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Dairy Pipeline: October 2004
Bennet G. Cassell
Extension Dairy Scientist,
Genetics and Management
(540) 231-4762
email: bcassell@vt.edu
In some Virginia herds, the object of reproductive management is simply to get the cow bred, and the service sire is just a delivery system. In other herds, the service sire is an investment in the future of the herd and a matter of great concern. Combinations of these two visions of "how to breed a herd" at work around the state. The table below shows the percentage of herds that choose to breed their cows by AI and natural service and some of the results of those decisions.
| Comparison of AI practices in Virginia Holstein herds, September 2004. | ||||
| % of cows bred to non-AI bulls | % of herds in this category | Average NM$ of lactating cows | Rolling herd average milk | % sire ID |
|---|---|---|---|---|
| None | 26% | $177 | 21,471 | 83% |
| 1 9% | 26% | $158 | 20,767 | 84% |
| 10-24% | 13% | $140 | 19,839 | 77% |
| 25-74% | 15% | $107 | 18,502 | 59% |
| >74% | 20% | $72 | 17,978 | 43% |
The table shows that 65% of Virginia Holstein herds (the first three categories) choose to use herd bulls for less than 25% of the services performed. These herds have higher production and consistently do a better job of sire ID. They usually have better records of the service sires that produced calves born than herds with more bull breeding. As one might expect, the average genetic merit of cows in those herds is higher than in the herds relying on bull breeding. This difference may be understated by the average NM$ of cows in the herds, as genetic evaluations are not possible on cows that have no sire ID. We just don't know much about the genetic merit of those cows. I see the dairy business as increasingly competitive, a business where managers need to take advantage of every opportunity for greater profit. Use of genetically superior bulls is one such opportunity. While many herds in Virginia utilize this best management practice fully, there is certainly plenty of opportunity for others to join in.