This document provides an overview of the lactation process in dairy cows. It discusses how milk is produced in the mammary gland and secreted, the mechanism of milk letdown triggered by oxytocin release, and various milking procedures and factors that affect milk quantity and quality. The document also describes the pathway that a nerve impulse travels when a cow associates milking with the letdown reflex, causing oxytocin release from the pituitary gland and milk ejection from the alveoli through myoepithelial cell contraction. Stress can inhibit this process by releasing epinephrine instead of oxytocin.

1. To dairy raisers,
this is the most
awaited moment...
... now they
have the calf
and of course
the milk!
Lactation is the
production of milk
by the mammary
gland or udder.

2. At the end of the unit, the students
should be able to:
 Identify the parts and functions of the
mammary gland.
 Describe how milk is secreted in the
mammary gland.
 Understand the mechanism of milk
letdown.

3.  Distinguish various milking procedures.
 Point out milk handling techniques.
 Enumerate the different factors that
affect the quantity and quality of milk.

8. • (A) that a cow associates with milking causes a nerve impulse (B) to
travel via the inguinal nerve(1) to the spinal cord(2)and the brain(3) The
brain causes the release of oxytocin (D) from the posterior pituitary (C).
Oxytoxin is released into a branch of the jugular vein(4) and travels to
the heart(5) and is then transported to all parts of the body by the arterial
blood. The oxytocin reaching the udder leaves the heart by the aorta(6)
and enters the udder through the external pudic arteries (7).On the
udder, it causes the myoepithelial cells to contract, resulting in milk
ejection from the alveioli.
• When cows are frightened, angered, in pain, or ill-treated, they will not
let-down their milk.This is caused by the release of epinephrine
(adrenalin) from the adrenal gland which inhibits the release of
oxytocin.