Breeding on foal heat (the first heat period after parturition) has long been a practice that some horse owners love and others hate. Foal heat breeding begins five to 12 days postpartum, with most ovulations less than 20 days postpartum, said Terry Blanchard, DVM, MS, Dipl. ACT, of Texas A&M University, in his presentation on the topic.

Those that love foal-heat breeding say it decreases the mare's odds of reentering anestrus (lack of cycling) and avoids delay in foaling to conception interval to maintain annual production of foals, he said. He listed further arguments in favor of the practice as follows: The pregnancy rate can be good, and the cumulative season pregnancy rate can be comparable to those from first breeding on a later postpartum estrus. Also, a pregnancy from breeding this early keeps the mare foaling early in the year, which is preferable for breeds in which all foals have the same birthday at the beginning of the year regardless of their actual age.

Those against the practice, however, claim that there is a lower pregnancy rate than on later postpartum estrus (about 20%), and there might be increased pregnancy losses for these pregnancies, he said. Other problems might include issues with delayed uterine involution (return to normal size and position following delivery) and excessive contamination of the reproductive tract following more breedings than might be necessary if the foal heat were skipped and the mare started breeding on a later heat.

Is the success or failure of foal heat breeding dependent on farm management? Possibly, he said. His talk primarily centered on the positive experiences one farm has had with the practice over a five-year period