• Fermentative vs Glandular Digestion:
• In glandular digestion (monogastrics), host enzymes hydrolyze macromolecules into their constituent monomers (proteins $\rightarrow$ amino acids; starch $\rightarrow$ glucose) without altering basic carbon skeletons.
• In fermentative digestion, symbiotic anaerobic microbes extensively alter substrates, converting hexose sugars and plant cellulose through anaerobic glycolytic pathways into entirely different metabolic end-products—predominantly Volatile Fatty Acids (acetate, propionate, butyrate), methane, and carbon dioxide [Option 4].

Correct option: (4) Substrates are more extensively altered in fermentative digestion than in glandular digestion