Digestion and metabolism of dietary fat in farm animals

Abstract

~~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

Use of re-esterified palm oils, differing in their acylglycerol structure, in weaning-piglet diets

“…As expected, unsaturated FA were better absorbed than were SFA, and stearic acid was less well absorbed than was palmitic acid, because as unsaturation increases, digestibility is increased, and as the FA chain length increases, digestibility is reduced (Doreau and Chilliard, 1997). In this sense, SN, due to its high unsaturated FA content, showed the greatest total FA apparent absorption and, therefore, the greatest digestible energy.…”

Animal performance and meat characteristics in steers reared in intensive conditions fed with different vegetable oils

“…Moreover, no differences (P > 0.05) were found in carcass weight, conformation, fatness or pH 24 h after slaughter (Table 3). It is generally accepted that including unsaturated fats in ruminant rations leads to a decrease in the digestion of structural carbohydrates in the rumen, and that the reduction is less when protected fats are used, such as calcium soaps or hydrogenated fats (Doreau and Chilliard, 1997). A lower productive output with the SOY treatment, compared with PALM and OLI, was therefore to be expected.…”

“…In a review of data on the use of fats in steer fattening, Clinquart et al (1995) found that incorporation levels below 5% do not affect ruminal digestion or productive output, irrespective of the type of fat used or how the fats are pre-treated. Doreau and Chilliard (1997) indicated that the reduced digestibility of organic matter when unsaturated fats are added is due to a poorer utilisation of the fibrous fraction, without modification of starch digestion. It has been demonstrated that lipids have a negative effect on bacterial growth.…”

Methane production and diurnal variation measured in dairy cows and predicted from fermentation pattern and nutrient or carbon flow

“…Hydrogen was assumed to be produced when OM was fermented to Ac and Bu, and used during production of Pr and Va. Since two of the three trials used high-fat diets and the FA concentration varied substantially between diets, the amount of H 2 available for CH 4 production was corrected for biohydrogenation, assuming hydrogenation rates of 75% for C18:1, 80% for C18:2 and 92% for C18:3 (Weisbjerg et al, 1992;Doreau and Chilliard, 1997). After this correction, it was assumed that all residual H 2 was converted to CH 4 (i.e.…”