Effects of dietary compound acidifiers supplementation on growth performance and intestinal health of juvenile American eels (Anguilla rostrata) cultured in cement tanks

Abstract

This experiment was conducted to investigate the effects of compound acidifiers (CAs) on the growth performance and intestinal health of juvenile American eels (Anguilla rostrata) cultured in cement tanks. Six cement tanks with similar fish size and weight (approximately 4 g/fish and 87 kg/tank) were randomly divided into control group and CAs group with three replicates each. The fish of two groups were fed commercial diet and commercial diet supplemented with 4 g/kg CAs, respectively. The trial period was 56 days. The dietary CAs supplementation significantly increased final fish weight, weight gain rate, specific growth rate and feed intake (P<0.05). There were no significant differences in feeding rate, feed efficiency, and survival rate between the control group and CAs group (P>0.05). Protease activity in intestine was increased significantly by CAs supplementation (P<0.05). Lipase activity and amylase activity were similar between control group and CAs group (P>0.05). CAs supplementation significantly increased the villi length and thickness of the intestinal muscular layer (P<0.05). Dietary CAs supplementation increased the richness and the diversity of intestinal microbiota. At the phylum level, the higher relative abundances of Proteobacteria, Actinobacteria and Bacteroidetes and the lower relative abundance of Firmicutes were observed in CAs group compared to the control group. At the genus level, dietary CAs supplementation significantly increased the relative abundances of Faecalitalea, Sphingomonas, Sutterella and Mycobacterium (P<0.05). In conclusion, the dietary 4 g/kg CAs supplementation might improve the growth performance and intestinal health of juvenile American eels cultured in cement tanks.

Effects of White Fish Meal Replaced by Low-Quality Brown Fish Meal with Compound Additives on Growth Performance and Intestinal Health of Juvenile American Eel (Anguilla rostrata)

“…Tenericutes, Firmicutes, Proteobacteria and Spirochaetae were the four major phyla of bacteria in this study, which were similar to the results in the previous studies about the composition of the intestinal microbiota of American eels [ 14 , 19 , 44 , 51 ]. As for the changes in bacteria at the phylum level, Tenericutes might promote the growth of fish and inhibit the proliferation of pathogenic bacteria in the intestine [ 52 ].…”

“…Macleaya cordata extract could maintain the intestinal structural integrity by upregulating the expression of intestinal tight junction protein-related genes [ 45 ]. Similarly, the compound acidifiers also had positive effects on maintaining the parameters of the intestinal morphology of American eels [ 19 ], which could be ascribed to its ability to promote the proliferation of intestinal epithelial cells and decrease intestinal permeability [ 46 , 47 ]. Notably, the aforementioned intestinal morphological parameters in the 30% and 40% LQBFM groups with higher histamine levels were significantly poorer than those in the LQBFM20+CAs group.…”

“…It was reported that dietary 300 mg/kg grape seed proanthocyanidins could reverse the alteration of 534 mg/kg histamine on the diversity or abundance of the intestinal microbiota of juvenile American eels [ 44 ]. At present, the effects of Macleaya cordata extract or compound acidifiers on the alpha diversity of intestinal microbiota were not reported under dietary histamine stress but the alpha diversity of the intestinal microbiota was affected by supplementation of those two feed additives individually without dietary stressors [ 14 , 19 ]. The roles of those two feed additives in regulating the intestinal microbiota under the high level of histamine in the diets of juvenile American eels should be confirmed in future research.…”

“…Little information was known about the role of Iamia and Breznakia in fish [ 58 , 59 ]. According to the results of previous studies, there should be higher relative abundances of some pathogenic bacteria in the intestine of juvenile American eels in theory [ 14 , 19 , 51 ]. Nevertheless, there could be more probiotics in the intestine of juvenile American eels from the LQBFM20+CAs group.…”

“…In recent years, some functional feed additives, including Macleaya cordata extract [ 14 ], grape seed proanthocyanidins [ 15 ] and compound acidifiers [ 16 ], have been individually supplemented in eel diets to improve the parameters of growth and intestinal health status of American eels ( Anguilla rostrata ). The principal biological activities of these functional additives are anti-inflammatory, antioxidant and beneficial shaping of the microflora in the intestine, respectively [ 17 , 18 , 19 ]. The beneficial effects of them on growth and health may counteract the adverse impact caused by histamine from LQBFM.…”