Effect of Gray strain infectious bronchitis virus and high dietary calcium on renal function of Single Comb White Leghorn pullets at 6, 10, and 18 weeks of age.

Experiments were designed to evaluate the effects of Gray strain infectious bronchitis virus (IBV) and high dietary calcium (Ca), alone and in combination, on renal function in pullets. Eight hundred female Single Comb White Leghorn chicks were raised on starter ration. Five hundred chicks were inoculated intravenously with Gray strain IBV at 4 wk of age; the remaining chicks were not exposed to IBV. At 6 wk of age, IBV-inoculated and uninoculated chicks were randomly divided into two diet treatment groups. Half the chicks were fed commercial grower ration (approximately 1.0% Ca, .6% available P) and half were fed commercial layer ration (approximately 3.25% Ca, .5% available P). Birds remained on their respective diets until 18 wk of age. Kidney function studies were conducted on anesthetized birds at 6 wk of age prior to initiation of the diet treatments, at 10 wk of age, and at 18 wk of age. The layer ration increased Ca excretion, decreased inorganic phosphate excretion, and decreased urine hydrogen ion concentration in 10-wk-old pullets in comparison with the grower ration. These diet effects on kidney function were attenuated when the pullets reached 18 wk of age. The layer ration also caused an 11.5% incidence of urolithiasis, and significantly increased kidney asymmetry in 18-wk-old pullets relative to the effects of the grower ration. Gray strain IBV exposure significantly increased kidney asymmetry in 18-wk-old pullets, but had no gross effect on kidney function clearly related to the etiology of urolithiasis. Gray strain IBV did not enhance the incidence of urolithiasis in any of the age groups.