Genetic Elements Called miRNA May Be Next Foaling Predictor

Preparing for foaling means different things to different people. Without question, though, knowing when a mare is likely to foal would mean a lot to most foaling attendants.

“The gestation length of mares is highly variable, spanning anywhere from 320 to 390 days. Further, ‘characteristic’ changes in the mare, such as waxing and laxity of the pelvic ligaments are also quite variable. This often leaves owners and farm staff lurking in the shadows of the barn at night or the wee hours of the morning waiting for a mare to foal,” said Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

Due to the risk of difficult birth, called dystocia, which occurs in about 10% of all foalings, most owners or farm managers prefer to be present for the birth of the foal. Being able to more accurately predict foaling would be valuable in terms of safety and reducing workload.

Various foaling predictors already exist, suggesting that none is yet the perfect predictor of foaling. Offering a novel approach, Japanese researchers suggested that small segments of genetic material called circulating microRNAs (miRNAs) could be used to predict foaling.^*

“Cells release miRNAs to regulate various physiologic processes such as cell proliferation, programed cell death, and even endocrine functions. Studies in humans have already identified parturition-related miRNAs, so researchers wished to determine if miRNAs related to parturition also existed in pregnant mares,” explained Crandell.

Fourteen healthy mares were recruited for this study. Researchers collected blood samples one month prior to parturition, then five, three, two, and one day prior to parturition, as well as on the day of parturition. They then compared circulating miRNAs to determine if any specific one significantly increased or decreased in the periparturient period to help predict foaling.

“This study identified 18 different miRNAs that were affected by proximity to parturition. Of those, five were significantly different at five days before parturition compared to thirty days prior to parturition. Two of those miRNAs were novel, whereas the other three were known miRNAs, previously identified and named,” shared Crandell.

According to the researchers, “This study provides basic knowledge of parturition-related circulating miRNAs in mares, and identifies miRNAs that could potentially be used as biomarkers to predict parturition in mares.”

From a nutritional standpoint, some important nutrient considerations for broodmare include feeding omega-3 fatty acids, such as those found in EO-3, which may help improve colostrum quality and enhance passive transfer of antibodies to the foal. Additionally, supplementing mares with omega-3 fatty acids may result in improved success for early rebreeding.

“For antioxidant protection throughout pregnancy, parturition and lactation, supplement broodmares with natural-source vitamin E, such as Nano-E,” added Crandell.

^*Kikuchi, M, H. Murase, K. Urata, T. Ishige, S.-I. Nagata, T. Tozaki, H. Kakoi, T. Ishiguro-Oonuma, and K. Kizaki. 2024. Evaluation of circulating miRNAs in mares approaching parturition. Domestic Animal Endocrinology 89:106879.