Desempenho produtivo de vacas da raça Gir leiteira em confinamento alimentadas com níveis de concentrado e proteína bruta nas dietas

Abstract

The objective of this work was to evaluate the effect of increasing levels of concentrate and crude protein in the diets, in which intakes of dry matter and nutrients, coefficients of digestibility, milk production and composition and efficiency of food use were evaluated. Twenty cows in lactation were distributed in a random block design, with five replicates per diet, defined according to milk production. The experimental diets were constituted of sorghum silage as roughage and concentrate at the following levels: 11.7; 23.3; 35.2 and 46.8% with four levels of crude protein (CP) (11.0; 12.0; 14.0 and 16.0%) on diet dry matter basis. Increases in the levels of concentrate and crude protein caused a greater increase in the total dry matter intake. The coefficient of digestibility of crude protein was influenced by greater levels of concentrate and crude protein in the diet. Milk production was greater for cows fed diets with greater levels of concentrate and crude protein but it did not differ among cows fed other diets. For cows of milking Gyr breed kept in the conditions of this research, levels of 23.3% concentrate and 12% of crude protein in the diet present the best productive response. © 2010 Sociedade Brasileira de Zootecnia.