Testicular biopsy in stallions: diagnostic potential and effects on prospective fertility

Testicular biopsy was performed as a standing procedure on fertile, mature stallions (n=7) under sedation and local anaesthesia. The 'Biopty' instrument was used to collect three samples from the left testis of each stallion. The oestradiol, testosterone and inhibin content in each testis were assessed by validated radioimmunoassay (RIA); protein concentrations were determined and the testes were prepared histologically for haematoxylin and eosin staining. The fertility status of each stallion was assessed before and after testicular biopsy by semen evaluation, changes in total scrotal width, pregnancy rate per oestrous cycle, serum and seminal plasma antisperm antibody concentrations, and determination of plasma LH, FSH, oestradiol, testosterone and inhibin concentrations once a week by validated RIA. Testicular testosterone (3.85 +/- 1.24 ng mg(-1) protein), oestradiol (3.01 +/- 0.95 ng mg(-1) protein) and inhibin (11.06 +/- 1.69 ng mg(-1) protein) content were measured successfully from tissue samples by RIA. Active spermatogenesis was evident in all histological samples. The mean numbers of progressively motile morphologically normal spermatozoa were not significantly different in the last three ejaculates of the 7 day periods of semen collection before (3.37 +/- 0.48 x 10(9) spermatozoa per ejaculate) and after (3.77 +/- 0.48 x 10(9) spermatozoa per ejaculate) testicular biopsy. Total scrotal width varied within normal ranges throughout the year (from 11.7 +/- 0.3 to 10.0 +/- 0.4 cm). Pregnancy rates per oestrous cycle before (50 +/- 6%) and after (63 +/- 9%) testicular biopsy were not significantly different. The concentration of antisperm antibodies in serum and seminal plasma samples did not vary significantly before and after testicular biopsy. Plasma LH, FSH, oestradiol, testosterone and inhibin concentrations fluctuated within normal ranges after biopsy in the expected seasonal pattern. In conclusion, the present study demonstrates that using the 'Biopty' instrument to obtain testicular biopsy samples from stallions has no apparent detrimental effects on prospective stallion fertility and can be used to evaluate testicular factors and structure.