Determining the optimal dose of virginiamycin for ruminal parameters and performance of Nellore cattle on pasture / Determinação da melhor dose resposta de virginiamicina nos parâmetros ruminais e desempenho de bovinos Nelore a pasto

There are no studies evaluating the virginiamycin (VM) doses under tropical conditions. So, the present study was conducted to evaluate the optimal dose of VM for growing Nellore bulls on tropical pasture. Two experiments were conducted. The first experiment, one hundred and two Nellore bulls (307 ± 25 kg body weight [BW]; 22 months) were used. Animal performance was evaluated using a randomized block design, with group as experimental unit (n = 8; 12 animals each). The second experiment, a double 4 × 4 Latin square, eight animals were used to evaluate the ruminal parameters. Four doses were evaluated: 0, 35, 55, and 75 mg VM per 100 kg BW. The average daily gain (P = 0.08) and carcass gain (P = 0.05) exhibited a trend of quadratic behavior. An increased dose of VM did not affect supplement intake (P = 0.64), rumen pH (P = 0.96), acetate: propionate ratio (P = 0.73), or the total concentration of volatile fatty acid (P = 0.63). The concentration of rumen ammonia nitrogen exhibited a quadratic effect (P = 0.01). A quadratic behavior was found for volatile fatty acid, except for propionate, which presented linear behavior (P = 0.03). In conclusion, the dose of 47 mg VM per 100 kg BW is recommend for growing Nellore bulls on tropical pasture.(AU)

Em condições tropicais não existem estudos avaliando doses de virginiamicina (VM). Dessa forma, o presente estudo foi conduzido para avaliar a dose ótima de VM para bovinos Nelore recriados em pasto tropical. Dois experimentos foram conduzidos. No Experimento 1 foram usados 102 bovinos Nelore não castrados, com peso corporal (PC) inicial de 307 ± 25 kg e 22 meses de idade. As variáveis de desempenho foram avaliadas em blocos inteiramente casualizados, sendo o grupo a unidade experimental (n = 8; 12 animais cada). No Experimento 2 foram utilizados 8 animais em quadrado latino duplo para avaliação dos parâmetros ruminais. Foram avaliadas 4 doses de VM: 0, 35, 55, e 75 mg VM para cada 100 kg PC. O ganho médio diário (P = 0.08) e o ganho em carcaça (P = 0.05) apresentaram tendência de comportamento quadrático. O aumento na dose de VM não afetou o consumo de suplemento (P = 0.64), pH ruminal (P = 0.96), relação acetato: propionato (P = 0.73) e a concentração total de ácidos graxos voláteis (P = 0.63). A concentração de nitrogênio amoniacal ruminal apresentou efeito quadrático (P = 0.01). Comportamento quadrático foi observado para todos os ácidos graxos voláteis, exceto propionato, o qual apresentou comportamento linear (P = 0.03). Em conclusão, a dose de 47 mg VM/100 kg PC é recomendada para bovinos Nelore recriados em pastos tropicais.(AU)

Determining the optimal dose of virginiamycin for ruminal parameters and performance of Nellore cattle on pasture / Determinação da melhor dose resposta de virginiamicina nos parâmetros ruminais e desempenho de bovinos Nelore a pasto

There are no studies evaluating the virginiamycin (VM) doses under tropical conditions. So, the present study was conducted to evaluate the optimal dose of VM for growing Nellore bulls on tropical pasture. Two experiments were conducted. The first experiment, one hundred and two Nellore bulls (307 ± 25 kg body weight [BW]; 22 months) were used. Animal performance was evaluated using a randomized block design, with group as experimental unit (n = 8; 12 animals each). The second experiment, a double 4 × 4 Latin square, eight animals were used to evaluate the ruminal parameters. Four doses were evaluated: 0, 35, 55, and 75 mg VM per 100 kg BW. The average daily gain (P = 0.08) and carcass gain (P = 0.05) exhibited a trend of quadratic behavior. An increased dose of VM did not affect supplement intake (P = 0.64), rumen pH (P = 0.96), acetate: propionate ratio (P = 0.73), or the total concentration of volatile fatty acid (P = 0.63). The concentration of rumen ammonia nitrogen exhibited a quadratic effect (P = 0.01). A quadratic behavior was found for volatile fatty acid, except for propionate, which presented linear behavior (P = 0.03). In conclusion, the dose of 47 mg VM per 100 kg BW is recommend for growing Nellore bulls on tropical pasture.

Em condições tropicais não existem estudos avaliando doses de virginiamicina (VM). Dessa forma, o presente estudo foi conduzido para avaliar a dose ótima de VM para bovinos Nelore recriados em pasto tropical. Dois experimentos foram conduzidos. No Experimento 1 foram usados 102 bovinos Nelore não castrados, com peso corporal (PC) inicial de 307 ± 25 kg e 22 meses de idade. As variáveis de desempenho foram avaliadas em blocos inteiramente casualizados, sendo o grupo a unidade experimental (n = 8; 12 animais cada). No Experimento 2 foram utilizados 8 animais em quadrado latino duplo para avaliação dos parâmetros ruminais. Foram avaliadas 4 doses de VM: 0, 35, 55, e 75 mg VM para cada 100 kg PC. O ganho médio diário (P = 0.08) e o ganho em carcaça (P = 0.05) apresentaram tendência de comportamento quadrático. O aumento na dose de VM não afetou o consumo de suplemento (P = 0.64), pH ruminal (P = 0.96), relação acetato: propionato (P = 0.73) e a concentração total de ácidos graxos voláteis (P = 0.63). A concentração de nitrogênio amoniacal ruminal apresentou efeito quadrático (P = 0.01). Comportamento quadrático foi observado para todos os ácidos graxos voláteis, exceto propionato, o qual apresentou comportamento linear (P = 0.03). Em conclusão, a dose de 47 mg VM/100 kg PC é recomendada para bovinos Nelore recriados em pastos tropicais.

Effect of increasing monensin sodium levels in diets with virginiamycin on the finishing of Nellore cattle.

This study evaluated the effect of increasing levels of monensin sodium (MON) in diets with virginiamycin (VM) on the finishing of feedlot cattle. Two hundred and eighty intact male Nellore cattle (348 ± 32 kg body weight, 22 months) received one of the following five diets: control diet (without additives); diet containing VM (25 mg per kg dry matter) combined with 0 (MON0), 10 (MON10), 20 (MON20) or 30 (MON30) mg MON per kg dry matter. During adaptation (28 days), the MON0 diet increased dietary net energy for maintenance and gain compared to the control diet (P = 0.04). The combination of additives linearly reduced dry matter intake, body weight and average daily gain (P < 0.01). Considering the total study period (110 days), there was a trend of greater net energy intake for maintenance (P = 0.09) and hot carcass weight (P = 0.06) for animals fed MON0 compared to the control diet. The combination of additives linearly reduced dry matter intake (P = 0.04) and linearly increased gain : feed and dietary net energy for maintenance and gain (P < 0.01). The combination of VM with MON at a dose of 30 mg/kg dry matter is recommended for Nellore feedlot cattle because it improves the efficiency of energy utilization.

Effect of supplementation of beef cattle with different protein levels and degradation rates during transition from the dry to rainy season.

The objective of this study was to evaluate the effect of increasing the supply of protein with different degradation rates on the performance and metabolism of growing Nellore cattle reared on Brachiaria brizantha cv. Marandu pasture during the transition period from the dry to rainy season. The experiment was installed on an area of 34 ha, divided into 12 paddocks with an average area of 2.85 ha. In the performance evaluation were utilized 72 recently weaned, non-castrated Nellore cattle with an initial body weight (BW) of 199 kg (SEM = 16). The following supplements were used: energy protein supplement containing 25% crude protein (CP) (C-25) and energy protein supplements containing 40% CP with one third highly degradable CP and two thirds poorly degradable CP (40-1/3NPN), one half highly degradable CP and one half poorly degradable CP (40-1/2NPN), and two thirds highly degradable CP and one third poorly degradable CP (40-2/3NPN). Higher protein degradation rates reduced supplement intake (P < 0.01). In the first period, animals consuming supplement 40-1/3NPN exhibited higher average daily gain (ADG) (0.30 kg/day), similar to that of animals receiving supplement 40-1/2NPN (P = 0.04). In the second period, supplement 40-2/3NPN resulted in lower ADG (0.19 kg/day less than the other supplements). There was no effect of supplement on animal performance in the third period (P > 0.10), when ADG was 0.56 kg/day. In conclusion, the response to supplementation is associated with interactions with characteristics of the forage canopy. Supplementation with a true protein source will be beneficial only during the early stage of the dry-rainy season transition period.