Effects of Bacillus subtilis Natto NB205 and Its Mutant NBMK308 on Egg Quality in Aging Laying Hens

In aging laying hens, reproductive changes reduce egg quality. Bacillus subtilis natto (B. subtilis) is a versatile bacterium with high vitamin K2 content, providing health benefits for animals and humans. This study investigated the effect of B. subtilis natto NB205 and its mutant NBMK308 on egg quality in aging laying hens. Results showed that NB205 and NBMK308 supplementation significantly improved albumen height (p < 0.001), Haugh units (p < 0.05), and eggshell thickness (p < 0.001) compared to the control group. Supplementation also increased ovalbumin expression, regulated tight junction (TJ) proteins, reduced pro-inflammatory cytokine levels, and improved the health and productivity of aging laying hens by regulating key apoptosis-related genes in the magnum part of the oviduct. There were differences in the expression of vitamin K-dependent proteins (VKDPs) in the magnum between NB205 and NBMK308, but no significant differences in the improvement of egg quality. Supplementation with NB205 and NBMK308 can improve egg quality in aging laying hens.

Identification of reliable reference genes for expression studies in the magnum of laying hens housed in cage and cage-free systems

Stress factors during poultry production can evoke changes in gene transcription and protein synthesis in the hen oviduct and could affect the internal and external egg quality. Studies of relative gene expression require the identification of the most stable reference genes for the quantitative polymerase chain reaction (qPCR) to investigate the reproductive tissues' response in laying hens kept in different production systems. The objective of this study was to determine the most stable reference genes of the magnum tissues of laying hens housed in two different production systems. Hy-Line Brown hens were reared under the same sanitary conditions until 15 weeks of age. Later on, they were transferred into two different production systems, conventional cage (CC) and cage free (CF), up to 82 weeks of age. At 50 and 60 weeks, a total of six hens from each production system were euthanized, and magnum samples were collected. The qPCR was used to determine the RNA transcription level of five reference genes, ACTB, 18S, GAPDH, MSX2 and HMBS. These genes were evaluated for transcript expression in magnum tissues by NormFinder, BestKeeper, geNorm and RefFinder software. The results indicated that the most stable gene in the CF housing system was HMBS in three of the algorithms and in the CC housing system was the 18S, and the best combination of reference genes was HMBS/GAPDH in CF and 18S/HMBS in CC. In conclusion, HMBS, 18S and GAPDH genes could be used together as reference genes for the normalization of the magnum tissues transcript expression of hens in CF and CC housing systems.

Transcriptome analyses to reveal the dynamic change mechanism of pigeon magnum during one egg-laying cycle

We analyzed the transcriptome of pigeon magnum in three stages (C1: pre-ovulation, C2: post-ovulation, C3: 5-6 days after ovulation) to elucidate the molecular and cellular events associated with morphological changes during the laying cycle. We observed that C1 was highly developed, apoptosis rate was highest in C2, and C3 attained the smallest size. Through RNA-sequencing, we obtained 54,764,938 (97.2%) high-quality clean reads that aligned to 20,767 genes. Gene expression profile analysis showed the greatest difference between C1 and C3; 3966 differentially expressed genes (DEGs) were identified, of which 2250 genes were upregulated and 1716 genes were downregulated in C1. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that protein processing and transport activities were prominent in C1, and upregulated genes included those related to signal recognition particle (SRP), signal recognition particle receptor (SRPR), translocon, GRP78, RRBP1, TRAP, TRAM1, and OST. Egg white protein-related gene expression was highest, with OVALY being the most highly expressed. In C2, apoptosis-related gene expression was higher than in C1, and fatty acid metabolism was active, which may be correlated with magnum tissue regression. Collagen- and laminin-related gene expression was prominent in C1 and C3, indicating roles in egg white protein generation and magnum reconstruction. PR gene expression was highest and exhibited drastic change in the three groups, indicating that PR and its regulation may be involved in changes in magnum morphology and function. Through the identification and functional analysis of DEGs and other crucial genes, this may contribute to understand the egg white protein production, magnum tissue regression, and magnum regeneration mechanisms.

Transcriptome analysis reveals differentially expressed genes and pathways for oviduct development and defense in prelaying and laying hens

PROBLEM

The oviduct plays an indispensable role in the formation of eggs, especially the magnum and uterus. The identification of oviduct development in different stages will help to target candidate genes and pathways in regulation of albumen and eggshell formation, as well as defense mechanism in oviduct and egg.

METHODS

To identify the function differences and the molecular defense mechanism of the oviduct and egg, we performed transcriptome sequencing analysis of the magnum and uterus in 120-d-old and 300-d-old Lohmann layers, three birds in each group.

RESULTS

With fold changes (log2 ratio) ≥ 2 and false discovery rate (FDR) < 0.01, RNA-Seq revealed 1,040 genes expressed differentially in the magnum and 595 genes in the uterus. By combining GO enrichment and KEGG pathway analysis, it served to show that gene activities of the magnum and uterus in prelaying chickens were more likely to concentrate on growth and development, and after egg-laying, they were mainly inclined to enhance the substances transmembrane transport and secretion activities. We further characterized 1579 new genes, while only 803 of them were functionally annotated. A complex mixture of proteins related to defense was measured in this study. A subset of avian β-defensins (AvBDs) and ovodefensins (OvoDs), that is, AvBD12, AvBD11, AvBD10, OvoDA1, OvoDB1, OvoDA2, OvoDA3, and OvoDBβ, was detected to express in the magnum of laying hens at high levels.

CONCLUSION

Collectively, the identification and functional analysis of these differentially expressed genes (DEGs), as well as specific expression of avian defensins, may contribute to understand the development and defense mechanisms of oviduct and eggs.