Four rams of Polish long-wool sheep were intensively used in course of one year in an experimental scheme: 10 periods of semen collection, 10 ejaculation daily for 10 consecutive days in each period. It was found that the concentration and number of spermatozoa decreased significantly in the last (10th) ejaculates compared to the first ones. Apart from these qualitative changes connected with intensive use of the animals, it was also noted that the season of semen collection affected semen quality. The highest concentration and number of spermatozoa was observed in the ejaculates collected during the period November-March, the lowest ejaculate volumes were recorded in spring, whereas percentage of spermatozoa with damaged acrosomes was noticeably higher in July and August. Increased frequency of ejaculation was connected with possibly lower share of epidydimis secretion in the ejaculate. This resulted in considerable decrease of the activity of plasmatic proteinase inhibitors in the last (10th) ejaculates. Studies showed that changes in the inhibitor activity in ram seminal plasma in the annual cycle were caused by variations in the intensity of secretion of these substances, as well as bonding of the inhibitors by proteinase liberated from damaged acrosomes. Intensive sexual exploatation of rams may lead to some disturbances in the system protecting seminal proteins against unspecific proteolysis.