Própolis e vitamina E na dieta de vacas leiteiras suplementadas com óleo de linhaça sobre a qualidade e funcionalidade do leite

Abstract

Studies were carried out to evaluate a propolis extract as a source of antioxidants for dairy cows. In the first experiment a propolis extract was incubated with microbial population from dairy cows to determine, in vitro, its influence on fermentation and gas emission. Propolis extract was used in doses: 1.1, 2.2, 6.7, 11.1, 16.7, 22.2, 27.8, 38.9, and 55.6 ug/mg of substrate. Propolis extract linearly reduced the final pH of the medium and linearly increased propionate production. In a linear form, use of propolis extract reduced methane production and increased carbon dioxide production at five and 24 hours of fermentation. In the second experiment, a propolis-based product and vitamin E were supplemented, in association or not, in diets with flaxseed oil to dairy cows to determine the effects on digestibility and nutrient utilization. Four Holstein cows with rumen cannula, averaging 584 ± 52 kg body weight and 90 ± 39 days in milk were used in a Latin square design 4 × 4, with four treatments and four periods. Experimental diets were: 1) control diet; 2) diet with flaxseed oil, 25 g/kg DM; 3) diet containing flaxseed oil + propolis-based product, 1.2 g/kg DM; 4) diet containing flaxseed oil + propolis-based product + vitamin E, 375 IU/kg DM. Supplying propolis-based product in association or not with vitamin E had no effect on intake and ruminal and total tract digestibility of the diet. Rumen pH, ammonia nitrogen content, rumen microbial production, efficiency of microbial synthesis and excretion of nitrogenous metabolites were not altered by diets. In the third experiment, propolis-based product and vitamin E, in association or not, were added to diets containing flaxseed oil to dairy cows in order to assess the influence on blood parameters, blood lipid peroxidation, milk chemical composition, fatty acid composition and antioxidant quality of milk. Animals and treatments were the same as in the second experiment. Propolis-based product associated or not to vitamin E in diets caused a decrease in blood concentrations of total cholesterol, HDL and blood lipid peroxidation. Providing propolis extract with or without vitamin E to cows had no effect on milk yield and composition. Addition of Propolis-based product in diets elevated concentrations of FA 18:1 and cis9, trans11 18:2, and also the total CLA concentration in milk. Association of propolis extract and vitamin E in diets also caused an increase on milk CLA content. Total polyphenols concentration in milk was increased by using propolis extract isolated or with vitamin E in diets. Propolis-based product provided higher antioxidant activity of milk by the reducing power method. Providing propolis extract combined or not to vitamin E did not improve the oxidative stability of milk. In the fourth experiment, a milk naturally enriched with polyunsaturated fatty acids and antioxidants, by feeding the cows and obtained in the third experiment, was supplemented to growing rats in order to verify the milk functionality on health of these animals. Forty male Wistar rats presenting 21 days-old were used in a completely randomized design, with experimental period of 85 days. Supplementation was performed by gavage at dose 0.005 mL/kg body weight. Experimental groups were: control with water, common milk, PUFAenriched milk, and PUFA and antioxidants-enriched milk. The supply of milk enriched with PUFA and antioxidants to rats did not modify the feed intake, digestibility, blood glucose, blood antioxidant capacity, organs weight and growth of rats. Supplementation with this milk moderately elevated blood concentrations of total and LDL cholesterol and significantly increased the accumulation of visceral adipose tissue. Propolis showed being a good source of phenolic compounds for dairy cows not influencing digestion and nutrient utilization of diet, with improvement of fatty acid composition and antioxidant content of milk. Milk rich in polyunsaturated fatty acids and antioxidants did not modify the rat growth, although a higher accumulation of visceral adipose tissue was observed.