Biological and technological background of estrus synchronization and fixed-time ovulation induction in the pig

A technology that allows for manipulating of estrus 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. Such technology at least in part, saves labor and permits 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. This 'biotechnology of reproduction' will be reviewed. It covers procedures for synchronizing estrus 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 estrus synchronization stand alone, other procedures require additional treatments. If fixed-time insemination is the goal, estrus needs to be synchronized 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.