Solved how to add a potioneffect to an entity

hey guys does anyone have an idea on how to change the speed of a pig that's being ridden?
i've already tried

Code:

this.addEffect(new MobEffect(MobEffects.a, 1000000, 2));

but it only works when the pig is free, eg. the pig isn't being ridden, so while i'm luring it with a carrot, it is faster than the player, but when i start riding it and get the carrot on a stick in my inventory, it's slow af, completely ignoring the potion effect the pig has