Urinary acidification previously was shown to be an effective treatment for
calcium-induced
urolithiasis in domestic fowl, but diuresis caused by the acidifying agent (
ammonium chloride) was an undesirable side effect. Because supplemental dietary
methionine reportedly acidifies mammalian urine, an experiment was conducted to evaluate the efficacy of the free
acid form of
methionine hydroxy analog (MHA) as an acidifying agent for treating avian
urolithiasis. From 5 to 17 wk of age, immature Single Comb White Leghorns were fed diets containing normal
calcium (1%) or high
calcium (3.5%). Diets were supplemented with 0, 0.3 or 0.6% MHA. Relative to birds fed the normal
calcium diets, birds fed the high
calcium diet without added MHA were in a state of metabolic
alkalosis and excreted more alkaline urine containing high levels of
calcium. Birds fed the high
calcium diet without MHA also had significantly higher kidney asymmetry ratios, a higher incidence of gross kidney damage, and a higher incidence of urolith formation when compared with birds fed normal
calcium diets. When compared with the high
calcium diet without MHA, the high
calcium diet supplemented with 0.6% MHA significantly acidified the urine without causing detectable
metabolic acidosis, significantly reduced kidney asymmetry and gross kidney damage, and reduced the incidence of urolith formation without increasing water consumption or urine flow. These data demonstrate that MHA effectively prevents
calcium-induced kidney damage in domestic fowl without causing undesirable side effects. MHA did increase both fractional and absolute
calcium excretion during
calcium loading.