Objective—To determine incidence, risk factors, and
heritability estimates of hind limb lameness caused
by hip dysplasia in a birth cohort of Boxers.
Animals—1,733 Boxers from 325 litters.
Procedure—Status of Boxers with respect to clinical
signs of canine hip dysplasia (cCHD) was registered
during an 8-year period. Survival analysis accounted
for dogs lost to follow-up. Effective heritability for
developing cCHD was estimated by use of a proportional
hazard model on the basis of the Weibull distribution.
Parametric survival models were developed to
identify the influence of potential risk factors.
Results—Cumulative hazard rate for cCHD from 7
weeks to 8 years of age was 8.5%. Dogs that were
kept on a floor covered with a slippery material were
1.6 times as likely to develop cCHD, compared with
dogs kept on a nonslippery floor. Risk of cCHD doubled
in dogs from litters with a high preweaning mortality
rate. Dogs that were neutered at 6 months prior
to a diagnosis of CHD were 1.5 times as likely to
develop cCHD, compared with sexually intact dogs.
Dogs > 5 years of age were 1.8 times as likely to
develop cCHD, compared with younger dogs.
Estimated effective heritability of cCHD was 0.11. In
terms of the risk of cCHD in progeny, mean estimated
breeding value (EBV) of the 10 best and 10 worst
sires was –0.32 and 0.42, respectively.
Conclusions and Clinical Relevance—Registration
of Boxers that develop cCHD may provide a strategy
for disease prevention. In addition to diagnostic evaluation
of radiographs, sire EBVs provide useful information
for breeding selection decisions. (Am J Vet
Objective—To determine mortality rate over time,
risk factors for death, and heritability of life expectancy
Animals—1,733 purebred Boxers born in The
Netherlands between January 1994 and March 1995.
Procedure—Dogs were followed up from weaning
(ie, 49 days of age) to 10 years of age through use of
a written questionnaire sent to owners every 6
months. Mortality rate over time, risk factors potentially
associated with death, and heritability of life
expectancy were examined by use of a proportional
hazards model based on the Weibull distribution.
Results—Estimated mortality rate during the 10-year
study period for this birth cohort of Boxers was 45%.
The probability of surviving to 5 years of age was
88%; the probability of surviving to 10 years of age
was 55%. Estimated effective heritability of life
expectancy was 0.076, meaning that in this population,
an estimated 7.6% of the observed variation in
life expectancy could be attributed to genetic differences
among dogs that were passed from parents to
Conclusions and Clinical Relevance—Results suggest
that cumulative incidence of death from weaning to 10
years of age among this birth cohort of Boxers was
45%. The estimated heritability of life expectancy suggested
that life expectancy can be improved by use of
selective breeding. (Am J Vet Res 2005;66:1646–1650)
Objective—To evaluate propagation velocity of acoustic waves through the lens and vitreous body of pigs, dogs, and rabbits and determine whether there were associations between acoustic wave speed and age, temperature, and time after enucleation.
Sample Population—9 pig, 40 dog, and 20 rabbit lenses and 16 pig, 17 dog, and 23 rabbit vitreous bodies.
Procedure—Acoustic wave velocities through the ocular structures were measured by use of the substitution technique.
Results—Mean sound wave velocities in lenses of pigs, dogs, and rabbits were 1,681, 1,707, and 1,731 m/s, respectively, at 36°C. Mean sound wave velocities in the vitreous body of pigs, dogs, and rabbits were 1,535, 1,535, and 1,534 m/s, respectively, at 38°C. The sound wave speed through the vitreous humor, but not the lens, increased linearly with temperature. An association between wave speed and age was observed in the rabbit tissues. Time after enucleation did not affect the velocity of sound in the lens or vitreous body. The sound wave speed conversion factors for lenses, calculated with respect to human ocular tissue at 36°C, were 1.024, 1.040, and 1.055 for pig, dog, and rabbit lenses, respectively.
Conclusions and Clinical Relevance—Conversion factors for the speed of sound through lens tissues are needed to avoid underestimation of the thickness of the lens and axial length of the eye in dogs during comparative A-mode ultrasound examinations. These findings are important for accurate calculation of intraocular lens power required to achieve emmetropia in veterinary patients after surgical lens extraction.