The correct answer is option 3: By allowing the cattle to graze in the fields.

Option 1 suggests that increasing the supply of feed concentrate can reduce fodder consumption, but it does not necessarily increase milk production. Feed concentrate alone may not provide all the necessary nutrients for cows to produce more milk.

Option 2, stall feeding, may help reduce fodder consumption, but it does not necessarily increase milk production. Cattle may not have access to fresh grass and other nutrients that they would get from grazing in the fields.

Option 4, administering hormones, may potentially increase milk production, but it does not directly reduce fodder consumption.

Allowing the cattle to graze in the fields (option 3) is the most effective method as it allows the cows to consume fresh grass and other natural vegetation, reducing the need for additional fodder inputs and promoting higher milk production due to a balanced and natural diet.