Model selection
We used R (v3.5.3; R Core Team, 2019, Vienna Austria) for all analyses.
We constructed either linear mixed effects models using the lme4 package or linear models using stats package to test our four
main hypotheses. Final best-fit models were selected using an AIC
selection criterion, ΔAIC ≥ 3. The only exception was when ΔAIC was
within 3 for the models for liver and pectoralis lipid damage including
cohort as a random factor compared with excluding it, and in these
cases, we decided to control for cohort.