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1. Bovine mammary
gland
14-Arid-2022
PMAS
FAISAL
SHAHZAD SOMROO

2.  Front : Rear quarter = 40 : 60
 Support system: ligaments and connective
tissue
 Secretory and duct system: exocrine gland
 Blood supplies and capillary structures: 400-
500 kg of blood pass through the udder  1
kg of milk
 Lymph system
 Innervation of the udder: milk let down reflex
Mammary gland structure

6. The udder of a cow producing 40 lbs. of milk
in a 12-hour period can weigh up to 100 lbs.

7.  Skin and Subcutaneous Tissue :
 a minor capacity to suspend and stabilize the udder
 protects the interior of the udder from injury and
bacteria.

8. Median Suspensory Ligament
-The most important support for the udder (MSL)
-Clearly divides the udder into the right and left halves
-The MSL is composed of elastic tissue that stretches
to allow the udder to expand as it fills with milk.

9. Lateral Suspensory Ligament
-Chiefly fibrous and non-elastic (don't stretch).
-The LSLs extend along both sides of the udder
and at intervals send sheets of tissue into the gland
to provide support to the inside contents of the udder

10.  Pendulous Udder
If the Medial and Lateral
suspensory ligaments weak
en and the cordlike structur
e that attaches the fore udd
er to the body wall stretches
, the result can be a pendul
ous udder.
 Disadvantages of a
pendulous udder include:
 Cleaning difficulty
 Milking difficulty
 Risk of injury
 Risk of mastitis

11. Streak Canal
- approximately ¼ to ½ inch in length,
-closed by sphincter muscles.
The streak canal serves two very important purposes.
1. it prevents the escape of milk between milkings
2. it acts as a barrier to the entry of bacteria and
other foreign material.
-Milking speed is related to the size of the canal
and also the tightness of the sphincter muscles.

14. Keratin
- The cells that line the streak canal contain keratin.
- Keratin is a waxy substance similar to ear wax.
- This substance helps to seal the teat end between milkings.
- Keratin also has properties that inhibit the growth of bacteria
(disease organisms).
- The physiological process of the teat canal forming a keratin
plug after drying off appears to be a major front-line defensive
mechanism.

15. Fürstenburg's Rosette
- Fürstenburg's rosette is located
directly above the streak canal.
-It is made up of loose folds of
membrane that smooth out as milk
accumulates in the udder.
-This aids in blocking the escape of
milk between milkings.
-This can be damaged by improper
milking or by improper use of
mastitis infusion nozzles.

16. Teat Cistern
-The teat cistern is the cavity inside
the teat that holds from 1/2 to 1 1/2
ounces of milk, depending on the
size of the teat. -The teat cistern is
the holding chamber where milk ac
cumulates before it is removed thro
ugh the teat end during milking.
-It refills continuously during
milking.
-This is where the first milk to be
removed accumulates between mil
kings.

17. Gland Cistern
The gland cistern joins to the
teat cistern at the base of the
udder. The gland cistern, whic
h can vary greatly in capacity, f
unctions as a collecting vessel
for milk from the major milk du
cts that flow into it. The gland c
istern fills rapidly during milk le
tdown.

19. Secretory System
 Milk is released by alveoli into ducts which
carry milk to the gland cistern.
 Between milkings approximately 40% of
the milk is stored in the teat and gland cist
erns and the major ducts while the remaini
ng 60% is stored in the alveoli.

20. Alveoli
-grape-like clusters
-Each alveolus is composed
of a single layer of epithelial
cells surrounding a central ca
vity.
-These cells absorb nutrients
from the blood, transform
them into milk and discharge
the milk into the cavity of the
alveolus.
-Each alveolus is also
surrounded by specialized
muscle cells known as myoe
pithelial cells that are respon
sible for milk ejection during l
etdown.

22.  Around the time of calving, the secretory cells of the
alveoli start to produce milk.
 During parturition, there is a large surge of prolactin
and this is the signal to start lactation.
 The important hormones for milk production and the
maintenance of lactation are prolactin, insulin-like
growth factor (IGF)-1 and growth hormone.

24. Milk Let-Down
 Neuro-hormonal reflex
 The suckling stimulus or massaging of the udder stimulates
somatic nerves in the teat, which send a signal to the posterior
pituitary gland and causes the release of the hormone oxytocin
.
 Oxytocin causes the myoepithelial (muscle) cells around the
alveoli to contract.
 For efficient milking, there are several important factors to
remember.
 Stimulate 1 min before milk let-down
 The maximal effect of oxytocin occurs during tfirst 2 to 3 minutes
of milk let-down.
 Stress during cow preparation or during milking will inhibit
oxytocin release.
 Inhibition of oxytocin release

27. Dry period

28. Lactation Cycle
 4 phases of mammary gland
 1. Dry period:Development
 2. Around calving (-4 to +4 days): Differentiation
 3. Lactation: All cell activity directed towards milk
synthesis and no further mammary growth.
 4. Involution of the mammary gland: This is the
gradual but irreversible regression of the gland (i.
e. a reduction in the numbers of active alveoli). Th
is starts after the peak of lactation, but is more pro
nounced during late lactation.

29. Dry period
 The mammary gland of the dairy cow requires a
non-lactating period prior to an impending parturition
in order to optimize milk production in the subseque
nt lactation.
 There is general agreement that an approximate 60-
day non-lactating period is required and that dry peri
ods of less than 40-50 days result in less than optim
al milk yields.
 The dry period is critically related to the dynamics of
intramammary infection (IMI) within a dairy herd.

30.  1) The period of active involution:
 0-30 days after drying-off
 2) The period of steady state involution:
 The period of time the gland is maintained in the fully
involuted state.
 3) The period of lactogenesis and colostrogenesis:
 15-20 days prepartum
 Regeneration and differentiation of secretory epithelial cells
 Selective transport and accumulation of immunoglobulin
 The onset of copious secretion
Physiological Function during the
Dry period

31. Active Involution: Early Dry Period
 Milk composition
 Lactose ↓
 Total protein ↑
 Lactoferrin ↑ : major protein
 Serum albumin ↑
 Immunoglobulin ↑
 Casein ↓
 Mammary cells
 Involution-associated ultrastructural changes begin within
48 hours after cessation of milk removal.
 Large stasis vacuoles in the epithelial cells
 Cell apoptosis and Phagocytosis

32. The Relationship of Active
Involution to New IMI
Factors may favor new infection during the early dry period
 1) A large volume of milk is accumulated and leakage of milk from
teats is often observed.
 2) The contents of the gland are no longer being removed at regular
intervals.
 3) Teat end disinfection is stopped.
 4) The factors of natural defense are only marginally elevated over
normal milk levels during this potentially vulnerable period (first 3 d).
 5) The phagocytic cells are occupied in the phagocytosis of
degenerated epithelial cells, fat and casein.
 6) The phagocytic capabilities of the macrophage and PMN and the
responsiveness of lymphocytes to antigen stimulation are reduced.
 7) Secretion components can act as growth stimulants for certain
bacteria.

33.  In the other side
 The gland should be more resistant to new IMI because of
the elevation in phagocytic cells, lymphocytes, immunoglob
ulins and Lf
 These changes occur too slowly and their antibacterial
action is compromised by other normal events of involution.
 Treatment of glands at or near drying off with colchicine,
endotoxin or the combination of the two compounds resulte
d in a more rapid involution, earlier elevation of resistance f
actors and reduced IMI during the first week of the dry peri
od.
The Relationship of Active
Involution to New IMI

34. Steady State of Involution:
Relationship to New IMI
 The conditions within the mammary gland during
steady state involution can resist the establishment
of new IMI.
 A few volume of fluid
 Greatly reduced of the major constituents of milk
 The concentration of immunoglobulins and Lf are elevated
 The predominant cell type would appear to be the
lymphocyte in uninfected quarters but substantial numbers
of macrophages are present.
 The PMN are generally found in low numbers by
comparison to lymphocytes and macrophages.

35. Lactogenesis-Colostrogenesis:
Relationship to New IMI
 Destructive processes
 Hormonal control
 Formation and accumulation of colostrum: IgG1
 The major components of milk increase 2 wks before
parturition.
 Fat, casein and lactose increase in the 5 days preceding
parturition.
 Volume increase 1-3 days prepartum
 Citrate↑ (harbinger)The molar ratio (citrate:Lf)
increases by approximately 100 fold over the last few
days prepartum.
  A loss of the antimicrobial properties of Lf

36.  Number of cells in secretion of uninfected quarters
gradually decline over the 2 week prepartum period.
 The macrophage appear to be the predominant cell
type.
 The phagocytic ability of macrophages and PMN
appear to be inhibited.
 The susceptibility to new IMI increase caused by the
environmental pathogens
 Little or no protection from dry cow therapy products
Lactogenesis-Colostrogenesis:
Relationship to New IMI

37. Summary
 The susceptibility of the bovine mammary gland to new IMI ↑at both
the beginning and the end of the dry period.
 The early dry period is associated with decreased synthesis of milk
constituents, regression of synthetic tissue (active involution) and in
creased levels of antibacterial factors and/or systems.
 The late dry period is associated with development and
differentiation of synthetic tissue, increased selective transport of Ig
G1 immunoglobulin (colostrogenesis), increased synthesis of milk c
onstituents (lactogenesis) and decreased levels of antibacterial fact
ors and/or systems.
 During both periods fluid is accumulated in the gland.
 A lack of flushing action, teat leakage  bacterial colonization

39. Summary of Changes in Composition of
Mammary Secretion During the Dry Period

40. Dry Cow Therapy

41. Dry Cow Therapy
 The Advantages
 A reduced incidence of new infections during the first 3 to 4
wks of the dry period
 A much higher cure rate than lactational treatment of some
organisms
 An aid in the regeneration of damaged milk secretory
tissues
 A reduced incidence of mastitis in the next lactation
 An avoidance of milk loss due to treatment of mastitis in
lactation
 A reduced level of mastitis, translating into increased milk
production, better quality milk and greater money returns

42. Types of Antibiotic Treatment
 Intramammary infusion products
 1. the quick-release, short-acting types designed
specifically to treat mastitis in lactating cows
 2. the slow-release, long-acting types formulated
specifically to treat subclinical mastitis in dry cows
and to prevent new infections in dry cows: remain
in the udder for ≥ 21 days

43. Drying-off
 Regeneration of new milk secreting cells
 Restore body energy and nutrient reserves
 50-70 days, never less than 40 days before
the expected calving date
 Reducing the concentrate reduce milk yield
 Intermittent milking
 Sudden cessation of milking

44. Dry Cow Treatment Procedure (1)
 Milk the udder out completely.
 Clean and dry teats with a single paper towel or cloth.
 Dip all teats in an effective teat dip. Allow 30 sec before
wiping teats with single service paper towel or cloth.
 Starting with the teats on the far side of the udder,
disinfect the teat ends by scrubbing each for a few
seconds with a separate alcohol-soaked cotton swab
 Treat quarters in reverse order; near side first, far side
last

45.  Insert only the tip of the cannula (6 mm or ¼ in) into
the teat end prior to infusing. Massage the treatment
up into each quarter.
 Dip teats in an effective germicidal product after
treatment.
 Practical teat dip all treated cows at least once a day
for two weeks after drying-off and for two weeks
before calving.
 Remove the cows from the milking herd to prevent
antibiotics from entering the milk supply
Dry Cow Treatment Procedure (2)

55. General Considerations
 Laboratory culture and sensitivity test
 Early dry off
 Number of infusions
 Teat dips
 Vaccination or Immunization
 Sanitation
 No dry period
 Dry cow therapy to Bred Heifers

56. Blanket vs. selective dry cow
therapy
 Blanket dry cow therapy when either;
 BTSCC > 500,000
 4 or more clinical cases /100 cows /3 days
 The quarter infection rate > 15%
 The individual cow SCC average for all cows > 250,000
 Use selective dry cow therapy when the monthly BTSCC stays
consistently <200,000 and the quarter infection rate <15%. Treat
only the following cows;
 Individual cows with peak SCC>250,000
 Cows that had clinical mastitis during lactation
 Cows from which a major organism has been cultured from the
milk.

57. Defense Mechanism
and Immunity of
Mammary Gland

58. Natural Disease Resistance
Factors in the Mammary Gland
 Physical Barrier
 Cellular Immunity
 Humoral Immunity
 Phagocytosis

59. Physical Barrier
 Teat shape
 Streak canal
 Teat sphincter
 Keratin
 Streak canal diameter
 Furstenberg’s rosette
 Intramammary infection
 Bacteria

60. Cellular Immunity
 Leukocyte ~ Milk Somatic Cell
 ~60% are macrophages
 ~30% are lymphocytes
 ~10% are polymorphonuclear cells
 Innate immunity = first line defense
mechanism
 Chemotactic activity by cytokines released
from lymphocytes
 Phagocytosis

61. The process of PMN chemo-attraction into the mammary
gland (From Suriyasathaporn et al. 2000b).

62.  Processes are limited by
 Limit of sources of energy in milk
 Diluted the concentration of cytokines
 Milk fat and protein can interfere the function
Cellular Immunity

63.  Neutrophils
 Predominant cell type in early inflammation
 Phagocytosis
 Oxygen-dependent killing mechanism
 Small antibacterial peptides: the defensins
 Macrophages
 Predominant cell type
 Phagocytosis
 Antigen presenting cell: MHC class II
Cellular Immunity

65.  T-lymphocytes : CD4+ : CD8+ ratio<1 in milk
 T-helper lymphocytes (CD4+):
 Recognition of MHC antigen
 Activating B-lymphocytes
 T-cytotoxic or T- suppressor lymphocytes (CD8+):
 Cytotoxic T lymphocytes: removing old or damaged
secretory cells
 Suppressor T-lymphocytes: control or modulate the
immune response
Cellular Immunity

66.  B-lymphocytes
 Produce antibodies
 Specific pathogen recognition
 Present MHC class II
Cellular Immunity

68. Humoral Immunity
 IgG1, IgG2, IgA and IgM
 Low during lactation  High during non-
lactating period Peak during
colostrogenesis
 IgG1, IgG2 and IgM: Bacterial opsonin
 IgA: agglutination, preventing bacterial
colonization, toxin neutralization

69. Nonspecific Bacteriostatic
Components
 Lactoferrin: an iron-binding protein
 Produced by epithelial cells and leukocytes
 Prevent growth of bacteria
 High during inflammation and involution
 Complement: a collection of proteins in serum and milk
 Lysis of invading bacteria
 Highest in colostrum, inflamed mammary glands, during
involution
 Lowest during lactation
 Lysozyme: a bactericidal protein in milk
 Cleaving the peptidoglycans from the cell wall or cell
membrane of bacteria
 Little protection to the bovine mammary gland

70.  Lactoperoxidase-thiocyanate-hydrogen
peroxide system
 Bacteriostatic for Gram+ bacteria
 Bactericidal for Gram- bacteria
 Low oxygen tension of the mammary gland can
limit the effective of this system.
 Cytokines: G-CSF, GM-CSF, IFN-, IL-1, IL-2
Nonspecific Bacteriostatic
Components