Abstract
Using a progesterone agent [Controlled Internal Drug Releasing-Bovine (CIDR-B)] made of a silicone resin containing 1.9 g of natural progesterone that is inserted into the vagina, continuous superovulation (I course) treatment was intentionally performed twice at an interval of 35 days in Japanese black multiparous cows regardless of the estrous cycle. It was then investigated whether this continuous treatment could be further repeated twice at an interval of 42 days (total of 3 repetitions=approximately 1 year). The test animals were 9 Japanese Black cows. CIDR-B was inserted into the vagina regardless of the estrous cycle and superovulation treatment was started after Day 10. The method of treatment consisted of either a decreasing dose administration over a period of 3 days of FSH (total amount=20 AU), or simultaneous and separate subcutaneous administration of FSH 25 AU dissolved in 30% PVP (polyvinyl pyrodine) and FSH 5 AU in physiological saline, in the neck. Ovum collection was non-surgical methods on Day 7. Estrous was confirmed in all the animals (total of 54) that were treated and ovum collection was performed. The results of the superovulation treatment were as follows: mean estimated number of luteal bodies,10.5 ± 0.8 (S.E); mean number of residual ovarian follicles, 9.3 ± 0.9; mean number of normal embryos, 6.7 ± 0.3; and mean percentage of normal embryos, 71.7%. In addition, the results by course (I, II, III course), with 18 animals in each course, were as follows: mean estimated number of luteal bodies, 9.2, 9.8, and 12.5, respectively; mean number of recovered ovaries, 8.2, 8.7, and 11.0, respectively; and mean number of normal embryos, 6.0, 5.8, and 8.2, respectively. There were no statistically significant differences in the results and they were similar to those obtained using the conventional FSH decreasing dose administration method. From the above results, it was evident that continuous superovulation can be done intentionally over 1 year in cows using CIDR-B, regardless of the estrous cycle.
