• Rumen pH and VFA Absorption Kinetics: Volatile fatty acids (acetate, propionate, butyrate) exist in the rumen in chemical equilibrium between un-dissociated (protonated, non-ionized, $\text{HA}$) and dissociated (ionized, $\text{A}^-$) forms ($pK_a \approx 4.8$):

• Mechanism of Increased Absorption:
• As ruminal pH drops (acidifies towards $pK_a$), the proportion of lipid-soluble, un-dissociated $\text{HA}$ rises substantially.
• Non-ionized VFAs cross the lipid bilayer of the ruminal stratified squamous epithelium rapidly via simple passive lipophilic diffusion, causing the rate of VFA absorption to increase.

Correct option: (2) increase

• Statement (I) is False: Megasphaera elsdenii is the primary lactate-utilizing ruminal bacterium responsible for converting lactic acid to propionate. It is enriched in highly efficient, grain-adapted ruminants where it prevents subacute ruminal acidosis (SARA), and is lower in less efficient animals.
• Statement (II) is True: Ruminal propionate synthesis serves as an alternative hydrogen sink ($2\text{H}^+ + 2e^-$), competing directly with methanogenic archaea for metabolic hydrogen. An increased Propionate : Acetate (P:A) ratio decreases enteric methane ($CH_4$) emissions and increases metabolizable energy retention.
• Conclusion: Statement (I) is false, but Statement (II) is true.

Correct option: (4) Statement (I) is false but Statement ({I) is true.