Some Factors Influencing the Rumen Microbial Population

Abstract

SUMMARYIn sheep fed once daily, the concentrations of micro-organisms in the rumen changed with the time after feeding, some organisms fluctuating in numbers more than others; peak concentrations were reached at different times for different organisms. These changes in concentration were reilected in changes in the proportion of dividing cells, for example, in Dasytricha rumiimatiurn this proportion varied from less than 0.2 yo throughout most of the day to a maximum of 23% a few hours before feeding; for Entodiniurn spp. the variation was less: it was possible to calculate the minimum doubling time for these latter organisms as about 5 hr.One animal a t dif'fercnt times, or different animals, on the same ration and dietary regime had very dil'ferent rumen microbial populations, these differences being particularly marked in the case of some organisms. Reasons why these marked differences in microbial population are not reflected in similarly marked differences in over-all rumen metabolism are discussed.Feeding different quantities of the same ration had little effect on the concentration of rumen microbes, provided the ration was above a minimal level; it is, however, suggested that output of microbial cells from the rumen may have varied with the amount of feed given. Starvation for a few days or prolonged under-nutrition had a marked effect, some organisms being drastically reduced in numbers or dying out completely. When the qualitative nature of the diet was changed, about 10 days were needed a ion. to complete the major adjustments in the rumen microbial popul t'

Diurnal Changes in the Concentrations of Micro-organisms in the Rumens of Sheep Fed Limited Diets Once Daily: WITH AN APPENDIX ON THE KINETICS OF RUMEN MICROBES AND FLOW

“…above, it can be seen that v = In 2/g = In (1 + I ) / T = I / T approximately for small values of I . In the work reported here, the observer who estimated the proportion of dividing cells used different criteria from those used in the studies of Warner (19623) and it is believed that I' = 0.751, where I' is the proportion of cells recognizable as dividing in the living preparations used to determine the time to complete division T , and I is the proportion of cells recognizable as dividing in fixed preparations, as recorded in this paper. For entodinia, therefore, v = I'/T = 31…”

“…However, this was not the case, and it would appear that the length of the trichomes reflected their nutritional rather than their reproductive status. Previous work (Warner, 19623) indicated that much, but not all, of the variation in concentration of oscillospirae, as measured by the standard count, disappeared when the total count was used, suggesting that sequestration and return accounted for some part of the changes in concentration. This might account for the fact that the initial rate of decline in concentration exceeded the dilution rate.…”

Digestion of a dehydrated lucerne/barley diet (70:30) in defaunated, Isotricha-monoinoculated and mixed-fauna-inoculated rumen in sheep

“…To calculate the volume of ciliates in the rumen, the mean volumes of large (Eudiplodinium, Isotricha), medium (Epidinium, some Entodinia) and small ciliates (small Entodinia) were taken to be 10 6 , 10 5 and 10 4 pm 3 respectively (Warner, 1962;Williams and Coleman, 1992). The corresponding biomass was calculated from the estimations of Leng et al (1981) and Broad and Dawson (1975) Van Soest and Wine (1967).…”

Effect of ruminal inoculation of Isotricha alone or a mixed B-type fauna in a defaunated rumen on the digestion of a hay-maize diet (70:30) in sheep

“…Samples of rumen fluid (5 ml) containing 5% (w/v) solution of orthophosphoric acid were kept at -15°C. Two milliliters of rumen fluid were mixed with 8 ml of a 12.5% (w/v) (Warner, 1962 (Leng et al, 1981) and that the mean content of N in their DM was close to 6.0% (Jouany and Thivend, 1972). We also assumed that the volume, and therefore the weight, of small entodinia was 100 times less that of the large ciliates.…”