Data of four layers flocks (#31-34) from North Carolina Layer Performance and Management Test of the Department of Agriculture and Consumer Services were used in the meta-analysis to find if an increase in space allowance can affect egg production traits in white and brown layers. Effects of space allowance of 310 and 413 cm2/bird on layers performance were compared in this study. The increase in space allowance resulted in a significant improvement in egg production, egg mass and daily feed intake in both white and brown layers throughout the first (approximately 490-d; P < 0.001) and second (approximately till 760-d; P < 0.05) cycles of egg production. Space allowance did not affect age of maturity and final body weight at the end of first egg production cycle in both types of layers. Increasing birds space allowance resulted in a reduction in the mortality rate of white layers (P < 0.001) in the first egg production cycle and in the first (P=0.015) and second (P=0.027) egg production cycles in brown layers. The increase in space allowance significantly improved egg weight (P < 0.001) in white layers in the first egg production cycle. A significant increase in egg weight was observed in the first (P=0.014) and second (P=0.050) egg production cycles in brown layers in response to increasing birds space allowance. Egg size distribution was significantly influenced by the space allowance during both egg production cycles in white and brown layers. Space allowance is a management tool that can be used to optimize egg production traits, mortality and egg size distribution in both white and brown layers. Space allowance of 413 cm2/bird could significantly improve egg production and egg size distribution in first and second egg production cycle compared to 310 cm2/bird.

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