EBVs and How to Use Them

Are you totally confused as to what exactly is an Estimated Breeding Value? Have you ever tried to calculate one and thrown your pencil in the air in frustration? Well, the age of computers has solved this most perplexing problem. Estimated Breeding Values (EBV’s) are nothing but averages of differences multiplied by a constant. Sounds simple, but it is very easy to get lost in which difference is averaged with what. So, using a spread sheet, the convoluted calculations have been reduced to a simple matrix. All you have to do is find the target values and follow the line across and down to arrive at the answer. No more calculators, no more broken pencils.

First, what is an EBV and why should you even worry about it? EBV is the best way to predict the average fleece characteristics of as yet unborn progeny when using a known buck over a known doe herd. Researchers in Australia have spent five years figuring the values out and they can be a valuable tool for predicting the future.

To put it simply, all fleece characteristics have different heritabilities. That is, some are more likely to be passed on to progeny than others. For example, production is highly heritable whereas the Secondary/Primary (S/P) ratio for follicle density is not very heritable. So, if you are interested in increasing your production, you need to figure out what the EBV is for your doe herd. This is done by simply averaging the percent yield for your does. The does are always considered as a group, so differences between does within the herd are ignored. What we are trying to figure out is the expected average of the kids produced by this doe herd. So, let’s say your doe herd averages 20 percent yield and you would like to increase it to 30 percent. Now you can plainly see that a higher yielding buck will be required but how much higher? You don’t want to use too high a producing buck because that will increase your fiber diameter unacceptably. The trick is to select the finest buck that will give you your expected increase in down production.

The most important thing to remember is that production of a single buck means nothing unless you know what the average is for the herd from which that buck comes. This is so important, it needs to be restated. A buck which produces 300 and who comes from a herd that averages 250g will have a different effect on your does than another buck also with 300g production which comes from a herd that averages 200g.

The reason lies in population dynamics. When you look at a population of bucks, you can easily take an average of them all. If you were to graph that population, most of the herd would fall within a range close to that average. However, some individuals will fall way outside of the average range. This is what’s called a bell-shaped population curve (Figure 1). This bell-shaped population curve can be broken down into standard deviations, the an example of which is the shaded portion of the graph. This is where the most representative members of the population will fall and this is where your next buck should come from if you want to get your money’s. Here, bucks are more likely to have dominant genes for the expressed characteristics and will be more likely to pass on those genes.

So, back to our example, if you select a buck that is close to the average of the herd from which it comes, he is more likely to have dominant genes for the characteristic you are looking for and will be more likely to pass on those genes. Bucks that fall outside the middle range of the herd’s bell shaped curve are liable to be throwbacks to who knows what and may not pass on the desired genes.

So, your 50g does need to find an appropriate mate. Table 1 is the needed matrix. Notice that the matrix is broken into five separate groups based on the average of the herd from which the buck arises. The individual buck averages at 10 months of age are the top row of each group. The doe herd averages are along the left hand column of each group. You have found three potential bucks to breed your does. All are 18u, 250g, mature bucks from different herds. How do you choose between them? Buck #1 is from a 16u, 150g herd and tested at 15u, l00g as a kid. Buck #2 is from a 19u, 300g herd and tested at 15m, 200g as a kid. Buck #3 is from a 18u, 250g herd and tested at 15u, 150g as a kid. Using the EBV Table, you can predict now each buck might combine with the genetics of your does.

So, for Buck #1, look at the buck herd average of the 150g group, the second one down. Now follow across the row and find the individual buck average at 10 months of age of 100g. Follow the column down one row to the one for a doe herd average of 50g. The number there, 84.75, means that you can expect the average down production of the progeny using Buck #1 to be 84.75, almost 15g short of the l00g target.

For Buck #2, look at the fifth group of buck herd averages, the one for 300g down production. Follow the individual buck average row across to 200g, and then down to the next row for 50g doe herds. The number there is 144.5g. Your average progeny production using Buck #2, is likely to be 144.5g. Buck #3, located in the fourth grouping, will increase your progeny average to 119.5g. Clearly, Bucks #2 and #3 are the more appropriate choices as far as production goes. But what will they do to your micron diameter?

In order to focus your breeding strategies and narrow the potential buck field to one buck, you must consider the effect each buck will have on the average micron diameter of the progeny. All three bucks have a mature fiber diameter of 18.5u, meaning they were 16u bucks as kids, and your does have an average fiber diameter of 15u. The herd from which Buck #2 arises has a fiber diameter of 19 u.

Refer to Table 2 and look at the fifth grouping down. Follow across to a buck average of 16u, and then down two rows to the doe herd average of 15u. The number there, 16.30 means that your average fiber diameter for the progeny will be 16.30u. But you are shooting for 16u and you will need to reconsider.

Find Buck #3, an 18.5u buck from an 18u herd. Table 2 indicates that using Buck #3 will result in progeny that average 16.03u. Bingo! You have found your future stud sire. Using him will result in average progeny with 119g of production and 16u diameter. You have just doubled your production while keeping the average micron diameter at 16u. Besides, Buck #3 represents the average of his herd and falls within the first standard deviation on the population curve. He is a safe bet.

Here is a link to Table 3, EBVs for Bodyweight.

There are other things to remember. Just because an individual animal looks good today doesn’t mean he’s the buck for you. Always, always take into consideration the buck’s age and his environment. Cashmere fleece coarsens with age, sometimes to an unacceptable level. Research has shown that on average, a kid buck will coarsen 1.5u the first year and .5u every year after that until maturity. So if you are looking at a kid buck that tests at 16.5u, you must add 2.5u to that kid fleece test to approximate his fiber diameter as a six-tooth adult. If you buy a young animal, remember that the reason his price is discounted is that you are assuming the risk that he may coarsen and you may end up wasting a year or two of genetic progress because you made a mistake. Older bucks are more expensive and may be worth it.

Environment is also very important. Chinese cashmere, the world leader in fineness, is grown in a cold, inhospitable climate with little to eat. Goats grown in cold climates on available range may appear to have less production and finer diameter than they would on lush pasture at sea level. Goats grown in feedlot conditions will appear to have more production and coarser diameter than the same individual after it’s moved to West Texas brushland. The point to remember is that the genetics will remain the same no matter what an animal looks like. To quote Ted Scarlett, an Australian Goat Production Officer, “an animal’s performance is decided by genetics and by its environment. You must be careful to buy it for its genetic superiority because you cannot buy its environment.”

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