Influence of long-term treatment with equine somato-tropin (EquiGen®) on gonadal function in stallions with poor semen quality

The aim of the present study was to investigate the spermatogenic and Leydig cell activity in stallions with impaired semen quality after treatment with equine somatotropin. Experiments were performed using 18 adult clinically healthy stallions with poor semen quality which did not pass breeding soundness evaluation. The animals were randomly divided into a treatment (n = 9) and a control (n = 9) group. Over a period of 90 days, nine stallions received a daily intramuscular injection of 10 mg recombinant equine somatotropin (EquiGen®, BresaGen Limited, Adelaide, Australia) and 9 control animals were injected with the same amount of physiological saline solution. During and until 2 months after treatment, semen characteristics and daily sperm output as well as plasma testosterone concentrations were determined monthly in all stallions. In addition, testosterone concentration measurement after stimulation with hCG was performed in all animals immediately before and at the end of the treatment period as well...