Reproductive Characteristics of Boars during and after Exposure to Increased Ambient Temperature2

Abstract

Reproductive performance of 12 ll-month- old Yorkshire boars was determined during and after exposure to control or increased ambient temperatures. After 3 weeks adjustment at 23 C in temperature controlled chambers, six boars were heat stressed by exposure to 34.5 + 1.0 C for 8 hr and 31.0 • 1.0 C for 16 hr during each 24-hr period and six control boars were main- tained at 23.0 + 1.0 C for 11 weeks. All boars were subsequently exposed to 23 C for 6 weeks. Semen was collected twice weekly before, during and after heat stress and boars were naturally mated with gilts during weeks 7 to 11 of treatment. Daily rectal temperatures and respiratory rates were increased during heat stress, but the ability to ejaculate and semen volume were not altered. Percentage motile sperm was decreased during heat stress (P