Holstein World: What changes have we seen in dairy cow genetics over the years?
Marj & Dick: Data show that today’s cows produce more milk from better udders and stand on a more sound set of feet and legs than cows of even 10 years ago. Also, today’s cows are larger, more angular, and have lower pregnancy rates than cows born in the early 1990s. These same cows now are more likely to be managed in groups, milked in a parlor, and often are housed in freestalls. Some of these changes over the years have been beneficial, some neutral, while others have been less desirable.
In a nutshell, we have changed the cow, changed her environment, changed how she is managed, and further, have changed what we expect from her. These changes have implications for breeding more durable, more long-lived, and more profitable cows for tomorrow.
So, what is the research telling us about today’s Holstein cow? Perceptive breeders will not be surprised to learn (because commercial dairies have been telling us for years) that the genetic makeup associated with longevity is different today than that for Holsteins of 10-15 years ago. Several key changes include:
High yielding cows have only a slight genetic advantage to avoid culling. Ten or so years ago, high yielding cows had a decided genetic advantage for longevity. Given today’s high producing cows and dairies’ needs to control replacement costs, this change probably is not a surprising outcome. The implication is that it is important to focus on traits other than production in order to improve cow longevity.
Cows that are more Dairy (cows which carry less Body Condition) tend to be culled earlier than those which are less angular. This relationship is a striking departure from cows of 15 years ago which showed strong positive associations between longevity and Dairy Form. This finding is supported by US and international research which indicates that more angular cows tend to have poorer fertility and more health problems. To regain some resilience for tomorrow’s commercial cow, we need to breed for cows that are less sharp – in other words, cows that show that they have sufficient body reserves for important functions like the immune system, reproduction, and maintaining a pregnancy.
Large cows (combination of taller cows, with more Strength, more Body Depth, and wider Rumps) are culled earlier than more moderately sized cows as evidenced by negative correlations today between Productive Life (PL) and the body size traits – Stature, Body Depth, Strength, and Thurl Width which tend to track together (these trait are correlated) and as such, ultimately define the size of cows. This result of earlier culling for large cows agrees with comments we hear from commercial dairies who say that they need more moderately sized cows and further, should not be surprising given that today’s cows are more than 0.5 standard deviation larger than cows born in 1985.
Holstein World: How has the shift in breeding for health traits also affected your contracting and sire selection?
Marj & Dick: Significantly. The equations that measure and illustrate the economic advantages of healthy, fertile, longer-lasting cows in today’s dairy economy are sound and realistic.
The three most significant costs in producing replacement cattle are facilities, feed and labor. We know that the cost of each of these three components edge up each year and therefore the cost of replacing cows in the herd goes up each year. Economic stability for dairy farm families is dependent upon the difference between a cow’s lifetime marginal return and the cost to replace her.
We also know that that pregnancy status and cell count are the two primary factors that determine voluntary culling in dairy herds. Therefore as genetic evaluations for additional health and fertility traits have become available and the accuracy of exiting trait evaluations have been improved, these traits have become increasingly more important in our sire selection processes.
Dairy farm families that milk Holstein cows have every reason to expect that these genetic deficiencies in the breed be addressed. They should expect genetic improvement and genetic progress for health, reproductive and longevity traits. We have taken the steps necessary to assure genetic progress in these traits.