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Post by katt on Apr 7, 2014 20:32:29 GMT -5
So I am curious what the breeders on board here think. Studying immunology right now, it is super complicated so I won't go into it in depth, but basically you have special cells called dendritic cells that collect little pieces of pathogens and bring them to lymph nodes to be recognized by special white blood cells called T-Cells. Specific T-Cells recognize the little piece of pathogen the dendrite cell brought it and replicate and then go out and attack the pathogen to get rid of the infection. Part of this process is a protein called MHC in the dendritic cells. The more types of MHC you can make, the wider variety of T-Cells you can make, and the easier you can fight off a wider variety of pathogens.
MHC variations are encoded in your genes, one gene from each parent. People are usually heterozygous for their MHC gene, which in this case means that because they have 2 different MHC genes they can produce a lot more variety of T-Cells than people who are homozygous. So essentially a heterozygous person is able to create an immune response against a much wider variety of specific pathogens. Clearly it is far more complicated than that, but that's the gist of it.
So with that in mind we look at Line Breeding, or inbreeding. Inbreeding typically creates a much higher rate of homozygous offspring than out breeding since you are pulling from the same gene pool. (Which is how certain disorders can be bred in OR bred out). But in regards to the immune MHC genes, increased homozygosity would mean a decreased potential variety of immune response.
I'm curious of breeders' thoughts on this. With ferrets' tendency to collect various illnesses anyways it can be difficult to say based on rates of illness alone, but I wonder if by line breeding to try and exclude certain genetic health disorders or predispositions, one might also inadvertently be breeding lines with a decreased immune capacity due to an increased rate of homozygous MHC offspring.
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Post by bitbyter on Apr 8, 2014 8:18:33 GMT -5
Interesting...something to think about at least.
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Post by Heather on Apr 8, 2014 12:51:09 GMT -5
It is an interesting thought and one that certainly must be considered. One thing to think about is that most breeders who line breed are looking for a specific physical attribute or series of attributes, whether it's colour or size, shorter face or even disposition. The problem about immunity is that this is not something one sees...as in physically sees. Many still consider it the "luck of the draw" and you will hear where a ferret is being bred because that line has been particularly healthy or is particularly long lived. Most who line breed outcross as well bringing in new blood every third or fourth generation. I don't know if that's got science behind it or just observation or just because the "old ones" did it. As science starts to make a larger in-road on breeding we might actually start to see some of the deeper aspects of genealogy applied. We know that certain cancers and lymphomas show up in lines, they're hereditary. The problem is that ferrets are bred in such a fashion that you an have 3 generations on the ground before the lymphoma becomes visible or worse it's a shared stud who has infected not just one breeder's stock but several. This has happened. It is a good possibility that by breeding for a visible attribute we are creating an underlying issue though supposedly this outcrossing is supposed to help remove this. I don't know if it does and I'm sure many aren't as sure about it as they'd like to be.
ciao
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Post by bitbyter on Apr 8, 2014 13:20:37 GMT -5
What about slowing down the breeding Heather? Kits one year and v-hob for two and then back into the breeding rotation? The breeder wouldn't get as many kits but would have a better handle on their health long term.
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Post by katt on Apr 8, 2014 14:18:23 GMT -5
I think the Jill would be too old by then Jason? If she has her first litter at 1, then 2 years off, she'd be 4 for the next litter. If they start breeding at 2, that's be 5 yrs old...
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Post by Heather on Apr 8, 2014 14:18:57 GMT -5
I don't believe in breeding every year and no more than twice in the life time of a jill (many would argue with that). Yes, that would be a solution. Breeding later would also be a solution too. Many breed jills on their first or second season meaning many are breeding at a year old, some sooner (which is wrong, IMO, breeding younger than a year) Jills are sexually mature by a year of age (usually they come into season around 8 to 10 months) but a raw fed jill isn't physically mature until around 18 months. This goes for the hobs too. Many health issues don't rear their ugly heads until adult and often with ferrets they may actually have had been bred and have had a litter by that time. It then becomes an issue if those kits are then bred at a year and by that point in time that jill is producing her second litter. As you can see it can all become a house of cards very quickly depending on your breeding practices. If a hob is high quality and a winning show hob, he may breed multiple litters in a season if he's studded out. The farm ferrets we just won't get into that because the poor jills produce 3 or 4 litter in a year and are "executed" as soon as they stop producing high quantity litters. A breeding jill in a farm never gets to see her third birthday.
ciao
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Post by katt on Apr 9, 2014 4:18:54 GMT -5
How old is too old to breed though? I'd think waiting 2 years, then taking 2 off, and a second litter at 5 (like Jason was saying - just putting ages on it)... 5 seems old for a Jill to be bred considering 5 is "geriatric." 5 years = about 50 in ferret age. What is the age cut off to Stop breeding? Off topic, but I am curious.
RE the immune genes, that's something that may not even show up as a disease really. It Could in theory, but really we're talking more like - these ferrets are better or worse at fighting off ECE and Flu and ear infections etc than those guys. Kind of hard to test.
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Post by Sherry on Apr 9, 2014 8:42:30 GMT -5
Not certain but most seem to not breed a jill after 4 years of age.
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Post by Heather on Apr 9, 2014 14:45:48 GMT -5
Most do not breed a ferret after 4 or 5 over here. They breed them slightly older 5 maybe in Europe but then their average lifespan is older over there too. Bacchus and Enigma (who were an oops litter, they would have and shouldn't have) were born to a jill at 7 yrs. Bev had no intention of ever breeding this jill, she took it on herself to go find a mate. Most jills over here at 7 are no longer even fertile. There is a very small breeding window and back to backs are the most commonly done. Many breeding at a year, two and three, so you can see why, it's very difficult to stop a rolling ball of genetic issues. This was why many of the old timers in the UK who had already destroyed whole lines warned about breeding for fancy. This didn't even go into the hidden issues of genetic predispositions to lymphoma or worse creating cancers that weren't even common to ferrets
ciao
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Post by katt on Apr 10, 2014 1:19:46 GMT -5
Okay, that's about what I thought. I mean 4=40 so it seems too old to breed to me, but I don't know a ton about breeding either.
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Post by katt on Apr 12, 2014 15:49:45 GMT -5
For the scientifically curious I found a good quote in the text briefly describing the molecules I am talking about...
MHC is a molecule on your cells that binds to foreign protein and presents them to the T-Cells in your immune system so that antibodies can be "made" for the foreign protein so that your immune system and better recognize and attack said foreign invader.
"For an individual the advantage of having multiple MHC class I and class II genes is that they contribute to different peptide-binding specificities, allowing a greater number of pathogen-derived peptides to be presented during any infection. This improves the strength of the immune response against the pathogen by increasing the number of activated pathogen-specific T cells."
Individuals who are homozygous for MHC alleles thus do not have this immunological advantage. Inbreeding typically increases the rate of homozygosity for genes.
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Post by Deleted on Apr 19, 2014 4:07:21 GMT -5
It translates to inbreeding depression, unless I've misunderstood. Takes about 5 generations of solid inbreeding (sibling x sibling, nothing less) for young to be visibly affected by such issues, a general lack of vitality & unable to flourish, as their bodies are battling dozens of small infections that they can't beat. You'd have a mortality rate of about 50%-90%. That's where culling comes into it, euthanasia of the suffering kits, as mother nature would do. Most Linebreedings actually never achieve it, because it isn't concentrated enough.
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