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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.)

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.)

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.)

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.)

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.