When compared to cows, ewes, and sows, mares experience a short interval between birth and their next heat cycle. After foaling, the uterus undergoes involution, a process that reduces uterine size, repairs uterine tissues, and restores the uterine environment to a nonpregnant state. Commercial breeders typically prefer every-year foaling, which is difficult to maintain because of the 11-month gestation of the mare, so supporting uterine involution is critical. In a recent study, researchers set out to determine the effects of feeding docosahexaenoic acid (DHA), an omega-3 fatty acid, on uterine involution in the weeks after foaling.*
The Research Study Parameters
This study included eighteen pregnant mares. The mares were assigned to one of two groups, a treatment group in which a microalga rich in DHA was fed daily at 0.6 g/kg body weight or a control group. The treatment was fed from 90 days prior to the expected foaling date until seven days after the first postpartum ovulation. Otherwise, the mares were fed similarly to maintain moderate to moderately fleshy body condition, including access to Bermudagrass pasture and a commercial concentrate at a rate of 1 kg/day (2.2 lb/day) before foaling and 2 kg/day (4.4 lb/day) after foaling.
Reproductive health parameters were ascertained through rectal palpation and ultrasonographic examination, including uterine and endometrium diameters, intrauterine fluid, uterine tone, and uterine echogenicity. Echogenicity measures the ability of a tissue to reflect an ultrasound wave.
Mares fed the DHA-rich supplement had smaller uterine horn diameters after foaling compared to control mares. Interestingly, DHA-fed mares had greater uterine echogenicity scores. Low echogenicity is generally related to increased estradiol, which induces edema and estrus behavior, so researchers expected lower scores as mares readied for rebreeding.
The researchers observed no treatment effects for the other parameters evaluated.
Researchers concluded that “supplementation with DHA during peripartum may benefit uterine involution process and odds of early conception.”
“This research adds to the emerging volume of work that indicates omega-3 fatty acids, particularly DHA, is a useful nutritional supplement for broodmares,” explained Catherine Whitehouse, M.S., a nutritionist with Kentucky Equine Research. Studies in other species show omega-3s have beneficial effects on reproduction. These benefits include modifying prostaglandin synthesis/metabolism and regulating genes integral to uterine function.
“The source of omega-3 fatty acids is important. Choose a high-quality supplement that delivers DHA directly, such as marine-derived EO-3,” Whitehouse advised.
*Ferreira, J.R.D.M., S.B. Villela, C. Bianconi, M. Ormieres, G.D. de Melo, G. Pugliesi, and A.A.D.O. Gobesso. 2021. Uterine involution of mares supplemented with dietary algae-derived omega-3 fatty acids during the peripartum period. Journal of Equine Veterinary Science 106:103733.