ALUMINUM AND ACID EFFECTS ON CALCIUM AND PHOSPHORUS-METABOLISM IN YOUNG GROWING CHICKENS (GALLUS-GALLUS-DOMESTICUS) AND MALLARD DUCKS (ANAS-PLATYRHYNCHOS)

Acidification is associated with increased mortality, reduced growth, and bone abnormalities in birds. Associated with acid deposition is an increase in aluminum availability due to solubilization from soil and other sources. (Conversely, experimental diets containing aluminum su lfate have much reduced pHs.) The present studies compare the effects of two levels of dietary acid (sulfuric acid) (0.122 and 0.56 mol H+ p er kg feed; 0.056 and 0.277 mol sulfate per kg feed) and dietary alumi num (aluminum sulfate at 0.1 and 0.5%; sulfate at 0.056 and 0.277 mol sulfate per kg feed) on bone growth, mineralization, and phosphorous/c alcium homeostasis in growing birds (chickens and mallard ducks). Grow th was reduced by the high acid (chicken) and aluminum (ducks and chic kens) diets, A reduction in bone mineralization was observed in birds receiving aluminum-containing diets [low aluminum diet: decreased tibi a ash, calcium, and phosphorus (chickens); high aluminum diet: decreas ed tibia dry weight, % of ash and mg; ash, calcium (chickens, ducks as % of ash), and phosphorus (chickens mg/duck, % of ash)]. Moreover, pl asma concentrations of inorganic phosphate were reduced in chicks on t he high aluminum diet. Then were also marked decreases in bone growth and mineralization [tibia weight, ash (mg), calcium (mg), phosphorus ( mg)] and plasma concentrations of 1,25-dihydroxy vitamin D-3 in chicks on the high acid diet compared to those on a control diet. These chan ges were probably due to reduced feed intake; changes in bone indices being of a greater or similar magnitude in pairfed control. Then was l ittle change in bone indices, growth rate or feed consumption in duckl ings receiving either the low or high acid diets. It is concluded that aluminum directly adversely affected bone mineralization whereas acid effects are mediated in part by changes in feed consumption.