Rumen bacterial diversity associated to protein utilization efficiency and amino acid profile for absorption in grazing Nellore steers supplemented with rumen undegraded protein during dry and rainy season

Abstract

Supplementation of cattle with rumen undegraded protein (RUP) sources may be an important strategy to supply nutritional deficiencies from forage and increases the amino acid utilization efficiency, consequently increasing performance. However, this supplementation may result in different amino acids duodenal flow when animals are maintained during dry or rainy season; this is due to the seasonality of production (composition) of tropical forages. The present project aims to evaluate the effect of ruminally undegradable protein (RUP) on intake, digestibility, ruminal fermentation and microbial diversity, duodenal amino acid profile and intestinal amino acid digestibility in grazing Nellore cattle during dry and rainy season. Two studies will be carried out, being the first trial for evaluation of protein metabolism and amino acids profile in grazing animals during dry season, supplemented with mineral salt plus urea with or without RUP. The second trial will evaluate the protein metabolism and amino acids profile in grazing animals during rainy season supplemented with mineral salt with or without RUP. In the first study eight Nellore steers will be used, cannulated in the rumen and duodenum, arranged in four simultaneous Latin squares (2x2), to evaluate nutrient intake and digestibility, ruminal and blood parameters, rumen microbiota, amino acids duodenal flow, nitrogen balance (N) and, fecal and urinary excretion of N and amino acids. In the second study, will be used 9 Nellore steers, castrated, rumen cannulated and duodenum distributed in 3 Latin squares (3x3), with three treatments (mineral salt (MS), corn gluten (GLU) or protected soybean meal (PSM)) and three experimental periods. The data will be analyzed using the PROC MIXED procedure of SAS and the means will be compared using the Tukey test. Our hypothesis is that the supplementation with RUP could results in a better amino acids profile, consequently increasing the utilization efficiency of the supplemental metabolizable protein during both dry and rainy periods, thus modifying microbial diversity. The results obtained in this proposal will allow the design of nutritional strategies in order to optimize the efficiency of N utilization in typical cattle production scenarios in Brazil. (AU)