For example. If a girl has the trait lactating and during sex you would add in the she does something with that because she has the trait.
Looking over the code, there are a few places where the lactation stat is used in the game.
The traits "Dry Milk", "Scarce Lactation", "Abundant Lactation", "Cow Tits" and if she is pregnant are used to calculate the lactation stat. (If she has "No Nipples", she does not lactate.)
If you want me to add any text to the game, attach a text file to a post and I will add it in.
Or you can edit the source code on github and make a push request.
If you are only using it for a script, then it should just be a matter of playing with the lactation stat.