it works i have a horse who was lvl 1 with 6 amity i gave it the potential pill now its lvl 3 with 8 amity. :D
http://wlodb.com/files/at_lvl_3_with_8_amity.png

when he lvl up to 4
http://wlodb.com/files/lvl_4_with_9_amity.png

and final proof at lvl 5.
http://wlodb.com/files/finally_lvl_5_with_10_am...

i had to use a exp statue at lvl 3 to speed up the lvling but at that low amity my horse would of ran away. but thanks to potential pill it stayed :D.