J. Dairy Sci. 87:(E. Suppl.):E13–E26 © American Dairy Science Association, 2004. Nutritional Approaches to Minimize Subacute

Lameness and subacute ruminal acidosis (SARA) both appear to be very prevalent throughout the US dairy industry. Reduced ruminal efficiency, liver and lung abscesses, and laminitis are all thought to be re-lated to SARA. Both the nutritionist and dairy manag-ers are responsible for the delivery and consumption of a ration that is likely to produce a ruminally healthy pH. Nutritionists should consider the expected amount of physically effective neutral detergent fiber provided by ration ingredients, along with their expected rumi-nal fermentabilities and resultant microbial acid pro-duction. Environmental conditions, such as heat stress, overcrowding, and uncomfortable stalls, which may al-ter feed intake patterns and animal behavior, should also be considered in ration formulation. Additional amounts of physically effective neutral detergent fiber, and/or a reduction in ruminal nonstructural carbohy-drate availability, may be warranted during times of increased animal stress. Higher levels of intake may also predispose the rumen to SARA, since salivary buffer secretion may not adequately compensate for additional acid production. Forage drymatter should be determined twice weekly, or more frequently if results vary by more than 5 percent of the dry matter value. Ration variability can be further reduced by premixing individual forages, or at least attempting to make each loader bucket of feed a uniform mix obtained from the entire height or face of the bunker silo. Ingredient se-quencing and mixing time should be standardized on a given dairy. Techniques to minimize sorting, including frequent feed pushups, the addition of water or a low dry matter by-product, and appropriate forage pro-cessing, should be adopted by managers. (Key words: dairy cow, laminitis, subacute rumen aci-dosis, physically effective NDF