Norberg E, Rogers G W, Ødegård J, Cooper J B, Madsen P
Department of Genetics and Biotechnology, Danish Institute of Agricultural Sciences, Research Center Foulum, P.O. Box 50, DK-8830 Tjele, Denmark.
J Dairy Sci. 2006 Feb;89(2):779-81. doi: 10.3168/jds.S0022-0302(06)72139-7.
Electrical conductivity (EC) of milk is an indicator of mastitis. If EC shows genetic variation and is genetically correlated to mastitis, it could be used in a breeding program that includes selection for improved mastitis resistance. In this study, daily records of EC and mastitis from about 1,500 Holstein cows were analyzed. A bivariate animal model was used for estimation of (co)variance components, including fixed effects of age of calving, herd-test-day, and days in milk, in addition to random additive genetic effects and permanent environmental effects. For EC, the estimated heritability was moderate (0.22 to 0.39), whereas for mastitis, the heritability was low (0.013). The genetic correlation between EC and mastitis was estimated to be 0.75, and genetic improvement of mastitis resistance should be feasible through selection for reduced EC.
牛奶的电导率（EC）是乳腺炎的一个指标。如果EC表现出遗传变异且与乳腺炎存在遗传相关性，那么它可用于一个包括选择提高乳腺炎抗性的育种计划中。在本研究中，分析了约1500头荷斯坦奶牛的EC和乳腺炎的每日记录。采用双变量动物模型来估计（协）方差成分，除了随机加性遗传效应和永久环境效应外，还包括产犊年龄、牛群-测试日和泌乳天数的固定效应。对于EC，估计的遗传力适中（0.22至0.39），而对于乳腺炎，遗传力较低（0.013）。EC与乳腺炎之间的遗传相关性估计为0.75，通过选择降低EC来实现乳腺炎抗性的遗传改良应该是可行的。
