Abrstract. The aim of the study was to analyse the influence of a breed/crossbreed of young boars, at the age from starting the exploitation till the end of their first year of life on selected biological features of their semen and on the number of doses which can be made from one ejaculate. An attempt has been made to determine the influence of age on features of semen in Polish Large White (PLW) breed and crossbreed boars – Hampshire x Duroc (Hamp x Dur). The material under investigation consisted of the total of 7 719 ejaculates taken from boars belonging to Polish Landrace (PL) breed, PLW breed and from crossbreed boars Hamp x Dur, used at the insemination station in Kraśnik. The investigated boars were divided into two groups, depending on their age: the first group comprised boars at the age from starting the exploitation till the end of their first year of life, and the second group consisted of boars at the second year of life. Ejaculates were compared with respect to their volume, concentration of spermatozoa, percent of progressive motility spermatozoa and the number of insemination doses obtained from one ejaculate. The results of the study have shown that the parameters of ejaculates of young boars of the investigated breeds varied considerably. Young boars belonging to PL breed were characterized by the largest volume of ejaculate and the largest percent of progressive motility spermatozoa; also the largest number of insemination doses which could be made from one ejaculate in the case of these boars. Crossbreed boars Hamp x Dur were characterized by the highest concentration of spermatozoa (422.76 thousand per mm³). Age of young boars belonging to PLW breed had a significant impact on all the analysed features; in the case of crossbreed boars Hamp x Dur no distinct changes in ejaculates taken from boars which were up to up to 24 months old were observed only in the concentration of spermatozoa. High breeding potential, which manifested itself in the number of insemination doses (above 20), was also observed in the case of boars belonging to PLW breed and crossbreed boars Hamp x Dur at the second year of life.

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