Tufts Veterinary Field Service Leading the Charge in Assisted Reproduction in Farm Animals

Farm animal embryo transfer is advancing rapidly, and at the heart of the action is Tufts Veterinary Field Service (TVFS) at Cummings School of Veterinary Medicine.

More than 55,000 farm animals are treated every year by TVFS in Woodstock, Connecticut. TVFS specializes in equine, bovine, and small ruminant (sheep, goats, camelids) services, focusing on wellness care, sports medicine, and herd health. TVFS falls under the Department of Ambulatory Medicine and Theriogenology, established three years ago with the dual mission of serving farm animals and training students in large animal veterinary medicine.

"The department was created to provide leadership to a growing group of faculty members, with a common purpose. The faculty themselves settled on the name, 'Ambulatory Medicine and Theriogenology,' to reflect the most important aspects of their work," says Cummings School Dean and Henry and Lois Foster Professor Alastair Cribb, D.V.M., Ph.D., FCAHS. "Theriogenology is a key discipline across all species. It helps support animals' reproductive health and our agricultural and rural communities."

One area that has developed dramatically over the past few years is TVFS's reproductive medicine, specifically embryo transfer.

"With cattle, small ruminants, and horses, we're at the front edge for all three species," says Dr. Eugene White, D.V.M., DABVP, Professor and Amelia Peabody Foundation Chair in Agricultural Sciences in the Department of Ambulatory Medicine and Theriogenology at Cummings School. Dr. White has been with TVFS for 27 years, focusing mainly on cattle.

Dr. White, Associate Professor Dr. Rachael Gately, D.V.M., and Assistant Clinical Professor Dr. Adam Ward, D.V.M. are assisted by Large Animal Veterinary Technician Cassidy Narkawicz in performing the transfers almost daily, year-round. Overseeing TVFS is Dr. Carlos Pinto, MedVet, Ph.D., A.C.T, Dorrance H. Hamilton Professor in Applied Reproductive Medicine and chair of the Department of Ambulatory Medicine and Theriogenology.

"We have a unique group of talented faculty in our department," says Dr. Pinto. "We're excited to have faculty with such great potential to advance our mission here. After decades of being primarily engaged in providing clinical services, our department has been experiencing a very productive phase, combining teaching, clinical service, and research and discovery."

Embryo transfers in cattle, where an embryo from one cow is inserted into a recipient cow, is a powerful, advanced assisted reproductive technique available for farm animals. This specialized service began to be offered at TVFS around 2009 and increased significantly about five years ago with the rise in demand from beef and dairy producers.

The procedure aims to produce better cattle by obtaining multiple offspring from the very best cattle during a single year. Donor cattle may be selected based on production, fertility, disease resistance, or excellent feet and legs. "Also, if a dairy cow can carry a pregnancy but is unable to conceive her own, acting as an embryo recipient could help extend her productive life," says Dr. White. 

Embryos from across the country and worldwide are received almost daily at TVFS and stored at the clinic until ready for transfer. From 2016 to 2021, TVFS averaged nearly 500 bovine embryo transfers annually. The number of transfers rose sharply over the past two years, with 775 completed in 2022 and 1,725 last year.

The benefits of assisted reproduction with cows are significant for dairy farms, including keeping cows producing milk and supplementing the dairy farmers' incomes. Dairy farmers can provide cows in their everyday milking herd to serve as recipients, or surrogates, for a fee, thus supplementing the farm's income. These cows serving as recipients will carry a calf owned by someone other than that dairy farm; sometimes, that owner is local, and sometimes, they live in a completely different state. The advantage to the owner of that embryo, or future calf, is that they can have more high-value or rare-breed calves born than they have their own adult cows to carry the calves on their own farm. It is a win-win for both parties – the dairy farmer is able to begin a new lactation with their cow while eliminating the concern for excess production of their own calves, and the owner of the embryo can bring home new genetics to their own farm in the form of a young calf.  One of the largest recipient herds for TVFS is Fairvue Farms in Woodstock, home to about 3,000 Holstein cattle, including 1,500 milking-age cows, each milked three times daily.

"There's a need to be met, and the vacuum is already present," says Dr. White. "Embryo transfer helps control the number of females born to meet the needs of the farm. We're always looking for innovative ways to generate income for dairy farmers."

Dr. Gately, who has been involved with embryo transfer work with small ruminants, cattle, and horses for 13 years at TVFS, adds, "A cow needs a pregnancy to make milk, but you can't keep every calf because the farm grows too fast. Assisted reproduction with bovines has the unique aspect of helping commercial dairy farms stay in business more efficiently."

With small ruminants, one of the main benefits of embryo transfer is importing rare genetics. Many U.S. farmers would like to acquire embryos from Europe, with recently opened avenues. Donor animals must undergo months of vetting, tests, and isolation before exporting embryos to the U.S.

"It's a big process, but it's possible now," says Dr. Gately. "The most classic example, Valais Blacknose sheep from Switzerland, are now here because the border is open. A few years ago, they were not on North American soil. We now can collect, freeze, thaw, and transfer embryos that let us take a breed from Switzerland to the U.S."

Dr. Gately and her team transferred embryos from a Dutch Spotted sheep in the United Kingdom to a recipient sheep here in the U.S. This marks the first successful embryo transfer of that breed in this country. This coveted breed from the U.K. is now grazing at a farm in Vermont.

"Farmers want to propagate good genetics," says Dr. Gately. "I have a ewe named Annie, who is a prime specimen of the Dorset breed of sheep. They naturally raise one to three lambs a year, so she'll maybe get ten lambs in her lifetime. If we do an embryo collection, we can possibly get 30 to 50 lambs from Annie that can then be carried and raised through surrogates."

For the equine community, embryo transfer facilitates passing along desirable or superior genetics from a valuable animal to offspring, according to Dr. Pinto. Embryos are collected from valuable mares and transferred into recipient mares. Assisted reproduction also allows mares who are showing or competing to produce offspring without going through pregnancy and interrupting those activities.

"Some mares may have reproductive problems that prevent them from becoming pregnant or carrying a pregnancy to term, such as a broken pelvis or disorders of the reproductive tract that cause pregnancy losses. For these mares, we can collect embryos and transfer them into reproductively sound recipient mares," says Dr. Pinto.

Dr. Pinto explains that conventional in vitro fertilization in horses is still an incipient technology that is beginning to become a viable option for producing embryos in vitro. However, intracytoplasmic sperm injection, in which a single sperm is injected into an oocyte, has been successful in horses, with thousands of foals born worldwide within the past ten years.

In addition to on-the-ground embryo work, exciting research in the field is also happening at TVFS. The Swiss Village Farm Foundation, an organization that sought to preserve endangered and rare species of cattle and sheep, granted a $3.5 million gift to Cummings School to establish the Dorrance H. Hamilton Professorship in Applied Reproductive Medicine. For 20 years, the TVFS clinicians assisted with collecting germplasm samples (embryos, sperm, blood, etc) from rare and at-risk breeds of cattle and sheep; these samples are currently stored at the Smithsonian Conservation Biology Institute in Front Royal, VA. Dr. Pinto is the first to hold this professorship. One of his projects is collaborating with the Smithsonian Institution to devise a strategy to study and utilize these germplasm samples. "Rare foundational species of cattle and sheep are more resilient to disease, lower levels of nutrition, and adverse environments. Due to the high productivity of cows today, they are increasingly susceptible to disease and decreased fertility," says Dr. Pinto.

"Expanding the clinical reproductive services we offer at TVFS is another goal we have. We hope to establish research and clinical labs at TVFS to offer clinical embryo services across species for commercial use. Cummings School is supporting this goal by planning an expansion and renovation of our facilities in Woodstock, which will allow us, among other things, to set up a commercial in vitro lab for cows, sheep, goats, and horses. We are very excited about the prospect."

Additionally, Dr. Gately is working with Stephanie Bertrand, M.B.A., at Cummings School's Farm, and Heather Gray-Edwards, D.V.M., Ph.D., at UMass Chan Medical School, to create large animal models of human neurodegenerative disorders. This team is starting to investigate how in vitro fertilization can be successfully utilized in their collaborative approach to developing models of rare disorders such as Sialidosis, Maple Syrup Urine Disease, and more.

Amid all this work are the veterinary students of Cummings School, who rotate through TVFS every three weeks, focusing on primary care and embryo work.

"Cummings School is committed to providing students with a comprehensive veterinary education that prepares students for a range of career pathways in veterinary medicine. The department ensures that we provide excellent herd and individual animal health care for farm animals through Tufts Veterinary Field Service, providing an excellent learning experience for our students," says Dean Cribb. 

"We are devoted to teaching, training, and inspiring veterinary students," adds Dr. Pinto. "We have a shortage of vets at all levels in the United States. Farm animals are the most in need of more veterinarians. We hope as students come in rotation in Woodstock, some will heed the call to work with farm animals."