THE EFFECT OF CITRIC ACID AND MICROBIAL PHYTASE ON AMINO ACID DIGESTIBILITY IN BROILER CHICKENS
Résumé
1. Two experiments with growing chickens were carried out to study the effects of the inclusion of a microbial phytase (Natuphos® 5000) and citric acid (CA) in maize-soybean based diets on the performance and apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA). In both experiments the diets were formulated to contain the same amounts of energy and protein. 2. In the first experiment, data were analyzed as a 2 x 2 factorial arrangement with two levels of AP for 1 d of age to 3 wk (3.5 and 2.2 g/kg) and for 3 to 6 wk (2.7 and 1.4 g/kg), and two levels of commercial phytase (0 and 500 FTU/kg) in each period. The AID of CP and dispensable and indispensable AA were not modified by the level of AP in the diet. Addition of phytase improved the AID of CP and dispensable and indispensable AA only at low AP levels. 3. In the second experiment, data were analyzed as a 3 x 2 factorial arrangement with three concentrations of citric acid (0, 20 and 50 g/kg) and two levels of commercial phytase (0 and 750 FTU/kg). Diets were formulated with deficient levels in AP (2.5 g/kg). Performance was not affected by commercial phytase addition. The addition of CA reduced the weight gain but did not modify the feed intake and gain:feed. In general, the AID of CP and dispensable and indispensable AA were not affected by CA addition. Commercial phytase increased the apparent ileal digestibility of crude protein but had not effect on AID of dispensable and indispensable AA. 4. In conclusion, the results of these experiments demonstrated that microbial phytase enhanced AA digestibility in maize-soy-based diet only at very low AP levels, and that CA had not affect on the AID of CP and dispensable and indispensable AA. No synergism between CA and microbial phytase could be detected.
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