CHAPTER: 10
Rumen Microbiology
Ø Introduction to Rumen Microbiology
Ø Role of Microbes in Silage
Production
…………………………………………………….
Introduction to
Rumen Microbiology:
Rumen
Microbiology:
• The
study of microorganisms & its symbiotic relationship in the forestomach
(rumen) of herbivores to exploit fibrous feeds as a source of energy &
nutrients is known as Rumen Microbiology.
Importance
of rumen microbes:
• Increasing
the production of microbes in the rumen is the key to lifting milk production
and composition.
• The
microbes break down feed to produce volatile fatty acids, which are used by the
cow as energy for maintenance and milk production.
• The rumen microbes are also digested and
absorbed in the small intestine of the dairy cow as the main protein source for
milk production—providing up to 70–90% of a cow’s protein requirements.
Roles of Rumen
Microorganisms:
Rumen
Bacteria:
• Use
cellulose, hemi-cellulose, starch, sugars, intermediate acids, proteins, &
lipids.
• They
regulate overall fermentation by reducing carbon dioxide with Hydrogen gas to
form Methane.
Protozoa:
• Ingest
bacteria for their protein source.
• Control
bacteria no. in the rumen.
Rumen
Fungi:
• Degrade
cellulose and xylan.
• Aid
in the fiber digestion
Some
Important Species of Rumen Bacteria:
• Fibrobacter succinogenes is
the predominant cellulolytic Gram-negative bacterial
species in the rumen. It ferments glucose and produces acetate and succinate as
waste products.
• Ruminococcus flavifaciens is
a Gram-positive, cellulolytic bacterium. It is the most active species
involved in the digestion of plant cell walls due to its high cellulase and
hemicellulase activity. It produces hydrogen, acetate and succinate as end
products.
• Megasphaera elsdenii is
a Gram-negative coccus and is the predominant bacterial species in
the rumen of young ruminants. It is important because it ferments glucose to
propionate which is then available to the host for gluconeogenesis.
• Selenomonas ruminantium is
a non-cellulolytic Gram-negative species which ferments glucose and
occurs in large numbers when ruminants are fed grain. This species is an
important producer of propionate which is used by the host ruminant for
gluconeogenesis.
• Veillonella parvula is
a Gram-negative bacterium
that uses lactate as a growth substrate, from which it makes acetate and
propionate.
• Butyrivibrio fibrisolvens are Gram-negative cellulolytic
bacteria, common in the rumen, producing acetate and butyrate by fermentation
of glucose and other substrates.
• Lactobacillus
ruminis is
predominant in the reticulo-rumen of young animals. It is an important glucose
fermenter and produces mainly lactate.
• Streptococcus
bovis is another important glucose fermenter
also producing mainly lactate.
• Methanobacterium
ruminantium and Methanosarcina barkeri are
important rumen methanogens.
Protozoa:
• The
protozoa are actually predators to the bacteria in the rumen --- they eat the
bacteria for dinner
• The
rumen protozoa produce fermentation end-products similar those made by the
bacteria, particularly acetate, butyrate, and hydrogen.
• Specific
examples of common protozoa include Ophryoscolex monoacanthus, Entodinium
exiguum, Eudiplodinium maggii, and Isotricha
intestinalis.
Rumen
Fungi:
• help
out the fiber-digesting bacteria by doing some of the initial work of splitting
fibrous material apart and making it more accessible for the bacteria.
• Species
of Piromyces, Neocallimastix, Orpinomyces and Anaeromyces degrade fibre to
a substantial degree.
Role of Microbes
in Silage Production:
• Silage
is preserved fodder, made from green plants.
• Silage
is prepared with maize, sorghum, peas and alfalfa plants.
• During
the process of preservation, certain fermentation process takes place due to
microbial activity.
• In
the preparation of silage, plants are harvested before they are fully mature,
and are cut into small bits.
• Then,
it is spread into silo pits and packed well by human labor.
• After
this, pits are covered with clay paste to make them air-tight.
• Soon
fermentation sets in.
• During
the process lactic acid, butyric acid, propionic acid and trace amount of
alcohol may be formed.
• In
about three months, a highly palatable cattle food is formed inside the pit.
Methods
of Silgae Production:
• The
main role of microorganisms in silage production is to ferment the different
organic component present in plants and produce organic acids like lactic acid,
butyric acid, propionic acid.
• The
organisms mainly involved in the fermentation process are lactobacilli, some
anaerobic Clostridium, Some yeasts, moulds.
• Lactobacillus
plantarum and L. brevis are most active and the lactic
acid produced by them inhibits the growth of other bacteria.
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