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Our objective was to quantify differences in carcass fabrication yield and allometric coefficients of carcass components from implanted and non-implanted steers.

Our objectives were to develop and evaluate a model to induce liver abscesses (LA) in cattle and assess roles of Fusobacteriumand Salmonellaon LA formation and severity.

Liver abscesses in cattle negatively affect production and cause economic losses across the beef cat- tle industry. Recently, a nutritional model has been devel- oped to induce liver abscesses that will provide a method to evaluate the underlying mechanisms driving their de- velopment. The objective of this study was to evaluate gene expression of ileal tissue from calves challenged using the new model.

Rumination and activity of growing feedlot steers were evaluated in response to growth-promoting implant administration, feeding duration, and dietary rough- age.

We investigated incremental growth of carcass and non-carcass components and tissue partitioning of implanted or non-implanted steers.

Our objective was to evaluate tissue residue levels, calculated NH3gas emissions and live and carcass growth in finishing beef steers fed lubabegron (LB).

Our objective was to evaluate growth performance of feedlot steers and heifers administered a sham terminal implant or Synovex Choice, Synovex Plus, or Synovex ONE Feedlot terminal implant 60 or 120 d after initial implantation with Synovex Choice.

We evaluated the effects of growth implant administration upon live growth performance, dimension- al growth, and carcass outcomes of steers across a 378-d feeding duration.

For more than 80 years, liver abscesses have been documented to reduce beef system value. These infections of liver tissue result in poorer growth performance as evidenced by diminished live and carcass weights, leaner and lesser muscled carcasses, and greater rates of trim. Those negative outcomes are compounded by reduced animal and carcass value. As technology advances, methods to reduce and prevent liver abscesses should be a goal of scientists and producers worldwide.

Life Products’ direct fed microbial, 10-G, is a lipid-coated and heat protected mixed culture containing Lactobacillus acidophilus, Enterococcus faecium, Pediococcus pentosaceus, Lactobacillus brevis, and Lactobacillus plantarum. Previous small-pen research has reported inconsistent benefits to performance and carcass characteristics from feeding 10-G. The objective of this trial was to evaluate the effects of feeding 10-G on growth performance and carcass quality in yearling steers. In this randomized complete block design, 6,400 yearling steers were allocated to treatment (10-G or control) within a block (n = 16), where pen served as experiment unit. Trial diets were composed of steam-flaked corn, wheat silage, corn silage, and Sweet Bran Plus. The addition of 10-G within the treatment diet was at an inclusion of 2 g·animal-1·day-1to provide 1x109cfu for approximately 170 days. Mean initial body weight was 358 kg and cattle were on feed for an average of 182 days. No differences (P> 0.10) were observed between treatments for dry matter intake (control: 9.75 vs 10-G: 9.80 kg), final body weight (control: 641vs 10-G: 641 kg), average daily gain (control: 1.55 vs 10-G: 1.55 kg/d), or feed efficiency (control: 2.85 vs 10-G: 2.87). When evaluating carcass characteristics, there were no differences (P> 0.10) for hot carcass weight (control: 415 vs 10-G: 413 kg) or liver abscess prevalence (control: 17.4 vs 10-G: 18.2%). However, dressed carcass yield was decreased (P= 0.05) by 0.17% for cattle fed 10-G (control: 64.51 vs 10-G: 64.34%). No differences (P> 0.10) were observed for marbling score (control: Small29vs 10-G: Small27), ribeye area (control: 100.00 vs 10-G: 100.00 cm2), backfat thickness (control: 1.30 vs 10-G: 1.30 cm). USDA quality grade outcomes. In conclusion, the supplementation of 10-G direct fed microbial did not influence live or carcass performance within this trial.

Liver abscesses (LA) are a polymicrobial infection and the causative agents include two subspecies of Fusobacterium necrophorum, necrophorumand funduliforme, and Trueperella pyogenes. Nucleic acid-based analysis of the purulent material of LA has indicated that Proteobacteriaand Bacteroideteswere the dominant phyla, next to phylum Fusobacteria. The sporadic isolations of bacterial species of the Proteobacteriaand Bacteroidetesin LA have been reported. An aspect of the pathogenesis that has not been investigated is whether bacterial pathogens in LA originate, besides the rumen, from the colon? Therefore, our objectives were to target detection and isolations of Salmonella enterica, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosaand Bacteroides fragilis, in addition to routine isolations of F. necrophorumand T. pyogenes, from LA and also from ruminal and colonic epithelial tissues of the same animals. Liver abscesses, matched with ruminal and colonic epithelial tissue samples from 96 steers and heifers, originating from 15 feedlots, were collected at slaughter, transported to the laboratory and processed within 24 hours. Samples were subjected to anaerobic and aerobic culture methods, including enrichment and selective media for detection and isolation of S. enterica, E. coli, K. pneumonia, P. aeruginosa, and B. fragilis. Prevalence of bacterial species were shown in table 1. For each bacterium, two-sided Fisher's exact test was used to evaluate the association of its prevalence in LA with that in colon and rumen at 0.05 level. Overall, prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenesand S. entericain liver abscesses were 86.4% (83/96), 21.8% (21/96), 35.4% (34/96) and 6.2% (6/96), respectively (Table 1). In ruminal tissue samples, prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenesand S. entericawere 6.6% (6/96), 40.6% (39/96), 11.4% (11/96) and 4.1% (4/96), respectively. Prevalence of subsp. necrophorum, subsp. funduliforme, T. pyogenesand S. entericain colonic tissues were 18.7% (18/96), 36.4% (35/96), 0% (0/96) and 7.2% (7/96), respectively. Prevalence of E. coli, Klebsiellaspp., and P. aeruginosain LA samples were 70.8% (68/96), 92.7% (89/96), and 91.6% (88/96), respectively. Prevalence of E. coli, Klebsiellaspp., and P. aeruginosain rumen epithelial tissue samples were 17.7% (17/96), 50.0%, (48/96), and 15.6% (15/96), respectively. Prevalence of E. coli, Klebsiellaspp., and P. aeruginosain colonic tissue samples were 16.6% (16/96), 24.0% (26/96), and 12.5% (12/96), respectively. Prevalence of subsp. funduliformein ruminal and colonic tissues was greater than subsp. necrophorum. None of the liver abscess samples yielded B. fragilis. In conclusion, E. coliwas the second most dominant species detected and isolated from LA, next only to subsp. necrophorum. The greater frequencies of isolations of subsp. necrophorumand S. entericafrom colonic epithelial than ruminal epithelial tissues suggest that hindgut could also be a source of pathogens involved in LA.

Most research surrounding liver abscesses involves post-hoc evaluation of naturally occurring abscesses in production settings. Few studies have been designed to experimentally induce abscesses with the purpose of identifying a time course, causality, and associated physiological implications. Therefore, we set out to develop a minimally invasive, reliable, and repeatable model to induce liver abscesses in calves in a controlled research environment to elucidate the genesis and etiology of the disease, with the ultimate goal of developing abscess reduction strategies. Experiment 1 was an attempt to induce abscesses by intraruminal inoculation with Fusobacterium necrophorum, Salmonella lubbock, and Truperella pyogenes(FST) following an intravenous lipopolysaccharide challenge. Holstein steers were harvested 3- and 10-d after inoculation, but no abscesses were detected. Experiments 2 and 3 involved diet manipulation by cycling calves on and off a high-starch, acidotic diet followed by intraruminal inoculation of microbes. In Experiment 2, Holstein calves were fed a negative control diet, an acidotic diet, and an acidotic diet plus bacterial inoculation with FST. No abscesses formed in the control or acidotic diet calves, but 43% of calves fed the acidotic diet with FST inoculation formed liver abscesses, suggesting that acidosis alone is insufficient to produce abscesses. In Experiment 3, treatments consisted of Holstein steers fed a negative control, an acidotic diet, an acidotic diet plus ruminal Fusobacterium necrophorum(F), and an acidotic diet plus Fusobacteriumand Salmonella(FS). Again, there were no abscesses in the control or calves fed an acidotic diet alone; however, 40% of calves receiving F presented with an abscess, and 50% of the calves that received FS presented with abscesses. These data suggest that ruminal acidosis in conjunction with a ruminal load of pathogens commonly associated with liver abscesses provides a model that will induce liver abscesses. While the role of barrier dysfunction in the rumen and the lower gastrointestinal tract in formation of abscesses is not fully understood, this work provides a foundation to further explore the etiology of this disease and potential mitigation strategies.

The objective of this study was to develop a model for liver abscesses (LA) in Holstein steers by using an acidotic diet or acidotic diet plus intraruminal inoculation of Fusobacterium necrophorum, Salmonella entericaserotype Lubbock, and Truperella pyogenes. Holstein steers (n = 40; initial BW = 84.9 + 7.1 kg) were individually housed and randomly assigned to either a negative control diet (CON), an acidotic diet (AD), or an acidotic diet plus intraruminal inoculation with the bacterial mixture [ADB; (1 × 109colony forming unit (CFU)/mL of each bacteria]. Steers in AD and ADB were cycled on (3 d) and off (2 d) a high-starch diet 20 days before intraruminal inoculation of ADB. Following inoculation, AD and ADB remained on the acidotic diet for the remainder of the study. Ruminal pH boluses were randomly inserted into 19 steers across treatments to monitor ruminal pH throughout the study. Steers were euthanized and necropsied to record gross pathology on the lung, rumen, liver, and colon. Culture techniques were used to determine the prevalence inoculated bacteria within LA. Quantitative polymerase chain reaction methods were used to quantify F. necrophorumin rumen tissue. Data were analyzed as a completely randomized design with animal as the experimental unit, where an α of ≤ 0.05 determined significance. Liver abscess prevalence was 43% in ADB vs. 0% in AD and CON treatments (P <0.01). Ruminal damage was 51.1% greater in ADB than in AD and 78.6% greater than in CON (P≤ 0.05). There were no pathological differences in the lungs and colons among treatment groups (P≥ 0.14). There was a treatment × time interaction for ruminal pH, where pH decreased below 5.6 in AD and ADB calves during each cycle of the acidotic diet (P <0.01). The ADB contained a greater concentration of F. necrophorumsubsp. Necrophorumand subsp. Fundliforme within rumen tissue (P≤ 0.03). Of the LA cultured, 100% contained F. necrophorum, 50% S. enterica, and 0% contained T. pyogenes. The F. necrophorumsubsp. Necrophorum was phylogenetically typed and identical to the strain (FN-8LI) infused in the bacterial inoculation. These data suggest that acidotic diet in combination with intraruminal inoculation of the bacterial mixture is sufficient to induce liver abscesses and provides insight on possible mechanisms and origins of LA. Further studies are needed to validate these results and determine if this model may be used to study novel intervention methods.

Sexed semen artificial insemination is a breeding technique that allows producers to shorten breeding seasons, optimize genetics through use of superior semen, create calves based on sex preference, and increase profitability. Sexed semen is a technology that sorts semen by differences in DNA content between X (female) and Y (male) bearing sperm. However, sexed semen practices have yet to be widely used in beef cows due to reduced sperm numbers, low conception rates, and increased costs. The objective of this study was to determine the effect of time of estrus upon fixed-time artificial insemination (FTAI) of sex-sorted semen on conception rate using two different estrous synchronization protocols. Multiparous commercial beef cows (n = 73) were randomized by age, body condition score (BCS), and days post-partum at the University of Arkansas Livestock and Forestry Research Station in Batesville. Both synchronization treatments (TRT) used a controlled internal drug releasing device (Eazi-breed CIDR; 1.38g progesterone) inserted intravaginally on d -14 of the protocol simultaneous to administration of prostaglandin F2α (PGF; 500µg cloprostenol sodium; Estrumate). In the first treatment (TRT 1; 7&7 Synch), gonadotropin-releasing hormone (GnRH; 86µg gonadorelin; Fertagyl) was administered on d -7. In the second treatment (TRT 2; 8&6 Synch), GnRH was administered on d -6. Both treatments were then administered PGF simultaneous to CIDR removal on d 0, 66 ± 2h before FTAI and administration of GnRH. Standing heat (estrus) was visually detected every 3 h for 30 min intervals between CIDR removal and FTAI. Heat detection patches were used in conjunction with visual detection of estrus. Time of estrus was signified as time of standing immobile when mounted in combination with presenting a patch score of 4 (>75% color removed). Time of estrus (TD) was deviated from time of FTAI and categorized into three equal time groups (Grp 1 = 0 to 11.0 h; Grp 2 = 11.01 to 22.0 h; and Grp 3 = 22.01 to 33.0 h). Conception rate (CR) was determined via ultrasound 37 ± 2 d after FTAI. Data were analyzed using the GLIMMIX procedure of SAS 9.4. CR did not differ by age of dam (P= 0.58), BCS (P= 0.48), or TRT (P= 0.83). However, TD had an effect on CR (P= 0.002); and resulted in CR of 45% (Grp 1), 87% (Grp 2), and 42% (Grp 3). In conclusion, these results indicate artificially inseminating cows with sexed semen between 11.01 and 22.0 h after time of standing estrus will increase pregnancy rates for multiparous commercial beef cattle.

Holstein steers (n= 40; initial BW = 84.9 ± 7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorumsubsp. necrophorum(9.8 × 108colony forming units [CFU]/mL), Trueperella pyogenes(3.91 × 109CFU/mL), and Salmonella entericaserovar Lubbock (3.07 × 108CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P< 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorumsubsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorumsubsp. necrophorumand Salmonella. The F. necrophorumsubsp. necrophorumwas clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophoruminto the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA.An acidotic diet challenge in conjunction with intraruminal inoculation with F. necrophorum, T. pyogenes, and SalmonellaLubbock were able to induce LA in Holstein steers.Liver abscesses (LA) in feedlots are costly to the beef industry. At harvest, LA cause an increase in liver condemnations, carcass trimming, and a decrease in quality grade. The objective of this research was to develop an experimental LA model in Holstein steers using an acidotic diet with and without intraruminal inoculation of bacteria involved in LA formation. These data suggest acidotic diet challenges in conjunction with bacterial inoculation were able to induce LA in Holstein steers. The acidotic diet alone caused reduced rumen content pH and caused rumen wall inflammation and damage, observed at harvest. Nonetheless, the addition of bacteria had a compounding effect on rumen damage. Both bacteria inoculated were isolated from 57% of LA suggesting they may work in synergy to form LA.

This study evaluated starch dilution with different sources of fiber from terminal implant to harvest on feedlot cattle performance, rumen buffering characteristics, and carcass outcomes. Steers (n = 416) were allocated to 48 pens in a randomized complete block design and assigned to 1 of 4 dietary treatments. Treatments were steam-flaked corn-based diets: CON; 7.5% corn stalks fed for the entire feeding period or CON followed by CS; 14.8% corn stalks, WD; 9.5% wet distillers grains with solubles and 7.5% corn stalks, or NR; 19.0% wet distillers grains with solubles and 0.0% corn stalks fed from terminal implant to harvest. Steers were transitioned to CS, WD, and NR over 6 d using a two-ration system. Within each pen, 2 steers received an indwelling rumen pH bolus and a 3-axis accelerometer ear-tag to quantify rumination. Treatment differences were considered statistically significant when P < 0.10. Dry matter (DM) and metabolizable energy (ME) intake were greatest for cattle consuming CS, intermediate for WD and CON, and least for NR (P <0.01). The average daily gain (ADG) did not differ among treatments (P= 0.18); however, feed efficiency (G:F) was least for NR, intermediate for WD, and greatest for CS and CON (P= 0.10). Steers consuming CS had more (P= 0.08) 12thrib fat than NR, WD, or CON, but no other differences (P≥ 0.24) in carcass characteristics were observed. A treatment × day interaction (P <0.01) was observed for daily rumination time and ruminal pH. Results suggest that increasing the concentration of corn stalks in the diet post-terminal implant increased DM and ME intake and rumination; replacing corn stalks with wet distillers grains with solubles improved G:F and reduced rumination with minimal impacts on ruminal pH.

An experiment was conducted to evaluate the fabrication yields of carcasses from beef steers supplemented zilpaterol hydrochloride (ZH) and fed at maintenance (MA) or ad libitum (AB) intake levels. Beef steers (n= 56) from a common sire were blocked (n= 28 per block) by terminal growth implant and sorted into pairs by BW. Four pairs (n= 8) were harvested on day 0; the remaining 24 pairs (n= 48) were assigned to a dietary intake level (MA or AB) and days on feed (28 or 56 d). Within pairs of MA or AB intakes, steers harvested on day 56 were randomly assigned to supplementation of ZH (90 mg·d−1per steer) for 20 d followed by a withdrawal period of 4 d or control (C). Steers (BW = 603.5 ± 48.1 kg) were harvested at a commercial processing facility. After a 24-h chill period, standard USDA grading procedures were used to derive a calculated yield grade and quality grade. Following grading, left carcass sides were transported to the West Texas A&M University Meat Laboratory for fabrication. Each side was fabricated into subprimals to determine individual red meat yield (RMY), trimmable fat yield (TFY), and bone yield (BY). A mixed model was used for analysis; fixed effects included treatment combinations and random effects included block and pairs. Single df contrasts tested day 0 vs. 28, day 0 vs. 56, day 28 vs. 56, MA vs. AB, and C vs. ZH. Yield of chuck eye roll differed (P= 0.05) by days on feed (0 d = 4.14, 28 d = 4.11, 56 d = 4.55%). Similarly, eye of round yield was impacted (P= 0.02) by days on feed (0 d = 1.51, 28 d = 1.37, 56 d = 1.36%). Additionally, brisket yield was altered (P< 0.01) by days on feed (0 d = 4.08, 28 d = 3.56, 56 d = 3.48%) and treatment (C = 3.34, ZH = 3.61%). For remaining subprimals, no differences (P≥ 0.15) were detected. Furthermore, results indicated that RMY tended (P= 0.07) to differ by treatment (C = 61.35, ZH = 63.67%). Comparatively, TFY was impacted (P= 0.04) by intake (MA = 20.44, AB = 23.33%). Results from this study indicate that a MA intake level during the last 56 d of the finishing period concurrent with ZH supplementation impacts subprimal yields as well as carcass RMY and TFY of beef steers.

Crossbred beef bulls (n= 180) were blocked by initial BW (337 ± 10.9 kg; six blocks) and assigned randomly to one of three treatments on day 0: 1) INJ; received 1 mL (100 mg Zn) of a Zn solution in each testis, 2) BAN; received blood- restrictive rubber band placed around the dorsal aspect of the scrotum, 3) BUL; bulls with testicles remaining intact in a randomized complete block design (three treatment pens per block and 10 cattle per pen). A subset of 54 animals (n= 3 per pen) was fitted with accelerometers on day 0 to quantify behavior variables continuously for 28 d. Testis width and scrotal circumference, and serum haptoglobin (days 0, 1, 3, 5, 7, and 14) and testosterone concentrations (every 28 d until slaughter) were also determined for the subset. During the slaughter process, testes from INJ and BUL were collected to assess final testes weight and for histopathological evaluation. Data were analyzed using a mixed model (α = 0.05); pen served as the experimental unit for all dependent variables. Final BW was greater (P< 0.01) for INJ and BUL compared to BAN (672, 686, and 611 kg, respectively; SEM = 4.4). Overall ADG and G:F were greater (P≤ 0.03) in INJ and BUL than BAN; whereas, DMI was similar between treatments for the study duration (P= 0.46). Histopathological evaluation (n= 13; INJ = 7; BUL = 6) indicated that INJ testes were degenerative and reproductively nonviable whereas BUL testes were normal. Serum testosterone concentrations on day 168 were similar (P= 0.14) between INJ and BUL whereas after day 14, BAN was nondetectable; however, initial serum testosterone concentrations were similarly low across treatments. Serum haptoglobin concentration was greater (P< 0.01) in INJ than BUL and BAN on days 1, 3, 5, and 7. Scrotal circumference (P= 0.08) and testis width (P= 0.07) on day 168 tended to be greater for BUL than INJ. Motion index (P≤ 0.02) and step count (P= 0.04) was greater in BUL and INJ compared to BAN cattle during the 28 d monitoring period. No difference in standing time (P≥ 0.85) or lying bouts (P= 0.35) occurred. Zinc injection resulted in sterilization but did not cause complete cessation of testicular function evidenced by testosterone concentrations more similar to BUL than BAN. This resulted in overall increased BW and G:F for INJ vs. BAN, yet the acute phase response was markedly greater directly after Zn injection. Collectively, Zn injection resulted in outcomes more similar to BUL than BAN, implying minimal efficacy of INJ as a castration method in older bulls arriving to the feedlot.

Holstein steers (n= 40; initial body weight [BW] = 96.0 ± 10.5 kg) were individually housed in a climate-controlled barn to evaluate potential models for the genesis of liver abscesses (LA). In this 2 × 2 factorial, steers were balanced by BW and randomly assigned to one of two treatments: 1) intravenous saline injection followed by intraruminal bacterial inoculation with Fusobacterium necrophorumsubsp. necrophorum(1 × 109colony forming unit [CFU]/mL) and Salmonella entericaserovar Lubbock (1 × 106CFU/mL; CON; n= 20 steers); or 2) intravenous injection with 0.25 µg/kg BW of lipopolysaccharide (LPS; Escherichia coliO111:B4) followed by intraruminal bacterial inoculation of F. necrophorumsubsp. necrophorum(1 × 109CFU/mL) and S. entericaserovar Lubbock (1 × 106CFU/mL; LBI; n= 20 steers) and 1 of 2 harvest dates (3 or 10 d post LPS infusion). Body weights were recorded on days −4, −1, 3, and 10, and blood was collected for hematology on days −4, 3, and 10, relative to LPS infusion on day 0. Intraruminal bacterial inoculation occurred on day 1. Steers from each treatment group were harvested at two different time points on day 3 or 10 to perform gross pathological examination of the lung, rumen, liver, LA (if present), and colon. Feed disappearance was less for LBI than CON (P< 0.01); however, BW did not differ (P= 0.33) between treatments. Neither treatment nor time differed for hematology (P≥ 0.13), and no gross pathological differences were noted in the lung, liver, LA, or colon (P≥ 0.25). A treatment × harvest date interaction was noted for ruminal pathology in which LBI had an increased percentage of abnormal rumen scores on day 3 (P< 0.01). These results suggest that an LPS challenge in combination with intraruminal bacterial inoculation of pathogens commonly isolated from LA was not sufficient to induce LA in steers within 3 or 10 d (P= 0.95) when compared to CON. Further evaluation is needed to produce a viable model to investigate the genesis and prevention of LA in cattle.Lipopolysaccharide in combination with intraruminal bacterial inoculation of Fusobacterium necrophorumand Salmonella entericais not a viable model to induce liver abscesses in steers within 10 d. Bacterial inoculation alone was insufficient at inducing liver abscesses, and further research to determine the time necessary to induce liver abscesses is needed.Liver abscesses in feedlot cattle can cause a decrease in feed intake, average daily gain, feed efficiency, and hot carcass weight. At harvest, liver abscesses result in liver condemnations, carcass trimming, and a potential decrease in quality grade, with an estimated economic cost to packers of $41.6 million annually. Our objective was to evaluate an intravenous endotoxin challenge followed by intraruminal inoculation of bacteria commonly isolated from liver abscesses over a 10-d period as a potential model to understand the genesis and etiology of liver abscesses in cattle and evaluate possible preventative interventions. Results suggest that an endotoxin challenge in combination with intraruminal bacterial inoculation is not a viable model to induce liver abscesses in steers, and bacterial inoculation alone was insufficient to induce liver abscesses. The length of time necessary to induce liver abscesses is also unknown. Based on our results, more research is needed to develop a noninvasive model to induce liver abscesses in cattle.

Calf-fed Holstein steers (n= 115; 449 ± 20 kg) were utilized in a serial harvest experiment. A baseline group of five steers was harvested after 226 d on feed (DOF), which was designated day 0. The remaining cattle were assigned randomly to 11 harvest groups, with slaughter every 28 d. Cattle were either not (CON) or were fed zilpaterol hydrochloride for 20 d followed by a 3 d withdrawal (ZH). There were five steers per treatment in each slaughter group ranging from days 28 to 308. Whole carcasses were divided into lean, bone, internal cavity, hide, and fat trim components. Apparent mineral retention (Ca, P, Mg, K, and S) within the body was calculated as the difference between mineral concentration at slaughter and day 0. Mineral concentration at day 0 was determined from body composition of steers harvested at day 0 multiplied by individual live body weight (BW) at day 0. All data were analyzed as a 2 × 11 factorial arrangement with individual animal as the experimental unit. Orthogonal contrasts were used to analyze linear and quadratic contrasts over time (11 slaughter dates). There were no differences in concentration of Ca, P, and Mg in bone tissue as feeding duration increased (P≥ 0.89); concentration of K, Mg, and S in lean tissue did fluctuate across DOF (P< 0.01). Averaged across treatment and DOF, 99% of Ca, 92% of P, 78% of Mg, and 23% of S present in the body were in bone tissue; 67% of K and 49% of S were in lean tissue. Expressed as gram per day, apparent retention of all minerals decreased linearly across DOF (P< 0.01). Expressed relative to empty body weight (EBW) gain, apparent Ca, P, and K retention decreased linearly as BW increased (P< 0.01) whereas Mg and S increased linearly (P< 0.01). Apparent retention of Ca was greater for CON cattle (greater bone fraction) and apparent retention of K was greater for ZH cattle (greater muscle fraction) when expressed relative to EBW gain (P≤ 0.02), demonstrating the increase in lean gain by ZH cattle. There were no differences in apparent retention of Ca, P, Mg, K, or S due to treatment (P≥ 0.14) or time (P≥ 0.11) when expressed relative to protein gain. Apparent retention averaged 14.4 g Ca, 7.5 g P, 0.45 g Mg, 1.3 g K, and 1.0 g S/100 g protein gain. Expressing apparent mineral retention on a protein gain basis minimized effects of rate and type of gain, allowing for better comparison across treatments and time. Feeding zilpaterol hydrochloride did not affect apparent mineral retention when expressed relative to protein gain.This research measured concentration of Ca, P, Mg, K, and S in the body of Holstein steers across a 308-d feeding duration, relative to a control group harvested on day 0. Previously established feedlot cattle requirements for these minerals are primarily based on serial harvest data from the 1940s.Mineral requirements for feedlot cattle are largely based on measured mineral concentration in the body at harvest. Fairly extensive research has been done quantifying Ca and P in the body of cattle, but data on Mg, K, and S are sparse. Serial harvest experiments are expensive and labor intensive and therefore not conducted frequently. A group of 115 Holstein steers was fed a finishing diet with serial harvest every 28 d. Two treatments were evaluated, control and cattle fed zilpaterol hydrochloride to increase lean tissue growth. Every 28 d, five steers from each treatment group were harvested with the whole carcass divided into lean, bone, internal cavity, hide, and fat trim components. Apparent mineral retention was calculated as the difference between mineral composition at day 0 (baseline harvest group) and each 28 d harvest group. Averaged across treatment and days on feed, 99% of Ca, 92% of P, 78% of Mg, and 23% of S present in the body were measured in bone tissue; 67% of K and 49% of S were in lean tissue. Apparent retention averaged 14.4 g Ca, 7.5 g P, 0.45 g Mg, 1.3 g K, and 1.0 g S/100 g protein gain.

Sixty-eight (68) crossbred steers were evaluated using two real-time, B-mode ultrasound units to estimate final carcass attributes. The cattle were ultrasounded at the West Texas A&M research feedlot (Canyon, Texas) and carcass data was collected at the West Texas A&M Meats Laboratory (Canyon, Texas) or Tyson Fresh Meats (Amarillo, Texas). Objectives of the study were 1) to compare ultrasound live animal data to carcass attributes at harvest 2) to evaluate the performance differences between the ALOKA 500 (ALK) and the EVO ultrasound units All ultrasound images were captured by the same Ultrasound Guidelines Council (UGC) certified technician with images being processed at the UltraInsights Laboratory (Pierce, Colorado). The correlations between 12thrib fat thickness of the carcass (FTC) and ultrasound (FTU) were 0.84 for the ALK and 0.85 for the EVO, with no differences being found between the two units (P = 0.15). Correlations between the 12-13thrib carcass ribeye area (REAC) and ultrasound ribeye area (REAU) were 0.69 for the ALK and 0.66 for the EVO. There was no difference in REAU size between the two units. Carcass marbling score (MS) and ultrasound intramuscular fat (IMFU) correlations were 0.78 for the ALK and 0.84 for the EVO. The IMF data were found to be different between the two units, with the EVO measuring a mean IMFU value of 6.03 and the ALK a value of 5.26 with the change of 0.77 being different (P < 0.01). It is concluded that both ultrasound units performed favorably when predicting FTC and marbling score but were not highly correlated for REAU. It was found that the predictions between the two units on FT and REA were the same, though the EVO was higher on both. The IMFU values between the ALK and EVO were different, with the EVO again predicting higher values.

Bovine liver abscess outcomes of individual animals (n = 989,296) were observed from 2013 to 2021 on a pen (n = 6,420) basis to quantify liver abscess prevalence and severity, as well as other liver abnormalities such as liver flukes. Cattle originated from 122 feedlots located in Arizona, Colorado, Idaho, Kansas, Minnesota, Missouri, Nebraska, Oklahoma, and Texas. Livers were audited at eighteen different beef abattoirs. Observational categories included sex (heifer, steer), cattle type (Holstein, beef-type), and pen count. Pen counts were grouped (< 40, 41–80, 81–160, 161–320, and >320) to quantify the association of pen size on liver abscess outcomes. Data were analyzed as a series of binomial proportions using generalized linear mixed models with fixed effects of observational categories (cattle type, feedyard location, pen size and sex). Cattle fed in Oklahoma or Texas exhibited greater (P < 0.01) frequency of liver flukes (3.2% vs 0.5%) than cattle fed in Colorado or Nebraska. Cattle fed in Colorado, Kansas, Missouri, Nebraska, Arizona, and Oklahoma exhibited fewer (P < 0.01) total abscesses (23.5%, 26.0%, 23.6%, 19.3%, 16.9%, and 18.1%) than cattle fed in Idaho, Minnesota, and Texas (36.4%, 36.4%, and 33.2%). Beef-type cattle were observed to exhibit fewer (P < 0.01) total abscesses (22.0% vs 41.1%) and fewer (P < 0.01) severe abscesses (10.2% vs 26.4%) than Holstein cattle. Likewise, native heifers exhibited fewer (P < 0.01) total abscesses (20.6% vs 23.3%) and fewer (P < 0.01) severe abscesses (9.3% vs 11.1%) than native steers. Abscess prevalence differed as a function of pen size. Both total abscess and severe abscess rates decreased (P < 0.01) as animal count within a pen increased (32.66%, 27.47%, 27.86%, 23.17%, and 20.33%; 17.20%, 14.48%, 14.80%, 11.45%, and 9.14%). These results suggest liver abscess prevalence and severity is affected by a wide range of factors.

This study evaluated the effects of a single slow-release implant compared to two re-implant programs administered at either 120 days on feed (DOF) or 80 days from harvest on performance, carcass characteristics, and activity of serially harvested feedlot cattle. Using a randomized complete block design, steers (n = 4,680) were randomly assigned to 72 pens and 1 of 12 treatments in a 3 × 4 factorial arrangement. Treatments were either a slow-release implant (SR), an initial slow-release implant followed by re-implant at 120 DOF (SR+RI-120), or an initial slow-release implant followed by re-implant 80 days from harvest (SR+RI-80) administered to cattle harvested at 166, 180, 194, or 208 DOF. A 3-axis accelerometer ear-tag was used in a subset (n =1,080) of animals to quantify rumination time and activity. No interactions (P ≥ 0.09) were observed for implant × DOF. Implant did not affect (P ≥ 0.25) final BW, ADG, or DMI, but re-implanted steers had a greater (P < 0.01) G:F ratio than SR. Re-implanted steers also had greater (P ≤ 0.03) HCW, dressed yield, and ribeye area, but less (P < 0.01) backfat, marbling, and empty body fat (EBF) compared to SR. Re-implanted steers had less (P < 0.01) choice and yield grade 4 and 5 carcasses than SR steers. As DOF increased, HCW, dressed yield, backfat, marbling, and EBF increased linearly (P < 0.01). The percentage of choice and yield grade 4 and 5 carcasses also increased (P < 0.01) linearly with additional DOF. An implant × day effect (P < 0.01) for weekly activity minutes suggests re-implanted steers had greater activity after re-implant administration. Re-implanting within the payout period of a slow-release implant increases feed efficiency, HCW, dressed yield, and activity minutes, but decreases carcass fatness and reduces quality grade regardless of timing of secondary implant administration.

Cattle diet, marbling and wet aging can affect eating quality and consumer preference of beef. The objective of this study was to assess the relationship of cooked volatile compounds and consumer sensory traits of New Zealand grass-fed strip loin steaks in comparison to US grain-fed strip loin steaks from five different USDA quality grades, wet-aged for 7, 21 and 42 days. Beef strip loins (n = 200; 20 per USDA quality grade/fed cattle type) representing five USDA quality grades (USDA Prime, Top Choice, Low Choice, Select and Standard) and two fed cattle types (New Zealand grass-finished and US grain-finished) were used. Steaks were cooked to a target internal temperature of 71°C and served to consumer panelists (n = 600; 120 per five different cities in the US). Volatile analysis (n = 600) was performed on cooked samples, and quantitation was conducted by an internal standard calibration with authentic standards. Statistical analyses were conducted using the FACTOR procedure of SAS. A principle component analysis (PCA) showed relationships of volatile compounds, treatments, and consumer ratings. PC1 explained 17.17% of the variation and PC2 explained 10.96% of the variation. Consumer flavor liking was most closely associated with ethanol and treatments grass and grain Prime aged 42d. The majority of the alcohols and n-aldehydes were associated with the 7d grain treatments including grain Top Choice, Low Choice and Select. The Maillard derived compounds were grouped together and most associated with grass Top Choice 42d and the consumer attributes. Methional was closest to many grass treatments including grass Top Choice 7d, Low Choice 7d, Standard 7d, Prime 7d and Standard 21d. Although associations were evident between volatile compounds and consumer sensory attributes, they were not strongly related.

Heifers (n = 1,394; 291 ± 9.9 kg) were used to test the effects of a direct-fed microbial (10-G) on live growth performance and carcass characteristics. Heifers were blocked by arrival day and randomly allocated to treatment (0 or 2g/animal/d; CON and 10-G, respectively) in a randomized complete block design with ten pens per treatment. Heifers were fed for an average of 192 days. Growth and carcass outcomes were analyzed using mixed models with pen as experimental unit and block as random effect. Dry matter intake (P = 0.63), average daily gain (P = 0.69), gain:feed (P = 0.95) and final body weight (P = 0.79) did not differ between treatments. Neither deads and removals (P = 0.52) nor first or second treatment morbidity rates (P ≥ 0.84) were different between treatments. Hot carcass weight (P = 0.19), dressed carcass yield (P = 0.33), 12thrib fat depth (P = 0.73), ribeye area (P = 0.13), calculated empty body fat (P = 0.71) or marbling score (P = 0.20) were not different between treatments. Yield grade distributions did not differ between treatments (P ≥ 0.44), however cattle fed 10-G tended (P = 0.09; 15.78 vs 20.34%) to be represented by fewer USDA Select carcasses. Livers from cattle fed 10-G tended (P = 0.10; 1.02 vs 2.19%) to have a lower frequency of abscesses when compared to CON. Heifers fed 10-G also had fewer (P < 0.05; 5.27 vs 8.51%) severe liver abscesses. These results suggest that supplementing fed beef heifers with 10-G decreased rates of severe liver abscesses without altering live animal performance or carcass characteristics.