Potencial leiteiro de vacas primíparas da raça pantaneira mantidas em regime de pastejo com diferentes níveis de concentrado

Abstract

The aim of this study was to evaluate the performance, digestibility and blood and urinary parameters of primiparous cows Pantaneira breed, kept under continuous grazing in mombasa-grass (Panicum maximum) with different levels of supplementation and quantify the lactation persistency. Thus 5 primiparous cows, with average weight of 396.2±43.5kg, were keptin continue grazing regime and supplemented with different levels of concentrate. Levels of supplementation were 0.0; 0.3; 0.6; 0.9 and 1.2% of body weight. The experimental design used for the collection of variables from animals was the Latin square. Milk production increased with increasing level of concentrate in the diet, while the percentage of fat decreased linearly and lactose linear increase. The forage biomass, with their respective fractions, of the leaf, stem and senescent materials, showed no differences in the treatments. The rate of herbage accumulation showed increasing trend due to the levels of concentrate. The crude protein of leaf and total carbohydrates of leaf and stem were also positively influenced by the treatments. The concentration of plasma urea increased, while that the others blood and urinary parameters were not statistically significant. The lactation curves of individual cows were estimated using the univariate model and the analysis of nutritional quality of milk was effected by ultrasound method. The persistence of lactation of primiparous cows Pantaneiras was 150 days and ended spontaneously. The average milk yield was 6.30 kg milk/day, being the lactation peak comprised between the 50th and 60th day. We observed invariability between producing animals, indicating the need of more research for selection of a dairy pedigree. The average fat, protein, lactose andnon-fat total solids contents of milk were 4.3, 3.8, 6.2 and 10.9%, respectively.