FA Med Q3, III
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. What would you like to do?
do all quarters produce milk equally?
caudal 2 quarters produce 60%
where is milk produced? what happens when mammary gland is stimulated?
- alveolar cells produce milk
- release of oxytocin - contraction of myoepithelial cells and sphincter relaxes
what hormone inhibits oxytocin release?
catecholemines (epinephrine) - don't startle the cows at milking time
how much blood supply is required to produce one gallon of milk?
500 gallons of blood
what are the major hormones needed for milk production?
- ACTH and prolactin
- (also insulin, growth hormone, TSH, PTH)
at time of calving are ACTH, prolactin, and progesterone high or low? what do these levels promote formation of?
- hi: ACTH, prolactin
- low: progesterone
- conversion of alpha-lactalbumin to *lactose*
what are three diseases you should look for when examining the utter, as they do not have treatments, only prevention? which is contagious?
- pseudocowpox - scabs
- herpes mammilitis - crusts/open sores
- bovine papillomavirus - contagious
how many somatic cells (WBCs) are in a healthy utter?
what cell greatly increases when fighting bacterial infection in utter? does this cell work better or worse than when fighting bacteria in the blood?
- neutrophils can get into the millions
- less effective in milk - no available glucose and fat/casein coats them
Lactoferrins are an important defense against which pathogens? how do they work?
- coliforms (kleibsiella and e.coli)
- -bind iron so bacteria can't use it for growth
why is post-parturiant cow more likely to develop mastitis?
- immunocompromised (high cortisol for delivery impairs immune)
- oxytocin leaves sphincter slightly open
- laying in dirty environment
what happens in the gland when bacteria and SCC overwhelm it?
milk clot/plug with debris can lead to atrophy of alveolus
How does a peracute mastitis differ from acute mastitis?
- both have sudden onset of signs
- peracute - systemic illness precedes abnormal milk
- acute - less severe systemic illness
what is the difference between subacute, subclinical and chronic mastitis?
- subacute - no systemic illness; only small clots/mild inflammation
- subclinical - inflamed mammary w/NO systemic illness signs
- chronic - can be subclinical for months w/flare ups
of all forms of mastitis, which is most common?
what are you looking for when using a strip cup to evaluate each quarter? will this test show anything abnormal for subclinical mastitis?
- macroscopic evaluation for color and consistency (flakes, gargot/clumps, watery, bloody)
- NO changes if cow is subclinical
what leukocytes are present in the milk in health? in illness?
- health = macrophages
- illness = neutrophils
will somatic cell counts reveal subclinical cases?
- what are the indirect ways to do SCC?
- indirect: estimated SCC counts
- -California mastitis test for individuals
- -Wisconsin Mastitis Test for bulk samples
what are direct ways to do SCC?
- exact counts:
- -direct microscopic
When California Mastitis Test is performed, alkyl arylsulfonate and bromcresol purple are added to the milk. What does this cause to happen?
- lysis of cells and polymerizes DNA - forms gel
- (more gel = more nucleated cells)
What is the milk to reagent ratio for CMT? how long do you wait to determine results?
- 1:1 (don't fill cup more than half full of milk)
- read within 30sec
if CMT gets score of trace, about how many cells are present? what if its score of 1 (distinct slime)?
what will CMT cup look like if it gets a score of 2 vs. 3?
- 2: distinct gel (2.7x10^6)
- 3: convex gel (8.1 x10^6)
what is the maximum allowable SCC in milk in the US?
what are some causes of false positive results on CMT?
- *Increased WBCs* - colostrum or trauma to udder
- *less fluid but same # WBCs* - late lactation/dry off or illness that decr. production
- *higher # than rest of milk* - first strip and residual milk
Culture samples should be collected before starting treatment. Who should have cultures run?
new to the herd and those w/incr WBC (clinical and subclinical)
when cleaning teats for culture collection, which teat should you prepare first? What order should you collect the sample?
- clean far then near (don't contaminate what you just cleaned!)
- collect near then far (don't contaminate clean teats)
If the sample can't be run within 48 hours, should you throw it away and start over?
no, just freeze it until it can be run
when is it a good idea to submit separate quarter samples for culture?
- best results but $$$
- suspect Staph aureus
- only one quarter positive on CMT
Composite samples collect from all 4 quarters in one sterile vile and is more economical but what is the draw back?
more environmental contamination
if bulk sample results come back positive for coliforms or strep, what could this mean other than mastitis?
- problem with pre milking procedure
- (live at teat ends - access bulk tank but not in mammary)
what test is recommended for the DHIA (dairy herd improvement association)?
direct electronic methods for specific SCC counts
are 90% of mastitis cases from contagious cow-cow transmission or acquired from the environment?
contagious causes like staph/strep
what are common mastitis causing organisms found in the milk and lining epithelial cells?
- strep. agalactiea, coagulase negative
- Staph. spp. and strep. dysgalactiae
what are common mastitis causing organisms found in the deep tissue of the gland?
- staph aureus
- strep uberis
- A. pyogenes
what are common mastitis causing organisms found in the gland as well as other body systems?
coliforms like e. coli and kleibsiella
what is a nonpathogenic contagious organism associated with the udder?
what are the "big two" contagious pathogens of mastitis?
- staph. aureus
- strep agalactia
what kind of mastitis does staph aureus cause (peracute/acute/chronic/subclinical)?
- most cases subclinical - major loss in production
- can lead to gangrene
How effective is the immune system at attacking staph aureus?
- evades neutrophil phagocytosis
- capsule - resists opsonization
- leukotoxin - kills phagocytes
what makes staph aureus mastitis difficult to treat?
- B-lactamase producer so no penicillins
- deep tissues affected
- gangrenous form - thrombosis - blood tinged serum
how will cow present with clinical v. subclinical staph aureus mastitis? what about strip cup? CMT?
- subclinical: cow normal, normal strip, positive CMT
- clinical: febrile/anorexic, abnormal strip, positive CMT
how will cow present with chronic staph aureus mastitis? strip cup?
- palpable fibrosis in udder
- abnormal milk if flare-up or can be subclinical/normal strip cup
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