**Genetic parameters for longevity in a colony of German Shepherd dog guides**

**J.B. Cole**^{1}, D.E. Franke^{1}, and E.A. Leighton^{2}

^{1}Department of Animal Science, Louisiana State University, Baton Rouge, LA 70803

^{2}The Seeing Eye, Inc., Morristown, NJ

## ABSTRACT

Data on longevity for 1,304 German Shepherd dogs (GS) was used to estimate genetic parameters for working life. A Cox proportional
hazards model on unadjusted working life was used to test the assumption that the baseline hazard function for the population
is a Weibull hazard. The rejection of that assumption led to the definition of two measures of working life: estimated for
working life to 18 months post-graduation (EWL) and working life beyond 18 months post-graduation (LWL). For EWL, 92.45% of the
records were censored after 540 days, while for LWL 47.89% of the records were censored after 4,361 days. The Survival Kit
v3.12 was used for variance components and breeding value estimation. Estimates of additive sire genetic value for Cox and
unstratified Weibull models were 0.87 and 0.36 for EWL and 0.05 and 0.03 for LWL, respectively. Heritability estimates on a log
scale (assuming no censoring) were 0.19 and 0.61 for EWL and 0.09 and 0.04 for LWL, respectively. For both traits, the standard
deviations and skewness of the posterior densities of the sire variance were fairly large. Due to the small size of the dataset
and the large number of censored records, it was not possible to obtain more precise estimates of the sire variance. The large
heritabilities observed for EWL under the Cox and Weibull models should be interpreted with caution because virtually all EWL
records were censored. Pearsonâ€™s product-moment correlation coefficents for sire breeding values estimated under the Cox and
Weibull models were 0.99 for EWL and 0.88 for LWL, respectively. The low correlation between the models for LWL may be due to
large prediction error variances and the skewness of the posterion distribution of sire effects, although these problems were
noted for EWL as well.

(**Key words:** variance components, working life, dog guides)