Effects of the EPNIX® beef program on feedlot performance in diets containing no Monensin or Tylosin

Abstract Text: This study was conducted to compare growth performance, health and carcass characteristics of beef steers fed diets containing EPNIX® products (Alltech Inc., EPNIX) with steers fed control (CON) diets formulated using conventional sources of trace minerals and common feed additives. One thousand six hundred and eighty crossbred steers (Initial BW = 347.9±23.7 kg) were used in a randomized complete block design with 2 treatments (CON and EPNIX) and 12 pens per treatment.  Pen was the experimental unit. CON diets contained trace minerals from mostly inorganic sources plus monensin and tylosin. EPNIX diets contained organic trace minerals, yeast and bacterial preparations, but not monensin or tylosin. Both treatments were fed diets containing ractopamine hydrochloride at the end of the feeding period. EPNIX products tended to increase DM intake (9.95 vs. 10.12 kg/d, P = 0.086), but there were no differences between treatments in final BW, ADG or feed efficiency (P ≥ 0.145). Carcasses from steers on the EPNIX treatment were 6.4 kg heavier (409.7 vs. 416.1, P = 0.015) than CON steers and dressed yield was 0.5 units higher (64.4 vs. 64.9 %, P < 0.001). Final BW adjusted to a common dressed yield was higher for EPNIX steers (P ≤ 0.038), as was carcass-adjusted ADG (P ≤ 0.033). Carcass adjusted feed efficiency did not differ between treatments. Differences in health parameters between treatments were not remarkable. Marbling score and quality grade distributions were not remarkably different between treatments (P ≥ 0.019). Calculated yield grade was lower (leaner) for EPNIX than CON carcasses (3.30 vs. 3.15, P = 0.049), due to heavier carcass weight and larger LM muscle area (92.5 vs. 96.3 in², P < 0.001). Liver abscess prevalence was higher for steers on EPNIX relative to CON (13.6 vs. 26.5%, P < 0.001) but measures of liver abscess severity did not differ between treatments.  Differences in meat quality parameters were not remarkable.  These results demonstrate that cattle may be fed successfully with EPNIX® products fed in lieu of monensin and tylosin, although liver abscess prevalence would be a concern. The increased dressed yield and heavier carcass weights for steers on the EPNIX treatment suggests a possible role of EPNIX products to improve carcass weight transfer.

Keywords: Antibiotics, Carcass