Blood Required per ml of Milk Produced

For the production of 1 ml of milk, the quantity of blood that passes through secretory tissues of the mammary gland is about:

Correct Answer: 500 ml

Approximately 400–500 ml of blood must pass through the secretory tissues of the mammary gland to produce 1 ml of milk. This enormous blood flow is necessary because milk synthesis requires continuous delivery of precursors (glucose, amino acids, fatty acids, minerals, vitamins) from blood to mammary secretory cells (alveolar epithelial cells).

Circulatory System of the Udder

• Arterial supply: External pudic artery (mammary artery)
• Venous return (3 primary routes):
  1. Subcutaneous abdominal vein (milk vein) — 1st route; acts as an index of milking ability (prominent milk vein = high yielder)
  2. External pudic vein — 2nd route
  3. Perineal vein — 3rd route

Practical Significance

The blood-to-milk ratio (500:1) explains why high-producing cows have visibly prominent milk veins and why mammary health is so critical — any disruption in blood flow (e.g., mastitis-related inflammation, injury) directly reduces milk synthesis.

Why Other Options Are Wrong

• 100 ml → far too low; not enough to supply all milk precursors.
• 1000 ml → overestimate; 500 ml is the accepted figure.
• 200 ml → insufficient; documented requirement is 400–500 ml.