Exploring the composition and structure of the faecal microbial community improves the understanding of the role of the gut microbiota in the gastrointestinal function and the egg-laying performance of hens. Therefore, detection of hen–microbial interactions can explore a new breeding marker for the selection of egg production due to the important role of the gut microbiome in the host’s metabolism and health. Recently, the gut microbiota has been recognised as a regulator of host performance, which has led to investigations of the productive effects of changes in the faecal microbiome in various animals. In the present study, a metagenomics analysis was applied to characterise the composition and structural diversity of faecal microbial communities under two selections of egg-laying performance, high (H, n = 30) and low (L, n = 30), using 16S rRNA-based metagenomic association analysis. The most abundant bacterial compositions were estimated based on the operational classification units among samples and between the groups from metagenomic data sets. The results indicated that Firmicutes phylum has higher significant (P < 0.01) in the H group than in the L group. In addition, higher relative abundance phyla of Bacteroides and Fusobacteria were estimated in the H group than the L group, contrasting the phyla of Actinobacteria, Cyanobacteria and Proteobacteria were more relative abundance in the L group. The families (Lactobacillus, Bifidobacterium, Acinetobacter, Flavobacteriaceae, Lachnoclostridum and Rhodococcus) were more abundant in the H group based on the comparison between the H and L groups. Meanwhile, three types of phyla (Proteobacteria, Actinobacteria and Cyanobacteria) and six families (Acinetobacter, Avibacterium, Clostridium, Corynebacterium, Helicobacter and Peptoclostridium) were more abundant in the L group (P < 0.01). Overall, the selection of genotypes has enriched a relationship between the gut microbiota and the egg-laying performance. These findings suggest that the faecal microbiomes of chickens with high egg-laying performance have more diverse activities than those of chickens with low egg-laying performance, which may be related to the metabolism and health of the host and egg production variation.

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Nowadays, there is much legislation in the world devoted to restrict the use of synthetic antibiotics in the poultry industry, which could reduce performance rate and production profits. Various phyto-biotic growth promoters have been proposed to serve as antibiotic alternatives with emphasis on plant extracts and essential oils. This study was conducted to assess the impacts of using the oregano essential oil (OEO) (comprised of 5% thymol and 65% carvacrol) and Enviva essential oil (EEO) (4.5% cinnamaldehyde and 13.5% thymol) as phytobiotic feed additives (PFA) on growth performance, cecal microbiota and serum biochemicals of growing ducks. In total, 800 11-day-old ducklings, housed in 20 floor pens, were allotted randomly into five dietary treatments: (i) A basal diet (BD) (control), (ii.) BD+50 mg EEO/kg, (iii.) BD+100 mg EEO/kg, (iv.) BD+150 mg OEO/kg and (v.) BD+300 mg OEO/kg diet. The growth performance traits were studied between 11 and 42 days of age. At the experiment end, 40 ducks were slaughtered (eight/ treatment) and cecal digesta and blood samples were collected to estimate the cecal bacterial populations and serum blood biochemicals. The results indicated that the tested levels of OEO and EEO did not display any significant effect (P>0.05) on the duck’s final BW, BW gain, growth rate, feed intake, feed conversion ratio or survivability rate. Besides, the different levels of EEO and OEO decreased the cecal populations of Coliforms (P<0.01), total aerobes (P<0.01) and lactose-negative Enterobacteria (P<0.05) in comparison with those of the control group. Finally, the tested EEO and OEO levels did not show any significant effect on the serum variables; in terms of total protein, albumin, globulin, total cholesterol, triglycerides, alanine aminotransferase and aspartate aminotransferase. In conclusion, the antimicrobial effect of the OEO and EEO against the cecal microbiota has been proven, while they did not display significant effects on the growth performance or blood variables of growing ducks.

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Precise nucleic acid editing technologies have facilitated the research of cellular function and the development of novel therapeutics, especially the current programmable nucleases-based editing tools, such as the prokaryotic clustered regularly interspaced short palindromic repeats (CRISPR)-associated nucleases (Cas). As CRISPR-based therapies are advancing toward human clinical trials, it is important to understand how natural genetic variation in the human population may affect the results of these trials and even patient safety. The development of "base-editing" technique allows the direct, stable transformation of target DNA base into an alternative in a programmable way, without DNA double strand cleavage or a donor template. Genome-editing techniques hold promises for the treatment of genetic disease at the DNA level by blocking the sequences associated with disease from producing disease-causing proteins. Currently, scientists can select the gene they want to modify, use the Cas9 as a "molecular cutter" to cut it out, and transform it into a more desirable version. In this review, we focus on the recent advances of CRISPR/Cas system by outlining the evolutionary and biotechnological implications of current strategies for improving the specificity and accuracy of these genome-editing technologies.

It has been established that gut microbiota influences chicken growth performance and fat metabolism. However, whether gut microbiota affects chicken growth performance by regulating fat metabolism remains unclear. Therefore, seven-week-old chickens with high or low body weight were used in the present study. There were significant differences in body weight, breast and leg muscle indices, and cross-sectional area of muscle cells, suggesting different growth performance. The relative abundance of gut microbiota in the caecal contents at the genus level was compared by 16S rRNA gene sequencing. The results of LEfSe indicated that high body weight chickens contained Microbacterium and Sphingomonas more abundantly (P < 0.05). In contrast, low body weight chickens contained Slackia more abundantly (P < 0.05). The results of H & E, qPCR, IHC, WB and blood analysis suggested significantly different fat metabolism level in serum, liver, abdominal adipose, breast and leg muscles between high and low body weight chickens. Spearman correlation analysis revealed that fat metabolism positively correlated with the relative abundance of Microbacterium and Sphingomonas while negatively correlated with the abundance of Slackia. Furthermore, faecal microbiota transplantation was performed, which verified that transferring faecal microbiota from adult chickens with high body weight into oneday-old chickens improved growth performance and fat metabolism in liver by remodelling the gut microbiota. Overall, these results suggested that gut microbiota could affect chicken growth performance by regulating fat metabolism.

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Programmed cell death-1 (PD-1) and its ligands, particularly PD-L1 and PD-L2, are the most important proteins responsible for signaling T-cell inhibition and arbitrating immune homeostasis and tolerance mechanisms. However, the adaptive evolution of these genes is poorly understood. In this study, we aligned protein-coding genes from vertebrate species to evaluate positive selection constraints and evolution in the PD1, PD-L1 and PD-L2 genes conserved across up to 166 vertebrate species, with an average of 55 species per gene. We determined that although the positive selection was obvious, an average of 5.3% of codons underwent positive selection in the three genes across vertebrate lineages, and increased positive selection pressure was detected in both the Ig-like domains and transmembrane domains of the proteins. Moreover, the PD1, PD-L1 and PD-L2 genes were highly expressed in almost all tissues of the selected species indicating a distinct expression pattern in different tissues among most species. Our study reveals that adaptive selection plays a key role in the evolution of PD1 and its ligands in the majority of vertebrate species, which is in agreement with the contribution of these residues to the mechanisms of pathogen identification and coevolution in the complexity and novelties of vertebrate immune systems.