Feeding strategies to minimize rumen acidification and improve feedlot performance of Nellore cattle fed high energy diets

Abstract

This project will have 2 objectives: 1) evaluate the length of adaptation period to high concentrate diets based on corn grain processed as coarsely ground; and 2) evaluate the effect of the combined use of monensin (MON) and virginiamycin (VM) in the adaptation and finishing period; all of them on feedlot performance, feeding behavior, carcass traits, starch and NDF digestibility (only study 2), and rumen health of Nellore cattle finished in feedlot. Ninety-six 22-mo-old yearling Nellore will be used in the first trial, and one hundred-twenty animals will be used in the second trial, with a average initial weight of approximately 370 kg. For the first experiment about protocols of adaptation, the treatments will be: T1 - adaption for 6 days, T2 - adaptation for 9 days, T3 - adaptation for 14 days, and T4 - adaptation for 21 days. For the second experiment, about combined use of MON and VM in either adaptation or finishing period, animals will be allocated according to the treatments: 1) MON (30 mg/kg) in the adaptation (ADAP) and finishing (FIN) period, 2) MON (30 mg/kg ) + VM ( 25 mg/kg) in ADAP and only VM (25 mg/kg) in FIN, 3 ) MON (30 mg/kg) + MV (25 mg/kg) in ADAP and FIN, 4 ) VM (25 mg/kg) in ADAP and MON (30 mg/kg) + VM (25 mg/kg) in FIN.. At the beginning of experimental period and every 28 days, yearling bulls will be weighed. Dry matter intake will be measured every day, and average daily gain and feed efficiency will be calculated. Likewise, the deposition of muscle and fat will be evaluated at the beginning and at the end of the study. Yearling bulls will be slaughtered when an average body weight of 490 kg is reached after 84 days on feed. Samples of rumen epithelium, and ration and feces will be collected for future analysis of rumen health, and starch and NDF digestibility, respectively. (AU)