Kazakhstan starter compound feed for African catfish (Clarias gariepinus): formulation, quality characterization, and efficiency in aquaculture

Currently, the breeding of Clarias gariepinus is a promising area of aquaculture in Kazakhstan. African catfish is a fast-growing, rapid-maturating, hardy and disease-resistant species. In the Almaty region, breeding of African catfish is most relevant due to a large number of geothermal sources which can significantly reduce the cost of fish growing. However, fish farmers use imported starter feeds. Here, we submit research data on approbation of the Kazakhstan starter feed for larvae of C. gariepinus . A technology has been developed for the production of mixed feed based on grain raw materials using the extrusion method (LLP Kazakh Research Institute of Processing and Food Industry, Almaty). The experimental feed is a 50.7 % protein, 11.53 % fat, and 17.31 MJ/kg of metabolic energy. Experimental rearing (LLP Kapshagai spawning and rearing farm-1973 and a peasant farm MG, Almaty region, 2020). Trout feed Aller Futura EX 0.5-0.2 mm (Aller Aqua, Denmark), the most common feed for growing C. gariepinus in Kazakhstan was a control. The experiment was arranged in duplicate, two pools for the control and two pools for the experiment. The fish was fed by hand 12 times during daylight hours in equal portions. The growth rate of juvenile C. gariepinus was assessed by control catches at 10-day intervals and a final catch. Volumetric method was used for the C. gari-epinus larvae counting. Fish-breeding and biological parameters of the juvenile C. gariepinus were obtained by expert assessments. Absolute bodyweight gain, the feed conversion ratio and the survival rate of juveniles were 1313.7 g, 0.93 vs. 0.82 in the control and 75 % vs. 77 % in control, respectively, (the LLP KSRF-1973) and 1588.5 g, 0.93 vs. 0.88, 72 % vs. 74 % (the MG farm). Thus, the developed starter feed is not inferior to the standard in terms of nutritional value, it is physiologically complete, balanced in the main nutrients, including essential amino acids, and easier to digest. The compound feed is a well-flowing crumbs from dark to light brown in color, has high water resistance, swells quite well (swelling time is 40 minutes), and retains its shape during swelling. It was well eaten by fish. The granules practically did not break, did not crumble, and were of a size convenient for fish. Compound feed complies with sanitary standards in terms of microbiological indicators and can be stored for 10 months. The cost of the developed starter compound feed is 3 times lower than that of the imported one, and the cost of African catfish juveniles was less by 0.39-0.73 tenge per individual while fish breeding and biological parameters remained quite high. That is, in terms of the combination of price-quality, the Kazakhstani starter mixed fodder corresponded to the used standard sample. The results obtained allow us to conclude that the proposed feed is competitive, and its use will improve the efficiency of rearing juveniles of African catfish and the capabilities of fish farms in Kazakhstan