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Mother Nature favours June, but late April is best (so far) for rotational grazing

There is a never-ending debate on when is the best time to calve. You have four choices; spring, summer, fall or winter. The only thing that will tell you when the best time to calve for your operation is a gross margin analysis. The numbers will tell you. If you don’t know your margins, then you are just guessing. I do not waste my time in these debates.

I tried three different seasons before I found the right one for me. Yes, I guess I have one more to try, but for now I am happy.

I of course started calving in the winter because that is what I was told to do. I soon learned that that was not for me. Too cold and too much labour! Calves are born with a summer hair coat and I like to get a full night’s rest. No thank you!

I then looked into the economics behind the calving period. If you compare the biological time period of a cow’s gestation and the seasonal time period of one year of our Alberta climate, it was an easy decision for me. The biological time periods would be the first, second, third trimesters and her return to estrus.

The most expensive time seasonally to feed our herds is the winter. They require more energy to keep warm than the other three seasons.

Biologically, the cow requires the least amount of nutrition in the second trimester. A 1,200-pound cow in her second trimester only requires an ME of 16.6 Mcal and 6.9 per cent protein daily. This does need to be adjusted for the weather but overall she will require less feed here than during the other three time periods. She is not milking and only carries a small fetus.

If you use a gestation wheel and line up the second trimester with the winter season, (December 21 to March 31) that places calving time about June 21. This also corresponds to Mother Nature as most of the wildlife seems to prefer this time period for a birthing season. It is Mother Nature’s design to have the animals store fat thoughout the spring, summer and fall. This allows them to stick it out for the winter with a lower-quality feed that is not very plentiful. Some of their energy requirements for the winter are stored on their backs. In the spring they get to feast on some very lush forage again which allows them to start putting on weight before giving birth in late June or early July. Haven’t we always been told that the cow needs to be gaining weight prior to calving? The highest nutritional requirement of a cow is at calving time which also makes sense to line this up with summer.

So that’s what I did. I moved calving to June 21, which also happens to be the longest day of the year. One other correlation with this date is the fact that many animals, including cows, are photosensitive. This means

they are day-length sensitive when it comes to their estrus cycle. A cow will return to estrus faster, the closer she calves to the longest day of the year. This means that she will have a better chance at rebreeding if she is able to have three or four cycles before being exposed to a bull again.

With all these factors in front of me, it was not hard for me to decide that summer calving was for me. I tried it for three years. I ran across one problem. The calving season did not match my grazing techniques. I had a fair amount of difficulty with the stress levels of the cows and calves during late June and early July due to my grazing rotation. I move the herd quite often as I am managing for the land and it had a negative impact on the herd.

I was losing newborn calves when I moved paddocks. The moms would up and leave them behind or the calves would wonder off and hide in the long grass. No matter how gentle I tried to herd the animals, calves were always missing. They would be hiding in the trees or in a different paddock. I also ran over a couple calves because I could not see them sleeping in the tall July grass. I was forever trying to find lost calves and matching up cows and calves.

Some of you summer calvers will argue this point, I know, but not all pastures are set up in open fields and easy moves. I have some pastures where summer calving was not a problem, but most of my pastures have a high percentage of bush and paddocks that are not always side by side.

The size of the herd impacts this as well. If a baby calf gets separated from its mom during a move, it takes less time and is less stressful to only have 50 legs to sniff compared to 400. If that calf is stressed every day and possibly misses one milking a day because of everyday moves, what do you think the weaning weights are going to look like?

I also had some difficulty with sick calves in the summer. In the heat, they dehydrate quickly if they get sick. I am pretty particular about the pasture management but I also did not want the negative consequences for the herd. So I made an adjustment.

April 25 is my target now, to finish hopefully by June 21. I still believe in all the arguments for summer calving but I have lined up my calving season with my grazing season. I still have many of the summer calving benefits and this makes a much easier calving time for me. I stockpile grass for calving in May and supplement feed on these pastures with bale grazing. This allows me to maintain the herd in relative proximity to a facility for a longer period of time. I do slowly rotate the calving herd, only enough to keep the ground clean. I check twice a day and tag and castrate calves as soon as I can. They are much easier to catch before they are six hours old. As I am a custom operator, there are still certain requirements that my customers ask me to provide.

As the pasture starts to grow, I can start to send pairs out to match the grass. I usually begin my grazing season around May 10 so by this time I have a good number of healthy pairs to hit pasture. This allows me to match the carrying capacity of the early paddocks with an appropriate stocking rate. As the grass starts to jump during May, I continue to add pairs to the paddocks in rotation. As long as the calves are a few days old, they can keep up with mom no problem with my low-stress grazing rotation.

Each paddock the grazing herd moves into has more carrying capacity than the last one, so I simply add more pairs to it every few days. If they have not calved by June 15, they are on their own. The whole herd is grazing by then.

Sorting is easy when you have a calf cart that pulls behind the quad. When you catch the calf to tag it, you place it in the standup cart, and drive to a separate paddock for pairs. Ninetyfive per cent of the time, mom just follows you out the gate.

No system is perfect but this one seems to work for me. Once in awhile I will get those late-April rain or snowstorms that cause me some grief, but I seem to get through them without too many losses. I have very little calving difficulty with May calving and I quite enjoy being out there in the spring.

This is what seems to work on my operation. What works for me might not work for you, but maybe you picked one thing up from this article that will help your calving season run a little smoother. Best wishes!

Steve Kenyon runs Greener Pastures Grazing Management in Busby, Alta.,,(780) 307-6500, email[email protected]

About the author


Steve Kenyon runs Greener Pastures Ranching Ltd. in Busby, Alta. You can email him at [email protected] or call 780-307-6500.

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