With calving season upon us, I hope you're recording your calves' birth dates and their dam numbers in a calving book. If so, all you need to generate a Herd Calving Distribution Table (HCDT) is each calf's weaning weight.

These three pieces of data can help you tweak management and convert 2005's missed profit opportunities into next year's added profit opportunities for your cow herd.

My Integrated Resource Management (IRM) work suggests per cow profit within a beef cow herd varies cow to cow depending on when a cow calves within the herd's calving distribution. Figure 1 presents the profit index by 21-day calving interval for my demonstration herd. The most profitable cows calve in either the first or second 21-day calving intervals.

Clearly, there's an economic incentive to manage a herd's females so more of them calve in the first two calving intervals. In my February column, I described how your pocket calving book data can help you measure and manage the 21-day calving distribution of your cow herd. The article focused on missed profit opportunities typically found in IRM herds I've analyzed.

Last month's column focused on the age distribution component of an HCDT. I suggested the age distribution of females in your beef cow herd tends to impact the herd's generated gross income. A herd's overall economic performance is highest when most females are in the 4- to 6-year-old category. Older or younger cows pull down a herd's overall performance.

My demonstration herd had 55% of its females in Group 1 (2-4 years old), 22% in Group 2 (5-7 years old), and 23% in Group 3 (8 years and older). While the cow herd's average age was 5.1 years, this manager had a majority of his herd falling outside the highly productive middle-aged group.

Managing 2-year-old heifers

Several ranchers have told me that once they solved their replacement heifer problems, most of their herd's other problems went away. They say good mature cows tend to take care of themselves and have a calf every 365 days.

I believe there's a lot of truth in these statements. Let's look at how one might intensify heifer replacement management.

If you're going to measure the calving interval of both replacement heifers and mature cows, when do you start the counter? The Beef Improvement Federation (BIF) guidelines suggest starting when the third mature cow (3 years and older) calves.

BIF guidelines also suggest all heifers be calved ahead of the mature cows, a recommendation I agree with.

In this example herd, eight heifers calved early, followed by the third mature cow, which started the 21-day counter. The remaining 74% of this rancher's 2-year-old heifers were in the first through fourth calving intervals. This rancher pretty well missed the “calve heifers early” rule.

Why should heifers be calved ahead of mature cows? It's quite common for 2-year olds to have a calving interval greater than 365 days when calving as 3-year olds. If not calved early as 2-year olds, heifers are much more likely to be culled early in life as late breeders. Early calving allows 2-year-old heifers to fall within the first calving interval as 3-year olds.

The last thing you want is to bring in an expensive replacement heifer only to have her culled early in life due to late breeding as a 3- or 4-year old. This is a real missed profit opportunity.

Being open as a 3-year old is an even bigger missed profit opportunity. Culling heifers as 3- or 4-year olds increases a herd's unit cost of producing a cwt. of calf. Whether raised or purchased, the negative economic impact is a large missed profit opportunity.

If a scan of your HCDT shows a particular year's females moving down the table and to the right, as Figure 3 suggests (yellow lines), it indicates their calving interval is more than 365 days. This isn't uncommon, but it represents another missed profit opportunity as it implies these cows are destined for early culling as late breeders. Culling late breeders and replacing them with bred heifers adds substantially to a herd's production costs.

Can a rancher move breeding dates up to nudge the arrows down and to the left? In other words, can females be managed to a calving interval of less than 365 days? Yes, but it takes a lot of high-quality feed, tender loving care and added economic cost.

Harlan Hughes is a North Dakota State University professor emeritus. He lives in Laramie, WY. Reach him at 701/238-9607 or harlan.hughes@gte.net.