Effect of dietary acid or aluminum on growth and growth-related hormones in young chickens.

The effect of two concentrations of dietary acid (sulfuric acid) or aluminum (aluminum sulfate) on growth and growth-related hormones was examined in a heavy (broiler) strain of chicken between 4 and 18 days old. Growth (body weight, average daily gain, and tibial length) in chicks receiving either dietary acid or aluminum-containing diets were compared to chicks fed a control diet and to chicks fed diets containing sodium sulfate. Despite the reduced growth in acid-fed chicks, there were no changes in the plasma concentrations of growth hormone, insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding proteins (IGF-BP). However, in chicks receiving the high aluminum diet where growth was markedly depressed (by 57%), plasma concentrations of IGF-I were depressed, while those of the 36-kDa IGF-BP were elevated. The effects of acid and aluminum on growth were mediated at least partially by reductions in feed intake. Pair feeding depressed growth and tended to decrease plasma concentrations of IGF-I. Some differences were observed between acid or aluminum groups and their respective pair-fed controls. For the groups receiving the low-aluminum and both the high- and low-acid diets, values were increased compared to corresponding pair-fed controls for average daily gain, the level of the 36-kDa IGF-BP, and skeletal growth. On the other hand, high aluminum had a toxic effect in addition to reducing feed intake, with skeletal growth being reduced more in chicks receiving the aluminum diet than in the pair-fed controls.