Climatic and Lunar Effects on Boar Ejaculate Traits

There is evidence that phases of the moon affect wild animal behaviors including reproduction. However, there is little evidence of moon phase effects on domestic livestock behavior. This study investigated the effects of moon phase and climatic variables on boar ejaculate traits. Records of 4,149 semen collections from boars of 9 different breeds were used. The response variables were volume of ejaculate, concentration of sperm in the ejaculate, and number of doses obtained per ejaculate. Moon phase, highest daily temperature (T), lowest daily T, average daily relative humidity (RH), temperature-humidity index (THI), season and the interaction of moon phase with season were analyzed at the day of collection and 45 days prior to date of collection as a proxy of initiation of spermatogenesis. For both dates analyzed, breed of boar, season and the interaction of season with moon had significant effects (P<.05) on the volume of the ejaculate. Moon phase had a significant effect (P<.05) on volume of ejaculate at the date of collection. Sperm concentration was significantly affected (P<.05) by breed, high and low temperature, THI, RH and the interaction of moon phase with season. Season showed a significant effect (P<0.01) on concentration of sperm at the initiation of spermatogenesis. For doses obtained/ejaculate, the effects of breed, season, moon phase and the interaction between season and moon phase were significant (P<.05) at collection date and at the initiation of spermatogenesis. A highly significant (P<.0001) interaction between season and moon phase was found for volume of ejaculate, sperm concentration and number of doses obtained per ejaculate at date of collection. Yorkshire boars had the highest volume of ejaculate (305.96±15.20ml) and Duroc boars had the lowest (167.55±13.21ml). Duroc boars showed the highest concentration of sperm (527.10±24.98x10⁶/ml). A significant effect of moon phase at the day of collection and 45 days prior was observed on the number of doses/ejaculate. The significant interaction of season and moon phase on boar semen quality traits suggests that to maximize productivity of modern swine production systems further investigation is needed.