The effect of photoperiod on selected parameters of boar semen

The objective of the present research was to determine the effect of increasing and decreasing natural photoperiods on selected parameters of boar ejaculates. The study material consisted of 17 boars: six Polish Large White (PLW) breed, five Polish Landrace (PL) breed, and six Duroc×Pietrain (D×P) crossbreed, all aged between 8 and 12 months at the beginning of the research. Analyses were conducted on 612 ejaculates, which were collected in two experimental periods: an increasing photoperiod (IP) (January–June) and a decreasing photoperiod (DP) (July–December). A statistically proven impact of photoperiod on the volume of semen was observed in all the studied breeds (P=0.004). During the decreasing photoperiod the mean volume of semen was 261.16±75.20 ml and this was almost 17 ml higher than that for the increasing period. For boars involved in the experiment, day length also had a significant impact on the total number of motile spermatozoa (P=0.037). In the increasing photoperiod the mean number was 3.26×10⁹ lower. A decreasing photoperiod has a positive affect on both boars and the parameters of the collected ejaculates, which were observed in the higher number of insemination doses per ejaculate. Between the different breeds, the reactions of boars to photoperiod differed and the most significant influence of photoperiod on semen parameters was noted among D×P breed boars. Least susceptible to changes in day length were PLW breed boars.