Bob Douglas, PhD, owner of BET Labs in Kentucky, specializes in working with veterinarians and farm owners to assist in reproductive problems of mares and stallions. He works with Northern and Southern Hemisphere breeders, and said his clients who maintain mares in Kentucky have suffered losses in all ages of foals.
Southern Hemisphere foals will start being born about Aug. 1 in Kentucky, and some breeders lost half or more of this year's foals thus far (which would have been about six to eight months gestation).
One thing Douglas and veterinarians have been cautioning breeders about is that some of these mares which lost early fetuses might show heat, but won't have a breedable follicle. "Just because a mare is teasing in heat doesn't mean she'll be bred successfully," said Douglas. "You have to get rid all luteinized structures, both CLs (corpus luteums) and luteinized follicles." Glossary of Terms
Douglas explained that with a rise in luteinizing hormone (LH), developing follicles fill with blood and the wall of the follicle gets luteinized and acts as a CL (inhibiting progression of a breedable follicle and return to estrus).
"You have to go back in there with prostaglandin to get rid of the hemorrhagic follicles which may be luteinized, and there could be several," said Douglas. "You have to clean the ovaries off and get them started again."
With mares which lost foals at 60-90 days and have accessory CLs that inhibit a return to heat to protect a pregnancy, the ovaries are essentially inactive.
"She's like a January mare," explained Douglas. "You can use domperidone or sulpiride to stimulate prolactin release, but you need GNRH to recruit a breedable follicle. It takes two to three weeks. If the mare is set up right on this program, it is effective (at returning the mare to a breedable heat) more than 60% of the time."
Douglas said farm managers need to understand that veterinarians have to ultrasound the ovaries in order to discriminate between breedable follicles and those which are filled with blood and not fertile.
"We need more time and the proper drugs" to get some of these mare in foal, said Douglas. "If we had a purified equine FSH and LH, we could drive a viable follicle in eight to nine days. They have those products for cattle, but they're a difficult product to make."