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Virginia Cooperative Extension - Knowledge for the CommonWealth

Prepare for fall semen purchases

Dairy Pipeline: August 1998

Bennet Cassell
Extension Dairy Scientist, Genetics and Management
Virginia Tech
540/231-4762, email: bcassell@vt.edu

August bull proofs signal the Virginia dairy industry to get ready for fall breeding season. Here are some steps to consider before making those critical semen purchase decisions.

  1. Take inventory. How much semen do you need? Should some of the semen in the inventory be discarded? That's a hard step for some dairy farmers to take, but it may be the most important decision you make this fall as far as genetic improvement is concerned.
  2. Which AI bulls have lots of daughters and granddaughters in your herd? Cows sired by bulls that were at the top of Net Merit and TPI lists when the semen was used could well have half brothers in active AI service now. Those first calf heifers sired by AI young sires or the better pedigreed herd bulls are another potential problem. Their paternal grandsires will be showing up as sires and maternal grandsires of some of the bulls in AI service.
  3. You should have your herd mated to manage (not just avoid) inbreeding. To do this job right, each bull you plan to use this fall should be considered as a mate to each cow. Subtract 80 lbs. for each 1% inbreeding in a potential calf from the bull's PTA for milk and use the bull with the highest adjusted PTA. Each bull will have several adjusted PTA's for different potential mates in the herd. He might be a great mate for one cow and a terrible choice for another when inbreeding is considered.
  4. The ideal way to deal with inbreeding is a lot of trouble without computer help. Alternative: choose service sires from the top of Net Merit or TPI lists and note their sire and maternal grandsire. Do not use a bull as a mate to a cow whose sire or maternal grandsire is the same as the sire or maternal grandsire of the bull. Ask your AI company or breed association if they have or when they will have a mating program that manages inbreeding as suggested in #3.



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