Regional Extension Agent/Animal Science & Forages
As I was preparing to write this article, I took the liberty to read several articles written by Ph. D’s regarding selecting replacement heifers. Though I often have a tendency to over simplify things, three themes emerged about replacement heifers; 1) replacements are costly, 2) they should be a genetic improvement to the herd, 3) and the heifer should become a fertile cow that produces a calf annually for a long time. I think most producers would agree with my simplified summarization, but what criteria can producers use to select the right replacement heifers that will offer genetic improvement, annual calf production, and longevity for their money?
To select a replacement heifer that meets all of the criteria above, she must first exist. In today’s time, there are many tools, strategies and research data available to assist commercial cattlemen in producing quality replacement heifers that are more likely to be productive in a herd for many years.
Probably the most common selection criteria for commercial cow-calf producers are looks. The best looking heifers are the ones that are chosen for replacements. This tends to pick heifers from the earliest calving cows along with selecting genetics that emphasize growth. Both of these are positive contributions and in many cases, breed composition and looks are the only selection criteria available to a buyer. While looks are important, using this as a sole means for heifer selection may not be ensuring selection for fertility and longevity.
One production strategy that can influence longevity is to use a good crossbreeding program. Research has shown for many years how using complimentary breeds can increase maternal heterosis and longevity in cows. Matching a good crossbreeding program and using EPD’s to select sires that have desirable traits for size, milking ability, and calving ease can also aid in producing replacements that can be successful in a herd.
Evaluation of the reproductive tract of a heifer can be used to help determine if a heifer is sexually mature enough for breeding along with detecting possible reproductive problems associated with malformed uterine horns and ovaries. In return, this helps us to select more fertile heifers. The reproductive tract scoring system ranges from 1 to 5, with 1 being a less developed reproductive tract and not yet cycling and a 5 being cycling based on the presence of a corpus luteum or large follicle on the ovaries and good uterine tone. Heifers with scores above 3 generally have higher pregnancy rates and conceive earlier than heifers with a reproductive tract score of less than 3. Thus, using these scores to select heifers can increase the number of heifers being pregnant at the end of the breeding season with a higher percentage of the heifers conceiving early in the breeding season.
Generally, the goal for a first calf heifer is to have a live calf and then to get rebred in a timely manner. Taking pelvic measurements and choosing heifers with adequate pelvic size and culling the heifers with the smallest pelvic measurements can decrease the percentage of assisted births along with increasing the number of live calves born to heifers. Of course, breeding these heifers to bulls known to have low birth weights will also decrease the chances of calving difficulty. By reducing the trauma of calving, a heifer is more likely to recover and get rebred in a timely manner, thus increasing her chances of becoming part of the cow herd.
There are many other factors that should be taken into consideration when it comes to selecting replacement heifers such as environment, nutritional requirements, and temperament to name a few. As I mentioned in the beginning of this article, I have a tendency to over simplify things. It will take some time, effort and thought to utilize the selection tools that I mentioned in this article, but by using as much information as possible to select replacement heifers, we will be better equipped to choose a heifer that will become that productive cow that will last in the herd for many years.