“The key to culling is determining at what point the cow’s production potential has dropped enough to warrant replacement,” says Jeff Bewley, a dairy Extension specialist with the University of Kentucky. “In short, a cow should be culled when higher profits are expected from her replacement.”
That, of course, is easier said than done, Bewley acknowledges. “The expected future profits from the current cow depends on many things including the cow’s age, production, days in milk, reproductive status, previous and current diseases, and so on,” he says. “On top of that, estimating the future profits and lifespan of her replacement makes the task twice as difficult.”
To make the job a little easier, Bewley and colleague Karmella Dolecheck offer four tips:
• Know your target herd size: Being aware of your current and target herd size in the future will dictate “if, when and how many cows to cull,” they say.
•Be aware of replacement availability: Consider not only the number of replacement heifers you have but their quality. “In most cases, the best genetics on the farm are in your heifers. Therefore, it’s important to realize that you are not replacing a cull cow with an identical animal but actually a genetically superior animal.”
• Cow ranking. Use software programs that will rank your cows based on their potential profitability. For example, the CowVal option in DairyComp ranks cows according to their value before and after becoming pregnant. Looking at these values, you may not even want to breed an older cow if her “after-pregnancy” value is lower than an incoming replacement. Factors such as temperament or dominance also come into play.
• Good records. Having good records on production and reproduction are essential in ranking cows and determining culling status. But don’t forget disease records such as the number of times cows have been treated for mastitis or lameness.
In the end, Bewley and Dolecheck say culling decisions are not only science, but art. Perfect prediction is not possible, they say, but having records as complete as possible helps in artful culling decisions.
Note: This story appears in the June 2017 issue of Dairy Herd Management.