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  • Author or Editor: Angelique L. J. Nielen x
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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)

Full access
in American Journal of Veterinary Research



To determine relative impact of genetic, common-litter, and within-litter factors on puppy mortality.


2,622 Boxer puppies of 413 litters born during a 14-month period.


For each puppy, pedigree was determined, and litter in which it was born was registered. Overall mortality and mortality per specific cause of death were analyzed by use of a model that included an additive genetic effect, common-litter effect, within-litter effect, and regression of mortality on inbreeding coefficient. Relative importance of the effects was determined from estimates of the variance in mortality explained by each factor.


22% of the puppies died before reaching 7 weeks old. Stillbirth was the most frequent cause of death, followed by infection. Most observed differences were attributable to within-litter factors, which explained 67% of the variance in death attributable to infection and ≤ 96% of the variance in death attributable to asphyxia. Common-litter factors were more important than additive genetic factors. Variance attributed to common-litter factors ranged from 2% for cheiloschisis, palatoschisis, or cheilopalatoschisis to 30% for death attributable to infection, and variance attributed to additive genetic factors ranged from 0% for asphyxia to 14% for euthanatized because of white color. Inbreeding coefficient had a significant effect on death attributable to infection, which increased 0.26% for each percentage increase of inbreeding.

Conclusions and Clinical Relevance

Additive genetic factors have less impact on preweaning mortality than common-litter factors, which in turn have less impact than within-litter factors. Mortality attributable to infection increases significantly with increases in inbreeding. (Am J Vet Res 1999;60:1106-1110)

Free access
in American Journal of Veterinary Research