Dietary choline requirements of adult GIFT tilapia (<I>Oreochromis ni-loticus</I>)

Abstract

A10-week feeding trial was conducted to study the effect of dietary choline chloride supplementation on the growth performance, lipid metabolism, feed utilization, body composition, serum biochemical indices, liver lipid content, and muscle and liver choline content of adult GIFT tilapia(Oreochromis niloticus). The basal diet contained 27.60% crude protein and 6.45% crude lipid. The basal diet was supplemented with choline chloride(0,300, 600, 1200, 1 800, and 2 400 mg choline per kg food) to formulate six semi-purified diets containing choline of 97.80(control group), 375.04, 565.74, 974.27, 1409.81, and 1 824.35 mg choline per kg food. Each diet was randomly fed to three replicates of GIFT tilapia with an initial average weight of(220.00±8.34) g in 18 pond cages(1.0 m×1.0 m×1.5 m). Compared with the control group, the addition of choline to the diet significantly improved weight gain rate, specific growth rate, and feed utilization(P0.05). The liver fat content decreased significantly(P0.05) in all groups compared with the control. In addition, the liver choline and muscle fat content of all groups increased significantly(P0.05). With increasing dietary choline levels, serum triglyceride and cholesterol content increased in the groups with significantly higher choline chloride than that of the control group(P0.05),the liver triglyceride and cholesterol content decreased significantly(P0.05). Serum aspartate aminotransferase(ALT), alanine aminotransferase(AST), and alkaline phosphatase(ALP) also decreased significantly(P0.05) with increasing dietary choline content. The choline requirement of adult GIFT tilapia was 506.43 mg choline per kg food based on the specific growth rate; however, it was 981.38 mg choline per kg food based on liver choline concentration. Our results suggest that choline chloride supplementation could improve tilapia growth performance, feed efficiency, reduce liver fat content, and promote lipid degradation.