Nitrate ( ) supplementation is an effective methane (CH₄) mitigation strategy for ruminants but may produce nitrite ( ) toxicity. It has been reported that rumen protozoa have greater ability for and reduction than bacteria. It was hypothesised that the absence of ruminal protozoa in sheep may lead to higher accumulation in the rumen and a higher blood methaemoglobin (MetHb) concentration. An in vivo experiment was conducted with defaunated (DEF) and faunated (FAU) sheep supplemented with 1.8% in DM. The effects of rumen protozoa on concentrations of plasma and ruminal and , blood MetHb, ruminal volatile fatty acid (VFA) and ruminal ammonia (NH₃) were investigated. Subsequently, two in vitro experiments were conducted to determine the contribution of protozoa to and reduction rates in DEF and FAU whole rumen digesta (WRD) and its liquid (LIQ) and solid (SOL) fractions, incubated alone (CON), with the addition of or with the addition of . The results from the in vivo experiment showed no differences in total VFA concentrations, although ruminal NH₃ was greater (p < .01) in FAU sheep. Ruminal , and plasma concentrations tended to increase (p < .10) 1.5 hr after feeding in FAU relative to DEF sheep. In vitro results showed that reduction to NH₃ was stimulated (p < .01) by incoming in both DEF and FAU relative to CON digesta. However, adding increased (p < .05) the rate of accumulation in the SOL fraction of DEF relative to both fractions of FAU digesta. Results observed in vivo and in vitro suggest that and are more rapidly metabolised in the presence of rumen protozoa. Defaunated sheep may have an increased risk of poisoning due to accumulation in the rumen.

中文翻译：

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日粮硝酸盐和原生动物的存在会增加绵羊瘤胃中硝酸盐和亚硝酸盐的减少。

硝酸盐（）补充是反刍动物有效的甲烷（CH ₄）缓解策略，但可能产生亚硝酸盐（）毒性。据报道，瘤胃原虫有更大的能力和减少比细菌。假设绵羊中没有瘤胃原生动物可能导致瘤胃中更高的积累和更高的血液中血红蛋白（MetHb）浓度。对补充有1.8％DM的去羊（DEF）和动物群（FAU）绵羊进行了体内实验。瘤胃原虫对血浆和瘤胃的浓度的影响和，血MetHb，瘤胃挥发性脂肪酸（VFA）和瘤胃的氨（NH ₃）进行了调查。随后，2体外实验以确定原生动物的贡献和在DEF和FAU整个瘤胃食糜（WRD）和其液体（LIQ）和固体（SOL）的级分还原速率，单独孵育（CON），其中添加的或加上的。体内实验的结果显示总VFA浓度没有差异，尽管 FAU绵羊的瘤胃NH ₃更大（p <.01）。 饲喂FAU后1.5小时，相对于DEF绵羊，瘤胃和血浆浓度趋于增加（p <.10）。体外结果显示，还原为NH ₃受到促进（ 通过输入相对于CON摘要的DEF和FAU来得出p <.01）。但是，相对于FAU消化液的两个馏分，添加DEF的SOL馏分的累积 速率均增加（p <.05）。在体内和体外观察到的结果表明，与在瘤胃原虫存在下更迅速代谢。由于瘤胃中的堆积，腐烂的绵羊中毒的风险可能会增加。