I have grinded up to 600+ days already.
I can make all of the special slave get pregnant with 3 pregnancy.
Remember that it is not just your slaves that needs upgrade. You also need to upgrade your monsters.
I got my monsters with maxed out stats with the help of the special slave dragonian offspring with high stats.
To give you an idea on how I got my bunny get multiple pregnancy with higher luck, you got to feed her a lot before she can do multiple pregnancy. A mere 100 milk won't get you anywhere since I fed mine more than 5000 already with no cheat and still has around 60% chance of 3 pregnancy. Here are her stats.
All of my monsters have maxed out stats. And my special slave currently has higher stats than normal specially my Inu
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