Contents of Raft Layer vs Rumen Liquor

Raft layer & rumen liquor contains-

Correct Answer: Longer forage particles & finer particle respectively

The Raft layer contains longer forage particles (coarser fiber). The Rumen liquor contains finer particles (smaller, denser fragments from microbial digestion).

Physical Significance

• Longer fiber particles in the raft float because of their lower density and entrapped gas within fibers
• Longer fibers physically stimulate the rumen wall and cardia → trigger regurgitation reflex (rumination begins in reticulum)
• Through rumination, long particles are re-chewed → reduced to <1–2 mm fine particles → sink into rumen liquor → can exit through reticulo-omasal orifice

Particle Size and Production Effects

• High roughage diet (long fiber → high raft): High acetate production → high milk fat%
• High concentrate/grain diet (fine particles → high rumen liquor): High propionate production → high milk yield

Clinical Note — Subacute Ruminal Acidosis (SARA)

• High-producing dairy cows fed too much concentrate → insufficient raft → less rumination → less saliva (less buffering) → pH drops → SARA → reduced milk fat (low-fat milk syndrome)