Ovulation and fertilization rates in anoestrous ewes, treated with a progestagen (MAR) and seric gonadotrophin (PMSG)

Jorge E. Correa1 e Ingrid Vandeputte2

Twenty four non lactating Romney Marsh ewes were controlled during the anoestrous season in Valdivia, Chile (lat. 400 S) during November and early December. Twelve ewes were treated with a 60 mg medroxy progesterone acetate (MAP) sponge. The sponge was kept intravaginally during 12 days. The day of pessary withdrawal, the ewes received 500 u, of Pregnant Mare Serum Gonadotrophin (PMSG). The other 12 untreated ewes were used as control. Al) the treated ewes were matad within 3 days after the PMSG injection. None of the control ewes showed oestrus. Laparotomies and flushing of uteri and oviducts were carried out 8 days after PMSG injection. Eleven out of the 12 treated ewes ovulated, with an ovulation mean of two CL per ewe (range 0-6 CL). Two out of 12 untreated ewes ovulated with an ovulation mean of 0.16 CL per ewe. A fertilization rate of 78% (11 ova fertilized/14 ova recovered) was found in the treated ewes.

1 Instituto de Reproducción Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.
2 Memorante, obtando al título de Médico Veterinario, Universidad Austral de Chile.