The Low Prim Mode is available in the Big Cats, Wild Dogs and the Wild Mustangs it is not available in the Little Varmints. The Low Prim will take and put the animal either in a crate, a box or a stall. Removing the animals ability to walk about the area. The animal will still have some animations but the most of them have been stripped out to reduce the amount of prims it takes up.
To reverse this you need to go to the website and log in to the various dashboard for the animal you want to reverse the mode to and use the webMOOG~Animal. This will send you a box to rezz to the ground and it will remake the animal in a full prim version.
If you do not have a log in for the website you can gain access to the website by clicking the sign at any of the stores that says Register for the Portal. This is a free service we offer our clients.