Broodmare Trace Mineral Levels Affect Colostrum Quality

The trace minerals copper and zinc are required for normal growth, development, and immune function in young horses. Nutrition of the mare during pregnancy and the young foal in the month after birth are also critical to proper development of weanling and yearling horses.

A study was carried out by scientists from the University of Guelph in Ontario, Canada, to monitor the trace mineral status of broodmares in gestation and to determine influences on colostrum and foal serum. In the study, 81 Thoroughbred and Standardbred broodmares on nine commercial breeding farms in Ontario were monitored monthly during the last trimester of pregnancy and during parturition. Blood samples obtained from the mares at each visit and from the foals at birth were analyzed for copper and zinc levels. Colostrum samples from the mares were analyzed for protein, immunoglobulin G (IgG), copper and zinc. The digestible energy, crude protein, and copper and zinc daily intakes of the mares were estimated.

Thoroughbreds and Standardbreds had a mean colostrum copper content and standard error of 0.71 ± 0.04 and 0.61 ± 0.03 mg/l, respectively. Mean broodmare serum copper levels showed a decrease during gestation. These values were in the low range of adequate serum levels for adults.

Foaling month significantly affected mare serum copper levels. Mare serum copper levels and colostrum copper concentrations were positively correlated. Both were positively correlated to estimated dietary protein and energy intake respectively.

Foal serum copper levels at birth were positively correlated to colostrum IgG and protein. There was an increase in mare serum zinc levels during gestation but these levels varied among the farms studied. Differences in mare colostrum copper levels could be due to farm management or genetic differences between breeds. Results of this study suggest that dietary and/or farm management practices could influence the serum copper and zinc status of broodmares.

Most fortified commercial feeds designed for broodmares contain adequate levels of minerals including zinc and copper. Owners should check with an equine nutritionist if they have questions about providing these minerals to broodmares.