EN
Values of selected parameters of milt from carp, Cyprinus carpio L., representing four breeding strains - the Lithuanian strain B (n = 12); the Hungarian strain W (n = 16), the Ukrainian strain Ur (n = 16), and the Polish strain 6 (n = 14) collected during the spawning season after stimulation with Ovopel (1 pellet/kg) were compared. Spermatozoa motility (%), their concentration in milt (billion/ml), total protein content in seminal plasma (mg/ml), as well as its osmolality (mOsm/kg) were determined. The activity of lactate dehydrogenase (LDH), acid phosphatase, and anti-proteolytic activity (APA) were also determined. Values obtained for the activity of the analyzed enzymes are presented in U/I. Significant differences were observed among the basic parameters of milt only in total protein content between males of the Ur and W strains (P < 0.01) and strain 6 (P < 0.05). Significant differences were not noted in the activity of LDH, AcP, or APA(P>0.05). High correlation coefficients (R = 0.862, P < 0.001 and R = 0.667, P < 0.01) between APA activity and total protein content in the seminal plasma of males from strain 6 suggest that protective proteins might constitute the main protein fraction in the seminal plasma of these fish.