The statistics of long-lived dogs are fine as curious cases but we can not extend its significance to broad families, except in very rare cases when the proportion of long-lived dogs is statistically significant and extensive to a high percentage of entire lineage as for Jotunheim’s dogs . On the contrary within a lineage of long lived dogs there are short lived dogs but relative smaller proportions because life span within a goup or lineage trends to show a normal distribution of frequencies.
We must not forget that long lived dogs from non healthy lineages can produce high proportions of non healthy dogs because are carriers of deleterious genes. Even proportions of affected dogs by genetic diseases, as DCM, on the offspring can be higher for a long lived sire than for short lived sire. Transmission of genetic diseases depends of genes provided by both sire and dam sides, but for popular sires with a higher number of offspring can be considered independent of dam input because diverse dam are implicated in the statistical of offspring. Curiously the comparison of incidence of DCM in the offspring of two contemporary popular sires: Eick v.d.. Rappenau (1987-1994, dead by DCM) (incidence of DCM in the offspring=7.5%) and Prinz v. Norden Stamm (1988-2001- a long lived dog) (incidence of DCM in the offspring=10.4%) which illustrates that life span is only one variable in the complex equation of survival.
Analyzing the European Dobermann population structure on a sample of 129 litters born 2009, overall sample are related by ascendancy with only three major ancestors in three significant clusters (figure 1). Main group (79.5% litters) include conformation dogs and/or ZTP grouped in two clusters related with two popular sires: Cluster 1 include dogs of majority related with Graaf Quirinus v. Neerlands Stam (GQvNS), and less with Prinz v. Norden Stamm (PvNS), Cluster 2 include dogs of related in the same extension with Graaf Quirinus v. Neerlands Stam, and Prinz v. Norden Stamm. Cluster 3 minority group (20.5% litters) includes pure working dogs related with Bingo v. Ellendonk (BvE) and much lesser with Graaf Quirinus v. Neerlands Stam, and Prinz v. Norden Stamm. Population structure of population born 2009 illustrates the “fetish power” of pedigree for breeders, and clusters size show that conformation is the goal of majority of breeders.
COI on seven generation pedigree of sample of litters born 2009 shows a positive biased distribution of frequencies (Skewness= +0.926) (not normal) which illustrates that endogamy is a dominant practice in matings (figure 2) (Average COI in sample=9.31%) . Good conformation is the first breeding goal for breeders and line-breeding and close-breeding based on pedigree data is a cultural practice of mating system common in professional and regular breeders who register several litters per year (
Leroy et al. 2007).
No significant difference in a Student t-test is observed in average COI between groups (Sig. two tailed = 0.257) (table 1). However dogs related with Bingo v. Ellendonk (Cluster 3) shows higher fitness (average litter size-ALS*) than dogs of two others clusters and significant differences in a Student t-test have been observed (Sig. two tailed = 0.001) which illustrates that selection for utility is an advantage in terms of genetic fitness over the selection for anatomical traits.
Application of general rules of reduction of COI for increasing diversity implicates that dogs of Cluster 3 (minority) must be mating with dogs of Cluster 1 or 2 and low available diversity can be loss to conform a homogeneous group. Likewise, this genetic advantage of dogs related with Bingo v. Ellendonk, despite the high average COI of this group (10.55%), may be lost when dogs of Cluster 3 are mating with dogs of Cluster 1 or 2.
* Litter size is referred to realised litter size (registered puppies)
The conclusions of the analysis of population structure and fitness for the population born 2009, suggests the possibility that average life span (LSP) may differentially affect dogs of both functional groups (working dogs related with Bingo v. Ellendong and show-dogs related with Graaf Quirinus v. Neerlands Stam, and/or Prinz v. Norden Stamm. The inability to perform the analysis of average life span on the same sample of dogs born in 2009, determines that I did a statistical analysis on a separate sample including 281 records of dogs born between 1990 and 2008 belonging to both groups (231 show dogs/50 working dogs). Each record includes: name of the dog, dates of birth and death, life span (LSP), bloodline group pedigree (Working dogs or Show dogs), and inbreeding coefficient COI.
Difference in a Student t-test for average COI between groups of this last sample (Sig. two tailed = 0.044) is in the limit of significance at 0.05 level, but is higher for Bingo v. Ellendonk related dogs (Average COI=12.54%) than for Graaf Quirinus v. Neerlands Stam, and/or Prinz v. Norden Stamm group (Average COI=10.41%).
Comparison of Kaplan-Meier survival curves (figure 3) for dogs related with both groups show that difference between groups is significant (Mantel-Cox log rank Chi-square=12.685; Sig.=0.000), and from an early age the survival factor is lower for show-dogs group in all age classes. Average life expectancy is +1.437 years higher for BvE related dogs (Average LSP=8.08 years) than for GQvNS and/or PvNS group (Average LSP=6.64 years). For long lived dogs belonging to age classes with LSP>10 years, difference is also evident between groups: Cum. Survival =16.5% for BvE related dogs, and Cum. Survival =6.3% for GQvNS and/or PvNS group.
Analysis of variance from bivariate correlations for litter size where dog is born, COI of litter and life span variables within each group not shows significant correlations in both cases.
A paradigm in conservation science predicts that isolated populations will experience reductions in individual genetic fitness due to inbreeding depression. However it’s also true that inbreeding and purging affects positively fitness and life expectancy in this cluster of dogs related with Bingo v. Ellendong specifically. Recessive deleterious mutations, with positive effects on traits linked to ﬁtness, are purged more easily by selection in small or inbred populations than in populations with random mating (
Charlesworth and Charlesworth, 1999).
It’s clear that both genetic advantages on fitness and life expectancy of dogs related with Bingo v. Ellendong are linked to accomplish both simultaneous conditions: dogs strong related by kinship with Bingo v. Ellendong and selected for working.
References:
Leroy G. , Verrier E. , Wisner-Bourgeois C , Rognon X (2007). Breeding goals and breeding practices of French dog breeders: results from a large survey. Revue Méd. Vét., 158(10), 496-503.
Charlesworth B., Charlesworth D..(1999). The genetic basis of inbreeding depression.
Genet. Res. 74:329-340.