VPB 121: Veterinary Physiology - II (2+1)

AMMONIA NITROGEN IN THE RUMEN FLUID

• Ammonia is an important source of N for the growth of rumen microorganisms.  About 92% of rumen bacteria utilize ammonia as a nitrogen source.
• Ammonia nitrogen in the rumen fluid varies with diet( 2mg to 100 mg/ dl) ( normal range is 5-25mg/dl)
• High concentration of starch diet tends to reduce rumen ammonia.
• Urea, frequently used to replace true protein in ruminant ration as a non-protein source is rapidly cleaved in rumen by ureolytic bacteria to ammonia.
• Ammonia toxicity is most frequent sequelae of urea feeding where rumen pH may rise to 7.3. But urea toxicity is tolerable if pH is maintained within 7.0.
• The route by which NH3 utilized depends upon the concentration of NH3 in the rumen fluid. When the NH3 concentration is low, the energy dependent GS/GOGAT systems is utilized whereas when the concentration  is high, GDH system is utilized. This is the pathway by which NH3 is converted to microbial protein. When NH3 present in the form of ammonium ion and it requires active transport.
• Glutamine occupies a central role in the nitrogen metabolism of rumen bacteria. As there is no functional TCA cycle (Ketoglutarate is not formed) it is synthesised by reverse TCA cycle.