Patterns of egg production across the lunar cycle in broiler breeder hens under tropical conditions.

1. This study evaluated whether lunar periodicity was associated with variation in productive traits and mortality in commercial broiler breeder hens. Production records from Cobb 500 heavy breeder hens (n = 17,548), collected between 2016 and 2021 on a commercial farm, were analysed.2. The synodic lunar cycle was divided into eight consecutive phases of approximately 3.7 days each. Two production seasons were defined according to rainfall patterns: December-April (wet season) and May-November (dry season). In addition, three laying periods were considered: early production (weeks 26-28), peak production (weeks 29-34) and late production (weeks 35-56).3. The lunar cycle significantly influenced the number of eggs laid, laying rate, percentage of hatching eggs and the number of cracked eggs (p < 0.01). The number of double-yolk eggs was not affected. Egg production decreased towards the middle of the lunar cycle and increased towards the final phases, with higher production around the new moon compared to the full moon.4. Significant interactions were observed between lunar phase and both production season and laying period. Mortality showed variation across the lunar cycle, with the highest values occurring around phase 6.5. These findings suggested that lunar periodicity may be associated with short-term variation in productive traits and mortality in commercial broiler breeder flocks, highlighting the potential relevance of lunar-associated environmental rhythms in avian biology.