Substituição parcial do farelo de soja por farelo de soja tratado com amino resina na dieta de vacas F1 Holandês x Gir manejadas em pastejo intensivo

Abstract

The study aimed to evaluate the partial replacement of the conventional soybean meal (SBM) with soybean meal treated with amino resin (FST) in the diet of lactation dairy cows managed in intensive grazing system and its effects on intake and digestibility of the diet, milk production and composition, efficient of N use (ENN) and microbial protein synthesis. Eighteen F1 Holstein x Gir cows were distributed in replicated 3x3 with 21d Latin square design with 21d of experimental periods. The control diet contained 14.4% of conventional soybean meal, which was replaced with equivalent amounts (DM basis) of FST on two levels 28%, 1.0 kg as-fed basis (FST1.0), and 42% 1,5 kg in as-fed basis (FST1.5). Diets were isonitrogenous and isocaloric and met the requirements of the animals. The animals fed the diet FST1.5 produced on average 1.3 kg/d more milk compared to treatment with FS. No differences were found between treatments for the parameters of consumption and milk composition. The feed efficiency and nitrogen use did not differ between treatments. No differences were observed for milk urea nitrogen (MUN). Treatment FSAR1.5 decrease plasma urea nitrogen (PUN) when compared with FSAR1 but not to FSC. The replacement of SBM in order to increase undegradable rumen protein (RUP) content in the diets increased milk production without changes its composition, pasture and concentrate intake and apparent digestibility of nutrients.