Citric acid improves phytate phosphorus utilization in crossbred and commercial broiler chicks

Previous research in our laboratory has shown that citric acid (CA) improves phytate P utilization in New Hampshire x Columbian (NHC) crossbred chicks fed a P-deficient corn-soybean meal diet. The current study was conducted to determine if CA is also effective in commercial broiler chicks (Ross x Ross). In 3 experiments, 4 replicate groups of 5 male NHC chicks and male commercial chicks were fed corn-soybean meal diets varying in CA and nonphytate P (NPP) from 8 to 22 d of age. In experiment 1, a 2 x 2 x 2 factorial treatment arrangement was used to evaluate the effect of 2 levels of CA (0 and 3%) and NPP (0.13 and 0.28%) in NHC chicks and commercial chicks. The commercial chicks, but not the NHC chicks, fed the 0.13% NPP diet had to be removed from the experiment after 3 to 5 d due to very poor growth and severe leg problems. Chick weight gain and tibia ash were significantly increased (P < 0.05) by CA in both types of chicks. In experiment 2, the same 2 x 2 x 2 factorial treatment arrangement was again used except that the NPP levels were 0.18 and 0.28%. Tibia ash was increased significantly (P < 0.05) with the addition of CA in both breeds of chicks; response was greater at 0.18% NPP than at 0.28% NPP. In experiment 3, graded levels of CA (0, 1, 2, 3, and 4%) were evaluated in commercial chicks fed diets containing 0.18% NPP. Tibia ash increased linearly (P < 0.05) as CA increased from 0 to 4%. The average increase in bone ash resulting from 3% CA supplementation in experiments 2 and 3 was 41%. These results indicate that CA markedly improved phytate P utilization in NHC and Ross x Ross commercial broiler chicks.