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Life expectancy in a birth cohort of Boxers followed up from weaning to 10 years of age

Marjan A. E. van HagenDepartment of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, The Netherlands.

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Bart J. DucroAnimal Breeding and Genetics Group, Department of Animal Sciences, Wageningen University, 6700 AH Wageningen, The Netherlands.

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Jan van den BroekDepartment of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, The Netherlands.

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Bart W. KnolDepartment of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, The Netherlands.

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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)

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)