Lundén A, Edfors-Lilja I, Johansson K, Liljedahl L E
Department of Animal Breeding and Genetics, Swedish Univeristy of Agricultural Sciences, Uppsala.
Poult Sci. 1993 Jun;72(6):989-99. doi: 10.3382/ps.0720989.
The frequency of the MHC haplotype B15 had been found in a previous study to be more than two times higher in a White Leghorn line selected for high egg production compared with the unselected control strain. To further evaluate these findings, matings were performed between chickens with the same heterozygous B genotypes, being combinations of the most frequent haplotypes, i.e., B15, B19, and B21. In total, more than 1,300 observations from two generations were analyzed. In each generation, approximately one half of the chickens were derived from the line selected for total egg mass, the other half from the control strain. The MHC genotypes were determined serologically. Additive and dominance effects of B haplotypes on production traits were analyzed using an individual animal model. The estimation of genotypic values, together with the analysis of gene substitution effects, showed that the B15 haplotype was associated with early sexual maturity and low egg production during the late production period, i.e., between 43 and 63 wk of age, whereas B19 was associated with later onset of sexual maturity. The association of B15 with early sexual maturity would thus explain the high frequency of the B15 haplotype previously observed in a line selected for high early egg production. No dominance effect of the B system was observed for any of the traits, suggesting that the present results were due predominantly to additive gene effects.
在之前的一项研究中发现，与未选的对照品系相比，在一个为高产蛋量选育的白来航品系中，MHC单倍型B15的频率高出两倍多。为了进一步评估这些发现，让具有相同杂合B基因型（即最常见单倍型B15、B19和B21的组合）的鸡进行交配。总共分析了来自两代的1300多个观察结果。在每一代中，大约一半的鸡来自为总蛋重选育的品系，另一半来自对照品系。通过血清学方法确定MHC基因型。使用个体动物模型分析B单倍型对生产性状的加性和显性效应。基因型值的估计以及基因替代效应的分析表明，B15单倍型与早期性成熟以及产蛋后期（即43至63周龄）的低产蛋量相关，而B19与性成熟较晚相关。因此，B15与早期性成熟的关联可以解释在一个为高早期产蛋量选育的品系中先前观察到的B15单倍型的高频率。对于任何性状均未观察到B系统的显性效应，这表明目前的结果主要归因于加性基因效应。
