Qualidade do leite de vacas F1 Holândes/Zebu alimentadas com diferentes níveis de fornecimento da dieta

Abstract

The objective of this study was to evaluate the effects of different dietary levels of diet for F1 Holstein / Zebu cows on a physicochemical composition and milk fatty acid profile. Sixty lactating cows were used. The experimental design was completely randomized in a 5 x 3 factorial scheme, with 5 diet supply levels and 3 lactation periods. Dietary supply levels were: diet bread at will and diets provided in, 2.75; 2.5; 2.25; 2.0% of body weight. The mean values of lactation days in each experimental period evaluated and their objectives are: 1st period (50.0 ± 12.80 days); 2nd period (111.5 ± 11.75 days); 3rd period (183.0 ± 17.5 days). Twenty cows were used per experimental period, four cows per treatment. The experiment was divided into three periods of 21 days, with 16 days of adaptation and 5 days of collection. As samples of milk from each cow were analyzed for the physicochemical composition, somatic cell count and milk fatty acid profile. The different levels of diet supply in relation to the percentage of live weight did not influence the production of milk corrected to 3.5% of fat. For the lactation periods, the animals presented higher milk production in the first lactation period (13.27 kg-1). There was no effect of dietary supply levels, in different lactation periods, for fat content (3.34%), protein (3.41%), lactose (4.60%), total solids (12.0% ), defatted dry extract (8.80%), urinary nitrogen (14.5 mg dL-1) and somatic cell count (89.98 ml mL-1). It decreased the sum of saturated fatty acids in milk and increased that of monounsaturated fatty acids as it reduced levels of dietary supply. The rates of atherogenicity and thrombogenicity decreased with a reduction in supply levels and the desirable fatty effects showed an increasing linear effect with a decrease in supply levels. The cooling of the diet supply to 2% of the F1 Holstein cow weight x Zebu did not alter a physical-chemical physics of milk and improved the quality of milk fat from the point of view of human nutrition. These have been reducing the levels of saturated fatty acids, increasing the concentration of desirable fatty acids and increasing the relationship between hypo and hypercholesterolemic fatty acids.