Model* Effect tested AIC X2 d.f. p a) Control vs. TSB t + d + s   409.3       d + s Treatment 415.9 8.6 1 0.003 t + d + t|s Treatment x sire 411.9 1.4 2 0.51 t + t|d + s Treatment x dam 404.2 9.1 2 0.01 b) TSB vs. S.ferax t + d + s   503.2       d + s Treatment 509.0 7.8 1 0.005 t + d + t|s Treatment x sire 502.2 5.0 2 0.08 t + t|d + s Treatment x dam 506.3 0.9 2 0.63 c) Control vs. S.ferax t + d + s   502.4       d + s Treatment 500.6 0.2 1 0.65 t + d + t|s Treatment x sire 505.8 0.6 2 0.74 t + t|d + s Treatment x dam 498.1 8.3 2 0.02 *t = treatment; d = dam; s = sire, t|d = dam and dam x treatment interaction; t|s = sire and sire x treatment interaction

Table 1: Likelihood ratio tests on mixed model logistic regressions on embryo mortality (based on a binomal distribution). Different models are compared to determine whether a treatment by itself or in interaction with parental effects caused changes in embryo mortality. “TSB” = addition of supplementary nutrients to induce growth of microbial pathogens, “S.ferax” = addition of TSB plus S. ferax. The Akaikes information criterion (AIC) indicates the quality of fit of a model. P-values were obtained from comparisons between a model and its reference model (t+d+s).