The rumen ammonia level (AL) is the key intermediate in the microbial degradation and synthesis of protein. Measurement of ruminal AL reflects the balance achieved between protein breakdown and synthesis under special dietary circumstances. If the diet is protein deficient or its protein resists degradation, the rumen AL will be low and the rumen microbial growth will be slow. Conversely, if protein degradation is faster than synthesis, rumen AL will accumulate in excess of its optimum level. Excess AL is absorbed into the blood, and converted into urea via liver. Major part of urea is excreted in the urine as a waste causing pollution to the environment. This study examined the effect of various spices when incubated with different forages in rumen fluid (RF) in vitro for different times on AL.