Thursday, June 22, 2017

Automatic Calf Feeders - Bacteria Control Challenges

During a study including 38 farms over 18 months the research team assessed the bacteria contamination levels of milk consumed from automatic calf feeders. Each farm was sampled from both the automated feeder mixing tank (mixing tank) and the point of connection between the flexible dispensing tube and the nipple (tube end). 

Bacteria counts reported:


Source of Sample           Value                         Standard Plate Count      Coliform Count
                                                                                   (cfu/ml)                         (cfu/ml)
1. Mixer tank                  Median                              166,916                             336
                                        Range - lowest                         125                                 0
                                                   - highest              59,396,100               25,621,330

2. Tube end                     Median                            2,566,867                       10,430 
                                        Range - lowest                       6,668                              45
                                                   - highest              82,825,000               28,517,000

Using the thresholds of 10,000 cfu/ml coliforms and 100,000cfu/ml standard plate count (SPC) they reported:

Source of Sample                 SPC>100,000            Coliform Count >10,000
                                         (% farms above)            (% farms above)
1. Mixer tank                          32                                   15
2. Tube end                             68                                   28

What are the messages for me?

First, RANGE values for both SPC and coliforms demonstrate that while it is possible to deliver clean food to autofeeder calves it clearly is possible to screw up badly - very, very badly - 82,000,000 plus cfu/ml!

Second, when I culture "as-fed" milk samples for my clients we use these upper thresholds to determine if on-farm cleaning and handling procedures are being met (usually fed in bottles or buckets manually):
                              SPC     <10,000cfu/ml
                       Coliforms   <1,000cfu/ml

If my clients' samples came back looking like those from theses 38 farms I would be all over their cases - all cleaning procedures would be examined closely for protocol compliance slip-ups. Weekly samples would be taken all along the handling stream to isolate possible points of inoculation and growth.

Third, in terms of calf care and calf health, I consider feeding milk with these levels of bacteria contamination irresponsible and perhaps bordering on animal abuse.

As an aside, one time when we were monitoring bacteria levels with automatic feeders for a client we discovered that the warm-water holding reservoir was serving as a bacterial incubator because the feeders were being used most of the time for whole milk. Contaminated water was leaking into each batch of milk as it was heated. By changing the settings to use 10g of powder in every mixer bowl the reservoir problem was eliminated. So, I have to admit that issues beyond cleaning can sometimes contribute to high bacteria counts. 

References:
Jorgensen, M.W. and Others, "Factors associated with dairy calf health in automated feeding systems in the Upper Midwest United States." Journal of Dairy Science 100:5675-5686 June 2017. Dietrich, M. and Others, " Factors associated with aerobic plate count, coliform count, and log reduction of bacteria in automated calf feeders." Journal of Dairy Science, 93, Suppl. 2, p214 #86.

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