Lactation in the horse: the mineral composition of mare milk.

The research investigates changes in the mineral composition of mare’s milk during lactation, noting that minerals in the milk except sodium and potassium decreased over time.

Methodology

• The study was conducted on five Thoroughbred mares, with milk samples being collected one to three times weekly from the first to the eighth week of lactation. For two mares, this continued for an additional 8 weeks.
• The milk samples were collected after oxytocin, a hormone that stimulates milk release, was administered to the mares.
• Samples, averaging 500 mL, were then analyzed for different constituents including total solids, ash, calcium, phosphorus, magnesium, sodium, potassium, copper and zinc.

Findings

• Almost all constituents (except sodium and potassium) decreased in concentration throughout lactation. This implies that a mare’s milk changes in composition as lactation progresses, with minerals generally decreasing.
• The rates of decline for ash, calcium, phosphorus, and magnesium were similar. However, the decline rates of other elements were different. This suggests that different elements in mare’s milk are affected differently over the lactation period.
• Specifically, the data show that total solids and ash content were 12 and 0.61% respectively, at the end of the first week of lactation, 10.5 and 0.45% at 4 weeks, 10 and 0.38% at 8 weeks, and 10.2 and 0.32% at 16 weeks. This shows a continuous decline for these constituents throughout the lactation period.
• Calcium, phosphorus, and magnesium concentrations at the end of the same periods respectively also decreased over time. Copper and zinc concentrations showed a similar trend.

Conclusion

• The findings indicate that the mineral composition of mare milk varies depending on the stage of lactation. Therefore, the nutritional content of mare’s milk should be described with consideration to the mare’s lactation stage.