AFFECTING THE PHOSPHORUS RETENTION IN FISH BREEDING BY USING SPECIAL CEREAL VARIETIES

The aim of the study was to monitor the phosphorus digestibility of the feed used in the fish breeding. Phosphorus excreted by fish into the aquatic environment may be one of the potential sources of pollution of the aquatic environment by biogenic elements. The efforts to influence the amount of phosphorus leaving the fish breeding are divided into several directions, where the main reason is different physiology of fish digestion. In particular the pond breeding of cyprinids is becoming an increasingly addressed issue. The possibility of influencing phosphorus digestibility by the use of phytate enzymes in the carp breeding is almost impossible in practise; therefore it is important to focus on one of the other methods. Breeding of new varieties of cereals with reduced content of indigestible form of phosphorus for cyprinids is one of the potentially successful ways how to eliminate the amount of phosphorus leaving the fish breeding. 60 pc of common carp fry and four experimental diets were selected for this study. The first part of the test was focused on the feeding of wheat and the second one on the feeding of barley. Control varieties and varieties with a reduced content of phytate were used in both parts. Phosphorus digestibility of the feeds was determined through the indicator method where the crude fibre served as an indicator. In the case of wheat, there was determined a statistically highly significant increase (P<0.01) of phosphorus digestibility (by 11.21%) when feeding a low -phytate variety. In the case of barley, there was determined a statistically significant increase (P<0.05) of phosphorus digestibility when feeding a low-phytate variety. Feeding cereals varieties with a reduced content of phytate has a significant effect on reducing phosphorus loading of the aquatic environment.