SUMMARYThe development of the rumen flora and fauna has been followed by microscopic observations of rumen fluid from 58 young lambs and calves kept under different conditions of management ; including remaining with the dam, early weaning and artificial inoculation into the rumen. Ciliatefree animals were successfully maintained by isolation from direct contact with other ruminants from an early age, but it was noted that greater space should be left between cattle than between sheep. The general effect of different diets and treatments proved similar in calves and lambs but certain differences were noted in their flora. Certain large bacteria developed in isolated lambs without direct contact between animals. Some generalizations, particularly the effect of a high concentrate diet, were applicable to all animals examined, but there were variations between individual animals. In the establishment of rumen ciliates diet was the governing factor and artificial inoculation with ciliates proved as effective as constant contact with the dam. Although the ciliate-free animals showed no differences in performance certain differences in the rumen flora common to isolated calves and lambs were noted.

SUMMARYThe establishment and components of the rumen ciliate population in a series of young animals has been followed using intra-ruminal inoculation with rumen material, and for comparison purposes the ciliate population in a number of adult ruminants has been examined. The fact that the ciliates Polyplastron multivesiculatum, Eudiplodinium maggii and Epidinium spp., though not host specific, did not form a stable mixed population was noted and experiments were carried out to examine the antogonism between certain of these organisms. The cause of the antagonism was not determined but cannibalism, food competition, or gross bacterial change did not seem to be responsible. It was found that the population of an adult animal could be changed by inoculation but the relationship between the ciliates appeared to be in some way affected by the host. It is concluded that inter-relationships of the type described may play an important role in determining the components of a particular rumen microfauna.

1. Twelve steers fitted with rumen cannulas were used in three separate experiments to investigate the effects of the presence or absence of rumen ciliate protozoa on methane production. The diet consisted of 850 g barley and 150 g protein supplement/kg, and was given in three feeds daily at a restricted level of 61 g/kg live eight^''^. Animals were defaunated initially by allowing ad lib. consumption of this diet and were then maintained ciliate-free by isolation or were faunated by inoculation with a mixed ciliate suspension. Samples of rumen fluid were taken routinely for the assessment of microbial populations and for volatile fatty acid (VFA) analysis and energy and nitrogen balances and digestibility measurements were made at intervals while animals were confined in respiration chambers.2. In each experiment the rumen VFA proportions changed from a high-propionate pattern under ciliate-free conditions to a low-propionate, high-butyrate pattern in the presence of ciliates: differences between treatments were highly significant (P < 0.001). There were also marked differences between treatments in CH, production but a reliable comparison was possible only in Expt 3, in which CH, was significantly higher (P < 0.001) in the presence of a rumen ciliate population. In Expt 3 the increased loss of energy as CH, in the faunated animals amounted to 4 4 MJ/100 MJ energy intake.3. Stoichiometric estimates of CH, production derived from the observed VFA proportions showed good agreement with CH, production as measured in respiration chambers. On average, the stoichiometric CH, values overestimated CH, production by a factor of 1.08. 4.Highly significant linear relationships (P < 0.001) were observed between the molar proportion of each major VFA and the quantity of CH, produced: the proportion of propionic acid was inversely related to CH, and showed the lowest residual standard deviation of all the relationships examined.5. The losses of energy in faeces and urine did not differ between treatments hence the increased loss of energy as CH, in the faunated animals resulted in a significant reduction in the metabolizability of the diet from 0.73 to 0.69 (P < 0.05). No significant differences were detected between treatments in heat production, apparent digestibility coefficients or N balance.6. It is suggested that the rumen ciliates, by modifying the rumen VFA proportions, are directly responsible for the increased CH, production in faunated animals.Previous work in this laboratory has shown that rumen ciliate protozoa are normally absent from cattle given ad lib. access to an all-concentrate diet but can be established in large numbers when the same diet is given in amounts below appetite (Eadie et al. 1970). When intake is restricted and the daily allowance is offered in three equal meals the presence of ciliates gives rise to marked changes in the pattern of rumen fermentation. In particular, rumen pH is higher and the volatile fatty acids (VFA) in rumen fluid show a lower proportion of propionic acid and a much high...

In previous work the rumen microbiology of young animals fed on a high carbohydrate ration has been considered and has tended to be fairly consistent (Eadie, Hobson and Mann, 1959; Eadie, 1962). In this note a further controlled experiment on calves weaned on to a 50:50 mixture of roughage/high concentrate mixture and on to the high concentrate alone, is reported. In view of interest in the intensive feeding of cattle on barley these results from young animals are compared with a series of observations made more recently on older animals fed predominantly on barley, since it was obvious from the outset that the physical nature of the rumen contents was different in the two age groups. The sudden introduction of large amounts of carbohydrate into the diet of animals previously fed conventionally has been shown to create profound changes in the rumen microbial population (Krogh, 1961) and the microbiology of the young concentrate-fed calf was very different from the roughage-fed animal. However, the barley-fed steers used in this work had been early weaned on to a high concentrate ration and had clearly become adapted to the adult high carbohydrate diet.

I. Three heifers were changed from a diet of equal parts of hay and barley cubes (50:~o diet) to one entirely of barley cubes given in three equal feeds throughout the day. Feed intake was restricted to 80 % of calculated appetite at the time of change and this percentage progressively decreased as the live weights of the animals increased.2. The change of diet had no significant effect on the volume of rumen fluid but the rate of outflow from the rumen was significantly lower on the barley diet than on the 50: 50 diet.3. Animals on the restricted barley diet developed an exceptionally high rumen ciliate population and the bacterial population was shown by Gram films to include a number of organisms typical of roughage-fed animals. In culture, organisms of the genus Bacteroides were predominant but these appeared largely as cocco-bacilli in the Gram films. This microbial population was associated with a higher proportion of butyric acid than of propionic acid in the rumen fluid.4. Occasional fluctuations in ciliate populations occurred in all three heifers. Decreases in ciliate number were paralleled by increases in propionic acid and decreases in butyric acid but not necessarily by a fall in pH. Under these conditions Gram films showed increases in bacteriodes-type rods and in certain curved Gram-negative rods.5. Rumen ammonia concentrations were on average lower and showed a different diurnal pattern when ciliate numbers were reduced. Lactic acid concentrations were low and were not affected by the size of the ciliate population.6. When the three heifers were given the barley diet ad lib. there was a decrease in rumen pH and a complete loss of rumen ciliates. The rumen bacterial population and the volatile fatty acid proportions were similar to those seen during decreases in ciliate number at the restricted level of intake. These changes also occurred in a fourth heifer which was changed fairly rapidly from the 50: 50 diet to a restricted amount of the barley diet. 7.Two steers which had never had access to roughage were changed from ad lib. to restricted intake of the barley diet and were later given an inoculum of rumen ciliates. The rumen microbial population and the pattern of fermentation so produced were similar to those found in the heifers on the restricted barley diet.8. Anomalous values were noted for total counts of rumen bacteria when free starch grains were present in the rumen fluid.9. It is concluded that large ciliate populations and high proportions of butyric acid can be produced in animals fed exclusively on a barley diet by suitable adjustment of the intake and the method of feeding. I t is postulated that the ciliate population may be largely responsible for the high butyric acid concentrations.The rumen microbial populations of mature steers given ad lib. access to a barley diet have been described by Eadie, Hobson & Mann (1967) and have been shown to be similar in many respects to those found in young ruminating calves given large amounts of starchy concentrates (Eadie, 1962). A complete...