Use of hCG to induce a prolonged luteal phase in gilts

摘要

Prior to introduction into the breeding herd, gilts are usually subjected to a period of isolation and acclimatization of 30 to 60 days. Depending on the gilt age and weight at entry and gilt management, some gilts will become pubertal during this period while others become pubertal after entering the breeding barn. This lack of predictability may constrain programmed gill service and so negatively affect facility utilization. A reasonable degree of control can be achieved by the appropriate utilization of estrus synchronization compounds such as allyl trenbolone. However, this product is expensive and is unlikely to be economically justified. An alternative approach is to use the gilts own physiology to effect estrus synchronization. An effectivebut controversial technique for estrus synchronization is to breed and then abort. An alternative and more welfare-friendly approach is to induce a prolonged luteal phase and then induce luteolysis as required. To this end, the induction of ovulation and subsequent formation of corpora lutea will cause the production of progesterone which will block estrus. If a prolonged luteal phase can be established, this progesterone production will be maintained. A prolonged luteal phase can be established by theserial administration of estradiol between days 11 and 14 of the estrous cycle. However, this is labour intensive and estradiol is not cleared for use in pigs. Another way to induce a prolonged luteal phase may be the administration of a single dose ofhCG on day 12 of the estrous cycle. The mechanism involved is the induction of follicular development and the endogenous production of estradiol. This is a very attractive approach in terms of using a cleared product, its simplicity and cost relative toother protocols. It is known thai porcine corpora lutea are responsive to prostaglandin (PGF) from 12 to 14 days of the estrous cycle. Therefore, from day 14 onwards PGF can be used to induce luteolysis and gilts should return to estrus 5 to 10 days later. The present study was undertaken to determine the efficacy of hCG for the initiation of a prolonged luteal phase and of prostaglandin for the termination of the prolonged luteal phase.