Department of Animal Production, Faculty of Agriculture, Bani Walid University, Libya
Friesian bulls ,semen ,Dry summer ,Humidity ,

The present study aim to analyze the semen production data of Friesian bulls in Libyacollected over a period of one year was analyzed to examine seasonal effects on quantity and quality of semen. Pure breeding bulls of Friesian (n = 18), maintained under naturally ventilated open-sided sheds, were used for semen collection. Meteorological information on ambient temperature, relative humidity and rainfall was used to divide the calendar year into two stressful summer seasons viz; dry summer (April - June) and wet summer (July–September) and a stress free season (October - March). The number of ejaculates per bull recorded during three seasons were not significantly different (P>0.05). Friesian bulls produced lower ejaculatory volume during dry summer season (P<0.05). Seasonal pattern of mass motility and individual motility of semen was different. The mass motility of semen was significantly lower during wet summer. However, individual motility in the semen of Friesian bulls did not differ among seasons (P>0.05). Wet summer resulted in reduced number of semen doses. The results of this study indicated that wet summer season deteriorated semen quality in terms of mass motility, individual motility and number of doses, except individual motility in semen of Friesian bulls.

7 , 2 , 2017