In recent years, commercial laying hen and breeder operations have progressively shifted from conventional battery cages toward cage-free systems, with cage-free housing reaching 55% across the European Union in 2021. However, floor eggs remain a critical bottleneck in cage-free management, increasing manual collection labor while causing substantial economic and hygienic detriments from soiled or damaged eggshells. This seminar reviews three studies to elucidate how nest architecture, spatial preference, and genetics jointly influence floor egg incidence. First, floor laying exhibits moderate heritability (h2=0.39-0.52). Tracking Rhode Island Red and White Leghorn hens demonstrated that nest spatial dispersion (MDN, PNL) is moderately heritable (h2=0.18-0.37), whereas duration after laying (MDA) is highly heritable (h2=0.54-0.70) and genetically distinct from pre-laying occupancy (rg<+0.20). Breeding for higher nest dispersion and shorter MDA offers an effective approach to enhance nest turnover and mitigate floor laying. Second, evaluating nest attributes revealed that curtained enclosure is the dominant environmental driver for nest choice, overriding substrate texture preferences and reversing two-month-old site habits. Providing dark, secluded nests thereby eliminates the primary stimulus for hens to lay in facility corners. Third, spatial pattern analysis (SPI) across five broiler breeder lines confirmed that gregarious nesting is heavily regulated by genetics (P<0.0001) and represents a pre-laying specific motivation rather than general daytime social flocking. During laying peaks, nest overcrowding saturates corner capacity, directly driving floor egg occurrence (rs=0.28, P=0.002), while flock spatial distribution between litter and slats under male mating pressure indirectly regulates nest access. In summary, combining genetic selection for nesting efficiency, enhanced nest enclosure, and flock spatial management provides a comprehensive strategy to minimize floor eggs while safeguarding poultry welfare.
- Sun, J., N. Suzuki, T. Nii, and N. Isobe. 2024. Effect of different inflammation states on the antimicrobial components in milk of goat udders after milking cessation. Anim. Sci. J., 95(1), e13926.
- Sun, J-k., Z-L. Liang, T. Nii, N. Suzuki, and N. Isobe. 2025. Antimicrobial component concentrations in the milk of peripartum goats. Anim. Sci. J., 96(1), e70029.
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