Influences of dietary lipid and temperature on growth, fat deposition and lipoprotein lipase expression in darkbarbel catfish (Pelteobagrus vachellii)

Darkbarbel catfish (Pelteobagrus vachellii) is an important freshwater fish in China. Water temperature greatly influences the absorption and utilization of dietary lipid by fish. Response values (including growth, hepatic fat deposition, and gene expression) for darkbarbel catfish mediated by two factors (water temperature 20-34 °C; dietary lipid level 2-17%) were the focus of this study. The relationship between the two factors and the response values was evaluated by the response surface method using the central composite design. The experiment was conducted under laboratory conditions and lasted for seven weeks. A total of 975 experimental fish (average weight 11.75 ± 0.17 g) were selected and placed in 39 plastic tanks. The results showed that the linear effects of lipid level on feed conversion rate (FCR), hepatopancreas somatic index (HSI), hepatic triglycerides (TG), cholesterol (TC), and lipoprotein lipase (LPL) gene expression were significant (P < 0.05). The linear effects of water temperature on specific growth rate (SGR), HSI, TC level, and LPL mRNA expression were significant (P < 0.05). The quadratic effects of water temperature and lipid level on SGR and FCR were significant (P < 0.05). Low water temperature and low lipid diets significantly inhibited growth, increased HSI, and reduced hepatic TG and TC levels, and LPL mRNA expression. The adjusted R2 values for the SGR, FCR, HSI, TC, TG, and LPL mRNA regression models were 0.77, 0.85, 0.62, 0.73, 0.85, and 0.91, respectively. The optimal combination of water temperature and dietary lipid level was 27.5 °C and 9.2%, at which the greatest growth and FCR were 2.13%.d−1 and 1.31 respectively, with desirability of 0.904. These results indicated that water temperature may mediate the requirement and utilization of dietary lipid, and intervene in hepatic fat deposition. The results of this study can be used to help optimize the culture conditions of darkbarbel catfish.