Mineral digestibility and environmental issues. Efficacy and interactions of phytases

Means to reduce excretion of both P and trace elements such as Cu and Zn in pig manure include better agreement between supply and requirement and development of comprehensive strategies to improve biological availability of these elements, e.g. by using organic rather than inorganic mineral sources. However, comparison of results between studies is often confounded by the response criteria used for measuring the efficiency of different mineral sources. Low digestibility of P in feed ingredients remains the main problem, although it can be partly alleviated by supplementing pig diets with microbial phytases, and by using highly digestible mineral phosphates. More recently, research has focused on ways to manipulate pig's gut environment by adding organic acids or prebiotic substances (e.g. beta-glucans) to the diet in order to improve P digestibility. Eventually, cross reactions of feed enzymes such as exogenous microbial phytases and non-starch polysaccharide (NSP) degrading enzymes with microbial fermentation processes through changes in intestinal pH may affect both enzyme activity and efficiency. (C) 2010 Elsevier B.V. All rights reserved.