A study was done of 4 different types of hens to see if they had different reactions to cages or floor pens. Each genotype was put in a cage or a floor pen. After 50 weeks they were killed and their bones were examined. There was little differences found between the gene type of the hens and bone structure. It was found that birds kept in floor pens had a heavier radius than birds kept in cages, but the tibia was not different. The researchers suspect that because caged birds can still stand they are able to put weight on their tibia’s.