| Fertility is considered as one of the most important economic traits in modern poultry industry. With the popularity of artificial insemination technique, there is an urgent demand for roosters which is able to produce an adequate quantity and quality of semen, because this can influence the number of im-pregnated females. For that matter, semen evaluation has been accepted as a way to estimate potential fertility of a male and then to maximize the number of offspring from those valuable ones. The study consists of two parts,the first one was to estimate the genetic parameters of semen quality-related traits, the second one was to select the relevant candidate gene. All of studies were basic research for improv-ing and select the fertility of chicken.The first study was conducted to estimate the genetic parameters of semen quality-related traits, us-ing a MTDFREML procedure, in 516 purebred Beijing-You (BJY) full-sib male chickens derived from the same hatching, and subsequently to assess the feasibility of genetic selection to improve the semen quality of BJY chickens. Genetic parameters were estimated using an animal model which was consid-ered the result of non-genetic factor analysis. The heritabilities and correlations among semen volume after ejaculation(VOL), semen pH(pH), semen color score (COL), sperm viability(VAI), sperm motility score (MOT), the percentage of abnormal spermatozoa (ABN), and Sperm density(DEN) were estimated. The results show that the estimated heritabilities of VAI, MOT, and ABN were high (ranging from 0.52 to 0.85), whereas the heritabilities of VOL, COL, and DEN were moderate(0.28, 0.19, and 0.12, respectively).Genetic correlations between ABN andVAI and MOT were both negative (–0.37 and–0.27, respectively), whereas a high positive genetic correlation was found between VAI and MOT (0.88). This indicates that adopting certain breeding measures to improve sperm motility rate and vitality, might reduce the rate of abnormal sperm rate and results in counter-productive effects.Based on the first trial, the sperm-associated antigen 6(SPAG6)gene was studied in 390 Bei-jing-You chickens and regarded as a candidate gene for semen quality traits. Sequencing was applied to analyze the association between SNPs and their heliotypes in SPAG6 gene's intron 5 with semen quality, in order to provide the relevant candidate genes or some molecular markers for the MAS application. The results were as follows:1 Five SNPs were identified in intron 5 of SPAG6 gene, they were A20353G(SN1),T20427C(SN2), T20497C(SN3), T20569C(SN4) and G20587A(SN5). After linkage analysis, it was found that there were complete linkage between SN1 and SN2, SN4 and SN5.2 The effect of polymorphisms of SPAG6 gene on semen quality traits was analyzed, the results in-dicated that the polymorphism of SN1(SN2)was significantly associated with ABN. In SN3 loci, The chicken with genotype B3B3 showed lower ABN(P<0.05), but MOT and VAI traits were lower than genotype A3B3 and A3A3(P<0.05). In SN4 loci, B4B4(B5B5)was higher MOT and lower ABN than A4A4(A5A5)(P<0.05), thus, B4B4(B5B5)was considered as predominance genotype.3 Haplotype combinations in SPAG6 intron 5 with semen quality traits were studied. In this study, the birds with haplotype combinations H1H6 had the highest VOL and VAL. Although the birds with haplotype combinations H1H7 had higher VAL and lowest ABN, the VOL was lowest than other haplo-type combinations.In conclusion, H1H6 was predominance haplotype combinations and it could be considered as candidate molecular marker for semen quality. |
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