Feeding hay or dry fodder helps the cow in regurgitation which helps in digestion process and absorption. A mixture of Brans(Rice bran, wheat bran) and Cakes (coconut, gingelly, groundnut) along with cotton seed cake in crushed form after soaking it in water is very good for cows. Tapioca in dried form is also seen in some areas for feeding cows, which is rich in starch.
quote author=niksnarayana link=topic=155.msg18503#msg18503 date=1413512776]
Some quick calculation.
A cow should be fed around 2.1% of its body weight in Dry Matter (DM) for body maintenance and another 0.3 kg per liter milk production.
So for Jersey with 400 kg body weight,
Body Maintenance = 2.1% * 400 kg = 8.4 kg DM
Milk assuming 18 liters per day = 0.3 * 18 = 5.4 kg DM
Napier has 20% DM, which means 40 kg Napier will provide 8 kg DM to the cow.
Plus 5.4 kg of concentrates with minimum 20% Crude Protein. Roughly I can say a basic mix of 4 kgs of Wheat Bran, Maize Powder etc and around 1 kg Groundnut cake or similar cake. Oil cake is important as it will provide high protein which is missing in your fodder as well as basic concentrate mix.
Use 100 gm mineral mix per cow. Also use Sodium Bicarbonate 50 gms per cow. If you are comfortable using Urea, that is also good source of protein, should not exceed 100 gms per cow per day.
I doubt whether the cow will be able to consume 40 kg of green fodder, you may have to reduce it to 30 kg and include some dry fodder to compensate for DM.