By Jackie Atkins, Ph.D., Director of Science and Education at the ASA
On a daily basis, cattle operations face management decisions that can make the enterprise either more or less successful. It’s not always easy to know what the right decision is but with some thought and advice from trusted sources, usually the choice becomes obvious. If it seems like the wrong direction, usually producers can change their minds and go a different direction. Selecting the genetics to use in the herd is not easy to reverse. It takes months, or years, or even decades (in the case of raising replacement females) to realize the results of that decision. Therefore, it is vital that beef cattle operations use the best measurements of genetic merit when selecting their breeding stock.
There is no argument among trained animal breeders, EPDs are the most accurate way to compare the genetic potential of different animals for a variety of traits. What can be confusing though is how much weight to put on the dozens of traits with EPDs. How important is weaning weight compared to calving ease? How much genetics for growth is beneficial before the size of the mature cow gets too big? Economic indexes take the guess work out of this equation and provide one simple number — representing profit.
With any enterprise, profit is equal to the total money generated (output) minus the total costs (inputs). Economic indexes use what we know about biology and the beef cycle to estimate the genetic potential for profit. This graphic from Tim Cartledge with Lancaster Black Simmentals (Meningie, SA, Australia) summarizes the genetic accounting in the All Purpose Index (API). API evaluates cattle used to generate replacement females and harvesting the remaining calf crop. Cartledge shows the inputs and outputs (economically relevant traits) for each sector of the beef industry. If there isn’t a direct measurement for the economically relevant traits, EPDs for correlated traits are used to predict EPDs for the economically relevant traits.
For instance, many people might think birth weight is an economically relevant trait. That would only be true if cow/calf producers were paid by the pound of the calf at birth. Rather birth weight is an indicator of calving ease. Calving ease direct and maternal are the best EPDs to estimate calf survival (the real economically relevant trait). In a similar fashion, milk and mature weight are used to predict cow intake.
If operations are selling all calves for harvest, terminal index (TI) should be used. With TI, the maternal traits no longer are economically relevant. Cow intake, replacement rate, and salvage weight are removed from the cow/calf sector. As direct calving ease remains a predictor of calf survival, calving ease direct remains in the calculation of TI but maternal calving ease is removed from the index as there won’t be daughters calving in this system. Economic indexes are easy to use — they take all the economically relevant traits and boil them down to one number — profit. Use economic indexes to ensure you choose the most profitable genetics for your operation.