Health and Fitness Traits for More Functional Cows

Dairy producers have selected for higher milk production for many years. Genetic improvement causes an average Holstein cow born in 2003 to produce over 7,000 lbs more milk in one lactation than her ancestor born in 1960 produced. Type traits, particularly udders and feet and legs, have also improved because of intensive selection. However, the health and fertility of dairy cows cannot be included among these success stories. The most obvious example is that genetic trend was responsible for half of a nine-point decline in pregnancy rate in Holsteins between 1960 and its low point in 1995.

The industry response has been to develop a national genetic evaluation program for a number of fitness traits, fertility among them, in recent years. In 1994, the year Lifetime Net Merit (LNM) along with genetic evaluations for productive life and somatic cell score were introduced, production traits received 74 percent of total emphasis. By 2006, emphasis on production traits had declined to 46 percent of total emphasis with most of the remaining emphasis on fitness traits. Look for emphasis on production to be reduced further in the next revision of LNM, scheduled in conjunction with a genetic base change in 2010.

In 2003, I wrote an article titled "Holsteins do what we bred them to do" for the A.I. column in Hoard's Dairyman. The column was inspired by questions from a Swedish Red breeder in South America. Cows in her part of the world were managed on a grass based, low input system, leading to different expectations of optimum cow performance than most U.S. dairy farmers. Here is an extract from that piece:

Expectations for the Holstein cow were changing at that time, and that column (extracted) went on to say

Today, dairy breeders are voting through sire selection decisions for healthier, more fertile cows that last - and still produce. We should anticipate increased emphasis on health and fitness traits in the years to come, as well as more success from those efforts through genomic evaluations. We can expect much more accurate identification of potential bull mothers with exceptional genetics for lowly heritable traits. In the past, we were more or less guessing which cows were really more fertile or would live longer at the time in their lives when they became bull mothers. Genomic evaluations, of course, also enable much more accurate screening of the young bulls produced prior to progeny test.

Using Genetic Evaluations for Fitness Traits

Genetic evaluations for health and fitness traits have been added to existing proofs for production and conformation. There is a one-way valve on genetic evaluations as we only add to existing lists. The Genex Investment Guide for August 2009 included 28 different traits, composites and indexes excluded, for each bull. How should dairy farmers manage all that information? Following are some thoughts on how to use genetic information on fitness - and other - traits.

Selection indexes that combine production, health and fitness proofs are essential to make consistent, wise selection decisions. LNM (or Fluid and Cheese Merit), finds A.I. bulls whose daughters have optimum combinations of favorable genes for lifetime economic merit. The economic values used in LNM make it especially useful for commercial producers. Fluid Merit is a good choice for farmers who sell to high Class I milk markets with no protein premiums.

In the past, I have advised using calving difficulty proofs to choose mates for virgin heifers, but to continue to use bulls with less desirable proofs for calving difficulty on older cows. I no longer support this practice. A mature Holstein cow can safely deliver a heifer calf sired by calving difficulty bulls, but that heifer calf inherits calving difficulty genes from the sire. Those unfavorable genes will be preserved in the heifer, expressed in her first and all subsequent calves, should she survive the first experience. Holstein breeders should discriminate against bulls with extreme calving difficulty, even if their overall merit is outstanding.

Producers should be careful not to be too attracted to bulls with outstanding merit for one or two fitness traits or type composites, unless those bulls have acceptable rank for a comprehensive index like LNM. For instance, unrestricted selection to improve fertility could also reduce yields. A more judicious practice would be to choose bulls with higher Daughter Pregnancy Rate (DPR) ratings among the top 20 percent of all A.I. bulls for LNM. This method ensures "fertility" bulls are outstanding for LNM at the same time.

Higher proofs are better for many traits including Productive Life, DPR, udder composite and feet and leg composite. Lower proofs are better for Somatic Cell Score, service sire calving difficulty, daughter calving difficulty, service sire stillbirth rate, and daughter stillbirth rate. Lower values for size composite are favorable in Holsteins for many herds. LNM already accounts for differences in direction of selection, the economic value of each trait, and how each trait relates genetically to other traits in the index. If selection is based on LNM, producers don't need to know the answer to this question.

The addition of health and fitness traits to genetic evaluations for type and production is leading to much more effective breeding programs for improved lifetime economic merit of dairy cows. Breeding programs should focus on the total cow - healthy, fertile, productive, with udders and feet/legs appropriate for today's management systems. The tools available to breeders today are the best we have ever had, and can be expected to become even better as genomic technology evolves in the years to come. Genetic improvement is an investment in the long-term profitability of the dairy herd. All producers, regardless of any other features of their farm, have access to the best genetics that have ever been available.