Effect of high oral doses of Nitrate on salivary recirculation of nitrates and nitrites and on bacterial diversity in the saliva of young pigs

Ingested nitrate is absorbed in the small intestine, recirculated into the saliva and reduced to nitrite by oral bacteria. In pigs receiving a moderate dietary addition of nitrate, the recirculation into the saliva is modest, so we aimed to assess the effect of higher nitrate doses to find out how the animal reacts to this new situation and to evaluate if a higher nitrate level could enhance the nitrate reduction process, improving the nitrite production Trial 1. Six piglets received 100 g of a commercial diet with 2.45% KNO3. Compared to baseline values, nitrate in blood serum and saliva increased 15 times, and declined after 6h Vs. 2h. Salivary nitrite increased 7 times after the addition and declined after 6h Vs. 2 h. Trial 2. Six piglets were fed a diet with or without 1.22% KNO3 for 2 weeks. Salivary nitrate and nitrite increased with the addition of KNO3: nitrate increased from d0 to the end of the trial, nitrite increased fifteen times after one week, but decreased after 2 weeks to 4.5 fold the control. After two weeks nitrate reduced Shannon’s diversity index of salivary microbiota. The present results indicate that the long exposure to high quantities of nitrates impairs the oral reduction of nitrate to nitrite and engenders a reduction of the mouth’s microbiota diversity.