Archiva Zootechnica vol. 9, 2006 95 Phytase as a factor of improving broilers growth performance and environmental protection Jovanka Levic, Olivera Djuragic, Slavica Sredanovic Faculty of Technology, Feed Technology Department Novi Sad, Serbia & Montenegro ABSTRACT The aim of this work was to find out the possibility how to increase the availability of phytic phosphorous and, at the same time, decrease phosphorous excretion through faeces into the environment when using phytase in broilers fed diets based on corn, soybean and sunflower meal with reduced level of phosphorous added. In all feeding periods of broilers, the group fed trial mash II with reduced phosphorous level and phytase had higher body weight by 2.0- 18.7% during the trial, better feed conversion by 7.0% at the end of the trial and by 17.7% at the end of the second week, mortality lower by 16.7% and decrease of phosphorous level in faeces by 5.4 to 22.4 during the trial. The positive production results obtained in broiler feeding have shown that phytase added affected the increase of availability of trial mashes based on corn, soybean and sunflower meal with reduced level of phosphorous added. Keywords: broilers, feed utilization, phytase, phosphorous excretion, weight gain INTRODUCTION Phosphorous is an important feed ingredient and is supplied to animals in needed amounts through raw material and added phosphates. Vegetable feeds contain significant amount of this mineral, however, 50-80% of phosphorous is bound in phytates, that cannot be broken down by endogenous enzymes in poultry (Anon, 1997). As a consequence, phosphorous from vegetable sources is poorly digested and cannot meet nutritional requirements of poultry regardless the fact that cereals, leguminous and oilseed plants contain 1-5% phytate. In order to become available to broiler chicks, phosphorous from vegetable sources must be hydrolyzed, with phytase as a catalyst, to inositols and inorganic phosphates which are readily absorbed in digestive tract (Annison, 1993). Through supplementation of microbial phytase to the monogastric animals about 50% of phytic phosphorous may be released (Anon, 1997). Results of numerous experiments have shown that degradation of phytate by phytase has two-fold positive effect – release of phosphorous and release of minerals,