Epsilon Archive for Student Projects

Abstract

The aim of the study was to investigate whether the sedation method had an effect on the screening result for hip dysplasia (HD). Another aspect considered was if the dog’s weight had an impact on the results. This study was a follow up on the results from an earlier study of sedation routines in Swedish dogs. The breeds included in this study were the same as in the earlier one; German shepherd, Bernese mountain dog, Boxer, Newfoundland, Rottweiler, Saint Bernard, Golden and Labrador Retriever. The analyses were based on data provided by the Swedish Kennel Club (SKC), and included information on all dogs in the SKC database of the concerned breeds screened for HD during 2004-2010. The information included age, weight, registration number of the dog and its parents, hip status, clinic, gender, breed and sedation method. HD is a polygenic trait which means that the phenotype is affected by both genes and environmental factors. A dysplastic hip has a poorly fitted hip socket, which often leads to arthritis and suffering in affected dogs. Environmental factors that can have an impact on whether a dog develops dysplasia or not are for example feeding, weight, age at screening and sedation method. The disease is more common in heavy, large breeds than in small ones. The reason for that can be how fast growing the breed is, and also which size and weight it has. How successful the breed club has been in trying to select healthy dogs to decrease the frequency of HD is another reason for certain breeds to be more commonly dysplastic than others. The heaviest and largest breeds in this study, Newfoundland and Saint Bernard, were found to be the ones with highest frequency of hip dysplasia. Labrador Retriever, Rottweiler and Bernese mountain dog were the healthiest ones, regarding hip status, of the breeds included in the study. In 2000, the SKC decided to join the FCI protocol for examination and grading of HD. The FCI grading scale has five classes, A to E, and is commonly used in European countries. The grades A and B means that the dog is free from dysplasia and C, D and E means mild, moderate and severe HD, respectively. For the screening result to be official, the dog must be at least 12 months old. For some giant breeds such as Newfoundland and Saint Bernard the limit is 18 months. Another requirement is that the dog is sedated during the screening procedure. Information on which sedation method that has been used on each individual dog has been recorded by the SKC since 2004. Today the sedation method used is decided by the individual veterinary clinics that the dog owner chooses to use. This means that several sedation methods are in use. In the analyzes sedation methods were divided into six different groups, medetomidine and butorphanol, medetomidine, acepromazine, dexmedetomine and butorphanol, dexmedetomine and “others”. The sedation methods that were used in less than 2 % of the participating dogs were sorted into “others”. The sedation methods works in different ways, but most of them both calm the dog, makes it easy to handle and relaxes its muscles. Acepromazine differs from the others by just calming the dog, but the muscle tonus stays intact. Analyzes showed that dogs that were given acepromazine had a lower risk of being diagnosed with HD than the dogs that had undergone a more heavy sedation. Other factors that might have an effect on the development of HD were also analyzed. The weight of the dog had a significant effect on HD, and a tendency towards a correlation between increasing weight and dysplastic hip joints could be seen. However, dogs with the most severe type of dysplasia, E, deviated from this tendency. Earlier studies suggest that a dog that is given a restricted diet and kept in good condition is more likely to stay healthy and not develop HD. Whether the sex had an impact on the development of HD has been studied earlier with various results. In this study the effect of the sex on HD differed between breeds and no clear pattern could be seen. During the time period that the data was collected the SKC had five different panelists evaluating radiographs. The analyses showed a significant effect of panelist on HD. To be able to adjust for the impact of systematic environmental effects and decrease the prevalence of HD more efficiently, the suggestion is to base the selection on BLUP breeding values rather than on phenotype.