Rebreeding Your Horse on Foal Heat

Get the facts about this common horse breeding practice.

Question: Our 20-year-old mare has had four foals without any problem. She is due to foal this year after finally conceiving with on-farm AI collection and direct insemination. Barring any foaling problems, should we rebreed on her foal heat or wait for the next cycle?

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Answer: Breeding on foal heat is a subject that will elicit many opinions. With foal heat breeding, the pregnancy rate is lower than on subsequent cycles. The pregnancy loss rate is higher than mares bred on subsequent cycles. A majority of the data for these statistics comes from large commercial breeding farms. A study performed at Texas A&M University looked at foal heat breeding in the population of prison mares. These mares are selected for fertility and bred to stallions of good fertility. In that study, there was no difference with pregnancy rate if the mare was bred on foal heat or if foal heat was skipped and the mare was bred on subsequent heats. I would skip foal heat and breed her on the subsequent cycle. If she is due to foal later in the year, you can shorten the interval to the second heat with the use of prostaglandin. I would suggest having your veterinarian palpate and ultrasound the mare's uterus when she is in foal heat to make sure it is in good shape. - Pete Sheerin, D.V.M., Lexington, Kentucky

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