Differences in diagnostic test results and hematologic data between aged and young horses.

The study compares blood tests and other diagnostic test results between old and young horses to identify possible changes related to aging. The researchers found significant differences in the blood samples and responses to glucose, which were probably due to age-related ailments in the horses.

Methods and Participants

• The study compared diagnostic tests and hematologic data between aged horses (at least 20 years old) and young horses (5 years or younger).
• Initial data came from two groups: group 1 consisted of 8 aged and 6 young mares, and the same data was later collected from group 2, containing 3 aged individuals (mares and geldings) and a mix of one mare and 5 geldings for the young group.
• Furthermore, a dexamethasone suppression test (DST) was carried out and necropsies were performed on group 3, which comprised of 6 mares and mare number 8 from group 1.

Findings and Interpretations

• The complete blood counts and serum biochemical profiles were compared between young and aged horses in groups 1 and 2.
• In aged horses, mean corpuscular volume, a measure of the average volume of red blood cells, was higher compared to young horses.
• The horses’ oral glucose tolerance and insulin responses to orally administered glucose were also tested and showed that in group 1, plasma ascorbic acid values were lower in aged horses than in young horses even when subjected to the same circumstances and diet.
• An age-related hyperinsulinemic response to orally administered glucose was notable in the horses in group 1. The study hypothesizes that this could potentially be due to a high incidence of subclinical hypophyseal (related to the pituitary gland) and/or thyroid adenomas (benign tumors) among the aged horses.
• These findings of adenomas were supported by necropsies on 13 older horses wherein 10 were found to have hypophyseal and/or thyroid adenomas. These adenomas were associated with hyperinsulinemic responses in group 2.
• All horses in groups 2 and 3 were subjected to a 24-hour DST.

Summary and Conclusion

• This study provides valuable insights into the hematologic and metabolic changes in aged horses where certain ailments such as adenomas are reflective in diagnostic tests and blood data.
• The focus on glucose tolerance and insulin response proves to be significant in this study as hyperinsulinemic responses observed in older horses were attributed to a high occurrence of adenomas.
• The researchers conclude that the same care and feeding regimen does not yield the same health results for horses of different ages and that age-related ailments significantly affect these outcomes.