2014 season trial
A number of outbreaks of clinical facial eczema were seen on farms in the region. It may surprise many that the majority of these farms had some form of facial eczema prevention in place (ie. zinc supplementation). Even the best laid plans can come unstuck and in most herd outbreaks of facial eczema cows are found to have insufficient zinc circulating in their systems despite regular zinc supplementation occurring.
Franklin Vets was asked to assist in a DairyNZ and Sustainable Farming Fund trial looking into on-farm zinc supplementation practices in the region. The trial was particularly concerned with determining how the various methods and rates of supplementation were reflected in blood zinc levels and in levels of liver damage (ie. facial eczema damage). We are to visit 20 farms across the practice, weigh and blood-sample cows, collect spore counts from multiple sites across the farm and complete a survey detailing facial eczema management on the farm.
The results of this study were interesting to say the least with a number of farms demonstrating lower than ideal zinc levels and significant levels of hidden liver damage and disease (see graph). Of the 8 farms sampled, 50% had less than protective zinc levels and 38% had one or more animals with subclinical liver damage. Reasons for the failure of zinc to reach the cow appears to be multifactorial but is most commonly associated with errors in calculating dose rates, frequency or infrequency of dosing and the zinc supplied not making it to the cow (eg. dilution, evaporation, water leaks).
This is a bigger issue than we realise as facial eczema is often a hidden disease (we only see the tip of the iceberg). All herds should consider zinc testing as an effective and rapid assurance of their FE control programme. Talk to your vet today.