Effect of nutritional factors on fatty acid composition of lamb fat deposits

A literature review was made of the influence of nutritional factors on the fatty acid composition of fat deposits and muscles of lambs. A bibliographic data base, containing 979 observations from 108 papers, was made up in such way that one observation corresponded to one group of lambs in one experiment. Each nutritional factor was studied only when number of observations was sufficient. Consequently, special emphasis was given to the effect of dietary ingredients supplying energy or nitrogen on the fatty acid composition of subcutaneous (SC) and perirenal adipose (PR) tissues and in muscles of lambs. Regardless of sex, breed and breeding conditions, all the tissues examined showed a similar pattern of modification in fatty acid composition with diets. In milk fed lambs the pattern of fatty acids largely reflected the dietary fat pattern. The fatty acid of stored fats before weaning had an influence on fatty acid composition of fat deposits and muscle, several months after weaning. When the diets were rich in beet pulp or in fish meal the proportion of C-18:1 was significantly increased and the proportions of C-18:0, C-18:2 and C-18:3 decreased in fat tissues. Inclusion of maize in diet resulted in an increase in linoleic acid content in fat deposits. Inclusion of cotton meal increased linoleic and stearic acids in fat deposits. Grass-based diets increased C-18:0 and C-18:3 in lamb tissues. Melting point of both SC and PR were strongly associated with differences in C-18:0 percentages. This approach underlined difficulties in understanding the diet effects on fatty acid composition of fat deposits and muscles without taking feeding and other management aspects into account. This study supported the extent to the modification of the fatty acid composition of lamb carcasses by choice of dietary ingredients despite the ruminal hydrogenation of dietary fat.