Previous exposure to dietary phytase reduces the endogenous energy losses from precision-fed chickens.

1. A precision feeding experiment was conducted with broiler chickens, which were previously fed on diets with or without phytase, to study the effects of previous exposure to dietary phytase supplementation on the excretions of endogenous energy, nitrogen, amino acids and minerals. 2. Female Ross 308 broiler chickens, which had previously received one of 4 experimental diets (low P maize/soy diets (control, D), D + 250 international units of phytase per kg diet (FTU), D + 500 FTU and D + 2500 FTU) were used in the study. All birds were starved and then given 50 ml of glucose solution at 44 d of age. The birds were allocated to individual metabolism cages in a randomised block design with 8 replicates of each of the 4 dietary treatments. 3. Chickens which had been previously fed on diets supplemented with phytase excreted 32% less energy and 28% less dry matter per kg metabolic body weight (W(075)) from endogenous sources, compared to birds fed the unsupplemented diet. 4. Birds previously given phytase supplemented diets excreted 60% less sodium than those given the control diet, but there was no effect on all other minerals investigated. There was no effect of diet on the excretion of endogenous N, sialic acid or amino acids. 5. The results showed that the effects of feeding chickens on diets with supplementary phytase may continue for a few days after the diets are withdrawn. This suggests that previous exposure to phytase may alter the nutritive value of follow-on diets, which may be a commercially important effect.