Effects of Dietary Arachidonic Acid Levels on Growth Performance, Whole-Body Proximate Composition, Digestive Enzyme Activities and Gut Morphology of Juvenile Golden Pompano Trachinotus

Abstract

The effects of dietary arachidonic acid (ARA) levels on growth performance, whole-body proximate composition, digestive enzyme activities, and gut morphology were studied in juvenile golden pompano Trachinotus ovatus. Six diets were formulated with six levels of ARA. Fish were fed twice daily to apparent satiation for 56 days (8 weeks). Weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), feed conversion ratio (FCR), and viscerosomatic index (VSI) were significantly affected by dietary ARA levels (P < 0.05). WG, SGR and PER increased with the increasing levels of ARA (P < 0.05), and thereafter slightly declined (P > 0.05); they were highest in fish fed the diet with 0.51% ARA and the lowest in fish fed the diet containing 0.15% ARA. Linear regression analysis on SGR indicated that the recommended optimum dietary ARA level for optimal growth of juvenile golden pompano was 0.53%. Whole body protein significantly declined when dietary ARA levels increased from 0.15% to 0.88% (P < 0.05), and were lowest in fish fed the diet containing 0.88% ARA. The whole body lipid content showed an opposite trend compared with whole body protein. Pepsin activities showed no significant differences among treatments (P > 0.05), while lipase activities of fish were significantly influenced by dietary ARA levels (P < 0.05). The number of goblet cells and intestinal villus length increased with increasing levels of ARA from 0.15% to 0.51% (P < 0.05), and decreased thereafter. Goblet cells of fish fed diets with 0.36%, 0.51%, 0.71% ARA were higher than in the other groups (P < 0.05).