When our kids were teenagers [they're now all in their 40's] they had a couple of horses and a donkey.

My involvement included administering worming paste - ?? ivermectin??

Horses were OK. Shove the tube to the back of the tongue and 'download' it.  Horse didn't seem to mind.

But the donkey!  He knew what was going on before you got near him!

When you finally got enough strength to get it into his mouth and 'download' he would immediately drop to his knees and wipe his mouth in the dirt. Quite funny and a comic relief after the battle of getting it into him!