Reduction of the period of adaptation using only virginiamycin on starch and total gastrointestinal tract digestibility of feedlot Nellore cattle

Abstract

This project will have two objectives: 1) evaluate nutrient digestibility in the total gastrointestinal tract of rumen cannulated Nellore cattle; and 2) evaluate the starch digestibility in the total gastrointestinal tract of feedlot Nellore cattle, both aiming to reduce the length of adaptation period to high-concentrate diets containing only virginiamycin (VM) as feed additive. Two experiments will be performed in this project: 1) 5 rumen cannulated Nellore will be used in a 5x 5 Latin square experimental design with an approximate weight of 350 kg and 17 months of age. The animals will be divided into five treatments: 1- MON (MON; 30 mg / kg) with adaptation for 14 days; 2- MON (30 mg / kg) + VM (25 mg / kg) with adaptation for 14 days; 3- VM (25 mg / kg) with adaptation for 14 days; 4- VM (25 mg / kg) with adaptation for 9 days; and 5- VM (25 mg / kg) with adaptation for 6 days; and 2) 120 Nellore bulls will be used, which will be randomly allocated in 30 pens (4 animals/pen) at the feedlot facility and assigned to one of the five treatments previously described for study 1. In both studies, the digestibility of nutrients will be determined, and in the first one the total digestibility of the nutrients and their fractions by means of titanium dioxide markers will be carried out. The fecal collections will be performed for 5 consecutive days and it will start on day 8 for the animal adapted only with VM in 6 days, day 11 for the animal adapted only with VM in 9 days and on day 16 for all treatments. In the second study, the digestibility of the starch will be carried out following the methodology of Zinn et al. (2007). (AU)