zombiefied piglings spawning way too much from portal

So this has happened to me many times, i dont know if its a bug but as you can see on the image zombiefied piglings keeps spawning when the portal is active. Way too much. So we always have to unactivate the portal so we dont have to keep getting rid of piglings that keeps spawning every sec. Please fix this soon because we cant really go to the neather as this keeps happening everytime we activate the portal.