Calves should stand and nurse within 2 hours of birth if everything is normal and weather is not severe. For maximum antibody exposure from the colostrum, calves need to nurse within four hours of birth.Cows should be checked to see if they have been nursed or calves should be assisted in nursing.alves should stand and nurse within 2 hours of birth if everything is normal and weather is not severe. For maximum antibody exposure from the colostrum, calves need to nurse within four hours of birth. Cows should be checked to see if they have been nursed or calves should be assisted in nursing.