Teores de proteína para vacas lactantes em pastejo de capim-elefante

Abstract

To evaluate the effect of feeding concentrate with different crude protein (CP) contents, lactating dairy cows grazing elephant grass were distributed in a 3x3 latin square. Three kg/cow of concentrates (15.2, 18.2, or 21.1% CP) were offered twice a day. Elephant grass dry matter (DM) availability was 1,873kg/ha; with a daily offer of 17.4kg/cow. The elephant grass DM content was 19.6% with 13.9% CP, 66.1% neutral detergent fiber (NDF), and 67.4% in vitro DM digestibility. There was no difference among treatments regarding total diet DM daily intake (21.5, 21.6, and 20.8kg/cow), elephant grass DM (16.1, 16.3, and 15.5kg/cow), and elephant grass NDF (10.7, 10.7, and 10.3kg/cow). Milk yield (17.5, 17.2, and 17.6kg/d) fat (3.4, 3.5, and 3.5%), protein (2.9, 2.9, and 2.9%), lactose (4.4, 4.4, and 4.4%), and N-urea (14.1, 14.6, and 15.8mg/dL) did not differ among concentrates (P>0.05). Plasma N-urea was higher in cows fed concentrate with 21.1% CP (11.5 = 12.2<14.4mg/dL, P<0.05). According to these results, concentrate with 15.2% CP can be used to lactating dairy cows grazing elephant grass, without affecting milk production as compared to concentrate with 18.2 or 21.1% of CP.