When talking about reproduction, most times the emphasis is on the mare. But if your mare doesn't conceive on a single, well-timed cover, the stallion's fertility may be the issue.
Dr. Steven Brinsko, a reproductive specialist at Texas A & M University, said the first step is to have the stallion examined by a reproduction specialist to determine the reason for his subfertility. If the examination reveals a problem that cannot be resolved (like an anatomical problem), there is no sense spending time and money in an attempt to increase the stallion's fertility. If no permanent condition exists, Brinsko suggested some immediate and long-term management solutions that are permissible for Thoroughbred breeding.
Most advances in reproductive techniques used in artificial insemination that entail laboratory manipulation of the egg and sperm are not available for Thoroughbred breeders because the Jockey Club requires live cover. But reinforcement breeding is a low-tech option shown to increase impregnation rate.
Reinforcement breeding is the practice of collecting semen from the exterior of the penis when the stallion dismounts the mare and then mixing it with prewarmed semen extender and infusing it into the uterus of the mare just covered.
In a 2006 study, Dr. Terry Blanchard, a reproductive specialist at Texas A & M, reported: “Mares receiving reinforcement breeding had a greater chance of getting pregnant than mares that were not reinforced; this resulted in an average increase of a 12 percent-per-cycle pregnancy rate in eight of 13 stallions in the study.”
“In some of these subfertile stallions, you get a dismount sample and collect the drippings off the end of the penis, add semen extender to that and then you can actually artificially inseminate the mare with that,” said Brinsko. “One other thing we can do is put semen extender into the mare's uterus to help with the survivability of the sperm in the uterus before it gets to the fallopian tube.”
This method is successful for some subfertile stallions, but not others. Blanchard said stallions whose impregnation rates increase with the use of reinforcement breeding during the first season it was employed also experienced a similar increase when it was used in subsequent years.
Another option is repeated matings. Over the past 30 years, stallion books have increased dramatically, from about 40 mares in the 1980s to as many as 300 mares for today's stallions who do dual-hemisphere duty. Most mares are expected to conceive on one strategically timed cover. Brinsko suggested reducing the book for a subfertile stallion so he is able to cover an individual mare multiple times.
“Adjust their book down so that they are able to double-breed mares rather than have one shot at them,” Brinsko said. “In other words, being able to breed them closer to ovulation and at least twice, sometimes three times, you are able to breed them as close to ovulation as possible.”
A stallion's body takes two months to complete a cycle of sperm production (spermatogenesis). Brinsko said any management strategies should be given at least that much time to produce results. Horses retiring from racing or other athletic careers should be allowed at least two months to settle down before breeding them.
“When horses just come off the track, and those in intensive training, because they're stressed, their semen quality is poor,” Brinsko said. “After we take them out of that environment and let them be a horse, their testes will actually grow and their semen quality will improve.”
Brinsko said the situation is different for every stallion, because each horse is an individual.
“Some horses could take several months, and other ones, even though they might have some stress, have [good] semen quality even coming right off the track,” he said. “In general, we would really prefer to have the horse off three to four months at least before we intend to breed them. We need to let them settle into the breeding farm routine and allow those stress hormones to decline.”
Because sperm membrane is made of fatty acids, supplements containing omega-3 and docosahexanoic acid (DHA) are helpful to enhance fertility in some stallions. DHA is the end product of omega-3 after it is processed by the horse's body. Sperm is high in omega-3 fatty acids, particularly DHA. A high ratio of DHA to omega-6 fatty acids results in enhanced fertility, whereas the reverse results in diminished fertility.
“Horse feed, in particular a corn-based diet, has the wrong ratio of omega-3 to omega-6 fatty acids,” Brinsko said. “For fertility, we need higher omega-3 to omega-6, because corn is very high in omega-6. Putting these nutraceuticals in its diet can help that, and also getting an energy source other than corn, such as flaxseed or flax oil, something that's higher in omega-3 could potentially help.”
Carnitine in the diet has been shown to improve fertility. In a 2016 Australian study, stallions were fed a daily supplement containing 40 grams of L-carnitine from September 1 through December 31, in anticipation of the Southern Hemisphere breeding season. The researchers saw an improvement from week six of treatment onward.
Adding vitamins E and C to these supplements enhances results.
Brinsko suggested two Platinum Performance supplements specifically designed for stallions: Platinum Potency, containing omega-3, DHA, and vitamins E and C; and Platinum Motility Plus, containing two forms of carnitine.
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