<b>Body composition and deposition efficiency of protein and energy in grazing young bulls

Abstract

The effects of supplementation with different protein: carbohydrate ratios on body composition, carcass characteristics and protein and energy deposition efficiency of young were assessed. Twenty-four Nellore calves (132.5 ± 5.5 kg and 90-150 days of age) were kept on pasture for a 430 day experimental period. The treatments were: Control = mineral mixture only; HPHC = high-protein and high-carbohydrate supplement; HPLC = high-protein and low-carbohydrate supplement; LPHC = lowprotein and high-carbohydrate supplement; LPLC = low-protein and low-carbohydrate supplement. Four animals at begning and 20 animal at end of experiment were slaughtered to evaluate the carcass composition. Control bulls had the lowest (p < 0.05) intake of ME (9.8 Mcal day-1) with no difference (p > 0.05) between supplemented bulls (13 Mcal day-1). Although non-supplemented bulls had less (p < 0.05) retained protein, retained energy (RE), body weight gain and dressing percentage, differences were not observed (p > 0.05) between supplemented bulls. High-carbohydrate supplements were associated with more (p < 0.05) RE (596.2 Mcal) than low-carbohydrate supplements (515.5 Mcal). Differences were not found (p > 0.05) in the energy efficiency between the groups. Therefore, supplementation increases the intake and retention of protein and energy without changing the retention efficiency.

Nitrogen partitioning and microbial protein synthesis in lactating dairy cows with different phenotypic residual feed intake

“…In the present study, the low RFI cows retained less N than the high RFI cows, which may be due to their lower DMI. Moreover, other studies with male cattle [42] and young bulls [43] have proposed that N retention increases due to a rise in the N supply. However, the ADG of two groups were not different, which is inconsistent to the differences in N retention.…”