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<blockquote data-quote="ArmyDoc" data-source="post: 698371" data-attributes="member: 6832"><p>Let me see if I can explain it:</p><p>Your greatest hybrid vigor comes from crossing two completely unrelated animals "a" an "b". The closest you can come to this is two unrelated purebreds - say a continental and a british breed. Essentially, what you are doing is undoing the inbreeding that occured to develope the breeds. You get 50/50 with neither half matching the other.</p><p></p><p>But what about the next generation? If you breed back to either of the two original breeds, you get an animal that is 75% one breed and 25% the other - much less hybred vigor than 50/50.</p><p></p><p>You can still get some hybred viggor by choosing a third breed "c", that is unrelated to the first two - say a bos indicus breed like brahman. This gives you 50/25/25. Each "portion" unrelated to the other, maintaining the highest level of hybrid vigor.</p><p></p><p>But what about the next generation? If you breed back to any of the first 3 breeds, you don't maintain as much hybred vigor. If you go back to "a" or "b", you get 62.5/25/12.5. If you stick with "c" you're even worse off, with 75/12.5/12.5</p><p></p><p>Ideally, you'd like to get a 4th totally unrelated breed, to end up with 50/25/12.5/12.5. Unfortunately, there isn't any 45h totally unrelated breed. All the cattle fall into one of those three groups - british, continental and bos indicus. Sure, you can pick a different but somewhat related breed, and get some hybred vigor, but most people go back to one of the first two breeds "a" or "b". This is a three breed rotation, and from what I've read maintains the greates hybred vigor in each succeding generation, though still not as much as in that first cross.</p><p></p><p>Bottom line, the more times you cross breed, the further you get away from a purebred animal. The further away from a purebred animal, the less hybrid vigor you get from crossing to an unrelated animal.</p></blockquote><p></p>
[QUOTE="ArmyDoc, post: 698371, member: 6832"] Let me see if I can explain it: Your greatest hybrid vigor comes from crossing two completely unrelated animals "a" an "b". The closest you can come to this is two unrelated purebreds - say a continental and a british breed. Essentially, what you are doing is undoing the inbreeding that occured to develope the breeds. You get 50/50 with neither half matching the other. But what about the next generation? If you breed back to either of the two original breeds, you get an animal that is 75% one breed and 25% the other - much less hybred vigor than 50/50. You can still get some hybred viggor by choosing a third breed "c", that is unrelated to the first two - say a bos indicus breed like brahman. This gives you 50/25/25. Each "portion" unrelated to the other, maintaining the highest level of hybrid vigor. But what about the next generation? If you breed back to any of the first 3 breeds, you don't maintain as much hybred vigor. If you go back to "a" or "b", you get 62.5/25/12.5. If you stick with "c" you're even worse off, with 75/12.5/12.5 Ideally, you'd like to get a 4th totally unrelated breed, to end up with 50/25/12.5/12.5. Unfortunately, there isn't any 45h totally unrelated breed. All the cattle fall into one of those three groups - british, continental and bos indicus. Sure, you can pick a different but somewhat related breed, and get some hybred vigor, but most people go back to one of the first two breeds "a" or "b". This is a three breed rotation, and from what I've read maintains the greates hybred vigor in each succeding generation, though still not as much as in that first cross. Bottom line, the more times you cross breed, the further you get away from a purebred animal. The further away from a purebred animal, the less hybrid vigor you get from crossing to an unrelated animal. [/QUOTE]
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