Those pads are a little more plump than what I'm used to seeing. Does the white stake tell you it is opuntia?
If you were to put your tongue on the glichids on that plant you would end up with a hundred and fifty million tiny little stickers in your tongue. But for some reason, tortoises can eat cactus with spines and it doesn't affect them.
Nice pads, Here is one that I have that is close to what you have, If you live in a warm climate, go ahead and plant them in the ground and let them go. They will produce more new growth in the ground than being in pots. Your tortoise will love it.