Astragalus polysaccharides, cinnamaldehyde and their complexes affected growth, physicochemical parameters, histomorphology and flesh quality of Largemouth bass (Micropterus salmoides)

Previously, antibiotic was crucial for aquaculture development, but brought many negative effects. Cinnamaldehyde (Cia) and Astragalus polysaccharides (Asp), bioactive ingredients from Astragalus membranaceus and Cinnamomum cassia, have been confirmed their benefits to livestock. This is the first study to investigate the impacts of Cia, Asp and their joint-effect on Largemouth bass (Micropterus salmoides) growth, digestion, histomorphology and flesh quality. Fish with average weight of 72.48 ± 6.81 g were divided into 5 groups, fed with basal feed (M0); supplemented with 1 g Cia/kg diet (C1); 1.2 g Asp/kg (A1); compatibility of 1 g Cia and 1.2 g Asp/kg (CA1); 1 g Cia and 2 g Asp/kg (CA2) for 65-day. The results showed that growth, condition factor (CF) and survival rate (SR) were significantly improved in adding-groups. Especially, the greatest CF, SR, higher feed intake and conversion rate, apparent dry matter digestibility were all measured in CA1 group. The CA1 M. salmoides also exhibited higher triglyceride, aspartate aminotransferase, alanine aminotransferase and low-density lipoprotein cholesterol contents, while total-cholesterol and high-density lipoprotein cholesterol resulting in fat deposition descended in CA1 group. The activity of digestive enzymes markedly strengthened in A1 and CA1 treatments (P < 0.05). It is consistent with stronger digestive ability, the thinner muscle layers, longer villus, thicker columnar epithelium and lamina propria were found in CA1 and A1 groups. In addition, supplemented Asp was helpful to enhance antioxidant capacity of M. salmoides muscle, whilst reducing the malondialdehyde and lipid-peroxide. The nutritional composition was best in the CA1 fillets, richer in protein, least ash and fat. The histological characteristics were improved in CA1 muscles, which is the most resilient. However, most of above indices inhibited in CA2 group, particularly, the intestinal and liver damages occurred. On balance, the supplement with best aquaculture effects is CA1: 1 g Cia+1.2 g Asp/kg diet.