Benefits and usefulness
Varner states that, in Blanchard's project, about 60 percent of the horses showed an improvement. "With these horses, you
don't know if it will be an improvement unless you try it. Within a group of horses, you might try it where half of them get
it and half of them don't, and then see what happens."
Varner notes that sometimes people won't use reinforcement breeding on the first or second cycle and then try it on the third
cycle for mares that aren't getting pregnant. But, he notes, it's like comparing apples to oranges, because they're likely
looking at a subfertile population of mares. To determine if the technique is beneficial, he cautions, it must be done with
mares on the same cycle (i.e., used or not used for mares in cycle one, two or three). "But to compare pregnancy rate in cycle
one with mares in whom it's not conducted versus cycle three in mares where it is conducted, you might see erroneous information
about its usefulness," Varner says.
Sheerin concludes that reinforcement breeding helps tremendously in some horses but not in others. "In some cases they're
not going to just reinforce the stallion that it helps the most, because then you're pointing the finger at him. So some farms
will reinforce all the breedings, and other farms will reinforce only if the client asks for it. More clients are asking for
it because of Blanchard's research."
Sheerin notes that it's fairly common to reinforce, in certain cases, all mares on a farm because the veterinarian doesn't
want to raise concern about a particular stallion's reputation. "Farms that do it on a routine basis will typically do it
on most, if not all, of their horses," Sheerin continues. At other farms, reinforcement breeding is done if the mare's owner
or the veterinarian asks for it.
"The cases for which I recommend it depend on the mare or for a stallion that I might think has a problem," Sheerin says.
"The mares I use it on are those with a cervix that doesn't relax. When a mare is in heat, her cervix is supposed to be short
and wide open so the semen can go where it should. But in some maiden mares or mares that have had foaling issues and have
a scarred cervix, the cervix doesn't relax like it should. Then you're concerned if the semen got into the uterus, and those
are the candidate mares we would reinforce. Those mares are ones in which you would typically find semen in the vagina (as
opposed to in the uterus)."
Kane is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine
with a background in horses, pets and livestock. He is based in Seattle.
1. Blanchard TL, Love CC, Thompson JA, et al. Role of reinforcement breeding in a natural service mating program, in Proceedings. 52nd Ann Mtg Am Assoc Equine Pract 2006;384-386.
2. Blanchard TL, Thompson JA, Brinsko SP, et al. Some factors associated with fertility of Thoroughbred stallions. J Equine Vet Sci 2010;30(8):407-418.
3. Varner, DD, Love CC, Blanchard TL, et al. Breeding-management strategies and semen-handling techniques for stallions—case
scenarios, in Proceedings. 56th Ann Mtg Am Assoc Equine Pract 2010;215-226.