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California Leafy Green Products Handler Marketing Agreement (LGMA) established food safety metrics with guidance recommendations of 366 m (1,200 feet) and 1,609 m (1 mile) distances between production fields of leafy greens and a concentrated animal feeding operation (CAFO) containing >1,000 and >80,000 head of cattle, respectively. This study evaluated the effect of these distance metrics and environmental factors on the occurrence of airborneEscherichia coliin proximity to seven commercial beef cattle feedlots located in Imperial Valley, California. A total of 168 air samples were collected from seven beef cattle feedlots during March and April 2020, which were the months implicated in the 2018 Yuma Arizona lettuce outbreak of E. coli O157:H7. The distance between air sampling sites and the edge of the feedlot ranged from ∼0 to ∼2,200 m (∼1.3 mile), with each sample comprised of 1,000 L of processed air taken at a 1.2 m elevation over a 10-minute duration. E. colicolonies were enumerated on CHROMagar ECC selective agar and confirmed with conventional PCR. Meteorological data (air temperature, wind speed, wind direction, relative humidity) were collectedin situ. The prevalence and mean concentration ofE. coliwere 6.55% (11/168) and 0.09 CFU per 1,000 L of air, with positive samples limited to within 37 m (120 ft) of the feedlot.Based on logistic regression, the odds of airborne E. coli detection were associated with little to no wind and close proximity to a feedlot. This pilot study found limited dispersal of airborne E. coli in proximity to commercial feedlots in Imperial Valley, with light-to-no wind and proximity within 37 m of a feedlot significant factor-associated airborne E. coli in this produce-growing region of California.

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.

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.

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.

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 (NEm) and gain (NEg) 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 NEm and NEg, 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 NEm value assigned for YG (5.60 Mcal NEm/kg; NASEM, 2016. Nutrient requirements of beef cattle. 8th ed. Washington (DC): National Academy Press.).

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.

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.

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 objective of the current study was to investigate the effects of supplemental rumen-protected lysine and methionine (SMART) and ractopaminehydrochloride (RAC) on cattle growth performance and carcass characteristics of finishing calf-fed Holstein steers. Calf-fed Holstein steer calves [n = 96; body weight (BW) = 466 ± 29 kg] were used to evaluate the interaction of ractopamine and supplemental methionine and lysine on growth performance and carcass characteristics. Steers were blocked by initial off-truck BW and assigned within BW grouping to 16 pens (6 steers/pen). From d 1 to 67, all steers received the basal steam-flaked corn-based finishing diet. From d 68 to harvest (d 103), steers received experimental diets consisting of two levels of RAC (0 vs. 300 mg/hd/d; Optaflexx, Elanco US, Inc., Greenfield, IN) and two levels of supplemental SMART (0 vs. 0.67% DM basis, Smartamine ML Adisseo, Alpharetta, GA). There was an interaction (P = 0.04) between RAC and SMART supplementation, where cattle fed the combination of both supplements had an increase in dry matter intake (DMI) compared with cattle fed either RAC or SMART. However, there was no interaction (P ≥ 0.17) of treatments in other growth performance or carcass characteristic variables evaluated in the study. Carcass adjusted average daily gain (ADG) and energy efficiency of the diet increased (P ≤ 0.02) on cattle supplemented with SMART. Moreover, carcass-adjusted final BW and feed efficiency, as well as energy efficiency, increased (P ≤ 0.05) on cattle supplemented with RAC. However, neither SMART nor RAC supplementation affected (P ≥ 0.13) cattle DMI. Both SMART and RAC supplementation increased (P ≤ 0.03) carcass weight, with no effect (P ≥ 0.17) in other carcass characteristics. In conclusion, both SMART and RAC supplementation enhances cattle growth performance with no detrimental effects on carcass characteristics of calf-fed Holstein steers. [ABSTRACT FROM AUTHOR]

Objective of the current study was to evaluate the effects of tannin supplementation on cattle growth performance, energetic efficiency, and carcass characteristics of calf-fed steers. One hundred and sixty dairy steer calves with initial body weight (IBW) of 129.85 ± 3 kg, were blocked by IBW and randomly assigned to 40 pens (4 steers/pen; 10 pens per dietary treatment). Dietary treatments were: 1) Control (no additives); 2) MON (30 mg/kg monensin); 3) TAN (15 g/kg ByPRO; 70% condensed tannin; Silvateam USA, Tontitown, AR); and 4) MON+TAN (30 mg/kg monensin + 15 g/kg ByPRO). All steers were fed a similar steam-flaked corn-based diet (63.5% steam-flaked corn, 12.0% hay, 17.5% of dry distillers grains with solubles, 4.0% cane molasses, and 3.0% vitamin/mineral supplement). All cattle were slaughtered after 328 days of feed. There were no effects (P = 0.13) of dietary treatment on final BW (615 ± 22 kg), overall average daily gain (1.48 ± 0.07 kg/day), overall dry matter intake (7.93 ± 0.39 kg/day), overall gain to feed ratio (0.187 ± 0.07), and overall observed vs. expected net energy for maintenance and gain (1.00 ± 0.03 and 1.00 ± 0.04, respectively). However, cattle receiving MON or MON+TAN supplementation increased (P = 0.04) BW and gain to feed ratio in the first 112 days on feed compared with cattle in the control treatment. Moreover, cattle in the 2 dietary treatments receiving monensin supplementation tended (P = 0.09) to increase average daily gain and gain to feed ratio on the first 112 days on feed compared with cattle in the control treatment. There were no effects (P = 0.22) of feed additive supplementation on hot carcass weight (380.7 ± 14.7 kg), dressing percentage (61.83 ± 1.05%), kidney, pelvic, and heart fat (3.32 ± 0.19%), backfat thickness (0.73 ± 0.12 cm), longissimus muscle area (83 ± 4.83 cm2), marbling score (494 ± 48), and calculated yield grade (2.94 ± 0.24). Moreover, there were no effects (P = 0.55) of dietary treatment on percent of liver abscess incidence, regardless of diet, calf-fed steers in the current study had 3.75% of liver with abscess. [ABSTRACT FROM AUTHOR]

Objective of the current study was to evaluate the effects of cattle breed (Holstein vs Angus × Holstein) on growth performance, energetic efficiency, and carcass characteristics of calf-fed steers. Eighty Holstein (HOL), initial body weight (IBW) of 128.7 ± 3 kg, and 80 Angus × Holstein cross (CROS) with IBW of 127.1 ± 3 kg, were blocked by IBW and randomly assigned to 40 pens (4 steers/pen; 20 pens per breed). All steers were fed a similar steam-flaked corn-based diet (63.5% steam-flaked corn, 12.0% hay, 17.5% of dry distillers grains with solubles, 4.0% cane molasses, and 3.0% vitamin/mineral supplement). All cattle were slaughtered after 328 days of feeding. There was no effect (P = 0.13) of cattle breed on final body weight (615 ± 22 kg) and overall average daily gain (1.48 ± 0.07 kg/day). However, calf-fed HOL steers had greater (P = 0.04) overall dry matter intake compared with calf-fed CROS steers (8.06 vs. 7.79 ± 0.39 kg/day; respectively). Therefore, calf fed CROS steers had greater (P = 0.01) grain to feed ratio compared with calf-fed HOL steers (0.192 vs. 0.182 ± 0.005; respectively). Moreover, calffed CROS steers had greater (P < 0.01) utilization of dietary net energy for maintenance (2.29 vs. 2.29 ± 0.06 Mcal/kg; respectively) and gain (1.51 vs 1.61 ± 0.06 Mcal/kg; respectively) compared with calf-fed HOL steers. Calf-fed CROS steers had greater (P = 0.02) hot carcass weight (HCW; 386.3 vs. 375.2 ± 14.7 kg; respectively), dressing percentage (DP; 62.3 vs. 61.4 ± 1.05%; respectively), longissimus muscle area (LMA; 86.9 vs. 79.1 ± 4.83 cm2; respectively), backfat thickness (0.89 vs. 0.55 ± 0.12; respectively), and marbling score (538 vs. 449 ± 48; respectively). However, there was no effect (P = 0.26) of cattle breed on calculated USDA yield grade (2.94 ± 0.24). Moreover, there was no effect (P = 0.39) of cattle breed on incidence of liver abscesses. Therefore, cross breeding calf-fed Angus × Holstein increased HCW, DP, LMA, and marbling compared with purebred calf-fed Holstein steers. Moreover, regardless of cattle breed, calf-fed steers in the current study had only 3.75% of liver with abscess. [ABSTRACT FROM AUTHOR]

Objectives were to evaluate the relationship between pen mud accumulation and growth performance of calf-fed Holstein steers during the extreme heat characteristic of the months of August and September in the Southern California desert region. Holstein steers (n = 105; initial BW = 443 ±17 kg) were utilized in 28-d experiment (August 17 - September 14, 2021). Steers were blocked by initial shrunk weight (220 d before the initiation of the experiment) and randomly assigned to 21 pens (5 steers per pen). Pens were 62 m2 with 25 m2 overhead shade, automatic waterers and 2.4 m fence-line feed bunks. All steers were fed a steam-flaked corn-based growing-finishing diet. A bolus measuring temperature activity (smaXtec Basic, Smaxtec Animal Care GmbH, Austria) was placed in the rumen of each steer 55 d before the initiation of the experiment (June 22, 2021). Mud scores were recorded weekly by visual inspection. Mud score was determined as the percentage of pens surface area covered with mud. Scores were determined as follows: 1 - 0 to 20% of pen covered by mud; 2 - 21 to 40% of pen covered by mud; 3 - 41 to 60% of pen covered by mud; 4 - 61 to 80% of pen covered by mud; 5 - 81 to 100% of pen covered by mud. Ambient temperature averaged 33.2 ±2.3° C for the experimental period. Temperature of dry pen surfaces was greater than that of muddy surfaces (50.3 vs 20.4° C, respectively, P < 0.01). The relationship between ruminal temperature and pen mud score was not appreciable (P = 0.56). However, ADG was greater with a pen mud score of 2. Average daily gain decreased as pen mud score increased (r2 = 0.55). Similarly, feed efficiency was greatest in pens with a pen mud score of 2. Greater pen mud scores resulted in decreased feed efficiency (r2 = 0.56). [ABSTRACT FROM AUTHOR]

Objectives were to evaluate the relationships between ambient temperature (AT) and respiration rate (RR) and ruminal temperature (RT) of calf-fed Holstein steers during the extreme heat characteristic of the months of August and September in the Southern California desert region. Holstein steers (n = 21; one steer per pen; initial BW = 422 ±15 kg) were utilized in 28-d experiment (August 17 - September 14, 2021). Steers were blocked by initial shrunk weight (220 d before the initiation of the experiment) and randomly assigned to 21 pens (5 steers per pen). Pens were 62 m2 with 25 m2 overhead shade, automatic waterers and 2.4 m fence-line feed bunks. All steers were fed a steam-flaked corn-based growing-finishing diet. A bolus measuring temperature activity (smaXtec Basic, Smaxtec Animal Care GmbH, Austria) was placed in the rumen of each steer 55 d before the initiation of the experiment (June 22, 2021). During the experimental period, the respiration rate of one calf per pen was collected weekly. Respiration rate was obtained at 1100 h by counting the number of flank movements per minute. Ambient temperature at 1100 h averaged 37.6 ± 2.3° C for the experimental period. Temperature-humidity-index (THI) at 1100 h averaged 83.5 ± 1.7 (steers experienced "danger" or "emergency" THI categories through the entire 28 d trial). As AT increased from the minimum of 22.9° C to a maximum of 39.8° C, RR increased from 58.6 ± 12.9 breaths/min to 103.9 ± 16.9 breaths/min (RR = -54.9 + 4.13 AT, P < 0.01, r2 = 0.65). Likewise, RR increased with increasing RT (RR = -1259 + 33.7 RT, P < 0.01, r2 = 0.92) as RT increased. As ambient temperature increased, ruminal temperature increased (RT = 35.9 + 0.117 AT, P< 0.01, r2 = 0.65), though never exceeding 40.6° C. [ABSTRACT FROM AUTHOR]

Objectives were to evaluate the influence of ENDOVACBeef ® (Endovac Animal Health, Columbia, MO) vaccination on calf-fed Holstein steer growth performance, dietary energetics, and carcass characteristics. Fifty Holstein steer calves were utilized in a 322 d trial. Calves were blocked by initial shrunk body weight (134 ±5 kg) and randomly assigned to treatments within weight groups to 10 pens (5 steers per pen, 5 pens per treatment). Five pen groups received the ENDOVAC-Beef vaccination on d 28 and d 56, and the remaining 5 pens did not receive the ENDOVACBeef vaccination. All steers were fed the same steamflaked corn-based growing-finishing diet. Vaccination did not affect (P = 0.10) live weight, average daily gain, and dry matter intake during the 322 d feeding period. However, vaccination increased (P = 0.04) gain efficiency and estimated dietary net energy values (NE) during the first 112 d on feed. Vaccination did not affect (P = 0.14) gain efficiency or estimated dietary NE during the final 112 to 322 d, or over the entire feeding period (1 to 322 d). Vaccination did not affect (P = 0.31) hot carcass weight, dressing percentage, and marbling score. However, vaccinating calf-fed Holstein steers with ENDOVAC-Beef increased (P = 0.01) longissimus muscle area (LMA; 86.5 vs 76.8 cm2) and retail yield (51.3 vs 50.4); but, tended to increase (P = 0.07) carcass fat thickness. Morbidity and pink eye infection were low and not affect by treatment (P = 0.18). We conclude that while vaccinating calf-fed Holstein steers with ENDOVAC-Beef did not have an overall effect on growth-performance, it increased (13%) LMA and retail carcass yield (1.8%). [ABSTRACT FROM AUTHOR]

Objectives were to evaluate the relationship between ruminal temperature and average daily gain of calffed Holstein steers during the extreme summer months characteristic of the Southern California desert region. Thirty-eight calf-fed Holstein steers (395 ±25 kg) were utilized in the 84-d experiment (June 30 - September 20, 2020). Steers were blocked by initial shrunk weight (168 d before the initiation of the experiment) and randomly assigned to 38 pens with 4 other steers (5 steers per pen). Pens were 62 m2 with 25 m2 overhead shade, automatic waterers and 2.4 m fence-line feed bunks. All steers were fed a steam-flaked corn-based growingfinishing diet. A bolus measuring temperature and activity at ten-minute intervals (smaXtec Basic, SmaXtec Animal Care GmbH, Austria) was placed in the rumen of each steer 112 d before the initiation of the experiment (March 10, 2020). Air temperature for the trial averaged 34.90 ± 3.03°C (maximum = 43.8 ± 2.97° C; minimum 24.72 ± 4.00°C). Average temperature-humidity-index (THI) was 80.1 ±5.4. Maximum THI during the 84-d period averaged 89.29 ± 7.85 (steers experience "emergency" THI category for all 84 days of the trial). Maximum (RTmax) and mean (RTm) daily ruminal temperature averaged 40.93 ±0.24 and 40.21 ±0.23°C, respectively. Average daily gain (mean = 1.18 kg/d; maximum = 1.54 kg/d; minimum = 0.88 kg/d) increased (P < 0.01) as RTm decreased (ADG, kg = 19.13 - 0.45 RTm; r2 = 0.28). There was a close association between RTmax and RTm (RTm = 4.57 + 0.87 RTmax; r2 = 0.84). While there are numerous factors that influence ADG of feedlot cattle, differences in ruminal temperature during periods of elevated ambient conditions (ie. temperature, humidity, ration) accounts for an important portion of that variation. [ABSTRACT FROM AUTHOR]