Often when we see issues arise despite treating with zinc it isn’t due to the spore counts being overwhelmingly high, it’s due to our zinc dosing being inadequate.
This can be due to a multitude of reasons that include (but aren’t limited to):
So how do we know we are achieving what we set out to in the first place? The important aim for what we are doing is to achieve circulating zinc levels 20-35umol/L in blood, this can be tested for by taking 10 cows 2-3 weeks after implementation of full rate supplementation programs to check how you are getting on, this will answer the question “are your cows getting enough zinc”? If you are not achieving the required levels then we can look at how this can be achieved.
In addition to this, when the spore counts are on the rise and we are wanting to make sure that it is being effective then it is a sensible move to check, testing 10 animals for GGT levels will enable us to determine the effectiveness of the program (its efficacy). In order for us to be able to do this effectively it is important that there is suitable potential exposure to FE, so this needs to be after the spore counts for the area have exceeded 20-30,000 for a period of 2-3 weeks.
GGT is the acronym for a liver enzyme that will rise in response to any damage done to the liver, measuring GGT levels will expose the sub-clinical disease that may be occurring and will help to dispel any complacency that all is well just because there is no clinical evidence of FE.
If in doubt please contact your vet to discuss. It is worthwhile to test your cows and make sure that what you are spending your money on what is going to be effective!