lecture 11

• how to control opportunistic pathogens?

  teat skin/end integrity and using post-milking teat disinfectant
• environmental pathogens from environment: klebsiella spp, prototheca spp, proteus spp, and pseudomonas spp
• environmental pathogens from fecal shedding: e. coli, strep spp, klebsiella spp, and serratia spp
• environmental pathogen, streptococci: gram positive coccus; includes strep uberis, strep dysgalactiae, strep equinus, and strep canis; short duration, infection lasts less than 30 days; 40% spontaneously cure
• environmental pathogen, enterococcus spp: gram positive, includes enterococcus faecalis and faecium
• streptococcus spp is salt intolerant; enterococcus spp is salt tolerant and antibiotic resistant
• coliforms: gram negative rods; ferment lactose to produce acid or gas, non-spore forming; includes e coli, klebsiella spp, and enterobacter spp; cause clinical mastitis and decreases milk production
• coliforms are easily identifiable by sour smell and slimy appearance
• other gram-neg pathogens: serratia spp, pseudomonas spp, proteus spp, salmonella spp, and pasteurella spp; not as prevalent and don't cause mastitis often
• serratia spp: gram neg, resistant to chlorohexidine teat disinfectants, poor response to antibiotics, produce chronic infections, occur more often during dry period
• pseudomonas spp: gram neg, affinity for water (like to reside in standing water and water hoses in milk parlor), poor response to antibiotics, causes chronic infections
• prototheca: not gram neg, is an algae (not bacteria), affinity for water or moisture (dirty bedding, alleyways, pasture systems), does not respond to antibiotics bc no cell wall
• big players of environmental pathogens: streptococcus uberis, e coli, and klebsiella pneumoniae; control beings in the living environment of the cow
• environmental mastitis pathogens are the #1 cause of clinical mastitis; main issue for well managed herds
• percent of cases: 29.7% coliforms, 25.4% environmental strep, 27.2% bacteriology neg (inflammation but no bact present), 17.6% other
• down stream consequences of environmental mastitis: limited to moderate affect on BT SCC (bc infection is known/clinical, won't be added to bulk tank); cows can die; low prevalence in herds; incidence can be high (bc infections are short), about 45 cases per 100 cow lactations
• incidence is the number of new cases at a specific time period (rate)
• prevalence is number of existing cases
• longer thick lines = contagious; shorter thick lines = environmental
• environmental mastitis pathogens are not well controlled by postmilking teat disinfectant or DCT (blanket or selective); yet, dry period is critically important bc IMI increases right after drying off (greatest risk)
• a large proportion of clinical mastitis cases are a result of IMI acquired during the dry period; IMI remain subclinical until the "stars align"
• 2/3 of clinical mastitis cases occur within the first 1-2 months of lactation
• control of environmental pathogens is key: limit exposure and number on teat end
• sources of environmental pathogens: milking parlor, soiled equipment, living environment (alleyways, bedding, pasture)
• limit number of environmental pathogens before milking: need to clean teats and remove bacteria to reduce bacteria counts in milk and reduce bacteria that could cause IMI
• environmental IMI: anything in manure, contaminated water and bedding
• wet = NOT CLEAN
• why must teats be dry?

  water goes into milk; contaminated water can introduce pathogens and facilitate movement of bacteria already present on skin
• squawking milking units: unit not attached properly or one quarter milks faster than others; causes air to move from parlor into cluster; bacteria can be flushed into another teat
• vacuum slip: when milking units are attached, near end of milking, increases IMI chances
• proper premilking procedure: fore-strip and remove large debris (initiate oxytocin letdown and check for clinical mastitis), apply premilking teat disinfectant (dip or spray, at least 30 s), remove disinfectant with single use towel, attach milk unit, remove milk unit, apply postmilking teat disinfectant
• environmental mastitis is significantly decreased with use of premilking teat disinfectant
• milking parlor plays a big role in pathogen presence, but the cow should only spend a couple hours in the parlor (mostly in environment)
• environment: includes bedding, alleyways, and pasture; more than 20 hrs a day in environment
• bedding types: crushed limestone, sand (new or recycled), sawdust (fresh or dried), manure solids, straw, or other waste feedstuffs (corn cobbs)
• what bedding best fulfills needs?

  depends on cost, cow comfort, ability, work on farm, and mastitis risk (organic vs non, moisture)
• non-organic bedding: harbor less bacteria (no food or moisture for bact), sand and limestone predominate
• organic beddings: have substrate to support bacterial growth, retain water, neutralize disinfectants, increase surface area, provide adherence; coliforms and environmental streps thrive
• managing sand: sand bed must be deep for comfort, requires daily cleaning of dirty stall curbs, dry sand should be added as needed, as moisture and organic mater increase so do bacteria counts
• managing organics: dry matter percentage, will grow bacteria faster than nonorganics, must be cleaned daily, strep spp love straw, klebsiella love sawdust, compost is good but limited in some countries