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 Knowledge for the CommonWealth

Let sire rank help you make sire selections.

Dairy Pipeline: May 1997

by Bennet Cassell
Extension Dairy Scientist, Genetics and Management
Virginia Tech

Most advertising material for individual bulls will focus on some strong point or unique combination of traits. The question for a potential buyer, however, is how good a bull is compared to other bulls which could be used instead. Knowing that a bull has a PTA of 1800 for milk or 1.75 for type reveals nothing about how he compares to other bulls on the market at the same time. Itās always a good idea to know where bulls rank for the combination of traits that a herd wants to improve through selection. USDA assigns "Rank Percentiles" for active AI bulls in the various breeds based on Net Merit. If only one number was available which related to a bullās genetic merit, that number should be rank percentile for Net Merit. Unfortunately, rank percentile is omitted from most advertisements and frequently isn't listed on price and proof sheets. If bulls are listed in Net Merit order, not knowing rank doesn't matter much since buying from the top of the list accomplishes about the same thing as buying bulls with high rank percentiles. What should a producer do when bulls arenāt sorted on Net Merit and rank percentiles aren't available? Keep a couple of key numbers in mind from the following table, but remember that the numbers will increase gradually until the next base change. Rank percentiles go DOWN for individual bulls over time as better bulls graduate from young sire sampling programs into active AI status. If you buy only semen from AI sampled bulls above the 90th percentile point, use up semen supplies within six months, and breed all cows and heifers AI, you have a genetic improvement program that would be hard to beat.

Minimum Net Merit value
to achieve the breed
90th percentile
80th percentile
Ayrshire  136  125
Guernsey  148  120
Holstein  173   159
Jersey  165  154
Brown Swiss  137  126

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