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3. Food Animal > Udder 1 > Flashcards

Udder 1 Flashcards

1
Q

what is mastitis? generally associated with what?

A
  • = inflammation of the mammary gland
  • Practically, associated with bacterial infection
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2
Q

how common is mastitis?

A
  • Typically, 1 cow in 5 has >= 1 case of clinical mastitis per lactation
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3
Q

economic and medical significance of mastitis

A
  • Often the most economically important disease on a dairy farm (~ $120 - $300 per case)
    > ~ $5000 – $12,000 per 100 cows per year
  • The #1 reason for use of antibiotics in dairy cows
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4
Q

healthy teat end should have what texture?

A

smooth - less hospitable for bacteria

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5
Q

are mastitis causing agents common?

A

Many mastitis-causing organisms are common on the cow and in her environment

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6
Q

challenges for the cow for mounting an immune response to mastitis

A
  • Blood-milk barrier limits the immune arsenal
  • Milk is a difficult place for immune cells and antibodies to function
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7
Q

how and why does the conductivity of milk change with mastitis? what other related changes occur?

A
  • mastitis milk is more conductive because there are more electrolytes (Na, K, Cl) present
    >inflammation causes increased vascular permeability / increased permeability of blood milk barrier
    > this is to let antibodies through
  • mastitis milk will look more like serum > better medium for immune system
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8
Q

notable changes in albumin, lactoferrin (what is this?) sodium, and chlorine in mastitis milk vs normal?

A

albumin, lactoferrin, sodium, chlorine all increased in mastitis milk
- lactoferrin is a “natural antibioitic” > binds to iron so bacteria cannot use it

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8
Q

mammary immune response - cellular and humoral; what do they include?

A

Cellular response:
* Primarily neutrophils

Humoral response:
* innate
> Complement system (opsonins)
> lactoferrin
> enzymes
> resident (e.g. LPS (endotoxin) receptors)
* acquired
> immunoglobulins (vaccination)
> memory

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9
Q

cells in milk; normla vs mastitis

A

Total cells:
-normal: < 100,000
-mastitis: > > 250,000

WBC:
-normal: >85%
-mastitis: >99%, due to massive increase in neutrophils

Epithelial cells:
- normal: <15%
- mastitis: <1%

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10
Q

new mastitis infections generally happen when?

A

New infections happen around milking
* Both contagious and environmental pathogens

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11
Q

general pronciples for mastitis prevention:

A
  • Reduce bacterial challenge at the teat end
    > Clean stalls, bedding, alleys
    > Teat cleaning and prep at milking
    > Strategic treatment of mastitis to reduce transmission
    > = Prevention of intra-mammary infection (IMI)
  • Support immune function
    > Provide cow comfort and bunk access to encourage feed intake
    > Provide nutrients that fuel the immune system (e.g. vitamin E, Se)
    > = Preventing IMI from developing into clinical mastitis
  • Reduce the severity of cases that do occur
  • Also note that new infections happen around milking
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12
Q

difference between clinical and subclinical mastitis

A

Mastitis (Intramammary infection (IMI)), leads to:
-clinical = visibly abnormal milk
> milk, moderate, or severe
-subclinical = visibly normal milk but measurable infection or inflammation

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13
Q

major (based on pathogenic and economic impact) mastitis pathogens and their basic classifications

A

CONTAGIOUS:
* Staphylococcus aureus
*Streptococcus agalactiae
*Mycoplamsa spp (mostly M. bovis)

ENVIRONMENTAL:
*Coliforms:
-Escherichia coli
-Klebsiella spp.
*Strep. uberis

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14
Q

minor (based on pathogenic and economic impact) mastitis pathogens

A

*Coagulase- negative Staphylococci (i.e. other than S. aureus)
*Corynebacterium bovis

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15
Q

Clinical mastitis means what? what are the levels?

A

= visibly abnormal milk
* Mild = flakes, clots, or watery milk; normal quarter
* Moderate = abnormal milk + swollen or hard quarter
* Severe = abnormal milk, quarter and systemically ill cow

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16
Q

does mastitis severity depend on the agent?

A
  • Severity is not well correlated with the etiologic agent
17
Q

how much production is generally lost due to a clinical case of mastitis?

A

Typically 3 to 10 days of production lost (non-saleable) per clinical case

18
Q

costs associated with a mastitis case

A

Costs include:
* milk discard
* treatment cost
* labour
* risk of drug residues
* possible risk of infection to other cows

19
Q

how common is clinical mastitis per lactation? what is the case rate, typically? what is our goal?

A
  • Typically ~ 20% (0 to 60%) of cows have >= 1 case of clinical mastitis per lactation
  • Typical clinical case rate ~ 3 to 6 % of milking cows per month
  • With optimal management, the goal is < 2% clinical case rate per month
20
Q

on canadian dairy farms: what is the 25%, 50%, and 75% percentile number of CM cases per 100 cow years? what is our goal?

A

-25% of famrs have <15 cases/100 cow years
-50% of farms have <26 cases/100 cow years

-The worst 25% have >39 cases/100 cow years

> Goal: 20 cases 100/cow-years

21
Q

on canadian dairy farms, what proportion of CM cases are milkd, moderate, severe?

A

Severity Score:
Mild (abnormal milk) 50%
Moderate (swollen quarter) 38%
Severe (systemic signs) 12%

22
Q

when we recover pathogens from mastitis cases, we cannot grow anything 19.1% of the time. Why?

A
  • often, by the time we see abnormal milk clots, the cow is already ‘winning’ (often the case with coliforms)
23
Q

top 3 pathogens identified in clinical mastitis cases

A

-E. coli: 15.9%
-S. aureus: 15%
-other strep spp.: 12.6%

24
Q

Common seasonal pattern of clinical mastitis in Ontario:

A
  • late summer, fall
    > ramps up in july, max cases sept, oct, nov
    >decreases in december and then low until june
25
Q

Stage of lactation when clinical mastitis commonly occurs? explanation?

A

far more common at the beginning of lactation, <20 days in milk
- steadily becomes less common as DIM increases, very few cases by 340DIM

  • immune system is not as good in early lactation, and there are many other metabolic demands on the cow
26
Q

Fresh period is a high-risk time for mastitis. why?

A
  • Substantial reduction in several elements of immune function
  • Re-opening of teats
  • +/- Packs and stalls that are not as clean as they should be
27
Q

what is subclinical mastitis? how do we detect it and how often do we look?

A
  • Inflammation without visibly abnormal milk
  • Detected by somatic cell count (SCC)
  • Somatic cells = immune cells (neutrophils) in milk
  • Routinely measured
    > Every 1-2 days in bulk milk – all herds
    > Monthly on individual cows in herds on DHI
28
Q

impact of subclinical mastitis on milk and cheese

A
  • Reduced milk production
  • Reduced cheese yield and quality
  • Reduced milk shelf-life
29
Q

SCC is associated with:

A

SCC is associated with the probability of bacterial infection

30
Q

what is the SCC linear score? what is the relationship with milk loss?

A

Linear score (LS) is the log(SCC)
* [log2(SCC) + 3]
* Linear relationship with milk loss
* Reduced skewing of group average SCC

31
Q

SCC score that is typical cut-point for estimated infection

A

SCC 200,000 cells/ml = LS 4

32
Q

SCC score that is regulatory limit in bulk tank milk?

A

Regulatory limit in bulk tank milk = SCC <400,000
* Fines and eventual shut-off

33
Q

range of SCC scores for non-infected

A

0-2000, with a peak around ~100
(recall 200 is the cutoff for estimating infection, so some cows are above this but not infected)

34
Q

SCC range for infected cows

A

~50 - 9000, with a peak just under 2000
(so some infected cows will be below 200 even though they are infected)

35
Q

what is the California Mastitis Test? how does it work and what does it tell us?

A
  • A simple cow-side qualitative SCC
  • Detergent in solution reacts with DNA in neutrophils to form gel
  • Cheap, fast, and provides information at the quarter level
36
Q

Milk loss due to subclinical mastitis - how does it change as the linear SCC score increases (for >= 2nd lactation cows)

A

losses start at LS = 2, and increase linearly
> by LS = 9, you are losing over 1200ks per lactation
> this is milk that is never produced due to mammary inflammation, not due to discard

37
Q

CMT starts to identify mastitis at what SCC?

A

-trace at SCC = 400
- at SCC = 800, should be able to visualize easily
>at this point, milk production will already be quite decreased, as cell count can already be quite high once we see the difference

38
Q

Typical pattern of SCC following a case of clinical (coliform) mastitis

A
  • SCC low until about 8/9 days post infection, then skyrockets, up to 8000
    >then gradual decline and back to normal at 25-30 days
    >very fast increase, slower decrease
39
Q

control of mastitis: general techniques

A
  • Milking hygiene and technique
    > Clean dry teats
    > Good milk let-down,
    rapid milk-out
  • Clean environment
  • Cow comfort
  • Dry cow therapy
40
Q

control of mastitis: pathogen specific techniques

A
  • Antibiotic treatment protocols for clinical cases
  • Vaccination
  • Selective culling
41
Q

diagnosis of mastitis: methods, pros and cons

A
  • Etiologic diagnosis may be important for treatment decisions, prognosis, and specific preventive measures
  • Definitive diagnosis based on bacteriologic culture
    > Takes at least 12-24 h, up to 3-4 days
    > Speciation after culture now done by MALDI-TOF -> Faster and more specific than chemical tests
  • PCR tests now available
    > Relevant for clearly cow-source (i.e. “contagious”) pathogens

3. Food Animal (22 decks)

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