Influence of Different Dietary Soybean Lecithin/Fish Oil Ratios on Growth Performance and Histology of Juvenile Grouper Epinephelus coioides

Key words: 
• Epinephelus coioides juvenile /
• soybean lecithin /
• fish oil /
• growth /
• survival

Abstract: Four formulated microdiets supplemented with different soybean lecithin/fish oil （SL/FO） ratios: Diet1（0%/22% ）, Diet2（5%/14% ）, Diet 3 （10%/8%） and Diet 4 （15%/7% ） were fed to 40-day-old juvenile grouper Epinephelus coioides after hatching. Each experimental diet was distributed in triplicate tanks. The survival, feed efficiency,growth performance and intestine histology of the grouper juveniles were monitored after a 40-day growth trial. Results showed that different dietary SL/FO ratios significantly affected the growth and survival （P≤0. 05） of the grouper juveniles. The juveniles fed Diet 3 （10% /8%, SL/FO） and Diet 4 （15/7,SL/FO） gave significantly higher weight gain （WG） than those fed Diet 1 （0% /22%, SL/FO）. The juveniles fed Diet1 （0%/22%, SL/FO） had obviously lower whole body lipid content than those fed other diets （P≤0. 05）, but had significantly higher whole body protein content than those fed other diets （P ＜ 0. 05）. For all treatments no significant differences were observed in feed efficiency （FE）, hepatosomatic index （HSI）, viscerosomatic index （VSI） and condition factor （CF）, specific growth rate （SGR）, feed intake （FI）, protein efficiency ratio （PER）, and final body weight （FBW）. Increase in dietary soybean lecithin/fish oil （SL/FO） ratio reduced lipid droplets in intestine enterocytes of grouper juvenile. It is concluded that the grouper juvenile microdiets should have a high dietary soybean lecithin/fish oil ratio （15%/7% ）.