Effects of excess vitamin D3 and cage density on the incidence of leg abnormalities in broiler chickens.

A 2 X 2 factorial experiment was designed to investigate the effects of excess vitamin D3 and cage density on the incidence and severity of leg abnormalities in broiler chickens. One hundred eighty 1-day-old broiler chicks were randomly divided into densities of either 10 (680 cm2/chick) or 20 (340 cm2/chick) per cage and fed a diet containing 22% protein and 2879 kcal/kg metabolizable energy formulated to meet National Research Council requirements. Two levels of vitamin D3 were incorporated to supply either 400 ICU or 4000 ICU/kg feed. High density and excess vitamin D3 resulted in a significant (P less than 0.05) increase in the incidence of twisted leg. Differences in incidence could not be explained through differences in body weight or feed consumption. However, broilers fed the excess vitamin D3 consumed more feed but gained less body weight, suggesting that metabolic stress may have been involved. High density appeared to increase the severity of the disorders, whereas excess vitamin D3 had no effect on severity.