Lactational anoestrus in the sow

Typically, a sow experiences anoestrus during lactation, due to suckling-induced inhibition of LH secretion. After weaning, pulsatile LH secretion increases, and final antral follicle growth, ovulation and oestrus can take place. Because of this, piglets are weaned at a relatively young age, in order to achieve a high number of litters per sow per year. To avoid the risks of weaning at a young age, the lactation period would have to be extended, but without postponing the next pregnancy. To achieve this, follicle growth and ovulation have to be established during lactation in a predictable manner. This review describes the principles of lactational anoestrus, and suckling regimes that can induce follicle growth, ovulation and conception during lactation.