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What does your calving distribution look like?

Jordan Thomas for Progressive Cattleman Published on 29 January 2019
calves and cows in green pasture

For most spring-calving beef producers, your herd is either calving now or will start to calve soon. Hopefully this article catches you before calving starts so you actually have time to read it – I know how busy this time of year can be. But as your calves start to come, I want you to have a metric in the back of your mind: calving distribution.

All beef producers are well acquainted with the term “calving season.” About every decade, the USDA National Animal Health Monitoring System conducts a survey of production practices used in the cow-calf industry. We are awaiting the 2017-18 survey results, but I will say there were some statistics in the 2007-08 results that I found particularly disappointing. Here’s one: 46.1 percent of beef cow-calf operations had year-round calving seasons. Now, I’m not sure where you live, but here in Missouri, I’ve never encountered any “season” that lasts the whole year. But that is another conversation for another time. There were a few bright spots in the data: Larger producers, for example, were much more likely to have defined calving seasons.

I suspect that as readers of this publication and as progressive cattle producers, most of you have defined calving seasons. Let’s say you calve over a 60-day period. There are mainly two approaches to make sure the length of your calving season stays 60 days: either you limit the length of your breeding season to 60 days or you use a longer breeding season but cull cows that become pregnant after day 60 of the breeding season. As long as you are committed to actually culling open or late-bred cows, either option works.

But here is what I challenge you to think about as your cows calve out this year: What total proportion of your cows have calved by each day of the calving season? Specifically, what percentage of your cows have calved in the first 21 days? What total percentage has calved by day 42? If you haven’t looked at this before, look at it this year as your herd calves out. Dig into your numbers. Break those percentages down by age group. Get creative. Even if you don’t find major, glaring problems, I guarantee you will find some areas for potential improvement.

Now what can you actually do about it in the next breeding season? As you probably expect, I am a huge proponent of estrus synchronization and artificial insemination for the commercial cow-calf producer. It’s not a cure-all; you still can’t starve your cows, and your cows still need to work in your environment. But if you are not taking advantage of reproductive technologies, you are simply leaving money on the table. Why? Even if you ignore the improvements in genetic merit, using estrus synchronization and A.I. at the start of the breeding season functionally shifts your calving distribution earlier than using natural service alone. You get more cows pregnant early in the breeding season, and that is one of the biggest drivers of profitability there is in the cow-calf world.

What proportion of your females can become pregnant to timed A.I. on day zero of the breeding season? Depending on whether we are talking about heifers or cows, I usually say about 50 to 60 percent. Don’t trust the research? Think that’s an exaggeration? Let’s look at some real-world numbers. In our statewide Missouri Show-Me-Select Replacement Heifer Program, we have field data from producer herds all across the state. Over 37,000 heifers in this program have received timed A.I. after estrus synchronization with the 14-d CIDR-PG protocol. The real-world average pregnancy rate? Fifty percent. A few years ago, the University of Missouri collected similar field data for mature cows using the 7-d CO-Synch + CIDR protocol in a large series of field demonstrations. There were over 7,000 cows across 73 cow herds in those demonstrations on commercial farms and ranches. Across all of those herds, pregnancy rate to the timed A.I. averaged 63 percent. Timed A.I. works.

Think of what using timed A.I. does to your calving distribution then. If you get 50 to 60 percent of your cows to conceive to A.I. on day zero of the breeding season before turning out bulls, that leaves only 40 to 50 percent of your cows that the bulls need to settle. When using timed A.I., we also give all of the cows an opportunity to conceive on day zero of the breeding season. If they fail to become pregnant, they have another opportunity when they cycle back around day 21. See what that means? In the first 21 days, the cows have had not one but two opportunities to become pregnant. In a natural service system, cows only have one chance to conceive in the first 21 days of the breeding season. And that’s assuming cows are cycling at the start of the breeding season – not all cows are. When using timed-A.I. protocols, we induce a large proportion of the anestrous cows to start cycling. That is a tremendous advantage when trying to get late-calving cows moved up.

The net impact of all of these benefits is simple: You get more early born calves. More early born calves means heavier average weaning weights for your steers. It means more early born heifer calves to retain as replacements. It means more time after calving for cows to start cycling again before the start of the next breeding season. It means more dollars in your pocket. What does your calving distribution look like?  end mark

Watch the video below for an explanation on calving distribution and timed A.I., including charts and examples.

Jordan Thomas
  • Jordan Thomas

  • Assistant Extension Professor and State Beef Reproduction Specialist
  • University of Missouri – Division of Animal Science
  • Email Jordan Thomas

PHOTO: No season lasts all year long and neither should calving season. Photo provided by Jordan Thomas.