Moving Forward- Breeding for Resistance to Marek's Disease

[chooks4life]

I started to respond to this earlier, but decided to think about this first.

When breeders began to supply birds on a commercial level, many decided to suffer low level losses rather than sell birds that were highly susceptible birds. This position registered with me. It could be said that we should have maintained this approach.

During the same time, some resisted the idea of fortified feeds believing that we were breeding nutritionally needy birds. There was evidence at the time that some strains were more tolerant of certain deficiencies than others and the traits were hereditary. This position could be argued against, but it is worth mentioning.

I'm very aware of the whole issue regarding breeding needy birds vs lower needs birds, but it's a very complex issue; I believe too often people are unwittingly erring on the side of inhumane practices. Our understanding of nutrition has continued to evolve at a rate that I don't think most nutritional guideline regulations, practices, etc have kept up with.

Virtually all commercial birds I see, which theoretically (their higher productivity notwithstanding) should be those with decently low nutritional needs due to being evaluated and bred for only short term existence and feed efficiency on very cheap, basic diets, are nevertheless deficient, and visibly showing the signs of their deficiency diseases. Not clinical signs, but the subclinical ones which will kill them if their cull-by date doesn't arrive sooner (which it almost always does, which allows the problem to continue, unrecognized). Because those who have never seen a chook in 100% health won't know what it looks like, the poor appearance of these birds is what is recognized as 'health'. But it's a low grade version of it.

Most people simply never know that their birds are deficient, since they don't recognize the signs. Being an Australian I'm very sensitive to this issue (funny how often regional differences crop up...) because most farmers I know allow clinical cases of malnutrition in their animals, not knowing any better, quite often farming by European or American standards on ancient Australian soil that is, on average, far poorer nutritionally than either of those countries.

Malnutrition is far more common than not, here I see it on almost all farms I ever lay eyes on. It grates at me a bit, and I'm aware I probably go the opposite way and over-supplement in some cases. That said, I don't think kelp or its 'super' nutritious alternatives, nettle or hemp for example, can really be considered overdoing it nutritionally when the rest of the diet is mainly comprised of natural fodders like insects and pasture they forage.

I'd absolutely love to see a comprehensive study on how chickens in the wild obtain their complete nutrient spectrum; I'd like to try to emulate those conditions (yes I'm aware it wouldn't support commercial type layers or meat birds) or at least try to find what more domesticated chickens survive on when feral. Clearly they manage and I suspect to an often very efficient degree once sufficient generations have elapsed. Heritage breeds in particular contain a few which were known for large output on more natural diets than their modern counterparts, it's clearly doable.

Mongrel genetics from farms where they had to make shift for themselves I have found incredibly feed efficient, as compared to birds I've bought from breeders who basically inhale food like it's air compared to the mongrels. Productivity has remained quite standard across the board though, regardless of intake; hence my statement that commercial birds in my experience are drastically feed inefficient, which is directly contrary to what many others believe (in many cases though I think the others are just going from what the brochure says and they have no actual experience with the feed efficiency discrepancies between mongrels vs commercials). I've seen a breed advertised as feed efficient when it ate no less than twice or even thrice the amount the average other type of chook required; yeah, maybe a hundred generations ago, that was a feed efficient breed, lol... Wonder how often they're re-evaluated. It's supposed to be ongoing but often isn't.

I do believe disease resistance and feed efficiency are interlinked in many cases and ways, and I also believe the more natural the nutrients, the better. I've never seen any information contradict that, but I've seen plenty of verification.

I don't believe commercial diets are correct overall; they're not all the same obviously, some sound great and are clearly far superior to all, when I reference 'commercial diets' I'm thinking of the cheapest high production options, with often synthetic nutrients and oils and low grade bases. Never, ever, seen a fully healthy chicken living on that. Too often I see people look at a pale faced hen and call her face 'bright red', call her shabby and rough feathers 'healthy'... Poetic license, there. Or just ignorance. Red means red, glossy and smooth does not mean rough and ruined... These terms of description are not meant to be 'interpreted', lol.

I certainly agree with the position that breeders would not being doing a breed any favors by over treating.

I am mixed on the bio security position. If I bring new birds in they are certainly quarantined, and they do not get put with the rest of flock afterwards. I do not think that I can expect my flock to be resistant to everything. There is too much out there to consider. Too many possibilities. I do believe that good management (or what I would call it), has to be part of it all.

While I do believe it would be possible to have a flock that is resistant to the majority of diseases, it would have to be a massive flock to allow for losses which occur as disease strains adapt; also, it would take years of careful work and record keeping, testing, introducing diseases, etc; and I don't know how far it could be taken as there are always some diseases which are simply extremely harsh, adapting rapidly, and adaption to one disease can render a bird weaker against another, sometimes.

I don't think resistance to everything is an easy situation to develop and maintain, but I don't think it's impossible; for the average flock owner, though, it probably is for all intents and purposes impossible. Would love to see some scientists work at that, establishing a flock of super-resistant birds...

I will continue to go as I have and make whatever decision I have to make when I get there.

MG and Marek's would be the two that it would be especially nice to see more resistance to.

Agreed. Best wishes.

 

[Northie]

+++++++++++Caution- technical jargon ahead ++++++++++++++

If you run a SNP, single nucleotide polymorphism, on the MHC-B, Major Histocompatibility Complex-B, you'd want B21 haplotype as it helps with MDV resistance. Conversely you wouldn't want B5, B13 or B19 haplotypes as they help with susceptibility. There were 14 haplotypes mapped that were involved with the resistance or susceptibility of various diseases.

Translation: there are tests that can help determine how resistant or susceptible an individual chicken should be.

How healthy it is otherwise, how much contact with the virus and levels of Natural Killer Cells will also make a difference. SNP tests are not available through normal labs but ADOL, the Avian Disease and Oncology Lab, may be able to advise of private companies that run the tests.

++++++++++Back to technical stuff +++++++

The chicken is perhaps the best nonmammalian vertebrate model that has been characterized in terms of the immune response, the genetics of disease resistance and vaccine response, and the genomic structure and function of the MHC. With respect to anti-tumor immunity, studies with chickens have concentrated mainly on immune responses against oncoviruses; this focus has resulted in the development of successful vaccines against tumors.

Particularly interesting is the association of certain MHC haplotypes with resistance to virus-induced malignancies. The first of such association to be described, and still among the strongest known, is the association of the MHC haplotype B with resistance to Marek’s disease . However, particular haplotypes are also associated with resistance of other oncogenic viruses including ALV and RSV. The strong association of MHC haplotypes and resistance to virus-induced malignancies is presumably related to the peculiarity of chicken MHC, which compared to the MHC of typical mammals, is much smaller and simpler, with a different genomic organization. Recombination is rare within the chicken MHC, and this property has been proposed to allow coevolution between interacting genes, such as the class I, TAP1, TAP2 and tapasin genes. A consequence of this coevolution is the expression of a single dominantly expressed MHC class I molecule due to peptide-binding specificity and cell-surface expression level, which determines the immune response to certain infectious pathogens and explain the striking associations with resistance to these pathogens. However, recent genetic studies have revealed that allelic difference of BG1 an IgSF receptor-like protein located in the MHC locus that contains an immunoreceptor tyrosine-based inhibition motif (ITIM) plays a major role in Marek disease and perhaps other oncogene-induced lymphomas. Interestingly, the association of MHC haplotypes with resistance to oncoviruses is not only due to antiviral responses but also to a better ability to control tumors growth and metastasis. Indeed, vaccination with low oncogenic RSV strains induces not only protective immunity but also results in regression of visceral tumors and erythroblastosis induced by RSV. Finally, contribution of non-MHC genes in resistance to viral replication and tumor growth is also documented.

RSV- Rous Sarcoma Virus

This bit is important and can probably explain why some breeds or strains are more resistant and some are exceptionally weak. Glad you posted it! B21 haplotype...

 

[speckledhen]

Yes, really, can't see any way around that, if it's intended to be taken as a fact rather than an assumption. It'd be great if there were affordable tests you could use at home to distinguish between birds and strains of MD, so you could for example know that a given breeder had birds that tested positive to multiple strains of MDV. Even then, seeing them in apparent good health is no guarantee they or their offspring would remain that way, you'd need more controls in place as gjensen's been saying.

As far as my understanding on it goes, there is no resistant breed, only strains. While admittedly my knowledge of breeds is pretty limited, I can't think of a single breed that as a collective whole has been reliably kept under the conditions necessary to ensure they're as resistant as possible. Somewhere, there is always a breeder holed up in their mountaintop fortress so to speak, lol... Resistant strains is as far as it goes.

Best wishes.

I was researching that a bit and I found numerous references to the Egyptian Fayoumis. They are touted to be highly resistant to Marek's as a breed. They are small bodied, hate confinement, prefer to free range for wild forage, fly very well so they are said to be "predator-resistant", a strange term I encountered in my reading about them (never heard that one). They say Leghorns are less susceptible to Marek's but they seem to be going further with the Fayoumis. This breed is pretty well opposite to what I've ever had.

Blurbs about the breed from various sources, first is MyPetChicken catalog:

The breed, through poultry genetics research and anecdotal reports, is thought to be especially resistant to viral and bacterial infections.

Obviously, a bird that pretty much wants to be feral would not be a choice for everyone, but I am finding them more and more interesting, just as I found the Icelandics very interesting.

 

[chooks4life]

I was researching that a bit and I found numerous references to the Egyptian Fayoumis. They are touted to be highly resistant to Marek's as a breed. They are small bodied, hate confinement, prefer to free range for wild forage, fly very well so they are said to be "predator-resistant", a strange term I encountered in my reading about them (never heard that one). They say Leghorns are less susceptible to Marek's but they seem to be going further with the Fayoumis. This breed is pretty well opposite to what I've ever had.

Blurbs about the breed from various sources, first is MyPetChicken catalog:
Obviously, a bird that pretty much wants to be feral would not be a choice for everyone, but I am finding them more and more interesting, just as I found the Icelandics very interesting.

Sounds very interesting, but I'd bet that at least a significant percentage of people who buy that breed will find they're about as susceptible as the next, given the way that many breeder programs are run, especially those run in isolation from the very stimuli required to retain their resistance, and then selected for type alone. Sounds like I should look into them more though, this research mentioned definitely requires investigating.

As for the Leghorns, I've heard that same info from a few sources but don't offhand believe it applies as a universal rule to the breed, only to strains of it. I suspect the origins of that claim re: Leghorns being a resistant breed possibly lie in the fact that MDV resistant strains of White Leghorns were developed decades back for research purposes but also at the same time, in the same research programs, MDV susceptible strains of Leghorns were developed. Since then I think the more resistant strain was used commercially but I haven't heard about anyone actively preserving their resistance in the intervening decades, and certainly when they're all vaccinated anyway it would be nigh impossible to reliably record susceptibility or resistance. I think it's just a marketing gimmick at this point.

I think I linked to the initial research about it... Anyway, it only took them a few short generations to take their resistance or lack thereof in either direction, very strong heritability indeed; about as quick as selecting for temperament has been in my flock. Rapid effect.

It's possible that many resistant strains of Leghorns are getting around commercially, but I doubt it's the majority. But, who knows? I do see healthy looking Leghorns on many farms, overall I do think they're more robust than many of the other common breeds used.

Best wishes.

 

[speckledhen]

I've never had a small bodied LF breed here, only the dual purpose. And every hen here, other than my old hatchery Brahma hen and two, also elderly hens of hatchery parentage, are from heritage lines and breeder type lines of birds. No vaccinated birds, EXCEPT for those last two pullets that I sold at about 18-20 weeks of age for being not right for the direction I wanted to go. They were vaccinated at Mt. Healthy hatchery, so had the "good" vaccine.

Since I never process my birds unless I get a very rare human-aggressive rooster, I ask myself why not have a bird who is small bodied and/or just for eggs. I would pick a Fayoumi over a Leghorn any day, though they are not great layers, just because I have never been partial to all white birds or Leghorns, either one. If I am at the point one day of starting from scratch and ordering direct from a hatchery, which I have NEVER done (hate the thought of the USPS having live animals), I would be tempted to add three or four of the EFs just to see how I like them. None of my birds are what you'd call flighty, though sometimes the Tiny Terrorist verges on that, so it would be an adjustment. I do free range and have no plans to stop so they'd be fine here, I suppose.

 

[chooks4life]

Egyptian Fayoumis do look interesting, but some look decidedly more feral/wild-type than others, which are much more 'hatchery type' if you know what I mean. You probably do. That homogenous look all breeds get when even of vaguely the same general body type, when bred by large commercial hatcheries rather than serious breed enthusiast type smaller hatcheries.

Anyway, for the sake of Marek's resistance, I know the type of EF I'd get, were I so inclined. Some birds, you can practically see the vitality emanating from.

Best wishes.

 

[Northie]

Http://www.ur.iastate.edu/IaStater/1997/may/chicken.html
Looks like they're working at introducing the Egyptian fayoumis genetics to other breeds of chickens.
Encouraging

 

[speckledhen]

Http://www.ur.iastate.edu/IaStater/1997/may/chicken.html
Looks like they're working at introducing the Egyptian fayoumis genetics to other breeds of chickens.
Encouraging

Very interesting, though the article really contradicts the advertised temperament of the Fayoumis. They all say they are NOT aggressive to humans, even the roosters. Have to check up on that more with sources here on BYC who already own them.

I think this is something to watch. We all realize that the more humans play around with anything, the worse (weaker) it gets. Chicken breeds, like dog breeds, are no exception. So something more on the wild side, like guineas, would logically have to be hardier than something more "human created", IMO.

Okay, can I tolerate a flock of Fayoumis and guineas, LOL? Had guineas, loved them, but they did not love my chickens so had to choose at that time.

 

[seminolewind]

Quote:

I have to question the liver, kidney, peripheral nerves, crop proventriculus, sm and lg intestines, pancreas were clean and your necropsy is indicative of Marek's? It sounds to me, a layman, more like cancer. Although Marek's can attack anywhere with tumors, I've only heard of tumors included on the liver and spleen but not inclusive. It sounds weird if it's indicative of Marek's.

Which brings up one other point. Pathologists and necropsies. Of the 3 I have, seems they were done by 3 different people, and 3 different depth of studies. Some are more explicit than others.

 

[speckledhen]

I still do not have a final report, only two marked preliminary. I was going to give them this week and then at the beginning of next, if I have not heard anything back from Dr. Davis, call and check on what the status is. He didn't get back to me on the last two emails, which is unusual, so maybe he's waiting for something definitive to tell me. I'm assuming a lot here, of course.