Effects of Dietary Phosphorus Levels on Growth Performance, Plasma Biochemical Parameters and Relative Gene Expression of Lipogenesis of Bighead Carp, Aristichthys nobilis

Abstract

An 8-week feeding trial was conducted to investigate the effects of dietary phosphorus levels on growth performance, plasma biochemical parameters, and lipogenesis gene expression of bighead carp. The results showed that weight gain (WG) and specific growth rate (SGR) increased with increasing dietary phosphorus levels up to 1.12%, and after that decreased. Feed conversion ratio (FCR) showed a converse trend compared with WG. Whole body protein and lipid contents significantly increased and decreased with increasing dietary phosphorus levels, respectively (P<0.05), whereas moisture and ash contents were not significantly affected by the dietary phosphorus levels (P>0.05). The highest values of the hepatosomatic index (HSI), total protein, and albumin contents were observed with 1.12% dietary phosphorus supplementation (P<0.05). Glucose levels increased with dietary phosphorus up to the level 1.32% phosphorus supplementation, and then decreased. Serum total cholesterol, total triglyceride, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphates activity were not significantly affected by dietary phosphorus levels (P>0.05). Excess phosphorus levels (1.32% and 1.59%) significantly down-regulated the relative gene expression levels of sterol regulatory element binding protein (SREBP) -1 and fatty acid synthase (FAS) (P<0.05). Based on WG and FCR, the optimal dietary phosphorus level should be 1.16%, using quadratic regression analysis.