The effects of eCG and GnRH administration on reproductive performance of Khalkhali goat during breeding season

Increment of ovulation rate in farm animals improves reproductive performance through increasing in litter size and fecundity rate. Estrus synchronization or the induction of estrus is a valuable management tool for increasing the pregnancy rate in goats. Stimulation of ovulation using different methods can improves reproduction performance by increasing the proportion of goats having twin ovulations and thereby increase kidding percentage (Khaldari 2008; Rahman et al. 2008). It has been suggested to use new reproductive approaches such as controlling and synchronizing of estrus and using hormones by applied Artificial Insemination (AI) to increase prolificacy leading to gain practical and economical advantages. Recently, Progesterone or its analogues is generally used to synchronize estrous during the breeding and non-breeding season. Administration of gonadotropins such as equine Chorionic Gonadotropin (eCG) after stopping progesterone treatment, causes an increase in rate of ovulation (Lopez-Sebastian et al. 2007). Also using Gonadotropin Releasing Hormone (GnRH) with eCG leads to a raise in ovulation rate and litter size in different goats breed (Akifcam and Kuran 2003). The objective of this study was to improve the reproductive performance using GnRH and eCG administration in breeding season.
Material and The experiment was carried out on 150 mature (2–5 years of age), non-lactating does with a body weight varying between 37 and 39 kg. The current study was performed in the natural breeding season under natural photoperiod environment. Synchronization of estrus was done by inserting intravaginal sponges containing 40 mg flugestone acetate (FGA, Chrono-Gest, Intervet International B.V., Holland) for 16 days. Goats were randomly assigned to three groups. The control group (T1) exposed to Khalkhali bucks without any treatments for mating after sponge removal. Goats in second (T2) and Third (T3) groups were injected intramuscularly 400 IU eCG (Serogonadotropin®, Biowet S.A., Poland) and 400 IU eCG with 50 mg GnRH (Vetocept®, Aboureyhan Co., Karaj, Iran) respectively in sponge removal time. Then the does were mated naturally with Khalkhali bucks. Five fertile Khalkhali bucks were introduced to each group twice a day, starting about 24 h after CIDR withdrawal, and left with them for estrus detection and natural mating. Does were observed continuously for 3 h when bucks were introduced to them and their mating were recorded. The date of birth, numbers of kids born per does and weight of each kid were recorded at kidding time. Reproductive parameters, including pregnancy rate, kidding rate, fecundity rate, twinning rate was determined as well. Blood was sampled from the external jugular vein into heparinized test tubes. The first blood samples were collected before inserting intravaginal sponges, the second, 7 days after inserting sponges and the third, one day after intravaginal sponge withdrawal. Samples were immediately transferred to the lab and centrifuged in the tubes for 15 min at 1000 ×g to separate the plasma. Plasma samples were stored at −20 ◦C for less than 2 months until analyzed for estrogen and progesterone concentrations. All assays were carried out in duplicate. The reproductive parameters were analyzed by ProcGenmod using SAS 9.2 in completelyrandomized design. The means of all reproductive traits were compared by using Chi-Square test. Born weight of kids and hormone concentration data were analyzed using the General Linear Models procedure of SAS and P 0.05) in breeding season. Control group had lower fecundity rate (106%) than the treatment groups (158% and 188 % in second and third groups respectively). Lambing rate in 1 to 3 treatments were calculated 113, 175 and 177% respectively that the treatment groups had higher (P 0.05). There was no significant difference in plasma estrogen and progesterone concentrations between treatments as well (P>0.05). eCG has biological activity of FSH and LH hormones and luteinizing effect of eCG promotes the maturation of follicle that lead to increase the production of estrogen hormone. Estrogen is effective in causing the estrous cycle (Godfery et al. 1997). Results of the current study showed that the injection of 400 IU eCG after sponge removal had no effect on kidding rate and pregnancy rate. But Zaiem et al (1996) observed that the goats treated with eCG had a higher pregnancy rate compared to the control group. Although some studies have reported that administration of eCG can improve the kidding rate and pregnancy rate in breeding season (Kermani Moakhar et al. 2012) as well as non-breeding season (Husein and Ababneh 2008). On the other hand, some studies reported that eCG has negative effects on pregnancy rate (Zeleke et al. 2005; Menchaca and Rubianes 2004). In the current study, treatment with eCG and eCGᩴ increased twinning rate. This result agrees with those reported by Ali et al (2007). Zarkawi et al (1999) reported that using eCG at CIDR withdrawal increased twinning rate from 7% in control group to 30% in treatment group. Also they observed no significant difference in twinning rates for high eCG doses. In another study using eCG in breeding season led to significant increase in twinning rate (61.9% vs 29.2%), lambing rate (86.2% vs 68.6%) and fecundity rate (127.6% vs 71.4%) compared with the control group (Koyuncu and Ozis Altıcekic 2010). These results were similar to the findings in the present study. There was no significant difference in weight of kids at kidding between treatments groups and control and this result shows that weight of kids was not affected by hormones treatments.
In conclusion, using of synthetic hormone caused improvement of reproductive efficiency of Khalkhali goat in breeding season.