Developing replacement heifers affected by herd size, pasture and goals

Beef cow-calf producers need to put replacement heifers back into their herds each year according to Eldon Cole, livestock specialist with University of Missouri Extension.

“If they wish to maintain their herd size, it typically requires 15 to 20 percent of their existing cow herd to be replenished annually,” said Cole.

Replacements may be home-raised or purchased.

“There is debate over whether buying a bred heifer or an open heifer or raising your own is the economical way to go. A lot depends on whether you feel your herd needs significant genetic improvement,” said Cole. “If that is the case, buying better genetics makes sense.”

Herd size can help in making the decision. Small herds—those under 25 to 50 cows—will probably find keeping only seven or eight weaned heifers a nuisance.

According to Cole, the weaned heifers will need a separate pasture until breeding season. Producers may need to buy a different bull or plan to breed them artificially. As they develop, it is also desirable to keep them away from the mature cows.

“So you can tell with that example, the decision to buy or raise heifers is not always a clear straight-forward decision,” said Cole.

Show-Me Select protocols

Regardless of the heifer’s source, Cole suggests that producers follow the lead successfully used for 20 years with the Missouri Show-Me-Select protocol.

Here are key points of that program.

Select heifers that were calved early in the calving season.

“So far as possible, involve genetics in guiding your heifer selection. Consider expected progeny differences for maternal traits and genomic panel data,” said Cole.

Have a veterinarian who is comfortable with reproductive tract scoring and pelvic measuring, examine the heifer 4 to 6 weeks ahead of the breeding season. The scoring system, 1 to 5 indicates their nearness to being ready to breed. A 1 score is very immature and they are poor replacement candidates and should be culled. A 2 is normally culled too. Three’s have not cycled yet but otherwise are suitable. They may require a bit more feed before breeding. Any 4s and 5s have had at least one heat period. “The SMS goal is to have at least 50 percent of the heifers score 4 or 5 for best early conception rate,” said Cole.

Pelvic size should be 150 square centimeters. If they are close, 140 square cm or so, SMS allows them to be remeasured at the first pregnancy check at which time the pelvic measurement must be 180 square cm.

The SMS program encourages participant to use artificial insemination following an estrus synchronization protocol. Most use a fixed time AI breeding followed with a cleanup bull or bulls turned with the heifers in 14 days.

Restrict the breeding season. Some hold it to 45 days, which gives heifers three opportunities to breed. “Others find a 90-day season works better but it does string out the calf crop. Regardless of the length most producers favor heifers that settle on the first service,” said Cole.

Before 90 days following AI or bull turn-in, have a veterinarian pregnancy check the heifers. Most veterinarian’s use ultrasound to estimate fetal age. Non-pregnant heifers should be sold as feeders.

More details on the Show-Me-Select Replacement Heifer’s requirements are outlined at http://agebb.missouri.edu/select/.