The micro-organisms in rumen samples from Red deer, hill sheep and reindeer grazing their natural pastures in the Scottish Highlands were examined at different seasons over a number of years. The total counts of bacteria and protozoa varied with the season, and were lowest in winter when fermentative activity was also at its lowest.
As is usual in roughage-fed ruminants, viable counts were only a very small proportion of the total counts. The reindeer rumens had the highest concentrations of bacteria.
There were no consistent differences in the types of bacteria between seasons, but although there were no bacteria peculiar to any animal species the balance of predominant types varied between the species. The principal types of bacteria were similar to those found in domesticated ruminants. The numbers of protozoa in the Red deer were higher than those in the sheep, and the concentrations in reindeer were higher than those generally reported for domesticated cattle or sheep. A number of species of protozoa were found in each animal and the predominant species differed in the different animals.