During drought, our focus is generally on what we don’t have and can’t do, says Kansas State University livestock specialist Sandy Johnson, PhD. Culling a portion of the cow herd can be necessary and provides an opportunity to reshape the herd. The standard recommendation to begin the process, Johnson says, is to cull the “four Os”: open, old, ornery and odd balls.
Today, culling the open cows can really go far beyond just pregnant and open. Pregnancies as early as 30 days can be identifi ed with ultrasound, and fetal size can be measured to stage pregnancies. Use of ultrasound can also allow gender to be determined, and the optimum time period to target fetal sexing is 60 to 85 days of gestation and no later than 110 days, as the pregnant uterus drops out of reach. Sexing fetuses requires a high level of skill, but Johnson notes increasing numbers of veterinarians have incorporated ultrasound equipment into their practice.
Determining the stage of pregnancies can facilitate the use of culling to tighten the calving season, bringing several advantages. These include heavier and more uniform weaning weights at sale time and more uniform nutritional requirements in the cow herd. Early calvers should rebreed early the following season, and cows with a tight calving season would respond well to synchronization of estrus and artificial insemination, perhaps using sexed semen.
Older cows that can no longer retain body condition or have feet or leg issues would be easy culls. When deeper culling is needed, tooth examinations can help identify older cows, but some type of record on actual age would be valuable if one was forced to make cuts into the middle- aged cows.
Culling the ornery or mean cows should be routine. When deeper cuts are needed, notes or other information on any handling issues or excess nervousness during handling would be useful to include in decisions. Several scoring methods are available to evaluate the disposition of your cows.
“Odd ball” cows may mean different things to different people. It could relate to coat color, calving season, size, body condition, horns or anything that adds unwelcome variation for management or marketing. Culling may allow you to optimize the mature weight of your cows for your production system.
If you have adequate forage this year, it still is a good time to evaluate whether you have the records and information needed to strategically cull cows in a future drought. If you need to make additional culls this year, consider culling strategies that will make management easier.