However, a protein deficiency will occur if the increased energy requirements of the working pony are not met. In such cases, body fat is first metabolized, and then muscle is broken down to sustain the animal. They also have many important roles in metabolism. Plants absorb minerals from the soil and are, therefore, subject to local variations. For example regionally, western Newfoundland has a selenium deficient soil.
Animals receive an inadequate level of selenium from locally grown forage.
Mineral supplementation is often necessary but should be done with caution since oversupplementation can cause toxicity. Calcium, phosphorus, and salt are minerals that require special attention. The calcium and phosphorus requirements of ponies is dependant on the age and function of the pony. Young, growing ponies, pregnant mares, and nursing mares have high requirements for calcium and phosphorus. There is no increase in requirement for the working pony.