Indigenous chicken products are increasingly favored by consumers due to their unique meat and egg quality.  However, the relatively poor egg-laying performance largely impacts the economic benefits and hinders sustainable development of the local chicken industry.  Thus, excavating key genes and effective molecular markers associated with egg-laying performance is necessary to improve egg production via genetic selection in indigenous breeds.  In the present study, comparative hypothalamic transcriptome between pre-laying (15 weeks old) and peak-laying (30 weeks old) Lushi blue-shelled-egg (LBS) chicken was performed.  A total of 518 differentially expressed genes (DEGs) were identified.  Among the DEGs, 64 genes were enriched in 10 Gene Ontology (GO) terms associated with reproductive regulation via GO analysis and considered as potential candidate genes regulating egg-laying performance.  Of the 64 genes, 16 showed high connectivity (degree≥12) by protein–protein interaction (PPI) network analysis and were considered as potential core candidate genes (PCCGs).  To further look for key candidate genes from the PCCGs, firstly, the expression patterns of the 16 genes were examined in the hypothalamus of two indigenous breeds (LBS and Gushi (GS) chickens) between the pre-laying and peak-laying stages using quantitative real-time PCR (qRT-PCR).  Eleven out of the 16 genes showed significantly differential expression (P<0.05) with the same changing trends in the two breeds.  Then, correlations between the expression levels of the above 11 genes and egg numbers and reproductive hormone concentrations in serum were investigated in high-yielding and low-yielding GS chickens.  Of the 11 genes, eight showed significant correlations (P<0.05) between their expression levels and egg numbers, and between expression levels and reproductive hormone concentration in serum.  Furthermore, an association study on single nucleotide polymorphisms (SNPs) identified in these eight genes and egg production traits was carried out in 640 GS hens, and a significant association (P<0.05) between the SNPs and egg numbers was confirmed.  In conclusion, the eight genes, including CNR1, AP2M1, NRXN1, ANXA5, PENK, SLC1A2, SNAP25 and TRH, were demonstrated as key genes regulating egg production in indigenous chickens, and the SNPs sites within the genes might be served as markers to provide a guide for indigenous chicken breeding.  These findings provide a novel insight for further understanding the regulatory mechanisms of egg-laying performance and developing molecular markers to improve egg production of indigenous breeds.

Beak trimming was a part of routine husbandry for poultry industry, which was the most efficient and economic way to reduce the incidence of cannibalism. However, the controversy about young chicken trimming still exits and it was drawing more concern recently along with the popular of animal behavior and welfare theory. To evaluate the influence of beak trimming on young chicken spleen development and find the key regulators of the spleen development, in this study, the electron microscope technique, flow cytometry and immunohistochemical techniques were used to investigate the effects of beak trimming stress on the spleen development. The result of electronic microscope showed that significant stress response could be found in chicken spleen cells after beak trimming. Cell volume became larger, chromatin of cell nuclear agglutinated conglobation, cytoplasm formed more vacuole, and mitochondria emerged vacuolization phenomenon in splenic lymphocyte after beak trimming. From the flow cytometry, the lymphocyte of spleen in the control group and experimental group were mainly in G1 phase, and the remaining small amount was in S and M phases. Of interest, the number of the lymphocyte which are in G1 phase within immune organ in the experimental group were more than that in the control group, but the number of cells in S and M phases were less than that in the control group. And beak trimming decreased the lymphocytes proliferation index of spleen. Inmmuohistochemical result showed that the beak trimming stress did not affect the expression sites of two apoptosis-related genes, Bcl-2 and Bax, in the spleen. But the expression level of Bcl-2 decreased while Bax increased in chicken immune organs after beak trimming. Furthermore, the beak trimming increased spleen cell apoptosis with a time-dependant style. Our findings may make a contribution to the active precaution of stress response.