Chapter 12 final.pages

Sulfur (S) is an essential mineral for animals and serves many important biological functions in the animal’s body. However, when excess S is present in ruminant diets, neurological problems can occur. When feed and water containing high levels of S (greater than 0.40% of diet DM) are fed to ruminants, a condition called polioencephalomalacia (PEM) can occur. Polioencephalomalcia is caused by necrosis of the cerebrocortical region of the brain of cattle, sheep, and goats. When S is consumed by ruminants, it is reduced to hydrogen sulfide by ruminal bacteria. Hydrogen sulfide is toxic and accumulation in the rumen is thought to be the cause of these toxic effects. Ruminants are more vulnerable to PEM when their diets are abruptly changed from a primarily forage diet to a primarily grain diet. This causes a dramatic shift in rumen microbial populations that produce thiaminase, resulting in a thiamin deficiency. Sulfur also appears to have a significant role and interaction with thiaminase production to cause this condition, but the mechanism is not well understood. In addition, excess dietary S can interfere with copper absorption and metabolism. As a result, when high dietary levels of S are fed for an extended period of time, dietary copper levels should also be increased (Boyles, 2007). This condition does not occur in non-ruminant animals (pigs, poultry, fish).