The below is going to be very long, but I hope it's helpful!
I understand that health might be impacted if colour is prioritised over other qualities by breeders, but is it possible that even a litter from a well bred, thoroughly health tested pair can have some particolour pups?
It's entirely possible. But it doesn't meant those puppies would be right for you. Every puppy in a litter is very different - which sounds obvious, but just because you want a puppy doesn't mean it's the right choice for you.
My youngest girl is very high energy, high mouthyness (always got something in her mouth), quite submissive and very affectionate with a healthy dose of Golden Retriever typical separation anxiety - perfect, really, as our family dog. But, there were other puppies in the litter who would not have been suited to our family - despite being raised in the same home, in the same way.
On the below:
- Inbreeding coefficient under 5%
- Best / good practice breeder
- Fully health-tested parents
- Age of parents
- How many litters each parent has had. (I see some sires producing dozens of litters, even for best-practice breeders -- is that really in the dog's best interest?)
I would suggest prioritising it like this:
- Good Breeder & Fully Health-Tested parents (the two should go hand in hand)
- Age of the parents/how many litters the bitch has had (no more than two litters for the bitch, no breeding before 3 - ideally - in a large breed dam, and no breeding after 5 years for the dam)
- COI
- How many litters the sire has had.
That's simply because whilst COI is important...you can have perfectly healthy dogs with very high COIs and very unhealthy dogs with low COI. Some of the healthiest dogs of my breed (Golden Retriever) are ones with slightly higher COIs. And genetic health of the parents/grandparents will always trump COI unless the COI is astronomical.
Sires can have dozens, if not 50+ litters. Not so much of an issue in a breed where there's lots of available studs and not an issue at all if that sire is very healthy and being bred with healthy bitches.
Think of it like this: would you rather a dog with more litters, who was the best of his breed for health, or a dog with less litters who was riddled with all manner of diseases?
Can I also ask about hip scores? I know for standard poodles the hip score is important. One best-practice breeder I've seen online has a litter whose parents have scores of 13 and 10. Is 13 too high? I see the grandparents of the one with a 10 had scores of 23 and 10. Does the score change during the dog's life?
It varies breed to breed. Parents scores are probably fine - not ideal, but fine. But the grandparent in question - no. The two scores for the hips should be similar. So 4/5 5/7 definitely not 23/10.
The scores can change during a dogs life - but that's when the dog is young. Big dogs often aren't fully grown (their growth plates don't settle) and don't reach physical maturity to 24 months, or later. The sooner hip scores are done, the better the score will be. It's something that people don't like to readily admit - as it's a practice that several big charities that are involved in dog breeding are known to do - but breeding a dog before their growth plates are 'finished' will always result in better scores.
Personally, I wouldn't go for that litter (sorry - it's easy to find litters when you know what to look for). The dam's mother has no hip scores - and the only reason that's not done in a breed where it's considered essential is because the breeder thinks something bad might turn up. And the sire's father has terrible hip scores. Two grandparents with either bad, or no, hip scores is not good - no matter how good the parents scores might seem. It's entirely possible those puppies might never suffer with hip issues...but with the generational scores I can see, I wouldn't take that risk. Hip dysplasia is painful, life-limiting and expensive to resolve.