I had stopped at one of my large training barns to check on their horses diets, as they had just returned from a recent show circuit. The owner said the horses were doing well, but he was going to tweak their diets just a little. He had purchased a bag of selenium from a local milling company and just wanted to top dress a little extra.
Unfortunately for him, the truth is that more is not always better. I explained how vitamins and minerals need to be kept in certain ratios and levels in order to keep horses healthy, and random adding of supplements can endanger their health. For example, copper and zinc must be kept in a 3:1 t 4:1 ratio for proper bone growth, development and maintenance. In young growing horses, having this ratio out of balance could lead to Developmental Orthopedic Diseases. I also noted that not all are horse feed supplements are created equal. In the case of minerals, organic complexed trace minerals (minerals that are tied to an amino acid) have increased bioavailability over the oxide or sulfate forms.
Horses have mineral requirements which are broken down into Micro and Macro. Macro minerals include calcium, phosphorus, sodium, chloride, potassium, magnesium and sulfur. These are required in gram amounts in the diet. Micro, or trace, minerals include copper, cobalt, manganese, zinc, iron and selenium. These are required in much smaller quantities in the diet, and are measured in “parts per million”, or ppm. A part per million is equivalent to one drop of water diluted into 50 liters (roughly the fuel tank capacity of a compact car). Micro and macro minerals play an important role in bone development, muscle, hair coat , appetite, as well as skin and hoof integrity. The key is that they must be balanced in the horses diet.