Small Volume of Inoculum with an Artificial Rumen Fluid for In Vitro Digestion of Forage

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Abstract
Evaluation of artificial rumen fluid for in vitro disappearance of dry matter of forage was made with 1 or 10 ml of rumen fluid inoculum. An interaction occurred between laboratory procedure and amount of inoculum. In vitro disappearance of dry matter was much lower with 1 ml of inoculum rather than 10 ml with McDougal''s artificial saliva. In vitro disappearance of dry matter was lower with 10 ml inoculum compared to 1 ml inoculum used with artificial rumen fluid. Eight different forages [wheat straw, milo stalks, corn stalks, corn silage, sorghum silage, alfalfa hay, oat silage and trudan soilage] and 2 inoculum sources [milo stalk and alfalfa hay] were used to compare artificial rumen fluid with 1 ml inoculum and McDougal''s artificial saliva with 10 ml inoculum. Mean in vitro disappearance of dry matter of forages varied from 35.9% for the wheat straw to 74.1% for trudan soilage. This mean tended to be higher when rumen fluid inoculum was obtained from a steer receiving a milo stalk ration (60.2%) than from a steer receiving alfalfa hay (57.8%). There was no interaction between sources of inoculum and laboratory methods. There was no significant difference between artificial rumen fluid and the standard procedure with any forage substrate. Artificial rumen fluid with 1 ml of rumen fluid inoculum should provide an alternative method for in vitro evaluation of forage.