That's not steep... At least not when your classes end this week giving you over a week of nothing but df time!
My attempt will be sans cheating or modding, since those would ruin the whole point of the competition IMO*. After all, anyone could go change all stone layers into soap and completely defeat the purpose of the excercise.
At the moment, I have all the infrastructure to make soap... These animals just aren't quite frisky enough. I started with about 10, now im at 40 about a year later. It would seem to keep the fat supply large enough I will have to wait at least another year until I have enough that the exponential nature of reproduction in DF kicks in. I just have to be careful to keep the population of them well controlled else I may surpass critical mass and cause an unstoppable cowsplosion.
Edit: it seems those crafty humans are trying to tempt me. They are offering almost 200% increase prices on my soap in an attempt to thwart my plans to create a soap tower. And my first batch of cows are maturing!
Edit 2: 120 animals, about 100 of which are cows or other large things... still maintaining 100 fps by turning off temp and weather.
*Note: opinion may change after first or second tantrum cycle.