Vet warning for farmers: Get zinc dose right!
Facial eczema spore numbers are already reaching dangerous levels in northern Taranaki.
Animals are at risk when spore numbers rise above 20,000, says Robyn Lofthouse (Waitara) a veterinarian with Energy Vets Taranaki Ltd. The veterinary practice monitors eight sites on a weekly basis in an area bounded by Tariki in the south to Awakino in the north.
‘‘But we would like to be monitoring 200-plus sites. We need more farmers to monitor what is happening on their own farms,’’ says Lofthouse.
‘‘Only by monitoring their own farms will farmers know when to start and stop preventative measures for facial eczema. They cannot rely on their neighbour’s spore count, nor can they rely on individual counts from the monitor farm in their area.
‘‘Know what is happening on your own farm. Spore counts differ from farm to farm and even from paddock to paddock. The only way for farmers to know where they stand is to collect and test grass samples from their own farm on a weekly basis.
‘‘We are already (from mid- January) getting counts from farms in our area at or above the 20,000 level and we have recently seen cases of facial eczema, too.
‘‘In previous years, toward the end of the season, we have seen counts persist above 10,000 (safe levels) until the end of April/early May.’’
Taranaki dairy farmers, claims Lofthouse, rely too heavily on the least-effective prevention method for facial eczema – water trough treatment.
‘‘It has proven to be the least reliable method for facial eczema prevention,’’ she says.
‘‘Cows need to ingest enough zinc on a daily basis in order to raise the concentration of zinc in the bloodstream to a high enough level to stop the toxin, sporidesmin, from damaging the liver. If the methods used to prevent facial eczema do not provide animals with a high enough concentration of zinc in their bloodstream, they will end up with liver damage.
‘‘Not enough zinc in the cow’s system is equivalent to no zinc at all!
‘‘This is a message that cannot be stressed enough, and I believe there is a misconception out there, that giving the cows some zinc (eg, half rates in feed or in water) is doing something. It’s not!
‘‘When it is time to start with zinc treatment, cows need to get full rates, according to bodyweight. Farmers should make sure they dose to the correct weight and at the correct rate. Calculation errors are a common reason for the failure of facial eczema prevention methods.’’
Spraying too late with fungicide at a time when the counts are already at toxic levels is another example why treatments fail, says Lofthouse.
‘‘Fungicide spraying prevents germination of spores which are there at the time, so farmers need to spray when the counts are still low (5-10,000). Grass needs to be actively growing for spraying to be effective, as it is absorbed by the plant.
‘‘Every year is a facial eczema year, and animals which do not get enough zinc and graze dangerous pastures will get liver damage. Liver damage is irreversible, therefore animals which took a hit one year, face the next eczema season with an already (potentially severely) compromised liver. It won’t take much more damage to tip those animals over.’’
Drenching in the shed is a reliable way for dairy farmers to get enough zinc into their cows, says Lofthouse.
However, this applies only when the cows are drenched to the correct weight, and only if drenched daily, she says. ‘‘Make sure that drench guns are delivering accurate doses and cows are getting the correct dose for their weight.
‘‘Zinc capsules are a very reliable way to protect all classes of stock. Farmers need to insert the capsules at the right time, which they can know only by monitoring their own farm. They should avoid inserting capsules too early, and potentially running out when the FE risk is still high.
‘‘Farmers should make sure they repeat the treatment at the correct interval if the counts on their farm are still elevated. Again, they need to dose their animals to the correct weight range to ensure enough zinc in their system.
‘‘Please don’t forget the young stock! They can often get missed. Farmers absolutely cannot rely on zinc in the water to protect their calves. I urge them to use zinc capsules for their calves and heifers.
‘‘A number of our farmers use zinc in the feed. While this can be reasonably effective, again there are a lot of variables that could result in inadequate zinc getting into the cows. Examples include cow size affecting intake, wastage and variable intakes in the feed pad or paddock situation. This can be controlled better with in-shed feeding.
‘‘Other variables include individual cow taste – some won’t eat enough – or cows lower down in the hierarchy missing out and not getting enough.’’ Milk indicator
A drop in milk yield is usually the first sign that a cow has facial eczema, says Robyn Lofthouse. Farmers may notice reddening or swelling of the udder and teats. Raised, lightly coloured areas of skin which eventually peel will be the most obvious sign of FE, she says. ‘‘In cases where the bladder is affected, bloody urine may be seen.
‘‘Affected animals must have access to shade to protect their sensitive skin from further sun damage. Consider once a day milking for affected animals, or drying them off. Zinc creams can be used to cover sensitive skin areas, too.
‘‘There are various other tonics/supplements available to administer during the recovery period. Liver damage is, however, permanent.’’