The effects of hydrolyzed canola meal protein on growth, body composition and expression of growth genes and appetite of beluga fish (Huso huso)

The aim of this study was to investigate the effects of increasing the hydrolyzed protein of canola meal on growth factors, expression of GH, IGF and ghrelin genes and beluga (Huso huso) juvenile body composition. For this purpose, 840 juveniles beluga with an average weight of 30±5grams were distributed in 12 tanks, 70 in each tank. Each tank has a capacity of 2400 liters. Canola meal hydrolyzed protein was fed with different levels of 0 (control), 300 (treatment 1), 400 (treatment 2) and 500 (treatment 3) mg of protein for 8 weeks. At the end of the breeding period, bioassay was performed to evaluate growth factors and biopsy of brain, stomach and liver tissue to evaluate the expression of these genes. The results showed that with increasing the amount of hydrolyzed protein in canola meal in the diet, body weight gain, specific growth rate and protein efficiency increased and the highest value was in treatment 3 (500 mg) which was a significant difference with other groups(P <0.05). Also, the expression of all 3 genes showed an increasing trend that the difference between treatments and control was significant (P <0.05). The highest expression was observed for all three genes in the 500 mg treatment. The lowest amount of protein was in treatment 3, but there was no significant difference in the amount of protein, fat, ash and moisture between the control and other treatments (P> 0.05). In general, hydrolyzed canola protein can positively affect growth performance in beluga fish.