The performance of 14.7 million commercial layers in 203 different flocks, located throughout the U.S. and representing 11 different White Leghorn strains was recorded and summarized. The records included weekly averages of hen day egg production, egg weight, feed and water consumption, dietary ME, BW, temperature, and mortality from 25 to 60 wk of age. These production characteristics were compared among age groups, strains, and strain groups in which each age group represented a 5-wk

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... , and each strain group represented the light, medium, and heavy strains. The distribution of flock-weeks by age group and temperature revealed a similar curve for all age groups; however, in general the younger flocks were kept at lower temperatures. The overall average temperature was 24.3°C and ranged from 15 to 30°C for individual flock weeks. Weekly feed consumption varied from 50.9 to 145.7 g/d and was correlated with BW, which varied from 1.12 to 1.91 kg/bird. Weekly egg production varied from 60.7 to 97.7%, and egg weights varied from 49.8 to 68.1 g/egg. A 7% difference in BW and a 39% difference in BW gain were noted between the heavy and light strain groups. Mortality was highest for the medium weight strain group. Negative correlations were observed between temperature vs. ME intake, hen-day egg production, and BW gain. Similarly, egg weight was negatively correlated to hen-day egg production and BW gain. The data described herein gave an indication of normal performance of commercial laying hens in the U.S. for a 9-yr period, 1992 to 2000, and should prove useful in development and testing of deterministic simulation equations.