Avaliação de marcadores de proteína microbiana ruminal e sua relação com diferentes fontes proteicas na estimativa da oferta de proteína metabolizável em ovinos

Abstract

The present study aimed to analyze the relationship between microbial protein markers (Pmic) and the influence of different protein sources in the diet on the estimation of metabolizable protein available for sheep. Five castrated male lambs of the Corriedale x Suffolk breed (35 ± 5 kg of live weight), surgically implanted with ruminal probes and "T" type cannulas in the proximal duodenum, were used in an incomplete 3 × 3 double Latin square design, with an additional period. The experimental diets were isoproteic and formulated with 60% forage and 40% concentrate on a dry matter (DM) basis. Corn silage was used as the forage, and the concentrates were formulated with ground corn, mineral premix, common salt, and one of the following protein sources: dried distillers' grains with solubles (DDG), soybean meal (SBM), or soybean cake (SC). The markers evaluated were purine derivatives, purines, and 15N. The diets evaluated in the present study did not affect the dry matter flow (DMF; P = 0.58). The DMF from the rumen was directly associated with the animals' DM intake (DMI) (P = 0.039). The influence of markers was observed only in treatments using SBM and SC. This suggests that, in situations of low ruminal degradability, as observed with the use of DDGs, Pmic is consistently estimated using the different markers. However, in scenarios with greater ruminal degradability, the choice of the Pmic estimation method has a significant impact, resulting in differences in the estimates provided by the markers used.