In my single player world I have a barn with all vanilla animal types. Cows, sheep, chickens, pigs, and rabbits. After installing quark I updated my barn to include iron grates both in a 3 block pattern outside the fence gate and one under the fence gate so I would have less issues with escape when I went in the pen.

All the animals react to the iron grates correctly and it blocks them except for pigs. Pigs walk over the grates normally as if they were any other block. Haven’t tested with any other animals that I haven’t already listed so I’m not sure about horses or any other non farm animals.

Edit: small correction after a little testing - it appears to only be baby pigs that ignore it.

Still seems to happen for baby pigs in the latest. Oof.

Happens with Baby Chickens too. This happens because Baby Chickens and Baby Pigs' stepHeight is greater than their height, and the bounding box calculation doesn't really expect this, so they can just walk under the bounding box. https://github.com/Vazkii/Quark/blob/1.15/src/main/java/vazkii/quark/building/block/GrateBlock.java#L53

Issue can be closed, not reproducible on 1.16.5 r2.4-311