EFFECT OF DIETARY ACID OR ALUMINUM ON GROWTH AND GROWTH-RELATED HORMONES IN MALLARD DUCKLINGS (ANAS-PLATYRHYNCHOS)

Acid precipitation may exert negative effects on growth and survival o f birds whether by the acid itself (H+ ions) or by aluminum consumptio n due to increased solubility at low pHs. The effects of aluminum or a cid on growth-related hormones were compared in mallard ducklings: gro wth hormone, insulin-like growth factor, and insulin-like growth facto r binding proteins (IGFBPs). Birds received two levels of acid: sulfur ic acid (0.056 or 0.277 moles sulfate per kg) or aluminum sulfate (0.1 or 0.5% aluminum; 0.056 or 0.277 moles sulfate per kg). Two sodium su lfate (0.056 or 0.277 moles sulfate per kg) treatment groups were adde d as additional controls, and a group was given control diet ad libitu m. Ducklings were fed the test diets for 15 days. In addition, there w ere pair-fed controls to the acid and aluminum diets. Growth as indica ted by body weight, average daily gain, and tibiotarsus length was red uced (p < 0.05) in ducklings on the high aluminum diet compared to tho se receiving the control diet ad libitum. Moreover, ducklings on the h igh aluminum diet had a reduced (p < 0.05) growth (average daily gain) compared to the pair-fed controls. No effects of the aluminum diets o n plasma concentrations of growth hormone, insulin-like growth factor- I, or IGFBPs were observed (IGFBPs being observed in the duck for the first time). Diets containing acid had no effects on growth or circula ting hormone levels. It is concluded that aluminum influences growth i n ducks directly and by reducing feed consumption.