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

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7.2 Population Genetics 7.2.1 Population History and Genetic Bottleneck Phenomena While the existence of large sighthound-like wolf-hunting dogs from Ireland is reported time and again throughout history (Symmachus 393; Graham 1885; Walker 1896; Hogan 1897; Gardner 1931; DeQuoy 1971; DeQuoy 1973; Miller 1988; Maison 1990; DeQuoy 1991; DeQuoy, Castillo et al. 1993; McBryde 1998; Thomasson 1999; Doyle 2002), the history of modern Irish Wolfhounds as studied in this thesis starts in the 1860s, when Captain George A. Graham defined the modern breed standard and started a controlled breeding program with the goal of recreating the breed that was, by then, almost extinct. To achieve this goal, he bred dogs that were believed to be related to the original Irish Wolfhound to other breeds of great size, such as Scottish Deerhounds, Great Danes and a variety of other dogs. Consult the above references for more detailed descriptions of the exact modus operandi. Based on the present data, the population history of modern Irish Wolfhounds can be roughly divided into the following phases: Time Period Phase N° ca. 1860-1890 Start of modern Irish Wolfhound breeding by Capt. Graham 1 and associates. First genetic bottleneck. ca. 1890-1914 Consolidation period; occasional further outcrossing. 2 Increase of population size. 1914- ca. 1920 World War I: decrease of population size; inbreeding peak. 3 Second genetic bottleneck. ca. 1920-1939 Economic prosperity; population size increases even 4 throughout the Great Depression World War II: population size greatly reduced, strong 1939-1952 inbreeding on dog 4732 in the UK and IRL. Third genetic bottleneck. 1952 Import of dog 5838 from the USA to the UK; short decrease 5 of inbreeding due to widespread use of this individual. since 1952 Dog 5838 becomes widespread throughout all Irish Wolfhound pedigrees. Fourth genetic bottleneck. since 1965 Exponential increase of population size masks previous 6 inbreeding in Wright's Inbreeding Coefficients. Table 7.1: Phases of the history of the modern Irish Wolfhound population. The N° column refers to Fig. 7.1 below. As shown in chapter 6.3.2, the last two genetic bottlenecks have the most influence on the population born 1965-2005. Of course, it should be kept in mind that the dogs shown to be the most important ancestors of this population are still subject to the genetic consequences of the previous two bottlenecks Figure 7.1 gives a typical example of the complete pedigree of an Irish Wolfhound born in 2000. Every ancestor is listed only once and connected to all individuals in its 96
first-generation progeny. The broadness of the genogram thus gives an impression of the effective breeding population size at a given time. 5 4 3 2 1 6 Masked Inbreeding Exponential Growth WW 2 1939-45 Interwar years WW 1 1914-18 Consolidation ca. 1890-1914 1860: Initiation of Modern Breeding Fig. 7.1: Typical genogram of an Irish Wolfhound born in 2000 (field in the far left), illustrating the occurrence of several genetic bottlenecks during the history of the population. The numbers in the figure refer to the occurrences described in table 7.1 above. Compare this graph to fig. 6.3 and 6.4 Note that the third and fourth genetic bottleneck do not appear as separate occurrences in this graph due to their closeness in time. The studied individual is subject to an average level of inbreeding (COI(5)=0.0078; COI(10)=0.1120; COI(20)=0.2707; Meuwissen's Inbreeding Coefficient = 0.3470). 7.2.2 Inbreeding and Lifespan 7.2.2.1 Mechanisms of Inbreeding Depression Inbreeding depression cannot occur if gene effects are purely additive – some degree of dominance and/or epistatic interaction between genes is necessary. Currently, there are two main theories on the genetic mechanisms underlying inbreeding depression: The partial dominance model and the overdominance model (Charlesworth and Charlesworth 1987). The partial dominance model of inbreeding depression postulates that inbreeding depression is caused by the accumulation of recessive deleterious alleles that can occur as the degree of homozygosis increases. This accumulation of recessive deleterious alleles ("genetic load") that are normally masked by dominance effects in the heterozygous form results in a loss of fitness in the inbred population, which can be expected to be proportional to the degree of deleteriousness in the relevant alleles. 97
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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
Page 51 and 52: CU/dl). Of these with low values, 2
Page 53 and 54: 3.12 Miscellaneous 3.12.1 Odds Rati
Page 55 and 56: The disease is clinically character
Page 57 and 58: It is interesting to notice that ev
Page 59 and 60: 4.2.2 The SAS Program Package Stati
Page 61 and 62: 5 Results of Past Studies Revisited
Page 63 and 64: 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: degree. The fact that average lifes
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 and 116: (Papazoglou, Monnet et al. 2002). G
Page 117 and 118: While there are currently no heredi
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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Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

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