Which statement about nitrates and ruminants is accurate?

• A. Ruminants are less susceptible to nitrates than monogastrics.
• B. Ruminants are more susceptible to nitrates than monogastrics because their rumen reduces nitrates to nitrites.
• C. Nitrates pose no risk to either ruminants or monogastrics.
• D. Nitrates toxicity affects only monogastrics.

Answer: (B)

Nitrates become a problem in ruminants because of what happens in the rumen. The bacteria there readily convert ingested nitrate (NO3−) into nitrite (NO2−). Nitrite, when absorbed, oxidizes the iron in hemoglobin from Fe2+ to Fe3+, forming methemoglobin. Methemoglobin cannot carry oxygen effectively, so tissues don’t get enough oxygen, causing weakness, rapid breathing, and potentially death. Monogastrics lack this extensive ruminal nitrate-to-nitrite conversion, so they’re less susceptible under the same exposure. Therefore, the accurate statement is that ruminants are more susceptible to nitrates than monogastrics because their rumen reduces nitrates to nitrites.