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On-Farm Milk Culture Training Workshop

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Christina Petersson-Wolfe joins us to discuss on-farm milk culturing from deciding which cows to test to using results. Learn about collecting and plating samples, identifying types of pathogens, and treatment recommendations for different types of infection.

See the full presentation at https://www.youtube.com/watch?v=r7P_53zeQbg

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On-Farm Milk Culture Training Workshop

  1. 1. On-Farm Milk Culture Training Workshop Christina Petersson-Wolfe Department of Dairy Science Virginia Tech
  2. 2. The right drug for the right bug • Different bugs respond to different treatments • Antibiotic sensitivities previously relied on • Culture based therapy is the best option
  3. 3. Waiting 24 hours to treat? • No difference in long-term outcomes – Recurrence – Milk production – Risk for culling – SCS • Reduced antimicrobial usage by 50% • No change in cure rates
  4. 4. Who to culture? • Depends on the goals of the farm – Clinical cases – always – High SCC cows – Cows going dry – Fresh cows – Heifers prior to calving
  5. 5. On-farm Culture • Various culture systems marketed • Minnesota Bi-Plate and Tri-Plate most widely used – User guides printed in both English and Spanish • Low initial input cost – Incubator = $55 • Hova-Bator (egg incubator) – Supplies = ~$2-3 per sample
  6. 6. • Three different selective media – Factor agar (proprietary ingredients) – G+ only – MTKT agar – Streptococcus spp. only – MacConkey agar – G- only On-farm Culture
  7. 7. • Aseptically collect sample from clinical quarter • Use sterile cotton swab to streak on all 3 media dipping back in sample between • Incubate overnight and observe growth at 24 hours • Determine treatment On-farm Culture
  8. 8. Plating on Tri-plates 1. Mix milk samples by inverting several times 2. Using aseptic technique uncap the tube of milk 3. Take a clean loop or swab and dip it into the tube 4. Starting with Factor Agar, streak milk sample from outside-in following streak lines shown above 5. Repeat steps 1-3 and streak on Modified TKT agar 6. Repeat steps 1-3 and streak on MacConkey Agar 7. Cap milk sample and discard loop/swab 8. Incubate milk sample for 24 h at 37C 1. Factor Agar (Bright red) 2. Modified TKT (Dark red) 3. MacConkey Agar (light pink)
  9. 9. • Gram positive growth = treatment – Can determine Strep from other G+ and treat differently if vet recommended • < Gram negative growth = no treatment • > Gram negative growth = systemic treatment On-farm Culture
  10. 10. • Strep spp. • possible Staph spp. + + + On-farm Culture
  11. 11. • Identifying Staph aureus + Factor agar Staph aureus On-farm Culture
  12. 12. On-farm culture results Streak in order of: Bright red (Factor Agar) Dark red (MTKT) Light pink (MacConkey) Factor Agar (red) Gram pos growth Staph/Strep MTKT (Dark red) Grows Strep only MacConkey (pink) Gram neg growth E. coli/Klebsiella Result + + - Strep or mixed Staph/Strep + - - Staph (check hemolysis) - + - Strep - - + Gram-negative (E. coli, Klebsiella, etc…) + + + Contaminated
  13. 13. What do no growths mean? • Big source of frustration for producers • 30-50% of samples will result in no growth • Sometimes… – The cow’s immune system handled it – The bacteria aren’t shedding – You just didn’t catch the bug • If she is a repeat offender, resample
  14. 14. CNS versus Staph aureus • Tri-plate alone doesn’t give you a definitive answer • Check hemolysis patterns • Can do coagulase test if wanted – Positive (+) = Staph aureus – Negative (-) = CNS
  15. 15. About the bugs… Classification Bacteria Source Control Staph CNS & Staph. hyicus Skin flora, subclinical Post dip, DCT Staph. aureus Infected udders Segregation, milking hygiene, treatment, cull
  16. 16. About the bugs… Classification Bacteria Source Control Strep Env. strep & Enterococcus Environment Pre & post dip DCT and clean environment Strep. dys. Environment and infected udders Pre & post dip DCT and clean environment
  17. 17. About the bugs… Classification Bacteria Source Control Coliform E. coli Bedding, manure, soil Sand, clean & dry, pre dip, J5 Klebsiella Organic bedding Avoid sawdust & recycled manure, clean & dry Enterobacter Bedding, manure, soil Sand, clean & dry, pre dip, J5 Serratia Soil and plants Sand, clean & dry, pre dip, J5, no chlorhex. dip
  18. 18. Classification Bacteria Source Control Other C. bovis & other Coryneforms Infected udders, teat canal Post dip, DCT Yeast & Mold Soil, plants, water, cannulas, dirty infusions Scrub teat ends well prior to infusion Prototheca Soil, plants, water, manure, contagious Segregate & cull cow, eliminate water areas Bacillus spp. Soil, water, wounds, dirty infusion Scrub teat ends well prior to infusion T. pyogenes (formerly A. pyogenes) Teat injuries, infections Fly control, killing affected quarter About the bugs…
  19. 19. Classification Bacteria Treatment Staph CNS & Staph hyicus Treat clinicals – Today Don’t treat subclinicals unless SCC DCT Staph. aureus Early lactation heifers – 5-7d Pirsue Treat 2nd, 3rd lactation first time cases Chronics unresponsive Occasional cure with DCT Cull chronics when feasible Culture fresh cows to monitor and treat How to treat…
  20. 20. Why are they hard to treat?
  21. 21. How to treat… Classification Bacteria Treatment Strep Env. strep. & Enterococcus 4-5 d penicillin - (3.5cc/100 lbs BW systemically) Good cure with DCT Strep. dys. Label treatment with Today Good cure with DCT
  22. 22. Classification Bacteria Treatment Coliform E. coli Local: No IMM treatment, supportive therapy if necessary, infection typically clears in < 10 days Systemic: IV Fluids (2-3L saline), followed with oral, Banamine (20cc on sick big Holsteins), 60-80 cc Oxytet IV Klebsiella Enterobacter Serratia Resistant to antibiotics, chronic infections, often result in cull 180-300 ml hypertonic saline infused may help Extra label use - Spectinomycin How to treat…
  23. 23. How to treat… Classification Bacteria Treatment Other C. bovis & Coryneform No lactating treatment, DCT works Yeast & mold No antibiotic treatment, many spontaneously cure Prototheca Antibiotics do not work - cull Bacillus spp. Can cause similar signs as coliform infections. Tx as gram-positive – Today or Pirsue T. pyogenes (formerly A. pyogenes) Kill the quarter or removal from the herd
  24. 24. Residues • Follow label directions – Treatment regiment – Withholding time • Test for antibiotic residue
  25. 25. Want more info? • Contact me – milk@vt.edu or 540-231-4767

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