Susceptibility of two commercial single comb White Leghorn strains to calcium-induced urolithiasis: efficacy of dietary supplementation with DL-methionine and ammonium sulphate.

1. Susceptibility to calcium-induced urolithiasis was assessed in pullets of two commercial SCWL strains (A and B) reared together from 5 to 18 weeks of age on diets containing 10 g/kg calcium (normal calcium: NC) or 35 g/kg calcium (high calcium: HC). 2. Kidney damage was not observed in pullets reared on NC diets. For pullets fed on HC diets, strain A developed significantly greater kidney asymmetry, a higher incidence of gross kidney damage and a higher incidence of uroliths than strain B. 3. Supplementing the HC diet with 6 g/kg DL-methionine significantly reduced the incidence of calcium-induced gross kidney damage and urolith formation in both strains. Ammonium sulphate (5.3 g/kg) was significantly more effective than DL-methionine in reducing calcium-induced kidney damage. 4. Neither DL-methionine nor ammonium sulphate caused a measurable metabolic acidosis. Neither supplement consistently affected water consumption or manure moisture.