Genetics, Health And Breeding?

[Eceni]

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Hi again
I got to thinking after my last post and I have some things and a question to throw out here.  The same dog that came up with PRA- I had stopped using this dog even before the PRA- thank God !!  The reasons being several:  All of a sudden I was getting cleft palates like mad ( never in 47 years of breeding had I had one before this)- I had 5 or 6 in succeeding litters, then I got a hydrocephalic puppy and had a few "fading" puppies.  Now it just could have been karma catching up with me- that is a possibility.  The I had a dog go in for a routine vaccination.  Well the IDIOT Vet he was taken to gave a 9 way shot AND a Rabies shot in quick succession.  The dogs' immune system crashed !  The Vet of course mis-diagnosed the problem and started treating him with massive doses of pain meds ( damn- I can't recall the name of the product- starts with a B I think. Help here?????)  Well he got to the point he was skin and bones and couldn't walk on his own.  I insisted the owner bring him to my Vet.  Thankfully he diagnosed the problem and after a long hard road the dog was fine.  I never experienced the same problem in another dog.  But then I never allow two vaccinations to be done at the same time either .

That's the scenario, now here's the question for our Veterinary people.  Do you think it is possible for a dog to be a total genetic nightmare ?  Or were all of these things totally unrelated ?  I know "stuff" sometimes happens, but in this particular case it was like a snowstorm - it just kept coming and coming.

Carol

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​

Carol - hi - I need to look into this further if I'm to be of any real use beyond the rather 'Noddy's guide to CoI' that I was taught and have read up on since (which, I have to say, came mostly from a fairly cynical genetics lecture who was of the opinion that 'responsible line breeding is an oxymoron, but it will keep you in business so don't knock it')

That said - in the world of simple autosomal genes, where everything is dominant or recessive, it takes two to create the genetic print of a pup and any one parent can only be a genetic nightmares if it is homozygous for a dominant gene and passes it on. So in horses, for instance, grey is dominant to all other colours; if a homozygous grey horse mates any other colour of mare, the foal will eventually grey out, whatever colour it starts with (and why would you want to breed something that guarantees to have melanomas by the time it's ten... I have a grey pony and love her to bits, so I'm not one to talk - just that I wouldn't breed from her).

so in this model for your dog to have been a total genetic nightmare all on its own, it would have had to have displayed all of the syndromes you mention - in which case, it wouldn't have been in your breeding programme.

BUT

we're not dealing with a world of single gene autosomal conditions, we're dealing with complex multiples of genes and variable expression which may require environmental triggers in some cases.

I think we can be fairly sure that cleft palate is recessive - but it wouldn't surprise me at all if it were linked to hydrocephalus and while you'd see a cleft palate (tho' perhaps not a partially cleft one? - it would depend on the extent of the defect), there are a number of people, and so perhaps dogs, who are walking round with marked hydrocephaly and only find out about it when, as a year-mate of mine did, they get knocked off their bike and have a brain scan and find they've been top of their year at public school and then vet school while having about an inch of functioning cortex round a very large hydrocephalus. So it might easily be lurking there unseen and be passed on when mated to a bitch with a similar predisposition.

and the immune system is way, way too complex to be driven by a single gene - there will be multiples, all working together, but it does seem that the move to homozygosity is likely to weaken the immune system. I don't know why this should be, but in species after species, it seems to be the case.

so, it would seem to me likely, that it wasn't the dog alone that was the issue, but the combination of dog and bitch(es) which brought together a variety of presumably partially recessive genes which were then homozygous in the pups.

but that's about as far as we can guesstimate.

to do this properly, we're going to have to look at the lines in more detail.

what I wonder is exactly how genetically diverse is the breed? I only have access to the Whippet archive, which may not be representative, but I'm having serious trouble identifying significant numbers of individuals which *don't* have 'Hillsdown Fergal' at least once in their lines and generally multiple times.

please don't inundate me with the dogs that are clear of this line. I'm sure they exist, but it would be a very interesting exercise for those who have access to the records, to look at how many entirely separate lines exist.

m

 

[patsy]

Hi again
I got to thinking after my last post and I have some things and a question to throw out here.  The same dog that came up with PRA- I had stopped using this dog even before the PRA- thank God !!  The reasons being several:  All of a sudden I was getting cleft palates like mad ( never in 47 years of breeding had I had one before this)- I had 5 or 6 in succeeding litters, then I got a hydrocephalic puppy and had a few "fading" puppies.  Now it just could have been karma catching up with me- that is a possibility.  The I had a dog go in for a routine vaccination.  Well the IDIOT Vet he was taken to gave a 9 way shot AND a Rabies shot in quick succession.  The dogs' immune system crashed !  The Vet of course mis-diagnosed the problem and started treating him with massive doses of pain meds ( damn- I can't recall the name of the product- starts with a B I think. Help here?????)  Well he got to the point he was skin and bones and couldn't walk on his own.  I insisted the owner bring him to my Vet.  Thankfully he diagnosed the problem and after a long hard road the dog was fine.  I never experienced the same problem in another dog.  But then I never allow two vaccinations to be done at the same time either .

That's the scenario, now here's the question for our Veterinary people.  Do you think it is possible for a dog to be a total genetic nightmare ?  Or were all of these things totally unrelated ?  I know "stuff" sometimes happens, but in this particular case it was like a snowstorm - it just kept coming and coming.

Carol

<{POST_SNAPBACK}>

​

Carol - hi - I need to look into this further if I'm to be of any real use beyond the rather 'Noddy's guide to CoI' that I was taught and have read up on since (which, I have to say, came mostly from a fairly cynical genetics lecture who was of the opinion that 'responsible line breeding is an oxymoron, but it will keep you in business so don't knock it')

That said - in the world of simple autosomal genes, where everything is dominant or recessive, it takes two to create the genetic print of a pup and any one parent can only be a genetic nightmares if it is homozygous for a dominant gene and passes it on. So in horses, for instance, grey is dominant to all other colours; if a homozygous grey horse mates any other colour of mare, the foal will eventually grey out, whatever colour it starts with (and why would you want to breed something that guarantees to have melanomas by the time it's ten... I have a grey pony and love her to bits, so I'm not one to talk - just that I wouldn't breed from her).

so in this model for your dog to have been a total genetic nightmare all on its own, it would have had to have displayed all of the syndromes you mention - in which case, it wouldn't have been in your breeding programme.

BUT

we're not dealing with a world of single gene autosomal conditions, we're dealing with complex multiples of genes and variable expression which may require environmental triggers in some cases.

I think we can be fairly sure that cleft palate is recessive - but it wouldn't surprise me at all if it were linked to hydrocephalus and while you'd see a cleft palate (tho' perhaps not a partially cleft one? - it would depend on the extent of the defect), there are a number of people, and so perhaps dogs, who are walking round with marked hydrocephaly and only find out about it when, as a year-mate of mine did, they get knocked off their bike and have a brain scan and find they've been top of their year at public school and then vet school while having about an inch of functioning cortex round a very large hydrocephalus. So it might easily be lurking there unseen and be passed on when mated to a bitch with a similar predisposition.

and the immune system is way, way too complex to be driven by a single gene - there will be multiples, all working together, but it does seem that the move to homozygosity is likely to weaken the immune system. I don't know why this should be, but in species after species, it seems to be the case.

so, it would seem to me likely, that it wasn't the dog alone that was the issue, but the combination of dog and bitch(es) which brought together a variety of presumably partially recessive genes which were then homozygous in the pups.

but that's about as far as we can guesstimate.

to do this properly, we're going to have to look at the lines in more detail.

what I wonder is exactly how genetically diverse is the breed? I only have access to the Whippet archive, which may not be representative, but I'm having serious trouble identifying significant numbers of individuals which *don't* have 'Hillsdown Fergal' at least once in their lines and generally multiple times.

please don't inundate me with the dogs that are clear of this line. I'm sure they exist, but it would be a very interesting exercise for those who have access to the records, to look at how many entirely separate lines exist.

m

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​

A lot of top kennels in the UK have a lot to thank the great stud dog Hillsdown Fergal for. To quote two famous breeders both men of very few words.Denis Meakin and Phil Moran-Healy Stick to your lines and you won't go far wrong, but they did not mean lines with health problems. These tw breeders have stuck to their lines for over forty years, another famous kennel that have consistently line bred from their original two whippets is Peperone.

 

[Seraphina]

I think we can be fairly sure that cleft palate is recessive - but it wouldn't surprise me at all if it were linked to hydrocephalus and while you'd see a cleft palate (tho' perhaps not a partially cleft one? -
m

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​

I thought that cleft palates, as well as other abnormalities, can also be caused by exposure to certain chemicals. Agent orange for one - Vietnam had greatly increased number of cases after the war.

 

[dragonfly]

Cleft palates are a blessing compared to some of the other inherited horrors that lurk below the surface. At least you can see them and deal with them. The ruff or ridge that is present on some whippets is thought to be linked to cleft palates, it is another mid line defect. Giving Folic acid in pregnancy helps to reduce incidence. In my experience not all breeders recognise cleft palates and even fewer admit to them.

Cathie

 

[maggie217]

Could I ask a question please? I have always been in favour of line breeding as long as there is no evidence of problems [health or otherwise] arising in those lines. With line breeding the good characteristics can be strengthened and, of course, there is also the danger of any problems/weaknesses being increased if present. Obviously if problems arise then the breeding programme must be looked at again.

Now I have rambled on my question is:-

If the linebred/inbred strain is free of problems then isn't there a bigger danger of introducing problems if using an outcross where the problems may not be known? In a good, healthy strain isn't line breeding a real benefit, although the gene pool is restricted?

Please excuse my ignorance but I am eager to know what others think as I personally believe in good line breeding.

Pauline

 

[patsy]

Yes, I have said this in an earlier post, if your lines do not have health problems I am all for line breeding. Yes by out crossing you can certainly bring something into your line. Line breeding and inbreeding are two completely different things.

The old dog men always swore that the best puppies came from the sire on the dams side, father to daughter but never mother to son.

 

[whippynit]

Havent got anything to add as im a newcomer to the breed but just want to say still finding all of this very interesting and please keep it all coming!! :thumbsup: :cheers:

Also , on the aspect of linebreeding, outcrossing etc as just raised by Maggie , would i be right in thinking that when you go out to outcross it is still to a dog that is linebred well itself ? Hope ive worded that correctly :b

 

[Eceni]

Could I ask a question please?  I have always been in favour of line breeding as long as there is no evidence of problems [health or otherwise] arising in those lines.  With line breeding the good characteristics can be  strengthened and, of course, there is also the danger of any problems/weaknesses being increased if present.    Obviously if problems arise then the breeding programme must be looked at again.
Now I have rambled on my question is:-

  If the linebred/inbred strain is free of problems then isn't there a bigger danger of introducing problems if using an outcross where the problems may not be known? In a good, healthy strain isn't line breeding a real benefit, although the gene pool is restricted? 

Please excuse my ignorance but I am eager to know what others think as I personally believe in good line breeding.

Pauline

<{POST_SNAPBACK}>

​

I'm not a breeder, so I don't have any particular position to defend, but from a purely genetic point of view, the problem with 'line breeding' is that you breed for phenotype, not genotype

which is to say that you breed on what you can see, not the genetic structure underlying it.

Every animal has two copies of each gene. If both genes are identical, they are called 'homozygous'. If they're not, then they're heterozygous.

in circumstances where there's a single gene - which we believe to be the case for coat colour in horses (I'm picking this because a) it's easy and b) I hope it's relatively uncontentious) - then it is possible to get

1 - a horse which is homozygous for grey and will always throw grey foals,

2 - a horse which is heterozygous for grey - that is, one copy of grey, one of not-grey - and will throw a statistical average of 1 foal in 2 that is grey (50%)

3 -a horse which is homozygous for not-grey (that is, carries no copies of the grey gene) and will never throw a grey foal on its own (of course, if put to a homozygous grey mare, then the mare gives the grey)

so - line breeding/in breeding/incest (the Pharaohs practised this long before anyone knew about genetics) is practised with the intent of moving towards uniformity - that is, animals that will 'breed true.' That uniformity is only achieved by increasing the number of genes that are homozygous on any given allele.

If your basic stock were truly 100% healthy, that would be fine, but the snake in the ointment is the existence of the recessive genes - those genes that, by definition, you can't see until they are homozygous - or, in the case of most of the things we are discussing (because most things are a good deal more complicated than single gene recessive/dominant bases) until an entire gene sequence becomes homozygous.

This is a good site for 'demystifying' Wright's inbreeding co-efficient Inbreeding co-efficients

and this is the paragraph at the bottom that is most relevant (with my added emphasis):

Unfortunately, in the average pedigree, there are a large number of shared ancestors. Therefore, the total inbreeding for a dog cannot generally be calculated manually and appropriate software must be used (e.g. CompuPed). Calculating inbreeding for only the first few generations is not particularly useful. If there are more than one or two common ancestors in four or five generation pedigree, the inbreeding is probably already higher than desirable. Unfortunately, having none is no guarantee that common ancestors will not occur in abundance further back, and some pedigrees of this type still achieve moderately high inbreeding coefficients. Neither can be number of shared ancestors be used as a reliable guide, as the inbreeding coefficient is very sensitive to when and where they occur in a pedigree.

 

This is largely why I started this thread. If there are genuinely breeders who have 'line bred' for 40 years and looking at some of the pedigrees, I can believe it - then it would be useful to know the exact inbreeding coefficients. Sadly, I don't have the necessary software or I'd already be publishing them for some of the lines we're discussing. I may get it, but I have a Mac, and it probably only exists for PCs

Anyway, aside from knowing the numbers just to scare myself with, IF this level of line-breeding is being done safely, then I would dearly like to know the criteria by which people have selected dogs that will not carry recessive genes for any of the list of diseases cited earlier in this thread - or any others that we don't know about that might emerge further down the line.

It's a fascinating concept and if we can find the answer, it'll help a lot of the other breeds and other species where line breeding is causing serious economic upset. Clearly serious and savage culling based on very rigid criteria would make it plausible - it's worked, more or less in the Icelandic horse where a supremely harsh environment has done the effective culling - but finding the life-time criteria by which to cull is the key - and forcing pet owners to neuter their beloved pets must be an interesting experience.

in the meantime, if someone has the necessary access to the pedigrees and wants to work out how many genuinely individual lines there are in whippets, I think it would be an interesting piece of work.

and yes, Agent Orange caused a whole slew of ghastly congenital defects - the damage to a foetus is not always genetic- the Thalidomide catastrophe is another good example - the routes to damage are many, but this thread could expand beyond all coping if we try to go down them all - can we confine it largely to breeding and inheritance? I think that leaves us more than enough to be going on with.

thank you all for your input

m

 

[clayelem]

If these recessive genes are carried then I would think that after a few generations of breeding together those that carry recessive genes,

any problems would have surely arisen.

Personal experience- My whippet bitch( in USA) who was line bred from a line with no defined health problems was outcrossed and we brought in several health issues that were not there before.

I think that our dogs become an extension of our family and we are very protective of what people say about them. When something negative is said, we tend to take it personally. No breeder intentionally tries to breed health problems and we need to get over this protective barrier and be honest about anything that any of our breedings produce and think carefully about repeating the use of any such dogs or bitches. As someone said before, unfortunately many problems don't arise until after dogs or bitches are used. It is a very sad situation, but sometimes whole breeding programs have to be scrapped for the sake of the breed.

 

[patsy]

I am sorry but I have to say that I don't understand half you have written, just some and I am sure that goes for most of ordinary whippet breeders on this thread.

I have written a book on the breed and prided myself that it was easy to read, and the novice could enjoy it. I adore, whippets they have been my life for forty years, apart from the odd missing ball no real problems, they have cost me very little at the vets even in old age. I do care deeply for the breed and feel for breeders who have encountered problems. I was always very sympathetic with Cathie when she had all her problems and really did feel for her. I have never over bred like a lot of the newer people in the breed, and now I feel very happy that I was a sixties babe in the breed, lots of fun many great friends a few are still around today, we retired to the bar after judging talked real dog. I can put my head on my pillow and say I have done my best.

 

[patsy]

If these recessive genes are carried then I would think that after a few generations of breeding together those that carry recessive genes,any problems would have surely arisen.

Personal experience-  My whippet bitch( in USA) who was line bred from a line with no defined health problems was outcrossed and we brought in several health issues that were not there before.

I think that our dogs become an extension of our family and we are very protective of what people say about them.  When something negative is said, we tend to take it personally.  No breeder intentionally tries to breed health problems and we need to get over this protective barrier and be honest about anything that any of our breedings produce and think carefully about repeating the use of any such dogs or bitches.  As someone said before, unfortunately many problems don't arise until after dogs or bitches are used.  It is a very sad situation, but sometimes whole breeding programs have to be scrapped for the sake of the breed.

<{POST_SNAPBACK}>

​

How very sensible ,completley agree.

 

[UKUSA]

Could I ask a question please?  I have always been in favour of line breeding as long as there is no evidence of problems [health or otherwise] arising in those lines.  With line breeding the good characteristics can be  strengthened and, of course, there is also the danger of any problems/weaknesses being increased if present.    Obviously if problems arise then the breeding programme must be looked at again.
Now I have rambled on my question is:-

  If the linebred/inbred strain is free of problems then isn't there a bigger danger of introducing problems if using an outcross where the problems may not be known? In a good, healthy strain isn't line breeding a real benefit, although the gene pool is restricted? 

Please excuse my ignorance but I am eager to know what others think as I personally believe in good line breeding.

Pauline

<{POST_SNAPBACK}>

​

I'm not a breeder, so I don't have any particular position to defend, but from a purely genetic point of view, the problem with 'line breeding' is that you breed for phenotype, not genotype

which is to say that you breed on what you can see, not the genetic structure underlying it.

Every animal has two copies of each gene. If both genes are identical, they are called 'homozygous'. If they're not, then they're heterozygous.

in circumstances where there's a single gene - which we believe to be the case for coat colour in horses (I'm picking this because a) it's easy and b) I hope it's relatively uncontentious) - then it is possible to get

1 - a horse which is homozygous for grey and will always throw grey foals,

2 - a horse which is heterozygous for grey - that is, one copy of grey, one of not-grey - and will throw a statistical average of 1 foal in 2 that is grey (50%)

3 -a horse which is homozygous for not-grey (that is, carries no copies of the grey gene) and will never throw a grey foal on its own (of course, if put to a homozygous grey mare, then the mare gives the grey)

so - line breeding/in breeding/incest (the Pharaohs practised this long before anyone knew about genetics) is practised with the intent of moving towards uniformity - that is, animals that will 'breed true.' That uniformity is only achieved by increasing the number of genes that are homozygous on any given allele.

If your basic stock were truly 100% healthy, that would be fine, but the snake in the ointment is the existence of the recessive genes - those genes that, by definition, you can't see until they are homozygous - or, in the case of most of the things we are discussing (because most things are a good deal more complicated than single gene recessive/dominant bases) until an entire gene sequence becomes homozygous.

This is a good site for 'demystifying' Wright's inbreeding co-efficient Inbreeding co-efficients

and this is the paragraph at the bottom that is most relevant (with my added emphasis):

Unfortunately, in the average pedigree, there are a large number of shared ancestors. Therefore, the total inbreeding for a dog cannot generally be calculated manually and appropriate software must be used (e.g. CompuPed). Calculating inbreeding for only the first few generations is not particularly useful. If there are more than one or two common ancestors in four or five generation pedigree, the inbreeding is probably already higher than desirable. Unfortunately, having none is no guarantee that common ancestors will not occur in abundance further back, and some pedigrees of this type still achieve moderately high inbreeding coefficients. Neither can be number of shared ancestors be used as a reliable guide, as the inbreeding coefficient is very sensitive to when and where they occur in a pedigree.

 

This is largely why I started this thread. If there are genuinely breeders who have 'line bred' for 40 years and looking at some of the pedigrees, I can believe it - then it would be useful to know the exact inbreeding coefficients. Sadly, I don't have the necessary software or I'd already be publishing them for some of the lines we're discussing. I may get it, but I have a Mac, and it probably only exists for PCs

Anyway, aside from knowing the numbers just to scare myself with, IF this level of line-breeding is being done safely, then I would dearly like to know the criteria by which people have selected dogs that will not carry recessive genes for any of the list of diseases cited earlier in this thread - or any others that we don't know about that might emerge further down the line.

It's a fascinating concept and if we can find the answer, it'll help a lot of the other breeds and other species where line breeding is causing serious economic upset. Clearly serious and savage culling based on very rigid criteria would make it plausible - it's worked, more or less in the Icelandic horse where a supremely harsh environment has done the effective culling - but finding the life-time criteria by which to cull is the key - and forcing pet owners to neuter their beloved pets must be an interesting experience.

in the meantime, if someone has the necessary access to the pedigrees and wants to work out how many genuinely individual lines there are in whippets, I think it would be an interesting piece of work.

and yes, Agent Orange caused a whole slew of ghastly congenital defects - the damage to a foetus is not always genetic- the Thalidomide catastrophe is another good example - the routes to damage are many, but this thread could expand beyond all coping if we try to go down them all - can we confine it largely to breeding and inheritance? I think that leaves us more than enough to be going on with.

thank you all for your input

m

<{POST_SNAPBACK}>

​

Like Patsy you had my undivided attention for the first part, after that I kinda of drifted off into the "what shall I do for tea?" zone. I really do want to understand but Im afraid that I need it spelled out to me in words that do not have me running for a dictionary.

Nicky

 

[dragonfly]

The kennel club are always keen to stress their credentials as promoters of the healthy pure bred dog so I would love to know why they allow ANY mating to be registered.

Sister x Brother, then lets take the progeny and mate it back to the

Mother. No problem just send the form in, pay the money and there are your registered pedigree puppies.

Any level of inbreeding is acceptable to the register, even though it is well known that this sort of mating is the most likely to produce dogs with inherited defects of many types. They are in the dark ages, in other countries breeders are at the very least discouraged from matings which exceed a certain COI.

When will the kennel club wake up to the problems they are fostering. More than any other body they could help to preserve a future for pure bred dogs, so why don't they bother?

Cathie

 

[Eceni]

Like Patsy you had my undivided attention for the first part, after that I kinda of drifted off into the "what shall I do for tea?" zone. I really do want  to understand but Im afraid that I need it spelled  out to me in words that do not have me running for a dictionary.Nicky

<{POST_SNAPBACK}>

​

Damn, I thought this was about as clear as it gets.... OK, I'll go away and think about it - the problem is that if I start getting too generic, we lose the precision, but maybe we don't need that.

bottom line:

line breeding is based on what you can see in a dog/bitch

It's what you *can't* see that causes the diseases we've been talking about - when all the recessives come together - but you didn't know they were there because they were recessive and so hidden

which is why it's generally not the case that you 'bring in ill health' by outcrossing to another (inbred) line - it's more that the match between the two lines shows up disease that was already there in both

does that make more sense?

would someone else like to help here?

m

 

[~elizabeth~]

which is why it's generally not the case that you 'bring in ill health' by outcrossing to another (inbred) line - it's more that the match between the two lines shows up disease that was already there.

And can there really be such a thing as a true out-cross within a breed that has had a closed gene pool for several decades? They dogs from so-called healthy lines share the same common ancestors as those that have had problems.

 

[Eceni]

which is why it's generally not the case that you 'bring in ill health' by outcrossing to another (inbred) line - it's more that the match between the two lines shows up disease that was already there.

And can there really be such a thing as a true out-cross within a breed that has had a closed gene pool for several decades? They dogs from so-called healthy lines share the same common ancestors as those that have had problems.

<{POST_SNAPBACK}>

​

That's what I was asking earlier on - and perhaps it's better that we abandon my efforts to present a users guide to genetics because clearly I haven't got what it takes

what matters is that breeders can create a healthy gene pool - which would mean finding out how many distinct and healthy lines there are within the whippet as a breed and then how to progress from there.

to do that, we'd need

a) to examine the pedigrees of all the lines

and

b) to have a detailed health survey to find out what's out there and what lines it's linked to

m

 

[dragonfly]

and now I feel very happy that I was a sixties babe in the breed, lots of fun many great friends a few are still around today, we retired to the bar after judging talked real dog. I can put my head on my pillow and say I have done my best.

<{POST_SNAPBACK}>

​

In a way Patsy has hit the nail on the head there. It was safer to line breed in earlier days, but if you keep doing it forever problems will eventually start to creep in to the breed. Unfortunately breeders weren't warned and they weren't aware of the effects of inbreeding on the long term health of a population. So they did their best with the knowledge they had. I am sympathetic to that and feel that the dog world has been ill served by its governing body who could have made an effort to educate but passed up the opportunity.

I think Patsy did breed in the golden age of pedigree dogs but that age is coming to an end and for a certain future I believe action is needed now. For some breeds it is already too late, don't let whippets be one of them.

I think Manda's post is excellent and it is well worth a good study, it is difficult explaining genetic theory but she's given it a good bash.

Cathie

 

[UKUSA]

Like Patsy you had my undivided attention for the first part, after that I kinda of drifted off into the "what shall I do for tea?" zone. I really do want  to understand but Im afraid that I need it spelled  out to me in words that do not have me running for a dictionary.Nicky

<{POST_SNAPBACK}>

​

Damn, I thought this was about as clear as it gets.... OK, I'll go away and think about it - the problem is that if I start getting too generic, we lose the precision, but maybe we don't need that.

bottom line:

line breeding is based on what you can see in a dog/bitch

It's what you *can't* see that causes the diseases we've been talking about - when all the recessives come together - but you didn't know they were there because they were recessive and so hidden

which is why it's generally not the case that you 'bring in ill health' by outcrossing to another (inbred) line - it's more that the match between the two lines shows up disease that was already there in both

does that make more sense?

would someone else like to help here?

m

<{POST_SNAPBACK}>

​

Thank-you, Im with you now. So if you have line bred for years with no health problems where would the incentive be to outcross and run the risk of a problem popping up?

Nicky

 

[dragonfly]

Like Patsy you had my undivided attention for the first part, after that I kinda of drifted off into the "what shall I do for tea?" zone. I really do want  to understand but Im afraid that I need it spelled  out to me in words that do not have me running for a dictionary.Nicky

<{POST_SNAPBACK}>

​

Damn, I thought this was about as clear as it gets.... OK, I'll go away and think about it - the problem is that if I start getting too generic, we lose the precision, but maybe we don't need that.

bottom line:

line breeding is based on what you can see in a dog/bitch

It's what you *can't* see that causes the diseases we've been talking about - when all the recessives come together - but you didn't know they were there because they were recessive and so hidden

which is why it's generally not the case that you 'bring in ill health' by outcrossing to another (inbred) line - it's more that the match between the two lines shows up disease that was already there in both

does that make more sense?

would someone else like to help here?

m

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Thank-you, Im with you now. So if you have line bred for years with no health problems where would the incentive be to outcross and run the risk of a problem popping up?

Nicky

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If you line breed for years you increase the likelihood that you will be producing homozygous characteristics until eventually you get a problem one. In a way a slow road to hell! In any case I don't really see how you can possibly line breed for years without out crossing unless you had your own mini population. That begs the question what is an outcross? One different dog somewhere once in a pedigree can be an outcross.

It is fascinating.

Cathie

 

[Eceni]

It's what you *can't* see that causes the diseases we've been talking about - when all the recessives come together - but you didn't know they were there because they were recessive and so hidden
m

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Thank-you, Im with you now. So if you have line bred for years with no health problems where would the incentive be to outcross and run the risk of a problem popping up?Nicky

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there probably isn't any providing you can keep culling out the ones where there is a problem so that you only breed for health and/or if you can identify the potential auto-immune problems before they arise and weed them out

This was my question in my opening post... how do you as breeders identify which dogs/bitches are the ones which carry the healthy recessives, when all you can see is what's there in front of you?

To answer more broadly, I was taught that 'responsible line breeding is an oxymoron' on the basis that experience with just about every other species says that without savage culling (such as happens in lab mice) extensive line breeding leads to a whole slew of problems from reduced milk yield and subfertility in Holstein cows to small litters in pigs and reduced immunity in sparrows...

so it's a genuine question. I'm entirely prepared to believe that experienced line breeders know what they're doing and can avoid the pitfalls. Actually, I very badly want to believe it because all the dogs I've looked at and lusted over have been extensively line bred. I just want to know how it's done and what criteria are used?

m