Effect of different feeds on meat quality and fatty acid composition of lambs fattened at pasture.

Two kinds of feed (commercial concentrate vs whole supplemented barley) were compared in unweaned lambs and lambs weaned at 40 days of age, fattened at pasture and slaughtered at 28 kg live weight, in order to observe their effects on meat quality and fatty acid composition. The weaning status influenced fatness; unweaned lambs displayed a greater carcass fatness score and more kidney knob and channel fat than weaned lambs. Compared with the unweaned animals, weaned lambs exhibited higher pH values at 0 h and 45 min in the m. longissimus thoracis (LT) and at 45 min and 24 h in the m. semitendinosus. The redness index (a*) of the m. LT of weaned lambs was higher than that of unweaned lambs, and lambs fed concentrate displayed a higher yellowness index (b*) and a higher Hue value than those given whole barley. Water-holding capacity did not vary with the treatments studied. The proportion of saturated fatty acids (SFA) in intramuscular fat was higher (P⩾0.001) in unweaned lambs than in weaned ones while, on the other hand, the latter displayed a higher proportion of monounsaturated fatty acids (MUFA) and a higher n-6/n-3 ratio in the same tissue. As was the case with intramuscular fat, the subcutaneous fat of unweaned lambs exhibited higher proportions of medium-chain fatty acids (C12:0, C14:0 y C16:0) and lower ones of stearic (C18:0) and oleic (C18:1) fatty acids than that of weaned lambs. Higher levels of heptadecenoic acid (C17:1) were found in the subcutaneous fat of lambs fed whole barley than in that of lambs given concentrate. PUFA/SFA and n-6/n-3 ratios were lower in the m. LT than in the m. quadriceps femoris.