I'm a bit confused with their aging, so I can not tell you how this works. I play rotationally and I noticed that some big animals seem to be nearly dead after playing them for only 1 simday - I wonder if they aged while I played other lots. On one farm I had a project running for 4 sim weeks but played also other houses in between, but those cows are mostly not very old yet. Maybe they age faster when not played...? I had aging off for all my sims during these sessions, but I did not toggle anything re animals in particular. I expected their aging to be off if my sims' aging is off, but I obviously was wrong about that. Hoping for some upclearing from Maxis as they start fixing bugs.