Rumen Ecology and its complications.pptx

In this ppt Rumen Ecology is discussed.

1. MICROBIOLOGY OF THE RUMEN Microorganisms are found throughout the gut, from mouth to the anus. Wherever suitable conditions and substrates occurs. They may be found attached to the epithelial surface, deep in the crypts in the mucosa, or free in the gut lumen. The rumen provides an environment which is very favourable for microbial growth. The pH of rumen is normally between 5.5 and 7.0 and the temperature is about 39oC which is near optimum for many microbial enzyme systems. Substrates is provided in a continuous manner. Contraction of the stomach helps to bring the microorganisms into contact with freshly ingested or ruminated feed and the fluid conditions are ideal for many microorganisms . Rumen microorganisms consists of bacteria, ciliated protozoa, fungi, and bacteriophages (viruses).

2. Rumen Bacteria Rumen bacteria are small cocci and rods like structures. Most classification schemes of rumen bacteria are based on the type of substrates used as primary source of energy.

3. A. Cellulolytic Bacteria ( Cellulose fermenting) Widely found in nature. Cellulose constitutes perhaps 70% of all organic carbon in the biosphere. These bacteria produce cellulase, an enzymes which hydrolyse β 1-4 glycosidic bonds of cellulose, and of the dimer cellobiose. As we know that no animal produces it own cellulase . Thus any animal which digests cellulose must rely upon bacteria somewhere in its gut to hydrolyse the β 1-4 bonds between the glucose residues. Cellulolytic bacteria are found in the highest concentration in the rumen of animals consuming fibrous diets. Important cellulolytic species include: Bacteroides succinogenes, Ruminococcus flavefaciens, Ruminococcus albus and Cillobacterium cellulosolvens.

4. B. Hemicellulose Fermenting Bacteria Hemicellulose differs from cellulose in containing pentose as well as hexose sugars and usually uronic acids. Hemicellulose is an important structural polysaccharide in plant cell walls and organism capable of hydrolyzing cellulose are usually able to utilize hemicellulose. Some species which ferment hemicellulose are: Butyrivibrio fibriosolvens and Bacteroides ruminicola.

5. C. Amylolytic (starch fermenting) bacteria. A number of cellulolytic organisms can also ferment starch, however, amylolytic species cannot ferment cellulose. Amylolytic species are found in greatest numbers when the animal is eating a diet high in starch such as grains. Important amylolytic bacteria include: Bacteroides amylophilus, Butyrivibrio fibriosolvens, Bacteroides ruminicola and streptococcus bovis.

6. D. Sugar Fermenter Bacteria Most of the bacteria which utilize polysaccharides are also capable of utilizing disaccharides and monosaccharides. Young plant material contains considerably readily fermentable carbohydrates which are rapidly fermented as soon as ingested feed enters the reticulo-rumen. This is one disadvantage of the ruminant system. It would be more efficient for the sugars to be digested and absorbed directly by the host animal in the small intestine. However, it is a small price to pay for the advantage of being able to utilize polysaccharides as an energy source, for which the host is dependent on the rumen microbiota.

7. E. Acid Utilizers Bacteria. A number of rumen microorganisms utilize lactic acid, although it is not normally present in appreciable amount. Others utilize succinic, malic or fumaric acids produced as end products by other bacterial species. Formic acid and acetic acid are also used by some species, although probably not as a primary energy source. Oxalic acid, which is toxic to mammals, is also decomposed by rumen microorganisms. This function of the rumen microbiota enables ruminants to exploit plant materials which would otherwise be poisonous and therefore not utilize. Some bacterial species which utilize lactic acid, which may occur in high concentration if the animal has sudden access to grains or other high-starch food. Some species of acid utilizers bacteria include: Peptostreptococcus elsdenii, Propioni bacterium and Selenomonas lactilytica.

8. F. Proteolytic Bacteria These are the most widespread of bacteria in the gut of mammals, including carnivores. In the rumen several species are known to utilize amino acids as a primary energy source. These includes: Bacteroides amylophilus, Clostridium sporogenes and Bacillus licheniformis.

9. G. Methanogenic Bacteria About 25% of the gas produces in the rumen is methane. Methane producing bacteria are slow-growing. Methanogenic bacteria species includes: Methanobacterium ruminantium and Methanobacterium formicicum .

10. H. Lipolytic Bacteria Some rumen bacterial species utilize glycerol, and only a few sugars. Others hydrogenate unsaturated fatty acids and some apparently metabolize long-chain fatty acids to ketones.

11. I. Ureolytic Bacteria A large numbers of rumen bacterial species exhibit Ureolytic activity, hydrolyzing urea to CO2 and ammonia. Many of these species are found attached to the rumen epithelium and hydrolyse urea diffusing from the blood into the rumen across the rumen wall. Thus, the concentration of urea in ruminal fluid is always very low. The usual range of bacterial numbers in the rumen is 15 to 80 × 109 per ml contents. However, numbers may be as low as 4 × 109 per ml in animals fed on wheat straw and as high as 88 × 109 per ml in sheep on good pasture.