I know people do keep a solitary house cow with only her calf for company, but the Welfare Codes for Cattle do state that bovines should always have the company of another bovine at their own age and stage. So in reality, it's not really high welfare unless you have two cows and two calves, sorry. You probably don't have enough ground for two, even if you chose Dexters. Especially if it's wooded, rather than all pasture.
Have you considered goats?