Performance, feeding behavior, carcass traits, rumen health, and starch digestibility of Nellore and 1/2 Angus/Nellore cattle adapted in feedlot for 9 or 14 days

Abstract

The objective of this study will be to evaluate the length of adaptation period to high concentrate diets on performance, feeding behavior, carcass and meat traits, rumen health and starch digestibility of Nellore and ½ Angus/Nellore cattle finished in feedlot. Forty-eight yearling bulls (385 kg), 24 Nellore and 24 ½ Angus/Nellore, back grounded on pasture will be randomly allocated and kept in 48 individual pens with concrete floor (10 m2 and 1,0 m bunk per animal) according to the treatments: Tl: Nellore adapted for 9 days, T2: Nellore adapted for 14 days, T3: ½ Angus/Nellore adapted for 9 days, and T4: ½ Angus/Nellore adapted for 14 days), characterizing a completely randomized design with a 2 x 2 factorial arrangement of treatments (2 genotypes and 2 lengths of adaptation period) with repeated measures over time according to the dependent variable measured. Each treatment will be composed by 12 replications (animals) in this study. After 9 or 14 days of adaptation, yearling bulls will receive the finishing diet containing 86% concentrate. 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 by ultrasound at the beginning and at the end of the study. Yearling bulls will be slaughtered in a commercial abattoir when an average body weight of 490 kg is reached after 84 days on feed. Samples of meat, rumen epithelium, and feces will be collected for future analysis of meat quality, rumen health, and starch digestibility, respectively. (AU)