1Tools for selection for functional traits in Canada

The Total Economic Value index (TEV) for dairy sires has been published in Canada since 1996. The TEV is an index based on total economic merit that allows breeders to select bulls for simultaneous improvement of both production and functional traits. The TEV uses a sub-index approach to combine sire EBV for yield, longevity, and udder health traits. Relative weights for the production, longevity, and udder health sub-indexes are 10, 4, and 1.5, respectively. Within the production sub-index, EBV for protein yield receives a weight of 9, relative to 2 for fat yield. The EBV for protein and fat are actually also sub-indexes, created by combining with approximately equal weights the individual EBV for yields in first, second, and third lactations. No direct emphasis is placed on milk yield. The longevity sub-index for a bull is simply its published EBV for herd life, which is calculated by combining direct information on actual daughter survival and indirect information based on conformation. The sub-index for udder health blends EBV for somatic cell score (SCS), udder depth, and milking speed. Relative weights for these 3 components are-13, 6, and 3, respectively. Similar to the yield traits, the overall EBV for SCS is a combination of separate EBV for SCS in lactations 1 to 3. The TEV i