Saturday, January 28, 2017

Stopping Salmonella from Infecting the Next Calf

We frequently find that there are reservoirs of the Salmonella pathogen on dairy farms.  As long as immunity is high the animals do not show symptoms of being clinically ill (Salmonellosis).

With the changes that accompany the introduction of the Veterinary Feed Directive (VFD) we have some dairies that have stopped continuous feeding of antibiotics to young calves (usually less than 4 weeks but maybe as long as 8 weeks). 

On one  hand, for dairies where pathogen exposure is well controlled (for example, low bacteria counts in colostrum, calves moved from calving pens promptly and reliably after birth, feeding equipment effectively cleaned) taking away this "band-aid" has little effect.

On the other hand, if the farm's management practices have be skating at the very edge of containing clinical infections taking away the continuous feeding of antibiotics in the milk for preweaned calved may be all that is needed for subclinical infections to become clinical. 

Also, if there is significant exposure to Salmonella bacteria routinely in the calving pens and calf housing any event that causes even a little weakness in immunity among either cows at calving or young calves may be all that sets off a Salmonella event among calves. So, beyond treating sick calves, what to do when one or more calves are diagnosed with Salmonellosis?

Stopping Salmonlla from Infecting the Next Calf

1. Review colostrum management
  • Using blood from 10-12 calves (draw between 2 and 7 days of age) assess the effectiveness of creating passive transfer of immunity among calves. Click HERE for a guide to measuring passive transfer of immunity. When using blood serum total protein method, our goal is to have 90% at 5.0 and greater, 80% at 5.5 and greater.
  • Using 5 or more colostrum samples (collected from nipple or tube feeder just before feeding the calf) have laboratory cultures run to assess the level of bacteria in "as-fed" colostrum. Click HERE for a guide on sample collection. Our goal is to have less than 5,000cfu coliforms and less than 50,000cfu total plate count. 
2. Review calving pen management
  • Set the goal of having dry clean  bedding for all calves
  • Set a goal for promptly removing calves from the calving pen(s) to a clean, dry environment.
  • For any high risk dam suspected of being a Salmonella carrier, isolate her, remove the calf immediately after calving and do not feed her colostrum to any calf. 
3. Sanitize, sanitize, sanitize
  • Review washing procedures for calving equipment, colostrum handling equipment and calf feeding equipment. Click HERE for an equipment washing checklist.
  • Review ways in which caregivers may be spreading Salmonella from place to place and from calf to calf. 

[Veterinary Feed Directive (VFD) is a US based government program designed to place all feed-related antibiotic use under the direct supervision of the farm's veterinarian. A directive containing a description of the animals, the antibiotic to be used and the dose and duration of use must be written before the farm can purchase the product from a supplier.]

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