EN
The studies were carried out on 12 Polish ponies at the mean age of 7 years and body weight 380-410 kg during mating season (3 months) in April-June. Six stallions received СаСО₃ (experimental group) for 30 days, six non-treated ones served as a control. They were fed the natural fodder and their diet contained 23.96 mg of Zn, 3.76 mg of Cu and 3.96 g of Ca (control) and 12.49 g of Ca (experimental group) per 1 kg. The semen was taken by means of an artificial vagina and was assessed on the basis of the concentration of spermatozoons, their number in one ejaculation, the percentage of moving and live spermatozoons and their morphology. In the seminal plasma the concentration of total protein, the activity of alkaline phosphatase and levels of Zn, Cu, and Ca were determined. The studies showed that calcium excess in the fodder decreased semen quality significantly (especially with regards to concentration and total number of spermatozoa, percentage of mobile, live and normal spermatozoa) and the content of Zn and Cu in the seminal plasma in stallions.