Recent discussions have downplayed the usefulness of culling records because, it is argued:
Culling is driven by the availability of replacements.
The reason for culling is always low milk production.
However, each cow that is culled or dies because of health problems that led to low milk production constitutes a missed opportunity to cull for genetic potential or to expand the herd. In the real world, herds that improve cow health and use a consistent culling policy end up with lower overall culling rates and larger herds — or heifers to sell if they do not wish to grow herd size.
If animals appear to be leaving your herd too quickly, it’s time to examine why.
Keep them healthy
We work with producers who have death loss rates of less than 3 percent, compared to the national average between 8 percent to 10 percent. And, their culling rates are between 17 percent and 27 percent, compared to the national average of 36 percent to 37 percent. These herds are expanding internally. Improved management, consistent nutrition, good genetics and sound health programs that keep cows healthy lead to better production, not culling.
Think about it. If, during a lactation, 30 percent to 50 percent of cows develop mastitis, 30 percent to 100 percent become lame, and 15 percent to 50 percent have clinical metabolic disease or uterine infections, just how many animals are truly culled because of low production or genetic potential?
Now, some will argue that it’s difficult to predict an animal’s future production potential and, hence, her present value. Making an accurate prediction is often difficult because of the high rate of disease. In our client herds, we have found that if a cow hasn’t had to deal with mastitis, for example, that the production correlation from one lactation to the next more than doubles.
If we keep them healthy, we can more accurately determine which cows and daughters are worth keeping.
Do the math
We all know that most animals with low milk production, or those that breed back late, usually had a health problem first.
Using the statistical calculation called “attributable risk,” with good disease records we can determine what percent of culling and death in the herd is associated with a history of specific diseases. These are the original insults that don’t get recorded as the reason culled unless the loss was sudden and recent. By calculating this number for categories, such as lameness, mastitis, and metabolic or post-partum disease, we can determine how much culling could be reduced through improved health.
For example, one client had a 28 percent total cull and death rate. Using the client’s excellent disease records, we found that half of all culls were due to two causes — mastitis and lameness. The other half of cows culled — 14 percent of the herd — could not be explained by disease history and were true production culls.
Compare this to a herd with a 36 percent culling and 8 percent death loss. Analysis showed that 75 percent of all animals left the herd due to disease. That means just 11 percent of the herd left because they were low production, healthy cows.
Recording disease records in combination with culling rates may have limited value. But by using it to help focus your prevention efforts and track improvement, it becomes a powerful business tool for waste reduction.
Always make individual cow culling decisions based on value, but don’t forget to record and monitor diseases.
Marquerita B. Cattell is a consulting veterinarian in Fort Collins, Colo.