Phosphatidylcholine in diets of juvenile Nile tilapia in a biofloc technology system: Effects on performance, energy metabolism and the antioxidant system

Abstract

Intensification of aquaculture production systems requires more nutritionally complete diets to maximize productive performance, metabolic processes and overall fish health. In previous studies, dietary supplementation with choline (both choline chloride and phosphatidylcholine) improved productive performance of tilapia cultivated in clear water. Nevertheless, choline has not been tested in a biofloc technology system (BFT), a culture system inhabited by diverse microorganisms that serve as food sources for fish. The objective of this study was to determine whether supplementation with phosphatidylcholine, also known as vegetable choline (0, 400, 800 and 1200 mg/kg of feed), in diets of Nile tilapia (Oreochromis niloticus) in a biofloc system would stimulate energy metabolism and the serum antioxidant system, with consequent improvements in productive performance. Juvenile Nile tilapia (≅ 8 g) were tested over 40 days. During this period, zootechnical performance was evaluated. Blood, gills and liver were collected at the end of the experiment for biochemical and energetic analyses. There were no significant differences between the treatments with respect to parameters of zootechnical performance (body weight, biomass gain, feed conversion, specific growth rate and hepatosomatic index) (P > 0.05). Alanine aminotransferase levels were significantly lower in fish fed 800 mg/kg of phosphatidylcholine than in control; total protein levels increased as a result of increased globulin levels. Activities of creatine kinase enzyme (800 and 1200 mg choline/kg treatments) and pyruvate kinase (1200 mg choline/kg) were significantly higher in choline-treated fish than in controls. Supplementation with the three doses of choline reduced hepatic lipid peroxidation and stimulated glutathione S-transferase activity. By contrast, the activities of other antioxidant enzymes (catalase, glutathione peroxidase and superoxide dismutase) were altered in the livers of fish that consumed the highest doses of phosphatidylcholine. We conclude that, in a biofloc system, supplementation with phosphatidylcholine had no effect on the zootechnical performance of tilapia; however, it stimulated energy metabolism and contributed to activation of hepatic GST and lower levels of lipid peroxidation.