Studies on rumen fermentation

I. Influences of grazing and hay feeding on rumen fermentation and viable counts of rumen microorganisms

Abstract

The rumen fermentation and viable counts of microorganisms of the rumen were compared between goats grazed on native fresh grass and those fed hay prepared from native grass. The results and findings obtained are as follows.
The viable counts of anaerobes appearing on glucose media were 2.0-9.3×1010 and 8.2×107-7.5×108 per ml of rumen contents of the grazed animal on September 23 and November 3, respectively. Then they were reduced to 2.5-7.5×107 on January 23 during hay feeding. The viable counts of aerobes on glucose media at the same dates were 1.6-7.7×109 (Sept. 23), 10-6.O×107 (Nov. 3), and 2.5×106-3.5×107 (Jan. 23). The conuts of microorganisms, regardless of anaerobes and aerobes, on glucose media showed some decrease at the final stage of grazing and the stage of hay feeding.
Changes in viable counts of certain microorganisms occurred after the feed intake. The number of anaerobes on glucose medium decreased 3 hours after feeding, but that of certain anaeroles grown on cellobiose-, succinate-, and lactate-media increased conversely. On the other hand, the number of aerobes on glucose medium increased after feed intake, while organisms on cellobiose-, succinate-, and lactate-media decreased in number.
The level of volatile fatty acids in the rumen fluid of a goat was higher during grazing than during hay feeding. Moreover, in the rumen fluid, large amounts of propionic and butyric acids were produced during grazing, but acetic acid was predominant during hay feeding.
The pH values of the rumen fluids were 6.4-7.1, showing no difference between grazing and hay feeding.
The Eh values of the rumen contents seemed to be lower during grazing than during hay feeding.