Effects of Dietary Protein and Energy Levels on the Reduction of Nitrate and Nitrite in the Rumen and Methemoglobin Formation in Sheep

Abstract

A 4×4 factorial experiment was conducted to investigate the influence of dietary factors on ruminal nitrite accumulation and methemoglobin formation in ruminants. Four adult Corriedale wethers equipped with permanent rumen fistula were assigned to four rations with different levels of protein and energy: R-1 (TDN 100%; DCP 100%), R-2 (TDN 50%; DCP 100%), R-3 (TDN 100%; DCP 500%) and R-4 (TDN 50%; DCP 50%) based on NRC feeding standard. All animals were administered intraruminally 30g. of sodium nitrate as 30% (w/v) aqueous solution via fistula. No appreciable difference was observed in the process of the disappearance of nitrate nitrogen in rumen among different levels of the nutrients intakes. Following the intraruminal administration of sodium nitrate, relatively higher accumulation of nitrite nitrogen was shown on the rations of low TDN level. Additionally, maximum accumulation of ruminal nitrite was significantly high (P<0.05) in the animals fed R-2 ration. Plasma nitrite increased as DCP consumption increased. Methemoglobin formation was enhanced on the ration of low TDN and high DCP levels, whereas on the ration of high TDN and low DCP levels it was lowered. Erythrocyte reduced glutathinne concentration decreased 20-60% from its normal average value of 1.5μmole/ml cells with the administration of nitrate, although there appeared to be no significant difference among treatments. Jpn. J Zootech.