Interpretive Summary: Supplementing a blend of magnesium oxide to feedlot cattle: effects on ruminal, physiological, and productive responses

By: Eduardo A Colombo, Reinaldo F Cooke, Ana Clara R Araújo, Kelsey M Harvey, Ky G Pohler, Alice P Brandão

Acidosis is a common digestive disorder in feedlot cattle consuming high-grain diets, resulting in excessive accumulation of organic acids and pH reduction in the rumen. Sub-acute acidosis is the most prevalent form of acidosis in feedlot cattle, and it is difficult to diagnose due to limited clinical signs, but directly impairs cattle health and productivity. This study evaluated the inclusion of a blend of magnesium oxide (MG) into feedlot diets, a novel neutralizing agent to control rumen pH and mitigate sub-acute acidosis. More specifically, cattle received a corn-based diet with the inclusion of MG at different levels (0%, 0.25%, 0.50%, or 0.75% of the diet). Ruminal pH increased as dietary MG inclusion increased, particularly as cattle consumed feed toward the end of the day. Concentrations of plasma haptoglobin and cortisol in the tail-switch hair decreased as dietary MG inclusion increased, indicating that MG supplementation reduced inflammatory and chronic stress resultant from sub-acute acidosis. However, no benefits from MG were noted for cattle productive traits, including growth rate, feed efficiency, and carcass merit traits. Therefore, supplemental MG appears to be effective in controlling rumen pH in cattle receiving a corn-based finishing diet, but without improvements in feedlot performance and carcass quality.

The full article can be found on the Journal of Animal Science.