The use of stoned olive cake and rolled linseed in the diet of intensively reared lambs: effect on the intramuscular fatty acid composition

The aim of the present study was to evaluate the effect of the inclusion of stoned olive cake and rolled linseed in a concentratebaseddiet for lambs on the fatty-acid composition of polar and non-polar intramuscular lipids of the longissimus dorsi muscle.To achieve this objective, 32 Appenninica lambs were randomly distributed into four groups of eight lambs each and were fedconventional cereal-based concentrates (diet C); concentrates containing 20% on a dry matter (DM) basis of rolled linseed(diet L); concentrates containing 35% DM of stoned olive cake (diet OC); and concentrates containing both rolled linseed(10% DM) and stoned olive cake (17% DM; diet OCL). The concentrates were administered together with grass hay at a 20 : 80forage : concentrate ratio. Growing performances and carcass traits were evaluated. The fatty-acid composition was analysed in thetotal intramuscular lipids, as well as in the polar and neutral lipids. The average feed intake and the growth performance of lambswere not affected by the dietary treatments, as a consequence of similar nutritional characteristics of the diets. The inclusion ofrolled linseed in the L and OCL diets increased the content of C18:3 n-3 in intramuscular total lipids, which was threefold higher inmeat from the L lambs and more than twofold higher in meat from the OCL lambs compared with the C and OC treatments. Then-6 : n-3 ratio significantly decreased in the meat from lambs in the L and OCL groups, reaching values below 3. The L treatmentresulted in the highest level of trans-18:1 fatty acids in the muscle. Regardless of the dietary treatment, the t10-18:1 was the majorisomer, representing 55%, 45%, 49% and 45% of total trans-18:1 for C, L, OC and OCL treatments, respectively. Neutral lipidsfrom the OC-fed lambs contained the highest amount of c9-18:1 (more than 36% of total fatty acids); however, the content ofc9-18:1 did not differ between the OC and C lambs, suggesting an intensive biohydrogenation of dietary c9-18:1 in the case ofOC treatment. The highest content of c9,t11-18:2 was detected in the intramuscular fat from the L-fed lambs, followed by theOCL treatment. A similar trend was observed in the neutral lipid fraction and, to a lower extent, in the polar lipids.