VPB 121: Veterinary Physiology - II (2+1)

RUMEN PROTOZOA 

• Many species of protozoa are active in rumen.
• All protozoa are strictly anaerobes and found only in ruminants.
• Ciliates form the bulk of protozoa and flagellates are present to a very limited extent.
• The ciliates belong to two families.

• Many species of micro-organisms are present in the rumen and variations occur in number of certain species with time after feeding, dietary regime and individual differences.
• Protozoal number is affected by pH (<5.5), type and composition of diet, season and frequency of feeding. Highly digestible diets increase their number.
• Protozoa store large quantities of reserve starch, which is used when exogenous energy supply is exhausted. Some facultative bacteria are also present.
• The microbes have a volume of 3.6% of strained rumen fluid and this volume contains 50% ciliate protozoa and 50% bacteria.
• Metabolic activity of bacteria is far greater than protozoa though total volume of small bacteria might be same as ciliate protozoa, which is due to greater surface area provided by the bacteria.
• Protozoal number range between 10⁵ and 10⁶ per ml fluid. Most of the rumen bacteria and protozoa are strict anaerobes.

Isotrichidae family

Ophyroscoledia family

Role of protozoa

• Increase in digestibility and weight gain is observed in faunated animal than in defaunated animals. But the absence of protozoa does not affect the animal performance.
• The protozoa help to stabilise the rumen fermentation, by ingesting feed particles and storing reserve polysaccharides and they may control the availability of substrates by sustaining uniform fermentation between feedings.
• Mixed protozoal-bacterial protein is better in quality than bacterial protein alone in contributing essential nutrients to ruminant animal.