ZH sources. Nevertheless, compared with non-supplemented controls, only ZIL appreciably decreases carcass fat. The basis for this is uncertain, but indicative that some practical differences in zilpaterol bio-equivalency may exist across commercial sources tested.

Sorghum panicle residue (SPR), a by-product of Sorghum vulgare, obtained in the manufacture of brooms and wisks, has potential as a partial substitute for grain in growing-finishing diets for feedlot lambs. Accordingly, 48 Pelibuey×Katahdin lambs (initial weight=16.2±4.3 kg) were used in an 84-d growth-performance trial to evaluate its comparative feeding value. Lambs were blocked by weight and assigned within weight groupings to 12 pens (4 lambs per pen). The SPR was finely ground before it was incorporated into the diet. The basal diet contained 60% whole grain sorghum (WGS; DM basis). Dietary treatments consisted in the replacement of WGS with 0, 50, or 100% SPR. Replacement of WGS with SPR decreased (linear effect, P=0.04) average daily gain (ADG), and tended to increase (linear effect, P=0.06) dry matter intake (DMI). Replacement of WGS with SPR decreased (linear effect, P&lt;0.01) gain efficiency (ADG : DMI), and observed dietary net energy (NE), as well as hot carcass weight, dressing percentage, kidney-pelvic-heart fat, and back fat thickness (linear effect, P⩽.05) Other carcass characteristics and wholesale cuts as a percentage of cold carcass weight were not affected by dietary treatments. It is concluded that SPR is a palatable feed ingredient for inclusion in finishing diets for feedlot lambs. The comparative NE values for SPR are 1.50 and 0.91 Mcal/kg for maintenance and gain, respectively, 75% the NE value of WGS. These NE values reflect the greater fiber content of SPR. To the extent that dietary energy density limits energy intake (and hence daily weight gain), appropriate constraints on level of SPR incorporation is warranted.

Objective: The influence of substituting steam-flaked corn (SFC) for dry rolled corn (DRC) on feedlot cattle growth performance and dietary net energy when cattle are allowed either ad libitum or 2-h restricted access to the finishing diet was evaluated., Methods: Treatment effects were tested using 96 crossbred steers (251±2 kg) during the initial 56 d of the finishing phase. Cattle were blocked by weight and randomly assigned within blocks to 16 pens (4 pens/treatment). Bunk space was sufficient (41 cm/head) to allow all steers access to the feed bunk at the same time. Treatments consisted of two finishing diets containing (dry matter basis) 77.1% corn grain processed by dry rolling (density = 0.50 kg/L) or steam flaking (density = 0.36 kg/L). Cattle were fed twice daily at 06:00 and 14:00 h, allowing for approximately 5% residual. In the case of restricted feeding, steers were allowed access to feeders for 1 h following each feeding, after which residual feed was withdrawn., Results: There were no treatment interactions on dry matter intake (DMI), average daily gain (ADG), gain efficiency (G:F), or dietary net energy (NE). Restricting feed access time reduced (p <0.01) feed intake, and hence, ADG. Substitution of SFC for DRC increased (p<0.01) ADG, feed efficiency (G:F), and estimated dietary NE, without affecting DMI. Based on tabular net energy of maintenance (NE m ) value (2.18 Mcal/kg) for DRC, the estimated NE m value for SFC using the replacement technique, averaged 2.44 Mcal/kg; an improvement of 10.7%. The ratio of observed-to-expected dietary NE was not affected by feed access time., Conclusion: Substitution of SFC for DRC in finishing diets for feedlot cattle enhanced ADG, gain efficiency, and the NE value of the diet. Although restriction of feed access time depressed DMI and ADG, it did not affect the comparative benefit of steam flaking toward enhancement of ADG, G:F, and dietary NE.

Objective: This study was determined the influence of virginiamycin supplementation on growth-performance and characteristics of digestion of cattle with decreasing dietary net energy value of the diet for maintenance (NE m ) from 2.22 to 2.10 Mcal/kg., Methods: Eighty crossbred beef steers (298.2±6.3 kg) were used in a 152-d performance evaluation consisting of a 28-d adaptation period followed by a 124-d growing-finishing period. During the 124-d period steers were fed either a lesser energy dense (LED, 2.10 Mcal/kg NE m ) or higher energy dense (HED, 2.22 Mcal/kg NE m ) diet. Diets were fed with or without 28 mg/kg (dry matter [DM] basis) virginiamycin in a 2×2 factorial arrangement. Four Holstein steers (170.4±5.6 kg) with cannulas in the rumen (3.8 cm internal diameter) and proximal duodenum were used in 4×4 Latin square experiment to study treatment effects on characteristics of digestion., Results: Neither diet energy density nor virginiamycin affected average daily gain (p>0.10). As expected, dry matter intake and gain efficiency were greater (p<0.01) for LED- than for HED-fed steers. Virginiamycin did not affect estimated net energy value of the LED diet. Virginiamycin increased estimated NE of the HED diet. During daylight hours when the temperature humidity index averaged 81.3±2.7, virginiamycin decreased (p<0.05) ruminal temperature. Virginiamycin did not influence (p>0.10) ruminal or total tract digestion. Ruminal (p = 0.02) and total tract digestion (p<0.01) of organic matter, and digestible energy (p<0.01) were greater for HED vs LED. Ruminal microbial efficiency was lower (p<0.01) for HED vs LED diets., Conclusion: The positive effect of virginiamycin on growth performance of cattle is due to increased efficiency of energy utilization, as effects of virginiamycin on characteristics of digestion were not appreciable. Under conditions of high ambient temperature virginiamycin may reduce body temperature.

Objective: Two trials were conducted in order to examine the effects of level of supplemental methionine on productive performance, dietary energetic, plasma amino acid concentration, and digestive function., Methods: Dietary treatments consisted of a steam-flaked corn-based diet containing urea as the only source of supplemental nitrogen supplemented with no supplemental amino acid (control), or control plus 1.01% lysine and 0.032%, 0.064%, 0.096%, or 0.128% methionine. In Trial 1, 150 Holstein steer calves (127±4.9 kg) were utilized to evaluate the influence of treatments on growth-performance, dietary energetic, plasma amino acid concentration during the first 112 days of growing period. During the initial 56-d period calves received the 5 experimental diets. During the subsequent 56-d period all calves were fed the control diet., Results: During the initial 56-d period, methionine supplementation increased (linear effect, p<0.01) plasma methionine. In the presence of supplemental lysine, increases on level of methionine in diet did not affect average daily gain. However, increased gain efficiency (quadratic effect, p = 0.03) and estimated dietary net energy (NE; linear effect, p = 0.05). Estimated metabolizable methionine supply was closely associated (R 2 = 0.95) with efficiency NE utilization for maintenance and gain. During the subsequent 56-d period, when all calves received the control diet (no amino acid supplementation), plasma amino acid concentrations and growth performance was not different among groups. However, the effects of methionine supplementation during the initial 56-period carried over, so that following a 56-d withdrawal of supplementation, the overall 112-d effects on gain efficiency (quadratic effect, p = 0.05) dietary NE (linear effect, p≤0.05) remained appreciable. In Trial 2, 5 cannulated Holstein steers were used to evaluate treatment effects on characteristics of digestion and amino acid supply to the small intestine. There were no treatment effects on flow of dietary and microbial N to the small intestine. Postruminal N digestion increased (p = 0.04) with increasing level of supplemental methionine. Methionine supplementation linearly increased (p<0.01) duodenal flow of methionine. Likewise, lysine supplementation increased an average of 4.6% (p = 0.04) duodenal flow of lysine. In steers that received non-supplemented diet, observed intestinal amino acid supply were in good agreement with expected., Conclusion: We conclude that addition of rumen-protected methionine and lysine to diets may enhance gain efficiency and dietary energetics of growing Holstein calves. Observed amino acid supply to the small intestine were in good agreement with expected, supportive of NRC (2000, Level 1).

Recent findings have shown that microbial nitrogen flow and digestible energy of diets are increased when urea is combined with a slow-release urea (SRU) in diets with a starch to acid detergent fibre ratio (S:F) 4:1. This affect is attributable to enhanced synchrony between ruminal N availability for microbial growth and carbohydrate degradation. To verify the magnitude of this effects on lamb performance, an experiment was conducted to evaluate the effects of combining urea and a SRU in diets containing S:F ratios of 3:1, 4:1, or 5:1 on performance, dietary energetics and carcass characteristics of finishing lambs. For that, 40 Pelibuey×Katahdin lambs (36.65±3 kg) were assigned to one of five weight groupings in 20 pens (5 repetition/treatments). The S:F ratio in the diet was manipulated by partially replacing the corn grain and dried distiller's grain with solubles by forage (wheat straw) and soybean meal to reach S:F ratios of 3:1, 4:1 or 5:1. An additional treatment of 4:1 S:F ratio with 0.8% urea as the sole source of non-protein nitrogen was used as a reference for comparing the effect of urea combination vs. conventional urea at the same S:F ratio. There were no treatment effects on dry matter intake (DMI). Compared the urea combination vs urea at the same S:F ratio, urea combination increased (p<0.01) average daily gain (ADG, 18.3%), gain for feed (G:F, 9.5%), and apparent energy retention per unit DMI (8.2%). Irrespective of the S:F ratio, the urea combination improved the observed-to-expected dietary ratio and apparent retention per unit DMI was maximal (quadratic effect, p≤0.03) at an S:F ratio of 4:1, while the conventional urea treatment did not modify the observed-to-expected net energy ratio nor the apparent retention per unit DMI at 4:1 S:F ratio. Urea combination group tended (3.8%, p = 0.08) to have heavier carcasses with no effects on the rest of carcass characteristics. As S:F ratio increased, ADG, G:F, dietary net energy, carcass weight, dressing percentage and longissimus thoracis (LM) area increased linearly (p≤0.02). Combining urea and a slow-release urea product results in positive effects on growth performance and dietary energetics, but the best responses are apparently observed when there is a certain proportion (S:F ratio = 4:1) of starch to acid detergent fibre in the diet.

Two experiments were conducted to examine the influence of kaolinite clay supplementation (0%, 1%, or 2% diet dry matter [DM] basis) on characteristics of digestion (Trial 1) and growth performance (Trial 2) in calf-fed Holstein steers fed a finishing diet. In Trial 1, 6 Holstein steers (539±15 kg) with ruminal and duodenal cannulas were used to evaluate treatment effects on characteristics of digestion. Kaolinite clay supplementation decreased total tract DM digestion (linear effect, p<0.01) without effects (p≥0.10) on site and extent of digestion of organic matter, neutral detergent fiber, starch and N, or ruminal microbial efficiency. There were no treatment effects on ruminal pH, volatile fatty acids molar proportions or estimated methane production. In Trial 2, 108 Holstein steers (132.4±5.6 kg) were used in a 308-d study to evaluate growth performance and carcass characteristics. There were no treatment effects (p>0.10) on average daily gain (ADG) and gain efficiency (ADG/dry matter intake). Kaolinite supplementation tended (linear effect, p = 0.08) to increase dietary net energy (NE) during the initial 112-d period. However, the overall (308-d) effect of supplementation dietary NE was not appreciable (p>0.20). However, due to the inertness of kaolinite, itself, the ratio of observed-to-expected dietary NE increased with kaolinite supplementation. This effect was more pronounced (linear effect, p 0.03) during the initial 224 d of the study. Overall (308 d), kaolinite supplementation tended to increase (linear effect, p = 0.07) dietary NE by 3% over expected. Kaolinite supplementation did not affect carcass weight, yield grade, longissimus area, kidney, pelvic and heart fat, and quality grade, but decreased (linear effect, p = 0.01) dressing percentage. It is concluded that kaolinite supplementation up to 2% of diet DM may enhance energetic efficiency of calf-fed Holstein steers in a manner independent of changes in characteristics of ruminal and total tract digestion.

Two experiments were conducted to examine the influence of protein and virginiamycin (VM) supplementation on feedlot growth performance, digestion, and metabolizable AA (MAA) supply of calf-fed Holstein steers. Growth performance and dietary energetics were evaluated in 120 Holstein steers (127 ± 9 kg). During the initial 112-d feeding period, a steam-flaked corn-based diet was balanced to meet either 100% (MAB) or 87% (UREA) of MAA requirements. Diets were supplemented with or without 22.5 mg/kg VM in a 2 × 2 factorial arrangement. Subsequently (d 112 to 308), all steers received the UREA diet with or without VM. During the initial 112-d, MAB increased ADG, G:F, and dietary NE ( < 0.01). Thereafter, when all steers received the UREA diet, ADG, G:F, and dietary NE were not different ( > 0.10) across initial supplementation treatments. Overall (d 1 to 308), MAB did not affect ADG ( > 0.10) but enhanced G:F efficiency ( = 0.03) and dietary NE ( = 0.05). During the initial 112-d period and through the remainder of the experiment, VM increased G:F ( < 0.01) and dietary NE ( < 0.01). Four Holstein steers (146 ± 4 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square design to evaluate initial 112-d treatment effects on digestive function. There were no treatment effects ( > 0.10) on ruminal digestion of OM, NDF, starch, microbial efficiency, or total tract digestion of OM and NDF. The MAB increased indispensable AA flow to the small intestine ( < 0.01) and total tract digestion of N ( < 0.01) and starch ( = 0.04). Observed AA supply to small intestine was in agreement with expected supply ( = 0.96). Virginiamycin decreased ( = 0.04) nonammonia N flow to the small intestine and did not affect ( > 0.10) total tract N digestion. Extrapolating from AA supplies in the metabolism study, MAB satisfied indispensable AA requirements during the initial 112-d period, whereas the UREA diet met 73.5% and 79.2% of methionine and lysine requirements, respectively. During the subsequent periods (d 112 to 308) indispensable AA supplies exceeded theoretical requirements. We conclude that enhancements in energy utilization when diets are balanced to meet MAA requirements of calf-fed Holstein steers during the initial 112-d feedlot period remain appreciable throughout time on feed. Virginiamycin enhanced efficiency of energy utilization throughout the feedlot growing-finishing period.

The objective of this experiment was to determine the feeding value of a mechanically extracted nontoxic variety of oil (JCO) as source of energy for feedlot lambs. Twenty Pelibuey × Katahdin lambs were individually fed a dry-rolled-corn-based finishing diet supplemented with 0%, 2%, 4%, or 6% JCO (diet dry matter basis). Supplemental JCO replaced dry rolled corn in the basal diet. Fatty acid composition of JCO was C16:0, 14.0%; C18:0, 8.2%; C18:1, 26.0%; C18:2, 50.3%, and C18:3, 0.4%. Daily intakes of JCO averaged 24.7, 51.1, and 77.3 g/day or 0.57, 1.08, and 1.62 g/kg LW for the 2%, 4%, and 6% levels of supplementation, respectively. Supplemental JCO did not affect ( = 0.33) dry matter intake (DMI), but tended to increase (linear effect, = 0.06) average daily gain, efficiency of gain (linear effect, < 0.01), and dietary net energy (linear effect, < 0.01) and decreased (linear effect, < 0.01) the ratio of observed/expected DMI. At low levels (20 g/kg diet dry matter) of supplementation, the net energy (NE) value of JCO corresponds closely (0.99) to the NE value assigned by current standards (), and this NE value decreased linearly as the inclusion level of JCO increased. There were not treatment effects on plasma metabolites. Across treatments, the concentrations of hemoglobin (11.64 ± 1.08 g/dL), hematocrit (39.15 ± 3.67%), glucose (85.2 ± 17.64 mg/dL), creatinine (1.43 ± 0.28 mg/dL), and urea (20.70 ± 4.35 mg/dL) were within normal (9-15 g/dL, 27%-40%, 50-90 mg/dL, 1.0-1.8 mg/dL, and 15-50 mg/dL, for hemoglobin, hematocrit, glucose, creatinine, and urea, respectively) ranges for healthy lambs. Based on DMI, performance and plasma metabolites observed in this study, nontoxic JCO is a suitable source of energy in finishing diets for lambs.

Eight Holstein steers (216±48 kg body weight) fitted with ruminal and duodenal cannulas were used to evaluate effects of wheat straw processing (ground vs pelleted) at two straw inclusion rates (7% and 14%; dry matter basis) in dry rolled or steam-flaked corn-based finishing diets on characteristics of digestion. The experimental design was a split plot consisting of two simultaneous 4×4 Latin squares. Increasing straw level reduced ruminal (p<0.01) and total tract (p = 0.03) organic matter (OM) digestion. As expected, increasing wheat straw level from 7% to 14% decreased (p<0.05) ruminal and total tract digestion of OM. Digestion of neutral detergent fiber (NDF) and starch, per se, were not affected (p>0.10) by wheat straw level. Likewise, straw level did not influence ruminal acetate and propionate molar proportions or estimated methane production (p>0.10). Pelleting straw did not affect (p≥0.48) ruminal digestion of OM, NDF, and starch, or microbial efficiency. Ruminal feed N digestion was greater (7.4%; p = 0.02) for ground than for pelleted wheat straw diets. Although ruminal starch digestion was not affected by straw processing, post-ruminal (p<0.01), and total-tract starch (p = 0.05) digestion were greater for ground than for pelleted wheat straw diets, resulting in a tendency for increased post-ruminal (p = 0.06) and total tract (p = 0.07) OM digestion. Pelleting wheat straw decreased (p<0.01) ruminal pH, although ruminal volatile fatty acids (VFA) concentration and estimated methane were not affected (p≥0.27). Ruminal digestion of OM and starch, and post-ruminal and total tract digestion of OM, starch and N were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal NDF digestion was greater (p = 0.02) for dry rolled than for steam-flaked corn, although total tract NDF digestion was unaffected (p = 0.94). Ruminal microbial efficiency and ruminal degradation of feed N were not affected (p>0.14) by corn processing. However, microbial N flow to the small intestine and ruminal N efficiency (non-ammonia N flow to the small intestine/N intake) were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal pH and total VFA concentration were not affected (p≥ 0.16) by corn processing method. Compared with dry rolled corn, steam-flaked corn-based diets resulted in decreased acetate:propionate molar ratio (p = 0.02). It is concluded that at 7% or 14% straw inclusion rate, changes in physical characteristics of wheat straw brought about by pelleting negatively impact OM digestion of both steam-flaked and dry-rolled corn-based finishing diets. This effect is due to decreased post-ruminal starch digestion. Replacement of ground straw with pelleted straw also may decrease ruminal pH.

Twenty Pelibuey×Katahdin ewes (35±2.3 kg) were used to determine the effects of the consumption of standardized plant extract containing a mixture of quaternary benzophenanthridine alkaloids and protopine alkaloids (QBA+PA) on growth performance, dietary energetics, visceral mass, and ruminal epithelial health in heat-stressed ewes fed with a high-energy corn-based diet. The basal diet (13.9% crude protein and 2.09 Mcal of net energy [NE] of maintenance/kg of dry matter) contained 49.7% starch and 15.3% neutral detergent fiber. Source of QBA+PA was Sangrovit RS (SANG) which contains 3 g of quaternary benzophenathridine and protopine alkaloids per kg of product. Treatments consisted of a daily consumption of 0 or 0.5 g SANG/ewe. Ewes were grouped by weight and assigned to 10 pens (5 pens/treatment), with two ewes per pen. The experimental period lasted 70 days. The mean temperature humidity index during the course of this experiment was 81.7±1.0 (severe heat stress). There were no treatment effects on water intake. Dry matter intake was not affected (p = 0.70) by treatments, but the group fed SANG had a numerically (11.2%) higher gain in comparison to the control group, SANG improved gain efficiency (8.3%, p = 0.04), dietary NE (5.2%, p<0.01) and the observed-to-expected NE (5.9%, p<0.01). Supplemental SANG did not affect (p≥0.12) carcass characteristics, chemical composition of shoulder, and organ weights (g/kg empty body weight) of stomach complex, intestines, and heart/lung. Supplemental SANG decreased liver weight (10.3%, p = 0.02) and increased visceral fat (16.9%, p = 0.02). Rumen epithelium of ewes fed SANG had lower scores for cellular dropsical degeneration (2.08 vs 2.34, p = 0.02), parakeratosis (1.30 vs 1.82, p = 0.03) and neutrophil infiltration (2.08 vs 2.86, p = 0.05) than controls. It is concluded that SANG supplementation helped ameliorate the negative effects of severe heat on growth performance of feedlot ewes fed high-energy corn-based diets. Improvement in energetic efficiency may have been mediated, in part, by anti-inflammatory effects of supplemental SANG and corresponding enhancement of nutrient uptake.

Four Holstein steers with ruminal and duodenal cannulas were used in a 4 × 4 Latin square design to examine the effect of daily intake of 0, 2, 4 or 6 g/steer of standardized plant extract containing a mixture of quaternary benzophenanthridine alkaloids and protopine alkaloids (QBA+PA) on the characteristics of ruminal fermentation and characteristics of digestion. The basal diet consisted of a steam-flaked corn-based finishing diet that contained 62% corn and 12% sudangrass hay and the rest of diet was composed of mainly dried distillers grains, molasses, fat, and minerals. The source of QBA+PA used was Sangrovit-RS (Phytobiotics Futterzusatzstoffe GmbH, Eltville, Germany) and supplementation levels of 2, 4, and 6 g Sangrovit-RS∙steer∙d, which represented a net daily ingestion of approximately 6, 12, and 18 mg of QBA+PA compounds, respectively. Inclusion of QBA+PA linearly increased ( = 0.04) flow to the duodenum of nonammonia N and linearly decreased ( < 0.01) duodenal flows of ammonia N. Ruminal microbial efficiency (duodenal microbial N; g/kg OM fermented in the rumen) and protein efficiency (duodenal nonammonia N; g/g N intake) were increased ( < 0.05) as the level of QBA+PA increased. There were no effects of QBA+PA supplementation on ruminal, postruminal, and total tract digestion of OM, starch, and NDF, but postruminal and total tract digestion of N increased ( < 0.01) as the level of QBA+PA increased. Digestible energy of the diet tended to increase (linear affect, = 0.09) with QBA+PA supplementation. Ruminal pH and total VFA molar concentrations were not different between treatments. Ruminal NH-N concentration linearly decreased ( = 0.02) with QBA+PA supplementation. Ruminal molar proportion of acetate increased ( = 0.04) as the supplementation level of QBA+PA increased. It is concluded that QBA+PA supplementation enhances efficiency of N utilization in feedlot steers fed a steam-flaked corn-based finishing diet. This effect was due, in part, to enhanced ruminal microbial efficiency, decreased ruminal degradation of dietary nonammonia N, and enhanced postruminal N digestion.

In experiment 1, eighty crossbred steers (239±15 kg) were used in a 229-d experiment to evaluate the effects of increasing levels of enzymatically hydrolyzed yeast (EHY) cell wall in diets on growth performance feedlot cattle during periods of elevated ambient temperature. Treatments consisted of steam-flaked corn-based diets supplemented to provide 0, 1, 2, or 3 g EHY/hd/d. There were no effects on growth performance during the initial 139-d period. However, from d 139 to harvest, when 24-h temperature humidity index averaged 80, EHY increased dry matter intake (DMI) (linear effect, p<0.01) and average daily gain (ADG) (linear effect, p = 0.01). There were no treatment effects (p>0.10) on carcass characteristics. In experiment 2, four Holstein steers (292±5 kg) with cannulas in the rumen and proximal duodenum were used in a 4×4 Latin Square design experiment to evaluate treatments effects on characteristics of ruminal and total tract digestion in steers. There were no treatment effects (p>0.10) on ruminal pH, total volatile fatty acid, molar proportions of acetate, butyrate, or estimated methane production. Supplemental EHY decreased ruminal molar proportion of acetate (p = 0.08), increased molar proportion of propionate (p = 0.09), and decreased acetate:propionate molar ratio (p = 0.07) and estimated ruminal methane production (p = 0.09). It is concluded that supplemental EHY may enhance DMI and ADG of feedlot steers during periods of high ambient temperature. Supplemental EHY may also enhance ruminal fiber digestion and decrease ruminal acetate:propionate molar ratios in feedlot steers fed steam-flaked corn-based finishing diets.

Two trials were conducted to evaluate the influence of supplemental urea withdrawal on characteristics of digestion (Trial 1) and growth performance (Trial 2) of feedlot cattle during the last 40 days on feed. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with urea to provide urea fermentation potential (UFP) of 0, 0.6, and 1.2%. In Trial 1, six Holstein steers (160 ± 10 kg) with cannulas in the rumen and proximal duodenum were used in a replicated 3 × 3 Latin square experiment. Decreasing supplemental urea decreased (linear effect, P ≤ 0.05) ruminal OM digestion. This effect was mediated by decreases (linear effect, P ≤ 0.05) in ruminal digestibility of NDF and N. Passage of non-ammonia and microbial N (MN) to the small intestine decreased (linear effect, P = 0.04) with decreasing dietary urea level. Total tract digestion of OM (linear effect, P = 0.06), NDF (linear effect, P = 0.07), N (linear effect, P = 0.04) and dietary DE (linear effect, P = 0.05) decreased with decreasing urea level. Treatment effects on total tract starch digestion, although numerically small, likewise tended (linear effect, P = 0.11) to decrease with decreasing urea level. Decreased fiber digestion accounted for 51% of the variation in OM digestion. Ruminal pH was not affected by treatments averaging 5.82. Decreasing urea level decreased (linear effect, P ≤ 0.05) ruminal N-NH and blood urea nitrogen. In Trial 2, 90 crossbred steers (468 kg ± 8), were used in a 40 d feeding trial (5 steers/pen, 6 pens/ treatment) to evaluate treatment effects on final-phase growth performance. Decreasing urea level did not affect DMI, but decreased (linear effect, P ≤ 0.03) ADG, gain efficiency, and dietary NE. It is concluded that in addition to effects on metabolizable amino acid flow to the small intestine, depriving cattle of otherwise ruminally degradable N (RDP) during the late finishing phase may negatively impact site and extent of digestion of OM, depressing ADG, gain efficiency, and dietary NE.

Forty-eight crossbred heifers (378.1±18 kg) were used in a 56-d feeding trial (four pens per treatment in a randomised complete block design) to evaluate the influence of ionophore supplementation on growth performance, dietary energetics and carcass characteristics in finishing cattle during a period of heat stress. Heifers were fed a diet based on steam-flaked corn (2.22 Mcal NEm/kg) with and without an ionophore. Treatments were: i) control, no ionophore; ii) 30 mg/kg monensin sodium (RUM30); iii) 20 mg/kg lasalocid sodium (BOV20), and iv) 30 mg/kg lasalocid sodium (BOV30). Both dry matter intake (DMI) and climatic variables were measured daily and the temperature humidity index (THI) was estimated. The maximum THI during the study averaged 93, while the minimum was 70 (THI average = 79.2±2.3). Compared to controls, monensin supplementation did not influence average daily gain, the estimated NE value of the diet, or observed-to-expected DMI, but tended (p = 0.07) to increase (4.8%) gain to feed. Compared to controls, the group fed BOV30 increased (p≤0.03) daily gain (11.8%), gain to feed (8.3%), net energy of the diet (5%), and observed-to-expected DMI (5.2%). Daily weight gain was greater (7.6%, p = 0.05) for heifers fed BOV30 than for heifers fed MON30. Otherwise, differences between the two treatments in DMI, gain to feed, and dietary NE were not statistically significant (p>0.11). Plotting weekly intakes versus THI, observed intake of controls was greater (p<0.05) at THI values ≤77 than ionophore groups. When THI values were greater than 79, DMI of control and MON30 were not different (p = 0.42), although less than that of groups fed lasalocid (p = 0.04). Variation in energy intake was lower (p>0.05) in the ionophores group (CV = 1.7%) than in the control group (CV = 4.5%). Inclusion of ionophores in the diet resulted in relatively minor changes in carcass characteristics. It is concluded that ionophore supplementation did not exacerbate the decline of DM intake in heat-stressed cattle fed a high-energy finishing diet; on the contrary, it stabilised feed intake and favoured feed efficiency. Ionophore supplementation reduced estimated maintenance coefficients around 10% in finishing cattle during a period of heat stress. This effect was greatest for heifers supplemented with 30 mg lasalocid/kg of diet.

Four male lambs (Katahdin; average live weight 25.9±2.9 kg) with "T" type cannulas in the rumen and proximal duodenum were used in a 4×4 Latin square experiment to evaluate the influence of supplemental dry distillers grain with solubles (DDGS) levels (0, 10, 20 and 30%, dry matter basis) in substitution for dry-rolled (DR) corn on characteristics of digestive function and digestible energy (DE) of diet. Treatments did not influence ruminal pH. Substitution of DR corn with DDGS increased ruminal neutral detergent fiber (NDF) digestion (quadratic effect, p<0.01), but decreased ruminal organic matter (OM) digestion (linear effect, p<0.01). Replacing corn with DDGS increased (linear, p≤0.02) duodenal flow of lipids, NDF and feed N. But there were no treatment effects on flow to the small intestine of microbial nitrogen (MN) or microbial N efficiency. The estimated UIP value of DDGS was 44%. Postruminal digestion of OM, starch, lipids and nitrogen (N) were not affected by treatments. Total tract digestion of N increased (linear, p = 0.04) as the DDGS level increased, but DDGS substitution tended to decrease total tract digestion of OM (p = 0.06) and digestion of gross energy (p = 0.08). However, it did not affect the dietary digestible energy (DE, MJ/kg), reflecting the greater gross energy content of DDGS versus DR corn in the replacements. The comparative DE value of DDGS may be considered similar to the DE value of the DR corn it replaced up to 30% in the finishing diets fed to lambs.

Two experiments were conducted to examine the effect of level of dried distillers grains plus solubles (DDGS) supplementation (0, 10, 20, and 30%; DM basis), replacing steam-flaked (SF) corn in finishing diets, on characteristics of digestion (Exp. 1) and growth performance (Exp. 2) in calf-fed Holstein steers. In Exp.1, 4 cannulated Holstein steers (349 ± 12 kg) were used to evaluate treatment effects on characteristics of digestion. Ruminal NDF digestion tended to increase (quadratic effect, P = 0.09) and ruminal OM digestion decreased (linear effect, P = 0.01) with DDGS substitution. There were no treatment effects on duodenal flow of microbial N (MN). Substitution with DDGS increased (linear effect, P < 0.01) N flow to the small intestine. The undegradable intake protein (UIP) value of DDGS was 35%. Postruminal digestion of OM (linear effect, P = 0.04) and fatty acids (linear effect, P = 0.03) and total tract digestion of OM and GE decreased (linear effect, P < 0.03) with increasing level of DDGS substitution. Substitution with DDGS did not affect (P = 0.80) ruminal pH but increased (linear effect, P = 0.01) acetate:propionate molar ratio. In Exp.2, 144 Holsteins steer (112 ± 6 kg) were used in a 305-d trial to evaluate treatment effects on growth performance and carcass characteristics. During the initial 126 d, DDGS substitution increased ADG (linear effect, P = 0.03), G:F (quadratic effect, P = 0.03), and dietary NE (quadratic effect, P = 0.02), maximal for both at 20% DDGS inclusion rate. Based on estimated indispensable AA supply to the small intestine as a percentage of requirements during the initial 126-d period, histidine was first limiting followed by methionine. During the final 179-d period and overall (305-d feeding period), treatment effects on ADG and G:F were small (P ≥ 0.22). Compared with the other treatments, HCW was greater (3.4; P = 0.03) at the 20% level of DDGS substitution. The NE value for DDGS in SF corn-based diets for the calf-fed Holstein are consistent with current tabular standards. Extra-caloric value of DDGS as a metabolizable AA source is apparent during the initial growing phase. The UIP value of DDGS used in this study (35%) was considerably less than current tabular estimates (52%; NRC, 2000).

Two experiments were conducted to evaluate the comparative feeding value of dried shredded sugarbeets (DSSB; 0, 20, and 40% of diet DM) as a replacement for steam-flaked corn (SFC) in finishing diets for feedlot cattle. In Exp. 1, 60 calf-fed Holstein steers (476 ± 6.3 kg) were used in a 97-d finishing trial. Substitution of SFC with DSSB did not affect ADG or DMI (P > 0.20). Increasing DSSB decreased gain efficiency (ADG:DMI; linear effect, P = 0.04) and dietary NE (linear effect, P = 0.03). Given that SFC has a NE(m) value of 2.38 Mcal/kg, the replacement NE(m) and NE(g) values for DSSB were 1.94 and 1.29 Mcal/kg, respectively. There were no treatment effects (P > 0.20) on carcass characteristics. In Exp. 2, 6 cannulated Holstein steers (205 kg) were used in a replicated 3 × 3 Latin square design to evaluate treatment effects on digestion. Ruminal digestion of starch, NDF, and feed N were not affected (P > 0.10) by DSSB, although ruminal OM digestion tended to increase (linear effect, P < 0.08). Replacing SFC with DSSB decreased flow of starch to the small intestine, but it increased flow of microbial N (linear effect, P = 0.05). There were no treatment effects (P > 0.14) on postruminal digestion of OM, NDF, starch, or feed N or total tract digestion of OM, starch, and N. Substitution of DSSB increased (linear effect, P = 0.05) total tract NDF digestion and decreased (linear effect, P = 0.05) dietary DE (Mcal/kg). Given that SFC has a DE value of 4.19 Mcal/kg, the replacement DE value of DSSB was 3.68 Mcal/kg. There were no treatment effects (P > 0.12) on ruminal pH or total VFA; however, DSSB decreased propionate (linear effect, P = 0.05) and increased acetate (linear effect, P = 0.07), butyrate (linear effect, P = 0.05), valerate (linear effect, P = 0.04), and estimated methane production (linear effect, P = 0.05). We concluded that DSSB may replace SFC in finishing diets at levels of up to 40% without detrimental effects on ADG and carcass characteristics. The NE value of DSSB is 82% that of SFC (DM basis). Partial replacement of SFC with DSSB alters ruminal VFA patterns, increasing estimated methane energy loss and slightly decreasing the efficiency of DE utilization.

Jersey cattle are known for producing carcasses with a greater amount of marbling, but they require more days on feed to achieve acceptable market weights compared with other breeds. The objective of this study was to evaluate the effect of dietary forage (12 vs. 24% sudangrass:alfalfa hay, DM basis) in steam-flaked, corn-based finishing diets on carcass characteristics, beef palatability, and retail color stability of steaks from Jersey beef compared with conventionally fed commodity beef strip loins (COM) of identified quality (Choice(-) and Select(+)). Jersey steers (n = 77) were blocked by BW and randomly assigned to 1 of the following treatments for a 383-d trial period: Jersey low 12% (JL; n = 38) or Jersey high 24% (JH; n = 39) forage (DM basis). A comparison group was selected from conventionally fed cattle on the same day of slaughter as the Jersey treatments, and strip loins from USDA Select(+) (COM; n = 20) and Choice(-) (COM; n = 20) were removed for data analysis. Seventy-two hours postmortem, strip loins were removed, vacuum-packaged, and aged at 3°C for 18 d postmortem. After the aging period, steaks from the LM were sliced, vacuum-packaged, and frozen (-20°C) until analyzed. Jersey steaks had reduced (P < 0.05) Warner-Bratzler shear force values compared with COM steaks. Trained sensory panelists rated JL greater (P < 0.05) for initial and sustained tenderness and initial juiciness than COM, whereas JH was intermediate. As expected, marbling was greater (P < 0.05) for both JL and JH compared with COM, and trained sensory panel sustained juiciness, beef flavor intensity, and overall acceptability scores were greater (P < 0.05) for both JL and JH compared with COM; however, no differences (P = 0.14) were reported for consumer tenderness and flavor. Objective color (L*, a*, b*) measurements decreased (P < 0.05) over time across treatments. There were no differences among treatments for lightness (L*); however, overall during retail display JL were less (P < 0.05) red (a*) and yellow (b*) than JH and COM. Subjective color scores indicated both JL and JH were less red (P < 0.05) than COM. Steaks from Jersey were equal to and on some measurements more desirable than steaks from COM carcasses for both color stability and palatability. These results suggest that dietary forage level had minimal effects on carcass characteristics and beef palatability. However, feeding a low-forage diet decreases input cost and potentially results in a greater valued carcass. Finishing long-fed (383 d) Jersey steers can meet beef industry expectations with respect to quality grade.

The primary reason for processing maize is to enhance feeding value. Total tract starch digestion is similar for coarsely processed (dry rolled, cracked) dry maize. Enhancements in starch digestion due to dry rolling maize v. feeding maize whole may be greater in light-weight calves than in yearlings, and when DM intake is restricted ( < 1·5 % of body weight). The net energy (NE) maintain (NEm) and NE gain (NEg) values for whole maize are 8·83 and 6·02 MJ (2·11 and 1·44 Mcal)/kg, respectively. Compared with conventional dry processing (i.e. coarse rolled, cracked), finely processing maize may increase the initial rate of digestion, but does not improve total tract starch digestion. Tempering before rolling (without the addition of steam) may enhance the growth performance response and the NE value of maize. Average total tract starch digestion is similar for high-moisture and steam-flaked maize. However, the proportion of starch digested ruminally is greater (about 8 %) for high-moisture maize. The growth performance response of feedlot cattle to the feeding of high-moisture maize is highly variable. Although the NEm and NEg value of whole high-moisture maize was slightly less than that of dry processed maize (averaging 9·04 and 6·44 MJ (2·16 and 1·54 Mcal)/kg, respectively), grinding or rolling high-moisture maize before ensiling increased (6 %) its NE value. Substituting steam-flaked maize for dry processed maize increases average daily gain (6·3 %) and decreases DM intake (5 %). The comparative NEm and NEg values for steam-flaked maize at optimal processing (density = 0·34 kg/l) are 10·04 and 7·07 MJ (2·40 and 1·69 Mcal)/kg, respectively. These NE values are greater (3 %) than current tabular values (National Research Council, 2000), being more consistent with earlier standards (National Research Council, 1984). When maize is the primary or sole source of starch in the diet, concentration of starch in faeces (faecal starch, % of DM) of feedlot steers can serve as an indicator of total tract starch digestion, and, hence, the feeding value of maize.

Four Holstein steers (137 ± 2 kg) with cannulas in the rumen and proximal duodenum were used in a 4 × 4 Latin square design to evaluate the influence of processing method on comparative digestion of white corn. Treatments consisted of a basal finishing diet containing 80% corn grain (DM basis) as 1) dry-rolled white corn (DRWC), 2) steam-flaked white corn (SFWC) with 0.36 kg/L flake density (SFWC36), 3) SFWC, 0.31 kg/L flake density (SFWC31), and 4) steam-flaked yellow corn (SFYC) with 0.31 kg/L flake density (SFYC31). Characteristics of ruminal, postruminal, and apparent total tract digestion of OM, starch, and N were similar (P ≥ 0.08) for SFYC31 and SFWC31 treatments. Decreasing flake density of white corn (from 0.36 to 0.31 kg/L) did not affect (P = 0.22) ruminal OM digestion, but increased (1.9%, P = 0.07) apparent total tract OM digestion. Compared with dry rolling, steam flaking white corn increased ruminal (9.4%, P = 0.05), postruminal (14.4%, P < 0.01), and apparent total tract OM digestion (8.2%, P < 0.01), reflecting corresponding increases in ruminal (13.3%, P < 0.01), postruminal (43%, P < 0.01), and apparent total tract (12.3%, P < 0.01) starch digestion. Apparent postruminal and apparent total-tract N digestion also were greater (6.5 and 5.6%, respectively, P = 0.04) for SFWC than for DRWC. The DE value of SFWC and SFYC diets was similar, averaging 3.39 Mcal/kg. The DE value of SFWC was greater (8.1%, P < 0.01) than that of DRWC. Ruminal pH (4 h postprandial) averaged 5.74 and was not affected (P ≥ 0.48) by dietary treatments. Compared with dry rolling, steam flaking markedly enhances the feeding value of white corn, with optimal flake density being less than 0.36 kg/L. Although white corn has greater vitreous endosperm content, characteristics of ruminal starch digestion and undegradable intake protein are similar to conventional yellow dent corn when processed to a similar flake density (0.31 kg/L). However, postruminal and apparent total tract starch digestion tends to be slightly less for flaked white corn than for yellow corn.

Ractopamine HCl and zilpaterol HCl, beta-agonists recently approved for use in feedlot cattle to improve performance traits and carcass leanness, were examined for their effects on fecal shedding of Escherichia coli O157:H7 in feedlot cattle. Fecal samples (n = 2,454) were obtained from four experiments (one ractopamine HCl, three zilpaterol HCl) over the course of a 3-year period, either by rectal palpation (ractopamine HCl experiment) or from pen-floor fecal pats. Samples were cultured quantitatively and qualitatively for E. coli O157:H7. No significant treatment differences were detected for fecal prevalence of E. coli O157:H7 in the ractopamine HCl experiment. Zilpaterol HCl feeding had no effect (P > 0.20) on fecal shedding in the first or second experiments, with overall E. coli O157:H7 prevalence relatively low (<7%). In the third zilpaterol HCl experiment, the percentage of fecal samples that were E. coli O157:H7 positive following qualitative culture was higher (P < 0.05) in the zilpaterol HCl treatment (10.3%) than for the control (6.1%). The current research showed minimal effects of beta-agonists on fecal shedding of E. coli O157:H7 and indicated that these compounds (fed immediately prior to slaughter) are not a cause for concern from a food safety standpoint.

Two trials were conducted to evaluate the influence of virginiamycin supplementation on growth performance and digestive function. In trial 1, 144 Holstein steer calves (119 kg of initial BW) were used in a 340-d trial. Treatments were (DM basis) 1) control (no antibiotic); 2) 16 mg/kg of virginiamycin; 3) 22.5 mg/kg of virginiamycin; and 4) 28 mg/kg of monensin. Calves received a steam-flaked corn-based growing diet for the first 112 d and thereafter were fed a finishing diet from d 112 until slaughter. Steers were divided into 2 BW groups (lighter-half and heavier-half), and assigned within groups to 24 pens (6 steers/pen). Virginiamycin did not affect (P > 0.20) ADG, but increased 340-d G:F (linear; P = 0.02) and dietary NE (linear; P = 0.04). Improvements in dietary NE were most pronounced during the final 116 d of the feeding period (linear; P = 0.04) that comprised the hot summer months (June through September). Monensin did not affect (P > 0.20) growth performance or dietary NE. Although average initial BW of the lighter-half and heavier-half BW groups differed by only 4 kg, the heavier BW group had greater HCW (13 kg, P = 0.02), LM area (5.4%, P = 0.01), ADG (4.3%, P = 0.02), G:F (2.3%, P = 0.08), and dietary NE (3.2%. P = 0.01) than the lighter BW group. In trial 2, 4 Holstein steers (269 +/- 3.5 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square design to evaluate treatment effects on digestion. Virginiamycin did not affect (P > 0.20) ruminal digestion of OM, NDF, starch, and N, and microbial efficiency, but tended to linearly increase (P = 0.09) ruminal N efficiency (nonammonia N flow to the small intestine/N intake). Likewise, virginiamycin did not affect (P > 0.20) postruminal or total tract digestion of OM, starch, NDF, and N. Compared with the control diet, monensin depressed total tract digestion of OM (4.2%, P = 0.03) and NDF (29.5%, P = 0.02). There were no treatment effects (P > 0.20) on ruminal pH, or ruminal lactate and total VFA molar concentration. Virginiamycin increased ruminal molar proportion of acetate (quadratic; P = 0.04) and estimated methane production (quadratic; P = 0.07), and decreased propionate molar proportion (quadratic; P = 0.09). Monensin did not affect (P > 0.20) ruminal VFA molar proportions or estimated methane production. We concluded that virginiamycin supplementation can enhance feedlot growth-performance and dietary energetic efficiency of calf-fed Holstein steers.

The objective of these studies was to evaluate the effects of zilpaterol hydrochloride (ZH), fed for 0, 20, or 30 d, on meat quality attributes of calf-fed Holstein steers. Steers were slaughtered at a commercial facility, and carcasses were selected by HCW to represent the pen mean. Further carcass selection was based on quality grade (Choice and Select) and yield grade. Proximate composition, measures of water holding capacity, and tenderness using Warner-Bratzler shear force after 7, 14, or 21 d postmortem were evaluated on the shoulder clod (triceps brachii), top butt (gluteus medius), and strip loin (longissimus lumborum). Percentage of purge for the 3 subprimals was not different (P > 0.05) among ZH treatments. Steers fed ZH for 20 d or 30 d had decreased (P < 0.05) percentages of fat in the triceps brachii, compared with 0-d ZH. Percentage of fat was less (P < 0.05) in the gluteus medius and longissimus lumborum when steers were fed ZH for 30 d compared with those steers fed ZH for 0 d. Percentage of fat was greater in Choice triceps brachii (P < 0.05) and longissimus lumborum (P < 0.10) compared with Select. Thaw loss was not different (P > 0.05) for any muscle due to ZH treatment. Only longissimus had a greater (P < 0.05) cooking loss with ZH treatment. Cooking loss was not different (P > 0.05) for the gluteus medius or longissimus lumborum due to quality grade or aging day. At each aging day, the 20- and 30-d ZH longissimus lumborum had greater (P < 0.05) shear force values than 0 d; however, 20- and 30-d ZH had a greater absolute change in shear force from 7 to 21 d than that of 0 d ZH. Triceps brachii steaks were less tender (P < 0.05) after ZH treatment, but gluteus medius steaks were not different (P > 0.05). There was no difference (P > 0.05) in shear force due to quality grade. Results illustrate the use of ZH in calf-fed Holstein steers will have minimal effects on purge, thaw, or cooking loss. Percentage of intramuscular fat will decrease, especially when fed for longer durations. Steaks from ZH treated steers were tougher than steaks from control animals at all aging times, but ZH steaks became more tender with postmortem aging.

Sixty-four crossbred heifers (451 +/- 23 kg) were used in a 42-d feeding trial (4 pens per treatment in a randomized complete block design) to evaluate the influence of preslaughter zilpaterol hydrochloride withdrawal period on growth performance and carcass characteristics. Heifers were fed a diet based on steam-flaked corn (2.13 Mcal of NE(m)/kg). Treatments were 1) control, no zilpaterol supplementation; 2) zilpaterol supplementation for 30 d, drug withdrawn from the diet 3 d preslaughter (ZIL-3); 3) zilpaterol supplementation for 30 d, drug withdrawn 6 d preslaughter (ZIL-6), and 4) zilpaterol supplementation for 30 d, drug withdrawn 12 d preslaughter (ZIL-12). Zilpaterol was supplemented at the rate of 0.15 mg/kg of BW daily. Intake of DM averaged 9.2 +/- 0.26 kg/d and was not affected (P > or = 0.36) by treatment. Compared with control heifers, ZIL-3 increased (P < 0.01) carcass-adjusted ADG (59%), G:F (57%), apparent dietary NE(m) (31%), and decreased observed/expected DMI (25%). Treatment with ZIL-3 did not affect marbling score (P = 0.49) or backfat thickness (P = 0.17), but compared with the control group, increased HCW (3.6%, P = 0.03), carcass dressing percentage (3.2%, P = 0.02), LM area (6.3%, P = 0.05), and reduced trimmed fat (31%, P = 0.03). Prolonging the period of zilpaterol withdrawal preslaughter tended to decrease carcass-adjusted ADG (linear, P = 0.11), G:F (linear, P = 0.08), apparent dietary NE(m) (linear, P = 0.11), and carcass dressing percentage (linear, P = 0.11). We conclude that growth performance and carcass yield responses to zilpaterol supplementation are negatively affected by prolonging the period of zilpaterol withdrawal beyond 3 d (the required minimum withdrawal period according to label). Drug withdrawal period may be a relevant factor in explaining variation in performance response to zilpaterol supplementation in commercial feedlots.

Performance, DMI, diet composition, and slaughter data from 9,683 pens of steers and 5,009 pens of heifers that were fed high-concentrate diets for 90 d or more were obtained from 15 feedlots from the western United States and Canada. The data set included pen means for more than 3.1 million cattle fed between 1998 and 2004. Performance measurements assessed included ADG, DMI, dietary NE, shrunk initial weight (SIW), and shrunk final weight. Mature final weight (MFW) for cattle in each pen was estimated based on regression of slaughter weight against SIW and ADG across all pens. Equations were developed to standardize performance projections (ADG, MFW, and break-even values) and analyze feedlot cattle close-outs. Generally, as diet NE concentration increased, DMI was decreased but G:F, dressing percentage, and yield grade all increased. Pens of cattle with greater SIW had greater ADG, DMI, and shrunk final weight but a lower G:F and dressing percentage. Dressing percentage and yield grade were correlated positively. Equations of the NRC relating gain to NE intake explained 85 and 80% of the variation in DMI of steers and heifers, respectively, with mean ratios of predicted to observed DMI (DMIratio) at 1.000 +/- 0.0506 and 0.974 +/- 0.0490. However, a significant (P < 0.001) bias in the NRC estimate of DMI was detected (r(2) = 0.10 and 0.05, for steers and heifers) between the DMIratio and ADG in which DMIratio increased as ADG increased. This was due to inherent confounding of ADG and MFW in the original NE equation of Lofgreen and Garrett. Based on iterative optimization to minimize the difference between expected and observed DMI, revised equations for retained energy (RE, Mcal/kg) were developed for steers and for heifers: RE(steer) = 0.0606 x (LW x 478/MFW(steer))(0.75)ADG(0.905); RE(heifer) = 0.0618 x (LW x 478/MFW(heifer))(0.75)ADG(0.905), where LW = mean shrunk live weight. The revised equations decreased the SD of the DMIratio by 5.4% (from 0.0496 to 0.0469) and eliminated the bias in DMIratio that was related to ADG (r(2) = 0.0006). The similarity between the 2 equations derived for steers and for heifers for estimation of RE from ADG supports the concept that scaling by MFW accounts for energy utilization differences between sexes.

Two experiments were conducted to evaluate the influence of dry-rolling (DRS) and tempering agent (TA) addition during the steam-flaking of grain sorghum (SFS) for feedlot cattle. Five dietary treatments were compared: 1) DRS; 2) SFS, no TA; 3) SFS, 0.275 mg/kg of TA; 4) SFS, 1.375 mg/kg of TA; and 5) SFS, 2.750 mg/kg of TA. Bulk densities of DRS and SFS were 0.48 and 0.36 kg/L, respectively. Diets contained 70.6% grain sorghum (DM basis). One hundred fifty crossbred steers (336 kg of BW) were used in a 115-d finishing experiment to evaluate treatment effects on feedlot performance. Body weight gain averaged 1.49 kg/d and was not affected (P = 0.47) by treatments. The SFS reduced (P < 0.01) DMI (9%) and enhanced (P < 0.01) G:F (13%) and the NE(m) and NE(g) value of the diet (9 and 11%, respectively). Use of a TA before flaking sorghum did not influence (P > 0.20) cattle growth performance or NE(m) or NE(g) value of the diet. Given that the NE(m) and NE(g) values of DRS are 2.00 and 1.35 Mcal/kg, respectively (NRC, 1996), the corresponding values for SFS were 2.28 and 1.59 Mcal/kg. Five steers (397 kg of BW) with ruminal and duodenal cannulas were used in a 5 x 5 Latin square design to evaluate treatment effects on digestive function. Ruminal digestion of OM and starch was greater (14 and 16%, respectively; P < 0.01) for SFS vs. DRS. Steam-flaking sorghum increased (P < 0.01) postruminal digestion of OM (11%), N (10%), and starch (25%) and total tract digestion (P < 0.01) of OM (8.3%), N (8.2%), and starch (8.9%). Grain processing did not affect (P > 0.20) ruminal pH or VFA molar proportions. There was a cubic component (P < 0.10) to level of TA on ruminal pH and VFA molar proportions, with values being optimal at 1.375 mg/kg of tempering agent. It is concluded that steam-flaking grain sorghum will increase its NE value for maintenance and gain (14 and 18%, respectively) and enhance the MP value of the diet due to greater intestinal N digestion. The use of a TA to enhance the mechanical efficiency of the flaking process may not otherwise benefit the feeding value of sorghum.

Two trials were conducted to evaluate the interaction of the maceration process and surfactant (Tween 80) supplementation on feeding value of rice straw. Treatments were steam-flaked, corn-based diets containing 14% forage (DM basis), which was 1) Sudangrass hay; 2) ground rice straw; 3) ground rice straw plus 0.22% Tween 80; 4) macerated rice straw; and 5) macerated rice straw plus 0.22% Tween 80. In the maceration process, rice straw was passed through 2 sequentially placed pairs of corrugated rolls set at zero tolerance under a ram pressure of 62,050 millibars, similar to a conventional grain roller mill, except that the opposing rolls operated at different speeds (12 and 14 rpm, respectively). Sudangrass hay and rice straw (native and macerated) were ground through a 2.6-cm screen before incorporation into complete mixed diets. In trial 1, 125 Holstein steers (292 +/- 1.7 kg of BW) were used in a 188-d evaluation of the treatment effects on growth performance and carcass characteristics. In trial 2, 5 Holstein steers (224 +/- 3.5 kg of BW) with cannulas in the rumen and proximal duodenum were used in a 5 x 5 Latin square design to evaluate the treatment effects on digestion. There were no interactions between maceration and surfactant on growth or carcass characteristics. Tween 80 did not influence the feeding value of rice straw. Compared with grinding alone, maceration of rice straw increased the carcass-adjusted ADG (6%, P < 0.10), G:F (6%, P < 0.05), and dietary NE (5%, P < 0.05); DMI was similar across treatments. Assuming NE(m) and NE(g) of Sudangrass hay are 1.18 and 0.62 Mcal/kg, the NE(m) and NE(g) were 0.61 and 0.13 Mcal/kg for ground rice straw and 1.21 and 0.65 Mcal/kg for macerated rice straw. There were no treatment interactions on characteristics of digestion. Tween 80 did not influence ruminal or total tract digestion of OM, starch, NDF, or N. Compared with grinding alone, maceration of rice straw increased ruminal digestion of OM (7.7%, P < 0.10) and NDF (30.8%, P < 0.05), and total tract digestion of OM (2.3%, P < 0.10), NDF (21.1%, P < 0.01), and N (3.7%, P < 0.05). Total tract digestion of OM, NDF, starch, and N for the Sudangrass diet corresponded closely with that of the macerated rice straw diets. Maceration increases the feeding value of rice straw to a level similar to that of good-quality (flag stage of maturity) Sudangrass hay, which is attributable to increased OM and NDF digestion. Effects of surfactant supplementation on growth performance and digestion are not appreciable.

The inclusion of supplemental fats in growing-finishing diets for feedlot cattle also improves diet "condition." Quality factors that may influence the feeding value of fat include the source of fat; moisture, impurities, and unsaponifiables; free fatty acid concentration; degree of saturation or titer; and rancidity (peroxide value). The net energy value of fat declines linearly with an increasing level of supplementation because of constraints on postruminal fatty acid digestion. The authors recommend that receiving diets not contain more than 2% supplemental fat. Little evidence suggests that the feeding value of fat is different for Holsteins than for conventional beef breeds. Fat supplementation is not consistent in its effect on intramuscular fat distribution (marbling), longissimus (rib eye) area, and fat thickness, but can be expected to increase dressing percentage and kidney, pelvic, and heart fat percentage.