The effect of hCG and GnRH on reproductive performance of superovulated Lake-Ghashghaei and Torki-Ghashghaei ewes with eCG during the breeding season

Reproductive performance of different sheep races is low in Iran and breeding of this domestic animal is not really economic. So it should be found essential and practical solutions for increasing reproductive performance of sheep. One of the suitable solutions is hormonetrapy such as using human Chorionic Gonadotropine (hCG) and Gonadotropin Releasing Hormone (GnRH) in superovulated ewes with equine Chorionic Gonadotropin (eCG), but, the results of different studies in hormonetrapy if different races are not similar. Therefore the present study was conducted to investigate the effect of these hormones on reproductive performance of Lake and Torki-Ghashghaei in rural breeding condition.

This study was conducted in two separated experiments. In the first experiment 75 Lake-Ghashghaei ewes (3-4 years old with the mean weights of 542.6 kgs) and in the second experiment 75 Torki-Ghashghaei ewes (3-4 years old with the mean weights of 591.9 kgs) were used. The estrous cycle of ewes in breeding season was synchronized with progesterone sponges for a 14 days period. Then, one day before removing the sponges 500 and 600 IU of equine Chorionic Gonadotropin were injected intramuscularly to Lake-Ghashghaei and Torki-Ghashghaei ewes respectively. After removing the sponges all the ewes became cycled and divided into three different treatment groups. The first group in each experiment was assumed as control and the second and third groups received 500 IU human Chorionic Gonadotropine and 0.5 ml Gonadotropin Releasing Hormone respectively. Then, in each experiment parameters such as the time of estrus start (hour), rate of return to estrus, parturition rate, rate of multiple births number of lambs and rate of lambing were evaluated.

The results in the first experiment (Lake-Ghashghaei ewes) indicated that the rate of return to estrus did not have significant differences among various treatment groups but the number of delivered ewes in human Chorionic Gonadotropine group was numerically more than other groups. The results also indicated that the number of single, twin and triple births' ewes was not significantly different among various treatment groups but the number of twin and triple births' ewes in human Chorionic Gonadotropine group was numerically more than other groups. The results in the second experiment (Torki-Ghashghaei ewes) indicated that the number of twin births' ewes fecundity and prolificacy rates were numerically more in human Chorionic Gonadotropine group compared with other groups. The results also indicated that the fecundity difference among different treatment groups had tendency to significantly (P=0.06) and this characteristic was higher in group receiving hCG, compared to other groups.

According to the obtained results, it can be suggested that using human Chorionic Gonadotropine (500 IU) in superovulated Lake-Ghashghaei and Torki-Ghashghaei ewes with equine Chorionic Gonadotropin (500 and 600 IU, respectively) caused improvement the number of born lambs and fecundity rate.