Body composition and net protein and energy requirements for weight gain of crossbred dairy cattle in grazing

Dulciene Karla Bezerra De Andrade,Wellington Samay De Melo,Mércia Virginia Ferreira Dos Santos,Kedes Paulo Pereira,Antonia Sherlânea Chaves Véras,Marcelo De Andrade Ferreira

doi:10.1590/s1516-35982009000400022

Abstract

The body composition and net protein and energy requirements for weight gain of 5/8 Hostein-Zebu crossbred cattle raised in Brachiaria decumbens Spaft pasture were evaluated. In total, 16 bulls with 10 months of age and body weight (BW) of 180 ± 19.95 kg were used. The animals were kept with free access to pasture or with restricted grazing (from 6 to 10 h). Four animals were slaughtered at the beginning of the experimental period to estimate the empty body weight (EBW) and the initial body composition of the remaining animals. The other animals were slaughtered at the end of the 84-day trial period. The logarithm equations of the protein and energy body content were adjusted according to the logarithm of the empty body weight EBW. From these equations, the net protein and energy requirements for weight gain were estimated. There was an increase in fat (from 37.17 to 59.08 g/kg EBW) and energy (from 1.68 to 1.94 Mcal/kg EBW) concentrations, with increase in body weight from 150 to 250 kg. The protein and energy requirements for gaining 1 kg of EBW increased with the increase in body weight or empty body weight. The relationship between fat concentration in gain and protein requirements also increased, indicating that as the BW or EBW increase, more fat deposition in the gain is observed.

Highlights

The success of any activity requires maximum efficiency of the production means and total control of the factors involved
In Brazil, studies on the nutritional requirements of cattle have been developed in feedlot system (Sources et al, 2005); this work was aimed to estimate the body composition and the net protein and energy requirements to gain in crossbred cattle in pasture
In the prediction of the empty body weight (EBW) from the body weight (BW) of animals used in this experiment, a significant linear effect (P

Summary

Introduction

The success of any activity requires maximum efficiency of the production means and total control of the factors involved. The first challenge in estimating the nutritional requirements is the measurement of the physical and chemical body composition, which varies during growth and may be influenced by age, maturity, gain rate, breeding, gender and nutritional level (Garret, 2000). Young animals present higher proportions of protein and water and lower proportions of fat (Berg & Butterfield, 1976), which, according to Grant & Helferich (1991) is caused by the deceleration of the muscle growth, confirmed by the lower protein gain in the empty body weight (EBW) and the further development of adipose tissue. Animals with high growth rate, yield potential and maturity present higher maintenance cost. As described by Geay (1984), in animals of late maturity and high growth potential, the reduction in energy consumption affects more the protein retention and growth rate than the fat deposition. The fat proportion in the gain of females is higher than in steers, which is higher than in non-castrated males

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