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

findings of the study at hand are identical to those derived from the data of Bernardi
(1986) and Prokopenko (1998) as described in chapters 5.1.5 and 6.2.4, providing
considerable support for this hypothesis. Unfortunately, no sufficient data on which
types of cancer account for this phenomenon were available.
Castration showed a considerable lifespan benefit in female Irish Wolfhounds in this
study, which is consistent with what is generally accepted in the literature. In male
Irish Wolfhounds, however, a non-significant decrease in life expectancy, as well as a
significant increase in Osteosarcoma risk was found in castrated animals. This
mirrors findings in other studies, where castration has been associated with an
increase in osteosarcoma risk (Ru, Terracini et al. 1998; Cooley, Beranek et al.
2002). However, no such risk increase was found for castrated female Irish
Wolfhounds in the study at hand as opposed to the two quoted studies.
It is possible that the increase in OS risk in castrated males may be partially
mediated through a longer growth period in males that underwent early castration.
However, other hormone-mediated effects are likely to also play a role in this context.
Given that neither a lifespan benefit nor a decrease in any particular cause of death
associated with male castration could be demonstrated in the study at hand, it seems
advisable not to routinely subject male Irish Wolfhounds to the procedure. If the
owner insists on the operation, it should at least be postponed until after the end of
the animal's growth period.
7.1.5 Development of Lifespan Over Time
As shown in chapter 6.2.6, there was a highly significant diminution of life expectancy
in dogs born since the 1960s. Furthermore, although lifespan data from before this
period are scarce in the database used for this study, other results (Comfort 1956)
suggest that there seems to be a phase of increasing lifespan, then a point when a
maximal lifespan was reached in dogs born in the 1960s, followed by a period where
it dropped again, to the point where life expectancy of Irish Wolfhounds born 1990-
1993 was decreased by roughly 1½ years as compared to their ancestors born
during the 1960s.
The reasons for this development are difficult to ascertain. Obviously, the increasing
possibilities of canine veterinary health care that became available in the years
following 1960 are a possible candidate to explain the increase in lifespan during this
period – the introduction of effective veterinary vaccination programs in this decade in
particular has probably played a key role, as may be the case with the wider
availability of antibiotic and antiparasitic drugs. However, this does not explain why
lifespan subsequently started to drop again despite the fact that the quality of
available veterinary care continued to increase.
Natural selection – "survival of the fittest" – may have influenced the observed
development: Back when veterinary care was more limited in its possibilities, Irish
Wolfhounds were subject to selection by their natural fitness and vigour. Even in the
absence of conscious selection for health and vigour traits, it was less common for
weaker individuals to be used for breeding, since they were eliminated from the
genepool at an earlier age; most probably due to infectious diseases. This may have
contributed to a selection for vigour as well as continuous purging phenomena (see
chapter 7.2.2.3) in the breeding population, which could then realise its full genetic
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