As bulls are being removed from the replacement heifers it's an ideal time to make arrangements with your local veterinarian to have those heifers evaluated for pregnancy after another 60 days.
Two months after the breeding season experienced palpaters should have no difficulty identifying which heifers are pregnant and which heifers are not pregnant, says Glenn Selk, Oklahoma State University emeritus animal scientist
Heifers determined to be "open" at that time should be strong candidates for culling, he says.
Culling open heifers immediately after pregnancy checking serves three purposes.
1. It will remove sub-fertile females from the herd. Lifetime cow studies were conducted at a USDA experiment station in Montana. Throughout 23 years, 1,589 replacement heifers were exposed to bulls. Of those, 266 heifers were found to be open after their first breeding season.
All these open heifers were then kept in the herd for an average of four years. From the 1,006 "cow years" that followed, only 551 calves were produced. In other words, when the heifers that failed to breed in the first breeding season were followed throughout their lifetimes, they averaged a 54.9% yearly calf crop. Despite the fact 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. It will reduce production costs. If you wait until next spring to find out which heifers do not calve, the winter feed expense will still be lost and there will be no calf to help pay the bills. This is money which can be better spent in properly feeding cows that are pregnant and will be producing a salable product at weaning time.
3. It also allows you to market those open heifers while they are still young enough to go to a feedlot and be fed for the Choice beef market. The grading change of several years ago had a great impact on the merchandising of culled replacement heifers. "B" maturity carcasses, which are those estimated to be 30 months of age or older, are much less likely to be graded Choice and often cannot be exported. Early culling, on the other hand, lets heifers go to the feedlot while they are young enough to be fed for four to five months and not be near the "B" maturity age group.
The percentage of open heifers will vary from ranch to ranch, Selk says.
"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," he says. "These are the very heifers that you want to identify early and remove from the herd."
If you are shopping for replacement heifers at sale, buyer beware! Selk adds.
Be wary of heifers which were exposed to bulls or artificial insemination/clean-up bulls and remain non-pregnant. This is the easiest opportunity to become pregnant they will have. If they are still open after that first breeding season they may be infertile, at worst, or sub-fertile compared to other heifers.
Remember the old Montana data that suggests that they will be 55% calf crop females the rest of their lives.