Where the \(\sigma^{2}\) variances were obtained as the reciprocal of the precisions (\(\tau\)) mentioned in the model description.
All the models were fitted using rjags, an R (---R Core Team 2016---) interface to JAGS (Just Another Gibbs Sampler, \cite{Plummer2015}) which uses Gibbs Sampling to estimate the marginal posterior distributions for the parameters of interest. Approximately 35% of the strain data was left-censored, and missing values due to censoring were imputed by JAGS as a random value below the limit of detection (using the function dinterval; for details see  \cite{Lunn2012}, but above -1.5 (equivalent to a negative strain of 1500 micro-strains). We used a family model instead of an animal model as, for the purposes of a simple one-generation pedigree the models are equivalent (sensu identical expected values and variance, \cite{Henderson_1985}), while the family model is much less computationally intensive. The R/JAGS code is available as supplementary material.