Here's a general answer to a number of points above:
The issue of anyone truly knowing if they have 'healthy dogs' for breeding is actually very tricky. The problem is that finding whether one has healthy dogs that could be bred requires years of cavalier breeding experience and knowing the full health and especially heart history of both grandparents and parents. For example, to adequately follow the heart protocol, you need at least five years of information on the parents and grandparents, plus all other health tests on both sides, an understanding of genetics and pedigree analysis. Why?
The genes that control the immune system are passed down together, one set from each parent, they are found close together on the chromosome. When in breeding occurs the chance that a puppy will inherit an identical set of these genes from each parent increases and this cuts the functional ability of the immune system in half and seriously compromises the quality and duration of life for the puppy.
Those of you who have had a Cavalier with allergies with demodectic mange or without the ability to fight off a deadly disease, know the tremendous suffering this involves both for the dog and its owner. So there are environmental reasons for an impaired immune system but the bulk of literature suggests that in breeding plays the greatest role.
As is well known our Cavalier Breed was founded on a small number of stud dogs and to get our breed established Mother was mated to Son, Father to Daughter, Brother to Sister, thus a genetic defect that was very rare in the source population now can be very common in a particular breed, because one or more individuals in the new population carried that defect.
Since there are pedigrees of Cavaliers with in breed coefficients of 44.6% in the 1940's perhaps greater care should be taken by Cavalier breeders when planning their breeding programs and also a study of pedigrees so as to avoid in breeding and paying particular heed to have as many long living Cavaliers in the pedigree background as possible, since those Cavaliers have proved their health status by living to a normal old age.
from:
http://www.cavaliers.co.uk/articles/articleinbreeding.htm
Consider how confusing most of us find inheritence of coat colour (eg which colour matings might produce which colours, and why). Now consider that though it is very complex -- depending on whether coat colours are themselves dominant or recessive, and then whether a given dog, due to its parentage, is carrying dominant and recessive genes for colour (see a chart expressing this here:
http://www.fckc.com/sante/genetique/possibilites.html )-- this is all actually VERY STRAIGHTFORWARD in genetic terms. Health issues, especially some of the major ones in cavaliers, are far more complex and require careful study and health histories of both lines, going back at least 3 and preferably, 5 or more generations. This is because many of these traits are being carried but not expressed -- in other words, your outwardly healthy cavalier may well give ALL its puppies severe early onset MVD or syringomyelia even though he or she does not have or show outward signs of either.
No one but experienced breeders currently keep records to help make such informed decisions. Genetics itself is extremely complicated -- for example, just read this *basic* introduction to understanding breeding coefficients:
http://www.dogstuff.info/playing_coi_sharp.html
and how traits are inherited in dog breeding:
http://www.sheepdog.com/genetics/basics.html
And this good basic intro to genetic issues in breeding:
http://www.el-minjas.com/Dogbreeding.htm
and this basic background article from the famous Dr Gerome Bell:
http://www.spinone.com/akc_chf99/23HealthyBreeding.htm
How many of us could follow these basic recommendations he reprints, for a healthy breeding?
With an established testing program, the breeder can monitor the frequency of the defective gene in the breeding population, and work to decrease the percentage of carriers.
Suggestions to Improved Planned Breedings (by Dr. Carmen L. Battaglia)
Check the following when screening study dogs:
1. Frequency of the desired traits occurring among his ancestors (three generation pedigree)
2. Frequency of the desired traits found among his littermates
3. Number of carriers, affected littermates, and ancestors in his three generation pedigree
4. Number of pups produced with desired traits
Steps to eliminate carriers:
1. Not repeat the breeding
2. Not use the sire/dam again
3. Test the offspring and not breed from carriers
4. Exclude littermates of those affected
5. Not breed to close relatives of those affected
Characteristics of Good Brood Bitches:
1. Whelps naturally without problems
2. Milk supply sufficient to support litter size
3. Encourages puppies to nurse
4. Careful and calm with pups
5. Is attentive with pups
People may think their supposed one-off breeding is 'just for friends' but how many of those friends and family will have just one litter, and on and on... with your original breeding decisions influencing the genes in the breed for decades beyond? The just for friends reason is one of the main ways breeds have already been gradually undermined... til we have the situation today where half our beautiful dogs will have heart murmurs by age 5!
I cannot stress enough that WE have the ability to help the breed's overall health by the decisions we make on who to get our dogs from, and to not breed ourselves. Who would not be ashamed to contribute to the breed's decline in order to breed in an underinformed way ourselves?
Any breeding decisions made in an uninformed way mean many more cavaliers (and a higher likelihood within the immediate litter) who die at age 6 or 7 after suffering thru heart collapse, who end up needing knee surgeries, who have severe syringomyelia, who inherit terrible conditions like curly coat (Alison can tell you how horrific this condition is -- so bad that most breeders will pts any puppy born with it... but how would an inexperienced breeder know to identify this condition? Alison's curly-coat affected dog was a puppy farm rescue. While she was forced to have many litters, no one understood she had this and she probably sent many litters of puppies out to unsuspecting UK owners, all carrying the rare curly coat genes. And I've no doubt many of those piuppies will eventually be bred by home breeders who are enjoying their seemingly healthy dog... and thus the terrible circle widens and widens).
And, here's a really good article to help anyone consider if they want to breed:
http://www.dogstuff.info/to_breed_or_not.html
Finally: One of the main reasons Bruce and I carefully discussed the pros and cons of having his breeding forum here on his two litters was 1) a fear that it might encourage backyard breeding, wieghed against 2) the pleasure it would give so many people, the insights into the complexities and responsibilities that come with breeding, and
the chance to offer people who would love to be part of such a process but responsibly recongise they should not be, an opportunity to vicariously experience a breeding and growth of a litter (or two!!). I know both Bruce and I have hoped that his forum would continue to give positive pleasures and information -- and I hope board members here who are ever tempted to breed might keep in mind all the above points, but also might go back to, and enjoy again, his documentation of his own litters.