Resumo Objetivou-se avaliar o efeito da redução na frequência de suplementação proteico-energética sobre o consumo de nutrientes, degradabilidade e digestibilidade da forragem, assim como o pH e concentração de nitrogênio amoniacal (N-NH3) ruminal em bovinos de corte recebendo feno de baixa qualidade. Foi utilizado o delineamento quadrado latino de 4 x 4. Quatro bovinos foram alimentados com feno de baixa qualidade e submetidos aos seguintes tratamentos: sem suplementação (controle); suplementação com 0,82% do peso corporal (PC), três vezes por semana (3x); 0,49% do PC, cinco vezes por semana (5x); e 0,35% do PC sete vezes por semana (7x). O uso do suplemento proteico-energético aumentou a ingestão de matéria seca (MS), PB (proteína bruta), FDN (Fibra em detergente neutro), EE (extrato etéreo), CNF (carboidratos não fibrosos) e os coeficientes de digestibilidade da PB, EE e CNF. Entretanto, não foram observadas diferenças na degradação da MS e FDN do feno entre os tratamentos. A suplementação não alterou o pH ruminal, mas a concentração de nitrogênio amoniacal (N-NH3) foi maior no tratamento 7x. A redução na frequência de suplementação proteico-energética diária para 3x ou 5x não afetou negativamente o consumo, digestibilidade e degradabilidade dos nutrientes em bovinos de corte recebendo feno de baixa qualidade.

Abstract The aim was evaluated the effect of reduce in protein-energy supplementation frequency on nutrients intake, forage digestibility and degradability, as well as, ruminal pH and ammonia nitrogen (N-NH3) concentration in beef cattle receiving low-quality hay. A 4 x 4 Latin square design were used. Four steers were fed with low-quality hay and subjected to four treatments: no supplementation (control); protein-energy supplementation with 0.82% of body weight (BW) offered three times per week (3WK); 0.49% of BW offered five times a week (5 WK), and 0.35% of BW offered seven times per week (7 WK). The use of protein-energy supplementation increased intake of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), ether extract (EE), non-fibrous carbohydrates (NFC) and the digestibility coefficients of CP, EE, and NFC. However, no differences in DM and NDF degradation visit the website to get the how were observed between treatments in the evaluated hay. Supplementation did not alter ruminal pH, but the N-NH3 concentration was highest in treatment 7WK. Reduction in protein-energy supplementation frequency of daily to 3WK or 5WK does not negatively affect intake, digestibility and degradability of nutrients in beef cattle receiving low quality hay.

ABSTRACT The objective was to evaluate the addition of antibiotic growth promoters to free-choice mineral supplement on ingestive behavior, mineral intake, and growth performance of grazing bulls. Sixty Nellore bulls [initial body weight (BW) of 219±17.8 kg and 15±2 months of age] were divided in 12 marandu grass paddocks. The treatments were: mineral supplement (control), mineral supplement + virginiamycin (VIRG), mineral supplement + lasalocid sodium (LASA) and mineral supplement + salinomycin sodium (SALI). Mineral supplements were formulated with target intake of 60 g d−1 and the growth promoters of 75 mg 100 kg−1 of BW. The experimental design was the completely randomized blocks. There was no treatment effect on ingestive behavior or mineral intake; however, the active ingredient intake differed between treatments. In the last experimental period, the intake of active ingredient LASA and SALI were higher than VIRG (0.66, 0.54, and 0.39 mg kg−1 of BW, respectively). Treatments also did not affect BW and average daily gain, which were 0.63, 0.60, 0.64, and 0.62 kg d−1 for control, VIRG, LASA, and SALI, respectively. Free-choice mineral supplementation intake by bulls has a high variability, and this impairs the regulation of the intake of antibiotic growth promoter additives. Therefore, the addition of antibiotic growth promoters to the mineral supplement does not affect ingestive behavior, mineral intake, and growth performance of grazing bulls.

The objective was to determine the effects of driving on the growth of steers during 55 days of moving by drive and 84 days after the arrival. Twenty-five steers were randomly chosen from a herd of 1,000 Nellore cattle, which were evaluated in two periods: the driving period, in which animals were moved a distance of 700 km on foot for 55 d; and the post-driving period, which lasted 84 d. Serum samples were obtained for hormone dosing (T3, T4, cortisol, and IGF-I) by radioimmunoassay using commercial kits. The data was collected at different time points during the experiment. No changes in live weight were observed between days 0 and 55. During the post-driving period, on the 28th, 56th, and 84th d, the average weights were 226.10 kg, 224.28 kg, and 242.6 kg, respectively; differences in weight were observed on the 84th d when compared with the 56th d. There were no changes in insulin and T3 levels in either periods; the lowest T4concentration was observed during the driving period. The serum T4concentration increased after 56 d of post-driving, and it was greater than the concentrations detected on the other days. The highest levels of cortisol were identified after 28 d of post-driving. An increase in IGF-I concentration was observed after 56 and 84 d of post-driving. Moving cattle by driving does not alter the weight of the animals and weight gain occurs during the post-driving period due to an increase in the T4 and IGF-I levels.