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Virginia Cooperative Extension - Knowledge for the CommonWealth

Take a look at your genetic improvement program

Dairy Pipeline: May 2006

Bennet G. Cassell
Extension Dairy Scientist,
Genetics & Management
(540) 231-4762; email:

Just how good are the proven AI bulls you use in your herd? Do you use AI more or less than other herds? Do you rely on AI young sires more or less than average and just how good are they compared to proven bulls? Here are state DHI averages for March 2006 to use as benchmarks. Average herd size in Virginia is 149 cows, of which 105 cows (70%) carry service to some bull.

  1. The average Virginia herd on DHI uses 14 different proven AI bulls to breed 71 cows (5 mates per proven AI bull.)
  2. Genetic merit for proven bulls is $307 for Net Merit, which ranks at the 64th percentile against all active AI proven bulls.
  3. Eight young sires in AI are mates for 17 other cows (two mates per young sire.)
  4. Pedigree merit is higher ($389 for Net Merit) than the proofs for proven AI bulls.
There will be some "pedigree slippage" by the time the proofs are out on the youngsters, but they will still compete very well with proven bulls at the 64th percentile. Another category of service sire is reserved for "all other bulls". Generally these are herd bulls kept to cover problem breeders or used in place of AI sires. Very seldom is any genetic information available for them. Check your herd's figures by looking at the "Genetic profile of service sires" on the DHI herd summary 202. Good goals for a herd breeding program would be:
  1. Rely on proven AI sires for 80-85% of all services.
  2. Strive for average rank for proven bulls above the 80th percentile.
  3. Use AI young sires for remaining services with no services to "other" bulls.
Virginia herds do use AI extensively in the lactating herd, but sire selection could be more intense in many herds. Before buying semen, check the rank of each bull for Net Merit. Stay above the 80th percentile for Net Merit on the most recent sire summary. There are plenty of choices for different traits within the top bulls for Net Merit.

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