In the last post about our pregnancy tests and results, I mentioned that we determined pregnancies, or lack-there-of, by observing heats. It occurred to me that not everyone reading probably knows what a heat means, or might not know what the signs of a heat are. This thought was confirmed by a question from a close friend with no agricultural background. So, I’ll offer my non-technical explanation.

Cows have a reproductive cycle just like people. When a cow is able to get pregnant, we say she is “in heat”. When a cow is coming into heat, she will just generally act different. Often, she will rest her head on another cow, or she might stand away from the rest of the herd mooing about nothing. There are also some subtle signs like a rise in body temperature and a higher activity level. The most noticeable and definite sign of a heat is mounting, or even more-so, being mounted.

I like to think that cows were created with technology like AI in mind. With no males present, females will mount other females that are in heat in the same manor that a bull would mount a cow to breed her. When a cow will stand and allow another cow to mount her for several seconds, we call it “standing heat”. We try to breed the cow 12 hours after we observe standing heat. The cow doing the mounting is not always in heat, but it’s always wise to watch cows that are hanging out together when one is in heat because the other(s) may either also be in heat or be coming into heat soon.

We have a pretty good heat detection rate by just observing our cows because David does the majority of the milking. He also usually takes a few minutes in the morning and afternoon to just watch. In addition, we don’t have so many cows that he has trouble identifying which cows are showing the signs mentioned above. If he does miss actually observing standing heat, he might notice signs on the cows back end while she is milking that indicate she has been mounted many times.

For those that don’t feel that observation is adequate for heat detection, there are other options. There are many products on the market that indicate heats. One type has a colored liquid in it and bursts if/when a cow is mounted leaving the color on her tail head. Another type puts a colored substance on the cow’s tail head that is smeared around if/when she is mounted. Some milk meters (a tool that we do not currently have in our milk barn) take the temperature of the milk and can identify a higher milk temperature as a likely heat, and some farmers use pedometers to observe when a cow takes an unusually high number of steps in a day. There are probably other methods of heat detection that I’m not familiar with (or didn’t think of as I was writing this), but these, I think, are the most common.

This may seem like too much information, but I felt it was worth explaining because heat detection is a huge part of dairy farming. Without accurate heat detection we miss opportunities to get our cows bred. It will be roughly 21 days before we get another opportunity to notice her heat and breed her. The longer it takes to get our cows bred, the slower our herd improvement will be. Also, if we don’t get a cow bred back quickly, her milk production will likely reduce before she is ready to have another calf. A high number of days open (not bred) is costly, so getting cows bred is a top priority for all dairymen, and that starts with heat detection.