Abstract
Data on doe longevity in a rabbit population were analysed using a semiparametric log-Normal animal frailty model. Longevity was defined as the time from the first positive pregnancy test to death or culling due to pathological problems. Does culled for other reasons had right censored records of longevity. The model included time dependent covariates associated with year by season, the interaction between physiological state and the number of young born alive, and between order of positive pregnancy test and physiological state. The model also included an additive genetic effect and a residual in log frailty. Properties of marginal posterior distributions of specific parameters were inferred from a full Bayesian analysis using Gibbs sampling. All of the fully conditional posterior distributions defining a Gibbs sampler were easy to sample from, either directly or using adaptive rejection sampling. The marginal posterior mean estimates of the additive genetic variance and of the residual variance in log frailty were 0.247 and 0.690.
Highlights
In rabbit does for meat production the average annual replacement rate is around 120% [15]
In order to achieve this objective, we extended the model proposed by Korsgaard et al [13] to include time dependent covariates
The animals belong to the V strain [8], where animals were selected for litter size, 28 days after parturition, based on a family index
Summary
In rabbit does for meat production the average annual replacement rate is around 120% [15]. One male is mated with a few does, the proportion of full-sibs in the data is high and females are closely related. In populations with this family structure the assumptions underlying sire models are far away from being satisfied, and to use animal models should be preferred. Another characteristic of rabbits is the very high reproductive rhythm, which implies that a female changes from one physiological state (e.g. lactating, pregnant, empty) to another within just a few days. The risk of culling/death is expected to differ in different physiological states, it is desirable to use an animal model with time dependent covariates for analysing longevity records of rabbits
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