Nature of Rumen as an Ecosystem

The rumen is a-

Correct Answer: Open & continuous ecosystem

The rumen is an open and continuous ecosystem. 'Open' because feed/water continuously enters and digesta continuously exits. 'Continuous' because microbial fermentation proceeds uninterrupted 24 hours a day.

Ruminal Ecosystem Parameters

• Normal ruminal pH: 6.5–6.8
• Optimum temperature: 39°C
• Redox potential: (−) 350 mV (highly reducing/anaerobic)
• Gas ratio: CO₂ : CH₄ = 65 : 35
• VFA ratio: Acetate : Propionate : Butyrate = 65 : 20 : 10
• Normal VFA level: 80–120 mEq/L

Ruminal Microbial Population (per ml of rumen liquor)

• Bacteria: 10¹⁰–10¹¹ (most numerous)
• Bacteriophage: 10⁹
• Protozoa: 10⁶ (majority are ciliate protozoa; they determine microbial population by eating bacteria)
• Fungi: 10³ (mostly flagellated; function: substrate penetration by breaking lignocellulosic bonds)

Bacteria Details

• Majority: gram-negative obligate anaerobes
• Lactic acid producers: facultative anaerobes (attach to ruminal wall near trace O₂)