Influence of Elevated Ambient Temperature on Reproductive Performance of Boars

Abstract

Twelve Yorkshire boars were randomly assigned to one of two temperature controlled chambers to determine the influence of elevated ambient temperature on reproductive performance. Heat stressed boars were exposed to 34.5 ± 1.0 C for 8 hr and 31.0 ± 1.0 C for 16 hr daily for 90 days. Control boars were maintained at 23.0 ± 1.0 C throughout the experimental period. Semen was collected twice weekly to determine sperm output and quality. Semen volume and gel weigh per ejaculum were not altered during elevated ambient temperature. However, sperm motility and percent normal cells with non-aged acrosomes decreased and the percentage of abnormal cells and cells with aged acrosomes increased by the second week of treatment. Sperm output was reduced in stressed boars during weeks two through six of treatment. Only 28.6% of 77 gilts bred with semen from stressed boars conceived compared to 41.2% of 88 gilts bred with control semen. At day 30 ± 3 of pregnancy, embryonic survival was 71.2 ± 3.7% in gilts bred with semen from control boars and 48.5 ± 5.2% for gilts bred with semen from stressed boars.