Studies on fixed-time ovulation induction in the pig

Abstract

A technology that allows for manipulating of oestrus and ovulation, and would then also allow for fixed-time insemination, can be of great benefit for swine farms that operate using sow batch management due, at least in part, to savings in labour and the production of large batches of evenly developed pigs. Thanks to the current knowledge on endocrine regulation of follicle development and ovulation, and the availability of numerous reproductively active substances such a technology is now available. It covers procedures for synchronising oestrus based on the use of altrenogest in gilts and of batch-wise weaning in sows, for stimulating follicle development using eCG and for inducing of ovulation using hCG or LH as well as GnRH analogues. While the procedures for oestrus synchronisation stand alone, other procedures require additional treatments. If fixed-time insemination is the goal, oestrus needs to be synchronised and follicular development and ovulation induced by the use of GnRH analogues and hCG with ovulation occurring within 36-42 hrs. It is a general recommendation to inseminate those animals twice, i.e. 24 and 40 hrs after ovulation induction. However, the aforementioned technology requires healthy animals and a solid management and cannot be used to compensate for poor management.

Dynamic profile of EVs in porcine oviductal fluid during the periovulatory period

“…Hence, the periovulatory phase is more relevant for gamete/embryo-maternal interaction. The sows' hormonal profile dramatically changes within this short period: estrogen level peaks during estrus, followed by the luteinizing hormone (LH) peak around 11 h later, which initiates ovulation for approximately 36-42 h (Brussow et al 2009). After ovulation, the level of progesterone quickly rises within the first 2 days (Henricks et al 1972).…”

Weaned Sows with Small Ovarian Follicles Respond Poorly to the GnRH Agonist Buserelin

“…At this point, it is also interesting to know that administering GnRH agonists at the start of estrus could also worsen the synchronization of ovulation since some sows could experience the endogenous LH surge before it would be induced by the exogenous GnRH agonist and consequently ovulate before the expected time [20]. In this controversy, it is important to point out that the administration of an GnRH agonist is recommended between 83 and 89 h after weaning, time when many weaned sows have already started estrus [10,17]. Interestingly, most sows showing post-weaning anovulatory anestrus had one or two parities.…”

“…Currently, exogenous hormones have proven practical utility for successful induction and synchronization of ovulation time in sows, inducing ovulation within an expected narrow time window in most sows [8,10]. The useful hormones include human chorionic gonadotropin (hCG; [11][12][13]), porcine luteinizing hormone (pLH; [14,15]) and GnRH analogues, particularly synthetic agonists such as buserelin [16][17][18], licerelin [19] or triptorelin [20,21].…”

The effect of fixed-time artificial insemination protocol initiated at different stages of the estrous cycle on follicle development and ovulation in gilts

“…Therefore, a variety of hormone products and analogs, such as altrenogest, pregnant mare serum gonadotropin (PMSG), equine chorion gonadotropin (eCG), GnRH, D-Phe6–LHRH (a GnRH agonist), and triptorelin (a GnRH agonist), have been developed to synchronize the estrous cycle and ovulation in domestic animals [ 7 , 8 , 9 , 10 , 11 ]. The use of these hormone products has led to the development of a novel technique, known as fixed-time artificial insemination (FTAI), which has been widely accepted in recent years by most large pig farms in China and several other countries [ 12 , 13 ].…”