I want to buy a twenty liter cow.

For a twenty liter dairy cow, look at HF cross, Jersey cross, Sahiwal, or Gir. First milk her in your presence, then do a CMT test on all four quarters, and ask which month of lactation she is in. If she is in month seven or eight, today’s yield can fall fast. For any cow above fifty thousand rupees, take a Pashumitra or vet with you before paying.