The investigations were carried out on the material of 570 ejaculates taken by manual metod from 30 boars used for insemination: Large White, Landrace, hampshire, duroc and pietrain. Young boars at the age of approximately 7-8 months, not used in reproductive per-formance, were chosen. One ejaculate taken from each boar in each successive month was ex-amined in sperm morphology. After collecting semen slides were immediately prepared. In each slide the morphology of 500 spermatozoa, including spermatozoa with proper proportions and showing major and minor abnormalities was evaluated. It was found that the percentage of nor-mal spermatozoa morphology shapes differently with boars of each breeds in particular months of the year. The semen taken from spring and winter had more spermatozoa with proper proportions than in the summer and early autumn period. The boars of wbp and hampshire breeds are less susceptible on influence of the seasonal factors, which appears profitable sperm mor-phological of every period of the year near insignificant amplitude of changes in next months of year. The semen quality of boars: Landrace, duroc and pietrain show the larger sensibility on operation of the seasonal factors.

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