Effect of dietary propionate on intake patterns and fatty acid composition of adipose tissues in lambs

The aim of the present trial was to study the effect of dietary propionate supplementation on growth performance, intake patterns and on the proportion of odd-numbered and methyl-branched chain fatty acids in internal or in subcutaneous adipose tissues. These fatty acids are responsible, in part, for abnormally soft subcutaneous adipose tissue. Eleven male lambs were fed ad libitum carbohydrate-rich diets based mainly on barley, supplemented (P diet) or not supplemented (C diet) with 5.6% DM of sodium propionate. During the trial, the intake patterns were recorded on three non-consecutive days over a 9h-period. The fatty acid compositions of four adipose tissue sites, two subcutaneous (dorsal, caudal) and two internal (omental, perirenal) were analysed. The ME intake (3.32+/-0.44Mcal per day) and average daily gain (316+/-64g per day) were not different (P>0.10) between the C and P treatments. The intake patterns of these lambs given ad libitum access to feed did not show any large meal even after the morning distribution of feed. No differences in intake patterns were observed between the two diets. The dietary propionate supplementation increased (P<0.05) the proportion of odd-numbered fatty acids (Odd FA) in both internal (increase of 0.7wt.% of total fatty acids) and subcutaneous adipose tissues (increase of 1.7% of total fatty acids). The effect of dietary propionate supplementation on branched-chain fatty acids was less conclusive although it tended to increase (P=0.09) the proportion of branched-chain fatty acids other than the iso and anteiso fatty acids (BCFAO) in dorsal adipose tissue. This experiment confirms the role of propionate as an important precursor of odd-numbered and methyl-branched chain fatty acids. Moreover, the dorsal adipose tissue seems to be the most sensitive adipose tissue to dietary increment in ruminal propionate content. A positive relationship between the mean ME intake rate measured over 8.5h and the proportions of Odd FA and BCFA in dorsal adipose tissue was shown. However, it does not appear to play a predominant role in the explanation of the individual variability in dorsal fatty acid composition.