Many Oklahoma ranchers choose to breed their replacement heifers about a month ahead of the mature cows. They also like to use a shortened 45- to 60-day breeding season for the replacement heifers. The next logical step is to determine which of these heifers failed to conceive in their first breeding season. This is more important today than ever before.

As the bulls are being removed from the replacement heifers, this would be an ideal time to make arrangements with your local vet to have those heifers evaluated for pregnancy in about 60 days, says Glenn Selk, Oklahoma State University Extension cattle reproduction specialist. In two months, experienced palpaters should have no difficulty identifying which heifers are pregnant and which heifers are open. Heifers determined to be open after this breeding season should be strong candidates for culling. Culling these heifers immediately after pregnancy checking serves some economically valuable purposes.

Identifying and culling open heifers early will remove sub-fertile females from the herd. Lifetime cow studies from Montana indicate that properly developed heifers exposed to fertile bulls but not becoming pregnant were often sub-fertile compared to the heifers that did conceive. In fact, when the heifers that failed to breed in the first breeding season were followed throughout their lifetimes, they averaged a 55% yearly calf crop. Despite the fact that reproduction isn't a highly heritable trait, it also makes sense to remove this genetic material from the herd so as to not proliferate females that are difficult to get bred.

Culling open heifers early reduces summer forage and winter costs. If the rancher waits until next spring to find out which heifers don't calve, the pasture use and winter feed expense will still be lost and there will be no calf to eventually help pay the bills. This is money better spent in properly feeding cows that are pregnant and will be producing a salable product the following fall.

Identifying the open heifers shortly after the breeding season is over (60 days) will allow for marketing the heifers while still young enough to go to a feedlot and be fed for the Choice beef market. The grading change of several years ago has a great impact on the merchandising of culled replacement heifers. "B" maturity carcasses (those estimated to be 30 months of age or older) are very unlikely to be graded Choice and cannot be graded Select.

As a result, heifers close to two years of age will suffer a price discount. Last week non-pregnant, yearling 875-lb. heifers (shortly after a breeding season) are selling for about $91/cwt. (Oklahoma National Stockyards). Therefore, an 875-lb. culled replacement heifer is worth about $796. Non-pregnant, two-year-old cows are selling for $65 to $70/cwt., while open two-year-old cows (those that could have been identified shortly after the breeding season) that weigh 1,000 lbs. would only sell for about $700 next spring.

The average expense for owning the cow is about $1/day. So the total loss of keeping the open heifer would be about $200 in feed and forage and another $91 in lost value. Thus, the grand total expense for not culling open replacement heifers in today’s market is about $291/head. Therefore, it's imperative to send open cull heifers to the feedlot while they're young enough to be fed for 4-5 months and not be near the "B" maturity age group.

Certainly the percentage of open heifers will vary from ranch to ranch. Don't be concerned if – after a good heifer development program and adequate breeding season – you find 10% of the heifers still are not bred. These are the very heifers you want to identify early and remove from the herd. It just makes good economic business sense to identify and cull non-pregnant replacement heifers as soon as possible.
-- OSU Cow-Calf Corner