The Effect of Drip Cooling System on Reproductive Performance of Boars Exposed to Heat Srtess

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After the six years of studies since 1985 concerning the effects of heat stress on the testicular functions of boars, we confirmed that the reproductive performance of boars exposed to 30-35ﾟC for 3 to 6 week were deteriorated. Based on the results, we have been studying the prevention measure of heat stress on boars with a thermography for a couple of years since 1989 receiving this grant in aid for scientific research. We studied the effectiveness of drip cooling system which emits small droplets of water on the boar's neck in the first year. The results showed that the application of the system to boars fed under 29-30ﾟC natural environment lowered the skin temperature of the boars from 2 to 3ﾟC. In the second year, two experiments were carried out using the environmental controlled chamber where total 6 boars were exposed to 24ﾟC (control) for 3 days and then to heat stressed treatment (33ﾟC for 10 h and 14ﾟC for 14 h daily) for 4 weeks. In the experiment 1, water droplets were dripped for one minute in every 11 minutes to the neck, shoulder and scrotum of the boars to study the effective part of the body for the reduction of heat stress. The results indicated that dripping on the neck of boars was the most effective. In the experiment 2, we investigated the physiological responses (heart rate, respiration rate, rectal temperature and skin temperature) and the testicular function of boars at controlled and elevated ambient temperature (33ﾟC) when water droplets were dripp on the neck of boars. The results showed that the drip cooling reduced about 1ﾟC in both rectal and skin temperatures although heart and respiration rate were not affected. In conclusion, we confirmed that the drip cooling system was the effective practice to prevent heat stress of boars in summer.