Effects of dietary protein concentration on growth and anti-oxidant capacity of coho salmon Oncorhynchus kisutch (Walbaum, 1792) alevins

A 12-week feeding trial was conducted to examine the effects of dietary protein concentrations on growth, whole-body chemical composition, and hepatic anti-oxidant enzyme activities of coho salmon Oncorhynchus kisutch (Walbaum, 1792) alevins. Five experimental diets were formulated with graded protein levels of 36.5%, 42.0%, 48.0%, 54.5%, and 60.0%, respectively, with each fed to triplicate groups of fish (0.36 +/- 0.01 g). Stocked as groups of 50 individuals per tank (water volume of 240 L), fish were fed four times daily with the method of overfeeding (15-20% body weight). After the feeding trial, the specific growth rate (SGR) in groups fed diets with 48.0%, 54.5%, and 60.0% protein was significantly higher than that in the 36.5% protein group (P < .05). The feed conversion ratio (FCR) in 48.0%, 54.5%, and 60.0% dietary protein groups was significantly lower than that in the 36.5% protein group (P < .05). No significant differences were observed for hepatosomatic index (HSI), intestosomatic index (ISI), condition factor (CF), and whole-body composition, except the crude protein content, which increased significantly with the increment of dietary protein level up to 48.0% (P < .05) and then leveled off (P > .05). Dietary protein up to 48.0% significantly increased the activities of total superoxide dismutase (T-SOD) and catalase (CAT) and significantly decreased the malondialdehyde (MDA) contents in the liver (P < .05). The second-order polynomial regression analyses based on SGR indicated that the optimal protein requirement in diets of coho salmon alevins was 53.6%, which was concurrent with a protein to energy ratio of 25.8 g protein MJ(-1).

Automated summary

A 12-week feeding trial was conducted to examine the effects of dietary protein concentrations on the growth, whole-body chemical composition, and hepatic anti-oxidant enzyme activities of coho salmon alevins. The results showed that diets with higher protein concentrations led to higher growth rate and lower feed conversion ratio. Additionally, the higher protein diet also increased hepatic anti-oxidant enzyme activities.