PRODUCTIVITY OF RAINBOW TROUT DEPENDING ON PROTEIN LEVELS IN PRODUCTIVE FEED

The article considers the efficiency of using complete feeds with different levels of protein in rearing commercial rainbow trout. The purpose of the experiment was to establish the effect of different protein levels in nutrition of two-year old trout on its productivity. For this purpose, five experimental groups were formed by the method of analogues. During the equalizing period, the experimental fish consumed feed of the control group. In the main period, the protein level in trout feed ranged from 44 to 52 % per 1 kg. As a result of the studies it was established that the increase of protein content in compound feed from 48 to 52 % leads to an increase in the weight of commercial fish by 13.0 % (p < 0.001), an increase in its growth intensity – by 7.4-16.7 %, while the reduction of protein in feed to 44 % leads to a reliable (p < 0.05) reduction in trout weight by 9.4 %, and a decrease in its growth intensity – by 6.5-12.1 %. It is proved that different levels of experimental trout’s protein nutrition have a highly reliable (p < 0.001) effect on the growth of marketable fish - the share of this factor’s influence is 89.8 %. Analysis of the feed costs, proves that using combined feed with 52 % protein for feeding two-year old trout, leads to a decrease in feed costs per 1 kg of weight gain by 5.1 %, whereas reducing this index to 44% causes increase of feed costs by 6.4 % per a unit of product, compared to feeding fish with production feed having the protein content of 48 %. At this, the preservation of experimental fish was high enough and made 94.3 to 96.2 %. In rearing trouts according to the criteria of maximum productivity, it is recommended to feed commercial trout with production combined feeds with the protein level of 52 %, whereas, in production according to the economic optimization criteria, this index should make 48 %