EN
The studies were carried out on 6 stallions aged approximately 7 years in two consecutive copulation seasons. The stallions were clinically healthy and were of good sexual impulse and had a proper quality of the semen. They were fed fodder with poor Zn content and their diet contained 21.84 mg of Zn in 1 kg of fodder in the first season and only 17.53 mg in the second season. 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 alive spermatozoons and their morphology. In the plasma of the semen there was determined the concentration of total protein, the activity of basic phosphatase and the content of Zn, Cu and Ca. The studies showed that due to the insufficiency of Zn the semen quality might be of less value; the indices in reference to the semen quality were consistent with the content of Zn in fodder, hair, serum and plasma of the semen.