I've written about soil, sulfur and Methionine deficiency often. But everything I see says it's getting worse. - Dr. Eleanor Kellon, Staff Veterinary Specialist for Uckele Health & Nutrition

Methionine is an essential amino acid, meaning horses must get it from their diet. It is critical in protein synthesis since many proteins start with methionine and without it synthesis will stop.

Methionine is the king of the sulfur-containing amino acids which give strength to hair, hoof horn, skin and tendons/ligaments. It is the precursor for SAM-e, a mood stabilizer, and the major antioxidant glutathione.

Methionine is a methyl donor required for the synthesis of L-creatine and L-carnosine. These compounds are critical to muscle function and athletic performance.

Soybean, peas and beet pulp are poor methionine sources. Historically, grains, brans and other seed meals were adequate sources. Hays easily met the 0.2% sulfur content most authorities recommend to support production of good levels of sulfur-containing amino acids. This is changing.

I am increasingly seeing hay analyses with sulfur below 0.2%, even below 0.1%. This means soil levels are low so grains will also be affected. What’s going on?

Read more: An Equine Methionine Crisis is Brewing

Iron deficiency anemia does not exist in adult horses. - Eleanor M. Kellon, VMD

It's common knowledge that horses with anemia and performance horses should get iron supplements to build their blood – right? Wrong!

Close to 70% of the body's active — not stored — iron is in the red blood cell pigment hemoglobin where it functions to bind oxygen from the lungs and carry it to the tissues. Iron is also the active binding element of myoglobin, the pigment that makes muscle red and acts to temporarily store oxygen in muscle and deliver it to the aerobic metabolic pathways for generation of energy. Iron is an indispensable component of hundreds of other proteins and enzymes in the body.

The body also takes advantage of iron's high reactivity to shuttle free electrons in the chain reaction that generates energy from foods in the form of adenosine triphosphate (ATP). A few antioxidant enzymes also use iron, and iron is used in body systems that detect dangerously low levels of oxygen.

However, iron's free and easy contribution in free radical reactions can have a black side. In white blood cells it is used to generate free radicals which are used to destroy invading organisms. When unchecked, that same capacity to generate free radicals can easily damage tissues.

While horses can be anemic for a variety of reasons, iron deficiency is not one of them. Except for foals raised in stalls with no access to dirt, iron deficiency anemia has never been found in a horse.

Read more: Beware Supplemental Iron