How did refrigeration change dairy farming?
When refrigeration arrived in the 19th century the equipment was initially used to cool cans of milk, which were filled by hand milking. These cans were put into a cooled water bath to remove heat and keep them cool till they were able to be moved to a collection facility. As more automated methods were created for harvesting milk, hand milking was replaced and, as a result, the milk can was replaced by a bulk milk cooler.
Ice banks were the first kind of bulk milk cooler. This was a double wall vessel with evaporator coils and water in between the walls at the bottom and sides of the tank. A small refrigeration compressor was used to extract heat from the evaporator coils. Ice builds up around the coils, till it reaches a thickness of about three inches surrounding each pipe, and the cooling system shuts off. When the milking operation starts up, only the milk agitator and the water circulation pump, which flows water across the ice and the steel walls of the tank, are required to cut down on the incoming milk to a temperature beneath 5 degrees.
Modern dairy farming
Modern dairy farmers use milking machines and hi-tech plumbing systems to harvest and store the milk from the cows, which are generally milked two or three times daily. In New Zealand some farmers who are looking to enjoy a better life style, are milking only once per day, exchanging a slight loss in production of milk for more leisure time. During the summer months, cows may be turned out to graze in pastures, both day and night, and are brought into the barn to be milked.