By Ann MilliganArticle links:
http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0172918 http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0172918&type=printable (PDF) A. M. Oberbauer1*, G. G. Keller2, T. R. Famula1
1 Department of Animal Science, University of California, Davis, Davis, CA United States of America,
2 Orthopedic Foundation for Animals, Columbia, MO United States of America
"The objectives of the present study were to characterize the influence of non-compulsory selection on phenotypic radiographic assessment of hip and elbow conformation over time. Dog breeds that were most highly participatory in a voluntary United States radiographic screening process for hips and elbows were evaluated for improvement, whether maternal or paternal selection was more responsible for any observed progress, whether some breeds prove more amenable to selection than others, and whether selection against one orthopedic disorder yielded concomitant improvement in the other."
"Canine hip dysplasia (CHD) and elbow dysplasia (ED) impact the health and welfare of all dogs. The first formally organized assessment scheme to improve canine health centered on reducing the prevalence of these orthopedic disorders. Phenotypic screening of jointconformation remains the currently available strategy for breeders to make selection decisions. The present study evaluated the efficacy of employing phenotypic selection on breed improvement of hips and elbows using the Orthopedic Foundation for Animals complete database spanning the 1970±2015 time period. Sixty breeds having more than 1000 unique hip evaluations and 500 elbow evaluations (1,056,852 and 275,129 hip and elbow records, respectively) were interrogated to derive phenotypic improvement, sex and age at time of assessment effects, correlation between the two joints, heritability estimates, estimated breeding values (EBV), and effectiveness of maternal/paternal selection. The data demonstrated that there has been overall improvement in hip and elbow conformation with a reduction in EBV for disease liability, although the breeds differed in the magnitude of the response to selection. Heritabilities also differed substantially across the breeds as did the correlation of the joints; in the absence of a universal association of these differences with breed size, popularity, or participation in screening, it appears that the breeds themselves vary in genetic control. There was subtle, though again breed specific, impact of sex and older ages on CHD and ED. There was greater paternal impact on a reduction of CHD. In the absence of direct genetic tests for either of these two diseases, phenotypic selection has proven to be effective. Furthermore, the data underscore thatselection schemes must be breed specific and that it is likely the genetic profiles will be unique across the breeds for these two conditions. Despite the advances achieved with phenotypic selection, incorporation of EBVs into selection schemes should accelerate advances in hip and elbow improvement."
From the Discussion...
"The data presented here confirms that employing phenotypic health information and selecting sires and dams from pedigrees free from dysplasia does reduce the condition. Acceptance of using health information in breeding decisions is growing. A 2004 study of Dutch Boxer breeders  indicated that 32% of the breeders utilized genetic information, expressed as an odds ratio of particular sire-dam combinations producing deleterious health traits, in their mate selections. A recent report assessing selection practices among Australian dog breeders indicated that the ªgenetics and healthº attribute of potential dams was one of the top four decision components ; despite this weighting in dam selection some breeders failed to practice health screening, including for CHD. As selection tools for health characteristics improve, using those will demonstrably improve the health of dogs."
By Ann MilliganA representative study of Danish owners of four small dog breeds
P. Sandøe, S. V. Kondrup1, P. C. Bennett, B. Forkman, I Meyer, H. F. Proschowsky,J. A. Serpell, T. B. Lund
PLOS ONE | DOI:10.1371/journal.pone.0172091 February 24, 2017
Breeds in this study include: Cavalier King Charles Spaniel, French Bulldog, Chihuahua and Cairn Terrier.
"A number of dog breeds suffer from welfare problems due to extreme phenotypes and high levels of inherited diseases but the popularity of such breeds is not declining. Using a survey of owners of two popular breeds with extreme physical features (French Bulldog and Chihuahua), one with a high load of inherited diseases not directly related to conformation (Cavalier King Charles Spaniel), and one representing the same size range but without extreme conformation and with the same level of disease as the overall dog population (Cairn Terrier), we investigated this seeming paradox. We examined planning and motivational factors behind acquisition of the dogs, and whether levels of experienced health and behavior problems were associated with the quality of the owner-dog relationship and the intention to reprocure a dog of the same breed. Owners of each of the four breeds (750/breed) were randomly drawn from a nationwide Danish dog registry and invited to participate. Of these, 911 responded, giving a final sample of 846. There were clear differences between owners of the four breeds with respect to degree of planning prior to purchase, with owners of Chihuahuas exhibiting less. Motivations behind choice of dog were also different. Health and other breed attributes were more important to owners of Cairn Terriers, whereas the dog's personality was reported to be more important for owners of French Bulldogs and Cavalier King Charles Spaniels but less important for Chihuahua owners. Higher levels of health and behavior problems were positively associated with a closer owner-dog relationship for owners of Cavalier King Charles Spaniels and Chihuahuas but, for owners of French Bulldogs, high levels of problems were negatively associated with an intention to procure the same breed again. In light of these findings, it appears less paradoxical that people continue to buy dogs with welfare problems."
The "study aimed to answer the following questions:
1) Do motivations for acquiring a dog, and pre-purchase owner characteristics, differ between owners of the four breeds?
2) Do levels of expenditure on veterinary treatments and health and behavior problems experienced differ for owners of the four dog breeds?
3) Do motivations prior to acquisition, and owners' experiences of health and behavior problems with their dogs, explain differences in the quality of the owner-dog relationship between the four breeds?
4) Do intentions of acquiring the same breed the next time a dog is to be procured change as a function of experienced health and behavior problems?"
By Ann MilliganWhole genome sequence, SNP chips and pedigree structure: Building demographic profiles in domestic dog breeds to optimize genetic trait mapping
Authors: Dayna L. Dreger, Maud Rimbault1, Brian W. Davis1, Adrienne Bhatnagar1, Heidi G. Parker, Elaine A. Ostrander
Key Words: population, homozygosity, canine, inbreeding
"Successful application of whole genome sequencing and genome-wide association studies for identifying both loci and mutations in canines is influenced by breed structure and demography, motivating us to generate breed-specific strategies for canine genetic studies."
"In the decade following publication of the draft genome sequence of the domestic dog, extraordinary advances with application to several fields have been credited to the canine genetic system. Taking advantage of closed breeding populations and the subsequent selection for aesthetic and behavioral characteristics, researchers have leveraged the dog as an effective natural model for the study of complex traits, such as disease susceptibility, behavior, and morphology, generating unique contributions to human health and biology. When designing genetic studies using purebred dogs, it is essential to consider the unique demography of each population, including estimation of effective population size and timing of population bottlenecks. The analytical design approach for genome-wide association studies (GWAS) and analysis of whole genome sequence (WGS) experiments are inextricable from demographic data.
We have performed a comprehensive study of genomic homozygosity, using high-depth WGS data for 90 individuals, and Illumina HD SNP data from 800 individuals representing 80 breeds. These data were coupled with extensive pedigree data analyses for 11 breeds that, together, allowed us to compute breed structure, demography, and molecular measures of genome diversity. Our comparative analyses characterize the extent, formation, and implication of breed-specific diversity as it relates to population structure. These data demonstrate the relationship between breed-specific genome dynamics and population architecture, and provide important considerations influencing the technological and cohort design of association and other genomic studies."
"The work presented here examines variables of inbreeding and homozygosity in a large and comprehensive set of dog breeds through parallel use of pedigree data, genome-wide SNP genotyping, and WGS. Specifically we compare data from extended pedigree analysis, genotyping with a SNP chip of 173,622 potential data points, and WGS with an average depth of 27.79X.
We found that each dog breed has a unique profile of genome diversity, varying by amount of total homozygosity as well as number and size of homozygous regions. Likewise, while we observe variation between members of the same breed, multiple individuals from a single breed can be combined to obtain an accurate reflection of breed-specific homozygosity and knowledge regarding fluidity of variation within breed confines. This allows us to define metrics that inform the design of canine genetic studies while also allowing us to develop an understanding of the intricate complexity of the diversity of dog breeds. Individual diversity metrics are provided for over 100 breeds as a resource for investigators in the field."
Using data from the Finnish Kennel Club (FKC) and from a screening program of the Finnish Dachshund Club, researchers from the University of Helsinki and the FKC provide evidence to support the use of radiographic screening for intervertebral disc calcification in Dachshunds and for adopting Estimated Breeding Values as a tool for selecting dogs for breeding.
"The present study surveyed the owners of more than 30 breeds of dogs using the Canine Behavioral Assessment and Research Questionnaire (CBARQ), a validated and reliable instrument for assessing dogs’ typical and recent responses to a variety of common stimuli and situations. Two independent data samples (a random sample of breed club members and an online sample) yielded significant differences among breeds in aggression directed toward strangers,owners and dogs (Kruskal–Wallis tests, P < 0.0001)."
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