When the 20/20 clinic in June was organised I decided that it would be a good idea to work out what it all meant and how different results would affect future matings.

The first thing to get straight was what each Pattern meant.

Pattern A - Clear, the dog has no genes that have PRA thus is unable to pass the defect on.

Pattern B - Carrier,  the dog has only one gene that has PRA so may pass this gene on to it's progeny but this dog will never develop PRA itself.

Pattern C - Affected, the dog has PRA and when older may well lose its sight, it will also pass on one defective gene to its progeny.

Next I worked out possible scenarios of different matings.

The easiest way to do this is to first understand that every dog has 2 genes for PRA, only one gene from each parent is passed onto each pup, but not necessarily the same gene to each pup.  This gives you any of four combinations in any one litter.  For the purposes of the scenarios I wanted to work out, I decided that I would use noughts and crosses.  O being a clear gene and X being an affected gene.

So bearing this in mind:

Pattern A (clear) = OO

Pattern B (carrier) = OX

Pattern C (affected) = XX

So possible matings are:

Pattern A to Pattern A

OO to OO

=

OO OO OO OO

In this mating only O's will be passed onto the pups so ALL pups will be OO (Pattern A).

Pattern C to Pattern C

XX to XX

=

XX XX XX XX

This time only X's will be passed onto the pups so ALL pups will be XX (pattern C).

Pattern A to Pattern C

OO to XX

=

OX  OX  OX  OX

Here the Pattern A parent can only pass on O to the pups and the Pattern C parent can only pass on X to the pups, so this means ALL the pups will be OX (Pattern B).

All the above matings produce a litter of pups that will all be of the same pattern.

The next 3 matings can produce different Pattern pups in any one litter.

Pattern A to Pattern B

OO to OX

=

OO  OO  OX  OX

So now there is two possibilities for the pups.  The Pattern A parent can only pass on an O but the Pattern B parent can pass on either an O or X, so statistically you will bet 50% of the litter being OO (pattern A) and 50% being OX (pattern B).  No Affected (pattern C) can be produced from an A to B mating.

Pattern B to Pattern C

OX to XX

=

OX  OX  XX  XX

This mating is similar to that above in that there is again two possible results fro the pups.  The Pattern B parent can pass on either an O or an X.  The Pattern C parent can only pass on an X, so again , statistically you will get 50% of the litter being OX (pattern B) and 50% this time being XX (pattern C).  So, No Clear (pattern A) pups can be produced from a B to C mating.

Pattern B to Pattern B

OX to OX

=

OO OX XO XX

This mating produces the widest variety of results.  Both parents can pass on either an O or an X, meaning statistically, you will get 25% of the litter being OO (pattern A), 50% being OX (pattern B), and 25% being XX (pattern C).  It has to be born in mind if doing this mating that these are statistics and you may well be unlucky and get more than just 25% affected in your litter.  Yes, obviously it works both ways but do you take that risk? (more on this later).

So from the matings above I can see which are OK and which aren't.  A to A is great and obviously the best mating to do if enough A's come back in the results for us to still have a good sized gene pool.

Other matins that wouldn't produce affected pups were the A to B and the A to C matings, so I could bear this in mind.

Matings that were obvious no-nos were the B to C and the C to C as no clear pups could be produced from these.

The B to B mating I hung a ? over as there's that element of risk.

So all I had to do now was wait for my results!

The next mating I planned was Oby and Indi, I was very excited about this and had been willing Indi to reach the age of two years since she arrived here!  This would be my almost all Pavesi breeding I had been dreaming of as I've loved every Pavesi bred dog I've seen so far.

Then came my results:  I was pleased that out of the 5 I'd tested only 1 was a pattern C, the others were all Pattern B, including Oby and Indi.

So the B to B mating was now pushed very much to the forefront of my thoughts.  Do I? Don't I? My immediate thought was yes it's worth the risk, the statistics are in my favour with only a 25% chance of affected pups, that's only 1 in 4, 2 in 8.  STATISTICALLY!  Statistics are a cruel thing, they are worked out over large numbers of dogs, not just your litter!  You could quite easily end up with all your litter being affected with PRA from this mating, while another litter elsewhere could end up with all clears.  So having thought this through some more I would have to say, no, personally I would not want to take this risk.  PATIENCE IS A VIRTUE, and in 2 matings I can get where I want to be without having produced any affected pups.

For example, if I was to mate OBY (pattern B) to a similarly bred Pattern A bitch, and keep (all being well) a Pattern A dog, I can then mate my new Pattern A dog to Indi (Pattern B).  Thus joining Oby and Indi's lines together without having produced an Pattern C pups.  This obviously works the other way round, if I'd used a Pattern A dog on Indi and kept a Pattern A bitch, etc.

So now your thinking, OK so what if you're worse off and it's a Pattern C you've got to work with?  Right then find a pattern A dog/bitch to mate to my Pattern C.  All you littler will be Pattern B (no need to test, if you don't understand why then you'd better go back to the beginning and read through my notes again).  The Pattern B pup can then be mated to a Pattern A and voila you have a litter of A's and B's in just two matings.

I think these basic thoughts on breeding should be taken into account.

1.  Pattern A stud dog owners:  don't turn down and otherwise exceptional bitch purely because of her eye status.  If she was suitable for your dog before then she is suitable now.

2.  Pattern A bitch owners:  don't disregard stud dogs that are B's or C's.  If he's exceptional quality and you really wanted to use him before then it may well be worth using him the once.

3.  Pattern B or C bitch owners:  don't disregard well bred bitches because of their eyes, there's a whole lot more to her than that.  DON'T FORGET mated to a Pattern A dog she can't produce affected pups.  Don't however, use a dog you would not have considered before.  If you didn't think he would compliment your bitch before then he won't now!  It would just have been a pointless mating.

4.  Everybody:  do try at all costs not to produce affected pups.  Yes, PRA the main is late onset but remember the puppy owner who ends up with the one that loses his/her sight at 6 years old.

I think the DNA test has given us all a valuable piece of information which used sensibly can only be beneficial to the breed (especially since we are all being completely open about our results).  What we mustn't lose sight of (no pun intended!) amongst all this is what is required of our breed in the breed standard it doesn't say "Conformation unimportant as long as the dogs is free of PRA"!

We have to use our B's and C's initially bearing in mind that the A's we have available in this country don't even amount to the number of ACD's I have in my own kennel!  For example, if we were only to use the Pattern A stud dogs then you would end up with a bottleneck effect on our gene pool, meaning that in a very short space of time all ACDs in the country will be very closely related and we'll have no where to go next.  This could easily be very detrimental to the breed in that there are more genes to a dog than just the PRA genes.  It only takes one of these overused stud dogs to pass on a bad gene for another problem and this will then become as widespread as PRA is now and we'll be back where we started, only with something of another name.  The ACD gene pool in Britain has always been relatively small we cannot allow this bottlenecking to happen or all the work over the last 20 years to get where we are today will be lost.  Given time we'll be able to produce clear after clear of the type we wanted before "the dreaded test."

My final thought:

Rome wasn't built in a day and it would never have been built at all it the labourers had been shot!

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