Abstract
Sixty adult ewes were treated intravaginally for 12 days with one of three progestagen treatments: (1) 500 mg progesterone pessary, (2) 30 mg flurogestone acetate pessary, (3) 12% (w/w) progesterone in a Controlled Internal Drug Release (CIDR) device. On days 10, 11 and 12 of progestagen treatment ewes received either 60, 45 and 30 mg; 45, 45 and 45 mg or 30, 45 and 60 mg of horse anterior pituitary extract (HAP), respectively. Progestagen treatment was terminated on day 12 at the time of the last HAP treatment. Ewes were bred by artificial insemination at 8- and 16-h intervals during oestrus, which was checked by using vasectomized rams. Ovarian response and fertility were determined at laparotomy 8 days after progestagen withdrawal. Progestagen treatment significantly increased ( P<0.05) ovulation rate, with a mean of 9.1, 12.0 and 6.6 ovulations from treatments (1), (2) and (3), respectively. The method of HAP administration had no significant effect on ovulation rate, with a mean of 9.8, 10.0 and 7.8 after either decreasing, constant or increasing levels during treatment. There was no difference in the fertilization rate following flurogestone acetate (45.7%) or CIDR (47.0%), but a lower rate resulted after the progesterone pessary (30.0%) ( P<0.025). More eggs were recovered following local than following general anaesthesia ( P<0.05). Results indicate that cervical insemination does not give a satisfactory yield of fertilized eggs following hormonal inductions of superovulation.
Published Version
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