It was found that supplementation with RPM and/or
PO to dairy cows diets did not show negative effect on ruminal pH, blood urea nitrogen and milk urea nitrogen
concentration (p > 0.05). However, supplementation with RPM resulted in lower ammonia nitrogen (NH3-N)
concentration (p < 0.05). In addition, propionic acid and milk production increased while acetic acid, acetic to
propionic ratio, methane production, methanogens and protozoal population decreased with RPM and/or PO
supplementation.