Cows need a certain amount of fibre to ensure rumen fuctions properly. Minimum fibre requirements for cows are shown below:
Fibre measurement vs minimum amount of dietary fibre (%DM)
Neutral Detergent Fibre: 30%
Acid Detergent Fibre: 19%
Crude Fibre: 17%
Low fibre, high starch diets will cause the cow's rumen to be acidic.
Grain poisoning, also known as acidosis my occur.
One way to combat this is by adding buffers such as sodium bicarbonate to the diet to help reduce acidity.
Buffers are usually recommended when grain feeding per day is more than 4 - 5kg grain/cow.
Buffers are not a substitute for fibre.
Hence, long term feeding of low fibre diet should be avoided if possible.