Cattle Genomics: sire selection tools for breeding more productive, profitable cows


The Cattle Site

19 September 2022


When we think about what makes a commercial cowherd exceptional, we must remember the long-term role that effective sire selection plays.


Editor's note: originally published: Cattlemen’s News Magazine


Nailing the bull-buying decision is essential for the long-term success of an operation. This decision impacts not only the calf crops that a bull sires during its lifetime but also performance in successive generations when replacement females are retained. Long-lived females are the cornerstone of a profitable commercial operation, so identifying bulls that will sire productive daughters is essential, writes Dr. Troy Rowan, assistant professor at the UTIA Genomics Center for the Advancement of Agriculture.


A commercial cow typically doesn’t become profitable until six years of age. Only then has it recouped the cost of its development and maintenance costs. We know that heifer development done the right way is not cheap, so cows leaving the heard before that profitable age are likely losing money.


Since cow longevity is such an important trait, and bulls are the chief driver of genetic progress in a commercial herd, having EPD-based selection tools for cow productivity is essential for long-term genetic improvement. Predicting a bull’s genetic ability to make long-lived daughters allows us to better evaluate its “big picture” contributions to the herd.


Many breed associations report cow longevity EPDs. The most common measure is stayability (STAY). STAY EPDs can be interpreted as the difference between sires in the percentage of daughters that will remain in the herd until age six without missing a calf. For example, if Bull A’s STAY EPD was 20 and Bull B’s was 30, we’d expect that 10% more of Bull B’s daughters would remain in the herd at age 6. The results of using STAY in practice are striking. An analysis from the American Simmental Association showed that daughters of bulls in the top 25% of the breed for STAY were twice as likely to remain in the herd at age six compared with daughters of bulls in the bottom 25% of the breed. Daughters of high STAY (top 25%) sires had an average of two more calves in their productive lifetime than daughters of low STAY sires.


Stayability is a compound trait, meaning that it is made up of multiple other individual component traits. All of the reasons we could imagine culling a cow from the herd early play into STAY: Fertility, structural soundness, udder quality, disposition, maternal ability, and other traits. Many breed associations also directly report EPDs for individual cow-focused traits. This allows us to select for important female traits in breeds without STAY EPDs, as well as on specific components of overall longevity that a particular herd might need.


For example, we might see that our herd is plagued by foot and leg issues...


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