Effects of soy lecithin on growth, stress resistance, digestive enzymes activity and antioxidant capacity in yellowfin seabream (Acanthopagrus latus) larvae

Abstract

Phospholipid (PL) is an essential nutrient that has vital effects on growth, stress resistance and early development in marine fish larvae. In this regard, a 30-day feeding experiment was conducted in order to examine the effects of live prey enrichment with graded levels of soy lecithin (SL) on some physiological responses of Acanthopagrus latus larvae. Four experimental emulsions levels of SL were used to enrich Rotifer and Artemia including very low (2%, N), low (4%, L), medium (8%, M) and high (12%, H). Newly hatched larvae were distributed into twelve 250-L cylindrical tanks with an initial density of 15000 larvae in each tank that was supplied with natural seawater (23 ± 1 ºC; 40.0 ± 1.0 g L-1). The green water method was used for larviculture and live prey was given to larvae two times daily. Larvae fed 4% SL containing live prey significantly had higher wet weight gain than other treatments. Air exposure and osmotic activity tests were also performed to detect larval resistance to stress. Larvae fed 8% and 12% SL containing live prey had higher survival compared to the other two groups. The accumulation of arachidonic ARA and docosahexaenoic acids was increased in the larval whole body fed high SL-supplemented live foods. Alkaline phosphatase and aminopeptidase N activities in the guts brush border membrane of larvae in M and H groups were higher than other treatments. The trypsin and chymotrypsin activities in the N group were lower than in other treatments. The highest and lowest amylase activities were in the H and N groups, respectively. The activity of catalase and glutathione reductase in the whole body of the M group was higher than the N treatment and other groups had intermediate values. Total antioxidant capacity in the whole body of larvae in the N group was lower than in the other treatments. In summary, moderate levels of SL (4–8%) are suggested for the enrichment of live foods in A. latus.