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Crossbreeding Musings
Contributed by

Jody and Chris Rohr
Millersburg, OH
E-mail rohrfarm@valkyrie.net
Editor's Note: Jody Rohr wrote the following after reading the article "Why Crossbreds May Be Superior to Purebreds: Breeding A Better Goat" written by Dr. Will R.Getz for the Georgia Goat Research & Extension Center, College of Agriculture, Home Economics, and Allied Programs, Fort Valley State University. Click Here to read the original article.
A companion to Jody Rohr's and Dr. Getz's works is Marvin Shurley's "Genetics".Click Here for Mr. Shurley's article.

That crossbreds usually perform better than purebreds isn't news. But the other info about heretibilities was something I've been wondering about for sometime. I've been wondering if my very nice 3/4 Boer doe would have equally as nice 7/8 Boer kids... From what I see in this article I may expect same or less performance in the way of certain traits while seeing more predictability in others.

Something that I would like to emphasize, and it was alluded to in this article but not stated firmly, is that purebred goats must exist in order to produce F1 crosses that express that hybrid vigor. The F1 cross is the 50% cross resulting from two purebreds of different breeds.

The point is that, like in the cattle world, some of us purists should continue with our purebreds, trying to produce the hardiest, most predictable genetics that we can, so that the commercial breeder can benefit from heterosis/hybrid vigor. If we select our purebreds and breed them for the best performance within their own breed then what we can offer the commercial breeder is something that he/she can really use! Those F1 kids from a superior cross of purebreds will out-perform a mediocre cross of purebreds.

Producing highly predictable genetics even within a breed isn't as easy as it sounds. It can take a lifetime to do this. Cattle breeders attempt to do this by carefully line-breeding their purebreds. I think that goat producers have a lot of room to work. It seems to me (my opinion) that goats have more genetic variability than cattle do. It could take a goat procucer (Take Note: this is my estimate based on intuition and not scientific fact...) two to three times as long to narrow down their genetics using line breeding and carefully culling those with defects or poor performance.

Cattle producers are on the right track with their EPD record keeping but it seems to me that the EPD system is not standardized to be relevant to all cattle breeders. What I mean is that the Hereford EPD system is different than say, the Angus system, and I can't read the EPDs of an Angus and compare to a Hereford without getting very familiar with both systems and both breeds of cattle. It would be wise for all meat goat breeds to start out with a universal or standardized system of EPDs if we ever get to that point. Even then I would think breed differences cause cross-breed EPDs to be less useful than those within a breed. EPDs (Estimated Progeny Differences) are the facts and figures we need to plan matings and eliminate some of the guess work. Still, EPDs aren't a set-in-stone guarantee that the mating will turn out in real life like it does on paper. But it is a much more sure way of breeding than a guess or a shot in the dark. EPDs require more record keeping and paperwork for the purebred producer, and more involvement at the breed organization level.

Genetic progress is speeded up by selecting for no more than 3 traits at one time.... This means we need to prioritize what is important in our own herd based on what we have to work with. I personally would like to improve growth, width of body, and good head conformation (which is really several traits all in one spot: tooth alignment, open nostrils, roman nose.....) and meatiness. That's four (or 7, depending on how you want to look at it...) traits. I have to choose which is the most important for me, right now, and work on it without changing horses in mid-stream, until the goal is achieved with high predictability. Then I can start working on 3 more traits... and then of course I will see some predictability in the first 3 traits start to wane....

Creating new breeds out of crosses isn't always as successful as selecting for certain traits within a breed because of the increase of genetic variability in the crosses. Increased variability gives one a larger gene pool to work with but also less predictability. This is where knowing heretibility of the trait you are selecting for is very important - it will help the new-breed crossbreeder to stay on track. And in the end, even a breed derived from a cross will lose its hybrid vigor due to concentrated selection for certain traits.

Of course, I'm still "shooting in the dark" with my program because I don't know all my individuals well enough yet to know what traits they are strong in and what they aren't. I'm trying to match bucks and does in such a way as to moderate the weaknesses and strengthen their strong points. It isn't always possible as sometimes both doe and buck are weak in the same area. This is where it helps to keep a buck for longer than 2 years - we get a chance to find out what the genetic make up of the buck really is and it means we need to either keep more goats or cull heavily to make room for better animals... I am not in a position yet to buy the best of the best (therefore breed the best to the best), though I'd like to.... but that route, of course, is the quickest way to produce the best....

It isn't easy but it is something to take some of the doldrums out of our day to day animal husbandry!

Jody Rohr
Millersburg, OH, USA


 

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