Influence of season on characteristics of epididymal and ejaculated semen in Meishan boars

Most of the epididymal spermatozoa collected in all the seasons examined maintained an ability to move progressively, had a cytoplasmic droplet in the distal site of the middle piece, and were morphologically normal. Reduced desire to mount a dummy was not observed during the experimental period. Characteristics of ejaculated semen were not significantly altered throughout the year. However, progressive motility and acrosomal integrity of spermatozoa ejaculated between July and September were more susceptible to storage at 4 degrees C than spermatozoa ejaculated during the other months and acrosomal integrity of spermatozoa ejaculated during the 3 months was to freezing-thawing. These results indicate that the reproductive activity of Meishan boars in Japan is only slightly influenced by season, but semen ejaculated during the summer is less suitable for storage than that ejaculated during the other seasons of the year.