Physical and chemical composition of the carcass of three different types of pigs grown from 25 to 115 kg live weight

A total of 74 pigs representing three commercially available crossbred types, Landrace (50%), Pietrain (50%) and Meishan (25%), were given food ad libitum over a 25to 115-kg growth period and serially slaughtered for physical and chemical analysis in five groups at 32, 42, 63, 82 and 114 kg live weight (W). Results are presented in the order of pig type as above. Pig types grew at similar overall rates of live body gain, but the Meishan type ate more food and had greater back fat depth. The Pietrain type was least fat. Dissected fatty tissue grew substantially faster than the carcass as a whole; allometric exponents being 1·64, 1·34 and 1·52 ( P < 0·05) for the Landrace, Pietrain and Meishan types respectively. Dissected lean tissue gains were 0·419, 0·427 and 0·308 kg daily ( P < 0·01), and dissected fatty tissue gains were 0·251, 0·158 and 0·218 kg daily ( P < 0·05); the Meishan type being slowest for lean gain and the Pietrain type slowest for fatty tissue gain. The Pietrain type had the largest crosssectional area of the longissimus dorsi muscle, and the Meishan type the smallest. The pelvic limb of the Meishan type lost density (as measured by specific gravity) fastest, and that of the Pietrain slowest as the pigs grew. The Meishan type had a lower proportion of its carcass lean and a higher proportion of its carcass fat in the pelvic limb than did the other two types. For each kg of live-weight gain, 0·037, 0·041 and 0·032 kg ( P < 0·05) of chemical protein was deposited in the pelvic limb of the three types respectively. Equivalent values for chemical lipid were 0·041, 0·035 and 0·041 ( P < 0·05). The Meishan type retained protein at a relatively slower rate in the pelvic limb than in the body as a whole. The Pietrain type had the greatest ultimate protein mass in the pelvic limb. Estimation of whole body protein content as a linear function of pig live weight gives coefficients of 0·154, 0·178 and 0·168 kg ( P < 0·05) for the three types respectively. Equivalent values for whole body lipid content were 0·269, 0·214 and 0·274 ( P < 0·05). Best estimates of the daily rates of protein retention in the body of the whole live pig were 0·152, 0·197 and 0·142 kg/day for the Landrace, Pietrain and Meishan types respectively.