The teat should resemble the mother's in size and shape to ensure mouth comfort, fit and correct tooth eruption, There is no hole in the teats, so the carer needs to make a hole to suit the animal being fed. Pierce the tip of the teat with a hot needle to make a hole about 1 mm in diameter, or for large animals, cut a hole with scissors. If the hole is too small, excessive sucking will quickly weaken the tip and the end will blow out. If this is happening then the hole is probably too small for the animal. Make a larger hole. The hole should be large enough for milk to drip out slowly, when the bottle is inverted.