When Used Correctly EBVs Will Make You Money!
Dr R Mark Enns, Department of Animal Sciences, Colorado State University
The advantages of a Total Herd Reporting (THR) system bring many benefits to Charolais breeders in terms of improving genetic tools. These tools which might include stayability and heifer pregnancy EBV, will help breeders make more profitable breeding decisions.
With the addition of EBV for more traits there is danger of overwhelming breeders with genetic information. Often I hear the words, “There are just too many EBVs, so I don’t look at them. I just pick a bull that looks good”. This perspective likely costs that breeder potential income – EBV are the best single tool for making genetic progress and ultimately producing animals that are more profitable.
So if EBVs are one of the best tools, how should breeders wade through all of that information? The key is to focus on the economically relevant traits.
Making Selection Easier
Narrowing down the list of EBV to only those applicable to a particular production system will help make selection easier and genetic progress faster in those traits.
As a general rule of thumb, the fewer traits considered when selection decisions are made, the more genetic progress is made in each of those traits.
However, using that logic, the first thought might be that the fastest way to make progress is to focus on a single trait. While tremendous genetic change can be achieved by selecting on a single trait, we never advocate single trait selection—single trait selection always brings about unintended consequences.
For instance, if a breeder were to focus all selection solely on 400 day weight, ignoring all other traits, what would occur over time? That breeder would make tremendous improvement in 400 day weight but would also end up with bigger cows that required more feed, and had calves with greater and greater birth weights. In hard years, those cows would likely also have more difficulty rebreeding and producing calves the following year.
Realistically, when making selection decisions, the challenge is determining the “middle ground” that avoids the pitfalls of single trait selection yet narrows the list of EBV from all of those available.
Finding the “Middle Ground”
Determining where that “middle ground” is depends upon an understanding of the difference between an economically relevant trait
and an indicator trait
—these are the two classes of traits.
What are Economically Relevant Traits (ERTs)?
Economically relevant traits are traits directly related to either increases in income or costs of production.
From a commercial producer’s standpoint, identifying the economically relevant traits involves asking, “If all else were equal and I changed only the EBV for this trait up (or down), will it influence my income or my costs?”
If that producer can answer “yes” to this question, then the trait is economically relevant in that production system. If it is economically relevant, then it should be considered when making selection decisions.
If the answer is “no”, then it should not be considered when making your selection decisions.
Immediately, the list of EBV to consider when making selection decisions is narrowed.
The above approach and question to identify the economically relevant traits takes a commercial producer’s perspective.
The perspective changes, however, for seedstock breeders. The seedstock breeders should ask themselves, “If all else is equal and I change only this EBV up (or down), will it influence the income or the expense of my customers’ herd?”
Seedstock breeders should evaluate EBV from the perspective of their commercial customers because the majority of bulls are sold to these breeders.
By asking these questions the economically relevant traits for a particular production system are easily identified.
So what about those traits that are not economically relevant? These are the indicator traits. Indicator traits are important because they add accuracy to the EBV for the economically relevant traits through their genetic correlation to those traits.
Birth weight and calving ease provide an excellent example of this relationship and the difference between the two classes of traits.
If the birth weight of calves born to heifers changes one kilogram does that change always influence the expense or income of farm? The answer to this is clearly no. Moving birth weight from 38 to 39 kg for instance, would not likely influence profitability. Birth weight is an indicator of calving ease.
But if the number of heifers requiring assistance (calving ease) were reduced by 1%, both cost and income would be affected.
• First there are more and heavier calves available to sell.
• Lower calving ease results in fewer calf deaths, and eliminates reduced performance in those calves experiencing calving difficulty.
• Problems with delayed rebreeding in the heifers are reduced as are labour costs associated with heifer calving.
In this case, calving ease is the economically relevant trait while birth weight is the indicator trait.
If EBVs for both of these traits were available, focus should be placed on calving ease rather than birth weight when making selection decisions. Additionally, the birth weight information is used in the calculation of a calving ease EBV—birth weight is already accounted for in a calving ease EBV.
In the New Zealand production system with the cyclical nature of grass resources, this concept is particularly important.
The NZCCS produces EBV for 200, 400, and 600 day weight. This is necessary because the customers of their breeders sell their calves at different times. Some sell at the end of the first summer, and others later.
How does this translate to the concept of economically relevant traits?
Charolais bull buyers should consider how you market the offspring of the bulls you are buying:
1. If you market them in the first summer the economically relevant trait is 200 day weight
—that is the EBV upon which you should focus your selection decisions (considering calving ease as well, of course).
2. If you market animals after their second summer, then 400 day weight is the economically relevant trait.
Selection decisions should focus on the EBV for 400 day weight with no emphasis on 200 or 600 day weight—those breeders do not get paid for 200 day or 600 day weight!
The same technique can be applied to milk EBV.
3. If the farm is not retaining replacements from the Charolais bulls, milk has no influence on its profitability—it is not economically relevant. On the other hand, if the farm is retaining replacement females sired by the Charolais bulls, milk is economically relevant.
By using the concept of economically relevant traits, a breeder can reduce the number of EBV that he must consider when making selection decisions and can avoid becoming overwhelmed by the sheer number of EBV.
This is the first and easiest step at making selection decisions easier and in making rapid progress in those traits that matter!