The meta-analysis confirmed possible nitrate poisoning triggered by higher blood methemoglobin levels with increasing nitrate consumption of ruminants: methemoglobin (%) 41.3 nitrate [g kg 1 body weight (BW) d 1] 1.2; R2 0.76, PB0.001. However, acclimatizing animals to nitrate reduced the toxicity of nitrate: methemoglobin (%) 4.2 nitrate (g kg 1 BW d 1) 0.4, R2 0.76, P 0.002. Animals fed nitrate reduced enteric methane emissions in a doseresponse manner: methane [g kg 1 dry matter intake (DMI)] 8.3 nitrate (g kg 1BWd 1) 15.2,R2 0.80, PB0.001. The reduction of enteric methane emissions due to supplementary nitrate was effective and consistent in both in vitro and in vivo studies and also persistent in several long-term studies.