Bone Breakage as Affected by Type Housing or an Exercise Machine for Layers

Experiments were conducted to evaluate the effect of exercise, housing practices and calcium source on the bone strength of laying hens. Dolomitic limestone was found to be inferior to calcium carbonate as a calcium source as indicated by weaker tibia strength when fed in equal or ⅓ higher amounts. Possibly the poorer availability of calcium was the cause of weaker tibias. Floor birds were found to have higher tibia breaking strengths and less broken bones compared to caged birds. Greatest differences were noticed in the number of broken wings, suggesting lack of exercise in cages as being a factor in bone weakness. Further studies involving daily exercise of caged birds in a treadmill resulted in higher humerus strength supported this conclusion. Floor birds had significantly higher (P < .01) bone breaking strength than either caged control birds or exercised birds, indicating either more exercise is required to strengthen bones or other factors might influence weak bones in caged birds. A device for exercising experimental birds is described.