Productivity and physiological-biochemical parameters of carp body after the supplementation of their feed with milk thistle

The paper presents the results of studies of the effect of the milk thistle Silybum marianum feed supplement with biologically active properties on productive and some physiological and biochemical parameters of carp body. Three experiments were conducted during 2013–2014, each of which had a control group, which was fed with a basic diet, and three experimental groups, which received milk thistle seeds at concentrations of 1 %, 5 % and 10 % in the diet, respectively. The object of the first experiment were age-1 carp, which were kept in aquariums and which received orally the ground seeds of the milk thistle in the composition of a starch paste (Control 1, Experiments 1–3). The object of the second and third experiments were age-1+ fish, which were fed with a feed supplemented with the milk thistle during the growing season (Control 2, Experiments 4–6 and Control 3, Experiments 7–9). The aim of the work was to determine the efficiency of the use of the milk thistle in carp feeding. At the same time, identical optimal conditions for keeping fish during testing were provided. The study was conducted according to conventional methods. The relative fat content in fish muscles was determined by the extraction method, total protein by the Kjeldahl method, and dry matter by evaporation. The hemoglobin content was determined by hemoglobin cyanide method, the number of erythrocytes was counted in the Goryaev's chamber. The obtained results were processed statistically, the difference between the groups was evaluated by the Student's test. After feeding age-1 carp with a feed supplemented with 5 % ground seeds of the milk thistle, the hemoglobin contents increased in all experimental groups compared to the control and the number of erythrocytes. The relative fat content in the muscles of the experimental fish increased by 29.4 %, 15 % and 8.1 %, respectively, while the protein content did not change. Analysis of the results of studies on age-1+ fish in 2013 showed an improvement in physiological parameters in all experimental groups compared to the control: hemoglobin content by 25.5 (P < 0.05), 12.5 and 3.6 %; erythrocyte count – by 7.7, 8.5 and 2.7 %. The relative protein content in the muscles of carp fed with a feed supplemented with 1 and 5% milk thistle increased by 6.5 % (P < 0.05) and 8.1 % (P < 0.05), fat – by 5.9 and 13.1 %, respectively. When feeding with 10 % milk thistle, these values reduced by 4.5 and 10.8 % compared to the control. Fish productivity in ponds, when fish was fed with 1 and 5 % milk thistle was higher than in control by 26.1 and 28.2 %, the average weight of age-1+ by 21.6 and 23.8 %, while feed costs decreased by 1.4 times. A repeated similar experiment in 2014 showed that the hemoglobin content of fish fed with 1 % milk thistle increased by 9 %, protein by 7.5 % (P < 0.001), dry matter by 6.9 % (P < 0.01). Fish culture parameters improved when supplementing fish feeds with 1 and 5 % milk thistle: fish productivity in ponds increased by 44.9 and 31.3 %, the average fish weight increased by 33.8 and 20.1 %, the feed ratio was lower by 40.0 and 33.3 % compared to the control group.