Upwards of nine-gallons, every day (that’s a lot of milk), though it depends on the cow:
It depends on the breed. Holsteins will produce around 75 pounds or 9 gallons of milk a day. Jerseys will produce around 21 pounds or 2.5 gallons a day. Angus cows will produce only around 10 pounds a day (1.2 gallons a day), and Herefords a little less. The two former breeds (Holstein and Jersey) are dairy cattle, and the latter two breeds (Angus and Hereford) are beef cattle.
However, it also looks like the growth hormones have doubled the yield:
It totally depends on the breeds of cows used for milking. Dairy cow milk yield has increased from an average of 3,750 litres per cow per year (12 litres/21 pints per day) in the 1970s to 7,445 litres (24.5 litres/42 pints per day). One of the highest yielding cow breed is Dutch Holstein Friesian cows.
Apparently this is significantly more than a calf actually requires:
The figures above reflect only the average per cow, some individual cows may produce significantly more but either way it equates to seven to ten times more than a cow would naturally produce to feed her calf.
The featured image is a rotolactor, which is a large, circular, rotating wheel that holds many cows. The original design went into production in 1930 and was designed for fifty cows:
The Rotolactor (roto + lactor ium) was a large rotating “merry-go-round” style platform for holding 50 cows. The machine brought the cows into position for milking with automatic milking machines. The rotating platform machine was sixty feet in diameter and made one complete revolution about every twelve and a half minutes. The twelve and a half minutes was the time required to prepare and milk each cow.
The first step for each new cow was receiving a bath. The cows were bathed with warm water and automatic showers, supplemented by two men using pressure hoses, who “devote their attention to the cleansing of udders and flanks.”
The next operator prepared the udder for milking. Then the teat-cups of the automatic milking machine are attached to the cow’s udder. The cow is then milked for the twelve and a half minutes during the Rotolactor’s one-time complete rotation. The teat-cups would then be detached at the end of the twelve and a half minute rotation. The cow would then step off the platform and return to the barn to her stall.
The milk was drawn by a vacuum to sealed glass containers above the cow’s head. It is then transported in pipes to weighing and recording apparatuses. Then it is piped to another room where the milk is cooled and bottled. This was faster and more efficient than the old methods previously used. Human hands never touched the milk and the milk never came into contact with air. It was important for the milk not to contact air to prevent premature spoiling. The Rotolactor could milk the Walker-Gordon dairy’s 1,680 cows three times daily. This produced 26,000 quarts of milk.
To be honest, I am still confused about why they have a wheel, since it seems like they are only milking one cow at a time (which is how it sounds but probably my misinterpretation). Leave a comment if you have any useful insights.