One must meet the foal's nutrient needs for maintenance and growth. But, some owners feed too much feed to weanlings opting for extra growth for halter futurities and sales. They think that bigger and fatter is better. Overfeeding can mean too much feed, especially grain or concentrate, or too much of a specific nutrient. Where an excess or deficiency of a nutrient exists, the ration is imbalanced.
Imbalanced rations cause problems, especially in growing animals.
Common imbalances are feeding weanlings excess energy or protein. Energy is not a nutrient. But, carbohydrates and fats, as nutrients, provide energy. If fed in excess, protein is used as energy and stored as fat. Animals eat less feed, not more, when protein is limited.