Acidosis

What is Acidosis?

Acidosis is a metabolic disorder that occurs when the rumen pH drops below normal (6.0) due to excessive production of volatile fatty acids (VFAs) — primarily lactic acid — from rapid fermentation of high-starch concentrates. It ranges from subacute ruminal acidosis (SARA, pH 5.2–5.5) to acute clinical acidosis (pH <5.0), which can be fatal.

SARA is the most common form, affecting 15–30% of high-producing dairy cows. It occurs when cows consume too much grain too quickly, or when the forage-to-concentrate ratio is too low (<40% forage). The resulting acid damages the rumen wall, reduces fiber-digesting bacteria, and allows harmful bacteria to proliferate.

Clinical signs of SARA include: reduced feed intake, intermittent diarrhea (loose, frothy manure), reduced milk fat test (milk fat depression), weight loss, and lameness (from laminitis). Acute acidosis presents with: complete feed refusal, severe dehydration, rumen atony, and potentially death from endotoxemia or liver abscesses.

Prevention is the primary management strategy: maintain adequate effective fiber (>28% NDF from forage), limit concentrate per feeding to 0.5% of body weight, feed TMR to prevent sorting, avoidslug feeding, and work with a nutritionist to balance ration fermentability. Transition cows gradually to higher concentrate levels over 7–10 days.