Improvement of Conception in Sheep Using Different Hormonal Treatments during Mating and their Influence on the Antioxidant Status

Abstract

The objective of this study was to compare the effects of GnRH, prostaglandin F2α (PGF2α) and oxytocin treatments at the time of natural mating on the conception rate (CR) of non lactating pluriparous ewes. All ewes (n=61) were served naturally by fertile rams every 12 hours after the beginning of estrus. After natural mating, ewes were randomly assigned into four treatment groups; G1 received PGF2α (n=14); G2 received GnRH (n=12); G3received oxytocin (n=15) and G4 or control received placebo (n=20). Pregnancy diagnosis was performed 25 days post-insemination by transrectal ultrasonography. Ewes were bled at the day of mating and every 10 days till Day 50 post mating to determine the changes in the total antioxidants during the first third of pregnancy. Pregnancy rate was higher (P<0.05) for all the treatment groups (69.33%) compared with the control group (55.54%). Litter size did not differ between groups except for oxytocin group. Ewe lambs dominate male in this study and the sex ratio unexpectedly preferred them. Total antioxidants did not differ significantly between groups in the present study but they were at their lowest values during estrus in all the studied groups. Gestation length, birth weight, number of services, body weight did not affect the pregnancy rate. It could be concluded that treatments with GnRH and PGF and oxytocin at the time of service could improve conception rate in pluriparous ewes.