Learning Reproduction in Farm Animals

12-Lactation

Learning Objectives:

To understand the anatomy of a mammary gland, how the mammary gland develops, how it secretes milk, what controls milk secretion and why colostrum is important.

Anatomy of the Mammary Gland

Gross diagram of gland (cow)

Mammary Gland of Sow and Mare

Diagram of Avelolus

Comparison of Colostrum to True Milk

Composition of colostrum and milk of holstein cow
Constituent	Colostrum (%)	2nd and 3rd Day Milk-Colostrum (%)	Milk (%)
Fat	6.0	3.5	3.5
Nonfat solids	22.3	12.5	8.8
Protein	18.8	7.5	3.3
Immune globulins	13.1	1.0	0.1
Lactose	2.5	4.0	4.6

Calf can absorbe immunoglobulins with decreasing efficiency up to 24 hours after birth.

Calf's immune system not functional until 1-2 months post-partum.

True Milk Production:

500-1000 liters of blood pass through gland to produce 1 liter of milk.

Blood precursors of the milk constituents in the ruminant.
Milk constituent	Blood Precursor
Water	Water
Lactose	Glucose
Protein
Casein	Amino Acids
ß-Lactoglobulin	Amino Acids
a-lactalbumin	Amino Acids
Milk serum albumin	Blood serum albumin
Immune globulins	Immune globulins
Fat
Fatty acids	Acetate, ß-hydroxybutyrate, blood lipids
Glycerol	Glucose, Glycerol from triglycerides
Minerals	Minerals
Vitamins	Vitamins

Lumen of Alveoli

Maintenance of Milk Production:

Metabolic hormones involved

Thyroxine & Triiodothyroine (Thyroid)
Insulin
Corticosteroids
Growth hormone

Need suckling stimulus + removal of milk

oxytocin - milk let down
As gland fills, pressure shuts off milk secretion

Example: Milk a cow 2x vs. 3x/Day, Get a 15-20% in milk production

Problems with milk let down:

Fear or Stress

Causes adrenalin which

Inhibits oxytocin release
¯ Response of myoepithelial cells to oxytocin
Vasoconstricts - ¯ oxytocin supply to gland

Learning Reproduction in Farm Animals

12-Lactation

Learning Objectives:

Anatomy of the Mammary Gland

Maintenance of Milk Production:

Illustrated Notes

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