Lipid composition of covering and intramuscular fat in pigs at different slaughter age

To study age-related variations in fatty acid composition of covering and intramuscular fat (IMF), 60 half siblings, Pic X Camborough, of the same age, 30 barrows and 30 gilts, chosen from 10 litters were used. Groups of 20 subjects each, 10 castrated males and 10 females, balanced for litter, were sacrificed at 6, 8.5 and 9.5 months of age, corresponding to the common slaughter age of the three Italian pig production types, at live weights averaging approximately 90, 145 and 160 kg, respectively. Samples of backfat and longissimus thoracis (LT) muscle, taken at the last rib, were analysed. On LT samples, moisture, fat content and drip loss were determined. Fatty acid composition was determined in lipids from subcutaneous adipose tissue and in lipid fractions from LT. Further, backfat lipids were submitted to iodine value (I. V.) determination. The data were evaluated by means of analysis of variance with age at slaughter and sex as the independent variables. As age increased (6, 8.5 and 9.5 months), higher contents of saturated fatty acids (SFA) (36.36, 39.08 and 39.19%, respectively; P<0.01) and monounsaturated fatty acids (MUFA) (41.78, 43.44 and 44.37%, respectively; P<0.01) were observed in backfat, whereas polyunsaturated fatty acids (PUFA) content, PUFA/SFA ratio and I. V. lowered (P<0.01). As total IMF is concerned, by increasing age, MUFA content increased (43.30; 46.76 and 47.28%, respectively; P<0.01), PUFA content decreased (18.63, 15.14 and 14.82%, respectively; P<0.01) and PUFA/SFA decreased as well (P<0.05); neutral lipids followed the same pattern, while an opposite trend was observed in polar lipids. IMF content (1.65%) was modified neither by sex nor age. The study shows that fatty acid composition of subcutaneous and intramuscular fats differs among the 3 slaughtering ages typical of the Italian pig industry. The variations observed, which could be ascribed to the increase of carcass fatness at increasing slaughter age, can affect both the nutritional and technological quality of pork.