Minimizing the risk for rumen acidosis.

Ruminal acidosis is a common disease in high yielding dairy cows, during which the rumen pH is depressed for several hours per day. There is no general agreement of the definition of the disease, and its diagnosis based on rumen pH measurement is invasive and inaccurate. As a result, the disease often goes unnoticed, and its impact is not well recognized. Surveys suggest a prevalence of between 19 and 26% in early and mid-lactation dairy cows in North America. Many symptoms have been attributed to subacute rumen acidosis (SARA), including feed intake depression, milk fat depression, reduced fiber digestion, inflammation of the rumen, systemic inflammation, dehydration, diarrhea, laminitis, liver abscesses, and increases in the concentrations of bacterial toxins in digesta throughout the digestive tract. These symptoms are not always obvious. The mechanisms of how, and even if, the rumen pH depression causes these symptoms are not always well understood. Cows may very in their susceptibility to ruminal acidosis. Preventing ruminal acidosis requires formulating diets that contain enough coarse (physically effective) fiber and do not contain excessive amounts of rapidly-fermenting nonfiber carbohydrates. In addition, these diets must be ingested by the cows in the way they were formulated, which involves preventing mixing errors, excessive mixing, and sorting by cows. The inclusion of buffers, e.g. sodium bicarbonate, and yeast in the diet can prevent rumen acidosis, as does adaptation to high grain diets during the last part of the dry period. Feeding strategies, such as frequent feeding, continuous availability of feed, and sufficient bunk space, spread out meals throughout the day, and reduces the risk of ruminal acidosis.