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What a difference 21 days makes

Most all cattlemen easily understand the direct impact conception rate has on their bottom line. Another measure that can directly affect ranch profitability is calving distribution. While pregnancy checking may give us a good indication of what our conception rate is (number of cows pregnant divided by the number of cows exposed), we will likely need to wait until calving to get a better feel for our calving distribution. 

So, what is “calving distribution”, and why should I be concerned with it? Calving distribution is a look at which cycle of your breeding season each of your calves are born. If you have a 60-day breeding season, you have about three, 21-day cycles, to get your cows bred. If you keep track of the birthdates of your calves, you can then generate the calving distribution of your calves. You can now look at the percentage of your calves that are born in each of the 3 breeding cycles in this 60-day breeding season.  

Why would this matter? Harlan Hughes has put together a graph in Figure 1, showing the relative profitability of when a calf is born within the calving distribution of a herd.

I have heard ranchers tell of herds where 65 percent of the calves are born in the first 21 days, as well as herds where 85 percent of the calves were born in the first 21 days.  It is entirely possible that both of these herds have the same conception rate, yet one is likely to be more profitable. Let’s say both herds are 100 cows and 95 percent of the cows were pregnant. If the ranches were only measuring conception rate, they are likely to be equally happy at this point. Let’s also say 3 percent of the live calves were lost by the time they were weaned. This gives us 92 live calves per herd to sell at weaning.

Will the checks for both herds be the same? Probably not. The second herd has 18 more calves born in the first cycle than the first herd (92 x 65% = 60 calves and 92 x 85% = 78 calves). If those 18 calves gain 2.5 pounds a day for an extra 21 days before they are weaned, they have added 945 pounds more pay weight than the first herd.  That could total over $1,400 more in your paycheck. And that herd probably has calves moving from the third cycle to the second cycle as well. Each cow that conceives a cycle earlier, can add about $78 more to your bottom line. Regardless of when a cow conceives, the cost to carry her for a year will be pretty much the same.  She should just as well conceive earlier, and deliver a heavier calf.

Now, just how do you get a calving distribution more like the second herd than the first?  Nutrition, genetics and management are the tools you have at your disposal. You may still have time to optimize any of these before your 2012 calves are conceived.