Effects of dietary eucommia ulmoides leaf extract on growth performance, expression of feeding-related genes, activities of digestive enzymes, antioxidant capacity, immunity and cytokines expression of large yellow croaker (Larimichthys crocea) larvae

A 30-d feeding trial was conducted to investigate effects of dietary eucommia ulmoides leaf extract (ELE) on growth performance, activities of digestive enzymes, antioxidant capacity, immunity, expression of inflammatory factors and feeding-related genes of large yellow croaker larvae. Five micro-diets were formulated with supplementation of 0 g kg(-1) (the control), 5 g kg(-1) (0 center dot 5 %), 10 g kg(-1) (1 center dot 0 %) and 20 g kg(-1) (2 center dot 0 %) of ELE, respectively. Results showed that the best growth performance was found in larvae fed the diet with 1 center dot 0 % ELE. Furthermore, ELE supplementation significantly increased the npy expression at 1 center dot 0 % dosage, while increased ghrelin in larvae at 0 center dot 5 % dosages. The activity of leucine aminopeptidase in larvae fed the diet with 1 center dot 0 % ELE was significantly higher than the control, while alkaline phosphatase was significantly upregulated in larvae fed the diet with 2 center dot 0 % ELE. A clear increase in total antioxidant capacity in larvae fed the diet with 1 center dot 0 % ELE was observed, whereas catalase activity was significantly higher in 1 center dot 0 % and 2 center dot 0 % ELE supplementation compared with the control. Larvae fed the diet with 1 center dot 0 % ELE had a significantly higher activities of lysozyme, total nitric oxide synthase and nitric oxide content than the control. Moreover, transcriptional levels of cox-2, il-1 beta and il-6 were remarkably downregulated by the supplementation of 0 center dot 5-1 center dot 0 % ELE. This study demonstrated that the supplementation of 1 center dot 0 % ELE in diet could increase the growth performance of large yellow croaker larvae probably by promoting expression of feeding-related genes, enhancing antioxidant capacity and immunity and inhibiting expression of inflammatory factors.