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  • Author or Editor: Bart W. Knol x
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Abstract

Objective—To obtain heritability estimates for diseases and characteristics in Boxers.

Animals—Birth cohort of 2,929 purebred Boxers from 414 litters.

Procedure—Heritability estimates were determined for cheiloschisis-palatoschisis, cryptorchidism, epilepsy, stifle disorders, cardiac disorders, coat color, birth weight, and adult weight, and height. Binary traits were analyzed by use of a mixed-effects probit model. Some traits also were analyzed by use of a model that postulated monogenic inheritance. Full pedigree analyses were performed. Variation in incidences of disease among clusters of related dogs was evaluated.

Results—Heritability estimates were virtually zero for cardiac disorders, medium (0.17 to 0.36) for most other traits, and high (> 0.55) for coat color, birth weight, and adult height. Litter effects and risk factors affected cheiloschisis-palatoschisis, heart murmur, coat color, broadly defined epilepsy, and adult weight. Litter effects may be attributable to common environmental effects for littermates but also may be attributable to dominance variation caused by a recessive gene. Heritability estimates increased when stricter definitions for epilepsy and stifle disorders were used. The monogenic model did not reveal higher heritability estimates for 6 traits analyzed. Incidences for white coat differed significantly for 10 familial clusters, confirming high heritability and effects of familial lineage.

Conclusions and Clinical Relevance—Results indicate that genetic improvement of most traits should be feasible, except for cardiac disorders. However, because most traits are influenced by environmental effects as well as genetic effects, genetic counseling based on polygenic inheritance and use of familial information rather than strict exclusion of parents is preferred. (Am J Vet Res 2001;62:1198–1206)

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in American Journal of Veterinary Research

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