Abstract
The conducted experiments showed that fish grown using feed containing probiotics with different mechanisms of action — enzymatic and antioxidant — showed gains and fatness coefficient exceeding the control values by more than 7 % and 5–13 %, respectively, with a decrease in feed costs of 6.7 %. Analysis of weight distribution among the studied fish groups revealed that in the experiments the percentage of individuals with higher body weight was higher by 9.65 and 14.75 %, amounting to 58.16 and 63.26 %, respectively. In the open field test, the juvenile sterlet from the 2nd experimental group recorded orientation activity, which was lower than in the 1st experimental and control groups by 3.79 % and 1.61 %, respectively, amounting to 34.8 units/min. However, the background motor activity in this group was the highest — 36.78 units/min. In the 1st experimental and control groups, on the contrary, a decrease in this indicator was observed. It was found that in individuals of the experimental groups, an increase in the reaction to the primary stimulus (vibroacoustic stimulus) was observed, followed by a sharp decrease in activity when exposed to the second stimulus. This indicates the manifestation of a defensive reaction (freezing), characteristic of sturgeon fish. In the control group, the reaction to the primary stimulus also increases, but to a lesser extent, and then remains almost unchanged. After exposure to the third stimulus, the activity of individuals of the control group does not return to the original level, exceeding it by 13.35%. At the same time, in individuals of the experimental groups, the activity approaches the background level. The ratio of orienting activity to background activity (activation level) in fish of the second experimental group was 13.9% lower than in the first experimental and control groups. This indicates that fish from the first experimental and control groups exhibit higher activity when entering a new environment. At the same time, individuals from the second experimental group demonstrate more restrained motor behavior. The reactivity indices in the experimental groups under the influence of low-frequency sound are 1,46–10,54 % higher, under short-term light stimulus and constant light exposure they are lower by 12.09–27.47 % and by 9.72–14.88 % in the 2nd and 1st groups, respectively, compared to the control group. Fish fed with feeds with experimental probiotic additives demonstrated increased resistance to high temperature and salinity. The highest heat resistance and salt tolerance were shown by fish from the first experimental group. Probiotic preparations with targeted action stimulate growth and stabilize the physiological state of fish in extreme conditions.
Published Version
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