Select Sires

Heat Detection (Part 1)
Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Nov. 13, 2003
With Ray Nebel,
extension specialist and professor of reproductive management,
Virginia Tech

Today’s Reproductive moment is with Ray Nebel, extension specialist and professor of reproductive managements at Virginia Tech. Ray, how soon should a cow be bred following a standing heat? Those that follow the am/pm rule say that if you see them in heat in the morning you breed them in the afternoon and if you see them in the night you breed them the next morning. So, what’s the best approach there?

Timing of insemination really should be based on the onset of estrus. The am/pm rule was established for two times a day heat-detection. If we catch a cow in heat this morning, it says she wasn’t in heat yesterday afternoon when we checked. And if we didn’t see her in heat this morning but catch her in heat this afternoon, this says when we went out this morning she wasn’t in heat but she is in heat this afternoon. So, the more often we go out and visually observe cows, the better job we can do of timing when insemination should occur. The biological events that determine conceptions are the life of the sperm and the life of the egg. The life of the egg is much shorter than the life of the sperm. The life of the egg is roughly eight to 12 hours. The life of the sperm in the female reproductive tract of the cow is roughly 24 to 36 hours. We would like to have sperm in there to defy fertilization waiting for the egg because it has a much longer life span. Therefore, the old adage of the am/pm rule still holds up if we do three times a day heat-detection.

What about twice a day heat-detection?

If we observe heat only twice a day, the recommendation is to breed about four hours after observation. This is due to the fact that we can’t time when that heat actually started. If we observe cows only once a day, we need to inseminate as soon as possible after observation because all it says is: if we observe her in heat now, and she wasn’t in heat yesterday at the same time, then it’s somewhere in the last 24 hours, so we to put the semen in there as soon as possible. So, again, the timing of insemination should be based on the heat-detection program, and the am/pm rule holds only if we are observing cows roughly three to four times a day.

If you have any more questions on this subject, you can contact your Select Sires reproductive specialist. They’ll be glad to help. That’s Ray Nebel, extension specialist and professor of reproductive management at Virginia Tech.

Select Sires Inc., 11740 U.S. 42 North, Plain City, Ohio 43064 / Phone: (614) 873-4683 Fax: (614) 873-5751