Serum Cortisol and Its Correlation with Leucocyte Profile and Circulating Lipids in Donkeys (Equus asinus)

Abstract

The values for basal serum cortisol concentrations of horses are available in many studies. However, there are limited data about serum cortisol in donkeys. The present study aimed to determine the baseline values for serum cortisol, to evaluate the influence of age and pregnancy on its levels, and to correlate its values with leucocyte profile, serum cholesterol, and triglycerides. Serum samples were collected from 97 healthy donkeys. Cortisol was analyzed by chemo-luminescent assay. The median and the 2.5th and 97.5th percentiles of serum cortisol measured and calculated in all donkeys were 5.64, 3.40, and 10.54 µg/dl, respectively. Females (n.91) were divided into three groups: Group A (young), Group B (adult), and Group C (pregnant at the 9th–11th months). The effect of age and physiological status was investigated by the Mann–Whitney test. Group C showed significantly higher levels than Group B (p < 0.05). Significant correlations were found in Group B with monocytes (r = 0.37, p < 0.01) and triglycerides (r = 0.30, p < 0.05), and in Group C with monocytes (r = 0.79, p < 0.01), basophils (r = 0.6, p < 0.05), and neutrophil/lymphocyte ratio (r = −0.63, p < 0.05). Higher cortisol values related to late pregnancy are also found in this species. These preliminary results provide evidence for a relationship between cortisol and the immune system as well as cortisol and lipid metabolism modulated by age and pregnancy when parameters are within normal values.

Role of Cortisol in Horse’s Welfare and Health

“…The nominal or basal value of plasma cortisol concentration in horses typically falls within a specific range, although it can vary based on factors such as the horse's age, health status, and circadian rhythm. The literature offers a reference range for basal cortisol concentration in equines, so that according to available reports, healthy adult horses exhibit resting basal cortisol concentration that typically range from 30 to 395 nmol/L [22,35,80,81]. The reference range provided offers a guideline for what is considered normal or nominal basal cortisol concentration in adult, healthy horses.…”