Physico chemical tests

VARIOUS TEST

Hydrogen ion concentration (Ph)

  • pH should be measured immediately after collection without much exposure to atmospheric air. It can be measured by indicator paper in field conditions.
  • Significance
    • Physiological variation - 5.5-7.0.
    • Ration rich in crude fibre and/or - Higher range (6.0-6.8.)
    • protein
    • Ration rich in starch or sugar - Lower range (5.5-6.0)
    • After starvation for 24 hours or more - Upto 8.5
    • Urea poisoning Rumen decomposition
    • Hydrochloric acidosis - 4.3-7.0 (average 6.3)
    • Rumen acidosis - 4.0-5.5 Even may reach less than 4.00 in acute cases.

Cellulose Digestion Test (CDT)

  • Take 10 ml of strained rumen fluid and add 0.3 ml of 16% glucose solution in a capped test tube. Suspend a thread of pure cellulose (free from any synthetic fibre) or single strand of unmercerized cotton thread in the rumen fluid. The lower end of the cotton thread is tied with a glass bead or other weight which must immerse in rumen fluid. Then tightly close the test tube and incubate at body temperature  (39º C) either in incubator or near a light bulb.
  • Significance
    • Normally digestion of cellulose takes place within 48-54 hrs. So, in fully active rumen fluid the weight in the lower end of cotton thread will fall to the bottom of the tube within that time due to digestion of cotton thread. If the thread has not broken within the normal time. It should be interpreted as cellulose digestion time is being delayed due to inactive rumen fluid.

Glucose Fermentation Test

  • It is performed in a fermentation saccharometer. Take 10 ml of rumen fluid and add 0.5 ml of 16% glucose solution in the saccharometer and keep at 39º C. The result is read after 30-60 minutes.
  • Significance
    • Normal rumen fluid containing active microflora will ferment the glucose and result in formation of gas.
    • 1-2 ml gas/hr - Rumen fluid containing active microflora.
    • No gas - Rumen fluid containing inactive microflora and acute rumen acidosis.
    • Decreased gas - Rumen decomposition, rumen alkalosis, acute rumen acidosis, Hydrochloric acidosis.
    • Normal/increased gas - Latent rumen acidosis
    • Increased gas - Foamy bloat

Redox potential or Methylene Blue Reduction Time (MBRT TEST)

  • This is measured y using a redox dye, methylene blue. Take 20 ml of freshly collected rumen fluid and add 1 ml of 0.03% methylene blue solution and mix. Measure the time required for decolouration of the sample using a plain rumen fluid as a basis for comparison.
  • Significance
    • It is one of the most reliable tests to assess the microbial status of rumen fluid.
    • In normally active microflora - Methylene blue reduced within 3 minutes.
    • Only straw ration - 3-6 minutes
    • Inactive flora due to ration poor - More than 15 minutes in structure, Inappetence
    • Rumen acidosis - More than 5 minutes

Nitrite Reduction

  • 10 ml of strained rumen fluid is placed into each of 3 test tubes and 0.2 (Tube 1). 0.5 (tube 2) or 0.7 (tube 3) ml of 0.025% Potassium nitrite solution is added and kept in water bath at 39º C. Every 5 minutes 1 drop from each tube is placed in the small wells of a ceramic plate and to each drop is added 2 drops each of reagent 1 (2 ml of sufanilic acid in 30% acetic acid to make 200 ml), and reagent II (0.6 ml alpha-naphthylamine, 16 ml concentrate acetic acid, 140 ml distilled water). Until disappearance of red colour which will provide information on the activity of microbes that degrade and synthesize nitrogenous compounds. The presence of red colour indicates that still nitrite is present.
  • Significance
    • Rumen fluid from cattle fed with - Nitrite should disappear in
    • Mixed ration 5-10 minutes – tube 1
    • 20 minutes – tube 2
    • 30 minutes – tube 3
    • Rumen alkalosis, Green fodder, - Rapid reduction in all tubes
    • Ruminal decomposition, Bloat
    • Lack of appetite, deficient ration, - Slow reduction in all tubes
    • Hydrochloric acidosis
    • Acute lactacidosis - No notable reduction even after 45 minutes.

Volatile Fatty Acids (V.F.A.)

  • For every 20 ml of rumen fluid, 1 ml of saturated mercuric chloride solution is added and sent to the laboratory for determining total and individual fatty acids.
  • Significance
    • Normal 
      • Total V.F.A. concentration - 60-120 mol/litre of rumen fluid
      • Propionic acid - 20-25 mol%
      • Acetic acid - 50-65 mol%
      • Butyric acid - 10-20 mol%
      • Formic, valeric, caproic and high fatty acids - 5 mol%
      • V.F.A concentration increased on concentrate ration and also 3-5 hours after feeding.
      • V.F.A. concentration decreased on completion of fermentation (pH increased).
    • Abnormal
      • Loss of appetite, Ration poor in structure, - Total V.F.A. decreased
      • Digestive disorders
      • Increasing amounts of easily digestible - Proportion of individual acids change
      • Carbohydrate

Chloride

  • To 0.1 ml of the chloride standard solution, add deionized water 1 ml and put 0.2 ml indicator. Then titrate the standard with mercuric nitrate solution. The end point is slight, but permanent violet colour. This will be the standard. Repeat the same with rumen liquor sample.
  • Calculation

(Test reading / Standard reading ) x 100 = m eq.

 

  • This is useful in distinguishing hydrochloric acidosis from lactic acidosis.
  • Normal level of chloride content in rumen fluid:- 15-25 mVal/litre.
  • Abnormal
    • Lactacidosis - Less than 40 mVal/litre.
    • Hydrochloric acidosis - More than 25-30 mVal/litre.
    • May increase to 30-100 mVal/litre in
      • reflux of abomasal content as a result of obstruction
      • supplementation of ration with sodium chloride
      • functional or anatomical pyloric stenosis
      • abomasitis
      • abomasal ulcer
      • sand in stomach or intestine
      • abomasal displacement
      • cellulitis of mesentery at its attachment to the abomasum
      • paralytic ileus

Total acidity (Titratable acidity)

  • One or 2 drops of phenolphthalein are added to 10 ml of rumen fluid and the mixture is titrated with N/10 NaOH until it becomes flesh coloured. The volume of NaOH required (in ml) multiplied by 10 gives clinical units of total acidity:
  • Normal rumen fluid - 8-25 clinical units
  • Significance
    • In hyperacidity (lactic acidosis or hydrochloric acidosis) - upto 70 units
    • Lactacidosis - significantly increased.
    • Hydrochloric acidosis - moderately increased.
Last modified: Friday, 23 September 2011, 7:24 AM