Lunar and climatic effects on boar ejaculate traits

There is evidence that phases of the moon affect wild animal behaviors including reproduction. There is, however, little evidence of moon phase effects on domestic livestock reproduction. This study investigated the effects of moon phase and climatic variables on boar ejaculate traits. Records of 4149 semen collections from boars of nine different breeds at one boar stud were used. The response variables were volume of ejaculate, concentration of sperm in the ejaculate, and number of doses obtained per ejaculate. Moon phase, greatest daily temperature (T), least 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 season and the interaction of season with moon had significant effects (P < 0.05) on the volume of the ejaculate. Moon phase had a significant effect (P < 0.05) on volume of ejaculate at the day of collection. Sperm concentration was affected (P < 0.05) by the interaction of moon phase with season, high and low temperature, THI, RH and breed. Season had an effect (P < 0.01) on concentration of sperm at the initiation of spermatogenesis. For doses that could be used for AI that were obtained/ejaculate, there were effects of moon phase, season, the interaction between season and moon phase and breed (P < 0.05) at collection day and at the initiation of spermatogenesis. There was an interaction (P < 0.0001) between season and moon phase for volume of ejaculate, sperm concentration and number of doses obtained per ejaculate at date of collection and at day of initiation of spermatogenesis. The significant interaction of season and moon phase on boar semen traits suggests that to maximize productivity of modern swine production systems determining a collection schedule in some seasons relative to moon phase may be advantageous.