Desempenho e exigências de energia e proteína de bovinos de corte em pasto suplementados

Abstract

This experiment aimed to evaluate the performance, carcass characteristics, body composition, and energy and protein requirements of beef cattle under grazing conditions. The experimental area constituted of 5 paddocks with Brachiaria decumbens as forage source. Twenty two steers (Zebu) with mean body weight and ages of 320kg and 18 months, respectively, were used. Three animals were slaughtered at the beginning of the experiment and used as standard. Of the nineteen remaining animals, three were designated for maintenance group and the others were randomly submitted to one of four treatments: mineral mixture (MM), 1, 2 or 3kg of supplement daily. There was a linear increase in dry matter intake (DMI), digestible energy (DEI) and metabolizable energy (MEI), and total digestible nutrients intake (TDNI) was maximum consumption of 2.88kg of supplement. The maximum average daily gain (ADG), 0.91kg/day, was observed for supplement intake of 2.69kg/day. Linear increase was observed in shrunk body weight (SBW), EBW and carcass weight. There was no effect on the carcass allowance, however, it was observed on the ribeye area and back fat thickness. No effect was observed on carcass length and commercial cuts. The requirement of net energy (NE) and net protein (NP) increased and decreased as the animals BW increased. The maintenance requirement for net (NE m) and metabolizable energy were 85 kcal/EBW 0.75 and 130 kcal/EBW 0.75. Supplementation of cattle in the period of transition between rainy and dry seasons increased the dry matter and energy intake, promoting an increase in animal weight gain.