Nitrate reduction in the rumen of the grazing sheep

Abstract

Nitrate, a normal component of pasture, shows marked fluctuations in its concentration in the plant. Nitrate and comparatively smaIl amounts of nitrite have been detected in the rumen contents of sheep on such pasture.The effect of adding moderate amounts of nitrate to the rumen of the grazing sheep has been studied. The rumen of the sheep on pasture is capable of handling comparatively large amounts of nitrate under normal circumstances without noticeable ill-effect. Any adverse effects due to the oxidising nature of the nitrate ion were surmounted within three to four days. The results reported tend to indicate a slight stimulation of rumen function after continuous daily nitrate dosing. Under such conditions the sheep exhibited a sustained but fluctuating methaemoglobinaemia with peak values of about 35% conversion of total haemoglobin to methaemoglobin.

Nitrate and Inhibition of Ruminal Methanogenesis: Microbial Ecology, Obstacles, and Opportunities for Lowering Methane Emissions from Ruminant Livestock

“…Nitrate tastes bitter, which lowers palatability of nitrate-based diets and may cause lower feed intake or feed sorting ( Miyazaki, 1977 ; Lee et al, 2015b ), but it is the high nitrate composition of certain plants, such as sugar beet leaves and certain grasses, and the subsequent poisoning of animals consuming these plants that has been of greatest concern ( Miyazaki, 1977 ; Dawson et al, 1997 ). The reduction of nitrate and accumulation of nitrite in the rumen were first detected by Sapiro et al (1949) and Lewis (1951) , with the observations being followed up in detail by Holtenius (1957) , Jamieson (1959) , and Wang et al (1961) . Nitrite is absorbed across the rumen wall into the blood where it interacts with hemoglobin in the erythrocyte to form methemoglobin ( Lewis, 1951 ; Holtenius, 1957 ; Jamieson, 1959 ), which is incapable of carrying oxygen.…”

“…The reduction of nitrate and accumulation of nitrite in the rumen were first detected by Sapiro et al (1949) and Lewis (1951) , with the observations being followed up in detail by Holtenius (1957) , Jamieson (1959) , and Wang et al (1961) . Nitrite is absorbed across the rumen wall into the blood where it interacts with hemoglobin in the erythrocyte to form methemoglobin ( Lewis, 1951 ; Holtenius, 1957 ; Jamieson, 1959 ), which is incapable of carrying oxygen. The nitrite arising from nitrate reduction is therefore toxic and the consequences of nitrate can be fatal ( Cockburn et al, 2013 ).…”

Nitrate poisoning in cattle. 2. Changes in nitrite in rumen fluid and methemoglobin formation in blood after high nitrate intake.

“…x & i-* * * _J ' ' L work of Jamieson (1959), Simon et al (1959), Davison et al (1962), Mcllwain et al (1963), Winter et al (1964) and Davison et al (1965), sometimes done with another object in view, the sampling of rumen fluid and blood were mostly carried out at intervals of one or more weeks. Nakamura et al (1976) record data on changes occurring in the methemoglobin content in the blood of sheep during the first week after dosing nitrate.…”

The effects on ewes and lambs of grazing pasture containing differing levels of nitrate‐nitrogen

“…Large amounts of nitrate given under ad libitum feeding failed to induce signs of poisoning (Dollahite and Holt, 1970) whereas single doses of t-t of such amounts did so. Sustained high doses of KN0 3 resulted in only temporary disturbance of the rumen flora and the efficiency of fermentation (Jamieson, 1959) which led to the conclusion that the grazing sheep is not seriously at risk from high nitrate-N grass because of the slow rate of intake of nitrate-N and the rate of degradation of the grass in the rumen. The work reported here supports that conclusion.…”