Effect of nitrate and its reduction products on the growth and activity of the rumen microbial population

Abstract

1. The nature of the digestion-inhibiting substance in Kikuyu grass (Pennisetum clandestinum, Hochst), containing high levels of nitrate, was investigated using in vitro digestibility techniques.2. Nitrite, which accumulated during the reduction of nitrate to ammonia, seemed to be the primary factor reducing digestibility. Nitrate and ammonia did not affect digestion in vitro.3. Nitrite caused a reduction in the cellulolytic, xylanolytic and total microbial population, with a concomitant reduction in cellulase and xylanase activity of the digesta.4. The mode of action of nitrite on rumen microbial growth was investigated.5. The possibility that the growth of cellulolytic rumen microbes was depressed by a reduction in concentration of essential branched-chain volatile fatty acids by nitrite was discounted.6. Although nitrite caused a marked increase in the redox potential, due to its oxidizing properties, the more-positive redox potential did not reduce the digestibility of the grass.7. The growth of three of the four major cellulolytic bacteria commonly found in the rumen was severely depressed by nitrite, while some rumen bacteria were relatively insensitive to nitrite.8. Growth inhibition seemed to depend primarily on the extent to which these microbes derive their energy from electron-transport-mediated processes.9. It was suggested that, due to the sensitivity of some rumen bacteria to nitrite, digestibility and therefore animal performance could be affected long before clinical symptoms of nitrite toxicity become apparent.

Effects of supplementation of inorganic sulfur on some biochemical parameters in Angora goat’s diet containing high nitrate levels

“…The value obtained in group NS was consistent with the report that the addition of sulfur to the ration did not affect the ammonium level of the rumen (21). It was reported that the extent to which the bacteria reduce nitrite to ammonia may be reduced if the level of ammonia in the rumen is high (22). Taking this situation into account, the fact that the groups do not have any differences with respect to ammonium nitrogen suggests that the level at which nitrite is reduced to ammonium is low since the bacteria meet their required level of ammonium nitrogen.…”

The effect of incremental levels of dietary nitrate on methane emissions in Holstein steers and performance in Nelore bulls1

“…2, feed intake was reduced with increasing levels of dietary nitrate. This may be explained by a suppressive effect of nitrite on NDF digestion in the rumen (Marais et al, 1988). Overall, the degree to which feed intake is decreased may depend on the type of diet: DMI of diets containing a greater proportion of NDF appears to be more negatively affected than DMI of high concentrate diets (Lichtenwalner et al, 1973).…”

Nitrate Detoxification of drinking water by ascorbic acid in growing rabbits.

“…The decreased digestibility of crude fibre may be due to the significant (P<0.01) reduction in the caecal bacterial population (Table 4), since the conversion of nitrate to nitrite and nitric oxide has a potential (SPEARS et al, 1977;MARAIS et al, 1988;BAIMATOV, 1991;XU and VERSTRAETE, 2001). …”