Often, we hear things like, “Perhaps you should change your treatment; maybe the ‘bugs’ on your farm are building up a resistance to what you are using.” I’ve heard arguments that this could happen and arguments that this is not a concern for dairy farmers. But has anyone ever suggested this about teat dip disinfectants? I don’t think I’ve heard that discussion too many times, if ever.
But some new research may indicate this could be happening. And I think it is worth discussing, especially if an alternative that may be more effective can save you money.
In an article published in the Journal of Dairy Science earlier this year, a group of researchers from North Carolina State set out to see if pathogens exposed to iodine or chlorhexidine would have any resistance to antibiotics.
The long and the short of it was no; no differences in antibiotic susceptibility were observed in pathogens that had been exposed to chlorhexidine or iodine prior to antibiotic exposure.
The great thing about science, however, is sometimes when we are trying to prove one thing we accidentally stumble across something else. And that is just what happened here.
In the process of trying to determine if there was any effect on antibiotic susceptibility, the authors discovered that the pathogens they selected for use (37 isolates of Staph. aureus, which were chosen from a library containing 4,000 milk isolates of Staph. representing common genotypes) were actually more susceptible to chlorhexidine than iodine.
I will stop here because it is important to note that this work should be repeated, as all research should, and I will add that the concentrations of iodine and chlorhexidine that we commonly use in our teat dips were all proven efficacious against the pathogens.
It was lower levels of iodine that were not as effective against the pathogens as compared to similar levels of chlorhexidine.
With that being said, some may think it prudent to be proactive and switch to a chlorhexidine dip, especially if they have a documented problem with Staph. aureus. That is easy enough, and there are many excellent options available for chlorhexidine dips.
Chlorhexidine can be in the form of chlorhexidine digluconate or chlorhexidine diacetate – more commonly referred to as chlorhexidine gluconate (CHG) and chlorhexidine acetate (CHA).
There is no research indicating one is more effective than the other. Most chlorhexidine dips contain 0.5 percent or 0.55 percent chlorhexidine.
Concentrations less than this tend to be ineffective. Chlorhexidine is non-irritating to the skin and kills bacteria for an extended period of time – two excellent qualities to have in a teat dip.
Why haven’t we traditionally used chlorhexidine? I believe the main reason is because chlorhexidine was more expensive than iodine. Additionally, research suggests iodine is more effective against Pseudomonas and Serratia species.
In light of recent price increases of iodine and this research, it may be worth investigating chlorhexidine if you haven’t considered it in the past.
You may still be anxious about making a change. As I mentioned, the concentrations of iodine that did effectively kill all the Staph species in this study are lower than what we commonly use in teat dips, which means you should be OK.
However, a 0.25 percent iodine teat dip may be approaching the concentration that some Staph species in this study were able to tolerate. If you feel you have a Staph problem and do not wish to switch to a chlorhexidine dip, you should strongly consider using at least a 0.5 percent iodine teat dip.
Maybe you want the best of both worlds – the broad spectrum effectiveness of iodine and better control of Staph that chlorhexidine may offer. For the first time ever, a combination iodine/chlorhexidine dip recently became commercially available.
In the past, we lacked the technology to stabilize chlorhexidine and iodine together in the same teat dip. The technology has now been perfected and introduced into the market.
Teat dip is an extremely important factor for a successful milk quality and udder health program. While this research suggests a trend may be developing with certain Staph species showing some resistance to iodine, there is more work that needs to be done.
If you do have a Staph problem on your dairy, it may be worthwhile to consider increasing the percent iodine in your dip or switching to a chlorhexidine dip.
With the increases in iodine pricing, a chlorhexidine dip may be a viable alternative when in the past it was not. It is also important not to forget combination dips, new and old. PD
Belsito researched milk quality improvement while earning a master’s degree from the University of Florida.
