Abstract: In order to define the best superovulation program, the best month old of calves and the best repeated superovulation time interval, different superovulation programs were conducted on different months old calves (1~6 months old) in this study. The results showed that the superovulation program 4, of which the average number of eggs collected was 80.0 missiles, the average number of oocytes recovered was 43.3 missiles and the average number of eggs available was 37.8 missiles, were significantly higher than the other four programs (P<0.05). It suggested that program 4 was fitted for superovulation of 3 months old calves; program 4 was much better than other 4 programs in 2 months old, 3 months old, 4 months old, 5 month old calves with the average number of eggs of 33.5, 41.0, 34.5 and 32.8 missiles respectively, and the difference between each other was not significant. The results of 1 month and 6 months old calves with the average number of available eggs of 10.8 and 18.3 missiles was significantly lower than the other four age groups (P<0.05), it suggested that the superovulation treatment program 4 was most suitable for 2 to 5 months calves. Moreover, we also found that the results of superovulation interval of 2 weeks group with average number of eggs available of 6.3 missiles were significantly worse than the interval of 3 weeks, 4 weeks and 5 weeks group (P<0.05) with that of 16.7, 23.7, 23.0 missiles, respectively. The superovulation difference between 3 weeks, 4 weeks, 5 weeks groups was not significant indicated that the best time interval of 3 to 4 weeks was best for repeated superovulation treatment on calves.

Key words: calves; superovulation; superovulation program