Evaluation of Dietary Essential Amino Acid Supplementation on Growth, Digestive Capacity, Antioxidant, and Intestine Health of the Juvenile Redclaw Crayfish, Cherax quadricarinatus

Abstract

The present study was an 8-week feeding trial investigating the effects of lysine and threonine supplementation in vegetable-based diets on growth, antioxidative capacity, and gut microbiota of juvenile redclaw crayfish, Cherax quadricarinatus (initial weight 11.52 ± 0.23 g). The lysine and threonine were supplemented to formulate five isonitrogenous (37%) and isolipidic (9%) diets containing 0% (control), 0.2% lysine (L0.2), 0.2% threonine (T0.2), 0.4% lysine (L0.4), and 0.4% threonine (T0.4), respectively. Compared to the control, weight gain rate (WGR) and specific growth rate (SGR) of C. quadricarinatus significantly increased with increasing dietary lysine and threonine supplementation from 0.2% to 0.4% ($P<0.05$). Hepatopancreas trypsin activity significantly increased with increasing levels of lysine and threonine in diets ($P<0.05$). However, the pepsin, lipase, and amylase activities were not affected by dietary levels of lysine and threonine ($P>0.05$). Compared with the control, crayfish in T0.4 and L0.4 showed significantly higher glutathione peroxidase (GPx) activity ($P<0.05$), lower alanine aminotransferase (ALT) activity, and lower malondialdehyde (MDA) content ($P<0.05$). Supplementation with 0.4% lysine significantly changed the composition of the gut microbiota ($P<0.05$), which showed a significantly increased relative abundance of Proteobacteria and decreased Firmicutes, Actinomycetes, and Pontomyces ($P<0.05$). The PICRUSt analysis demonstrated that the abundance of the metabolism and cellular processes pathways in the L0.4 group were markedly decreased compared with the control ($P<0.05$). Meanwhile, a tighter interaction of the microbiota community in crayfish was observed in the T0.4 experimental group. In conclusion, these results suggested that dietary supplementation with 0.4% threonine could significantly promote growth and improve microbial health in juvenile C. quadricarinatus.