Historically, to a lot of dairymen, calving ease has been a bit of a secondary trait. In many cases semen buying decisions were more centered on how much production or how much type a sire had. Calving ease was thrown into the mix almost as an afterthought, or as something to use on the heifers. However, the most stressful part of a cow’s life cycle is the calving process and its postpartum aftermath. The quality of life of a dairyman might increase dramatically if we could eliminate difficult calvings, retained placentas, ketosis, milk fever, displaced abomasums, etc. There would probably be a little less concern over the diminishing availability of large animal veterinarians if these ailments could be eliminated.

The problem is calving is needed to create peak milk production (provided the previously listed ailments are avoided) and future replacement animals for the herd. Since the advent of the Lifetime Net Merit $ (LNM$) system in 1994, we have been providing the general public with a continuous stream of new traits: LNM$, Cheese Merit $, Fluid Merit $, Productive Life, Somatic Cell Score and Daughter Pregnancy Rate, just to name a few.

Contrary to how you may feel, these new traits were not solely designed to confuse you; they have proven quite helpful in figuring out what makes a cow last. Our measurement of the calving process has now also evolved. Previously our only measure was calving ease or the ability of a sire to make a calf that is born easily. This has now expanded into four areas:

•sire calving ease

•daughter calving ease

•sire stillbirths

•daughter stillbirths

Sire calving ease (SCE) is the original calving ease trait, and it has not changed. It is the ability of a sire to make a calf that is born easily. It is measured as %EDBH, or the expected percentage of difficult births in first-calf heifers. The current Holstein breed average is 8 percent, and the range among active artificial insemination (A.I.) bulls is 3 to 17 percent.

Daughter calving ease (DCE) was introduced in 2003 and measures the calving event from the other side of the equation. Certain sires do a better job than others of making daughters that calve more easily. Daughter calving ease (DCE) is measured on the same percentage scale and the Holstein breed also averages 8 percent in this trait with a range of 4 to 14 percent.

Measurement of stillbirths was newly added with the August 2006 evaluations and, like calving ease, is measured through recorded DHI (Dairy Herd Improvement) information. A stillbirth is defined as a calf born dead or that dies within 48 hours of birth. Stillbirths have averaged 7 to 8 percent of all calvings in recent years, and 8 percent is deemed average, just like the Holstein calving ease base. Keep in mind this figure is for all calvings, whereas the sire calving ease traits are based on expected difficult births in first-calf heifers.

Average stillbirth rates are higher in first calvings (12 percent) than second calvings and beyond (5 percent). Like the sire and daughter calving ease indexes, stillbirths are also measured from both angles. The identification of bulls more likely to sire stillborn calves is measured as sire stillbirth (SSB), and the identification of bulls whose daughters tend to have stillborn calves is captured through the daughter stillbirth (DSB) index.

I have often felt few things are more disappointing on a dairy farm than the arrival of a dead calf. Not only do you suffer the most basic loss of a future replacement heifer, or at least some quick cash for the sale of a bull calf, but to add insult to injury, you must now spend time and money to dispose of the carcass. Depending on the nature of the calving, you get the added challenge of doctoring the cow, too. Genetic selection for improved calving ability will not overcome the need for good hands-on management, but it should work in concert with you to make the calving process easier.

As margins on the dairy farm get tighter, making cows that last a bit longer helps keep costs down. A healthy, disease-resistant, trouble-free, easy-keeper kind of a cow that more easily delivers a live calf should be in everyone’s best interests. LNM$-based sire selection addresses these needs while also identifying improved calving performance. An easy calving by itself doesn’t guarantee lifelong profitable bliss, but it does help provide a live calf and a cow with a start in the right direction. PD

References omitted but are available upon request by e-mailing editor@progressivedairy.com.

—From Horizons, November 2006