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Background: Procambarus clarkii produces high-quality, delicious meat that is high in protein, low in fat, and rich in calcium and phosphorus. It has become an important aquatic resource in China. Our objectives are (i) to analyze the level of genetic diversity of P. clarkii populations; (ii) to explore the genetic differentiation (Gst); and (iii) to propose appropriate strategies for the conservation. Results: In this study, Shannon's index (I) and Nei's gene diversity index (H) for P. clarkii were high (I = 0.3462 and H = 0.2325 on average and I = 0.6264, H = 0.4377 at the species level) based on the SSR markers. The expected heterozygosity value of 17 microsatellite loci in 25 crayfish populations was 0.9317, the observed heterozygosity value was 0.9121, and the observed number of alleles per locus was 2.000; and the effective number of alleles per locus was 1.8075. Among the P. clarkii populations, the inbreeding coefficient within populations (Fis) was 0.2315, overall inbreeding coefficient (Fit) was 0.4438, genetic differentiation coefficient among populations (Fst) was 0.3145 and gene differentiation (Gst) was 0.4785 based on SSR analyses. The cluster analysis results obtained by unweighted pair-group method with arithmetic mean (UPGMA) analysis, principal coordinate analysis (PCoA) and STRUCTURE analysis were similar. A mantel test showed that the isolation-by-distance pattern was not significant. Conclusions: The high Gst among P. clarkii populations is attributed to genetic drift and geographic isolation. The results indicated that more P. clarkii populations should be collected when formulating conservation and aquaculture strategies. How to cite: Liu F, Qu Y-K, Geng C, et al. Analysis of the population structure and genetic diversity of the red swamp crayfish (Procambarus clarkii) in China using SSR markers. Electron J Biotechnol 2020;47. https://doi.org/10.1016/j.ejbt.2020.06.007.

Background: Cellulose as a potential feed resource hinders its utilization because of its complex structure, and cellulase is the key to its biological effective utilization. Animal endogenous probiotics are more susceptible to colonization in the intestinal tract, and their digestive enzymes are more conducive to the digestion and absorption of feed in young animals. Min pigs are potential sources of cellulase probiotics because of the high proportion of dietary fiber in their feed. In this study, the cellulolytic bacteria in the feces of Min pigs were isolated and screened. The characteristics of enzymes and cellulase production were studied, which provided a theoretical basis for the rational utilization of cellulase and high-fiber food in animal production. Results: In our study, 10 strains of cellulase producing strains were isolated from Min pig manure, among which the M2 strain had the best enzyme producing ability and was identified as Bacillus velezensis. The optimum production conditions of cellulase from strain M2 were: 2% inoculum, the temperature of 35°C, the pH of 5.0, and the liquid loading volume of 50 mL. The optimum temperature, pH and time for the reaction of cellulase produced by strain M2 were 55°C, 4.5 and 5 min, respectively. Conclusions:Min pigs can be used as a source of cellulase producing strains. The M2strain isolated fromfeces was identified as Bacillus velezensis. The cellulase from M2 strain had a good activity and the potential to be used as feed additive for piglets. [ABSTRACT FROM AUTHOR]

Background: In order to study the influence of long-term growth process and evolution environment on intestinal bacteria of different breeds, the intestinal bacteria and volatile fatty acids among the faeces of Min, Landrace and Yorkshire pigs were analysed by Illumina high-throughput sequencing of the 16S-rDNA and gas chromatography. Results: The shared core microbiota of Landrace, Yorkshire and Min pig were 1273, accounting for 69.56% of total abundance of organisms. The proportion of Firmicutes in Min pig faeces (57.89%) was significantly higher than that in Landrace and Yorkshire pig faeces (47.01% and 46.40%, respectively) (P < 0.05), but that of Bacteroidetes was exactly opposite. Moreover, Min pig presented more highly efficient membrane transport, environmental adaptation, carbohydrate transport, and metabolism than Yorkshire pig (P < 0.05). The acetic acid/total volatile fatty acid ratio in Min pig was significantly higher than that in Landrace pig (P < 0.05), and the isobutyric acid/total volatile fatty acid ratio in Min pig was significantly larger than that in Yorkshire pig (P < 0.05). Furthermore, the content of branched chain volatile fatty acids in Min pig was significantly higher than that in Yorkshire pig (P < 0.05). Conclusions: This study demonstrated that Min pig, as an excellent breed in the cold area of China, possessed special intestinal floral structure compared to the imported pigs in order to satisfy their physiological and metabolic demands, which may influence their characteristics such as resistance to cold, diseases, and crude feeding, and the ability to deposit intramuscular fat. [ABSTRACT FROM AUTHOR]