牦牛乳蛋白基因杂合度与泌乳性能的关系

Relationship between individual gene geterozygosity and milking traits for yak

测定了 2 0 9头牦牛的产奶量、乳脂率、乳蛋白含量、乳糖和乳蛋白组分的相对含量等泌乳性状 ,并对每一个体分别进行 6个乳蛋白基因座的基因分型。结果表明 ,该牦牛群体平均基因杂合度为 0 1794 ,牦牛乳蛋白个体基因杂合度在0～ 0 5内 ,多数个体的基因杂合度比较低。在该群体中 ,随着个体基因杂合度的增加 ,产奶量、乳脂和α乳清蛋白 3个泌乳性状值显著增加 (P <0 0 5 )。当个体基因杂合度为 0 3333时 ,产奶量最高 ( 2 79 4 5 83kg) ,约比全群均值高出 13%( 2 4 7 12 90kg)。当个体基因杂合度为 0 5 0 0 0时 ,乳脂率最高 ( 6 5 4 83% ) ,约比全群均值 ( 5 7785 % )高出 13%。当个体基因杂合度为 0 5 0 0 0时 ,α 乳清蛋白含量最高 ( 18 10 80 % ) ,约比全群均值高出 12 %。

Milky yield(MY),milk protein percentage(MPP),milk fat percentage(MFP),lactose percentage,percentage of each type of milk protein to total protein were assayed for 209 yaks .Each type of milk protein was α lactalbumin(α La),β lactoglobulin(β Lg),casein(CN),immunoglobulin(IgG) and serum albumin(SA),respectively.Six milk protein polymorphism loci,α s1 CN,к CN,β CN,β Lg,α La and epithelial mucin(MUC 1),were genotyped for each of the yaks.Individual gene heterozygosity(IGH) was calculated for each individual and ranged from 0 0 5 in the present yak population.The results showed that most of the yak individual had low IGH and the population gene heterozygosity was very low(0 179 4),which indicated this population was a natural population lacking artificial selection and mating control Three most important traits,MY,MPP and α La,increased as IGH increasing( P <0 05).The highest MY was 279 458 3 kg when IGH was 0 333 3,which was 13% higher than the average milk yield(247 129 0 kg).The highest MFP was 6 548 3% when IGH was 0 500 0,which was 13% higher than the average milk fat(5 778 5%).The highest α La was 18 108 0% when IGH was 0 500 0,which was 12% higher than the average α La(16 104 6%).These indicated that IGH of the present yak population was too low and milking performance of yak could be improved by improving heterozygosity with controlled mating strategy.