Ruminal pH in Severe Grain Engorgement

In severe grain engorgement, the ruminal pH becomes:

Correct Answer: 4

In severe grain engorgement (grain overload / rumen acidosis / rumenitis), the ruminal pH drops dramatically to 4 or below. This is caused by massive overproduction of lactic acid by facultative anaerobic bacteria (Streptococcus bovis, Lactobacillus spp.) when animals consume large amounts of rapidly fermentable carbohydrates (grains).

Normal vs. Pathological Ruminal pH

Pathogenesis of Grain Engorgement

1. Excess grain → rapid starch fermentation → lactic acid overproduction.
2. Lactic acid accumulates → pH drops to ~4.
3. Low pH kills normal rumen bacteria (gram-negative obligate anaerobes) and protozoa.
4. Osmotic pressure increases → fluid drawn into rumen → bloat, dehydration.
5. Lactic acid absorbed → systemic metabolic acidosis.

Why Other Options Are Wrong

• pH 6 → Sub-normal but not severe; SARA range, not acute engorgement.
• pH 7.5 → Above normal rumen pH; seen in rumen alkalosis (urea toxicity), not grain overload.
• pH 9 → Extremely alkaline; this would represent severe urea toxicity or alkalosis, not grain engorgement.