Abstract
In temperate regions goat’s reproduction is seasonal. To obtain year-round breeding, hormonal treatments are currently applied. These treatments usually combine a progesterone analog with the pregnant mare serum gonadotropin (PMSG). However, their use has significant ethical and environmental drawbacks. Therefore, alternative methods to manage reproduction are needed. The discovery that in mammals the neuropeptide kisspeptin is a major positive regulator of hypothalamo-pituitary gonadal axis offered an attractive alternative strategy to control reproduction. We have previously designed a kisspeptin analog, called C6, which offers pharmacological advantages over endogenous kisspeptin. These include a longer lasting effect and enhanced activity following intramuscular injection. In the present work, we evaluated C6 effect on LH and FSH plasma concentrations in the Alpine goat breed and tested whether C6 could replace PMSG to trigger ovulation. An intramuscular injection of C6 (15 nmol/doe) given 24 hours after the end of progestogen treatment induced a surge-like peak of both LH and FSH. This was followed by an increase of progesterone, a hallmark of ovulation induction and corpus luteus formation. These results were obtained at three different time of the year: during the breeding season, the non-breeding season and at the onset of the breeding season. Furthermore, we compared the efficacy of C6 and PMSG to induce fertile ovulations when these treatments are given at the onset of the breeding season and are followed by artificial insemination. The results of this first attempt were extremely promising with gestation rates of 45% and 64% for C6 and PMSG respectively. Pending optimization of the treatment procedure in order to improve efficacy, kisspeptin analogs could be the long sought-after alternative to PMSG.
Highlights
In temperate regions breeding seasonality of small ruminants translates into annual fluctuations of production affecting farmers’ profits
We compared the efficacy of C6 and pregnant mare serum gonadotropin (PMSG) to induce fertile ovulations when these treatments are given at the onset of the breeding season and are followed by artificial insemination
Fertility outside the natural breeding season is achieved mainly by hormonal treatments. These are based on progestogens and pregnant mare serum gonadotropin (PMSG called eCG for equine chorionic gonadotropin)
Summary
In temperate regions breeding seasonality of small ruminants translates into annual fluctuations of production affecting farmers’ profits. The use of hormones, especially PMSG, is facing several problems These include: reduced efficacy over time due to the production of antibody neutralizing PMSG [1], potential sanitary risks due to its extraction from animal fluid, and an increasing public hostility due to serious concerns related to animal welfare (UE report: PE 589.295v02-00 A8-0014/2017, point 43). Alternative methods, such as the so-called natural methods (which include the male effect and photoperiodic treatments), exist [2]. We conclude that C6 might be used as an alternative to PMSG in the control of reproduction in female goats
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