Caecum morphometrics of feedlot Nellore cattle fed virginiamycin to shorten the adaptation and increase carcass weight

Abstract

Two studies will be designed to evaluate the cecum morphometrics of feedlot Nellore cattle virginiamycin (VM) to shorten the adaptation period and increase hot carcass weight. In both studies will be used 120 animals with 370 kg divided into 30 pens (n = 4 per pen). The first study will have the following treatments: 1) Sodium monensin (MON; 30 mg/kg) with 14 adaptation days; 2) MON (30 mg/kg) + VM (25 mg/kg) with 14 adaptation days; 3) VM (25 mg/kg) with 14 adaptation days; 4) VM (25 mg/kg) with 9 adaptation days; and 5) VM (25 mg/kg) with 6 adaptation days. One animal per pen (n = 30) will be slaughtered at the end of adaptation period and ninety will be slaughtered at the end of finishing period for cecum evaluation. The second study will have the following treatments: 1) MON (30 mg/kg) the entire feeding period and 14 adaptation days; 2) VM (25 mg/kg) the entire feeding period with the best first study adaptation period (6, 9 or 14 days); 3) VM (25 mg/kg) + MON (30 mg/kg) during adaptation and only VM (25 mg/kg) during finishing period; 4) VM (25 mg/kg) + MON (30 mg/kg) during the entire feeding period with 14 adaptation days; and 5) VM (25 mg/kg) + MON (30 mg/kg) during 14 adaptation days and finishing period 1 and only VM (25 mg/kg) during finishing period 2. Cecum evaluation will be performed after cattle evisceration, and all entire washed cecum will be scored. It will be evaluated in this study cecum score, crypt depth, number of crypt and goblet cells. (AU)