Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

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7.4 Future Prospects in Breeding 7.4.1 General Considerations The findings presented in this study show that Irish Wolfhounds are subject to a decrease in average lifespan as well as a number of hereditary diseases and diseases with a hereditary component, and that lifespan in the breed has decreased markedly since the 1960s. While this is likely due to a number of concurrent factors, the decrease in selection pressure towards health traits is common to the majority of them (see chapter 7.1.4). Thus, it suggests itself to return towards more severe selection strategies for physical vigour in order to allow the population to get back to the level of genetical and, consequently, physical fitness that it possessed in the early 1960s through continuous purging of deleterious alleles. If a mean Irish Wolfhound lifespan of 8.92 ± 2.23 years was possible to reach in the past, it should also be possible to reach in the future. A common argument against rigorous selection for vigour traits – rigorous selection in general – in Irish Wolfhounds is the allegation that the gene pool of the breed is too small for it to survive such measures. However, the results of the study at hand make it quite clear that, given the apparent lack of inbreeding influence on lifespan as well as the exponential increase in population size over time, the potential for severe health- and vigour-based selection was never as good in the breed as it is at present. Practically, and apart from measures against specific hereditary diseases, this would imply the exclusion of dogs from breeding that get affected by medical conditions that would likely have killed them in earlier times, such as e.g. severe infections. This does not imply that one should leave such dogs without proper medical treatment, but rather that such facts from potential breeding animals' medical history should remain in the selection criteria after they have recovered. The tendency of kennels to have fewer bitches and a smaller overall number of litters is another example of breeders' and population interests being opposed in this aspect of selection (see chapter 7.3.1.2). The present population is subject to at least two potential bottleneck events that have taken place since the times of dog 5838 due to the excessive use of two particular stud dogs – one used at least 41 times between 1972 and 1977, the other used at least 39 times between 1993 and 2000 and one of its full brothers used at least 23 times between 1995 and 2002. These would represent the first two bottlenecks in the population history during which the breed has no longer been under considerable natural purging pressure. 7.4.2 Hereditary Diseases Selection decisions against hereditary diseases should be based on their frequency in the population, the severity of suffering they cause in the affected dogs, the ease of diagnosis, and the mode of inheritance. In this context, it seems reasonable to concentrate selection efforts on conditions that are widespread throughout the population, cause severe suffering and/or death, can be diagnosed easily (making screening possible) and have a high heritability, since selection against such conditions can be expected to potentially yield the highest benefit. 110
While there are currently no hereditary diseases in Irish Wolfhounds that can be diagnosed using a genetic marker test, two conditions in particular do fulfil the requirements specified above: DCM and PSS. DCM has a high level of prevalence, undoubtedly causes suffering and death in the dog (and considerable veterinary costs for the owner), can be easily diagnosed through the published ultrasonography reference values, and has a published mode of inheritance. The disadvantage is that it cannot be diagnosed from birth, but rather manifests in dogs that are past the age at which the first breeding usually takes place, which implies that ultrasound screening needs to be repeated throughout the breeding career of the animal and also thereafter, since symptoms of hereditary DCM can still appear at a relatively late age. The approach of using frozen sperm of dead sires known to have been DCM-free throughout their lives could be a potential means of omitting this problem (see chapter 7.4.3). PSS has a high allele frequency in the population, causes an important degree of suffering and, potentially, death in affected animals (and also considerable costs for treatment), can be diagnosed at an early age through routine screening, and has a published mode of inheritance that makes indirect identification of carriers possible through the screening of their direct progeny. Where other diseases follow a defined mode of inheritance (PCD, vWD, PRA, Epilepsy), control measures based on the points mentioned in chapter three suggest themselves. As for the major diseases with hereditary components (OS, GDV and, depending on the actual prevalence, OC), the establishing of multi-parametric selection based on BLUP-estimated breeding values derived from a central health registry would be the means of choice (also see chapter 7.4.4). However, it is also important to stress that the prevalence levels of hereditary diseases may vary between different populations, which may lead to differences in the most appropriate selection strategy for a given population (also see chapter 6.2.7). Given the amount of genetic afflictions in the breed, it is impossible to recommend a general strategy that will be applicable to all populations. Nevertheless, the information concerning modes of inheritance and control measures mentioned in chapter 3 will hopefully give a solid base on which to develop breeding programs that are adapted to different populations' specific needs. Working to make solid health data on which to base such strategies available is of paramount importance in this context (also see chapter 7.4.4 below). 7.4.3 Lifespan It has been shown that there are genetic contributions to canine lifespan per se (Canterberry, Greer et al. 2005), but their influence independent from hereditary disease predispositions remains unclear. The differences found between direct progeny of popular sires in this study (see chapter 6.2.5) are an indication towards such an effect, but insufficient as proof. Heredity of working lifespan has been investigated in German Shepherds and Labrador Retrievers used as guide dogs (Cole 2003), but the heritability values found were low (h 2 = 0.016 to 0.032). Since working lifespan and effective lifespan are not necessarily identical, the significance of these findings to Irish Wolfhounds remains unclear. 111
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Aus der Abteilung Tierhaltung und T
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Omnia mors poscit - lex est, non po
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Table of Contents Acknowledgements
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1 Abstract/Summary This study inves
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1.2.3 Own Data A worldwide pedigree
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Due to the frequent bottlenecks dur
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2 Introduction "It is impossible to
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3 Literature Review Several disease
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previous results (Comfort 1960). No
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the average ages were significantly
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3.2 Intrahepatic Portosystemic Shun
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Conservative therapy is also indica
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mitochondrial hyperplasia, disrupti
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there are marked individual differe
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3.3.2 Epizootology Numbers publishe
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2002). On the molecular level, the
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3.4.2 Epizootology In past studies
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3.5.1.3 Diagnosis The history and c
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3.5.2 Epizootology A prospective st
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Differential diagnoses include recu
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3.7.1.3 Diagnosis The definite diag
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Furthermore, the Utrecht cases also
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Figure 3.1: Survival times after fi
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have an independent mode of inherit
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3.9.1.5 Prognosis Prognosis for OCD
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CU/dl). Of these with low values, 2
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3.12 Miscellaneous 3.12.1 Odds Rati
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The disease is clinically character
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It is interesting to notice that ev
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4.2.2 The SAS Program Package Stati
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5 Results of Past Studies Revisited
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5.1.4 Causes of Death 5.1.4.1 Influ
Page 65 and 66: 5.2 Analysis of Murphy (1991) ANOVA
Page 67 and 68: 5.2.1.3 Gender Effects As mentioned
Page 69 and 70: 5.2.2.3 Gender Effects No significa
Page 71 and 72: 6.1.2 Inbreeding Four inbreeding co
Page 73 and 74: 6.1.3 Geographical Origin Countries
Page 75 and 76: 6.2.1 Data of Living Dogs Ages at w
Page 77 and 78: Coefficient R 2 p F Coefficient R 2
Page 79 and 80: Fig. 6.8: Lifespan (GD) of direct p
Page 81 and 82: UC Excluded - Birth Cohorts Merged
Page 83 and 84: Fig. 6.10: 10-Generation Wright's I
Page 85 and 86: The individual and cumulative contr
Page 87 and 88: 6.4 Ancestor Analyses of Diseases P
Page 89 and 90: 6.4.2 Osteogenic Sarcoma 6.4.2.1 Re
Page 91 and 92: 6.4.4 Portosystemic Shunt 6.4.4.1 R
Page 93 and 94: 6.4.5.2 Dog 6844 Given that dog 684
Page 95 and 96: 6.4.5.4 Dog 6636 Dog 6636 (born 195
Page 97 and 98: 7 Discussion 7.1 Lifespan 7.1.1 Lif
Page 99 and 100: findings of the study at hand are i
Page 101 and 102: degree. The fact that average lifes
Page 103 and 104: first-generation progeny. The broad
Page 105 and 106: In this model, the degree of purgin
Page 107 and 108: 7.2.2.5 Present Study No significan
Page 109 and 110: It is interesting to consider what
Page 111 and 112: 7.3 Ethical Considerations 7.3.1 In
Page 113 and 114: 7.3.2 Decreased Lifespan The ethica
Page 115: (Papazoglou, Monnet et al. 2002). G
Page 119 and 120: 7.5 Future Research Prospects 7.5.1
Page 121 and 122: 8 References Ackerman, L. (1999). T
Page 123 and 124: Deeb, B. and N. Wolf (1994). "Study
Page 125 and 126: Kealy, R. D., D. F. Lawler, et al.
Page 127 and 128: Rothuizen, J. (2002). Molecular Gen
Page 129 and 130: Walker, H. (1896). Der Irish Wolfho
Page 131: ID DR DA DR10 DA10 GR GA GR10 GA10
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