I have been using artificial insemination (AI) across my cows for 16 years and until this year I have been using the am/pm rule.

This means that if a cow was in heat in the morning I would inseminate her in the evening and if she was in heat in the evening then I would leave her until the next morning.

I have to say that this system has always worked well and I was very happy with my conception rates.

You would think I should have been content, but I’m always wondering if there is some better way of doing things.

So, after listening to other advice, I decided to change and this year I went to inseminating the cows once a day, and as for timing, it was just whenever I had an opportunity during the day.

This meant that some cows were done 12 hours after the onset of heat and others were done 24 hours after the onset of heat. There were even times when it was 36 hours after I first saw the cow bulling.

To be honest, I was quite surprised that my new regime seems to have made absolutely no difference to conception rates. They are the same this year as every other year.

I know this is not a very technical or scientifically robust experiment, but it has certainly opened my eyes.

Theories

When I travel around the country inseminating cows for other farmers, some of the theories I hear are extraordinary.

Some farmers think that the cow should be inseminated when she is in heat (the same timing as the bull). They cannot understand that there is no need for this. When I arrive in the yard they will tell me that I’m too late as she is off heat. Some ask, when I put my hand inside the cow, is she still in heat.

Others (when they call me) will say that they don’t know whether she is coming on or going off heat. I try to tell them that it doesn’t matter and explain that far more cows are done too early rather than too late. Quite often I get the impression that they just don’t believe what I am saying.

It’s a long time since the reproductive system of cows was explained to me. The way that I remember it was that a cow ovulates around 36 hours after the onset of heat. In other words, the egg cannot be fertilised until at least 36 hours after the cow first stands to be mounted.

So if you decide to inseminate a cow at the start of heat, then the semen has to survive and wait for 36 hours on the egg to arrive on the scene. Given that thawed semen only lives for about 36 hours after being handled, then the chances of getting a calf are slim.

If you happen to be using sexed semen, the chances are even lower as it only survives for around 24 hours after being thawed.

Blame

It’s very easy to blame other things for a cow not holding and I’m quite sure that I get accused lots of times, but I would never accept that it was because I was too late turning up to AI the cow.

I am convinced that there is a good window for getting cows in-calf (at least a 24-hour window). If you AI your own cows don’t be in any rush and if you use an AI technician, then ring early and tell them you are not in any great panic. As my sons are always reminding me: “Have a little bit of patience.”