Every day we are hearing more and more about Expected Progeny Differences. They are available for our animals on the ARI website. So now what do we do with them? How do we use them? Will they help us to sell alpacas? Do we post them online and print them in our sales literature to market our animals? Well, yes EPDs can be used to help market sale of animals or stud services, but that is not the purpose for which they were developed. EPDs are a tool for the selective breeder of livestock to use in making breeding decisions about selection and mating choices.
Where do we want to go with our breeding programs? What are our goals for the next generation of crias, and the generation after that? If we don’t know where we are going then any road (or EPD) will take us there. But if we do have specific goals about the outcome of the next cria we are going to produce from a certain female, or for the whole next annual crop of crias from our herd, then we can begin to develop a strategy for how we are going to reach that goal. Using EPDs to make selection decisions, which means deciding which animals to use for breeding, and to make mating decisions, which means deciding which two animals will breed with each other, can move us more rapidly and predictably toward our goal. This has been proven time and again with other livestock.
Quantitative genetic science and mathematics is a very sophisticated body of knowledge that can become a whole field of study in and of itself. Most of us will never have the inclination or the time to learn and understand even a fraction of it. The good news is that it is not really necessary to understand anything about the actual math and science behind EPD calculations in order to use these tools for breeding decisions, just as it is not necessary to understand electronic circuits and processors and machine language to turn on the tool of your computer and read this article.
“But I not only don’t understand how EPDs are calculated, I don’t even know how to use them!” Here is the even better news, we really do already know how to use EPDs. In fact almost every ARI member has been using EPDs since they bought their very first breeding stock. How is that possible? Let’s take a look at what that means.
Very few alpaca breeders practice random mating. Most of us will look at a female that we plan to use as a dam and begin to think about what male we want to mate with her. We might only have the goal of producing an offspring that is an exact copy of her, but in most cases we are thinking about how we would like the offspring to be different from her, presumably improving on her in some way. Maybe we would like to see the offspring have a longer staple length than the fleece on the dam, or more crimp in the fiber, or a larger or smaller stature, a wider or more narrow chest, a different color fleece, or more fiber coverage on the legs, or more consistency in the fleece, or more density, better structure, the possibilities are almost endless. But in each particular case we probably are thinking about how we want to genetically improve the offspring over the dam in one or more particular traits. We then start looking for a male that we believe will produce that change in the cria when mated with our dam. We select a male to mate with her because we think that the offspring is going to in some way be better than the dam in regard to the particular trait or traits of interest.
There are many ways in which we might go about making our decision about which male to use. Perhaps we will look at his conformation or his fleece, or the conformation or the fleece of his existing offspring. Perhaps we will look at his pedigree, or his skin biopsy results, or his histograms or his show performance but however we do so, we are making the decision and selecting this male because we believe that mating him with our female will result in a cria that is in some way different from the dam. We are expecting a difference in the progeny. Therefore we have just used an “expected progeny difference,” an EPD, to make our decision.
The process of using ARI calculated EPDs is no different than whatever process we have used in the past to make our selection and mating decisions with expectations of differences in the progeny. The process is the same, but when we use the scientifically calculated EPDs the rate at which our breeding programs move toward our chosen goals should be much more rapid, because our selection accuracy will be greater. That of course is also the major reason why EPDs can be an effective marketing tool, even though that is only a secondary purpose for them. A byproduct of their value in determining the genetic breeding value of an animal for a given trait is that in turn helps to determine the sale value of that animal based on a more accurate prediction of what the animal can do genetically in a buyer’s breeding program. This is true whether you are offering up an animal for sale or searching for one to buy yourself for a particular genetic goal in your breeding program.
Now that we realize that we already have been using EPDs all the time, let's look at how to use the calculated EPDs in particular. A really good place to start is to read the Producer’s Report which Dr. Enns just released with the latest set of EPD results. Let’s familiarize ourselves with that information and the next article will deal with the meaning and use of the EPD numbers we are receiving as well as the accuracy reported along with those values.