[Factors of variation in the fatty acid composition of cow milk fat]
1996
Perdrix, M.-F. | Sutter, F. | Wenk, C. (Ecole polytechnique federale de Zurich, Zurich (Switzerland). Institut des sciences animales, Groupe alimentation)
Milk fat contains a number of different fatty acids. Ten acids with four to 18 carbon atoms chain length and three unsaturated acids with 18 carbon atoms constitute more than 90 % of the total fatty acids. The content of fat and the composition of fatty acids in the milk are influenced by many factors, which are separated into three groups: 1) animal factor: genetic background, stage of lactation, race, and mammal infection; 2) environmental factor: method of production, milking, and season; 3) dietary factor: forage and concentrate mix, level of nutrition, concentration and nature of protein and fat in the diet. The fatty acids secreted by the mammal gland are of double origin. They either derive from circulating long-chained fatty acids or from the de novo synthesis from precursors with two or four carbon atoms within the mammal gland. This synthesis is very important to understand the influence of the diet on the composition of fatty acids in milk. The ingredients and the chemical composition of the diet affect significantly the composition of fatty acids in contrast to the protein and feeding frequency, which show hardly any influence. Supplemental vegetable fat increases the proportion of polyenic acid with 18 carbon atoms in a satisfactory way only if the fat is protected from ruminal biohydrogenation
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