Efficacy of monensin and tylosin in finishing diets based on steam-flaked corn with and without corn wet distillers grains with solubles1

Abstract

Three hundred seventy-one crossbred-yearling heifers (299 +/- 9 kg initial BW) were obtained from a common source and used in a randomized complete-block designed finishing study. A 2 x 3 factorial arrangement of treatments was used with one factor being diet: based on steam-flaked corn finishing diet (SFC) or SFC plus 25% (dry basis) corn wet distillers grains with solubles (WDGS). The second factor was feed additives: no added antibiotics (NONE), 300 mg of monensin daily (MONENSIN), or 300 mg of monensin + 90 mg of tylosin daily (MON+TYL). Main effect of diet resulted in no difference in DMI (P = 0.34). Heifers fed SFC gained 9% faster (P = 0.01) and were 7% more efficient (P = 0.01) than heifers fed WDGS. In addition, heifers fed SFC had 3% heavier (P = 0.01) HCW; 1% greater (P = 0.01) dress yield; and had 3% larger (P = 0.05) LM area. Marbling score and carcasses that graded USDA Choice or better were both greater (P </= 0.03) for heifers fed SFC. Heifers fed MONENSIN had a smaller (P = 0.01) LM area than heifers fed NONE and tended (P = 0.09) to have smaller LM area than heifers fed MON+TYL. Marbling score, USDA quality grade, and USDA yield grade were not different (P >/= 0.12) among feed additive treatments. Kidney, pelvic, and heart fat and s.c. fat thickness at the 12th rib were also not different (P >/= 0.55) for main effects of diet and feed additive. There was a tendency (P = 0.09) for a diet x feed additive interaction for the most severe (A+) liver abscesses. Heifers fed NONE yielded the greatest percentage (16%) of A+ livers in the SFC treatment, whereas heifers fed MON+TYL yielded the greatest percentage (10%) in the WDGS treatment. Including wet distillers grains with solubles in diets based on steam-flaked corn decreased finishing heifer performance, HCW, and marbling. Tylosin addition tended to decrease severity of liver abscesses in diets containing SFC, but not in diets containing WDGS. These data indicate that monensin and tylosin may not be as effective when used in steam-flaked corn diets with 25% WDGS.

Effects of monensin and virginiamycin supplementation in finishing diets with distiller dried grains plus solubles on growth performance and digestive function of steers

“…Likewise, monensin supplementation of a high-fibre finishing diet containing 60% DDGS, 10% corn silage and 10% haylage increased ADG and G:F by 5% and 4%, respectively (Felix & Loerch 2011). However, in numerous other studies involving feedlot cattle fed energy dense finishing diets based on steamflaked corn with urea as the principal source of supplemental N, monensin supplementation did not improve ADG or G:F (Zinn & Borques 1993;Zinn et al 1994;Depenbusch et al 2008;Salinas-Chavira et al 2009). The basis for the variable response is not certain.…”

Influence of Ionophore Supplementation on Growth Performance, Dietary Energetics and Carcass Characteristics in Finishing Cattle during Period of Heat Stress

“…The potential for improved feed efficiency of feedlot cattle as a result of monensin supplementation is well-documented (Zinn, 1987; Delfino et al, 1988; Stock et al, 1990). However, the magnitude of the response has been variable, ranging from nil (Stock et al, 1990; Zinn and Borques, 1993; Depenbusch et al, 2008) to greater than 18% (Bartley et al, 1979). The basis for the variable response is not clear.…”

Effect of wheat dried distillers grains and enzyme supplementation on growth rates, feed conversion ratio and beef fatty acid profile in feedlot steers

“…The results suggest that some PUFA were not completely hydrogenated in the rumen, and feeding wheat DDGS with high cis-9, cis-12 18:2 and PUFA concentrations potentially increased these fatty acid concentrations in beef. This finding suggests some degree of protection of the PUFA in DDGS from ruminal biohydrogenation (Depenbusch et al, 2008).…”