Without the appropriate consideration of these basic events associated with estrus and ovulation, breeding programs typically produce marginal farrowing rates and waste labor and boar power . Female pigs are not sexually receptive during these periods of progesterone production. Failure to initiate pregnancy results in regression of the CL, a decline in serum progesterone concentrations and a return to estrus. The CA gradually regress during lactation and are less than 2 mm in diameter at the time of weaning. Follicular development is minimal and few follicles are greater than 4 mm during lactation.
Follicles continue to increase in size as the animal approaches estrus following weaning.
Sound management techniques are essential on any farm for the detection of the onset of estrus. Most sows return to estrus within 4-5 days after weaning, thereby, providing a natural synchronization of estrus. These animals should be carefully monitored. Early Embryonic Survival Typical North American domestic pigs give birth to 8-11 pigs. Unfortunately, genetic selection has made limited progress toward greater litter size and previous attempts by researchers provided minimal techniques or strategies to effectively increase sow fecundity.