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There are a lot of different disorders that can be found in sheep, some more common than others. In Norway these disorders has been described in literature as common disorders: - Spider Lamb Syndrome (SLS) - Cryptorchidism - Inverted eyelids, also called entropion. - Brachygnathia - Cleft palate - umbilical/abdominal and scrotal/inguinal hernias - Antresia ani - Microtia - rectal prolapse - microphtamia Most inherited disorders are recessive in nature. That means that for the animal to get the disorder, two copies are needed. The animals having one copy are carriers. Recessive disorders are especially important when there are few animals (small genome). It is also important when there are a small number of animals used to improve the production, like in selection.

This dissertation is a prospective study of a large group of privately owned dogs of three Hungarian shepherd breeds. The dissertation provides an overview of the current understanding of canine hip dysplasia, it highlights the characteristics and latest research within this field. It explains the methods of early detection of inherited genes as well as the ways to prevent the disease from developing in future breeding dogs. The data analysis evaluates the various aspects of the Norberg angle in three Hungarian dog breeds: Mudi, Pumi and Puli. In addition to this it presents the incidence, level of hip dysplasia (HD) and the predisposition in the mentioned breeds in relation to influencing factors such as gender, age, kennel, breed, owners gender, location code and year of birth. The investigation showed that in Mudi, Pumi and Puli the incidence of hip dysplasia is highest in category “A Free”, where 23 Pumi, 98 Puli and 41 Mudi dogs were categorized. This equates to 32%, 50.7% and 64% respectively. Dogs grouped as borderline (B) were 15 Pumi, 47 Puli and 14 Mudi, thus 20.8%, 24.3% and 21.8% accordingly. This decreasing trend of HD incidence continued with 29.2%, 16.5% and 4.7% of the dogs being regarded as mildly (C) affected, 15.3%, 6.2% and 4.7% classified as moderately affected and with 2.7%, 2% and 4.7% of the dogs regarded as severely affected. This showed that Pumi was the upmost-predisposed breed out of the three. When comparing the expected and observed values of level of HD, the difference between expected and observed values showed that 4 out of 5 levels of HD were statistically significant. Thus, for category B, C, D and E there was a high discrepancy between the expected and observed values, indicating that observed values (obtained by veterinarians and clinicians) tended to underestimate the actual severity of the various levels of HD. In all conclusion: there were no significant impacts on the Norberg angle found in our data set, with the exception of breed and kennel. None of the three Hungarian shepherd breeds are significantly more or less predisposed to HD than any of the other small and large breeds. We confirmed that environmental factors like kennel, thus feeding, raising and keeping conditions adds to the already predisposed dog and makes the manifestation of the disease even more unpredictable.

The Dachshund is a breed that has existed for several centuries. It was originally used as a hunting dog, but later it became more and more popular as a pet. It is a chondrodystrophoid breed, which means that it has been selected for a genetic form of dwarfism. The discs in chondrodystrophoid dogs are prone to early degeneration and calcification. The Dachshund is more prone than any other chondrodystrophoid dog to IVDD and calcification, and Hansen suggested in 1952 that the Dachshund is genetically predisposed for this condition. Several studies have been done to confirm Hansen’s theory. The results of these studies indicate that the Dachshund is genetically predisposed for disc degeneration and calcification. It is the breeders’ responsibility to exclude those dogs with early calcification from the breeding programs.

This work presents the nine breeds of draft horses that find their origin in France. Most of them have evolved from indigenous horses found in the different regions of France and are often well adapted to the particular climate and geography of the given regions. Just like in all developed countries, horses are not used as much as they once were before the apparition of cars and tractors. Therefore the horse population is greatly reduced when compared to times before the industrial revolution. This is especially true for the draft horse. We look into the evolution of breeds throughout History and how the draft horse adapted to the needs of the people. The evolution of draft horses closely follows the evolution of man made technologies. This explains why there aren’t as many draft horses nowadays as in the past. However draft horses are a sympathetic image for the public, who is reluctant to see them disappear completely. There still are passionate breeders and associations that wish to preserve those breeds the best they can. It has to be noted though, that preservation of all these breeds is very costly since no breeder can live solely from the breeding of horses, therefore it is worth wondering if it is wise to make such high preservation efforts on all of the nine breeds or if we should rather focus on some breeds and let others fade out. There are indeed some breeds that are genetically very close to each other, and on the contrary some breeds that have a quite unique genetic background.

The aim of the study was to perform a review study regarding breeding measures to reduce the prevalence of bone spavin in the domestic horse. Bone spavin is one of the most common forms of hind limb lameness in the horse (GOUGH and MUNROE, 1998). The cause of bone spavin is of multifactorial origin, and both inherited poor tarsal conformation, special types of work, injuries, trauma and genetic predisposition are factors contributing to the disease. The articles on bone spavin in this thesis were mostly done on specific horse breeds. Bone spavin is described as a disease commonly occurring in all horse breeds including ponies, but may more frequent be seen in some breeds as the Icelandic horse. Osteoarthrosis in the distal tarsal joints, bone spavin, is a well known condition which is common in Icelandic horses age 6-12 (BJÖRNSDÓTTIR et al. 2004) The Icelandic horse in Iceland is considered to have been pure for 1000 years as importation of horses to Iceland is not allowed according to the Icelandic law. Even though the number of horses on Iceland is quit large inbreeding still comes to thought. Inbreeding is a system of breeding in which related animals are mated and even though it is not a system used on Icelandic horses where the breeding is regulated by the Farmers Association of Iceland and monitored by the studbook World Fengur it is known that inbreeding increase the risk of genetic disorders. The whole equine genome scan was completed in 2007 and has made it possible to investigate genomic areas holding genes for specific diseases. Several disorders of multifactorial origin has been revealed on chromosome-wide quantitative trait loci. This has not yet been the case for bone spavin, but research is continuously progressing. Björnsdóttir et al concluded in 2000 that the prevalence for bone spavin could be reduced by breeding selection based on flexion test of the tarsus and radiology of the joint. In 2003 she studied the culling rate and revealed that bone spavin affects the duration of the use of the Icelandic horse. By performing a high detailed radiography and histology on the centrodistal tarsal joint of Icelandic horses age 6 months to 6 years she concluded that poor conformation and joint architecture seemed to be the cause of bone spavin rather than trauma and overloading in 2004. Stock and Distl studied the prediction of breeding values of several important joint pathologies on the Hanoverian Warmblood horse and indicated that it is possible to simultaneously consider health and performance traits. In 2006 the same researchers studied the genetic correlations between the same joint pathologies and concluded that genetic correlation between radiological health traits deserve close attention in horse breeding. Bone spavin does not necessarily have to end your horse's performance career, but they certainly require careful attention and care. Every horse and situation is different, so you will need to work with your veterinarian (KING, M. 2003)

Large breeds like the Great Dane are known to be predisposed to diseases like Hip dysplasia, Gastric dilational volvulus, and Dilated cardiomyopathy, which are associated with high veterinary costs, sudden death and low average age. There is no doubt that these are remarks of importance in the breeding of the Great Dane. Less common diseases are often overshadowed by these common ones, and therefore easier forgotten. Colour dilution alopecia, congenital sensorineural deafness and lethal white homozygous harleqins are all related to different colour genes such as dilution of black, piebald, merle and harlequin. Breeders have selected for specific colours and spotting according to the standards since the breed standard first were written. Since then genes involved in pigmentation has been revealed, and it is now possible to DNA testing what kind of colour genes dogs are carrying There are few acceptable colours in the Great Dane, and most of the dog population carries one or more of these genes that have been associated with diseases, making them highly relevant in the breeding of this breed, and expecially in case of harlequin breeding in which all of the above mentions colours are involved.

Cutaneous asthenia, also known as hyperelastosis cutis is an inherited congenital skin disorder that has been reported in a variety of species, characterised by skin hyperextensibility. This degenerative connective tissue dysplasia of friable, thin, hyperelastic skin was first described in Quarter horses in 1978 by Lerner and McCracken as Hereditary equine regional dermal asthenia (HERDA). The clinical symptoms of HERDA typically present on average, at 1.5 years of age and are frequently associated with the introduction of the saddle and riding. It primarily affects the dorsal region of the body and manifests as extremely loose, hyperextensible, fragile skin that tears easily and upon stretching does not return to its normal position. Single or multiple seromas and haematomas develop leading to chronic slow healing ulcers with sloughing of the skin and atrophic scar formation. This debilitating disease is found predominantly in Quarter horses, with the highest incidence seen in the cutting horse subpopulation, however cases in other breeds have also been reported. HERDA is an inherited autosomal recessive skin disorder that almost exclusively has been found in Quarter horse lineage tracing to the famous stallion “Poco Bueno”. The genetic defect responsible for this disorder is a missense mutation in the equine genome cyclophilin B (CypB) where a Gly-6 to Arg-6 substitution at codon 115 has been identified. It is believed this mutation alters protein-protein interactions of CypB and delays the triple helix folding of collagen. Research has indicated that this CypB mutation is responsible for alterations in diverse tissues containing fibrillar collagen, thus suggesting the HERDA phenotype is not limited to the skin. Since the mapping of the horse genome sequence was completed in 2007, the genetic basis for many hereditary diseases has been discovered and diagnostic tests have been developed and are available to the public. Further to this, the first sequencing of a Quarter horse genome by next generation sequencing in 2012, has led to an increased quantity of genetic variants for use in equine genomics which will provide advantageous resources for future equine genetic studies regarding performance traits and diseases. In an effort to control further manifestation of HERDA, it would be extremely beneficial for owners and breeders to become more informed about this genetic disorder in the horse and take the necessary precautionary steps in order to selectively avoid the further production of affected foals. Mandatory testing for genetic diseases such as HERDA is not the standard among breed registries around the world, with the exception being the Australian Quarter Horse Association (AQHA). Consequently, by availing of the genetic screening against this disorder and by careful selection of breeding stock, it may be possible to slowly reduce and even eliminate HERDA from the horse population in the future.

Dog breeding should be assessed and investigated from several aspects in order to gather a complete and comprehensive overview of the breed in question. It is essential to perform a proper background check of the breed in order to understand its history, origin of purpose as well as current strengths and weaknesses, before starting the breeding new progenies. Not only should a dog remain healthy, but its basic breeding goals regarding conformation and working abilities should also be maintained.

The Quarter horse is an American breed, and is today the largest registered breed in the world with. Worldwide there are over 5 million registered Quarter Horses. It is one of the oldest recognized breeds in the United States. The breed originated in the early 1600 as a cross between the English Thoroughbred and native horses of Spanish origin. The name originate from their ability to run a quarter of a mile faster than any other breed, hence the name, the Quarter Horse. Although the breed has existed for 400 years, the breed registry only began in 1940. Today the American Quarter Horse is known as a good racehorse, and for its outstanding performances in western disciplines. Their conformation and mind makes them well suited for the quick maneuvers required in cutting, barrel racing, reining and as a working cow horse. The breed is also shown in English disciplines.

The elegance and temperament of the Arab horse has been fascinating people for decades and turned the Arabian into a very popular breed. The value of these horses is not only of economic but also emotional importance since these horses are outstanding companions for every horse owner. This work will give an insight into the genetic disorders that endanger the sound breeding of Arabian purebreds and will show the most recent developments in managing, and hopefully eradicating, genetic related diseases of the Arab horse.

Merle pattern coats in dogs has been described from centuries in many breeds of domestic dog. Until recently the reason some dogs were born with this unique and beautiful pattern was a mystery. In fact it was not until 2005 that Clark et all discovered that retrotransposon insertion in SILV is responsible for merle patterning in the dog. Even more recently it has been discovered through new research that this mysterious merle gene is not only responsible for dilution patterns but also for many auditory and ocular disorders. These disorders appear to range from rare and mild in heterozygous merles to severe and debilitating in homozygous merles. During this thesis my aim was to discover exactly what unwanted hereditary complications are caused by the merle gene and their prevalence in the breeds associated with natural occurring merle patterns. Furthermore I was interested in determining what precautions if any are possible to implement to avoid merle dogs suffering from these hereditary diseases associated with the gene.

The Irish Draught is an animal that is deeply entrenched in the history of Ireland. From its original use as all purpose animal on the farm to the modern horse we see today, the Irish Draught has earned its right to be protected and bred long into the future. As we have already discussed though the breed has had its difficulties, it has prevailed through its turbulent past. With the new methods of inspection, stricter inspection processing for stallions and a new classification style for mares and stallions breeders can now look forward to making the most informed and best breeding decisions regarding their horses into the future. However, I believe further systems must be put in place if the Irish Draught is to have a future. With such a small gene pool and the Irish Draughts questionable ability to compete with other breeds at the top level of all equestrian competition leaves this breed in jeopardy. The “jack of all trades” aspect of the breed that served it well when it was a farm horse is in fact detrimental to its survival into the future. It is this inability to compete with more athletic breeds that cause it to be viewed by many only as a foundation breed for the further development of the ISH. Ideally there should be further research done into indentifying future markets for the sale of pure bred Irish Draught foals. Currently breeders receive only a fraction of the income from breeding pure bred animals that they could potentially achieve than if they were to cross their Irish Draught mares with more athletic breeds. This is a worrying trend one that must be reversed sooner rather than later and can only be achieve by showing breeders a market for their animals in which they will receive equal prices for their pure bred foals and not have to resort to breeding half-bred animals. New emerging markets, (such as China and other Asian countries), should be explored are possible areas of expansion for the breed into the future.

I find genetics a fascinating subject and the extreme morphologic variation among dogs makes their genetics even more interesting. As I am about to graduate soon, I will have to deal with genetics in a daily basis, from atopy to hip dysplasia. Because genetics is proceeding so rapidly, staying current is a tremendous challenge for most veterinarians. To reflect this progress, I feel that we need to update our approaches for educating our clients about wellness and prevention. I feel that is better when you catch a problem early with breed-specific screening. Being aware of breed risks is also helpful when pets present for illness. For e.g. knowing that a small breed like German Spitz is prone to patella luxation, will make my diagnosis more fast and accurate. Having a higher index of suspicion makes it less likely that I will miss a diagnosis or treat a pet inappropriately. I think I will be a better vet if I incorporate genetic susceptibility into my work in the future. I decided to focus my thesis work on my favorite dog breed the “German Spitz dog group” which is also the breed of my dog and learn more about it for my future vet carrier but also for the future good health of my dog.

The aim of the study was to perform a review study regarding the current genetic background of OC in the domestic horse. OC is a commonly seen locomotor disorder in young horses (WITTWER et al, 2007). The cause of OC is still not clear, even though it is assumed that it is of multifactorial origin, affecting many breeds and with an important genetic aspect. The whole equine genome scan was the first step in the investigation of genomic areas holding genes for OC and OCD. During the last years several studies has been done regarding the genetic background of OC in horses. In some reports it has already been proven that it's a disorder carried on many different genes (WITTWER et al, 2008). The articles analyzed for QTL mapping were mostly studies from the University of Hannover done between the years 2000-2010. The first article was the; Genome scan for Quantitative Trait Loci for OC in Hanoverian Warmblood horses using an optimized microsatellite marker set by LÖHRING (2003). LÖHRING revealed; 27 chromosome-wide QTLs on thirteen equine chromosomes for the OC trait in Hanoverian warmblood horses. In Dierks study 19 chromosome-wide significant QTLs were reveled on 17 equine chromosomes. They were found on equine chromosome; 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 16, 18, 19, 21, 22, 24 and 30. In 2009 Lampe did a complete genome scan in Hanoverian Warmblood horses and refined the QTLs for OC on chromosome 5, 16, 18 and 21. The genome-wide significant QTLs on equine chromosome 5, 16 and 21 were as earlier mentioned for fine mapping, together with the release of the horse genome assembly EquCab2 it was possible to identify new microsatellites. All QTLs on theses chromosomes were confirmed. Equine chromosome 18 was investigated as well, earlier QTLs on this chromosome was only confirmed in South German Coldblood horses in a linkage study for OC (WITTWER et al, 2007), and now a further investigation was done in Hanoverian warmblood horses. A new QTLs was identified on chromosome 18, thanks to the new microsatellites which made a more evenly and denser distribution marker set. The genetic influences of the development of fetlock OC and hock OC did not show any similarity, due the hock QTL did not map at the fetlock QTL. This was assumed likely as the genetic correlation between fetlock OC and hock OC were close to zero in trotter horses (GRØNDAHL and DOLVIK 1993) and even negative in Hanoverian warmblood horses (STOCK et al, 2005) WITTWER preformed a whole genome scan to confirm the QTLs identified in Hanoverian warmblood horses in South German Coldblood. A scan was preformed in 216 coldblood using 250 polymorphic microsatellite markers. WITTWER identified 17 putative QTLs on 17 equine chromosomes for the OC / OCD traits. The aim of WITTWER’s study was to confirm the QTLs by using single nucleotide polymorphisms (SNPs) of these genomic regions. SNPs are used as genetic markers for large scale genetic mapping projects and have been used with good result to identify chromosome regions associated with polygenic human and animal diseases. In 2008 a commercial SNPs microarray became available, the Equine SNP50 Genotyping BeadChip. It makes it possible to do, genome-wide analyses, quantitative trait loci identification and validation. It enables the development of a DNA test that can determine a horse’s genetic risk for susceptibility to a genetic disease, improving horse breeding programs since it enables the development of new diagnostic methods to upgrade equine health and welfare. The aim of KOMM’s study was to make a refine mapping of the already identified QTL on equine chromosome 2 and 4 in Hanoverian warmblood horses using dense marker sets, and also identify new potential candidate genes. Another aim of KOMM’s study was to confirm already identified QTLs and to detect new potential QTL by doing a whole genome scan with SNPs using the newly developed equine SNP50 BeadChip. 154 unrelated Hanoverian warmblood horses were used in the whole genome scan. 313 significant associated SNPs for the different phenotypic traits were observed. The QTL on equine chromosome 2 was confirmed at 17.55Mb and on equine chromosome 4 two QTL were revealed (at 7.61Mb and 39, 26 MB) these two QTL were located within the same QTL as identified before. In total ten new QTL were detected on equine chromosome 3, 5, 7, 16, 19, 20, 22, 26 and 29.

There are more than 5000 genetic diseases of humans and from 1990 to 2003, the Human Genome Project changed the world of genetics forever by mapping the human genome. The Horse Genome Project, a result of the Human Genome Project, was born in 1995 when 70 scientists from 20 countries met to make a plan for doing the same thing with the horse’s genome. During the course of the project, the genetic basis for several inherited diseases as well as simple genetic traits in horses were discovered, and molecular genetic tests could be developed. In January 2007 the work of sequencing and mapping the horse genome was completed. Researchers are now able to develop genetic tests with drastically decreased costs, time and samples needed, and a new frontier in equine genetics has been opened. The United States of America has for many years been in the lead of scientific research. The American Quarter Horse Association in particular are using vast sums of money in the research field of the breed, and for this reason much more is known about the genetic diseases in these horses. In addition, the Quarter horse is the most popular breed in the USA and the population is one of the largest in the world. The Arabian Horse Association has nonetheless established its own task force to focus on genetic diseases, and so we can only hope that this is the beginning of a new tendency for an increasing interest in genetic diseases.

Canine leukocyte adhesion deficiency in Irish Setters is an immunodeficiency disease caused by an autosomal recessive inheritable mutation in the ITGB2-gene. This C36S mutation results in impairment of the leukocyte function, and the affected homozygous puppies suffer from recurrent bacterial infections, and consequently die young. Several countries have tested their Irish Setter populations to realize the frequency of this mutation, and several countries have introduced regulations on the use of carriers in breeding. In our study, we tested Irish Setters in Hungary, to try finding the national prevalence of CLAD. We used buccal swabs to easily and non-invasively sample the dogs, and the analyzed our samples at the laboratory at the Department of Animal Breeding. Out of 11 Irish Setter samples screened for the CLAD mutation, 2 carriers were identified; the remainder exhibited a normal genotype. Hungary currently has no rules or regulations regarding the use of CLAD-carriers in breeding. Obligatory testing by breeders to identify carrier animals will decrease the frequency of the mutation, and eventually enable the eradication of CLAD from the Irish Setter population. Because of the relatively small gene pool in this breed, and to limit the economical losses breeders could suffer if strict bans were introduced, it might be advisable to adopt the strategy of not eliminating carriers with desirable traits, but rather opting to breed them only to normal (clear) animals and then either to test the progeny for the presence of the mutation or choose to spay or neuter them before placement as pets. This strategy allows elimination of the CLAD mutation in a timely fashion without too severely restricting the breeding population, losing desirable characteristics, economically affecting established breeders, or producing additional CLAD-affected offspring.