Variations de la composition des dépôts lipidiques chez les bovins

Abstract

Variation of lipid composition of adipose tissues and muscles in cattle. The fatty acid (FA) contents of adipose tissues and muscles influence the characteristics of meat quality. The main causes of variation in the fatty acid composition has been studied in cattle by meta-analyse of data from the literature. The lipid content of muscle was influenced by the genotype and the level of energy intake. The increase in intramuscular fat content with age and fattening was mainly constituted of triacylglycerols (TG). The phospholipid (PL) content was nearly constant for one type of muscle. TG had higher contents in monounsaturated FA (MUFA) and saturated FA (SFA) (TG/PL = 1.9- 1.3 - 4.5 - 1.2 - 1.1, for MUFA, SFA, C14:0, C16:0 and C18:0, respectively) but had lower contents in polyunsaturated FA (TG/PL around 0.07 for PUFA). With diets including concentrate feed unsupplemented with fat, the adipose tissues and the muscles had lower contents of C18:0 and C18:3 but higher contents of C18:1 than with diets with forages only. Moreover, in intramuscular fat the PUFAn-6/PUFAn-3 ratio was lower with forage diets. Except for palm oil and cotton seeds, the vegetable fats produced adipose tissues with lower levels of SFA content than with animal fats. In adipose tissues, the PUFA levels were at their highest with linseed and with safflower. In the muscles, the variations in the C18:2 contents are influenced less when unprotected fat was added to the ration. Linseed produced the higher level of C18:3 than other added fats. Fish oils decreased C18:0 but increased PUFAn-3 contents in the muscle. The influence of a fat supplemented diet on FA composition of the muscles was different for TG and PL. Composition of total muscle lipids was thus influenced by the ratio of the two fat classes.