Impact of mannanoligo saccharides on performance traits of rainbow trout

The effect of mannanoligo saccharides (MOS) as a food additive, applied at a concentration of 0.2% (O-I group of fish) and 0.3% (O-II group of fish) on morphometric characteristics and primary production of the Californian trout was investigated. The experiment was conducted on 450 fish divided into three groups with 150 individuals in each group, and lasted 40 days. The analysis of obtained results established the beneficial effect of the applied additives on morphometric parameters of the growth rate of fish, their final mass and final linear dimensions, and their growth, but no statistically significant differences (p> 0,05) were established. The highest body weight and body length of studied groups was achieved by trout of O-II group (118.49 g, 19.59 cm), followed by trout of O-I group (118.04 g, 19.58 cm) and the lowest K-group fish (115.94 g, 19.56 cm). Adding MOS in the feed mixture for trout had a beneficial effect (p> 0.05) in the exercise of lower feed conversion (FC) and better values of main production indicators: condition factor (FC), protein efficiency ratio (PER), the specific rate growth rate (SGR) and production index (PI) compared to the K group of fish that were fed diets without added mannanoligo saccharides. The best results were achieved by O- II fish group, and expressed in relative terms in comparison to the K group of fish: better feed conversion by 5.61%, a better utilization of protein feed value by 5.94%, a higher value of condition factor by 1.73 %, the specific growth rate by 2.26% and a better value of production index by 8.27%.