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Longevity in the Standard Poodle

                Longevity in the Standard Poodle
                             by John B. Armstrong, Ph.D.
                                  Department of Biology
                         University of Ottawa, Ottawa, Canada



    What is a reasonable life expectancy for a Poodle? ...or, for that matter, any domestic dog? This is not information readily
    available, as neither owners nor veterinarians are obliged to report deaths, and the kennel clubs keep no records. Where such
    data exists, it has been collected by surveys, and the results depend on how representative the sample is of the population. For
    example, a Swedish study (Bonnett et al., 1997) based on insurance claims ignores all past age 10 as they are no longer
    insurable, while an American study (Patronek et al, 1997) is based on deaths at veterinary teaching hospitals and will likely not
    include many that die of old age. Nevertheless, both rank the Standard and Miniature Poodle among the most long-lived dogs.



    Data collection
    We collected data from breeders and owners responding to requests placed in breed-specific publications, Internet discussion
    groups, and on the Canine Diversity Web site. Many of the older reports were from obituaries placed in breed publications.
    Respondents were also asked to give the ages of living dogs. Though these are not truly random samples, I believe they are large
    enough to be considered representative of the population. As data collection progressed, we found that the means changed very
    little after the first 150-200 reports.

    Longevity then and now
    The determination of the median lifespan is straightforward if one has sufficient data and the period covered is sufficiently far in
    the past that no individuals are still living. For more recent dogs, one can look at the percent still living from any year and attempt
    to determine the year for which 50% are still alive. The oldest dog reported still living in 1999 was born in 1982. Analysis of %
    survival over that period suggests a median lifespan of close to 11 years (Fig. 1).






















    Fig. 1. Survival of recent Standard Poodles. The data was collected during 1999. The curve is a best-fit polynomial calculated
    with Microsoft Excel. N = 627
    For older data, the number of reported deaths at each age may be taken as a percentage of the total reported, and is probably
    most clearly visualized by plotting the data as cumulative mortality, or a survivorship (% still living at age N). The data shown in
    Fig. 2 shows the survivorship of this group, compared to the recent group.






















    Fig. 2. Comparison of survival of poodles born before 1982 (N = 361), median lifespan 12.7 yrs, with those born more recently
    (N = 627), median lifespan 11.5 yrs.
    The difference of 0.5 yrs between the two results for the recent group is probably accounted for by the latter analysis weighting
    the years according to the number of reports. The difference between the recent and the earlier poodles is a more worrisome
    1.2-1.8 years. Is this difference real, and if so, what could account for it?

    The artifact possibilities include:

    sampling error - one or both groups are not representative of the whole population.
    selective memory - dogs that died young may have been forgotten and/or older dogs may have had an extra year or two added.
    analytical error - due to the difficulty of correcting the recent group for dogs still living. (Without correction, the median lifespan
    of the recent group is 8.4 years.)
    The remaining possibilities would include:
    environment - such as a higher level of toxic substances in the environment, poorer nutrition or over-agressive vaccination.
    genetics - a higher level of genetic abnormalities resulting from loss of genetic diversity, possibly due to line/inbreeding.
    Though inbreeding has an impact on longevity (see below), the inbreeding coefficients of the two groups were not significantly
    different.



    Effects of Inbreeding - Expectations
    A second objective of this study was to evaluate the impact of inbreeding on lifespan and the incidence of genetic problems.
    Among dogs that are only very slightly inbred, I would expect to find that some die from genetic and others from non-genetic
    problems. The frequency with which the former appear will depend on how common the "bad gene" is in the population. The
    frequency will be increased by inbreeding, because inbreeding increases homozygosity. However, if the problem leads to early
    mortality, continued inbreeding should tend to eliminate it. One might therefore predict that the highly inbred dog could be
    substantially free of genetic diseases. In contrast, nongenetic problems should be largely unaffected by inbreeding.
    However, though I agree that inbreeding can be used to identify undesirable mutant genes, there are several complicating
    factors. First, a genetic problem may be dismissed as nongenetic, particularly if it is not fully penetrant. Second, a dog may be
    bred, and it's progeny bred, before a late-onset problem is evident. Unfortunately, even a well-publicized announcement by the
    owner may not discourage the use of the descendants. These factors may actually increase the incidence of the problem in a
    highly inbred line.

    As an added complication, inbred lines may accumulate sub-lethal alleles that, individually, have no particularly obvious effect
    (and are not selected against) but collectively reduce overall fitness. The relative frequencies of the different primary causes of
    death may or may not change as a result.



    Effects of Inbreeding - Results
    When we break down the results into 4 subgroups according to the level of inbreeding (based on a 10-generation pedigree that
    is at least 95% complete), the survival of those inbred to less than 6.25% (the equivalent of first cousins who shared no other
    common ancestry) is significantly greater than for the more highly inbred dogs.























    Fig. 3. Standard Poodle survivorship at different levels of inbreeding. Blue diamonds: < 6.25% (N=39); pink squares: 6.25%
    -12.5% (N=65); red triangles: 12.5-25% (N=141); black circles: > 25% N=71). The solid line is fitted to the > 25% group.
    The least inbred group survive, on average, 14 years -- approximately 4 years longer than the most highly inbred. The shape of
    the survivorship curve more closely resembles that of a non-inbred population.




    Cause of Death
    Cause of death was indicated for 355 of the dogs surveyed. The most frequent cause cited for the pre-1982 dogs was "old age"
    (42.7%), whereas cancer was the most common cause in the 1982-99 group (33.7%), with old age only being cited 9.1% of the
    time. Table 1 shows the incidence of the most common causes of death, treating "old age" deaths as unknown.

    before 1982 1982-99
    Addison's 2.8% 5.9%
    Cancer 41.5% 37.1%
    GDV (bloat) 20.8% 27.6%
    Immune-mediated 0.9% 7.6%
    Kidney failure 5.7% 8.2%
    Seizures 5.7% 1.2%
    Cardiovascular* 6.5% 3.5%
    All other 16.1% 16.5%
    * includes stroke
    Bloat kills about 30% of the affected dogs. That would mean that the risk of a Standard Poodle bloating at least once during its
    lifetime may be as high as 90%.

    There is a very strong correlation between the incidence of bloat and inbreeding (Fig. 4). However, one should not conclude that
    a dog that has a low inbreeding coefficient is at no risk. The correlation may be due to the genetic predisposition to bloat being
    carried by those lines that have, in the past, practiced the closest inbreeding. If this predisposition is inherited as a dominant
    trait, only one parent need be a carrier.





















    Fig. 4. Percentage of dogs in a particular inbreeding range that were reported as dying of bloat.
    The incidence of cancer is also likely to be higher than shown, as there are some dogs who survive cancer. Additionally some
    proportion of the dogs reported as dying of old age probably have cancer. Cancer shows a slight negative correlation with
    inbreeding, but the difference between the least and most inbred dogs is not statistically significant.
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