How do you catch something that only lasts 2 to 4 seconds? It's not easy. But, this short window just happens to be the time it takes a herdmate to mount a cow in estrus.

Although producers, on average, miss 50 percent of heats, you shouldn't throw away your AI sleeve just yet. With a little refresher course, you and your employees can boost your heat detection skills and catch the cow that managed to sneak by the sleeve 18 to 24 days ago.

Check more often
Checking for heat while you are walking to the house for breakfast or driving by on a tractor isn't the best time to catch a cow mounting another cow. Instead, you need to take some time to observe the cows at least two times per day, at evenly-spaced intervals such as 7 a.m. and 7 p.m., says Paul Fricke, extension specialist in dairy reproduction at the University of Wisconsin-Madison.
And, checking for heat doesn't mean a quick walk through the freestalls, either. You need to stop whatever activity you're doing and just watch the cows for a set time period of 15, 20, or 30 minutes.
A recent Virginia Tech study noted that 25 percent of heats are less than 8 hours long. So, if you observe cows at 7 a.m. and 7 p.m., you could easily miss a cow who exhibits estrus activity between 9 a.m. and 5 p.m. Therefore, observe cows more frequently throughout the day, for set time periods. For example, if you check four times a day, watch the cows at least 15 minutes each time.

It makes economic sense to watch cows for signs of heat. (See sidebar, "Economics of heat detection.") So, if you haven't got the time, delegate the task to an employee.

Right time, right place
If you're watching for heat when cows are eating or milking, you probably won't see it. Instead, if you want to watch for heat, get the cows moving and intermingling, says Ray Nebel, extension dairy scientist at Virginia Tech. Watching cows when they are walking to and from the parlor provides a good opportunity because it forces the cows to focus on each other rather than milking or eating. However, don't watch for cows in heat while they wait in the holding pen because they don't have enough room to interact in this situation.

In addition to watching cows at the right time, watch them in the right places. Cows prefer to mount on dirt rather than concrete. In a study published in 1986 in the Journal of Dairy Science, researchers at North Carolina State University found that the heat detection rate on dirt was 91.3 percent, compared to 76.8 percent for cows on concrete. This same study also found that cows on dirt remained in estrus 13.8 hours versus 9.4 hours for cows on concrete.

To increase the heat detection rate when cows don't have access to dirt lots, provide them with a comfortable environment to prevent lameness. For example, trim hooves annually to prevent sore feet and give them ample space in the free-stall area so they can interact without obstacles. In addition, groove concrete in a diamond or square pattern to improve traction for cows desiring to mount or provide rubber belting in high traffic areas. (For more information on hoof trimming, purchase "Cattle Footcare and Claw Trimming."The book's cost is $37.45 with shipping. Contact Farming Press Books at (800) 481-1353 to order.)

Watch for these signs
With 80 to 90 percent of dairy cows cycling normally in a herd, don't push the blame of poor reproductive efficiency on the cows. A person's failure to notice the signs of a cow in heat remains the major cause of poor reproductive efficiency.
"Knowing the visual signs is very important for the people detecting estrus," Fricke says. In light of this, you can be 95 percent sure a cow is in heat if she stands solidly to be mounted by a herdmate.

Of course, as many as 15 percent of cows exhibit silent heats, so you won't be able to see signs of heat from every cow. And, if only a few cows exhibit heat at the same time, the above signs may not be as obvious, either.

In addition to properly identifying the signs of a cow in heat, observing cows more often for longer time periods allows you to catch cows in heat and get them bred faster. n

Remind yourself and your employees to watch for these signs of heat

  • A restless cow with a rubbed tailhead and clear mucus discharge from a swollen vulva.
  • A cow resting her chin on the back of another cow.
  • Cows exhibiting mounting activity.
  • Cows forcing their heads together.

Economics of heat detection

It pays to improve your heat detection efficiency, or the percent of cycling cows you breed every 18 to 24 days. If you breed 50 cows out of 100 cows that are cycling, your heat detection rate is 50 percent, well below the recommended efficiency of 70 percent to 80 percent, says Paul Fricke, extension specialist in dairy reproduction at the University of Wisconsin.

According to an October 1981 article in the Journal of Dairy Science, increasing your heat detection efficiency from 35 percent to 55 percent reduces the average days open from 136 to 119 days, with a net return of $60 per cow.

In addition, a Virginia Tech study published in the October 1994 issue of the Journal of Dairy Science points out that improving your heat detection efficiency from 20 percent to 30 percent, with an AI conception rate of 50 percent, results in an economic benefit of $83 per cow per year.