Organic food for aquaculture and pet animals: Phytase supplementation as an emerging strategy to reduce phosphorus losses.
University of Trás-os-Montes and Alto Douro (UTAD); Sparos Lda.
Facing the increasing costs and sustainability challenges of the compound feed industry, the raw materials of plant origin are increasingly being used in fish feed for aquaculture and for pet animals. However, a significant fraction (40-80%) of the phosphorus present in these plant ingredients is in the form of phytic acid. This form of phosphorus is not digestible by the monogastric animals since they do not have the enzyme needed for its hydrolysis, the phytase. Since phosphorus is an essential micronutrient for fish, the strategy currently used to meet the phosphorus needs of animals implies the use of food supplements with sources of inorganic phosphorus, namely calcium phosphates. Current food formulas thus imply additional costs associated with inorganic phosphorus supplementation (about 5%) and, above all, the release into the aquatic environment of a significant fraction of phytic phosphorus with the consequent environmental pollution burden. In the case of pet animals (dogs) the calcium: phosphorus ratio (Ca: P) of the current feeds is of the order of 1.6. However, there are studies that associate beneficial effects (e.g. joint condition and bone growth) to a reduction of this ratio to values close to 1. Advances in biotechnology allowed the development and marketing of phytases as enzymatic supplements of diets. In fish and pet animals, published research shows that phytase supplementation is a promising strategy to increase phosphorus digestibility by significantly reducing the pollutant impact of aquaculture fish feeds on the aquatic environment and reducing the Ca: P ratio of dog food. However, industrial use of phytase is not yet a common practice given the lack of quantitative knowledge related to optimal conditions of its use and the technological limitations to the implementation of the industrial application process. The FITAQUA project aimed to generate scientific knowledge and practical data on the biological and economic efficacy of a phytase supplementation strategy that would allow the development, on an industrial scale, of a new range of ecological feed in fish (trout and sea bream) and also the optimization of the Ca: P ratio in pet food (dogs).