~~Fat digestion and metabolism differ widely between animal species. In ruminants, dietary fats are hydrogenated in the rumen before intestinal absorption so that absorbed fatty acids (FA) are more saturated than dietary FA. In non-ruminants, intestinal FA digestibility depends on the level of saturation of dietary FA. Fat supplementation of the diet of cows decreases milk protein and has a variable effect on milk fat, depending on the source of dietary lipids. When encapsulated lipids are used, the linoleic acid content of milk is increased, but the organoleptic quality of milk may be altered. Supplementary lipids are incorporated into non-ruminant body fat, whereas de novo lipogenesis is reduced. There is a close relationship between the nature of dietary FA and nonruminant body FA.
Lipids: Fat digestion: Fat metabolismFats are present in small amounts (less than 5Ogkg DM) in most natural feedstuffs available for animal feeding, except oilseeds. However, supplemental fats are used in diets for nutritional or economic reasons in order to increase the level of fat in diets. Due to their high energy value, fat supplements may contribute to meeting the energy requirements of animals; furthermore, it may be cheaper in some circumstances to provide energy as fat rather than carbohydrates. It is often questioned whether the dietetic value and/or the quality of products, especially milk and meat, are altered by fat supplementation. The answer evidently depends on the type of production. The action of dietary fat is highly dependent on the animal species. Due to digestive and, to a lesser degree, metabolic utilization, the relationships between fat in the diet and fat in the products are different in single-stomached animals and in ruminants, in young and adult animals. In the present article some viewpoints on the digestion and the metabolic utilization of fats are developed in ruminants, and outlined in pigs and poultry. The main consequences in terms of chemical composition and quality of milk and meat are given in the last sections.
TRANSFORMATIONS AND ACTIONS OF DIETARY FATS IN THE RUMENThe digestive utilization of fats by ruminants is characterized by events in the rumen before they are absorbed in the intestine. During their stay in the rumen, fats are transformed so that the amount and composition of fat leaving the rumen differ from intake. Moreover, fat has negative effects on ruminal activity, mainly on carbohydrate degradation. In this section, the main features of fat metabolism and interaction with carbohydrate digestion are presented. The interaction between fat and N metabolism, of moderate magnitude is not treated here.
Lipolysis and hydrogenation, synthesis and incoiporation of fatty acids by bacteriaDietary lipids are extensively hydrolysed in the rumen, by microbial enzymes originating first from different classes of bacteria (of which the best known is Anaerovibrio Zipolytica), https://doi
