Sexual behaviour and semen characteristics of boars: effects of high temperature

Abstract

The effect of 4,7 or 10-day periods of high air temperatures on the sexual behaviour and semen characteristics of mature Large White crossbred boars was determined in three experiments. In experiment 1, boars kept at 40¦C for 8 hours and 30¦C for 16 hours each day for 7 days had lower courting behaviour activity when tested at 40¦C than control boars tested at <25¦C. After similar heat treatment in experiment 2, boars tested at 30¦C showed no significant differences in courting or copulatory behaviour from control boars, but the semen of two of six treated boars showed evidence of severe testicular- epididymal dysfunction. The semen of a third treated boar showed evidence of moderate testicular-epididymal dysfunction. In experiment 3, four boars were given a similar daily high temperature cycle to the above, either for 4 or 10 days. Two of the four boars given high temperatures for 10 days had semen with signs of severe testicular-epididymal dysfunction. The semen of the other two boars in this group, and one boar treated for 4 days, showed evidence of moderate dysfunction. It was concluded that during hot weather boars will mate normally during the cooler part of the day, and that they are able to tolerate short periods of heat stress (< 4 days) without detriment to semen characteristics. Protection from longer periods of high temperatures ( > 7 days) is necessary.