Transcript of Select Sires' Reproductive Moment Program
on DairyLine Radio Which Aired Dec. 14, 2006
With Ray Nebel,
Senior Reproduction and Herd Management Specialist, Select Sires Inc.

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 heat in the morning, then you breed them in the afternoon, and if you see that at 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 and if we only check cows for heat then the AM-PM rule was established with three-times-a-day heat detection. If we catch a cow in heat this morning then she wasn’t in heat yesterday afternoon when we checked, and if we didn’t see her this morning but catch her this afternoon it says when we went out this morning she wasn’t in heat but she is in heat this afternoon. The more often we go out and visually observe cows, the better we can do the job of timing when insemination can occur. The biological events that can determine conception are the life of the sperm or life of an egg - the life of the egg is much shorter than the life of the sperm. The life of the egg is roughly 8-12 hours, the life of the sperm in a female reproductive tract in a cow is roughly 24-36 hours; so we would like to have the sperm into the site of fertilization waiting for the egg because it has a much longer lifespan. So the old adage of the AM-PM rule 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. Again, because we can’t time when that heat actually started; if we observe cows only once a day we need to do it as soon as possible after observation. All it says, if we observe her now is she wasn’t in heat yesterday at this same time, so somewhere in the last 24 hours. We need to put semen in her as soon as possible. Again timing of the insemination should be based on the heat detection program. 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 specialists; they’ll be glad to help. Thank you, Ray. That’s Ray Nebel, senior reproduction and dairy herd management specialist for Select Sires.