Age at the beginning of the fattening period of Iberian pigs under free-range conditions affects growth, carcass characteristics and the fatty acid profile of lipids

This work studies the effect of starting age of the fattening period on productive traits and fatty acid (FA) composition of backfat (BF) of Iberian pigs. Three groups of eight Iberian barrows (body weight 101.25 ± 2.8 kg) started the fattening period at 14 (P14), 12 (P12) and 8 (P8) months of age. During the pre-fattening period pigs received 1.3, 1.5 and 2.5 kg/day of a commercial feed (for P14, P12 and P8, respectively). The P8 pigs showed lower slaughter weight, average daily gain (ADG), carcass weight, carcass outer length, backfat thickness and ham length than P14 and P12 pigs. In the subcutaneous outer backfat layer P14 pigs had significantly higher proportion of oleic acid (C18:1 n-9) (P<0.05) than P12 pigs. The subcutaneous inner backfat layer of P8 pigs had higher proportions of palmitic acid (C16:0), stearic acid (C18:0) and total saturated FA (SFA) and lower of C18:1 n-9, linoleic acid (C18:2 n-6), total monounsaturated FA (MUFA), total polyunsaturated FA (PUFA), total n-6 PUFA (n-6) and total n-3 PUFA (n-3) than P14 and P12 pigs. Finally, in the subinner backfat layer, P8 pigs had higher proportions of C16:0 and total SFA and lower of C18:2 n-6, C18:3 n-3, total PUFA, total n-6 and total n-3 than P14 and P12 pigs. In neutral lipids (NL) from intramuscular fat of Longissimus dorsi muscle, P8 pigs showed higher proportion of C16:0, C18:0 and total SFA and lower of C18:1 n-9, C18:2 n-6, total MUFA, PUFA and n-6 than P14 and P12 pigs. Polar lipids (PL) from P8 pigs showed higher proportions of C16:0, total SFA and lower C18:3 n-3 than those from P14 and P12 pigs. Hepatic NL of P8 pigs showed higher proportions of C18:0 and total SFA than P12 and P14 pigs. No differences on hardness, adhesiveness and chewiness of the inner subcutaneous backfat layer were observed among treatments. However, cohesiveness was lower in P8 than in P14 pigs and gumminess was lower in P8 than in P12 or P14 pigs. Therefore, productive traits, carcass quality and fat quality characteristics of Iberian pigs starting the fattening with 8 months are worse than those from pigs starting the fattening with 12 or 14 months of age.