EFFECT OF LOW- AND HIGH PHYTASE BARLEY ON PHOSPHORUS RETENTION AND BONE MINERAL COMPOSITION IN BROILERS.

The effects of low-phosphorus diets with two levels of phytase were examined in broiler chickens using eight replicates per treatment. The diets contained 40 % of spring barley with either 201 or 305 phytase activity units per kg. Chromic oxide was included in the diets as an indigestible marker. Excreta were collected during four consecutive three-day balance periods from the 12th to the 23rd day of age. No difference was observed for body weight gain between the dietary treatment groups but feed conversion ratio was better (P < 0.05) when higher phytase barley was used. In spite of the higher dietary level of phosphorus, the coefficient of apparent P retention was higher (P < 0.01) in higher than in lower phytase group. The retention of phosphorus increased (P < 0.01) with time of feeding in both low-phosphorus dietary groups. Differences between treatments in concentration of calcium, phosphorus, magnesium, sodium and potassium in defatted tibia were not significant (P > 0.05). [ABSTRACT FROM AUTHOR]