Body composition and energy and protein requirements of grazing Nelore steers

• Published in: Revista brasileira de zootecnia 2009-07, Vol.38 (7), p.1347-1354
• Main Authors: Almeida, Vitor Visintin Silva de(UFV Programa de Pós-graduação em Zootecnia), Queiroz, Augusto César de(UFV DZO), Silva, Fabiano Ferreira da(UESB DTRA), Silva, Robério Rodrigues(UESB DEBI), Oliveira, Aline Cardoso(UFV Programa de Pós-graduação em Zootecnia), Souza, Danilo Ribeiro de(Universidade Estadual do Sudoeste da Bahia)
• Format: Article
• Language: English
• Subjects: AGRICULTURE, DAIRY & ANIMAL SCIENCE; energia; energy; exigências; protein; proteína; requirements; VETERINARY SCIENCES; zebu cattle; zebuínos
• ISSN: 1516-3598; 1806-9290; 1806-9290; 1516-3598
• DOI: 10.1590/S1516-35982009000700026

This experimentwas carried out with the objective of determining the energy and protein requirements of grazing Nellore steers. Twenty four Nellore steers (average 371 ± 14 kg of BW and 26 months old) were used. Four steers were slaughtered at the beginning of the experiment (reference group), serving as a reference for the subsequent study. The remaining 20 animals were weighed and distributed in a randomized complete block design with four levels of supplementation offers: 0.0 (mineral mixture - control), 0.3, 0.6 and 0.9% BW, with five replications. The supplements, based on ground corn, soybean meal and/or urea, were previously balanced to achieve an average daily gain of 350, 650 and 850g, respectively, for the different levels of supplementation offers. The protein, fat and energy contents retained in the animal body were determined by regression equations of the logarithm of the protein, fat and energy in the animal body contents, in function of the logarithm of empty body weight (EBW). Net requirements of protein and energy for a gain of 1kg of EBW were obtained by deriving the prediction equations of the animal body content of protein, fat, or energy in function of the EBW logarithm. The net energy requirements for weight gain of Nellore steer can be obtained by the equation: NEg = 0.05764 × EBW0,75 × DEBWG0.8328. The following equation was obtained to estimate the retained protein (RP), in function of the average daily gain (ADG) and retained energy (RE): RP = 28.9199 + 85.7301 FBWG + 8.0669 RE. The net protein requirement for Nellore steers decreased as the body weight increased, with values of 174.62 and 163.10 g/kg EBG for animals of 300 and 450 kg BW, respectively. Com o objetivo de determinar as exigências de energia e proteína de novilhos Nelore sob pastejo, foi conduzido um experimento utilizando 24 novilhos da raça Nelore, castrados, com peso inicial de 371 ± 14 kg e 26 meses de idade. Quatro novilhos foram abatidos no início do experimento (grupo referência) para servir de referência nos estudos subsequentes. Os animais restantes (20) foram pesados e distribuídos em delineamento inteiramente casualizado com quatro níveis de suplementação: 0,0 (mistura mineral - controle); 0,3; 0,6 e 0,9% do PC e cinco repetições. Os suplementos, à base de milho, farelo de soja e/ou uréia, foram balanceados previamente para promover ganhos médios diários de 350, 650 e 850 g, respectivamente. Os conteúdos de proteína, gordura e energia retidos no