Nutritional quality indices of milk fat from goats on diets supplemented with different roughages

The experiment was conducted to evaluate the nutritional indices of milk fat of 1/2 Boer x Saanen goats on diets supplemented with three roughages. Eighteen goats under a semi-intensive system were divided into groups, and fed an ad libitum supplement of sorghum silage, maize silage or mulberry hay. Nutritional indices were determined from three milk samples taken during winter (August) and spring-summer (average of November and December). Using mixed statistical models, the animal error was computed as a random effect. The season and supplement were fixed. The winter season was markedly better for all variables (P < 0.01), while short-chain fatty acids did not change (P > 0.05). Interactions only occurred between the thrombogenic index and the C12:0/C10:0 ratio, where the higher values that are potentially more harmful to human health were obtained in the spring-summer season in animals fed maize silage, followed by the averages of other treatments during the same season. The values for unsaturated fatty acids, atherogenic index and thrombogenic index indicated differences between supplements, with better values for goats fed with sorghum silage and mulberry hay. Grazing Boer x Saanen goats supplemented with mulberry hay or sorghum silage provided milk with better lipid indices for the prevention of human coronary diseases. (C) 2011 Elsevier B.V. All rights reserved.