The study involved giving breeder hens free access to low nutrient-dense feed and water allowing the hens to regulate their dietary intake according to their biological needs. The hens were weighed at 24 weeks and placed in pens of heavy, medium and light weight body weight hens. The Heavy, Medium, and Light hens weighed 27.6, 26.3, and 24.3 lbs. at 30 weeks and 25.6, 24.6, and 23.0 lbs. at 42 weeks.
Researchers found the light hens had significantly better hen-day egg production than either the medium or heavy hens, while the heavier hens produced significantly heavier eggs.
Additionally, across all three body weight groups, there was a significant decline in body weight between 30 and 42 weeks of age.