I would like to know is there any compiled findings about this matter around. My findings are so far confusing, clearly indicating that some factors are missing.
OBSERVATION.
Slaughtered a horse foal. Welfedness was at maximum, action performed by a character with both survival and farming vastly superior to animal's stats, with a good metal axe in hand, again, with qualities at least two times better than slaughtered animal quality.
The stats of the horse foal: q35-46-40, meat quantity 11, milk quantity 12, meat quality 91%, milk quality 108%, hide quality 98%, breeding 63; end-sta-met 111%-15-16.
Slaughtering has produced a corpse with the same ess-sub-vit as the alive animal had, q35-46-40.
The result of skinning was q32.7-41.4-30.1 raw horse hide, the foal had hide quality 98%.
32.7 is roughly 93.4% of 35
41.4 is exactly 90% of 46.
30.1 is exactly 75.25.% of 40.
Clearly there are additional factors that influence every stat of the final product.
Butchering produced entrails, intestines etc with qualities 31.5-39.8-28.7, the foal had meat quality 91%.
31.5 is exactly 90% of 35.
39.8 is roughly 86.5% of 46.
28.7 is exactly 71.75% of 40.
So, what's the matter?
In case the topic is still unclear (hardly believable), I'm going to post more results and invite dear gentlemen to participate in the study.
Edit: operation performed by a character with 100+ in every base attribute, and sufficient cooking (100+), farming (100+) and survival (74); increasing by 1 every neglected ability stat did not changed qualities of the products.