Schatte, Margaret, authorGrandin, Temple, advisorPinedo, Pablo, advisorKeller, Kayleigh, committee member2024-09-092024-09-092024https://hdl.handle.net/10217/239176Myths and old farming legends have circulated the belief that the full moon affects livestock behavior and reproduction. To assess this association in dairy cattle, 13,558 records from 2019 to 2021 at an organic dairy farm in Colorado were analyzed. These records included lactation number, artificial insemination date (AI date), and pregnancy result. AI date was categorized into season and lunar phases. Lunar phases were separated into four equal categorizations: new moon, first quarter, full moon, and third quarter. The primary objective of this study was to identify any associations between the lunar phases and PAI1 (pregnancy rate at first AI). The secondary objective of this study was to use logistic regression to specify which phases had the lowest and greatest PAI1 while accounting for other effects on fertility. Logistic regression was used to complete this by comparing the pregnancy result of lunar phases while accounting for lactation number and season, which are known to affect pregnancy rate. The 4 lunar phase categorizations did have an association on PAI1 (p<0.05). The new moon phase resulted in the lowest PAI1 at 35.3% while the third quarter was the highest at 38.3%. Estimated marginal means were explored to identify the seasonal effect on pregnancy and found that winter had the highest probability of pregnancy and summer had the lowest. This analysis of 3 years of records provides evidence that the week of the new moon is the least probable week out of the month for pregnancy after first AI to occur, while the week before and week of the full moon are the most probable days for pregnancy after first AI to occur within the lunar cycle.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.dairy cowsartificial inseminationlunar cycleText