Enzimas fibrolíticas em dietas de novilhas leiteiras: balanço nutricional

Abstract

The objective of this study was to evaluate nitrogen balance and microbial protein synthesis according to the experimental diets of Jersey heifers supplemented with cellulolytic enzymes (xylanase), corn silage or sugar cane silage. Eight heifers of the Jersey breed, 8 ± 2.5 months old, with an average weight of 160 ± 15 kg were used. The animals were randomly divided into 2 4X4, balanced and contemporary Latin squares, in a 2X2 factorial arrangement. The experimental period was 20 days, 14 days for adaptation of experimental diets and 6 for data collection. Experimental diets were: 1- Corn silage (SM); 2- Sugarcane silage (SC); 3- Corn silage + fibrozyme (SME) and 4- Sugarcaneane silage + fibrozyme (SCE). Experimental diets were formulated according to the NRC, (2001), aiming to gain weight from 800 to 900 grams per day, these being isonitrogenated. The nitrogen consumption (g / day) had a significant effect (P <0.05) on the silage (SIL), the nitrogen consumption was 30.22% higher in the corn silage compared to the silage cane. The nitrogen balance (g / day) absorbed had influence of silage and enzymes, being 40,68% greater absorption in the corn silages (SM and SME) than in the cane silages (SC and SCE). The interaction effect (INT) and enzymes (ENZ) did not show significant difference (P> 0.05) for gross energy, digestible energy, metabolizable energy, net energy of lactation, net energy of gain, energy of maintenance and energy of gain calculated in this job. The inclusion of the enzyme fibrozyme positively influenced the nitrogen balance, but did not influence the energy balance of dairy heifers receiving cane silage or corn silage.