Effects of dietary aluminum and niacin on chick tibiae.

Effects of dietary aluminum chloride and niacin on bone mineral content and bone structural measurements were studied using young male Leghorn chicks. Standard chick rations containing .8% Ca and .4 or .5% available P were fed as control diets in three experiments. Experimental diets contained .05, .1, or .3% Al, or 1.0 or 1.5% niacin, or both and were fed for 2 wk. Tibia weights were decreased by 1.5% niacin, .3% Al, and by .1% Al plus 1.5% niacin (P less than .05). Breaking strength of tibiae was decreased (P less than .05) by 1.5% niacin, .1% Al, and .1% Al plus 1.5% niacin. Ultimate stress, which is force per unit area, was decreased by .3% Al and .05% Al plus 1.5% niacin (P less than .05). Niacin had no significant effect on bone mineral content. In Experiment 3, .3% Al decreased P, Ca, Mg, and Zn content of the tibiae (P less than .05). These findings indicate that feeding high levels of supplemental niacin results in decreased bone strength in chicks with no change in mineral content of the tibiae. Aluminum fed at levels of .3% of the diet causes a decrease in bone strength with concomitant changes in bone mineral content.