In addition to the bacteria in the rumen there are many larger (5–250/mm long) organisms which at various times have been designated protozoa Of these the ‘ovals’ (Quin’s and Eadie’s) are now known to be large bacteria (Orpin, 1976) and the ‘flagellates’ Neocallimastix frontalis, Piromonas communis and Sphaeromonas communis are the zoospores of phycomycete fungi (Orpin, 1977a, b) There are genuine flagellates in the rumen, eg Trichomonas spp, Monoceromonas sp and Chilomastix sp, but almost nothing is known about their metabolism (Jensen and Hammon, 1964) The largest, most obvious and most important protozoa are the ciliates, of which there are two groups both in the subclass Trichostomatia The so called ‘holotrich’ protozoa belong to the order Vestibuliferida and the entodiniomorphs to the order Entodiniomorphida, suborder Entodiniomorphina and family Ophryoscolecidae As the properties and metabolism of these two protozoal groups are different, they will be considered separately below

The Rumen Protozoa

Publisher Summary Rumen protozoa were first observed in rumen metabolism. These ciliate protozoa are present in all wild and domesticated ruminants and are of two types: the entodiniomorphid protozoa characterized by the presence of a firm pellicle and the possession of cilia on the peristome and the holotrich protozoa, which are completely covered with cilia. Rumen ciliate protozoa are acquired by young ruminants directly from adult animals or by eating food contaminated with saliva from such animals. Lambs or calves reared in the absence of adult animals have no ciliate protozoa although they acquire a normal bacterial flora. The chapter outlines the role of the protozoa in ruminant growth, metabolism, and disease, followed by descriptions of physiology and biochemistry of individual species. General findings are correlated to show the role played by protozoa in normal ruminants.

Rumen ciliate protozoa.

This review describes the progress which has been made during the last 10 to 15 years in the field of rumen microbiology. It is basically an account of new discoveries in the bacteriology, protozoology, biochemistry, and ecology of the rumen microbial population. As such it covers a wide range of subjects including the isolation and properties of methanogenic bacteria, the role of rumen phycomycete fungi, anaerobic energy conservation, and general metabolic aspects of rumen microorganisms. It also attempts, however, to describe and develop new concepts in rumen microbiology. These consist principally of interactions of the microbemicrobe, microbe-food and microbe-host types, and represent the main areas of recent advance in our understanding of the rumen ecosystem. The development of experimental techniques such as chemostat culture and scanning electron microscopy are shown to have been instrumental in progress in these areas. The paper is concluded with an assessment of our present knowledge of the rumen fermentation, based on the degree of success of experiments with gnotobiotic ruminants inoculated with defined flora and in mathematical modeling of the fermentation. The efficacy of chemical manipulation of the fermentation in ruminant is also discussed in this light.

Microbial ecology and activities in the rumen: part 1.

Adaptation in the metabolism of the animal, in the microbial metabolism in the rumen or by feeding techniques should be understood to involve adjustments in the natural regulation systems preventing digestive and metabolic disorders when changes are made in type and composition of rations. Disorders that may occur include chronic latent rumen acidosis with consequences such as parakeratosis ruminis, ruminitis chronica hyperplastica, ruminitis liver abscess complex, laminitis chronica, subclinical ketosis and eventually a cerebro-cortical necrosis as well as, finally, acute rumen acidosis which can be followed by acute ruminitis or acute laminitis9,10. The main factors involved in adaptation are dietary composition and level of feeding. Both of them can be discussed separately.

Adaptation to changes in dietary composition, level and frequency of feeding

Nitrogen and phosphorus nutrition of cattle: reducing the environmental impact of cattle operations.

Entodinium longinucleatum grown in vitro in the presence of bacteria engulfed a wide range of bacterial species at rates of 130–3400 bacteria/h/protozoon (from suspensions of 10 bacteria/ml), but showed a preference for Klebsiella aerogenes and Proteus mirabilis which occurred in the growth medium. Some of the bacteria were digested with release of soluble material into the medium. Free amino acids were incorporated by the protozoa in the presence of chloramphenicol at rates of 5·4–15·1 nmol/h/106 protozoa and approximately 40% of the amino acid-carbon was incorporated into protein. There was no appreciable synthesis of protozoal protein from carbohydrate. Evidence was obtained that the protozoa obtained the amino acids required for growth largely from engulfed bacteria.

The Uptake and Utilization of Bacteria, Amino Acids and Carbohydrate by the Rumen Ciliate Entodinium longinucleatum in Relation to the Sources of Amino Acids for Protein Synthesis

G. S. Coleman

Papers

The Uptake and Utilization of Bacteria, Amino Acids and Carbohydrate by the Rumen Ciliate Entodinium longinucleatum in Relation to the Sources of Amino Acids for Protein Synthesis