Effect of season on fertility of sows

Reduced fertility of sows during the warmer period of the year is a well-known occurrence in practical production. Namely, during summer months gilts become sexually mature later, the interval from weaning to estrus is prolonged, there is a greater number of postlactation silent estruses anestrias and ovarian cysts, the value of conception is lower, there are more irregular failed fertilizations, there is a higher degree of embryo mortality, and the litter size is smaller. This is why this occurrence presents an important zootechnological, veterinary-medical and economic problem. Most scientific research shows that this phenomenon is a consequence of the effects of an extended daily photoperiod and a higher ambient temperature. However, the degree of the individual effect of these factors has not been determined clearly, or the physiological and endocrinological mechanisms of their action. It is probably not possible completely to avoid the negative influence of seasonal factors on reduced fertility in sows during the summer period. However, it can be significantly alleviated with a regular maintenance technology, diet, hygiene and medical protection of sows. This paper presents knowledge acquired so far on the manifestation of this phenomenon, its physiological and endocrine bases, as well as possibilities for its practical resolving