The effects of different fishmeal level diets with or without phytase supplementation on growth performance, body composition, digestibility, immunological and biochemical parameters of juvenile hybrid sturgeon ( Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂)

A 12‐week growth trial was conducted to evaluate the effect of low fishmeal and phytase replacing inorganic phosphorus on juvenile hybrid sturgeon (Acipenser baeri Brandt ♀ × A. schrenckii Brandt ♂). Four experimental diets were designed as FM100p, FM100, FM250p and FM250, which represented 10% and 25% fishmeal with or without phytase, respectively. The results showed that although growth parameters had no significant difference in all treatments, low fishmeal obviously decreased the culture cost of hybrid sturgeon. Lipid content of body composition was obviously increased in low fishmeal treatments (p < .05). The interaction of low fishmeal and phytase significantly enhanced apparent digestibility coefficients of crude protein (p < .05). Two‐way ANOVA analysis showed that input and output of phosphorus were significantly affected by fishmeal level, phytase and interaction of both factors (p < .05). For the immunological and hepatic function parameters, fishmeal level and phytase had significant effects on the activities of lysozyme, myeloperoxidase, malondialdehyde, alanine aminotransferase, lactate dehydrogenase and alkaline phosphatase (p < .05). The present study potentially justifies that a diet containing 10% fishmeal can be used for hybrid sturgeon. Moreover, replacement of monocalcium phosphate by phytase not only has no adverse effect on the growth of hybrid sturgeon, but also reduces phosphorus emission and protects aquaculture environment.