Research

Carleigh Fedorka, Ph.D.

Inflammation of the reproductive tract is considered the greatest concern in reproductive medicine. Mares that struggled with prolonged inflammation are considered susceptible to the disease of persistent breeding-induced endometritis (PBIE). This disease is noted in roughly 15% of all mares, but is observed at greater rates in aged mares, mares that struggle with their metabolism, and mares that have poor reproductive conformation. The inability to clear the uterus can lead to infection, early embryonic loss, or even pyometra. This can lead to both an emotional and financial burden to breeders, as the repeat failed cycles can accumulate with frustration.

One of the primary ingredients in red wine, a protein called resveratrol, has been found to be anti-inflammatory, antioxidant, and even anti-cancer. Therefore, we wanted to evaluate the impact of resveratrol on PBIE. We hypothesized that mares fed resveratrol would have decreased inflammation in their uterus post-breeding. To assess this, we identified six mares that were susceptible to PBIE. The mares were fed 2,800 grams of resveratrol (Metaborol®; Equithrive, USA) every day for the duration of one estrus cycle. Following, mares were bred and then evaluated for inflammation of their uterus. We found resveratrol to significantly decrease the number of neutrophils found on cytology and in fluid collected during lavage.

Moving forward, we intend to head into the lab and process the remainder of our samples, as we also collected endometrial biopsies, uterine fluid, and serum. This will include measuring immune signaling molecules in uterine fluid and circulation using an immunoassay, and assessing the molecular pathways activated within the reproductive tract by this product. Following this, we hope to determine if resveratrol improves fertility in this population of sub-fertile animals. We hope to provide breeders with an additional option in improving reproductive performance in their mares; one that can simply be top dressed onto their feed every day.

Patricio Razquin, D.V.M., DACT

Overall broodmare health is required for pregnancy maintenance and delivery of a live foal, and a normal microbiome of the gut and uterus has been associated with healthy offspring. But, how important the microbiome is to pregnancy success is unknown. Bacterial metabolites that may contribute to healthy equine reproduction are short-chain fatty acids (SCFAs); the most abundant are acetate, propionate, and butyrate.

Our current research seeks to determine the role of SCFAs in the development of the equine placenta and fetus. The equine placenta is unique because it develops chorionic girdle trophoblast cells early in pregnancy. This band of specialized cells will migrate into the mare’s endometrium to form the essential endometrial cups, which secrete equine chorionic gonadotropin (eCG), a hormone required for pregnancy maintenance in the mare during the first third of gestation. The cells that form the chorionic girdle express receptors for SCFAs at the critical point of endometrial invasion, suggesting that SCFAs may play an important role in this critical pregnancy event. With our studies we expect to better understand the interaction of the chorionic girdle and SCFAs during equine pregnancy.

Jenny Sones, D.V.M., Ph.D., DACT
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Advancing the first ovulation of the year is a rate-limiting step in equine breeding programs. Artificial light is the most reliable method but can be challenging for large groups of mares maintained outside. Typically, this requires mares being under artificial lighting for about 60 days. Therefore, an alternative method requiring less time to hasten ovulation in the deep anestrus mare is desirable.

Sulpiride, a dopamine antagonist, in estrogen-primed deep anestrus mares increases prolactin and luteinizing hormone concentrations. To test this for the first time in Colorado, 12 mares (10-19 years) were housed in January 2025 at CSU without artificial lighting. Mares received estradiol cypionate (ECP) and sulpiride. All treated mares developed a 30–35-millimeter follicle with uterine edema between seven to 18 days after treatment, whereas none of the vehicle-treated mares exhibited follicular development (less than 30 millimeters). Ten of the 12 total treated mares developed a follicle more than or equal to 35 millimeters and uterine edema (11.4 plus or minus 1.5 days). One mare spontaneously ovulated, whereas 71.4% of the remaining mares ovulated after an ovulation induction agent. One mare developed a hemorrhagic anovulatory follicle. On days five and 12-14 after ovulation, serum progesterone concentrations of ovulated mares were 7.7 plus or minus 1.02 and 7.9 plus or minus 0.3 nanograms per milliliter, respectively.

These levels are considered adequate to maintain pregnancy. Treatment of noncycling mares with ECP-sulpiride significantly hastened follicle development and ovulation in CSU mares. This hormone combination may be clinically useful in both individual mares and large groups of embryo recipient mares.

Elaine M. Carnevale, D.V.M., Ph.D.

Research in the Carnevale lab centers on oocyte and sperm, including factors that affect their viability and function and, subsequently, fertility of mares and stallions.

Dr. Raul Gonzalez-Castro is studying stallion variability and sperm modifications associated with successful conventional in vitro fertilization. Sperm changes associated with capacitation, that are needed for in vitro fertilization and fertility, vary with stallion, sperm state, freezing method, and sperm handling. Therefore, understanding capacitation is essential to understand stallion fertility with insemination or assisted fertilization. Using this information, Dr. Gonzalez-Castro is studying the success of conventional in vitro fertilization in aged mares.

The impact of semen-associated extracellular vesicles is being studied by Allie Ash to determine how these cell-secreted vesicles affect sperm capacitation. Because the stallion’s diet can impact its ability to withstand oxidative stress, a study is also being conducted on the effect of targeted nutritional supplements on sperm viability and fertility.

We are continuing to study the impacts of maternal factors on quality of the ovarian follicle and oocyte, to better understand mare reproduction and management. The effects of feeding grains and sugars on the older broodmare’s follicle is being assessed, with preliminary results suggesting that the feed supplements impact energy substrates and signaling within the ovarian follicle.

In an ongoing study, Cheyenne Elliott and the group collected oocytes and follicle cells from older mares with PPID (Cushing’s disease) and/or insulin resistance to study the impacts of these endocrine metabolic dysfunctions on metabolism of the oocyte and surrounding cells, as the metabolic activity of these cells is critical for oocyte viability and mare fertility. In addition, ovulation failure is a common cause of reduced fertility in older mares, so we are studying the impact of the metabolic endocrine diseases on key signaling molecules within the preovulatory follicle, as well as obtaining preliminary information into the success of in vitro fertilization and early embryo development in affected mares.