Age and time can certainly change one's perspective on many things. Longevity is a subject that has an evolving meaning to me. I suppose that has something to do with the celebration of this author's 50th birthday this year. Longevity, as defined in the Merriam-Webster dictionary, is a long duration of individual life or long continuance. How does longevity apply to the cattle business? It depends on who you ask.
In cattle terms, longevity would be the age at which a cow dies or is removed from the herd due to her lack of productivity. Assuming normal conditions and a minimal amount individual stresses on a cow, it is not unusual to expect a beef cow to be productive up to 8 - 12 years of age. As we all know, cows can be culled much earlier than this "average" lifespan for various reasons while some cows can remain productive for many years past this range. We've all heard the occasional boast of someone possessing a cow that was "old enough to vote".
Greater longevity certainly has economic benefits for the commercial producer. Given the ever-increasing costs associated with developing a heifer or purchasing replacement females, these females need to remain in the herd several years to help spread out the initial expense of adding young females to the herd. Cows with greater longevity reduce the need for replacement heifers. Herds with a greater number of mature cows usually have a higher percentage of calf crop weaned and wean heavier calves. Mature cows simply do not face the challenges that a first-calf heifer faces such as the first calving and lactation, getting rebred and continuing to grow towards mature size.
How can we improve the longevity of a beef cow? Research has shown that longevity is a relatively low heritability trait that is difficult to make progress with through simple selection. A commercial producer can make significant improvement on longevity as with other lowly heritable traits by using crossbreeding. Research has shown that crossbred females typically live longer and are more productive than purebred females.
A producer can make improvements in cow longevity by concentrating indicators of structural soundness. Emphasizing skeletal soundness, good feet, udder quality, and monitoring tooth wear can help to keep a female in the herd for many years. Matching a cow's biological type and genetic potential to available feed resources and the environment is also important to insure a long, productive life. For example, a larger framed, higher milking female probably will not rebreed and perform as well in an arid climate as will a more moderate framed, average milking female.
Seedstock producers are starting to see more selection tools becoming available to them from national breed associations that should improve progress in longevity through selection. Expected Progeny Differences (EPDs) are available for such measures as Calving Ease Direct (CED), Heifer Pregnancy (HP), Calving Ease Maternal (CEM), and Stayability (STAY). By utilizing EPDs such as these, the seedstock producer can provide the proper genetics that can stay in the commercial producer's herd for many years.
However, it is evident that many seedstock producers do not value cow longevity as highly as the commercial producer. In today's highly competitive seedstock market, breeders are often compelled to make continual improvement on highly marketable traits such as weaning weight, yearling weight, and carcass traits. Look at just about any breed's documentation of change over a period of years and you can observe an increase in numeric values in growth and carcass EPDs. This is a direct result of using proven sires on younger females with higher EPD profiles than their maternal predecessors.
Is this increase in EPD values a positive? I believe the answer is a "qualified" yes. More growth rate and improved carcass traits is a positive as long as it does not negatively impact the fertility and productivity of the cow herd. Finding the proper balance between these potentially antagonistic traits is the challenge for today's seedstock producer. Given the fact that the nation's cow herd is currently at historically low levels, we need to efficiently produce an increasing number of pounds of high quality product from each head in order to meet the needs of the U.S. and world market.
The value of cow longevity is important to all segments of the cow-calf industry but is probably valued a bit higher by the average commercial producer than many involved in seedstock production. I suppose the variation in emphasis lies in the producer's perspective of the beef industry. My perspective of longevity has changed with the passing years. I certainly value longevity much more today than I did when I was a teenager!
Source: John F. Grimes, OSU Extension Beef Coordinator