Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Jan van den Broek x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

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 Res 2005;66:307–312)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine mortality rate over time, risk factors for death, and heritability of life expectancy in Boxers.

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 their offspring.

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)

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research