Abstract
The present study was conducted to clarify the changes of calpain and calpastatin activities in skeletal muscle as a function of growth rate at advancing age of commercial chickens, using male broiler and layer chickens of 2, 4, 6, and 8 weeks of age. The body weight of broilers were significantly greater than those of layers (P<0.01). The fractional growth rates during the period of 0∼2, 2∼4, 4∼6 and 6∼8 weeks of age were also significantly greater for broilers than for layers (P<0.01). Calpain and calpastatin activities were decreased with advancing age in both broiler and layer. Statistically significant differences (P<0.01) in calpain and calpastatin activities (units/g muscle and units/mg extractable muscle protein) between broiler and layer chickens were observed. The broiler has lower calpain activity than the layer, but higher calpastatin activity than layer during the entire period of the investigation. The rates of change with age in calpain activity and calpastatin activity showed the same trends in both breeds. The differences of the activities observed between broiler and layer chickens might be due to the different breeding methods. The differences in calpain and calpastatin activities at different age of broiler and layer chickens in the present study suggest that the regulations of proteolytic enzyme activity in muscle are related to the aging and genetic factor of breed.
