Many ranchers choose to breed the replacement heifers about a month ahead of the mature cows in the herd. In addition, they 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 early 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 call and make arrangements with your local veterinarian to have those heifers evaluated for pregnancy in about 60 days. In two months, experienced technicians should have no difficulty identifying which heifers are pregnant and which heifers are not pregnant (open). Those heifers that are determined to be "open" after this breeding season should be strong candidates for culling. Culling these heifers immediately after pregnancy checking serves three very economically valuable purposes.
1) Identifying and culling open heifers early will remove sub-fertile females from the herd. Lifetime cow studies from Montana indicated that properly developed heifers that were exposed to fertile bulls, but DID NOT become 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 is not 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.
2) Culling open heifers early will reduce summer forage and winter costs. If the rancher waits until next spring to find out which heifers do not calve, the pasture use and winter feed expense will still be lost and there will be no calf to help eventually help pay the bills. This is money that can better be spent in properly feeding cows that are pregnant and will be producing a salable product the following fall.
3) Identifying the open heifers shortly after (60 days) the breeding season is over 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, the heifers that are close to two years of age will suffer a price discount. Currently non-pregnant, yearling 875 pound heifers (shortly after a breeding season) are selling for about $110 per cwt. Therefore an 875 pound, culled replacement heifer is worth about $962.50. Non-pregnant two-year old cows are selling for about $70 per cwt and if they weigh 1000 pounds they are worth about $700 next spring.
The average expense for owning the cow is about $1 per day. Therefore, the total loss of keeping the open heifer would be about $200 in feed and forage and another $262 in lost value. The grand total expense for not culling open replacement heifers in today's market is about $462 per head. Therefore, it is imperative to send heifers to the feedlot while they are young enough to be fed for 4 to 5 months and not be near the "B" maturity age group.
Certainly the percentage of open heifers will vary from ranch to ranch. Do not be concerned, if after a good heifer development program and adequate breeding season, that you find that 10% of the heifers still are not bred. These are the very heifers that you want to identify early and remove from the herd. It just makes good economic sense to identify and cull non-pregnant replacement heifers as soon as possible.
Source: Dr. Les Anderson, Beef Extension Specialist, University of Kentucky