To further strengthen the research and clinical services in equine reproduction, two reproduction experts— Jonathan R. Hill BVSc, MACVS, PhD, and Dietrich H. Volkmann BVSc, MMed Vet-recently joined the faculty. Both come from overseas and bring a diverse background in theriogenology.
Hill comes from Australia where he earned his veterinary degree in 1985 and worked in private practice for 10 years-most recently as a partner in a rural rural mixed practice and an ovine and bovine artificial breeding center. To delve further into reproductive medicine, Hill completed a residency in theriogenology at Texas A&M in 1998 and a PhD degree in reproductive physiology in 1999. While at Texas A&M, Hill was one of the first researchers to clone a calf from adult cells. He also studied whether oxytocin could improve pregnancy rates after insemination in mares (it didn't) as well as testicular degeneration in stallions.
Since joining the Cornell faculty in late 1999, Hill has been studying pregnancy losses in large animals, in vitro fertilization and embryo transfer in sheep, and ways to improve nuclear transfer (cloning) by studying the abnormalities in cloned embryos, fetuses, and calves.
"We find, for example, that most pregnancy losses are due to placenta problems, primarily a lack of vascularization in the placenta and inadequate attachment of the placenta to the uterus," says Hill. "We are trying to determine the specific mechanisms that cause these abnormalities in the first trimester."
In the future, Hill would like to study in vitro embryo production further using bovine embryos as a model. He also wants to produce cartilage precursor cells for equine joints from stem cells.
"What I'd really like to do is to make in vitro-produced and cloned embryos more viable by trying to figure out how to improve the efficiency of the techniques and the health of the offspring," he says.
Volkmann grew up on a beef ranch in Namibia and was educated at the University of Pretoria in South Africa, where he worked until 2000. His most recent post was as head of the Department of Theriogenology.
"I've always been interested in reproduction, and when given an opportunity after vet school to do research in equine reproduction, I grabbed it and never looked back," says Volkmann.
In South Africa, veterinarians must learn about all species, so Volkmann conducted research across many veterinary species, including dogs and sheep.
"As we learn details about one species, we may or may not be able to apply them to other species," says Volkmann, who joined the college faculty last year.
He is conducting research on epididymal sperm preservation, a process that is used when important breeding horses are castrated or put down for various reasons.
"We are exploring why sperm from the epididymis (the duct in which mature sperm are stored) are different from ejaculated sperm. We are trying to find out, for example, the role of the seminal plasma. Is the fluid of semen important for fertility or not? We assume it is not, but then what is its role?"
To date, epididymal sperm have been frozen successfully and fertility trials are in progress.
Volkmann also is testing drugs that induce ovulation in mares to give breeders more control in trying to breed their mares with frozen semen, which is viable and able to fertilize for only a very short time. Deslorelin is one drug he is looking at. This time-released implant induces ovulation. Volkmann thinks it may continue to be released in the body for too long, thereby inhibiting mares from coming back into heat if they fail to conceive at the induced ovulation.
Volkmann also is studying the mechanisms for the detachment of the afterbirth after foaling, as premature detachment can suffocate a fetus and delayed detachment puts the mare at extreme risk.
"We also are looking at the recent abortion syndrome in Kentucky," says Volkmann. "Last summer, hundreds of thoroughbreds lost their foals in late pregnancy and we don't know why." At the same time, many other mares that had already conceived (a new pregnancy) in the spring were also losing their fetuses.
Volkmann is part of a research team that is analyzing blood samples from the mares that lost their pregnancies. In an early pregnancy loss, the mare loses its placenta and fetus but continues to secrete a hormone, equine chorionic gonadotropin, that prevents her from coming into heat again for up to 100 days. By that time, the breeding season is usually past and the mare will go barren. Volkmann hopes to figure out how to manipulate the hormonal environments of mares that have lost their fetuses so they will return to heat again more promptly. "
