Bone fragility in broilers as affected by pen height, sex, and a comparison of left and right humeri

Humeri and tibiotarsi breaking strengths were determined for broilers raised in pens of varying heights. Five hundred forty-four broilers were reared in conventional floor pens or wire cages on the floor with overhead restrictions of 20, 30, 40, or 60 cm. No significant differences were noted on growth, feed conversion or tibiotarsi breaking strength. Height-restricted broilers had significantly weaker humeri than did the controls. A significant linear relationship (P less than .05) was noted in height-restricted broilers in that as pen height increased so did humeri strength. Further studies were conducted to test for significant differences between male and female humeri strength and between right and left humeri on the same bird. Forty-six pairs of female and male humeri were obtained, tagged for identity, and broken on the Instron Model 1122. Males had significantly stronger humeri than females and right humeri were significantly stronger than left humeri in both sexes.