Perro's nesten - English
All animals have immune systems to fight infections and get rid of foreign material. All mammals have a group of genes which we call the MHC, the Major Histocompatability Complex. The MHC is the first part of this immune response and reacts to destroy viruses and bacteria to keep the animal healthy.
There are many versions of each of the genes that make up the MHC. In natural populations for instance, in human beings, there is a large and healthy variety of these collections of genes to give a wide range of possible responses to diseases. It is this that lets us develop immunity to various different flu viruses.
The MHC group of genes sit closely together on one chromosome and stay together during the fertilisation, where as normally each gene pair are split individually and either gene is passed to the offspring. The MHC genes make up a specific group and the whole group is inherited as an unchanged collection of genes to the offspring: another name for this group is an MHC-haplotype. Every mammal inherits two haplotypes: one from his mother and one from his father. There is evidence that if these are different from each other then the offspring has more options to fight off diseases (this is called “heterozygous”) and helps ensure a well functioning MHC enabling the animal to endure stress or vaccinations or sickness in a appropriate way.
In pedigree dogs we find certain limitations in the variety of MHC-haplotypes due to selective breeding both from wolves to dogs and then into specific dog breeds. The Nova Scotia Duck Tolling Retriever has eleven different ones which places it in the middle of the variety range as some breeds are left with two haplotypes and a few have more than 20! Unfortunately nine of the eleven haplotypes are relatively rare and two are very common – perhaps even overused.
In Finland, Sweden and the United States of America there is currently a lot of research into the role of the MHC-haplotype in the occurrence of auto-immune diseases. The picture changes as knowledge is gained and unfortunately it will take some years to really have clarity of understanding. It is clear that other genes are also involved than just the MHC-haplotypes. At present to inform our breeding we can test the haplotypes of our Tollers, but we do not yet know exactly how these will reflect in the outcome of our breeding: we do know that some genetic diversity will be maintained.
It is interesting to note that Tollers are used in this research as they have similar auto-immune responses to humans for rheumatic diseases, Addisons disease and skin allergies.
Some breeders have decided to keep the diversity of the MHC-haplotypes intact and to see how this reflects in the health of their breeding. And I have decided to join them and see what I can contribute.
Our reasons for this decision are:
• Our common sense tells us that there is a reason for this diversity in haplotypes in nature
• We believe that the health of our Tollers will benefit from maintaining variety in their MHC-haplotypes
• We want to make sure that as soon as the research can give us results all the eleven haplotypes are still around for all the breeders.
It means for me as a breeder that I want to breed in a way that contributes to the MHC-diversity. I aim to ensure my litters have as wide a MHC diversity as possible. There are always a lot of different things to consider before one can decide about a mating but the prevalence of heterozygous offspring will be high on my priority list.
DLA-Diversity Project in Nova Scotia Duck Tolling Retrievers