Effect of age, physiological state and nutrition on fatty acid composition in depot fat and ruminal volatile fatty acids in sheep

Two experiments were carried out with male lambs and hoggets of the semi-fine fleeced breed. Experiment I: after weaning at age 45 days, two groups of lambs received diets of different energy (4.1 and 6.0 MJ kg(-1) diet) and protein (130 and 200 g kg(-1) diet) content for 120 days. Experiment II: two groups of hoggets (uncastrated and castrated) from 10 to 18 months of age were fed diets similar in energy and protein to the control group of Experiment I (4.1 MJ kg(-1) diet and 130 g kg(-1) diet, respectively) but of different ingredient composition. With increasing energy and protein in the diet (Experiment I), total unsaturation increased in the adipose tissue of lambs. Similar results (decrease of C18:0, increase of C18:1) were obtained by changing the ingredient composition of the diet (replacement of corn and sunflower meal with urea), but at constant energy and protein levels. Castration did not induce marked changes in composition of subcutaneous and perirenal adipose tissue triacylglycerols. Subcutaneous adipose tissue, regardless of age, castration and diet was not homogeneous in fatty acid composition. Profiles of volatile fatty acids depended on the energy-protein content of diet, but not on its ingredient composition, or age and physiological condition of animals. The results of lipid composition of depots from both experiments were a good base for seeking suitable diets for fattening of lambs and hoggets.