Organic mineral sources represent another option for producers to supply minerals to their cowherds. Research suggests that some organic mineral sources are indeed more bioavailable; however, production responses to supplementation have been extremely variable. Positive responses to organic mineral supplementation are most likely, although not guaranteed, during stressful periods in the production cycle (i.e., calving and weaning) or when mineral antagonists (i.e., sulfur, molybdenum, iron, or aluminum) are present in large amounts. In these situations, producers should objectively weigh any expected benefit to animal performance against the added cost of including organic minerals in their supplementation program. If there is currently no problem with any production measure (i.e., reproduction, health, or weight gain), it is highly unlikely that there will be any benefit from feeding organic mineral sources.