How to Add Bacteria to Milk Replacer
Seriously, I do not have clients that have the goal of adding bacteria to milk replacer. However, I do have clients whose milk replacer when consumed contains many bacteria.
Question? How do the bacteria get into the milk replacer?
A case study.
Milk replacer is mixed in 55 gallon plastic drums. Then it is pumped through a drag hose to deliver it to the calves. In order to get to the calf the milk replacer goes through an intake hose going to a pump. It goes through the pump through a long plastic hose that is dragged from pen to pen. Squeeze a "gas-pump" type nozzle and out comes the milk replacer. The calf drinks from a nipple bucket.
Presto, like magic, the samples from this client last week had these bacteria counts!
Sample Site Coliform Total
Mixing barrel 300 2,300
From feeding nozzle 1,500 5,500
From nipple 8,500 23,700
Clearly, it is not difficult to add bacteria to milk replacer.
Just for reference, in my consulting work I use upper thresholds of 1,000 cfu/ml coliforms and 5,000 cfu/ml total plate count as goals for feeding either milk or milk replacer in order to achieve reasonably cost effective levels of calf scours.
Manually cleaning a big open barrel is not difficult - 5 gallons of water, detergent and a brush. Seems to work reasonably well.
Cleaning a long plastic drag hose and the plastic nozzle - not so easy - have to pump fluids through the intake hose, pump, drag hose and nozzle. Maintaining wash solution temperature above 120F (49C) is a challenge - especially when feeding in a cold barn in February in New York State.
Cleaning nipple buckets and nipples appears to be the big challenge - note the 10 fold increase in total bacteria from the barrel to what went into the calves.
How to reduce contamination levels in the future?
1. Quick and dirty solution is to use a strong chlorine rinse (500ppm) just before using any of the feeding equipment - especially the nipple buckets.
2. Not so quick solution - current wash protocol for nipple buckets is to wash in 110F detergent solution with a quick swipe using a stainless steel scrubber. Revised wash protocol I am suggesting is to rinse with lukewarm water before washing (no rinse currently), wash in detergent solution never less than 120F using a stiff bristle brush.
Even with the improved wash procedure I still lean toward the pre-use sanitizing rinse.
Maybe in March I will have another set of samples with fewer bacteria.