VFA Responsible for Lactose Production

Which Volatile Fatty Acid (VFA) is primarily responsible for milk sugar (lactose) production in ruminants?

Correct Answer: Propionate

Propionate is gluconeogenic — it is converted to glucose in the liver via the succinate pathway, and this glucose is used in the mammary gland for lactose synthesis.

Pathway: Propionate → Lactose

Propionate → (Liver gluconeogenesis) → Glucose → (Mammary gland) → Lactose (Glucose + Galactose)

Practical Application

• High-concentrate diet → more propionate → more gluconeogenesis → more lactose → higher milk yield
• High-roughage diet → more acetate → more milk fat → higher milk fat percentage

ATP Production from VFAs

• 1 mole Acetate → 10 ATPs
• 1 mole Propionate → 17 ATPs
• 1 mole Butyrate → 25 ATPs

Note: 1 gram of Propionic acid can theoretically provide 1.23 g of glucose.