Mammary Gland Health p1015-1043

Question 1

Starting at the streak canal, list the anatomic structures as you move proximally.

Answer 1

Streak canal —> Teat cistern —> Gland cistern —> Large ducts —> Lobe —> Lobules —> Alveoli

Question 2

Milk letdown occurs in response to what? How hormones are involved?

Answer 2

Tactile stimulation of the teat triggers a neurohormonal reflex, causing the pituitary gland to release oxytocin. Milk is then ejected from the alveoli into the cisterns.

Question 3

List ways the mammary gland is protected by invading pathogens.

(3)

Answer 3

1. Teat canal barrier, complete with protein-rich keratin that plugs the canal
2. Polymorphonuclear neutrophils
3. Innate immune system (complement, lactoferrin and acute-phase proteins)

Question 4

In cases of mastitis, where does lactoferrin come from and what does it do to prevent multiplication of microorganisms?

Answer 4

Lactoferrin comes from both mammary epithelial cells and neutrophil granules. It is responsible for sequestering iron and preventing iron-dependent microorganisms from multiplying.

Question 5

What complex do neutrophils express, in order to anchor them to vascular and intercellular adhesion molecules?

Answer 5

Pro inflammatory mediators, like IL-8, leukotriene B-4 and complement 5a serve as chemotatic agents. Neutrophils then express CD11b/CD18 complex that causes margination and ultimate migration between endothelial and mammary epithelial cells into the milk.

Question 6

CD14 receptors allow neutrophils to bind to what portion of bacteria, facilitating nonopsonic phagocytosis of G (-) bacteria?

Answer 6

Neutrophils bind to bacterial LPS, allowing phagocytosis of G (-) bacteria.

Question 7

What is the most important neutrophil receptor for opsonic phagocytosis, enabling phagocytosis of Ab-coated pathogens?

Answer 7

The Fc receptor binds to Fc region of Ig, particularly IgG2 and IgM, and is important for neutrophils.

Question 8

Out of the following Igs, which are opsonizing and which are nonopsonizing?

IgG1
IgG2
IgA
IgM

Answer 8

Opsonizing - IgM and IgG2 (enables efficient phagocytosis of microorganisms by neutrophils)
Nonopsonizing - IgG1 and IgA (neutralization of bacterial toxins, agglutination of bacteria and px of bacterial adherence to epithelial cells)

Question 9

How does can an intramammary infection play a role in oocyte and embryonic degradation, leading to cows with mastitis having decreased conception rates?

(eg. LPS)

Answer 9

LPS induces a prolonged release of inflammatory mediators, including PGF2alpha leading to uterine smooth muscle contraction and luteolysis, a gradual decline in plasma progesterone and thus abortion, especially in the first trimester

Question 10

What contributes to the immunosuppression during the periparturient period, that reduces the mammary gland defenses?

(3)

Answer 10

1. Increased circulating cortisol
2. Decreased neutrophil marginalization and recruitment
3. Increased and early onset of apoptosis of neutrophils

Question 11

During the periparturient period, cattle can undergo a negative energy balance. This increases the production of NEFAs from adipose tissue. List the negative effects this causes, that decreases mammary defense mechanisms.

Answer 11

NEFAs lead to undesirable expression of pro inflammatory mediators, adhesion molecules and reactive oxygen species.

Question 12

What is the threshold of SCC that defines a mammary quarter as healthy?

A) < 100,000 cells/mL
B) < 200, 000 cells/mL
C) < 400, 000 cells/mL
D) < 1.2 million cells/mL

Answer 12

B) < 200,000 cells/mL

Question 13

The CMT for detecting IMI consists of mixing a detergent/bromcresol purple with a milk sample. List the different scores and what they mean.

Answer 13

Negative - no precipitate - 0-200K cells/mL
Trace - slight precipitate - 150-500K cells/mL
1 - distinct precipitate, no gel - 400K-1.2 mill cells/mL
2 - some gel formation - 1.2-5 mill cells/mL
3 - distinct gel that covers paddle - > 5 mill cells/mL

Question 14

What does the National Mastitis Council specify in regard to the aseptic isolation of more than one bacterial species from an individual animal?

Answer 14

The NMC specifies that if more than one bacterial species is isolated aseptically, from a milk sample, it is most likely contaminated.

Question 15

Opportunistic organisms are in the cow’s environment, and when mammary defense mechanisms are lessened, they can cause IMI. There are environmental pathogens and contagious pathogens that get transferred through the milking process. List some common pathogens in these two categories.

Answer 15

Environmental - Gram (-) bacteria much as E. coli and Klebsiella

Contagious - host adapted bacteria, S. agalactiae (very controlled and not isolated often), S. aureus and Mycoplasma bovis

Question 16

Pick the mastitis pathogen that most likely described by the following: major mastitis pathogen; a chronic and subclinical IMI; if clinical IMI, systemic signs; adheres to and invades mammary epithelial cells and interstitial tissue; resists phagocytosis by neutrophils with a capsule that inhibits opsonization; exotoxins that damage and result in fibrosis and abscess formation; difficult to treat and seldom resolves spontaneously

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 16

F. S. aureus

This pathogen can also invade mammary defenses bc of the biofilm certain strains can make

Question 17

Pick the mastitis pathogen that most likely described by the following: obligate udder pathogen; control measures highly effective; IMI usually subclinical; adheres to epithelial cells in mammary gland and localizes primarily in ducts; chronic infections cause tissue damage and fibrosis, with subsequent permanent decrease in milk production;

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 17

G. Streptococcus agalactiae

Question 18

List two other environmental Streptococcal species that cause clinical and subclinical mastitis and the primary reservoir of these opportunistic pathogens.

Answer 18

S. uberis and S. dysgalactiae are commonly found in bedding materials as well as shed in feces. These environmental streptococcal infections are initiated in the dry period, roughly 50% of the time.

Question 19

Pick the mastitis pathogen that most likely described by the following: a coliform bacteria; from organic bedding material, under warm, wet conditions; does not adhere to or invade the epithelial cells; can be quickly eliminated; IMI of short duration and pathogen rarely isolated

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 19

B. E. coli is a coliform bacteria that can cause short durations of clinical or subclinical mastitis

Question 20

Pick the mastitis pathogen that most likely described by the following: a coliform bacteria; from organic bedding material, under warm, wet conditions; does not adhere to or invade the epithelial cells; can be quickly eliminated; has a significant and long term impact on milk yield; long duration of infection; sawdust bedding has been implicated

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 20

C. Klebsiella oxytoca and pneumoniae

Question 21

Pick the mastitis pathogen that most likely described by the following: risk factors for mastitis are co-mingling of cattle from multiple herds, off-site rearing of calves, stressors like overcrowding, unhygienic milking practices and insufficient biosecurity; shedding can occur through nasal or vaginal secretions, feces or milk; IMI can be persistent subclinical; once clinical, can affect multiple glands and will not respond to Abx; PCR diagnosis from a milk sample is best bc rapid; infected cows should be considered infected permanently

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 21

D. Mycoplasma with bovis being the most common associated with mastitis

Question 22

Pick the mastitis pathogen that most likely described by the following: occasionally associated with mastitis, but also considered normal flora and a contributor to BRD; in individual animals, hematogenous or lymphatic spread can be considered from the respiratory tract, but not a cause for a herd outbreak; herd outbreak can be caused from nasal secretions, cow-to-cow spread during milking;

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Pasteurella multocida
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 22

E. Pasteurella multocida

Question 23

Pick the mastitis pathogen that most likely described by the following: algae that has been isolated from feces of cows and other warm-blooded animals such as pigs and rodents; found in moist areas like soil, mud, vegetation and water; risk factors include intramammary infusions of unapproved products and use of internal teat sealants at dry off; IMI are both subclinical and clinical; treatment not recommended

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prototheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 23

E. Prototheca

Question 24

Pick the mastitis pathogen that most likely described by the following: commonly found in the streak canal; occasional IMIs with little impact on milk yield and low SCCs; transmitted from cow to cow

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 24

A. C. bovis

Question 25

Pick the mastitis pathogen that most likely described by the following: IMI has an acute purulent symptoms; transmitted by flies or environmental exposure, especially if teat ends are damaged; often termed summer mastitis;

A. Corynebacterium bovis 
B. E. coli
C. Klebsiella
D. Mycoplasma 
E. Prothetheca 
F. Staphylococcus aureus 
G. Streptococcus agalactiae
H. Trueperella pyogenes

Answer 25

H. T. pyogenes

Question 26

There is a 10 point plan detailed by the National Mastitis Council. List these points.

Answer 26

1. Establish goals for udder health
2. Maintain a clean, dry, comfortable environment
3. Proper milking techniques
4. Proper maintenance and use of milking equipment
5. Good record keeping
6. Appropriate management of clinical mastitis during lactation
7. Effective dry cow management
8. Biosecurity of contagious pathogens and marketing of chronically infected cows
9. Regular monitoring of udder health status
10. Periodic review of mastitis control programs

Question 27

Detail the gold standard for premilking teat disinfection.

Answer 27

Applying the premilking disinfectant —> allowing for a sufficient contact time —> using single use cloth/paper towel for each cow —> two or three streaks of foremilk

Question 28

What is the period of time between stimulation and attachment of the milking unit?

A) 30 seconds
B) 60-90 seconds
C) 120 seconds
D) 360 seconds

Answer 28

B) 60-90 is the ideal time length between stimulation and attachment; disturbances in milk flow and yield were noted if this increased to greater than 3 minutes

Question 29

At what milk flow rate should the milking units be removed?

A) 0 L/min
B) 0.5-1 L/min
C) 1-2 L/min
D) 1.5-2.5 L/min

Answer 29

B) 0.5-1 L/min of milk flow

Question 30

How much of the teat should be covered with disinfectant, post milking?

A) at least the streak canal
B) 50%
C) 75%
D) 100%

Answer 30

C) 75% of the teat should be covered