Generally, a baby calf will instinctively return to its mother for nursing after having nursed from another cow or after any other separation. Calves have a strong bond with their mothers and can often recognize them by smell and sound. However, if the calf has established a nursing relationship with another cow, it might take a little time for it to adjust back to nursing from its mother, especially if it has become accustomed to nursing from the other cow.
In most cases, the mother cow will recognize her calf and allow it to nurse. If there are no complications and both animals are healthy, the calf should eventually return to the mother for nourishment. It's important for farmers or caretakers to monitor the situation to ensure both the calf and the mother are comfortable and to intervene if necessary to facilitate the bonding process.