Kentucky Thoroughbred Farm Manager's Club: Keeping Mares and Foals Healthy

The middle of foaling season was an appropriate time for farm managers in Central Kentucky to brush up on some of the finer points of keeping foals and mares healthy. Veterinarian Karen Wolfsdorf of Hagyard, Davidson, & McGee, and reproductive physiologist Bob Douglas shared some of their knowledge with the Kentucky Thoroughbred Farm Manager's Club on March 2 in Lexington. The group also got an update from Rusty Ford of the Kentucky Department of Agriculture on the current "CEM-like" virus being investigated.

Wolfsdorf began with a review of the importance of successful passive transfer, or foals receiving antibodies and disease-fighters through colostrum. Wolfsdorf explained that the part of colostrum (the sticky "first milk" to come from a mare) that is most important are the immunoglobulins, or IgG. Through research she found that foals needed sufficient IgG’s within 24 hours of birth to prevent general sickliness, as well as specific illnesses. She listed four factors that impact that absorption of immunoglobulins; the IgG concentration in colostrum, premature lactation (which can cause the colostrum to thin), the volume of colostrum ingested by the foal, and a foal’s inability to absorb IgG’s through their bloodstream. To prevent further problems, she recommended IgG testing.

Another problem she discussed is neonatal isoerythrolysis (NI). This is when the foal and the mare have different red blood cells. This often can be identified if the foal is jaundiced, or yellowed. If severe or untreated, it can be fatal. About 1-2% of foals suffer from this, but early steps can prevent this such as blood-typing the mare and screening for NI antibodies about two weeks before the foaling date.

Bob Douglas explained how measuring and monitoring hormone levels in mares, and sometimes stallions, can increase conception rates, plus can give more information about a mare’s cycles. For example, after ovulation, progesterone levels in the mare increase to over 1 nanogram per ml, until an egg is 20 days old. If a mare’s levels remain below that level, she is not pregnant, and will again go in heat. If progesterone drops below 2 1/2 ng, this is a good indication that the mare may have an infection, or be "dirty." After 300 days, the level of estrogens drop and progestagins again rise, reflecting fetal maturation. Douglas said low levels of both progestagins and estrogens are a red flag for the possibility of fetal dismaturity, which if caught, is treatable.

Douglas also discussed the effects of low thyroid function. Mares with normal thyroid levels are less likely to have abnormal estrus cycles or abort their foals. These levels are often raised by simply reducing a mare's feed or by keeping her out of her stall more often

In addressing the CEM-like problem in Kentucky, Ford said seven horses have tested positive for the organism; three stallions and four mares, all nurse mares originating from the same owner. Ford recommended if there are any questions about the status of a horse’s condition, that the horse be isolated; i.e., kept in a stall without other horses on either side, and kept in a paddock without fences adjoining other paddocks. Ford said clear record keeping may also help in tracking the disease. Every premise where a horse tested positive has been quarantined. Any questions on this should be directed to a veterinarian, the state veterinarian’s office, or the state department of agriculture.

About the Author

Kristin Ingwell Goode

Kristin Ingwell Goode was a staff writer for The Blood-Horse, a weekly Thoroughbred news magazine and a sister publication to The Horse.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More

Free Newsletters

Sign up for the latest in:

From our partners