Background: Intramuscular fat (IMF) is one of the important factors influencing meat quality, however, for chickens, the molecular regulatory mechanisms underlying this trait have not yet been determined. In this study, a systematic identification of candidate genes and new pathways related to IMF deposition in chicken breast tissue has been made using gene expression profiles of two distinct breeds: Beijing-you (BJY), a slow-growing Chinese breed possessing high meat quality and Arbor Acres (AA), a commercial fast-growing broiler line. Results: Agilent cDNA microarray analyses were conducted to determine gene expression profiles of breast muscle sampled at different developmental stages of BJY and AA chickens. Relative to d 1 when there is no detectable IMF, breast muscle at d 21, d 42, d 90 and d 120 (only for BJY) contained 1310 differentially expressed genes (DEGs) in BJY and 1080 DEGs in AA. Of these, 34–70 DEGs related to lipid metabolism or muscle development processes were examined further in each breed based on Gene Ontology (GO) analysis. The expression of several DEGs was correlated, positively or negatively, with the changing patterns of lipid content or breast weight across the ages sampled, indicating that those genes may play key roles in these developmental processes. In addition, based on KEGG pathway analysis of DEGs in both BJY and AA chickens, it was found that in addition to pathways affecting lipid metabolism (pathways for MAPK & PPAR signaling), cell junction-related pathways (tight junction, ECM-receptor interaction, focal adhesion, regulation of actin cytoskeleton), which play a prominent role in maintaining the integrity of tissues, could contribute to the IMF deposition. Conclusion: The results of this study identified potential candidate genes associated with chicken IMF deposition and imply that IMF deposition in chicken breast muscle is regulated and mediated not only by genes and pathways related to lipid metabolism and muscle development, but also by others involved in cell junctions. These findings establish the groundwork and provide new clues for deciphering the molecular mechanisms underlying IMF deposition in poultry. Further studies at the translational and posttranslational level are now required to validate the genes and pathways identified here.

Ex situ preservation is an important method in the preservation of chickens, and cryopreservation of semen is the only method for gamete preservation at present. During the last two decades, many studies have been performed to develop standard chicken semen cryopreservation technology and achieve great progress. Many attempts and methods were investigated to adapt subspecies or different breeds. In this paper, we firstly reviewed the main factors affecting cryopreservation of chicken sperm, including the unique structure and characteristics of the spermatozoa. Secondly, the studies on key points of the chicken sperm cryopreservation technology, including semen dilution, cryoprotectants, equilibration time, packaging types, and freezing and thawing rates were summarized to generate the optimal parameters. Then, the mechanism underlying freezing damage and freezability revealed by recent omics methods relevant to the efficiency of cryopreservation were discussed. This review will provide relevant reference for the future investigation of poultry semen cryopreservation technology.

Poultry genetics resources, including commercial selected lines, indigenous breeds, and experimental lines, are now being irreversibly lost at an alarming rate due to multiple reasons, which further threats the future livelihood and academic purpose. Collections of germplasm may reduce the risk of catastrophic loss of genetic diversity by guaranteeing that a pool of genetic variability is available to ensure the reintroduction and replenishment of the genetic stocks. The setting up of biobanks for poultry is challenging because the high sensitiveness of spermatozoa to freezing–thawing process, inability to cryopreserve the egg or embryo, coupled with the females being heterogametic sex. The progress in cryobiology and biotechnologies have made possible the extension of the range of germplasm for poultry species available in cryobanks, including semen, primordial germ cells, somatic cells and gonads. In this review, we introduce the state-of-the-art technologies for avian genetic resource conservation and breed reconstruction, and discuss the potential challenges for future study and further extending of these technologies to ongoing and future conservation efforts.

Sperm motility is used to predict the semen quality and fertilization ability of breeder roosters. Indigenous chicken breeder roosters show variation

Semen quality is important for roosters' fertility. The correlations between semen quality traits and fertility has less been analyzed, impeding the selection of effective parameters for roosters selection. This research aimed to investigate the variation in semen quality traits in relation to fertilization capacity between 2 chicken breeds. A total of 156 Rhode Island Red (n = 78) and White Leghorn (n = 78) roosters of 53 wk were selected for semen quality estimation including semen volume, pH, sperm concentration, motility, viability, abnormal sperm percentage, and sperm kinematic parameters. Individual fertility was measured by artificial insemination using each 30 birds from 2 breeds. Significant variations were observed between breeds in semen volume, pH, sperm motility (MOT), viability, and abnormal sperm percentage (P < 0.05). The volume, MOT, and viability in Rhode Island Red were higher than those of White Leghorn roosters (P < 0.001). In addition, sperm kinematic parameters such as curvilinear velocity (VCL), straight line velocity (VSL), amplitude lateral head displacement (ALH), and average path velocity (VAP) in Rhode Island Red were higher than those of White Leghorn (P < 0.001). Fertility rate was positively correlated with MOT (r = 0.57), concentration (r = 0.43), viability (r = 0.39), VSL (r = 0.36), ALH (r = 0.43), and ALH (r = 0.38) for Rhode Island Red roosters (P < 0.05). Fertility rate of White Leghorn roosters was positively correlated with MOT (r = 0.71), concentration (r = 0.39), VCL (r = 0.52), ALH (r = 0.50), and VAP (r = 0.39) (P < 0.05). Principal component analysis of sperm kinematic descriptors revealed 2 principal components explaining more than 65% of total variance. In addition, for both genetic lines, the whole population was divided into 3 independent clusters. These results indicated that selection of roosters based on semen quality traits for may improve the fertility, and multivariate analysis may help to precise selection by comprehensive usage of different measures of sperm quality.

Sperm motility is the most important indicator in evaluating roosters’ fecundity. However, the genetic mechanisms underlying chicken sperm motility is not yet clear. Long non-coding RNA (lncRNA) play epigenetic roles in reproduction. In this study, RNA sequencing was employed to profile the testis transcriptome (lncRNA and mRNA) of six Beijing-you cocks divergent in sperm motility. In total, 2,597 lncRNAs were identified in the chicken testis, including 1,267 lincRNAs, 975 anti-sense lncRNAs, and 355 intronic lncRNAs. They shared similar features with previous studies. Of these lncRNAs, 124 were differentially expressed. Among 17,690 mRNAs detected in this study, 544 were differentially expressed, including a bunch of genes with known functions on sperm motility. GO annotation analysis revealed these genes were involved in ATP binding, cilium assembly, and oxidation-reduction processes. Integrating analysis of lncRNA and mRNA profiles predicted 10 lncRNA-gene pairs, including 8 co-regulated and 2 inversely-regulated pairs. To the best of our knowledge, this is the first genome-wide investigation of the lncRNAs in the chicken testis associated with sperm motility. Our results provided a catalog of chicken testis lncRNAs and genes worthy of further studies to understand their roles in cocks’ reproductive performance regulation.