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

Authors:
Publisher website
Google Scholar
Abstract
SUMMARY: Hematologic data and results of diagnostic tests were compared between aged (≥ 20 years old) and young (≤ 5 years old) horses to identify hematologic and metabolic changes associated with aging. Initial data were obtained from 8 aged and 6 young mares (group 1). Similar data were collected from a second group of aged (3 mares and 3 geldings) and young (1 mare and 5 geldings) horses (group 2). Dexamethasone suppression tests (dst) and necropsies were performed on 6 additional mares and mare 8 from group 1 (group 3). Complete blood counts and serum biochemical profiles were compared between young and aged horses of groups 1 and 2. Mean corpuscular volume was higher (P < 0.05) in aged horses. Oral glucose tolerance and insulin response to orally administered glucose were measured in 13 aged horses (groups 1 and 2) and 6 young mares of group 1. In group 1, plasma ascorbic acid values were lower (P < 0.05) in aged horses than in young horses maintained under the same conditions and feeding regimens. An apparent age-related hyperinsulinemic response to orally administered glucose identified in group-1 mares was probably a result of a high occurrence of subclinical hypophyseal and/or thyroid adenomas. Of 13 aged horses necropsied (groups 2 and 3), 10 had hypophyseal and/or thyroid adenomas that, in group 2, were consistently associated (P < 0.05) with hyperinsulinemic responses to orally administered glucose. All horses in groups 2 and 3 were given a 24-hour dst. Failure to maintain suppression of serum cortisol values 24 hours after dexamethasone administration was correlated (P < 0.05) with the presence of hypophyseal and thyroid adenomas whether or not clinical signs were apparent. There were no apparent changes in oral glucose tolerance, insulin secretion, or dst attributable to aging alone. Seemingly, there were no age-related changes in serum biochemical profiles or cbc in aged horses other than an increase in mean corpuscular volume.

This publication has 10 references indexed in Scilit: