Lipid digestion in ruminants

Abstract

Lipid digestion in ruminants presents a renew of interest because of the presence of fatty acids (FA) having an influence on the technological and nutritional properties of their products. These aspects are mainly the out come of the hydrogenation and isomerisation of the FAin the reticulo-rumen. Micro-organisms of the rumen, particularly the attached bacteria, are richer in FA than the offered diets. The FA composition of microbes is characterised by molecular diversity (more than 50 FA) and a high content in C16:0 and particularly C18:0. The FA composition can be influenced by dietary effects: concentrate contents of the diet and FA composition when the diet is supplemented with lipids. The duodenal flow of FA (Y), expressed in % of dry matter intake (DMI) is highly correlated with the ingested flow of FA (X, % DMI) :Y = 0.83 X + 0.84 (n = 116, R2 = 0.94, rsd = 0.54). Lipid digestion also depends on the level of the microbial synthesis in the rumen. About2/3 of the double bonds of the ingested FA are hydrogenated in the reticulo-rumen. The intensity of this hydrogenation decreases with diets rich in concentrate and having a high level of intake. The intestinal digestibility of FA ranges between 65 and 75 % approximately. The type of fat supplementation can influence this digestibility. The data and equations provided in this paper allow to predict the absorbed flows of the major FA in ruminantsand to formulate diets on this basis.