Plasma insulin, metabolite concentrations, and carcass characteristics of Japanese Black, Japanese Brown, and Holstein steers.

To characterize some of the physiological features of Japanese beef breeds, plasma concentrations of insulin and metabolites and carcass composition were measured in five Japanese Black, five Japanese Brown, and four Holstein steers (6.2 mo; 164 kg). The steers were raised under typical feeding conditions in Japan until they were slaughtered at 600 to 700 kg BW. Blood samples were collected at 8 mo of age (average BW, 194 kg) and at 300, 400, 500, and 600 kg BW. Plasma insulin concentrations increased with BW in all three breeds and were greater (P < .05) in Japanese Blacks than in the Japanese Browns or Holsteins at 400 and 600 kg BW. The Japanese Blacks exhibited lower (P < .05) plasma glucose levels at 300, 400, and 600 kg BW compared with Holsteins. Regardless of the breed, plasma urea nitrogen (PUN) concentrations increased with BW. The two Japanese breeds had greater (P < .05) PUN levels than Holsteins at 300 and 600 kg BW. Total cholesterol and phospholipid concentrations tended to decrease above 300 kg BW in the Holsteins; however, the concentrations of both metabolites were elevated in the steers of Japanese breeds at 500 and 600 kg BW (P < .05). Breed did not affect the plasma concentrations of albumin, triglycerides, and NEFA. The Japanese breeds had higher (P < .01) dressing percentage, greater (P < .05) carcass fat proportion, and a lower proportion of carcass bone (P < .01) than the Holsteins. These results indicate that there are breed differences in plasma levels of insulin and certain metabolites and carcass composition among Japanese breeds and Holstein.