DIETARY CALCIUM AND PHOSPHORUS EFFECTS ON BROILER PERFORMANCE AND THEINCIDENCE OF SUDDEN-DEATH SYNDROME MORTALITY

Three experiments were conducted with broiler chickens to determine th e effect of dietary Ca and P on growth, feed conversion, bone ash, and the incidence of sudden death syndrome (SDS) mortality. Trial 1 teste d three rations [100% NRC (1984) Ca and P; 140% NRC Ca and P; and 140% NRC Ca and P to 3 wk and 100% NRC from 4 to 7 wk] in Ross x Ross male s to 7 wk of age. Dietary Ca and P had no effect on body weight, feed conversion, bone ash, or leg problems, but SDS mortality was significa ntly higher in the two groups fed 140% Ca and P for 3 or 7 wk (2.83 an d 3.33% SDS mortality, respectively). Trial 2 tested three diets (85% NRC Ca and P, 100% NRC Ca and P, and 140% NRC Ca and P) in mixed sex A rbor Acres x Peterson chicks to 7 wk of age. The lower level of Ca and P (85% NRC) significantly improved feed conversion (7 wk) and decreas ed bone ash only at 3 wk and serum Ca (7 wk). There was no effect of d iet on SDS in this trial. Trial 3 tested two diets (85% NRC Ca and P o r 100% NRC Ca and 85% NRC P) in Ross x Ross males to 9 wk of age. Six- week body weight was significantly reduced in the 85% NRC Ca and P die t but body weight was equal by 9 wk of age. No effects were observed f or feed conversion, leg disorders, bone ash, or serum Ca. The SDS mort ality was significantly increased in the chicks fed the 100% NRC Ca an d 85% P diet compared to the 85% NRC Ca treatment. The results of thes e trials indicate that even slight deviations in dietary Ca and P beyo nd the NRC recommendations can create a metabolic imbalance in certain strains of broilers (Ross x Ross), which possibly increases susceptib ility to SDS mortality.