Resposta imune humoral e desempenho produtivo em novilhas de corte suplementadas com sal mineral e metionina protegida da degradação ruminal

Abstract

The knowledge generated on the main ingredients used in bovine diets allowed greater assertiveness in the formulations. Among these ingredients, the amino acids stand out as a tool capable of reducing the total levels of crude protein and adjusting the ideal concentrations of metabolizable protein in the diets. A review of current studies on cattle supplemented with rumen-protected methionine has demonstrated the influence of this strategy on reproductive parameters, immune response and productive performance. The objective of this study was to evaluate the effects of a methionine enriched mineral salt supplementation against productive performance and humoral immune response in beef heifers. Forty-Eight Brangus nulliparous heifers were divided into four experimental groups with three replicates each: Control Group without supplementation and without vaccination (GC01), Control Group without supplementation and with vaccination (GC02), Group Treatment with mineral supplementation and with vaccination (GT01) and Group Treatment with mineral supplementation of protected methionine and with vaccination (GT02). The animals were kept in native pasture. A supplementation period prior to 60-day vaccinations was adopted until the first dose of a monovalent vaccine inactivated for BoHV-5 was used as a method of stimulating the immune response to evaluate the effects of supplementation. After 21 days, serum samples were collected to measure the humoral response and the second dose was applied, with the interval of 21 days for new serum collections. The animals were weighed on days -60, -10, 0, 21 and 42 in relation to the vaccine protocol. The groups did not differ in body weight, DAG and ECC. When vaccinated animals were compared to GC01, higher levels of neutralizing antibodies were observed 21 days after the second vaccine dose. In the comparison between the supplemented groups, there was no difference in the seroconversions against BoHV. IgG levels were higher than GC01, 21 days after the second vaccine dose, but did not differ between the supplemented groups. Thus, the study concludes that there were no benefits of mineral supplementation or enriched with methionine protected against the productive performance and the humoral immune response of the animals studied.