Based on the Reactions page, I'm gathering that there's no way to make a custom reaction that uses a live animal (e.g. a custom shearing or milking reaction) ?
Closest you could get would be to use vermin, since they can be treated as items, but I haven't tried anything like that before. I wouldn't quite know how to go about it, or which hurdles may come up.
Alright, ty~
Since this thread was necro'd recently it seems fitting to put needed input into this question.
You can set up 'shearing' and milking reactions by modifying the creature raw properties. Other notable mod makers and modders in general have worked with this to have created bats (as a subterreanean animal) that have a regrowing shearable skin layer (with high tissue regeneration i think, i could be wrong and they have modified the bats skin to grow in excess like hair) to give off body parts for leather materials.
Wool by definition is a product of [YARN] (its very token specific on what can be allocated, so in some cases you might have to transform one product into another) which is why trolls can be sheared, because they have the same 'rules' as sheep in the reaction that they are based in which looks for a animal with the [YARN] body part tag if it is friendly livestock and removes it. Ill get back to you with the specifics but this is the kind of body part RAW configuration that happens.
[SELECT_MATERIAL:HAIR]
[STATE_NAME:ALL_SOLID:wool]
[STATE_ADJ:ALL_SOLID:wool]
[YARN]
A inventive use to put foward for this is to cut off one a tame hydra's heads entirely in order to harvest it (I don't know if you could extract teeth or additional materials from that but its a neat way to cheat leather for the effort of taming one, once you have the head i guess you can set up seperate reactions to remove parts from it by using HYDRA:HEAD or something like that as a reagent.)
Using a similar template from cows, you can also create milking reactions using the same logic as for a specific shearing action on a material. However it will dump the contents into a bucket, which will probably need a separate reaction to empty into a barrel, and the milking regardless of material is periodic rather than re-usable, even if the actual contextual source is infinite.
[USE_MATERIAL_TEMPLATE:MILK:MILK_TEMPLATE]
[STATE_NAME:ALL_SOLID:frozen cow's milk]
[STATE_ADJ:ALL_SOLID:frozen cow's milk]
[STATE_NAME:LIQUID:cow's milk]
[STATE_ADJ:LIQUID:cow's milk]
[STATE_NAME:GAS:boiling cow's milk]
[STATE_ADJ:GAS:boiling cow's milk]
[PREFIX:NONE]
[MILKABLE:LOCAL_CREATURE_MAT:MILK:20000]
[USE_MATERIAL_TEMPLATE:CHEESE:CREATURE_CHEESE_TEMPLATE]
[STATE_NAME:SOLID:cow cheese]
[STATE_ADJ:SOLID:cow cheese]
[STATE_NAME:SOLID_POWDER:cow cheese powder]
[STATE_ADJ:SOLID_POWDER:cow cheese powder]
[STATE_NAME:LIQUID:melted cow cheese]
[STATE_ADJ:LIQUID:melted cow cheese]
[STATE_NAME:GAS:boiling cow cheese]
[STATE_ADJ:GAS:boiling cow cheese]
[PREFIX:NONE]
As a cursory suggestion, if you use bucket and barrel materials with a set temperature (such as nether cap retaining a fixed heat temperature) and find a way to package your product into the bucket/barrel very quickly, you can retain the heat/cold of a product indefinitely, in the case that you wanted to make a creature you could milk for a very hot substance or a very cold one (whipped cream magic cows that dispense almost ready to eat, with a little prepping, ice cream anyone?)
My own reactions question, can you extract bones specifically from a corpse? Leaving it as meat and skin and probably collapsing upon itself?