LIQUID METHIONINE HYDROXY ANALOG (FREE ACID) AND DL-METHIONINE ATTENUATE CALCIUM-INDUCED KIDNEY DAMAGE IN DOMESTIC-FOWL

To evaluate the possibility that kidney damage may be induced by the c ommercial practice of feeding high-Ca (HCa) prelayer rations, and to e valuate the protective efficacy of supplementing HCa diets with liquid methionine hydroxy analog free acid or DL-methionine, 12-wk-old femal e Single Comb White Leghorn pullets were fed one of the following corn -soybean meal-based diets until they reached 22 wk of age: normal-Ca ( NC, 1% Ca); HCa (HC, 3.5% Ca); HCa supplemented with.34 or.68% liquid methionine hydroxy analog free acid (HC3A or HC6A); or HCa supplemente d with .3 or .6% DL-methionine (HC3DL or HC6DL). The unsupplemented HC diet caused a significant reduction in kidney mass and a significant increase in the incidence of gross kidney damage and urolithiasis in p ullets necropsied at 22 wk of age. Calcium-induced kidney damage was a ttenuated in a dose-response fashion by supplementing the HC diet with liquid methionine hydroxy analog and DL-methionine. None of the diets caused a significant metabolic acidosis. Plasma uric acid concentrati ons were not predictive of the extent of Ca-induced kidney damage. Ana lyses of glomerular size distributions indicated that subclinical or ' 'hidden'' kidney damage may not progressively develop into urolithiasi s as hens mature. When compared with hens reared on the NC diet, reari ng hens on the HC, HC3A, HC3DL, HC6A, or HC6DL diets did not consisten tly affect hen-day egg production, egg mass, eggshell mass, percentage eggshell, or bone mineralization.