How long a cow should remain in a milking herd is a tricky question without a straightforward answer. Some people will argue that increased herd longevity is a good thing. Nigel Cook from the University of Wisconsin outlines how this argument has been presented to him:
“People think longer lives result from healthier cows and that reflects better animal welfare, decreased environmental footprint (raising fewer replacements can decrease our methane emissions per pound of milk), and we can improve our economics because we’re keeping cows longer,” he says.
However, if you look a little deeper, this reasoning may be flawed. When comparing real herds, there are a variety of situations that may explain why there is no one-size-fits-all for turnover rates in a dairy.
“There are herds with lower turnover rates, with great welfare and excellent health. They sell heifers or build another barn, they expand. But there are also herds with lower turnover rates that have low turnover rates because they have to keep cows. Those cows may be high somatic cell count cows, mastitic cows or lame cows, and that impacts their overall performance and fertility,” Cook explains.
On the other hand, high turnover rates can also reflect good herd management.
“There are herds with high turnover rates that can support those rates because of good health and good fertility. They have the replacement supply they need to do it,” Cook continues.
Avoid Hasty Culling Choices
In the U.S, the average time for a dairy cow to remain in the herd is 2.5 lactations. Over the past 10 years, many improvements have been made in dairy herds: cattle are producing more milk with improved component contents, fertility rates are up and somatic cell counts are down. Despite these changes, herd turnover rates have remained fairly constant. Cook proposes this is because producers follow breeding, and not necessarily culling.
“The process of culling is enormously variable,” Cook says. “Few farms use relatively well organized, high quality summaries of data to help them select cows early enough in lactation to decide which cow leaves.”
Cook highlights how a lot of farms put too much focus on the cow’s immediate production history instead of their lifetime production.
“They have a heifer, they have a slot. They’re just making that decision that day without a lot of prior planning. I wish we could change that,” he says.
This can lead to hasty cull decisions that may not be the best move for the herd overall. This was confirmed in an unpublished survey of over 60 Wisconsin dairy herds. Cook and colleagues found that 29% of cows culled for production reasons were better performers than half of the cows in their own herds.
“We should be holding our farms accountable to the quality of the cows leaving the herd, not the quantity,” Cook says.
The Economics of Culling Decisions
Mike Overton, global dairy platform lead for Zoetis, suggests letting herd economics be a driving factor when making the decision to cull and selecting cull cows.
“When we look at [culling decisions], we’re trying to replace an inferior cow, and that represents an opportunity to improve the herd,” Overton says. “It comes down to timing. We do it too late, we cost the herd money. If we do it prematurely, we cost the herd money.”
Consider the predicted value of the incoming and potential cull animals. If you replaced that animal, what would the improvement in milk production be? How about the improvement in herd genetics? One additional consideration is the revenue for the current cow when she leaves.
“When you have a heifer calving into a herd and her predicted value is greater than the lowest value cow in the herd, replace that cow. If not, that heifer should go elsewhere,” Overton says.
While Overton advocates for more aggressive replacement strategies, he says he is often countered with the idea of whether the departing cow has ‘paid for herself’.
“The decision to replace the cow should never account for when she’s paid for herself. That’s flawed logic,” Overton says. “This line of thinking might work for your average and above average animals, but your lower producing cows, the ones you should be culling sooner, will end up staying in the herd longest.”
Also consider older cows have a higher risk of health complications, as well as a lower market value per pound at slaughter. The salvage value of a cow should play into your culling decisions.
“Most people assume a low replacement rate equals greater profitability,” Overton explains. “It would be true all things being equal. If you think about if all cows were healthy and equal in production and market value, and the only reason for replacement was mortality, a lower replacement rate is going to be better. But we also know that cows are not equal in value or productivity.”
It’s possible to fall into the trap of trying to hit longevity, productivity or replacement rate benchmarks; however, these may cause lower performing cows to be kept for longer. Cull decisions should be well informed and tailored to each herd.
“Don’t be afraid to replace poor producing animals, even first lactation animals, if you’ve got heifers available to take their place. Never restrict replacement just to try and hit a benchmark,” Overton says.
