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Effect of dietary protein content on performance, feed efficiency and carcass traits of feedlot Nellore and Angus × Nellore cross cattle at different growth stages

Published online by Cambridge University Press:  14 January 2018

P. M. Amaral
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil
L. D. S. Mariz
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil School of Veterinary and Animal Sciences, Universidade Federal da Bahia, Ademar de Barros St, 40170-110, Bahia, Brazil
D. Zanetti*
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil Instituto Federal de Educação, Ciência e Tecnologia do Sul de Minas Gerais, Machado-Paraguaçu Road, km 3, 37750-000, Minas Gerais, Brazil
L. F. Prados
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil Agência Paulista de Tecnologia dos Agronegócios, Rui Barbosa St, 14770-000, São Paulo, Brazil
M. I. Marcondes
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil
S. A. Santos
Affiliation:
School of Veterinary and Animal Sciences, Universidade Federal da Bahia, Ademar de Barros St, 40170-110, Bahia, Brazil
E. Detmann
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil
A. P. Faciola
Affiliation:
Department of Animal Sciences, University of Florida, Gainesville, Florida, 32611-0910, USA
S. C. Valadares Filho
Affiliation:
Department of Animal Science, Universidade Federal de Viçosa, PH Rolfs St, 36570-900, Minas Gerais, Brazil
*
Author for correspondence: D. Zanetti, E-mail: diego.zanetti@ifsuldeminas.edu.br, diegozanetti_@hotmail.com

Abstract

An experiment was conducted to evaluate whether a reduction in dietary crude protein (CP) and genotype affects animal performance, feed efficiency and carcass traits of beef cattle at different stages of the feedlot. Twenty-two Nellore and 22 crossbred F1 Angus × Nellore (Nellore: 8 months, initial body weight (iBW) = 212.7 kg; Crossbred: 8 months, iBW = 226.1 kg) were used in this experiment. The experiment was conducted in a complete randomized design with six replicates, in a 2 × 3 factorial design. The factors were two genotypes (Nellore and Crossbred) and three CP concentrations (100, 120 and 140 g/kg dry matter [DM]). The experimental period lasted 224 day, being divided into two stages (Backgrounding = 112 day, and Finishing = 112 day). At the end of the experiment, all animals were slaughtered to evaluate their carcass characteristics. Similar patterns were observed during backgrounding and finishing phases on intake and average daily gain (ADG) regarding genotype. Intakes of DM, organic matter, CP, neutral detergent fibre, non-fibre carbohydrates and total digestible nutrients, ADG (kg/day) and feed efficiency were greater in Crossbred animals than Nellore in both phases. During the backgrounding phase, dietary CP did not influence DM intake. However, a linear effect of CP on ADG was observed in the backgrounding phase. During finishing, Nellore cattle fed 100 g CP/kg DM presented lower ADG than Nellore fed 120 and 140 g CP/kg DM. Crossbred animals were heavier than Nellore at the beginning and end of the trial. Crossbred animals also gained more carcass, retained more CP and fat, and had a greater subcutaneous fat thickness during the experiment compared with Nellore. There was a quadratic effect of dietary CP on retained CP and dressing. The current study found that crossbred animals (F1 Angus × Nellore) not only had greater performance, but also better carcass traits compared with Nellore, representing an option for increasing productivity. Also, it is possible to adjust diets according to phase. During the backgrounding stage, 140 g CP/kg DM should be used, being reduced to 120 g CP/kg DM during the finishing stage of feedlot for Nellore and to 100 g CP/kg DM for Crossbred, without affecting performance adversely.

Information

Type
Animal Research Paper
Copyright
Copyright © Cambridge University Press 2018 

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