Effects of dietary eucommia ulmoides leaf extract (ELE) 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

Abstract

Abstract A 30-day 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 0g Kg−1 (the control), 5g Kg−1 (0.5%), 10g Kg−1 (1.0%), and 20g Kg−1 (2.0%) of ELE, respectively. Results showed that the best growth performance was found in larvae fed the diet with 1.0% ELE. Furthermore, ELE supplementation significantly increased the npy expression at 1.0% dosage, while increased ghrelin in larvae at 0.5% dosages. The activity of leucine aminopeptidase in larvae fed the diet with 1.0% ELE was significantly higher than the control, while alkaline phosphatase was significantly up-regulated in larvae fed the diet with 2.0% ELE. A clear increase in total antioxidant capacity in larvae fed the diet with 1.0% ELE was observed, whereas catalase activity was significantly higher in 1.0% and 2.0% ELE supplementation compared to the control. Larvae fed the diet with 1.0% 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-1β and il-6 were remarkably down-regulated by supplementation of 0.5-1.0% ELE. This study demonstrated that the supplementation of 1.0% 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.