Abstract:
An 8-week growth trial was conducted to determine the effects of dietary protein levels on growth, body composition and health status of paddlefish (
Polyodon spathula). Five experimental diets were formulated to contain 35.44%, 37.20%, 39.19%, 42.05% and 45.30% dietary crude protein (CP) with 5% lipid levels, respectively. At the end of the experiment, fish fed 35.44% to 42.05% CP diet resulted in significantly higher weight gain rate and specific growth rate, and both decreased at 45.30% CP level. The protein efficiency rate did not change significantly when the dietary CP increased from 35.44% to 42.05%; however, it significantly decreased when protein level reached 45.30%. The body composition of the experimental fish did not change significantly with the increase of dietary protein levels. The protein apparent digestibility coefficients (ADC) of 39.19% CP level is significant higher compared with other groups, which was contrary to lipid ADC and dry matter ADC. Liver lipase activity of
P. Spathula peaked with the fish fed 42.05% CP level. The highest superoxide dismutase activity of the
P. spathula was observed in the 37.20% treatment, and the activity of catalase significantly increased when CP level reached 39.19% compared to the 35.44% treatment. Based on second-order polynomial regression analysis of weight gain rate and specific growth rate, the recommended dietary protein level for
P. spathula diet is 40%-41%.