Av. Klieve et al., RUMEN BACTERIAL AND PROTOZOAL POPULATIONS IN CATTLE BEING RELOCATED IN TROPICAL QUEENSLAND, Australian Journal of Agricultural Research, 49(7), 1998, pp. 1153-1159
Rumen microbial populations were measured in Brahman-cross steers that
were relocated from spear grass (Heteropogon contortus) dominant past
ures in northern Queensland to buffel grass (Cenchrus ciliasis) domina
nt pastures in central Queensland, to assess whether aspects of rumen
function may contribute to the sometimes reported depressed growth rat
es following relocation. Nine genera of ciliate protozoa (Isotricha, D
asytricha, Entodinia, Epidinium, Diplodinium, Ostracodinium, Metadiniu
m, Elytroplastron, and Eudiplodinium) were recorded in the rumen fluid
of the steers. In most steers all genera were present at any time and
the generic mix persisted throughout the 10 months over which the stu
dy was conducted. Protozoal population composition fluctuated only sli
ghtly over the sampling period. Entodinia were predominant, occupying
50-70% of the population. Population density varied according to seaso
n, with the highest density (4-8x10(5)/mL rumen fluid) occurring in th
e wet season. Bacterial and protozoal populations were remarkably stab
le and little affected by relocation. Again, the major impact on popul
ation density was the season, with all carbohydrate (soluble sugar, st
arch, xylan, and cellulose) utilising bacterial subpopulations reachin
g the greatest density with the onset of the wet season.