Net essential amino acids requirements for Nellore and crossbred Angus x Nellore cattle

摘要

The objective of this study was to determine the net amino acid (AA) requirements for Nellore and Nellore-Angus crossbred bulls fed different crude protein (CP) contents (100, 120 and 140 g CP/kg dry matter intake). Forty-four bulls (22 Nellore and 22crossbred) were used in this experiment. Four bulls from each genetic group were slaughtered at the beginning of the experiment. The remaining 36 bulls were randomly assigned to one of three dietary treatments, and they were fed ad libitum. The experiment was a completely randomized design in a 2x3 factorial scheme (two GG and three CP contents). All animals were slaughtered after 224 days. The AA composition of the empty body weight (EBW) was determined. Net requirements were accessed through nonlinear models for each AA as a function of EBW. The estimates for the net requirements of lysine and methionine were 7.3 and 2.0 g/100 g retained CP, respectively, for a bull with an EBW weight of 400 kg.