Effect of ractopamine on growth, carcass traits, and fasting heat production of U.S. contemporary crossbred and Chinese Meishan pure- and crossbred pigs1

Abstract

Twenty-four U.S. crossbred (Duroc x White composite; D x Wc; 83.9 kg), 24 purebred Meishan (M; 59.4 kg), and 24 Meishan x White composite crossbred (M x Wc; 83.4 kg) barrows were allotted within genotype to a 16% CP corn-soybean meal diet or this basal diet + 20 ppm of ractopamine and allowed ad libitum access to feed for 52 d. No genotype x ractopamine interactions were detected (P greater than .05) in pigs for growth, lean cuts, ham and loin characteristics, leaf fat and visceral organ weights, fasting whole-animal heat production, and carcass traits except longissimus muscle area (LMA). The LMA was increased by ractopamine in D x Wc and M x Wc pigs (P less than .05) but not in M pigs. Compared with D x Wc and M x Wc pigs, M pigs had lower ADG, ADFI, and gain to feed ratio (G/F), shorter carcasses, and lower dressing percentage, LMA, predicted amount of muscle, weights of trimmed picnic, loin, and ham cuts, percentage of ham lean, and CP in ham lean, but heavier liver, kidneys, pancreas, and entire gastrointestinal tract with greater percentage of ham fat and ham bone (P less than .05). The M x Wc pigs had lower ADG, G/F, dressing percentage, LMA, amount of muscle, weights of trimmed cuts, and percentage of ham lean but heavier lungs, pancreas, stomach, and large intestine than did D x Wc pigs (P less than .05). Supplemental ractopamine increased ADG, G/F, dressing percentage, amount of muscle, trimmed loin weight, percentage of ham lean, and CP in ham lean and decreased weights of heart, lungs, kidneys, and pancreas in pigs (P less than .05). Neither genotype nor ractopamine had any effect on 4- to 24-h postprandial whole-animal heat production of pigs (P greater than .05). These results indicate that ractopamine will improve growth performance and carcass leanness in pure- and crossbred Meishan pigs.

The cellularity of developing adipose tissues in Pietrain and Meishan pigs

“…The activity of enzymes for lipid synthesis shows maximal values between 40 and 60 kg body weight in fast growing pigs, with marked differences according to the anatomical localization of the fat depot and breeds (Hood and Allen, 1973). Pietrain, which is recognized as one of the leanest breeds (Bidanel et al, 1994) and Meishan, which exhibits one of the highest degrees of adiposity (Yen et al, 1991 (Mersmann et al, 1976;Henry, 1977 (Camara et al, 1994 (Hausman and Martin, 1981) and the same is true for Large White pig compared to Pietrain (Moody et al, 1978). Later in life, after 45 days, the adipocyte size in Meishan pig is larger than that of Large White (Camara et al, 1994 Lee and Kauffman, 1974;Hood and Allen, 1977;Moody et al, 1978) and was observed also in bovine species (Chakrabarty and Romans, 1972;Lin et al, 1992 (Chora et al, 1995).…”

Effect of ractopamine on whole body and splanchnic energy metabolism in Holstein steers

“…Williams et al (1987) reported a reduction in liver size (P B0.05) in veal calves fed cimaterol. Pigs fed ractopamine also showed decreased weight (P B0.05) of heart, lung, kidney and pancreas (Yen et al 1991). As organs have considerably higher metabolic rates than skeletal muscle and account for 30(60% of whole body energy needs (Reynolds et al 1991), this tendency for a reduction in visceral organ mass may offset the increased heat production that would normally be associated with bAR agonist treatment, as a result of increased muscle mass and weight gain, thus accounting for the lack of change in heat production values seen in the current experiment.…”

Effect or ractopamine on growth and body composition of pigs during compensatory growth

“…It is unlikely that the reduction in the efficiency deposition associated with ractopamine treatment was the result of an increase in basal metabolic rate. Yen et al (1991) reported that it had no effect on postprandial whole-animal heat production in pigs. Also, a study by Ferná ndez et al (1998) found that salbutamol did not alter energy metabolism in swine and concluded that the detected differences in energy retention were a consequence of the modified protein and fat deposition pattern.…”