SYNCHRONIZATION OF OESTRUS AND FERTILITY IN SHEEP WITH TWO INJECTIONS OF FERTIRELIN ACETATE (GnRH ANALOGUE) AND PROSTAGLANDIN F2 a.

A study was conducted to determine whether a single intramuscular injection of 50ug of fertirelin acetate (GnRH analogue) followed 5 day later by 15 mg of prostaglandin F2 a would give an acceptable level of synchronization of oestrus and fertility in comparison with prostaglandin F2a. A total of 45 mature cyclic crossbred ewes (Chios x Ossimi) were involved in the study and randomly allocated to one of four treatment groups (ewes received 1.5 ml saline (group A) or single injection of 15 mg PGFza (group B) or double injections of 15 mg of PGFza (group C) or GnRH-PGF2C (group D)]. Oestrus occurred within 5 days from end of treatment in 45.5%, 72.7%, 90.9% and 91.7% of ewes in groups A to D. Precision of oestrus within 3 days period from end of treatment was higher (P<0.05) in ewes treated with double injections of PGFza or GnRH followed 5 days later by PGFza than ewes treated with single injection of PGF2a. Overall pregnancy rate after treatment with GnRH followed 5 days later by PGFza (group D) was significantly (P< 0.05) greater 83.3 % than for control ewes 27.3% (group A) and treated ewes with single injection of PGF20 45.5% (group B). Moreover, there was no difference in response and reproductive parameters between groups treated with double injections of PGF2a or GnRH followed 5 days later by PGF2a. These results indicated that acceptable levels of oestrus synchronization and fertility can be obtained with a combined injections of GnRH followed 5 day later by PGFza and the treatment can increase the precision of oestrus after PGFza within 3 days from end of treatment.