The effect of citric acid on the calcium and phosphorus requirements of chicks fed corn-soybean meal diets

Data previously reported from our laboratory indicated that supplementation of a corn-soybean meal diet with citric acid improves P utilization in chicks. The four experiments reported herein were conducted to further evaluate the effects of citric acid on Ca and P utilization for chicks fed a corn-soybean meal diet. Diets in all experiments were fed to chicks from 8 to 21 or 22 d of age. The first experiment evaluated the effect of 6% citric acid on the Ca requirement of chicks. A Ca-deficient basal diet [23% CP, 0.54% Ca, 0.45% available P (AP)] containing 0 to 0.7% supplemental Ca in 0.1% increments was fed with or without 6% citric acid. The results indicated that citric acid did not significantly affect the Ca requirement. A second experiment evaluated different levels of citric acid (0, 2, 4, or 6%) on P utilization, and results indicated that 4 and 6% citric acid produced the largest responses in growth and tibia ash. Experiments 3 and 4 were then conducted to determine whether 4 or 6% citric acid would reduce the level of supplemental P required. Dietary treatments were a P-deficient basal diet (23% CP, 1.0 or 1.3% Ca, 0.20% AP) supplemented with 0 to 0.25% inorganic P with or without 4 or 6% citric acid. When diets contained citric acid, weight gain and tibia ash were maximized at lower AP levels than when diets contained no citric acid. The results of this study indicate that citric acid increases P utilization in corn-soybean meal diets and reduces the AP requirement by approximately 0.10% of the diet.