you must wean this calf. if you dont wean this calf and turn it back out with the cows it will be sucking on which ever cow will let it till who knows when.first of all if its on two acres of grass and the grass is of good quality, the calf should not need any milk. it might need protien supplement, to supplement the grass if it is not good quality. protien will make it eat more thus keeping it from losing weight and maintain her proper growth. if you want to get it started on grain put it in a small pen with shelter and fresh water. give it good quality hay, high in protien. give it access to grain or commercial feed. sprinkle dry milk replacer on top of grain or feed. do not give it any more milk. keep fresh good hay in front of it at all times. when it gets hungry it will eat the grain. the odor from the milk replacer will attract it to the grain. when it starts eating remove the milk replacer from grain. do not give it anymore milk, if it is losing weight supplement with protien, such as protien tubs, protien pellets, etc. you can go ahead and vaccinate and worm the calf. if you have no pride in your livestock or work, do like the other guys said and take it to the sale barn and let somebody else fix the problem.