Effects of dietary visceral protein hydrolysate of rainbow trout on growth performance, carcass composition, digestibility and antioxidant enzyme in juvenile Oncorhynchus mykiss

The purpose of this study was to investigate the effects of dietary visceral protein hydrolysate (VPH) of rainbow trout on performance of juvenile Oncorhynchus mykiss . The antioxidant property of VPH was 85% ± 1.6%. Four diets were prepared including VPH free as the control and three diets with 5, 10 and 20 g/kg of VPH inclusions. Juvenile rainbow trouts ( n  = 252, 9.74 ± 0.22 g) were randomly distributed to experimental tanks. Final results showed the maximum amounts of weight gain and SGR and the lowest FCR value in fish fed with 10 g/kg VPH ( p  < .05). The highest carcass protein and fat contents were observed in 10 g/kg VPH treatment and the control diet, respectively ( p  < .05). The largest fat and dry matter digestibility were recorded in fish fed by 5 g/kg VPH ( p  < .05), while the control and 10 g/kg VPH diets showed the highest levels of protein digestibility ( p  < .05). Dietary inclusion of VPH improved SOD enzyme activity ( p  < .05). The results indicate that a diet containing 10 g/kg of VPH inclusion can improve growth performance and some other examined factors in juvenile O. mykiss .