The aims of the current study were to assess genetic diversity, conduct genetic characterization, and evaluate usefulness of an individual assignment test for 12 commercial chicken lines using 40 microsatellite markers. A total of 268 distinct alleles were observed across the 12 lines, and 42 of the 268 alleles (15.7%) were unique to only 1 line. Mean observed heterozygosity within a line ranged from 0.295 to 0.664, and the highest value was obtained from 1 of the White Plymouth Rock lines. Significant deviations from the Hardy-Weinberg equilibrium were observed at several locus-line combinations, showing excess of heterozygotes in many cases. As a whole, genetic differences among the lines estimated by the fixation index were high at 29.8%, whereas higher genetic similarity was observed among White Leghorn lines despite their different breeding histories. Assignment test could correctly allocate individuals at the line level to their origins, with a high accuracy (96.6%). Individual-based genetic characterization would be a usable step to conserve chicken genetic resources. Here, guidelines for future breeding and management of these lines by the poultry industry are provided.
Abstract. The goal of our present study was to observe whether the populations of antigen presenting cells (Ia+ cells) and T cell subsets (CD4+ and CD8+ T cells) change in the utero-vaginal junction (UVJ) of Rhode Island Red laying hens that showed dramatic declines in fertility after repeated artificial insemination (AI). Rhode Island Red laying hens were divided into two groups: a virgin group (R-V) and artificial inseminated group (R-AI), which was exposed to weekly AI for a period of 3 mo. Undiluted fresh semen collected from healthy Tosa-Jidori roosters, a native Japanese breed maintained in Kochi Prefecture, was used for AI. The UVJ tissues were processed for frozen sections, and Ia+ cells and CD4+ and CD8+ T cells were identified by immunohistochemistry. The Ia+ cells and CD4+ and CD8+ T cells were observed in the stroma and mucosal epithelium of UVJ in both the R-AI and R-V birds. The frequencies of them in the stroma were significantly higher in R-AI than R-V. The higher frequency of Ia+ cells in the UVJ of R-AI group indicated a greater potential capability for antigen presentation to CD4+ cells. The significant increase in CD8+ and CD4+ T cells in the UVJ of R-AI birds might be the result of a homing process of lymphocytes, which may affect sperm survivability and fertility.
Molecular markers are a useful tool for evaluating genetic diversity of chicken genetic resources. Seven chicken lines derived from the Plymouth Rock breed were genotyped using 40 microsatellite markers to quantify genetic differentiation and assess conservation priorities for the lines. Genetic differentiation between pairs of the lines (pairwise FST) ranged from 0.201 to 0.422. A neighbor-joining tree of individuals, based on the proportion of shared alleles, formed clearly defined clusters corresponding to the origins of the lines. In Bayesian model-based clustering, most individuals were clearly assigned to single clusters according to line origin and showed no admixture. These results indicated that a substantial degree of genetic differentiation exists among the lines. To decide priorities for conservation, the contribution of each line to the genetic diversity was estimated. The result indicated that a loss of 4 of the 7 lines would lead to a loss from 1.14 to 3.44% of total genetic diversity. The most preferred line for conservation purposes was identified based on multilocus microsatellite analysis. Our results confirmed that characterization by means of molecular markers is helpful for establishing a plan for conservation of chicken genetic resources.
The goal of this study was to determine the mechanism by which the fertility was declined by repeated artificial insemination (AI) in laying hens. The structures of sperm storage tubules (SST) and lymphocytes population in the uterovaginal junction (UVJ) of Rhode Island Red hens showing a declined fertility after repeated AI with Tosa-jidori semen and of virgin hens were examined histologically in experiment +. Then, the sperm storage abilities of those hens were examined in experiment ,. In experiment +, the SST was swollen with thinning of epithelium, and the population of lymphocytes was greater in the UVJ of hens showing a declined fertility after repeated AI compared with virgin hens. In hens showing a lower fertility, few sperm were present in SST, and lymphocytes invading into SST lumen after AI were observed (experiment ,). These results suggest that repeated AI may cause the destruction and abnormality in the functions of SST, and anti-sperm immunoresponse may occur in those SST in the birds used for current study. In these birds sperm could not be retained in SST, resulting in decline of fertility. Such abnormality of SST may be one of the factors involved in the decline of fertility by repeated AI in the other breeds that are reported elswhere.
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