Métodos de amostragem e caracterização química da Brachiaria brizantha cv. Marandu, consumida por bovinos na época da seca

Abstract

The aim of this study was to evaluate the forage quality of Marandu Grass (Brachiaria brizantha cv. Marandu) under grazing using three sampling methods: total dry matter (CS), hand-plucking sample (PS) and extrusa (EXT), estimating chemical-bromatological composition and the fractionation of nitrogen compounds and carbohydrates. The CS was published from an area delimited by a metallic frame (0,25m²), thrown randomly in the pickets. The PS was performed manually by three evaluators, observing the grazing behavior and material ingested by the animal. In the collection of EXT, the rumen was emptied of s bull with a ruminal cannula, and later submitted to grazing for 30-40 minutes, to obtain around 400g of sample. The experiment lasted a total of 90 days, divided into 3 periods. During the experimental period, the average amount of dry matter and green matter available to 3,2ton/ha and 4,9ton/ha, respectively. The experimental design used was completely randomized, where the sampling methodologies were compared by the tukey test at 5%. The values of NDF, FDA, CEL, HCEL, LIG and CHOT, were higher in the total dry matter, as compared to the other systems. A decrease in the availability of dry and total green matter was also observed, as the experiment was conducted during the dry season, justifying the problem of seasonality in tropical grasses. According to the results, the EXT sampling method was the one with the highest PB and CZ content, and the lowest NDF and FDA content. The chemical composition of forage is influenced by different sampling methods.