Twin Production by Embryo Transfer in Japanese Black-Holstein Crossbred Cows
Calving traits, postpartum reproduction and growth of calves in 28 Japanese Black-Holstein crossbred cows pregnant with twins including 3 cows with triplets by embryo transfer were compared with the data of 60 crossbred cows pregnant with single calves. After calving, all the cow-calf pairs were fed mainly roughage, grazed on pasture during summer and fed with grass silage during the winter season. No concentrate supplement for calves was given. Gestation length of cows giving birth to twins and calf birth weight were shorter by 8 days and lighter by 6 kg compared with cows giving birth to single calves, respectively. Significantly (P < 0.01) more cows giving birth to twins required assistance and retained placenta compared with cows giving birth to single calves. Twenty-five percent of all the cows that produced twins still gave birth to one calf or twin calves. In cows nursing twins, postpartum days to first ovulation and first estrus were significantly (P ＜ 0.01) longer compared with the cows nursing single calves. However, the interval between postpartum and conception and the number of embryo transfers (inseminations) required for conception were not different between the 2 groups. Daily gain (DG) of twin calves from birth to 90 days of age was significantly (P ＜ 0.01) lower than that of single calves, but DG from 90 to 180 days of age did not differ. At weaning after 180 days of age, body measurements of twin calves were 92-97% of those of single calves except for the body weight which was 82% of that of single calves. After all the 48 calves were produced (171%) and raised to weaning from 28 cows giving birth to twins, cows raising twins produced 136 kg more total weaning weight than did cows raising single calves. The results obtained in this study indicate that twin production by embryo transfer to the crossbred cows is efficient for beef production, although a relatively higher incidence of neonatal calf death was recorded.
|作成者||Osamu SUZUKI Mari AOKI Koji KIMURA|