The Official Forum of the Ameraucana Breeders Club > Breeding

Cross beak - genetic, environment...what?

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Susan Mouw:
Yes, that cockbird is headed for freezer camp and someone is coming to get the hen tomorrow for a backyard layer.

Lee G:
I agree with Harry, some strains are more prone to the deformity than others. Cross beak is an immediate cull for me. But interestingly enough, and according to one of my genetic books, it is a hard trait/defect to pin point inheritance, and wholly complex. Yes, it can be caused by too high of temperature during incubation, and even brought about by the environment. (Epigenetic's at play perhaps?) It’s also thought to be genetic, and recessive, and linked to the mb gene when homozygous. (Which explains why Ameraucanas seem more susceptible than other non bearded breeds, although it appears in all fowl.) But here’s the catch; both Hutt and Landauer found it was not possible to breed pure breeding cross beaked birds, even after heavily inbreeding for multiple generations. Birds thought to be impure for cross beak, produced cross beak offspring. Birds thought to be pure for cross beak, produced offspring with normal beaks. My book calls it ‘an extremity on multifactorial basis with incomplete penetrance.’  :o Alrighty then. I’ll stick to calling it an immediate cull on an individual basis, but won’t cull an entire family line because of it.

Good food for thought here.  :)

Lee G:
One way I use to id (and cull) chicks that could be potential cross beaks can be done right from hatch, though I like to give them 24 hrs to fluff up, and shed the egg tooth. While holding the chick firmly in hand, tip its' head back and look closely at the top and bottom mandibles from the underside; they should be even on both sides, and fit together perfectly, as well as be nice and straight. Any kind of deviation from this, like showing more beak on one side than the other, or any kind of curve, etc, could be a potential cross beak cull within a few weeks…hope this helps others save a bit on feed and space. ;)

Susan Mouw:

--- Quote from: Lee G on May 19, 2016, 09:34:36 AM ---One way I use to id (and cull) chicks that could be potential cross beaks can be done right from hatch, though I like to give them 24 hrs to fluff up, and shed the egg tooth. While holding the chick firmly in hand, tip its' head back and look closely at the top and bottom mandibles from the underside; they should be even on both sides, and fit together perfectly, as well as be nice and straight. Any kind of deviation from this, like showing more beak on one side than the other, or any kind of curve, etc, could be a potential cross beak cull within a few weeks…hope this helps others save a bit on feed and space. ;)

--- End quote ---

Incomplete penetrance?  Well, that would explain a lot - such as why one bird shows it at hatch and another takes 3 weeks for it to show. It would also explain the varying degrees of it.  At least it is thought to be recessive.  We have an inherited disorder in Labrador Retrievers, called Tricuspid Valve Dysplasia, that is, at least theoretically, autosomal dominant with incomplete penetrance.  The dominance mean that it is very hard to breed around, and incomplete penetrance means that some dogs can carry the gene(s) for TVD, without displaying any symptoms, yet pass it on to their offspring - and it only takes one parent to carry it.

At least with the recessive, it takes two.

Afterthought - if anyone needs help getting to sleep one night, try reading my article on the Genetics of TVD. http://www.ameraucana.org/docs/Genetics%20of%20TVD.pdf This was published, in a serialized format, in the Labrador Quarterly - either last year or year before - I can't remember now. Worked better than sominex, so I'm told.

Lee G:
But wouldn't dominance mean it'd be easier to breed around in poultry? Because a dominant gene can't help but express itself, and than you at least know what you're dealing with. Where as recessive genes can hide for generations, and pop out of the wood work when you pair certain birds/families and least expect it. A good reminder why test mating is so important though. Mammals are very different than avians, wow... My brain was not ready to look over that paper this morning Susan. lol Need more java, maybe more brain.  ::) haha


Oh, and I just confirmed my first (and hopefully last, knock on wood) cross beak chick this year. It was a blue from a batch of 30. All the rest look good, and still do, but sadly this little one was unlucky from the get go. :( Unfortunately I didn't think to take any head pics at hatch, but here is the chick at 10 days old with what has become obvious cross beak. I marked it as a potential cross beak from hatch, and grew it out until I could be sure.

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