An examination of the calcium and phosphorus nutrition of thoroughbred racehorses.

The study investigates calcium and phosphorus nutrition levels in thoroughbred racehorses, finding that a substantial portion of these horses receive inadequate calcium nutrition while on a high-grain diet during racing.

Study Methodology

• The researchers took samples of serum and urine from thoroughbred racehorses in Melbourne. A total of 90 horses were sampled in 1975 and 139 horses in 1980-81.
• Analysis of the samples focused on calcium (Ca) and phosphorus (P) levels. Measurements were taken for the amount of calcium and phosphorus being excreted, and their respective ratios to creatinine clearance.

Criteria for Adequate and Excessive Intake

• Horses with a calcium excretion greater than 15 mumole Ca/mosmole and a calcium to creatinine clearance ratio over 2.5% were considered to have sufficient calcium intake.
• On the other hand, phosphorus excretion greater than 15 mumole P/mosmole and a phosphorus to creatinine clearance ratio above 4% indicated excessive phosphorus intake.

Findings

• The study found that 60% of the horses examined had adequate levels of calcium intake, while 44% showed excessive levels of phosphorus intake.
• It was also observed that 25% of the horses were excreting more phosphorus in urine than calcium. This, according to the researchers, suggests that these horses are possibly dealing with nutritional secondary hyperparathyroidism.
• In fact, the horses of 53 out of 99 trainers who participated in races fell into this category.

Conclusion

• The research concluded that a high proportion of thoroughbred racehorses (around 40%) receive inadequate calcium nutrition. This is especially the case when they are on high-grain diets during racing seasons.