Duration Of Fertility Research Articles

Investigating the genetic determination of duration-of-fertility trait in breeding hens

The duration-of-fertility (DF), which was defined as the number of days when breeding hens lay fertile eggs following copulation or artificial insemination (AI), is an important economic trait in chick production when it has strong effects on fertile egg output and production costs. Little is known about the underlying genes and molecular markers related to DF trait to date. Here, we measured the DF of 701 Chinese Jinghong hens and 408 Jingfen hens. The DF showed high individual variability and potential for genetic improvement. Then, 192 Jinghong breeding hens were provided for a genome-wide association study, 27 SNPs respectively located in three genomic linkage regions (GGA1:41Kb; GGA3:39Kb and GGA8:39Kb) were suggested to be significantly associated with DF. Particularly, 6 of these 27 SNPs were further verified to be associated with DF in the 701 Jinghong and 408 Jingfen hens using PCR-RFLP genotyping method. These 27 SNPs were also mapped to 7 genes according to their genomic position. Furtherly, 5 of these 7 genes were tested using qPCR. Results show that the CYP2D6, WBP2NL, ESR1 and TGFBR3 mRNA expression levels of hens with long DF were significantly higher than the hens with short DF (P < 0.05). Overall, findings in our research provide new insight into the genetic basis of duration-of-fertility in breeding hens while providing new clues for further functional validation on the DF-related genetic regulation mechanism and improvement of DF through chicken breeding.

Genetic improvement of duration of fertility in chickens and its commercial application for extending insemination intervals

The growth rate of chickens has made remarkable progress in recent decades through continuous breeding efforts. However, this advancement has also led to a decline in fertility among commercially bred chickens. Therefore, it is crucial to understand and improve factors that influence fertility to ensure the continued success of the industry. Here, we conduct a 3-generation selection experiment within 2 purebred female lines, with the aim of increasing the duration of fertility (DF). Duration of fertility refers to the length of time hens remain capable of producing fertilized eggs and is a crucial factor that directly impacts chick output. The results showed that significant genetic progress was achieved in embryo survival rates and the fertility duration day during both the peak and late laying periods. Moreover, after 3 generations of selective breeding, the disparities in embryo survival and chick health rates from setting eggs between 8-d and 5-d insemination intervals in the grandparent stock were significantly reduced. The rates decreased from 1.83% and 2.39 to 0.72% and 0.33%, respectively. Surprisingly, the hatching performances of hens with an 8-d interval were comparable to those hens that had not undergone genetic selection for DF and had a 5-d interval. We further discussed the possibility of extending the insemination interval to 8 d in parent stock for commercial practices. The parental populations exhibited remarkable performance in terms of percentages of embryo survival and healthy chicks from the setting eggs, with rates exceeding 94 and 90%, respectively. Thus, it can be inferred that an extended insemination interval is feasible by genetic selection for DF. These findings will provide valuable insights into the efficacy of genetic selection in enhancing DF and its practical application in commercial breeding programs.

Investigation of the impact of gut microbiotas on fertility of stored sperm by types of hens

Owing to the practical interest in understanding duration of fertility (DF) to reduce the cost of producing hatching eggs by decreasing the frequency of artificial insemination, as well to uncover the mechanism of the estrogen-gut microbiome axis, elucidating the interaction between the maternal microbiome and the function of sperm storage tubules (SST) has become important for revealing the DF in laying hens. In this study, we investigated the compositional, structural, and functional differences in gut microbiomes between hens with high (HSST, n = 8) and low SST activity (LSST, n = 10) by performing phenotypic selection from approximately 400 individual hens based on their DFs. Their cecal microbial communities were analyzed by sequencing the V4 region of the 16S rRNA gene. The microbiome abundance estimators from the ceca of HSST and LSST hens were not significantly different at the phylum and genus taxonomic levels, although the relative abundances for the phylum Firmicutes and the genus Lactobacillus were higher in the HSST group. Furthermore, some taxonomic levels of bacteria expressing the components of several metabolic pathways differed between the HSST and LSST groups. Moreover, predicting functional microbiomes by Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that certain pathways, such as the metabolism of carbohydrates and protein, cellular processes, and organismal systems, of the HSST group exhibited higher expression of genes associated with bioactivity and energy biosynthesis than those in the LSST group. Our results may provide insights into hen-microbe interactions with respect to DF and will be useful in establishing a strategy for new research to uncover the functional regulation of SST in laying hens.

Gene co-expression network analysis reveals key potential gene modules in utero-vaginal junction associated with duration of fertility trait of breeder hens

The number of days (DN) when hens lay fertile eggs as well as the number of fertile eggs (FN) were produced after a single artificial insemination (AI), including the two duration of fertility (DF) traits. Indeed, they are the key production performance that associates with the production cost of hatching egg when its determination the interval between successive artificial inseminations. However, the relevant genes response for regulating the DF has not been uncovered yet. Therefore, we performed a weighted gene co-expression network analysis (WGCNA) to investigate the insight into co-expression gene modules on DF process in hens. The total mRNA was extracted from the utero-vaginal junction (UVJ, with the sperm storage function in hen’s oviduct which is the biological basis for DF) of 20 hens with several levels of DF traits, and performed transcriptome sequences of mRNA. As a result, three co-expression gene modules were identified to be highly correlated with DF traits. Moreover, the expression changes of top 5 hub genes in each module with DF traits were further confirmed in other 20 hens by RT-PCR. These findings highlighted the co-expression modules and their affiliated genes as playing important roles in the regulation of DF traits.

Novel copy number variation of the TGFβ3 gene is associated with TGFβ3 gene expression and duration of fertility traits in hens.

Improvements in the duration of fertility (DF) could increase the interval between successive artificial inseminations, thereby decreasing the cost associated with production of hatching eggs. The molecular mechanisms involved in DF in hens remains under-explored. In this study, expression levels of the transforming growth factor-β genes (TGFβs: TGFβ1, TGFβ2, TGFβ3) were investigated in utero-vaginal junctions (UVJs) of hens with long DF (Group L, n = 10) and short DF (Group S, n = 10). TGFβ1 and 2 tended to exhibit higher expression levels in UVJs from Group L hens. The expression levels of TGFβ3 mRNA and protein were significantly increased in UVJs of hens from Group L compared to hens in Group S. Consistently, six TGFβs downstream genes (DAXX, MEKK1, T-BET, GATA-3, TAK1, and FOXP3) associated with the immune response were found to be significantly differentially expressed in UVJs of Group L than Group S hens. In addition, four SNPs were identified in intron 1 of TGFβ3, and these SNPs were significantly associated with DF traits (P < 0.05). Furthermore, we identified multi-copy and copy number variants (CNVs) in chicken TGFβ3 and later determined significant associations between TGFβ3 CNVs and DF traits in hens. Specifically, TGFβ3 copy number exhibited a significant positive correlation with its expression (P < 0.05). Collectively, our results suggest that chicken DF traits may be regulated by the expression of TGFβ3 in UVJ. Meanwhile, the copy number variation in the TGFβ3 gene identified in this study seems to be one marker for DF traits.

Flourometry of Poultry Semen: Influence of Dilution and Storage on Chicken Spermatozoal Viability and Fertility

Two experiments were conducted to measure the effects of semen dilution and storage time (0, 1, 2, 3, 4, 24, and 48 h) at 22 C on spermatozoal viability (i.e., membrane permeability to ethidium bromide) and to determine the relationship between concentration of viable spermatozoa inseminated (25, 50, 100, and 200 × 106) and fertility. In Experiment 1, percentages of dead spermatozoa remained relatively constant during the 4-h postcollection period but increased significantly (P<.05) at 24 and 48 h. Sperm viability after 48 h was significantly higher in diluted semen than in undiluted semen. Percent (PF) and duration of fertility (DF) from undiluted semen significantly declined during the 4-h postcollection period compared with fertility of diluted semen. In Experiment 2, both PF and DF improved as the concentration of viable spermatozoa increased. Fertility was not significantly improved by inseminating more than 100 × 106 viable spermatozoa. The fertilizing capacity of chicken spermatozoa from undiluted semen was affected during storage before membrane permeability to ethidium bromide was altered.