No abstract

A 30-day feeding experiment was conducted to investigate effects of dietary allicin on survival, growth, antioxidant capacity, innate immunity and expression of inflammatory and appetite related genes in large yellow croaker larvae. Four iso-nitrogenous (53% crude protein) and iso-lipidic (19% crude lipid) diets were formulated via supplementing graded levels of allicin (0.0 (the control), 0.005, 0.01, and 0.02% dry diet, respectively). Results showed that, among dietary treatments, larvae fed the diet with 0.005% allicin had the highest survival rate (SR) ( P < 0.05), while larvae fed the diet with 0.01% allicin had the highest specific growth rate (SGR) ( P < 0.05). Activities of α-amylase in both pancreatic (PS) and intestine segments (IS) of larvae fed the diet with 0.01% allicin were significantly lower than that in the control ( P < 0.05). On the other hand, the supplementation of 0.01% allicin in diets significantly increased activities of alkaline phosphatase (AKP) and leucine aminopeptidase (LAP) in the intestinal brush border membrane (BBM) of larvae than the control ( P < 0.05), indicating the promoting roles of allicin on fish larval intestinal development. Moreover, compared to the control, both the nitric oxide (NO) content and the activity of nitric oxide synthase (NOS) were significantly up-regulated in larvae fed the diet with 0.005% allicin, and catalase (CAT) were significantly upregulated in larvae fed the diet with 0.02% allicin ( P < 0.05). Transcriptional levels of pro-inflammatory genes including cyclooxygenase-2 ( cox-2 ), interleukin-1β ( il-1 β) and interleukin-6 ( il-6 ) significantly decreased with increasing allicin, compared to the control. The expression of appetite genes including npy , ghrelin and leptin significantly increased with the prolonged fasting period, and dietary allicin supplementation significantly increased the transcriptional level of neuropeptide Y ( npy ) at 0.01%, while increased the transcriptional level of leptin in larvae at 0.02% dosages ( P < 0.05). These results showed that the supplementation of 0.005% – 0.01% allicin in diets could improve the survival and growth of large yellow croaker larvae probably by promoting intestinal development, alleviating inflammation and enhancing appetite.

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.