Milk Quality and Mastitis Control

Question 1

True or False: pathogens are able to move easily between the quarters of the udder

Answer 1

false; these are separated by connective tissue

Question 2

What type of cells synthesize and secrete milk?

Answer 2

alveolar cells; 60% milk storage

Question 3

Milk letdown is induced by what?

Answer 3

oxytocin-induced contraction of myoepithelial cells

Question 4

Following milk letdown, the milk is transported to where?

Answer 4

gland cistern via ducts (ducts = 20% milk storage)

Question 5

Milk is accumulated in where?

Answer 5

the gland cistern (cistern = 20% milk storage)

Question 6

What is the physiology of milk letdown?

Answer 6

suckling stimulates release of oxytocin > induces milk letdown; this “suckling” is more commonly stimulated by workers

• oxytocin has a very short half life: 2-3 minutes
• milk letdown is inhibited by stress

Question 7

If milk letdown does not occur, what is the issue with this?

Answer 7

60% of the milk is stored in the alveolar cells, so only 40% of the milk produced will be readily accessible without milk letdown

Question 8

What are the various methods of teat protection?

Answer 8

• skin
• inner and outer sphincters
• keratin plug
  
  • physical barrier
  • bacteriostatic properties

Question 9

What makes up the innate immunity of the bovine udder?

Answer 9

• macrophages
• neutrophils
• NK cells
• complement

Question 10

What are somatic cells and what levels of somatic cells are diagnostic for disease.

Answer 10

• immune cells that move from blood into the mammary gland
• Healthy and non-infected glands: SCC < 100,000 cells/mL of milk
  
  • mostly macrophages, neutrophils, lymphocytes, and epithelial cells
• Infected glands: SCC > 200,000 cells/mL of milk
  
  • mostly neutrophils

Question 11

What is mastitis and what are signs of peracute mastitis?

Answer 11

= inflammation within the mammary gland

• Peracute
  
  • 5 cardinal signs (redness, heat, swelling, pain, loss of function)
  • Systemic signs (fever, anorexia, dehydration, depression, muscle tremors, “down cow”)
  • Fast progression (4-12 hrs) and death

Question 12

What are the signs of acute mastitis?

Answer 12

• 5 cardinal signs: redness, heat, swelling, pain, loss of function
• mild depression and fever

Question 13

What are the signs of subacute mastitis?

Answer 13

• subdued signs of inflammation
• most common presentation of clinical mastitis

Question 14

What are signs of subclinical mastitis?

Answer 14

• inflammation in the absence of gross signs (incr SCC)
• most common presentation of mastitis

Question 15

What are signs of chronic mastitis?

Answer 15

• persistence of inflammation for weeks/months
• continuous process or periodic flare-up cases

Question 16

What pathogens are most commonly associated with mastitis?

Answer 16

most commonly caused by bacterial intramammary infection (IMI); fungi/yeast = least common

• Contagious pathogens:
  
  • cow-to-cow trasmission via fomites
    
    • Strep agalactiae
    • Staph aureus
    • Mycoplasma sp.
• Environmental:
  
  • Strep uberis
  • Strep dysgalactia
  • Coagulase neg. Staph. (CNS)
  • Trueperella pyogenes
  • Coliforms
    
    • E. coli, Klebsiela sp., Serratia sp., Pseudomonas sp.

Question 17

Describe the MOA of Staph aureus in causing mastitis

Answer 17

• causes moderate incr in SCC
• small shedding in milk
• inflammation mediated by coagulases, alpha, beta, and epsilon-hemolysins
• beta-lactamase and deep penetration into tissue: poor response to tx
  
  • consider segregation and culling

Question 18

What is the MOA of Strep agalactiae in causing mastitis?

Answer 18

• does not actively invade parenchymal tissue
• inflammation is mostly subclinical w/ acute flare-ups
• blockage of collecting ducts
• leads to involution of mammary tissue
  
  • replacement of secretory cells w/ scar tissue
  • decr milk production
• marked incr in SCC
• Abx susceptibility
  
  • ampicillin, cephapirin, pirlimycin

Question 19

What is the MOA of Mycoplasma sp. in causing mastitis?

Answer 19

• inflammation is often subclinical w/ acute flare-ups
• clinical cases often progress from 1 to mult quarters b/t 1-3 d
  
  • coffee-grounds appearance to milk
• intro via purchase of diary animals or intro of outside rearing heifers
  
  • biosecurity
• non-responsive to antimicrobial tx
  
  • ID and culling
  • segregation challenge
    
    • need for specialized culture (4-7d for lab results)

Question 20

What is the MOA of Strep uberis in causing mastitis?

Answer 20

• acute and chronic mastitis (similar to Strep agalactiae)

Question 21

What is the MOA of Strep dysgalactiae in causing mastitis?

Answer 21

• infections assoc. w/ teat injury (viral, mechanical, chemical, etc.)

Question 22

What is the MOA of coliforms in causing mastitis?

Answer 22

• peracute to acute mastitis
  
  • sudden and marked swelling of affected quarter
  • fever, mm tremors, rumen stasis, dehydration
  • serous milk (early) w/ fibrin or pus (late)
• incr incidence of death and agalactia compared w/ other pathogens
  
  • px particularly guarded for Klebsiella sp.
• Fast recovery if inflamma contains pathogen proliferation
  
  • milk production recovered in 1-2 weeks

Question 23

Why is early lactation a high risk period for developing mastitis?

Answer 23

• immunosuppression occurs during early lactation (3-4 wks postpartum)
  
  • stress and cortisol concentrations around parturition
  • negative nutrient balance
  • oxidative stress

Question 24

What is the impact of elevated milk production around peak lactation?

Answer 24

loss of teat canal integrity and milk leakage

Question 25

What are some reasons that first 21 days of the dry off period (i.e. involution) is a time of increased susceptibiltiy to new IMIs?

Answer 25

* pressure from milk buildup (production declines and cows are not milked) * potential milk leakage w/o constant teat end disinfection * death of secretory cells and active tissue remodeling * failure to form keratin plug

Question 26

What are some reasons that last 7-14 days of the dry off period (i.e. involution) is a time of increased susceptibiltiy to new IMIs?

Answer 26

* pressure from colostrogenesis * decr lactoferrin and resident leukocytes * colostrum components impair function of immune cells * rapid tissue differentiation and oxidative stress

Question 27

What are the best ways to prevent IMIs during the dry off period?

Answer 27

* health management - biosecurity * segregation and culling of chronically infected cows * nutrition * cow comfort - clean and dry environment * vaccination * teat skin condition * excellent milking procedures * **improve immunity peripartum**

Question 28

What are the goal and objectives of milk parlors and machine milking?

Answer 28

Goal: milk cows quickly, gently, and completely * incr milk harvested * decr discomfort of cows * decr risk of injury and mastitis

Question 29

What steps are a part of the cleaning and stimulation process in milk parlors?

Answer 29

* apply disinfectant (pre-dip) * remove foremilk (cistern) * 2-3 strings from each quarter * 15 sec per cow * check for mastitis * clean/black floor * mastitic milk cannot go to bulk tank * dip-strip vs. strip-dip vs. dip-strip-dip

Question 30

What steps are a part of the contact time for disinfection process in milk parlors?

Answer 30

* **30 seconds** * proper udder preparation **removes 75% of bacteria present on teat skin** to attachment * bacteria left on teat will end up in milk * past 30 seconds: * strip and wipe teats with a single-use towel (teat and teat end)

Question 31

What is the purpose of the lag time in milk parlor procedings and how long should this be?

Answer 31

* allows cow to respond to manual stimulation * 70-80 sec

Question 32

What steps are a part of attaching the cow's udder to the milking machine?

Answer 32

* 90-120 sec after onset of manual stimulation * goal is to **attach unti to clean/dry teats** * **​**prevents liner slips * attention to placement of claw * folded teats * dry quarters

Question 33

Describe the process of milking the cow with the milking machine

Answer 33

* **4-6 min** * machine maintenance * proper pulstor fxn * adequate vaccum presure * fix liner slips * backflow of milk, potential for contamination * avoid over-milking * residual milk (50-100 mL/quarter)

Question 34

What are the steps in detaching the cow from the milking machine and the post-dip?

Answer 34

* cut-off vaccum * avoid teat injury * automatic based on milk flow

Question 35

After milking, cows will return to a ...

Answer 35

* clean and dry pen * fresh food and water * proper heat abatement

Question 36

What are the various severity scoring levels for mastitis?

Answer 36

1. Mild = abnormal milk (clots, flakes, watery) 2. Moderate = abnormal milk + signs of udder inflammation (heat, swelling, pain) 3. Severe = systemic illness (fever, dehydration, wekaness, inappetence) \*tx based on severity: intramammary abx, +/- anti-inflammatory, +/- systemic and supprortive tx

Question 37

What are your treatment considerations and diagnostics for chronic cases of mastitis?

Answer 37

* **"three strikes rule" - do not tx quarter \> 3x within a lactation** * \> 2 monthly tests with SCC \> 200,000 cells/mL * consider non-tx options: * **older cows** * **other dz** * **mult quarters** * culling cow * early dry-off

Question 38

What are your options for diagnosing specific mastitis pathogens?

Answer 38

* lab tests: 24-48hrs, except *Mycoplasma* = 7d * on-farm culture: improve timing * UMN bi- and tri-plate * chromogenic selective media

Question 39

How do you decide to treat based off your culture results?

Answer 39

* no growth - do not tx * gram - cleared by time of culture * *Mycoplasma* * gram - = do not tx * robust immune response * incr spontaneous cure * **gram + = treat** * **​**less robust immune response (decr spontaneous cure)

Question 40

What are the cure rates for various IMI pathogens?

Answer 40

* *Strep agalactiae* - 90-95% * CNS - 60-80% * Environmental *Strep* - 40-50% * *Staph aureus* - 20-30%

Question 41

What are your monitoring parameters for herds and mastitis?

Answer 41

* bulk milk SCC and bacterial counts * rate of clinical mastitis * prevalence of subclinical mastitis * presence of contagious mastitis pathogens

Question 42

What is the protocol for dry cow therapy?

Answer 42

* treat all quarters from all cows with long-acting intramammary abx at dry off * +/- teat sealants * particularly important for *S. agalactiae* and *S. aureus* * **Goal: minimize new infections and promote cure during dry period** * Vaccination: * coliform mastitis (*E. coli*): reduces CS * *Klebsiella* sp. mastitis: under dev.

Question 43

What are the 6 keys to a mastitis control program?

Answer 43

1. Proper milking management 2. Environmental control 3. Dry cow therapy 4. Milking machine maintenance 5. Treatment protocols 6. Vaccination