Compared with the control, supplementation of FA remarkably increased activities of alkaline phosphatase and leucine aminopeptidase in the brush border membrane of intestine. Diets supplemented with 0.02%–0.04% FA significantly increased the activity of trypsin in the intestinal segment, while 0.01%–0.02% FA significantly increased the activity of trypsin in the pancreatic segment. Moreover, supplementation of FA significantly increased mRNA expression of intestinal epithelial proliferation and barrier genes ( pcna, zo-1 and zo-2). The supplementation of 0.01%–0.02% FA significantly increased the muscular thickness of intestine.

Larvae fed the diet with 0.01% FA had significantly higher villus height than the control. Based on the specific growth rate, the optimal supplementation was 0.0135% FA. Meanwhile, supplemental FA significantly increased final body weight and specific growth rate. Results showed that the supplementation of 0.04% FA significantly improved survival rate of large yellow croaker larvae. Four isonitrogenous and isolipids diets containing 0.00%, 0.01%, 0.02% and 0.04% FA were formulated, respectively.

2Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, ChinaĪ 30-day feeding trial was designed to evaluate the effect of supplemental fulvic acid (FA) on survival, growth performance, digestive ability and immunity of large yellow croaker ( Larimichthys crocea) larvae (initial body weight 11.33 ± 0.57 mg).

1Key Laboratory of Aquaculture Nutrition and Feed (Ministry of Agriculture and Rural Affairs), Key Laboratory of Mariculture (Ministry of Education), Ocean University of China, Qingdao, China.

Chenxiang Zhang 1 Yongtao Liu 1 Chuanwei Yao 1 Jianmin Zhang 1 Yuntao Wang 1 Jiahui Liu 1 Yucong Hong 1 Kangsen Mai 1,2 Qinghui Ai 1,2*

State of survival growth kit