Effects of dietary choline on liver lipid composition, liver histology and plasma biochemistry of juvenile yellowtail kingfish (Seriola lalandi)

Choline plays a crucial role in lipid metabolism for fish, and its deficiency in aquafeed has been linked to compromised health and growth performance. A 56-d experiment was conducted to examine the effects of dietary choline on lipid composition, histology, and plasma biochemistry of yellowtail kingfish (Seriola lalandi; YTK; 156 g initial body weight). The dietary choline content ranged from 0.59 to 6.22 g/kg diet. Three grams of 2-amino-2-methyl-1-propanol (AMP)/kg was added to diets, except for a control diet, to limit de novo choline synthesis. The results showed that the liver lipid content of YTK was similar among diets containing AMP and dominated by free fatty acids (FFA). In contrast, fish fed the control diet had significantly elevated liver triacylglycerol (TAG). Generally, the saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) content of liver lipid in fish fed diets containing AMP was not influenced by choline content. The SFA and MUFA of liver lipid in fish fed the control diet was similar to other diets except for a decrease in PUFA. The linear relationship between lipid digestibility and plasma cholesterol was significant, otherwise most parameters were unaffected. When AMP is present, higher dietary choline reduced the severity of some hepatic lesions. This study demonstrated that choline-deficiency affects some plasma and liver histology parameters in juvenile YTK which might be useful fish health indicators. Importantly, this study elucidated potential reasons for lower growth in choline-deficient YTK and increased the knowledge on choline metabolism in the fish.