Effect of genotype, feeding system and slaughter weight on the quality of light lambs

One hundred and eight Merino Branco and crossbred Ile de France×Merino Branco ram lambs were used to evaluate the effects of genotype, feeding system and slaughter weight on fatty acid composition of meat (longissimus thoracis muscle). At 60 days of age, lambs were assigned to the experimental feeding systems: P—pasture with dams; SP—pasture with dams, plus concentrate ad libitum; C—weaning and concentrate ad libitum. Lambs were slaughtered at 24 and 30 kg live weight. The meat had a low fatty acid content. Intramuscular fatty acid (FA) composition was not affected by genotype. Pasture raised lambs (P and SP) showed higher proportion of n-3 FA, conjugated linoleic acid (CLA) and trans-octadecenoic FA, and lower n-6:n-3 ratio, than C lambs. When slaughter weight increased, total FA content increased. Palmitic acid and monoenoic FA increased and polyunsaturated FA decreased with slaughter weight. The CLA proportion increased with slaughter weight, but only for lambs raised on pasture (P and SP). Fatty acid profile was effective in the identification of lamb feeding systems.