BODY-COMPOSITION, INVITRO LIPID-METABOLISM AND SKELETAL-MUSCLE CHARACTERISTICS IN FAST-GROWING, LEAN AND IN SLOW-GROWING, OBESE PIGS AT EQUAL AGE AND WEIGHT

Abstract

Eight slow-growing feral, obese (Ossabaw) pigs were sacrificed at 45 kg live wt and an average age of 170 days and were compared with a group of fast-growing, lean (Yorkshire) pigs fed the same ration and sacrificed at either 45 kg (average age, 130 days) or at 170 days (average live wt, 90 kg). Body composition and various carcass measurements, in vitro adipose tissue metabolism and muscle composition were measured. At equal weight, the obese pig had a greater percent body fat (40 vs. 23%) and backfat thickness (3.3 vs. 2.0 cm) than the lean. At equal age, the difference in percent body fat was not as great (40 vs. 31%): backfat thickness was equal. Percent body protein was greater in the lean pigs at either equal weight or equal age. In vitro lipolysis, per 100 mg adipose tissue, was lower in obese pigs than in lean pigs at equal weight. Obese tissue exhibited a greater lipolytic response to DBcAMP [dibutyryl cyclic AMP] stimulation than adipose tissue from lean pigs at equal weight; basal lipolysis per total fat mass was similar. At equal age, no differences in lipolysis between lean and obese pigs were observed. When compared at either equal age or equal weight, weight of semitendinosus muscle, and measurements of muscle RNA and DNA were greater in lean compared to obese pigs. RNA/DNA ratios were similar at equal weight and age: the protein/DNA ratio was lower in lean muscle compared to obese at equal weight. The decreased protein deposition in the obese, slow-growing pigs appeared due to fewer muscle nuclei rather than a decreased cellular capacity for protein synthesis.