Synergistic effects of dietary cholesterol and taurine on growth performance and cholesterol metabolism in juvenile turbot (Scophthalmus maximus L.) fed high plant protein diets

The study was conducted to investigate the effects of cholesterol, taurine and combination of dietary cholesterol and taurine on growth performance and cholesterol metabolism in juvenile turbot (Scophthalmus maximus L.) fed high plant protein diets. A basal diet (control) with 14.5% fish meal and 50% crude protein was formulated. The other three isonitrogenous and isolipidic experimental diets were prepared with the supplementation of 1.0% cholesterol, 1.0% taurine and a combination of 1.0% cholesterol and 1.0% taurine to the basal diet, which were named as C-1.0%, T-1.0% and TC, respectively. The results showed that the weight gain rate in fish fed C-1.0%, T-1.0% and TC diets was significantly higher than that in fish fed the control diet. Especially, fish fed TC diet showed the highest growth performance in data among dietary treatments. The plasma total cholesterol, free cholesterol and low-density lipoprotein cholesterol levels were significantly lower in fish fed TC diet compared to those in fish fed C-1.0% diet (P < 0.05). Fish fed C-1.0% diet showed significantly higher activity of cholesterol 7α hydroxylase (CYP7A1) than the control diet (P < 0.05), and activity of CYP7A1 in fish fed T-1.0% diet was the highest among dietary treatments. The PCR product of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMG-CoAr) amplified by the degenerate primers was 331 bp. The HMG-CoAr mRNA levels were significantly lower in fish fed TC diet compared to that in fish fed C-1.0% diet (P < 0.05). These results suggested that the combination of 1.0% cholesterol and 1.0% taurine is helpful for juvenile turbot fed high plant protein diets to obtain significantly better growth without negative effects.

► Turbot fed diet with 1% cholesterol and 1% taurine showed the highest growth.
► The plasma cholesterol-lowering effect was observed in fish fed taurine supplementation diet.
► Dietary taurine caused different expression of HMG-CoAr mRNA.
► Both cholesterol and taurine are helpful to obtain better growth without negative effects.