Effect of 19-norandrostenololylaurate on semen characteristics of colts.

The long-term effects of the anabolic steroid 19-norandrostenololylaurate on semen characteristics of Finnhorse colts were studied in 3 experiments. Semen was collected initially at 24 months of age and then twice a year. In experiment I, 500 mg or 100 mg of steroid per animal was given every 3rd week from 12 or 16 months to 24 months of age. In colts treated with 500 mg of anabolic steroid every 3rd week, azoospermia was observed in 3 out of 5 colts in the first semen collections, immediately after the end of treatment. The other 2 colts had low sperm numbers and a high percentage of proximal droplets in relation to control animals. The 100 mg group was less affected by steroid treatment than the 500 mg group. The seminal changes were observed to be reversible. All of the colts had spermatozoa in their ejaculates 4 months after the end of treatment. Two years after cessation of treatment, sperm numbers in treated animals exceeded those in the control group. In experiment II, colts were treated from 7 months to 12 months of age with a dose of 1 mg/kg every 3rd week or 0.3 mg/kg every week. The first semen collections took place 12 months after the last treatment. The animals treated with 0.3 mg/kg every week were less affected than those treated with 1 mg/kg every 3rd week. In experiment III, animals were treated from 3 months to 8 months of age, and the interval from the last treatment to the first semen collection was 16 months. There were no significant differences between the groups in any of the semen parameters examined. In the last semen collection, the control animals had numerically higher spermatozoal concentration and progressive motility and less dead sperm than the treated animals. It was concluded that the adverse effects of steroid treatment on semen characteristics were reversible, at least in the groups treated at age 7-25 months.