We raised 75-100 baby calves per year when we had the dairy, for about 30 years. We never used a nipple. We took the calves from the cows at 3 days old, used the bucket from the first feeding, using our fingers to coax them to drink. After a week, we would have them in groups of 4-6 and pour the milk in the trough and they would drink together. Sometimes, the slow drinkers would have to be put together to keep from getting shorted on milk. They had all the grain and soft hay they could eat and we would wean at 8 weeks. Now that is shortened due to high cost of milk replacer. I know the bottle and nipple would have given each calf an exact amount, but there was never enough time to feed them individually.