ASSESSMENT OF THE PHYSIOLOGICAL STATE OF RAINBOW TROUT WHEN INTRODUCING FLOUR FROM RAW RIVER CRAYFISH IN TO THE DIET

Abstract. The article presents the results of scientific research on the growth, development, survival, fatness and condition of the internal organs of rainbow trout with the introduction of raw crayfish flour into the diet.
Key words: feeding, compound feed, crayfish meal, growth dynamics, physiological state of fish.

Rational feeding of fish is a leading factor of the cultivation of both planting material and commercial fish in fish farms.

In the conditions of modern aquaculture, there is an urgent need to develop and widely use full-fledged artificial feed mixtures containing a complex complex of nutrients and biologically active substances necessary for normal growth and vital activity of the body [2; 3; 4; 5; 8].

Currently, a large number of additives are being developed and used in fish feeding, which contain essential amino acids, minerals, and vitamins aimed at increasing growth, improving the physiological state under stress, and increasing survival. Scientists are faced with another important problem - to combine in such additives not only their useful growth-stimulating, immunomodulating qualities, but also their rather low cost.

One of these additives is crustacean processing products.

Flour from crustaceans is not only a source of protein, but also supplier karatoid pigments in the fish organism. The role of carotenoids for normal physiological processes is indisputable. A large number of karatoid pigments were found in the tissues and organs of hydrobionts [1, 9].

The function of carotenoids in the body is not limited to conversion to vitamin A. Scientists have found out the immunostimulating role of carotenoids. Carotenoids increase the cytostatic activity of killer cells, slow down tumor growth and accelerate wound healing. Their importance in increasing the body's resistance to toxic substances under hypoxic conditions is also noted [6]. In addition, karotinoidy capable of saving action of vitamins and enzymes [7]. Experimentally, the possibility of obtaining red pigmentation of salmon muscle tissue by including astaxanthin in the diet was shown.

Thus, the aim of the work was to study the growth processes and physiological state of rainbow trout when using flour from raw river crayfish in diets.

Scientific research was carried out in the I. P. Surkov fisheries complex in Engels, Saratov region, in a closed water supply system (CWSS) and at the basis of the Department of «Feeding, zoohygiena and aquaculture», Saratov State Agrarian University named after N.I. Vavilov. The research scheme is presented in Table 1.

The control group's feed mix consisted of wheat flour, sunflower cake, fish meal (with a protein content of 32.4 %), vegetable fat, fish oil, molasses, and premix (bran).

The compound feed contained a high percentage of protein, fat and carbohydrates obtained as a result of adding more than 62.5% of animal components to the recipe, as well as microelements necessary for fish to develop fully. In the feed of the experimental group was introduced flour from raw river crayfish, pre-dried, in an amount of 20% due to fish meal and sunflower cake.

By the method of analogs, 150 individuals of rainbow trout with an average weight of 1230 g were selected and divided into 50 pieces in three polypropylene pools with a volume of 5 m3 each, water exchange 2.57 times per hour. The experiment was conducted for 10 weeks.

The water in the fish-breeding tanks of the CWSS in terms of hydrochemical composition met the requirements of Industrial Standard 15.312.87. - "Nature protection. Hydrosphere. Water for fish farms. General requirements and norms" for growing rainbow trout.

Water was supplied to the pools from the adder, the water exchange in one pool was 12850 l/h. Indicators of values of dissolved oxygen values, the hydrogen index (pH), met the stated requirements. During the studies, the average water temperature was 13.8 °C.

Fish feeding was implemented manually. The size of pellets (grits) of mixed feed corresponded to the mass of rainbow trout. The calculation of feeding rates was carried out depending on the mass of fish and water temperature.

The growth rate was studied based on the results of control weighings performed once every 14 days.

The introduction of flour from raw river crayfish into the rainbow trout diet had a positive effect on the growth and survival of commercial trout (Table 2).

The experimental group was ahead of the control group in absolute growth by 73 g. The growth rate was also higher in the experimental group by 7.2 %. The largest average daily increase was observed in the experimental group and exceeded the control by 1 %.

One of the indicators that directly characterize the growth and development of fish is linear size and fatness, which can be used to judge the physiological state of fish, and what effect does the flour from raw river crayfish have on the fish's metabolic processes (Table 3).

During the period of the experiment, a higher fatness coefficient was noted in the experimental group, it reached a maximum average value of 2.32, which indicates a more intensive fat accumulation of rainbow trout under the influence of raw river crayfish flour.

When studying the effect of raw river crayfish flour on the physiological state of the body of rainbow trout, it is necessary to assess the state of internal organs. At the end of the experiment, a control slaughter of fish was carried out. For control slaughter, 3 individuals were selected with an average weight of 1906.0 and 1972.7 g. when examining internal organs, no pathologies were found. The heart is resilient, rich red color, sufficient blood filling of blood vessels. The gastrointestinal tract had a natural color, without hemorrhages and pathologies in development. The stomach is well defined and has a siphon-like shape, the intestines are a kind of short tube. The liver is quite voluminous, compact, shiny, resilient, without hemorrhages. The results of determining the average mass of internal organs are shown in Table 4.

Analysis of the data obtained did not reveal changes in internal organs depending on the introduction of a feed additive to the diet of rainbow trout. Flour from raw river crayfish in the compound feed did not lead to a significant change in the mass of organs.

It was found that the introduction of raw river crayfish flour into the diet of rainbow trout has a positive effect on the chemical composition of fish muscle tissue (Table 5).

Analyzing the data on the chemical composition of muscle tissue, it can be noted that the protein and fat content in the experimental group exceeds the values of the control group by 4.7 and 2.7%.

There were no significant differences in the content of inorganic substances, such as calcium and phosphorus, in the experimental groups.

It was noted that when using raw river crayfish flour in feeding rainbow trout, the muscle tissue of the experimental individuals had a more intense pink color, compared to the control, which indicates the assimilation of astaxanthin from crustacean processing products. According to the results of the experiment, it is obvious that this natural caratinoid had a fruitful effect on the metabolism, thereby contributing to the increase in fish productivity.

Thus, it can be concluded that the use of compound feed with the addition of 20% raw river crayfish flour in feeding rainbow trout has a positive effect on the growth rate, development and physiological state of fish.

List of references

1. Bahareva, A. A. Using chitin-chitosan to improve the quality of feed / A. A. Bahareva, U. N. Grozescu // Abstracts of reports I international scientific student conference of the Association of universities of the Caspian States, Astrakhan, 1998, pp. 58-60.

2. Vasiliev, A. A. Influence of humic acids of the feed additive "Reasil Humic Vet" on the growth and survival of early young muksun / A. A. Vasiliev, I. V. Poddubnaya, I. A. Kitaev, Yu. a. Stuklova // Proceedings of the IV National scientific and practical conference State and ways of aquaculture development in the Russian Federation– Saratov, LLC "Amirit", - 2019, - P. 56-60.

3. Vasiliev, A. A. efficiency of using an immunostimulating drug in feeding sturgeon fish when growing in a closed water supply system / A. A. Vasiliev, I. V. Poddubnaya, A. S. Semykina // Agrarian scientific journal. – 2018. – no. 9. – Pp. 28-30. Pp. 47-50.

4. Vilutis O. E. Chemical composition of muscle tissue of rainbow trout when introducing flour from river crayfish into the diet. / O. E. Vilutis, D. S. Vasiliev, A.V. Vilutis // International scientific and practical conference "Modern ways to improve the productive qualities of farm animals, birds and fish", dedicated to the 90th anniversary of the zootechnical faculty OF the Saratov state agrarian UNIVERSITY named after N. I. Vavilov. - Saratov, 2020 - P. 167-170.

5. Poddubnaya, I. V. Influence of biologically active additive "Abiopeptide" with organic iodine on the growth, development and commercial qualities of carp when growing in cages / I. V. Poddubnaya, A. A. Vasiliev // Scientific practical and production journal of the Federal Agency for fisheries "fisheries". – 2017. - No. 1. - P. 77 – 82.

6. Karnaukhov, V. N. On the functions of carotenoids in animal cells / V. N. Karnaukhov // Biophysics of living cells. Pushchino, 1971. - Pp. 68-83.

7. Ponomarev, S. V. Physiological basis for creating a full-fledged combined feed, with considering the stages of development of the body of salmon and sturgeon / S. V. Ponomarev, E. A. Gamygin, A. N. Kanidyev // Bulletin of the Astrakhan state technical University, 2002 – P. 203.

8. Guseva, Y.A. Growth Rate And Commercial Qualities Of The Muscle Tissue Of Rainbow Trout With Hydrolysate Of Soya Protein Used For Feeding / Y.A. Guseva, A. A Vasiliev, I.V. Poddubnaya // Journal of Pharmaceutical Sciences and Research Volume 10 (8), 2018. - Pages: 1956-1958.

9. Gzeczuga, B. Comparative studies of the occurrences and xanthophylls in reproductive cells of water animals / B. Gzeczuga // Folia Histochem. et cytochem. - 1973. -v. 11. - P. 275-286.