Ichthyosis is a very rare skin condition in dogs that is the result of a recessive genetic mutation. ... Affected skin is rough and covered with thick, greasy flakes that stick to the hair. The term “ichthyosis” comes from the Greek word for fish, as the skin of these dogs resembles fish scales. While it is estimated that more than 50% of Golden Retrievers in Europe are carriers of the genetic mutation responsible of Ichthyosis, a breeder can manage their pairings to completely avoid producing a litter containing affected puppies. For more information on ichthyosis, please visit the Animal Genetics website at www.animalgenetics.us/Canine/Genetic_Disease/Ich.asp
Why You Need Population Genetics: the "Elevator Pitch" by Carol Beuchat, PhD1) All the useful genetic variation your breed will ever have was in the dogs that founded the breed. This genetic diversity is finite. 2) Each generation, alleles can be lost by chance (this is called "genetic drift") and also through artificial selection by breeders, who select for dogs with the traits they like and remove other dogs from the breeding population. 3) Because the stud book is closed, genes that are lost cannot be replaced. 4) So, from the moment a breed is founded and the stud book is closed, loss of genetic diversity over time is inevitable and relentless. 5) You cannot remove just a single gene from a population. You must remove an entire dog and all the genes it has. 6) You cannot select for or against a single gene, because genes tend to move in groups with other genes (this is called "linkage"). If you select for (or against) one, you select for (or against) them all. 7) Breeding for homozygosity of some traits breeds for homozygosity of all traits. Homozygosity is the kiss of death to the immune system. And, as genetic variability decreases, so does the ability of the breeder to improve a breed through selection, because selection requires variability. 8) The consequences of inbreeding (in all animals) are insidious but obvious if you look - decreased fertility, difficulty whelping, smaller litters, higher puppy mortality, puppies that don't thrive, shorter lifespan, etc. Genetically healthy dogs should get pregnant if mated. They should have large litters of robust puppies with low mortality. Animals that cannot produce viable offspring are removed by natural selection. 9) Mutations of dominant genes are removed from the population if they reduce fitness. Recessive mutations have no effect unless they are homozygous. Consequently, rare mutations are not removed; they are inherited from one generation to the next, and every animal has many of them. 10) If you create a bunch of puppies from your favorite sire, you are making dozens of copies of all of the bad mutations in that dog (which were never a problem before because they were recessive; see 9) and dispersing them out into the population. Now, a (previously) rare mutation will become common, its frequency in the population increases, and the chances go up that a puppy will be produced that is homozygous (has two copies of that bad allele) - and homozygous recessive alleles are no longer silent. 11) So, genetic disorders caused by recessive alleles don't "suddenly appear" in a breed. The defective gene was probably there all along. Make a zillion copies, and suddenly you have a disease. 12) Using DNA testing to try to remove disease genes from the breed will not make dogs healthier (see 2, 5, and 6). 13) The breed will continue to lose genes every generation (by chance or selection) until the gene pool no longer has the genes necessary to build a healthy dog. 14) At this point, the breed might look wonderful (because of selection for type), but it will suffer from the ill effects of genetic impoverishment - inbreeding depression, diseases caused by recessive alleles, increased risk for cancer, etc. 15) The health of individual dogs cannot be improved without improving the genetic health of the breed. The only way to improve the genetic health of the breed is to manage the health of the breed's gene pool. 16) Population genetics provides tools for the genetic management of breeds or other groups of animals. Breeders CAN improve the health of the dogs they breed if they understand and use them.
Copyright (c) 2013 Carol Beuchat This document may be reproduced without permission if accompanied by the copyright information.
Last revision March 2015. Excerpt from the Institute of Canine Biology ..... remember that the COI is an estimate of the predicted loss of vigor and general health to expect as a consequence of the expression of recessive mutations. Except during the development of a new breed when you want to use inbreeding to fix type, you should strive to keep inbreeding below 10% to achieve modest benefit with modest risk. Uh-oh. What if the level of inbreeding in my breed is already too high? The closed gene pools mandated by kennel clubs for purebred dogs necessarily result in inbreeding, and in many breeds the average level of inbreeding is already high. This is the reason the occurrence of genetic disorders in purebred dogs is steadily increasing (you can watch the "genetic disorder counter" here) at the same time as lower fertility, smaller litters, and higher puppy mortality are making breeding ever more difficult.
Your first option is to make the best possible use of the genetic diversity that still exists in your breed. Identify lines that are not closely related to yours, and even if those animals wouldn't be your first pick in terms of type, a cross producing a lower COI will be beneficial in the next generation in terms of health. A genetic analysis of your breed's pedigree database can help you find these less related animals using something called cluster analysis. Don't assume that animals from different lines or even in different countries are less related. Calculate the inbreeding coefficient of a potential mating from a good pedigree database that goes back to founders. An "outcross" to a dog that is more related than you realize is likely to produce a litter with lots of nasty surprises.
What if your breed is so inbred that there is nowhere for you to go to find less related animals? Unfortunately, many breeds are facing with this problem. Genetic diversity is unavoidably lost from a breed every generation, and to restore diversity and reduce inbreeding you need a way to put the genes back by breeding to an unrelated dog, probably of a different breed. If your breed is already highly inbred and struggling with significant health issues, this is not a trivial thing to do. The animals to outcross to must be selected very carefully. For example, breeding to another highly inbred dog, even of a different breed, will produce offspring that all have the same alleles for the genes that were homozygous in the parent. The key to managing recessive mutations in any population is keeping them rare, so adding animals to the population that share many of the same mutations is asking for trouble down the road. Also, incorporating new genetic material into the breed will require a well-designed strategy worked out for at least the next 4 or 5 generations. A single crossbreeding followed by sequential backcrossing into the breed will remove most of the genetic diversity you were hoping to introduce. You definitely need to start with a carefully designed plan designed by geneticists with the tools to do it properly.
Avoiding high levels of inbreeding in the first place is much easier than trying to fix things after inbreeding becomes a problem. Breeders should work together to monitor the inbreeding of their breed so they can all benefit from healthier puppies that meet their goals as breeders now and in the future.... If you have questions regarding the COI of our golden retrievers or of planned litters, please contact us. For more information on COI in general, please visit www.instituteofcaninebiology.org/blog/coi-faqs-understanding-the-coefficient-of-inbreeding
A Beginner’s Guide to COIWhat is COI? COI stands for Coefficient of Inbreeding. Essentially, it measures the common ancestors of dam and sire, and indicates the probability of how genetically similar they are. Why should I care? There are consequences to being genetically similar, some good, some bad. The fact that dogs within individual breeds are so genetically similar is what makes them that breed- and why , if you breed any Labrador to any other Labrador, the puppies will look recognisably like Labradors. OK, go on…but please keep it simple.. Many of the 20,000-odd genes that go into any dog of a particular breed are ‘fixed’. That means that every Labrador will have two identical copies of them- one inherited from their dam; one from their sire. Others however, are not so fixed – such as those genes in Labradors that code for colour. That is, Labradors can come in black, chocolate and yellow. Genes always come in pairs. The gene-pair is called an ‘allele’. When the pair is identical, it is called ‘homozygous’. When the pair is not identical, it is called ‘heterozygous.’ ‘Allele’, ‘homozygous’ and ‘heterozygous’ are three good words to understand if you are a dog breeder. Homozygous and heterozygous are terms often used more generally, too, when talking about diversity. The more gene-pairs that are homozygous = less diversity. The more gene-pairs that are heterozygous = more diversity. Geneticists in the main consider diversity a good thing. So not all the pairs of genes are identical? Correct. And this is what gives us variation within a breed. It’s why, as mentioned above, Labradors come in three colours. And it’s also what makes some bigger or shorter or faster or cleverer or more able to withstand disease than others. Of course environment can play a big role too, but the raw potential for every dog lies in its genes. I thought we were talking about COI? Many pedigree breeds are already highly homozygous, ie many of their alleles contain only a single gene type. This means that the characteristics that these genes produce will be the same in all puppies, regardless of which parents from the breed are used (ie no breed diversity) The COI is really just measuring the probability of any individual allele being homozygous due to an identical gene being passed down to the puppy along both the dam and sires lines from single common ancestors. Give us a dead simple example
Breed two completely unrelated Labradors
Mate two of their offspring together
What is the resulting puppies’ COI?
In this instance the puppies’ COI will be 25% – that is, statistically, there is a 25% chance that any allele will contain the exact same gene as a direct result of having common ancestors – in this instance the same grandparents. This is in addition to the levels of homozygosity that would be present in the breed regardless. You say ‘statistically’? Yes, in reality, they could be much more than 25% genetically identical/homozygous – or much less. The only way to know for sure would be to minutely examine every dog’s DNA which would be impossible (at the moment at least). But the statistical likelihood is nevertheless very useful to dog breeders. What about other COI examples? Parent/offspring: 25% Full sibling: 25% Grandparent/grandchild: 12.5% Half sibling: 12.5% Great grandparents/great grandchild: 6.25% First cousin: 6.25% What about other common ancesters? COIs are much more than looking at a dog’s parents. COIs also track how related dogs are further back in the pedigree. Look back 10 generations in our own family trees and you are very unlikely to see the same name twice. This is not true for dogs, though. The same names can appear many, many times. Traditionally, breeders have very commonly used grandfather/grand-daughter matings (and often even closer) to ‘fix’ certain traits. To get a true picture of how inbred a certain dog is, then, you should go back at least five generations and ideally ten. As you go further back, in most instances, the COI is likely to rise. Why are high COIs considered a problem? Two reasons:
Inbreeding will help cement ‘good’ traits but there’s a danger of it also cementing bad ones. In particular, it can cause the rapid build up of disease genes in a population.
Even if a breed of dog is lucky enough to be free of serious genetic disorders, inbreeding is likely to affect our dogs in more subtle, but no less serious, ways.
These include smaller litter sizes, less vigorous/viable puppies, fertility problems and weakened immune systems. These effects have been very well documented in other species and are known as inbreeding depression. Farmers, who used to breed livestock in much the same way as we still breed dogs, have now changed the way that they breed their animals. In fact farmers so recognise the benefit of hybrid vigour that much of the meat we eat, milk we drink and eggs we boil are from crossbreeds. That’s because the yield is likely to be more/healthier/disease resistant than that from purebred stock. A study of Standard Poodles discovered that dogs with a COI of less than 6.25% lived on average four years longer than those with COIs over 25%. Now nothing in genetics is inevitable. There are some examples out there of very inbred populations that appear to be pretty healthy and whose fertility/fecundity have not been affected. But the above effects have been observed far too often to ignore the risk. While a low COI does not guarantee a healthy puppy, a high COI should definitely be a cause for concern. Why bother to check a dog’s COI? As well as limiting further genetic problems, having a low COI may show that the breeder has tried to follow good breeding practice and limit inbreeding. This hopefully will reflect in other good practices such as socialisation and worm control so that your new puppy will be happier and healthier in many respects. How do I check my dog’s COI? You can check your prospective puppy’s COI (or COI of both parents) by going to the Kennel Club’s online Mate Select programme: Link to Kennel Club Mate Select programme Breed Average COI These vary enormously. A recent study carried out by Imperial College showed breed averages for the 10 breeds studied of around 4%. Within each breed though, there were enormous differences, with many dogs in the KC database with COIs over 25% (the equivalent of a mother/son mating) Important Caveat COIs are not the be-all and end-all of a dog. They’re just one measure. So don’t freak out if you discover your dog has a ten generation COI of 30%. Likewise, if your dog has a COI of only 1% it does not guarantee his health and fitness but his chances of having inherited a double dose of defective genes is far less. And… The breed average COIs given on each of the breed pages are those provided by the Kennel Club’s Mate Select online facility. The KC say that these are based on their pedigree records as far back as they go. Electronic records go back as far as 1982 and consist of, on average, 10 generations of pedigree ancestry. However, the records do not take into account the number of ‘founders’ for each breed, which in many cases is a small number of dogs. The COI breed averages are updated annually. How the Kennel Club calculates the COIs Information may be found here: Link to Kennel Club Inbreeding article Written by Jemima Harrison
While the OFA recommends a Echocardiography exam as the definitive diagnosis for Congenital Heart Disease (CHD), they also provide the following: Cardiac Guidelines for Breeders A careful clinical examination that emphasizes cardiac auscultation is the most expedient and cost-effective method for identifying Congenital Heart Disease in dogs. While there are exceptions, virtually all common congenital heart defects are associated with the presence of a cardiac murmur. Consequently, it is recommended that cardiac auscultation be the primary screening method for initial identification of CHD and the initial classification of dogs. Murmurs related to CHD may at times be difficult to distinguish from normal, innocent (also called physiologic or functional) murmurs. Innocent cardiac murmurs are believed to be related to normal blood flow in the circulation. Innocent murmurs are most common in young, growing animals. The prevalence of innocent heart murmurs in mature dogs (especially in athletic dogs) is undetermined. A common clinical problem is the distinction between innocent murmurs and murmurs arising from CHD. Of course, wanting to make sure we are performing the "best" diagnosis for our golden retrievers, we reached out to the Purdue University College of Veterinary Medicine to schedule to have our dogs tested. Imagine our surprise when informed the process they follow consists of a Cardiac Auscultation and only proceeds to the Echocardiography IF there is an abnormality detected in the cardiac auscultation. Therefore, since our dogs have already passed their cardiac auscultation we are not rushing out to have then radiated without cause. If you have questions on our rationale, please feel free to contact us. If you would like to review the OFA guidelines we've referenced, please visit their website www.ofa.org/diseases/other-diseases/cardiac-disease#cardiacexam