Okay it is a perk, but I could have sworn it had it's own description which you can't get back once you lose it. I've been hesitant to to breed with the Zil because of this. The last time this happened was when my demoness lost her 14 vestigial horns in CoC. I quit playing because of that.Isn't treated milk a perk though from the treatment meaning it can't be lost.