Rumen health and starch digestibilty of feedlot Nellore cattle adapted with different protocols

Abstract

The objective of this study will be to evaluate the length of protocols of adaptation to high concentrate diets on rumen health and starch digestibility of Nellore cattle finished in feedlot. One-hundred twenty Nellore yearling bulls (385 kg) backgrounded on pasture will be randomly allocated in 24 pens with five animals per pen (5,4 m² and 0,8 m bunk per animal) according to the treatments: step up program during 9 days (S9), step up program during 14 days (S14), restriction program during 9 days (R9), and restriction program during 14 days (R14), characterizing a completely randomized design with a 2 x 2 factorial arrangement of treatments (2 protocols of adaptation lasting 9 and 14 days) with 6 replications (pens) per treatment. The step up program consisted of ad libitum feeding of three adaptation diets over periods of 9 or 14 days with concentrate level increasing from 55% to 85% of diet dry matter. The restriction program consisted of restricted intake of the final diet (85% concentrate) with programmed increases in feed offered until yearling bulls reached ad libitum access over periods of 9 or 14 days. It will be performed the following analysis: 1) macroscopic and microscopic morphological evaluations such as number and area of papillae and absorptive surface area for cm2 of rumen wall; 2) histological such as papillae height, height and area of keratinized layer of rumen epithelium, and mitotic index; 3) immunological such as blood concentration of lipopolysacaride endotoxin-binding protein; and 4) total tract digestibility of starch using chromium oxide as external marker. (AU)