Disinfectants 101

You may remember the saying, "A horse is a horse, of course, of course." But Mr. Ed was not talking about disinfectants.

You may be quite surprised to learn that there are many considerations when it comes to selecting a disinfectant for your dairy.

First, we need a quick vocabulary lesson.

Chemical agents work by either killing or slowing an organism's growth. Agents that kill microorganisms have the suffix –cide, while those that slow growth or prevent multiplication use –static.

Choose the right tool

In the dairy industry, we are very familiar with detergents and sanitizers as they are used in the milking parlor, but the terms are not interchangeable.

Detergents are for the removal of soil and organic material. Some disinfectants can have detergent properties.

Sanitizers are used to reduce numbers of microbial contamination. They are often a combination of a detergent and disinfectant.

Disinfectants vary in their degree of effectiveness on microorganisms. Moving from the most susceptible to the least susceptible, the ranking would roughly look like this:

  • Mycoplasmas.
  • Gram-positive bacteria (Staph. and Strep.).
  • Gram-negative bacteria (E. coli, Pasteurella).
  • Enveloped viruses (coronavirus).  
  • Non-enveloped viruses (rotavirus). 
  • Fungal spores.
  • Picornaviruses (foot-and-mouth-disease virus). 
  • Bacterial spores. 
  • Coccidia. 
  • Prions (bovine spongiform encephalopathy). 

Six things to remember

Here are six considerations when selecting and using a disinfectant:

1. Organic load: You cannot disinfect manure. It is plain and simple. Don't try it. It doesn't work. Organic material (manure, bedding, dirt) will form a physical barrier that protects the microorganism. 

2. Disinfectant concentration: Follow label directions to achieve the proper concentration for best results. Be wary of the "more is better theory". Human and animal safety, harshness on equipment and surfaces, and cost are a few good reasons to stick with the label recommendation. 

3. Contact time: This information is normally listed on the label. Don't make the mistake of thinking a quick dip will do it. Buckets or sinks work well as soak areas. Items like calf tube feeders will float, so find an item to weigh them down so all surfaces are immerged. 

4. Surface area: Cracked wooden dividers in calf pens cannot be disinfected. It would cost less to replace them than the amount of disinfectant needed to inactivate all of the coccidia trapped in the cracks. Smooth, nonporous surfaces are the ideal areas to disinfect. Keep this in mind when purchasing and constructing.

5. Avoid cocktails: It is a bad idea to mix chemicals trying to formulate a magic concoction. Other chemicals can affect the effectiveness of others. Iodine is one example of a disinfectant that can be inactivated relatively easily.  Secondly, this is not safe. Remember baking soda and vinegar from science class?

6. Cost. Do not make the mistake of simply comparing the cost per ounce of the concentrated product. Take into consideration mixing directions and estimated coverage area to compare the cost of disinfection per square foot. The thumb rule is that 1 gallon will cover about 100 square feet. Now, how many square feet are in a calf hutch again?

I have only touched the tip of the cow patty on this topic. To really educate yourself and find some handy charts on selecting disinfectants, read veterinarian Glenda Dvorak's paper at: http://tinyurl.com/yboe7wn.

Angela M. Daniels is a veterinarian with Circle H Headquarters LLC, a dairy and swine veterinary practice, food safety laboratory and DHIA milk-testing and contract research organization in Dalhart, Texas.