Small-Scale

Dairy Farming Manual

Volume 4 

Husbandry Unit 7.1
 PHYSIOLOGY OF MILK PRODUCTION


page 87

Extension Materials
Why is knowing about the physiology of milk production important? (5-8)

1 So you can improve your:
- feeding
- management.

What is your cow's udder like? (9-41)

2 The udder is a skin gland with four quarters and teats.

Where does your milk come from?(42-46)

3 Cells in the udder take nutrients from the blood and produce milk substances.

What affects milk production? (47-60)

4 Many factors in:
- breeding
- feeding
- husbandry.
 

 

  page 89

5 Breeding affects milk production
6 but so do your feeding and management.
7 Knowing about the physiology of milk production helps you to improve your feeding and management
8 and to produce more high quality milk and increase your income.
 

 

  page 90

9 The udder is a well developed skin gland.
10 It is like sweat glands and tear glands which also secrete fluids to the outside of the body (exogenous glands).
11 All female mammals have an udder for feeding their young
12 and your cow's long lactation period gives milk for you as well as her calf.
 

 

  page 91

Outside the udder

13 The udder weighs between 10-30 kg without milk.

Signs of a good udder are:
- level
- left and right sides similar size.

 

14 The skin covers the udder and protects it from rubbing and from bacteria.
But it is not strong enough to support the udder.
15 Strong tissues called ligaments help to suspend the udder.
Two bands run along each side of the udder.
16 One band runs down the middle of the udder between the right and left halves.
The middle ligament meets the two side ligaments at the bottom, making a strong sling.
 

 

  page 92


17 The udder has 4 quarters and 

the two quarters on the left are clearly divided

from the two quarters on the right.
 
 

 

18 It is possible for a cow to have disease in one quarter without affecting the other quarters.
19 The front and rear quarters of the udder are not clearly separated.
The rear quarters are larger and produce about 60% of the milk.
20 Each quarter usually has one teat and the rear teats are usually shorter than the fore teats.
 

 

  page 93

21 The teat has:
 

- an opening for milk to come out
- a muscle to close the opening
 

- a lining to protect against bacteria.
 

 

22 Signs of good teats are:
- moderate size
- good position in quarter
- good muscle tension to stop leaks but allow easy milking.
23 Consult your extension worker about calves with more than 4 teats.
Removal of extra teats helps protect against mastitis.
page 94


Inside the udder
24 Inside the udder you can see lobes which produce milk.
The milk from each lobe passes through large ducts to the gland cistern which can store about 1/2 l milk.

Folds in the tissue help to keep the milk in the gland cistern until the cow is suckled or milked.

The teat is hollow and can hold a small amount of milk.

The streak canal (about 1 cm long) is at the end of the teat and leads to the outer opening.

The canal is involuntarily closed between milkings.
 

  page 95

25 Each lobe has a number of lobules and one large duct which drains the milk.
Connective tissue separates the lobules.
26 Each lobule has many alveoli and a duct which drains the milk from the lobule into the lobe duct.
27 Through a microscope, you can see that each alveolus has a small duct which drains milk into the lobule duct.
28 The alveolus is like a small sac.
The cells on the wall secrete particles of milk fat covered in protein into the hollow centre of the alveolus.
 

 

  page 96


29 The mammary ducts drain the milk from the lobes into the gland cistern.
These ducts only store and drain milk.

 

30 The streak canal secretes a liquid which fights bacteria.
A muscle closes the streak canal.
If the muscle is loose, milking is faster but it is easier for the cow to get udder infections.
The blood system
31 Arteries carry blood from the heart to the udder and carry food and oxygen.
Veins carry blood with waste products away from the udder.
32 Looking from the back, you can see the milk veins and other veins and the middle ligament.
 

 

  page 97



 33 Blood flow is important for milk production.
About 500 l of blood must flow through the udder to produce 1 l of milk.
34  The nerve and the endocrine system
Some nerves send messages from the brain to the udder. This controls blood flow and milk production.
Other nerves send messages from the udder and other parts of the body to the brain about touch, temperature and pain. The body then releases hormones which also control blood flow and milk production.
 page 98

35 Touching and washing the udder sends a message to the brain and glands release a hormone oxytocin into the blood.
This helps milk let-down.
36 Excitement and pain also send messages to the brain.
Glands release another hormone epinephrine which reduces blood flow and milk production.
37  The Lymph System

Lymph ducts drain colourless fluid from tissues into the blood vessels.
page 99


 38 You can feel some of the lymph nodes through the skin.
They are part of the cow's immune system and help fight disease.
39 Near parturition, the lymph ducts cannot drain enough fluid from the udder which swells more than normal.
This is called udder edema.
40 Milking does not help because the fluid is between the cells and not in the milk ducts.
41 Reducing salt intake may help because salt keeps water in the cow's body.
If the swelling is bad, call your vet who can give drugs.
 

 

  page 100

42 Each alveolus has cells which produce the substances in milk e.g. sugar, fat and protein.
43 Each cell in the alveolus has many structures inside it.
To produce milk the cell:
44
-takes nutrients from the blood
45
-produces the milk substances inside the cell
 

 

  page 101


 46

-releases milk substances into the alveolus where they mix with water to form milk.

Heredity

47 Different breeds and different cows can produce different amounts of milk.

Nutrition

48 Your cow needs the right amounts of feed, roughage and concentrates for maintenance and production rations.


 

49 Under feeding and over feeding lead to poor milk production.

 

  page 102


50                                                      Time after calving
51                                                         Dry period
If you dry off your cow for 8 weeks before calving, your cow will produce more milk after calving.If the dry period is too long or too short, your cow will produce less milk.
page 103


52                                                          Age
53                                Body size
54                          Time after milking
If you do not milk your cow, your cow will not produce milk. You dry off your cow.
page 104

55                         Number of milkings
You can milk your cow 3 or 4 times a day. You get a little more milk but:
                                   - you have to give more feed
                                   - you have to do more work.
Temperature
56 If your cow is hot, she will eat less and produce less milk.
57 Keep your cow cool with:
- insulated roof
- shade
- fan or breeze
- shower.
 page 105

58 Gentle exercise helps milk production

 

59 but make sure your cow is quiet and calm around milking time.
Disease

60 If your cow has mastitis, milk fever or other disease, the quantity and the quality of your milk is lower.

Call your vet.

  page 106


What do you know about the physiology of the udder?
     
    Importance
    Knowledge of physiology of the udder helps improve:
    1 feeding and management
     (6-7)
    2 milk production 
    (8)
    What the udder is
    1 Skin gland 
    2 Milk production 
    What the udder is like
    1 Exterior
    - weight and appearance 
    (13)
    - skin 
    (14)
    - supporting tissues 
    - quarters 
    - teats 
    2 Interior
    - gland cistern 
    (24)
    - lobes, lobules and alveoli 
    - gland cistern and streak canal 
    3 Blood system 
    4 Nerve system 
    5 Lymph system 
    Milk production 
    Factors affecting milk production
    1 Heredity 
    (47)
    2 Nutrition 
    3 Time after calving 
    (50)
    4 Dry period 
    (51)
    5 Age 
    (52)
    6 Body size 
    (52)
    7 Time after milking 
    (54)
    8 Number of milkings 
    (55)
    9 Temperature 
    10 Exercise and calm 
    11 Disease 
    (60)

page 107&108