Nutritional requirements of energy, protein and macrominerals for maintenance and weight gain of young crossbred Nellore × Holstein bulls on pasture.
2012
PORTO, M. O. | PAULINO, M. F. | VALADARES FILHO, S. de C. | DETMANN, E. | CAVALI, J. | SALES, M. F. L. | VALENTE, E. E. L. | COUTO, V. R. M. | MARLOS OLIVEIRA PORTO, UNIVERSIDADE FEDERAL DE RONDÔNIA; MÁRIO FONSECA PAULINO, UNIVERSIDADE FEDERAL DE VIÇOSA; SEBASTIÃO DE CAMPOS VALADARES FILHO, UNIVERSIDADE FEDERAL DE VIÇOSA; EDENIO DETMANN, UNIVERSIDADE FEDERAL DE VIÇOSA; JUCILENE CAVALI, UNIVERSIDADE FEDERAL DE RONDÔNIA; MAYKEL FRANKLIM LIMA SALES, CPAF-AC; ÉRITON EGIDIO LISBOA VALENTE, UNIVERSIDADE FEDERAL DE VIÇOSA; VICTOR REZENDE MOREIRA COUTO, UNIVERSIDADE FEDERAL DE VIÇOSA.
The objective of this study was to estimate requirements of energy, protein and macrominerals of young Nellore/Holstein crossbreds bulls supplemented on pastures of Brachiaria decumbens Stapf. Thirty-five young bulls, at 8.53±0.18 months of age and with initial body weight of 230.6±6.1 kg were used. Ten animals were slaughtered as reference, in different weight range, and the other animals were slaughtered at the end of the experimental period. For estimate of net energy requirements for weight, a regression equation between log of retained energy (RE) and log of empty body weight gain (EBWG) was constructed. Net requirements of Ca, P, Mg, Na and K were determined by the equation Y' = a.b.Xb-1, in which a and b represent the intercept and the coefficient of equation of prediction of macrominerals in body content, respectively. Requirements of metabolizable energy for maintenance (MEm) were obtained from retained energy in function of metabolizable energy intake (MEI). The requirements of MEm of Nellore/Holstein crossbreds young bulls on pasture was 125 kcal/EBW0.75/day. The efficiency of ME utilization for maintenance (km) of grazing Nellore/Holstein crossbred young bulls was 0.58 and 0.24 for gain. The total metabolizable protein requirements for an animal with 400 kg and with average daily gain of 1.0 kg, were 638.36 g/day. The dietetic requirements of Ca and P for an animal with 400 kg BW were 0.49 and 0.21% of DM, respectively. Daily metabolizable energy requirement for maintenance of grazing Nellore/Holstein crossbred young bulls was 11.6% greater than the values found for cattle in feedlot in Brazil (112 kcal/kg EBW0.75).
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