Prolactin Does Not Improve Colostrum Quality in Mares

In addition to supporting hundreds of other roles in a horse’s body, the hormone prolactin most notably contributes to milk production. More specifically, prolactin stimulates development of the mammary gland, and induces and maintains lactation. What it does not appear to do, according to one recent study*, is increase the concentration of immunoglobulins (Igs)—infection-fighting proteins—in mammary secretions, including colostrum.

The study set out to determine the impact of increased levels of prolactin on Ig levels in the blood, colostrum, and milk of mares. To do so, 12 pregnant mares were recruited, half of which were administered sulpiride to stimulate prolactin production.

“Researchers found that simply increasing prolactin levels by administering sulpiride did not affect colostrum quality,” explained Kathleen Crandell, Ph.D., longtime nutritionist at Kentucky Equine Research (KER) team.

Although circulating prolactin levels increased following administration of sulpiride, and Ig levels also increased in the bloodstream of treated mares, these increases were not accompanied by higher levels of Igs in colostrum.

Crandell added, “Improving colostrum quality by increasing Ig levels would be helpful for mares that previously had poor colostrum quality or experienced failure of passive transfer, but simply stimulating prolactin does not appear to be an effective means to achieve this goal.”

An alternative and possibly more successful method of improving colostrum quality includes dietary supplementation with omega-3 fatty acid products containing biologically relevant levels of DHA and EPA.

“KER offers EO•3, which contains 6,750 mg of EPA and DHA per serving that can be top-dressed on your horse’s daily ration,” advised Crandell.

*Migdał, A., Ł . Migdał, A. Zagrajczuk, et al. 2017. Influence of sulpiride treatment on the level of prolactin and immunoglobulins in the peripheral blood of mares during the postpartum period. Acta Veterinaria Hungarica. 65(3):417-428.