Fertility of anestrus ewes infused with gonadotropin releasing
hormone or injected with pregnant mares' serum gonadotropin
A.H. Hamra; J.E. Wheaton; J.M. Marcek
Department of Animal Science, College of Agriculture, Abu-
Ghraib, Baghdad, Iraq
Proceedings of the New Zealand Society of Animal Production.
1990, 50: 461-464
Two experiments were conducted to compare PMSG injection to GnRH
infusion for induction of breeding in anoestrous ewes. In Experiment
One, sixteen Suffolk ewes were pre-treated for 14 days with 30 mg
Cronolone sponges. At sponge removal half of the ewes received 0.125
ug/hr GnRH for 72 hours via subcutaneous osmotic pumps. The other half
received a single injection of 750 iu PMSG. Plasma LH levels gradually
increased and were sustained for 24 hours. Estrus, ovulation and
corpus luteum function were expressed in half of the ewes treated
with GnRH. All ewes treated with PMSG exhibited estrus, ovulated and
formed functional corpora lutea.
In Experiment Two, 24 ewes were divided into two groups and the same
treatments as in Experiment One were applied. Fertile rams were
introduced to all the ewes at the time of sponge removal. Estrus was
detected in 75% of the GnRH treated ewes vs 100% in PMSG treated ewes.
Lambing rates were 44% and 56% in GnRH and PMSG groups respectively.
These results suggest that the induction of fertility using continuous
infusion of GnRH is encouraging. However, other GnRH delivery systems
should be investigated.
Keywords: NZSAPAB;
Ewes; seasonality; induced fertility; GnRH; PMSG
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Last Updated 25-01-1997
