Which horse condition requires the highest nutritional level?

The condition that requires the highest nutritional level is a lactating mare eight weeks postpartum. During this time, the mare is not only recovering from the demands of pregnancy and foaling but is also producing milk to nourish her foal. This process requires substantial energy, protein, vitamins, and minerals to ensure both her health and the healthy development of her foal.

Lactating mares have a unique nutritional requirement as their bodies must support milk production, which is rich in nutrients essential for the foal's growth and development. A mare in this condition is typically in a state of high demand for quality forage and concentrated feeds to maintain her body condition and support lactation effectively.

Compared to other options, while weanlings, growing yearlings, and working horses also have significant nutritional needs, they do not match the critical demands of a lactating mare at this stage. Weanlings and growing yearlings are focused on development and growth, while working horses typically require energy for labor but do not face the same level of nutritional demands associated with lactation. Therefore, lactating mares are the group that requires the highest nutritional level to thrive during this vital period.