Arkher's blog of weebery and writing

Medieval peasants also didn’t eat chicken very often. That’s a source of eggs. If you’re lucky enough to own a cow it’s also unlikely you’d eat it unless it’s on its way out anyways. That’s a good source of milk. It’s more advantageous to keep a cow or chicken alive than to eat them.

Fat from a fat tailed sheep makes for good cooking fat if your setting is more middle eastern or North African inspired. European settings would prefer butter, lard, or olive oil depending on where exactly they are.

The limiting factor for livestock keeping in the medieval period was winter fodder--there was enough summer grazing for the spring births in fallow fields that they fertilized with their manure , but not enough hay and grazing to get them through the winter. So the lambs--all the males and some of the females--would be butchered in the fall. A bull calf might be butchered as veal (or "baby beef", depending on timing) its first fall or might be over-wintered and butchered as beef the following fall. A few of the older ewes would be butchered as mutton, replaced with female lambs from the spring births. A female calf would be traded, sold, or kept as a replacement.

Similarly, half of the chicks born would be male, destined for spring/early summer butchering. (Or caponed, castrated, though that's much more difficult with a bird.) Chicken is a lean meat, though, and rather tough in a free-range bird, so it was usually stewed rather than roasted. Capon was a bit of a luxury food due to the difficulty of castrating them. Geese were much more popular due to the fattier meat.