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We conducted an 8-week feeding trial to investigate the effect of mixed functional oligosaccharides (chitosan oligosaccharide, fructooligosaccharide, and xylooligosaccharide) extracted from wheat straw on the growth, feeding, physiology, histology, muscle texture, and gut microbiota of Micropterus salmoides. Six diets were formulated by incrementally adding mixed functional oligosaccharides (0.1, 0.5, 1.0, 1.5, and 2.0 mg/kg) to the control diet. 30 individuals with initial body weight of 25.1 ± 3.5 g were randomly allocated to 6 triplicate tanks and fed to apparent satiation twice daily. The fish fed 1.0 mg/kg additives displayed maximum growth, and the feed conversion ratio decreased with the increase in additives from 0 to 1.0 mg/kg (P < 0.05) but did not decline further with the addition of more than 1.0 mg/kg (P > 0.05). The villus height and width were significantly higher in the supplementation groups than in the control group, while the gut and liver structures presented abnormalities with excessive supplementation above 1.5 mg/kg. There were significant differences in muscle texture indices for M. salmoides over the fed additive gradient, and the hardness, gumminess, and chewiness were highest in the 1.0 mg/kg group. High oligosaccharide levels, such as 2.0 mg/kg, decreased the LZM level, while there were no significant differences in the SOD and MDA levels. Gut microbiome analysis revealed no significant differences in richness and diversity for groups fed the functional oligosaccharide gradient; however, the PCoA results showed that the microbial community composition changed markedly in response to different addition levels, and the 0.5 and 1.0 mg/kg supplementation groups were far apart from the lower and higher supplementation groups. The relative abundance of Proteobacteria was lower in the 0.5 and 1.0 mg/kg addition groups, while that of the phyla Fusobacteria and Firmicutes were higher in these two groups. Functional classification showed that microbes related to carbohydrate metabolism were more abundant in the 0.5 and 1.5 mg/kg groups than in the other groups. [ABSTRACT FROM AUTHOR]

Background: Chinese soft-shell turtle (Pelodiscus sinensis) is an important commercial species for their high nutritional value and unique taste, but it has been a vulnerable species due to habitat loss. In this study, homologous juvenile turtles were allocated to lake, pond and paddy field to investigate the habitat effects on turtles. Results: The growth, morphology and gut microbial communities were monitored during the 4 months cultural period. It showed higher growth rate of turtles in paddy field and pond. The appearance, visceral coefficients, gut morphology and microbial communities in turtles were distinct among different habitats. The microbial community richness on Chao1 was obviously lower in initial turtle guts from greenhouses, whereas it was relative higher in turtle guts sampled from paddy fields than ponds and lake. Significant differences on dominant microbes were found among initial and subsequent samples from different habitats. Firmicutes was the most abundant phylum in the guts of turtles sampled from the greenhouse initially, while Proteobacteria was the most abundant phylum after cultivation in different habitats, followed by Bacteroidetes. The microbial composition were distinct in different habitats at 60d, and the appearance of dominant phyla and genera was more driven by sampling time than habitats at 120d. Both the sampling time and habitats affected the appearance of dominant phyla and genera during the cultivation. The functional predictions indicated that both habitat type and sampling time had significant effects on metabolic pathways, especially amino acid and carbohydrate metabolism. Conclusions: The turtles could adapt to natural lakes, artificial ponds and paddy fields. The gut microbial abundance was different among the habitats and sampling time. The species of microbes were significantly more diverse in paddy field specimens than in those from ponds and lakes. Rice-turtle coculture is a potential ecological and economic farming mode that plays important roles in wild turtle protection and food security. [ABSTRACT FROM AUTHOR]