Reducing environmental pollution using animal feed enzymes

The global livestock population is estimated to be close to 4 billion animals, and to produce around 500 million tons of manure annually (Baidoo, 2003). This is expected to increase in the future with the projected greater demand for meat for human consumption. The problem of manure disposal is exacerbated by the concentration of animal production in increasingly large units, to obtain economies of scale and keep up with the demand for cheap food. The primary environmentalfactors are manure volume, manure nitrogen and phosphorus contents, methane production and odour (Jongbloed and Lenis, 1998). Legislation in many regions now restricts the amount of manure that can be applied per hectare, to prevent environmental pollution (Centner, 2001; Pellini and Morris, 2001). There are a number of strategies the animal production industry can take to reduce environmental impact. These include taking steps to improve the efficiency of conversion of feed into edible products, reduce feed wastage and formulate diets that more closely satisfy animal requirements for specific nutrients. At present 50-80% of the nitrogen and phosphorus fed to animals are not utilized but are excreted via manure and urine to the environment (Baidoo, 2003). Biotechnology could play a very important role in reducing the environmental impact of animal production. Examples include the development of animals more efficient at converting nutrients into edible products, and of higher quality, more digestible feedstuffs. Biotechnology can also be used to produce a range of feed additives that can improve the efficiency of animal production, including for example recombinant somatrophin, amino acids and enzymes. This paper summarizes a series of four experiments looking at the effects of microbial xylanase or phytase supplementation on excretion in swine and poultry. This summary indicates that the inclusion of these enzymes in animal feeds can reduce manure volume by up to 14%, and nitrogen and phosphorus outputs by up to 13% and 70%, respectively.