Genotype by environment interaction for udder health in Swedish Holstein cows

摘要: Genotype by environment interaction for somatic cell count and mastitis in the first lactation of Swedish Holstein breed was studied, using a reaction norm model multiple trait analysis. Data from milk-recording scheme containing more than 200 000 cows having their calving 1995-01-01 onwards used. Somatic defined as average value monthly milk sampling results until 150 days after expressed 10 cells per millilitre transformed to logarithmic scale base (LSCC). Mastitis an all-or-none observed before calving. Environments were as: herd-year averages 305-day protein yield, count, mastitis, all measured lactation; herd size, number with year. Furthermore, overall size 1995-2000 sizes The analysis done two models highest lowest quartiles environments well size. genetic correlation LSCC between low high indicated GxE environment. Variances slope level analyzed regressing phenotypic values masti-tis on envi-ronment Significant variation also detected predicted offspring perform-ance showed re-ranking sires. heritability estimated functions envi-ronments tended be increased distance average. Neither nor provided us complete when environmental mastitis. This is probably due that frequency close zero environments, resulting lack pheno-typic variation.