Genetic Trends of Body Measurements and Reproductive Traits in a Japanese Black Cow Population

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  • 黒毛和種雌牛集団における体測定値および繁殖形質の遺伝的趨勢
  • Genetic Trends of Body Measurements and

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Abstract

A study was made to investigate the genetic trends of body measurements at registration and reproductive traits in a cow population of the Japanese Black. The data were collected from 14, 881 Japanese Black cows which were registered in 1991 and 1992. The body measurements analyzed were withers height, chest girth, chest depth, rump length, thurl width and body weight, while the reproductive traits were age at first calving, calving interval and gestation length. Breeding values of the cows and their dams were predicted by using an animal model with multiple-trait REML procedure. Average predicted breeding value (PBV) was calculated by year of birth of predicted animals in order to obtain the genetic trends for each trait. The results of regression analysis showed that the PBV of the cows born from 1975 to 1989 increased high significantly for withers height, chest girth, rump length and body weight, respectively, while the PBV of cows for chest depth tended to increase slightly. On the other hand, no change was found in the PBV of cows for thurl width. The PBV of the sires born from 1975 to 1987 for all body measurements had a tendency to fluctuate slightly. The PBV of cows for age at first calving and gestation length tended to increase slightly and significantly during the period of 1975 to 1989. There was no change in the PBV of the cows born from 1975 to 1989 for first calving interval. It may be concluded that the improvement strategy of placing an emphasis on carcass quality appears to have not given up to date any special bad effect on the genetic trends of body size and reproductivity in Japanese Black cows population.

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