Evaluation of compost quality and the environmental effects of semipermeable membrane composting with poultry manure using sawdust or mushroom residue as the bulking agent.

Herein, the effects of different bulking agents (sawdust and mushroom residue), on compost quality and the environmental benefits of semipermeable film composting with poultry manure were investigated. The results show that composting with sawdust as the bulking agent resulted in greater efficiency and more cost benefits than composting with mushroom residue, and the cost of sawdust for treating an equal volume of manure was only 1/6 of that of mushroom residue. Additionally, lignin degradation and potential carbon emission reduction in the sawdust group were better than those in the mushroom residue group, and the lignin degradation efficiency of the bottom sample in the sawdust group was 48.57 %. Coupling between lignin degradation and potential carbon emission reduction was also closer in sawdust piles than in mushroom residue piles, and sawdust is more environmentally friendly. The abundance of key functional genes was higher at the bottom of each pile relative to the top and middle. Limnochordaceae, Lactobacillus and Enterococcus were the core microorganisms involved in coupling between lignin degradation and potential carbon emission reduction, and the coupled relationship was influenced by electric conductivity, ammonia nitrogen and total nitrogen in the compost piles. This study provides important data for supporting bulking agent selection in semipermeable film composting and for improving the composting process. The results have high value for compost production and process application.

A sustainable and economic strategy to reduce risk antibiotic resistance genes during poultry manure bioconversion by black soldier fly Hermetia illucens larvae: Larval density adjustment.

Black soldier fly (Hermetia illucens) larvae (BSFL) are common insects that are known for bioconversion of organic waste into a sustainable utilization resource. However, a strategy to increase antibiotic resistance gene (ARG) elimination in sustainable and economic ways through BSFL is lacking. In the present study, different larval densities were employed to assess the mcr-1 and tetX elimination abilities, and potential mechanisms were investigated. The application and economic value of each larval density were also analyzed. The results showed that the 100 larvae cultured in 100 g of manure group had the best density because the comprehensive disadvantage evaluation ratio was the lowest (14.97%, good bioconversion manure quality, low ARG deposition risk and reasonable larvae input cost). Further investigation showed that mcr-1 could be significantly decreased by BSFL bioconversion (4.42 ×107 copies/g reduced to 4.79 ×106-2.14 ×105 copies/g)(P＜0.05); however, mcr-1 was increasingly deposited in the larval gut with increasing larval density. The tetX abundance was stabilized by BSFL bioconversion, except that the abundance at the lowest larval density increased (1.22 ×1010 copies/g increase, 34-fold). Escherichia was the host of mcr-1 and tetX in all samples, especially in fresh manure; Alcaligenes was the host of tetX in bioconversion manure; and the abundance of Alcaligenes was highly correlated with the pH of bioconversion manure. The pH of bioconversion manure was extremely correlated with the density of larvae. Klebsiella and Providencia were both hosts of tetX in the BSF larval gut, and Providencia was also the host of mcr-1 in the BSF larval gut. The density of larvae influenced the bioconversion manure quality and caused the ARG host abundance to change to control the abundance of ARGs, suggesting that larval density adjustment was a useful strategy to manage the ARG risk during BSFL manure bioconversion.

The microbiota structure in the cecum of laying hens contributes to dissimilar H2S production.

BACKGROUND: Host genotype plays a crucial role in microbial composition of laying hens, which may lead to dissimilar odor gas production. The objective of this study was to investigate the relationship among layer breed, microbial structure and odor production. RESULTS: Thirty Hy-Line Gray and thirty Lohmann Pink laying hens were used in this study to determine the impact of cecal microbial structure on odor production of laying hens. The hens were managed under the same husbandry and dietary regimes. Results of in vivo experiments showed a lower hydrogen sulfide (H2S) production from Hy-Line hens and a lower concentration of soluble sulfide (S2-) but a higher concentration of butyrate in the cecal content of the Hy-Line hens compared to Lohmann Pink hens (P < 0.05), which was consistent with the in vitro experiments (P < 0.05). However, ammonia (NH3) production was not different between genotypes (P > 0.05). Significant microbial structural differences existed between the two breed groups. The relative abundance of some butyrate producers (including Butyricicoccus, Butyricimonas and Roseburia) and sulfate-reducing bacteria (including Mailhella and Lawsonia) were found to be significantly correlated with odor production and were shown to be different in the 16S rRNA and PCR data between two breed groups. Furthermore, some bacterial metabolism pathways associated with energy extraction and carbohydrate utilization (oxidative phosphorylation, pyruvate metabolism, energy metabolism, two component system and secretion system) were overrepresented in the Hy-Line hens, while several amino acid metabolism-associated pathways (amino acid related enzymes, arginine and proline metabolism, and alanine-aspartate and glutamate metabolism) were more prevalent in the Lohmann hens. CONCLUSION: The results of this study suggest that genotype of laying hens influence cecal microbiota, which in turn modulates their odor production. Our study provides references for breeding and enteric manipulation for defined microbiota to reduce odor gas emission.

Efficacy and role of inulin in mitigation of enteric sulfur-containing odor in pigs.

BACKGROUND: The efficacy and role of inulin in the mitigation of enteric sulfur-containing odor gases hydrogen sulfide (H2 S) and methyl mercaptan (CH3 SH) in pigs were examined in this study. Twelve Duroc × Landrace × Yorkshire male finisher pigs (60.7 ± 1.9 kg), housed individually in open-circuit respiration chambers, were randomly assigned to two dietary groups, namely basal diet (control) and basal diet supplemented with 1% (w/w) inulin. At the end of the 45 day experiment, pigs were slaughtered and volatile fatty acid (VFA) concentration, sulfate radical (SO42- ) concentration, population of sulfate-reducing bacteria (SRB) and expression of methionine gamma-lyase (MGL) gene were determined in contents from the caecum, colon (two segments) and rectum. Metabonomic analysis was used to compare differences in biochemical composition, and the Illumina MiSeq procedure to investigate differences in bacterial components, in the different parts of the large intestine between inulin-supplemented and inulin-free (control) groups. RESULTS: Inulin decreased (P < 0.05) the average daily enteric H2 S and CH3 SH production by 12.4 and 12.1% respectively. The concentrations of acetate, propionate and butyrate in the large intestinal content were significantly increased (P < 0.05) with inulin treatment, whereas valerate concentration and MGL mRNA expression decreased (P < 0.05). The growth of Lactobacillus, Butyrivibrio, Pseudobutyrivibrio, Bifidobacterium and Clostridium butyricum was stimulated, while that of Desulfovibrio, the dominant SRB, was inhibited, and there was an accumulation of SO42- in the large intestinal content of the inulin-supplemented pigs, suggesting that inulin mitigates H2 S generation from the SO42- reduction pathway by reducing the growth of SRB. CONCLUSION: The results showed that inulin mitigates CH3 SH generation via three methionine degradation metabolic pathways and H2 S generation from two cysteine degradation metabolic pathways, thus resulting in increased synthesis of these two sulfur-containing amino acids in the pig large intestine. © 2016 Society of Chemical Industry.

The excretion and environmental effects of amoxicillin, ciprofloxacin, and doxycycline residues in layer chicken manure.

The excretion rates and ecological risk to the environment of three commonly used veterinary antibiotics (VAs), amoxicillin, ciprofloxacin, and doxycycline, in layer hen manure during the application and withdrawal periods were investigated in a study consisting of a control group fed with VA-free basal diet and nine treatment groups consisted of three levels (200 mg/kg, 100 mg/kg, and 50 mg/kg) of amoxicillin (AMX), ciprofloxacin (CIP), or doxycycline (DOC). Each treatment group was replicated seven times with three layer hens per replication. Results of the study showed that the average excretion rates of AMX in the 200, 100, and 50 mg/kg groups were 67.88, 55.82, and 66.15%, respectively, while those for CIP and DOC were 47.84, 51.85, and 44.87% and 82.67, 94.39, and 95.72%, respectively. The concentrations of the above veterinary drugs in manure decreased sharply in the withdrawal period (7, 28, and 10 d, respectively), for AMX, DOC, and CIP. Neither AMX nor DOC was detected in the manure after the withdrawal period. In contrast to AMX and DOC, the excretion rate of CIP was significantly lower and thus had a longer residence time. Ecological risk study, estimated using hazard quotient values, showed that AMX in the 100 and 50 mg/kg groups posed no risk to the environment after d 1 of withdrawal, while CIP in the 50 mg/kg group posed no risk to the environment from d 5 of withdrawal. CIP in the 200 and 100 mg/kg groups required 10 d withdrawal in order to pose no risk to the environment. In contrast, DOC residue during withdrawal in the manure posed no risk to the environment, thus making it more environmentally safe.

Multiomics analysis of the effects of manure-borne doxycycline combined with oversized fiber microplastics on pak choi growth and the risk of antibiotic resistance gene transmission.

In this study, oversized microplastics (OMPs) were intentionally introduced into soil containing manure-borne doxycycline (DOX). This strategic approach was used to systematically examine the effects of combined OMP and DOX pollution on the growth of pak choi, analyze alterations in soil environmental metabolites, and explore the potential migration of antibiotic resistance genes (ARGs). The results revealed a more pronounced impact of DOX than of OMPs. Slender-fiber OMPs (SF OMPs) had a more substantial influence on the growth of pak choi than did coarse-fiber OMPs (CF OMPs). Conversely, CF OMPs had a more significant effect on the migration of ARGs within the system. When DOX was combined with OMPs, the negative effects of DOX on pak choi growth were mitigated through the synthesis of indole through the adjustment of carbon metabolism and amino acid metabolism in pak choi roots. In this process, Pseudohongiellaceae and Xanthomonadaceae were key bacteria. During the migration of ARGs, the potential host bacterium Limnobacter should be considered. Additionally, the majority of potential host bacteria in the pak choi endophytic environment were associated with tetG. This study provides insights into the intricate interplay among DOX, OMPs, ARGs, plant growth, soil metabolism, and the microbiome.

Biosafety assessment of laying hens fed different treatments of black soldier flies (Hermetia illucens) under doxycycline stress.

The black soldier fly (BSF, Hermetia illucens) is a resource insect that can utilize livestock and poultry feces. However, BSFs may also increase the risk of transmission of antibiotic resistance genes (AGRs) that are widespread in livestock and poultry farm environments. Therefore, we aimed to evaluate the biosecurity risks of different BSF treatments in the laying chicken food chain using the "chicken manure-BSF-laying hens" model. Our results indicated that different BSF treatments significantly affected antibiotic residue, ARGs, MGEs, bacterial antibiotic resistance, and bacterial microbial community composition in the food chain of laying hens fed BSFs. These risks can be effectively reduced through starvation treatment and high-temperature grinding treatment. Comprehensive risk assessment analysis revealed that starvation combined with high-temperature milling (Group H) had the greatest effect.

Effects of the oversized microplastic pollution layer on soil aggregates and organic carbon at different soil depths.

Soil aggregates (SAs) are the main site for soil organic carbon (SOC) fixation, and land plastic pollution is increasingly causing many soil problems. The effects of plastic on SAs and SOC seem to be significant, but there is still a lack of relevant research. This study investigated the effects of the "plastic contamination layer" (PCL) formed by the microplastic precursors (namely, oversized microplastics (OMPs)) on the content and properties of SAs of different particle sizes at different soil depths. The results showed that the PCL had an effect on SAs of different sizes at different depths: Compared with the control group, PCL mainly increased the content of SAs in 0-5 cm soil depth, about 28.08 mg macroaggregates, 13.79 mg microaggregates and 59.82 mg silt and clay aggregates per gram of soil. The presence of the PCL mainly down-regulates the organic carbon (OC) content in 0-5 cm macroaggregates, which is about 9.59 g/kg, the OC content in 10-20 cm microaggregates, which is about 16.41 g/kg, and the OC content in 0-5 cm silt and clay aggregates, which is about 4.16 g /kg, downregulated the expression of the key carbon metabolism genes (CMGs) coxL, and inhibited the contribution of the potential CMGs host bacteria Sphaerimonospora and Bacteroides to soil organic matter. This paper emphasizes that the presence of PCL reduced SOC sequestration.

The effect of manure-borne doxycycline combined with different types of oversized microplastic contamination layers on carbon and nitrogen metabolism in sandy loam.

The different forms and properties of microplastics (MPs) have different effects on the elemental cycles in soil ecosystems, and this is further complicated when the soil contains antibiotics; meanwhile, oversized microplastic (OMP) in soil is always ignored in studies of environmental behavior. In the context of antibiotic action, the effects of OMP on soil carbon (C) and nitrogen (N) cycling have rarely been explored. In this study, we created four types of oversized microplastic (thick fibers, thin fibers, large debris, and small debris) composite doxycycline (DOX) contamination layers (5-10 cm) in sandy loam, hoping to reveal the effects on soil C and N cycling and potential microbial mechanisms when exposed to the combination of manure-borne DOX and different types of OMP from the perspective of metagenomics in the longitudinal soil layer (0-30 cm). The results showed that all different forms of OMP, when combined with DOX, reduced the soil C content in each layer, but only reduced the soil N content in the upper layer of the OMP contamination layer. The microbial structure of the surface soil (0-10 cm) was more noteworthy than that of the deeper soil (10-30 cm). The genera Chryseolinea and Ohtaekwangia were key microbes involved in C and N cycling in the surface layer and regulated carbon fixation in photosynthetic organisms (K00134), carbon fixation pathways in prokaryotes (K00031), methane metabolism (K11212 and K14941), assimilatory nitrate reduction (K00367), and denitrification (K00376 and K04561). The present study is the first to reveal the potential microbial mechanism of C and N cycling under OMP combined with DOX in different layers, mainly the OMP contamination layer and its upper layer, and the OMP shape plays an important role in this process.

Effects of microplastics on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications.

Microplastics (MPs), as a new type of pollutant, widely exist in livestock and poultry breeding and agricultural soils. However, research on MPs pollution on greenhouse gas emissions in combined planting and breeding systems is lacking, especially from the perspective of phage horizontal gene transfer. Therefore, this paper explores the effects of MPs on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications. The results of the study indicated that the addition of MPs had an impact on both the physicochemical properties and microbial community structure of manure during the composting process and on the compost-applied rhizosphere soil of lactuca (Lactuca sativa). Specifically, on day 7 of composting, mcrA/pmoA and (nirS+nirK) levels in bacteria in the MP group significantly increased. Additionally, it was observed that the MP group had higher average temperatures during the high-temperature period of composting, which led to a rapid reduction in phages. However, the phage levels quickly recovered during the cooling period. Furthermore, the addition of MPs to the rhizosphere soil resulted in higher levels of nirK. These changes may affect greenhouse gas emissions.

The tigecycline resistance gene tetX has an expensive fitness cost based on increased outer membrane permeability and metabolic burden in Escherichia coli.

Livestock-derived tetX-positive Escherichia coli with tigecycline resistance poses a serious risk to public health. Fitness costs, antibiotic residues, and other tetracycline resistance genes (TRGs) are fundamental in determining the spread of tetX in the environment, but there is a lack of relevant studies. The results of this study showed that both tetO and tetX resulted in reduction in growth and an increased in the metabolic burden of E. coli, but the presence of doxycycline reversed this phenomenon. Moreover, the protection of E. coli growth and metabolism by tetO was superior to that of tetX in the presence of doxycycline, resulting in a much lower competitiveness of tetX-carrying E. coli than tetO-carrying E. coli. The results of RNA-seq showed that the increase in outer membrane proteins (ompC, ompF and ompT) of tetX-carrying E. coli resulted in increased membrane permeability and biofilm formation, which is an important reason for fitness costs. Overall, the increased membrane permeability and metabolic burden of E. coli is the mechanistic basis for the high fitness cost of tetX, and the spread of tetO may limit the spread of tetX. This study provides new insights into the rational use of tetracycline antibiotics to control the spread of tetX.

Cyclic AMP and biofilms reveal the synergistic proliferation strategy of Pseudomonas aeruginosa and Escherichia coli under the costimulation of high concentrations of microplastics and enrofloxacin.

Microplastics (MPs) provide attachment sites for biofilm formation of microorganisms, which can promote their resistance to environmental stress has been proved. However, the effect of MPs on synergy survival among microorganisms under antibiotic stress remains unclear. In the present study, the proliferation of Escherichia coli and Pseudomonas aeruginosa was assessed under enrofloxacin stress with the influence of MPs. Here, MPs reduced the growth speed of E. coli and enhanced that of P. aeruginosa, especially at 12 h, but the final value of OD600 and CFU of both bacteria not be influenced. E. coli was enrofloxacin sensitive (MIC = 0.25 µg/mL), and a high MP concentration in the presence of enrofloxacin notably enhanced the biofilm formation ability of P. aeruginosa, but proliferation decreased. In the coculture system, the proliferation of E. coli (increased 1.42-fold) and P. aeruginosa (increased 1.06-fold) both increased under enrofloxacin stress (0.25 µg/mL) with high-concentration MP addition. P. aeruginosa may provide the biofilm matrix for E. coli to resist the stress of enrofloxacin. The high concentration of cyclic AMP secreted by E. coli may slightly inhibited biofilm formation, leading to a decrease in the fitness cost of P. aeruginosa; thus, the proliferation of P. aeruginosa increased. The present study is the first to show that MP combined with antibiotics stimulates the metabolic cooperation of bacteria to promote proliferation.

Occurrence of microplastic in livestock and poultry manure in South China.

Microplastic (MP) contamination in soil has attracted much attention, and increasing evidence suggests that MPs can accumulate in agricultural soils through fertilization by compost. In addition, the most common raw materials for composting are livestock and poultry manure wastes. Because the presence of MPs may threaten the safe utilization of fertilizers composted by livestock and poultry wastes during crop planting, it is necessary to understand the contamination risk of MPs present in livestock and poultry manure. In this study, the distribution of MPs in 19 livestock and poultry farms with 3 different species was investigated by using FTIR microscopy. A total of 115 items manure MPs and 18 items feed MPs were identified as PP and PE types dominated by colorful fragments and fibers. Furthermore, after comparing the compositions of plastic products used in the feeding process, we proposed two transport pathways for MP pollution in manure and one potential transport pathway in feeds. Our result proved that the application of swine and poultry manure directly could be a new route of MPs in agricultural soil, furthermore, the presence of MPs could threaten the safety of resource utilization in agricultural soil by using swine and poultry manure for manure potentially. Not, only that, our study also provided a reference for the remediation of MP-contaminated soil.

Elimination and analysis of mcr-1 and blaNDM-1 in different composting pile layers under semipermeable membrane composting with copper-contaminated poultry manure.

The mcr-1 and blaNDM-1 elimination in copper contamination poultry manure was evaluated by semi-permeable membrane composting. The results showed the mcr-1 in control and high copper groups could not be removed, but mcr-1 decreased superlatively 80.1% in low copper treatment group. BlaNDM-1 was increased after composting, especially the copper addition groups, the results indicated that the relative abundance of mcr-1 and blaNDM-1 was obviously different in the different pile layers of copper treatment groups. Three mobile gene elements (MEGs) correlated both mcr-1 and blaNDM-1,copB correlated mcr-1, czcA and copA correlated both mcr-1 and blaNDM-1. The major phyla were Firmicutes, Bacteroidota, Actinobacteriota and Proteobacteria in all layers. The correlation analysis showed that the antibiotic resistance genes (ARGs) potential hosts could be influenced by copper form and physicochemical parameters. Semi-permeable membrane composting could decrease the abundance of major potential pathogens. Furthermore, the composting pile was not homogeneous by semi-permeable membrane composting.

Microbial Diversity and Community Variation in the Intestines of Layer Chickens.

The intestinal microbiota is increasingly recognized as an important component of host health, metabolism and immunity. Early gut colonizers are pivotal in the establishment of microbial community structures affecting the health and growth performance of chickens. White Lohmann layer is a common commercial breed. Therefore, this breed was selected to study the pattern of changes of microbiota with age. In this study, the duodenum, caecum and colorectum contents of white Lohmann layer chickens from same environment control farm were collected and analyzed using 16S rRNA sequencing to explore the spatial and temporal variations in intestinal microbiota. The results showed that the diversity of the microbial community structure in the duodenum, caecum and colorectum increased with age and tended to be stable when the layer chickens reached 50 days of age and the distinct succession patterns of the intestinal microbiota between the duodenum and large intestine (caecum and colorectum). On day 0, the diversity of microbes in the duodenum was higher than that in the caecum and colorectum, but the compositions of intestinal microbes were relatively similar, with facultative anaerobic Proteobacteria as the main microbes. However, the relative abundance of facultative anaerobic bacteria (Escherichia) gradually decreased and was replaced by anaerobic bacteria (Bacteroides and Ruminococcaceae). By day 50, the structure of intestinal microbes had gradually become stable, and Lactobacillus was the dominant bacteria in the duodenum (41.1%). The compositions of dominant microbes in the caecum and colorectum were more complex, but there were certain similarities. Bacteroides, Odoribacter and Clostridiales vadin BB60 group were dominant. The results of this study provide evidence that time and spatial factors are important factors affecting the intestinal microbiota composition. This study provides new knowledge of the intestinal microbiota colonization pattern of layer chickens in early life to improve the intestinal health of layer chickens.

Bacillus coagulans R11 consumption influenced the abundances of cecum antibiotic resistance genes in lead-exposed laying hens.

Bacillus coagulans is regarded as a clean, safe and helpful probiotic additive in the production of livestock and poultry breeds. Some studies have also shown that Bacillus coagulans can adsorb heavy metals in water, even in the gut of animals. However, whether Bacillus coagulans feeding influences antibiotic resistance gene (ARG) abundance in the gut of lead-exposed laying hens is unknown. To better apply such probiotics in the breeding industry, the present study employed Bacillus coagulans R11 and laying hens in model experiments to test ARG changes in the cecum of laying hens under lead exposure and B. coagulans R11 feeding. The results showed that there was the trend for ARG abundance decreasing in feeding B. coagulans R11 without lead exposure to laying hens in the cecum; however, feeding B. coagulans R11 to laying hens exposed to lead obviously increased the abundances of aminoglycoside and chloramphenicol ARGs. Further experiment found that hydroquinone, dodecanedioic acid, gibberellin A14, alpha-solanine, jasmonic acid and chitin were involved in the abundances of ARGs in the cecum, in addition the abundances of these compounds were also significantly enhanced by lead exposure or combination effects of lead and B. coagulans R11. As a result, the ARG hazards increased with feeding B. coagulans R11 to laying hens exposed to lead, and the key compounds which influenced by the combination effects of lead and B. coagulans R11 might influence the ARGs abundance.

A novel method for extraction of polypropylene microplastics in swine manure.

With the development of modern industry and agriculture, plentiful microplastics (MPs) were produced as a result of the abuse of plastic. The widespread presence of MPs in soils has caused coastal ecological environment pollution. Previous research has shown that fertilizer is one pathway for the entry of MPs into agricultural soils. Meanwhile, livestock manure is a major fertilizer for crops, and the application of livestock manure compost creates a potential pathway for MPs to enter soils. Thus, MPs may exist in livestock manure from the process of livestock breeding and ultimately contaminate agricultural soils. Based on the increasing attention to MP pollution, manure-born MPs will attract more interest in the future. Thus, the present study compares the extraction effects of centrifugation with fractional distillation, and an improved method is introduced to extract polypropylene (PP) from different types of swine manure. The numbers of particles and fibers were determined using a camera (MS60) connected to a stereomicroscope (Mshot MZ62), and the results showed that the recovery rate of plastic particles in swine manure based on different added numbers ranged from 71.43% ± 8.36 to 96.67% ± 3.33 with the centrifugation method, and only 31.11% ± 10.56 to 43.33% ± 12.56 using fractional distilling. The recovery rate for fibers was generally higher than for particles, especially using centrifugation, and ranged from 95.67% ± 1.58 to 100% ± 0, while the rate of fiber recovery using fractional distillation ranged from 39.44% ± 10.66 to 39.44 ± 10.66. The results of recovery rates using the two methods show that the effect of extraction by centrifugation is superior to the method of fractional distillation, with a recovery rate of approximately 100% for fibers and 90% for particles. The recovery number of microplastics evaluated with a line regression model was acceptable. Graphical abstract.

Breed differences in the expression levels of gga-miR-222a in laying hens influenced H2S production by regulating methionine synthase genes in gut bacteria.

BACKGROUND: The microbiota in the cecum of laying hens is crucial for host digestion, metabolism, and odor gas production. The results of recent studies have suggested that host microRNAs (miRNAs) can regulate gene expression of the gut microbiota. In the present study, the expression profiles of host-derived miRNAs in the cecal content of two laying hen breeds; Hy-line Gray and Lohmann Pink, which have dissimilar H2S production, were characterized; and their effects on H2S production by regulating the expression of gut microbiota-associated genes were demonstrated. RESULTS: The differential expression of microbial serine O-acetyltransferase, methionine synthase, aspartate aminotransferase, methionine-gamma-lyase, and adenylylsulfate kinase between the two hen breeds resulted in lower H2S production in the Hy-line hens. The results also revealed the presence of miRNA exosomes in the cecal content of laying hens, and an analysis of potential miRNA-target relationships between 9 differentially expressed miRNAs and 9 differentially expressed microbial genes related to H2S production identified two methionine synthase genes, Odosp_3416 and BF9343_2953, that are targeted by gga-miR-222a. Interestingly, in vitro fermentation results showed that gga-miR-222a upregulates the expression of these genes, which increased methionine concentrations but decreased H2S production and soluble sulfide concentrations, indicating the potential of host-derived gga-miR-222a to reduce H2S emission in laying hens. CONCLUSION: The findings of the present study reveal both a physiological role by which miRNAs shape the cecal microbiota of laying hens and a strategy to use host miRNAs to manipulate the microbiome and actively express key microbial genes to reduce H2S emissions and breed environmentally friendly laying hens. Video Abstract.

Metabolic activity of Bacillus coagulans R11 and the health benefits of and potential pathogen inhibition by this species in the intestines of laying hens under lead exposure.

Probiotics are widely used in agricultural breeding for care and maintenance of animal health, especially Bacillus coagulans, a new and popular species that could replace Lactobacillus. However, lead contamination in feed might influence the beneficial function. In the present study, Bacillus coagulans R11 was used as a model bacterium to investigate the effect of lead on changes in metabolites and genes, which could influence the beneficial function on laying hen. At the laboratory scale, transcriptomics and metabolomics were used to screen the main metabolites and related genes under lead exposure. The results showed that 4-acetamidobutanoic acid, dodecanoic acid, L-3-phenyllactic acid, apigenin and daidzein, which are antioxidants and antibacterial agents, were the main metabolites, even in the 100 ppm lead exposure group (the levels of these metabolites were 1.17-, 1.10-, 4.80-, 1.43- and 1.67-fold higher in the 100 ppm group than in pure culture medium). Twenty-three genes associated with the syntheses of the above 5 main metabolites were identified. Further animal experiments showed that B. coagulans R11 feeding of laying hens under lead exposure could prevent oxidative damage by increasing T-AOC and T-SOD activity and reducing the MDA concentration in serum and reducing the abundances of potential pathogens (Escherichia coli, Pseudomonas aeruginosa and Salmonella). Further analysis also showed that the inhibition of pathogen growth was due to the regulation of gene expression, as observed by transcriptomics, and these genes were associated with the abovementioned 5 main metabolites. However, the laying rate decreased by 10.53% compared with that of the control group when the lead exposure concentration was 100 mg/kg. The present study suggested that Bacillus coagulans R11 could help prevent oxidative damage and inhibit pathogen growth in laying hens to maintain a healthy intestinal environment for daily breeding, but under high-lead conditions, Bacillus coagulans R11 feeding could decrease the laying rate.

The Combination of Lead and Bacillus coagulans R11 Increased the Concentration of Alpha-Solanine in the Cecum of Laying Hens and the Pathogens Abundance Decreased.

Alpha-solanine is an alkaloid that can inhibit the growth of pathogens and cancer cells, the present study proved that feeding with Bacillus coagulans R11 increases the concentration of alpha-solanine in the cecum of laying hens, which also decreases the abundance of potential pathogens. In addition, the bacteria genera, metabolism pathways and its proteins involved in the biosynthesis of alpha-solanine in the cecum were also characterized. The results showed that B. coagulans R11 feeding could increase the concentration of alpha-solanine, even with lead exposure. Mevalonic acid and MEP/DOXP pathways were both participated in the biosynthesis of alpha-solanine; at the same time, the gut metabolites (S)-2-amino-6-oxohexanoate, N2-succinyl-L-ornithine and the bacteria proteins atoB, ispH were shown to be crucial role in the biosynthesis of alpha-solanine in the gut. The genera Faecalibacterium sp. An77 and Faecalibacterium sp. An58 2 were important in the biosynthesis of alpha-solanine, which provided the key proteins atoB and ispH. In addition, alpha-solanine could decrease the abundance of Prevotella sp. 109 and Prevotella marshii. In conclusion, alpha-solanine could be biosynthesized by cecal microorganisms with the stimulation of B. coagulans R11 in the intestine of laying hens, in addition, alpha-solanine was the main compound which also decreased the abundance of gut potential.