Energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two forage: concentrate ratios

AUTOR(ES)

Souza, Evaristo Jorge Oliveira de, Valadares Filho, Sebastião de Campos, Guim, Adriana, Valadares, Rilene Ferreira Diniz, Marcondes, Marcos Inácio, Véras, Antonia Sherlânea Chaves, Amaral, Paloma de Melo, Santos, Tathyane Ramalho

FONTE

Revista Brasileira de Zootecnia

DATA DE PUBLICAÇÃO

2012-03

RESUMO

The objective of this study was to determine the energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two levels of concentrate. Sixty heifers from three genetic groups were used: 20 Nellore, 20 Nellore × Angus and 20 Nellore × Simmental. Twelve belonged to the reference group (four of each genetic group) and were slaughtered at the beginning of the experiment. Another 12 heifers (four of each genetic group) were fed on the maintenance level and 36 heifers (12 animals of each genetic group) were kept in feeding system ad libitum with 30 (six in each group) or 50% (six of each group) dry matter concentrate. Animals were randomly assigned to six treatments in a 3 × 2 factorial arrangement (three genetic groups and two diets) with six replicates per treatment. Nine more heifers were used in a parallel experiment to estimate the apparent digestibility coefficients (three from each genetic group). Net energy requirements were estimated by the equation of retained energy as a function of metabolic empty body weight (EBW0.75) and empty body weight gain (EBWg). Requirements of metabolizable and net energy were estimated for maintenance by the equation of heat production as a function of metabolizable energy intake. Using the combined equation RE (retained energy; Mcal/day) = 0.0703 × EBW.75 × EBWg1.128 to predict net energy requirements for weight gain is recommended. The requirement of metabolizable and net energy for maintenance of all groups is 70.55 and 106.53 kcal/kgEBW0.75/day, respectively. Use efficiencies of metabolizable energy for gain and maintenance are 36.41 and 66.23%, for the three genetic groups respectively.

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