L4: Bovine Mastitis and Prod. Quality Milk (Donovan) Flashcards
fx of alveoli in mammary gland
- milk synthesis
- oxytocin responsive smooth m.
1st and most important line of defense against invasion by pathogenic bact.
teat canal
-lined by smooth m, squamous epithelium, and thick layer of keratin that is bacteriostatic
inflamm. char. by 5 signs
heat pain redness swelling disturbed function
clinical forms of mastitis
peracute (most severe) acute subacute (most common CLINICAL form) subclinical (most common form!) chronic
peracute mastitis
- most severe form
- CS in 4-12hr
- local AND systemic sign (fever, anorexia, dehydration, depression, m. tremor, +/- d)
- death common
acute mastitis
- 5 signs of inflamm. present
- usually accompanied by mild depression, fever
subacute mastitis
- subdued inflamm. signs
- not systemic
- most common CLINICAL form
subclinical mastitis
- inflamm. w/o gross signs
- testing needed to detect
- most common form of mastitis!
chronic mastitis
- inflamm. over wks/mos or from 1 lactation to the next
- continuous or periodic flare-ups that prod. acute or subacute CS
major primary udder pathogens causing mastitis
S. aures
Strep agalactiae
Mycoplasma sp.
Strep dysgalactia
major env. pathogens causing mastitis
strep uberis
strep dysgalactia
minor env. pathogens causing mastitis
Staph coag neg
coliforms
A. pyogenes
pathogenesis of Strep agalactiae
- does NOT actively invade tissue
- irritant accumulates and intensifies inflamm. rxn
- replacement of secretory tissue w/ scar tissue
- atrophy of mammary gland
- dec. milk prod. with very inc. bacterial/SC counts in milk
control of strep ag***
- can be eradicated!
- post-dipping
- dry cow therapy
- ID infected cows and treat (Blitz treatment
- Blitx treatment (abx during lactation) –> 90% reduction in 1/4 infection rate***
T/F: Blitz tx ONLY works for Strep ag mastitis***
T
S. aureus
- causes contagious mastitis**
- usually subclinical and chronic
- micro-abscess w/n gland
- peracute form –> gangrene
- reservoirs = milk, teat skin
- causes mod. inc. in SCC
path. of S. aureus
- penetrates into tissue
- prod. toxins (ie. alpha hemolysin assoc. with gangrenous mastitis)
- produces penicillinase
- abx have hard time penetrating CT of abscesses
mycoplasma sp.
- causes contagious mastitis**
- pneumonia, otitis, arthritis in calves
- often subclinical
- coffee-grounds appearance to milk
- non-responsive to abx
- periodic shedding
- primarily a RESPIRATORY pathogen
strep uberis and dysgalactia
- ENVIRONMENTAL
- NOT susceptible to eradication
- opportunistic
- uberis –> acute and chronic mastitis indistinguishable from Strep ag
- dysgalactia –> infections usually follow teat injury and enhanced by teat lesions
95% rule
95% of all mastitis due to: strep ag staph aureus strep uberis strep dysgalactia coliforms
coliforms
- ENVIRONMENTAL
- opportunistic
- low numbers of bact. shed in milk
- causes peracute to acute mastitis
- herds with low SCC may be at inc. risk
coliform mastitis char. by
- sudden marked swelling of quarter
- fever, m. tremor, rumen stasis, dehydration +/- d
- udder secretion serous –> thick with fibrin/leukocytes
pathogenesis of coliforms
- non-invasive
- endotoxins** released from bacteria when destroyed by immune system
- recovery usually rapid
- usually not chronic
goal % clinical cases
<3% of milking cows with clinical mastitis/month
California mastitis test
indirect measure of somatic cells in milk
- screens for subclinical mastitis
- not good for differentiating b/w infected and non-infected cows
relationship b/w SCC and milk prod. loss
linear (inc. SCC –> inc. milk loss)
components of mastitis control program
Proper milking management env. control dry cow therapy milking machine maintenance treatment protocols vaccination
pre-milking management
- clean and dry teats
- preDIP (controls env. mastitis)
- STRIP
- WIPE
- HANG
milking management
- avoid linear slips (can contribute to inc. coliform units)
- milk cows with DRY teats only!!
- readjust machine if necessary
- don’t overmilk
post-milking management
- make sure cow is milked out
- dip all 4 teats on all cows
- send cow to feedbunk with fresh feed and water
when does highest incidence of infection occur?
drying off period (2nd most common = after calving)
Dry Cow Therapy
-all functional quarters of all cows should be treated w/ long-acting intramammary abx at time of drying off, esp. for control of strep ag, staph aureus
T/F: culling is a form of tx
T
recommended and non-recommended vax
rec: E. coli
not rec: Staph aureus, Mycoplasma bovis
