Fatty acid composition of lambs of indigenous dairy Greek breeds of sheep as affected by post-weaning nutritional management and weight at slaughter

Abstract

The objective was to assess the effect of breed, sex, post-weaning nutrition and weight at slaughter on the fatty acids (FA) composition in carcass fat of lambs of indigenous Greek dairy breeds of sheep, the Boutsko (B), Serres (S) and Karagouniko (K) breed. The lambs (weaned at approximately 42 days) had been reared under different conditions of housing and feeding in three consecutive experiments (Experiment). In Experiment 1, lambs ( n = 120) were individually penned and fed ad libitum on a concentrate feed (11.3 MJ metabolisable energy (ME)/kg DM and 192 g crude protein (CP)/kg DM) together with 100 g/day of Lucerne hay (8.3 MJ ME/kg DM and 182 g CP/kg DM). In Experiment 2, lambs ( n = 108) were fed the same concentrate on 3 different levels: High (H), Medium (M) and Low (L) and ad libitum on Lucerne hay. In Experiment 3, lambs ( n = 108) were initially group fed indoors for 63 days on 3 different levels of concentrate (H, M and L) together with ad libitum Lucerne hay. Thereafter they were finished on irrigated, sown pasture. Lambs were slaughtered at one of 5 standard proportions of mature weight (PMW) for each breed in Experiment 1 (i.e. 0.20, 0.30, 0.45, 0.60 and 0.90); at 3 fixed live weights in Experiment 2 (TSLW; i.e. 23, 28 and 33 kg) and at 3 fixed PMW in Experiment 3 (PMW; i.e. 0.20, 0.48 and 0.54). The right hand side of their carcasses was minced and a random sample, around 200 g, was taken. It was freeze-dried and then grounded to obtain a quantity of 2 g for lipid extraction and preparation of fatty acid methyl esters, which were assayed by gas-liquid chromatography to identify. Results were analysed separately for each experiment by analysis of variance. In Experiment 1, breed of lambs had significant effects ( P < 0.001) on C14:0, C16:0, C17:0, C18:2, C18:3 and C18:1 ( P < 0.05), whereas sex affected only the percentage of C15:0, C16:1 ( P < 0.001), C18:0 ( P < 0.01) and C18:2 ( P < 0.05). Live weight of lambs at slaughter had significant effects ( P < 0.05–0.001) on all the fatty acids. In Experiment 2, with the exception of C18:0 and C20:0, all other fatty acids were significantly affected by Breed ( P < 0.05–0.001). However, only C17:0, C18:0, C18:1 and C18:2 were significantly ( P < 0.001) affected by the level of concentrates in the diet. The major finding in Experiment 3 was the trend for saturated fatty acids to be lower; possibly due to the fact that lambs finished at pasture. It is concluded that there are possibilities of modifying FA composition in carcass fat of lambs by manipulation of post-weaning nutrition and slaughtering them at a wide range of live weights.