144 Serum testosterone profile in Marwari stallions and its relationship with testicular parameters, semen characteristics, reaction time, stallion age, bodyweight, and height

Abstract

The present study investigated the serum testosterone profile of Marwari stallions before and after exposure to a mare and the relationship of serum testosterone profile with scrotal circumference, semen characteristics, reaction time, stallion age, bodyweight, and height. Marwari stallions (n=9) of three age groups (2-4 years, n=3; 4-6 years, n=3; and 6+ years, n=3) were used in the study. Scrotal circumference, height, and bodyweight of each of the stallions were measured. Semen was collected from each stallion twice per week in the early-morning hours using an artificial vagina and a mare in oestrus. Six ejaculates were collected from each stallion for evaluation of various seminal parameters (semen volume, sperm concentration, and progressive sperm motility). Reaction time for each stallion was also recorded. At every alternate semen collection (first, third, and fifth collections), blood samples were taken 15min before exposure to the mare and just before the semen collection for serum testosterone hormone assay using a horse testosterone enzyme-linked immunosorbent assay kit. The data obtained were analysed statistically using SPSS ver. 20.0 (IBM Corp.). The results showed that mean testosterone concentration was significantly different (P ≤ 0.01) among the stallions and was significantly lower (P ≤ 0.01) in the stallions below 4 years of age. No significant difference in testosterone level was observed before and after exposure to a mare. A positive correlation was detected between testosterone and both scrotal circumference (P ≤ 0.05) and sperm concentration (P ≤ 0.05), whereas a negative correlation was observed with reaction time (P ≤ 0.01). It was concluded that exposure to a mare does not change the testosterone level in stallion blood and that there is a relationship of serum testosterone concentration with scrotal circumference, sperm concentration, reaction time, and age but not with height and bodyweight.