Here in BC a cow can produce as much as 30 litres of milk a day and almost 9500 litres of milk a year.
The amount of milk that a cow can produce is dependent on many things like nutrition, breed and age. To produce milk cows must eat the a well balanced diet, so farmer's and nutrition specialists work very hard to ensure that all the cow's nutritional needs are met.
Different breeds produce different amounts of milk and have different levels of protein and fat in the milk that they produce. For example, around 95% of dairy cows are Holsteins (the black and white cows) and this breed produces the most milk of all the dairy breeds. Jerseys (the light brown cows) produce less milk but they have more fat in their milk.
As a cow gets older, she will often produce more milk because she isn't putting a lot of energy into growing (like young animals) and can use that energy to produce milk.
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