Often you won’t know how badly affected your cows were by facial eczema (FE) until calving time.
FE is a disease of ruminants caused by a fungus called pithomyces chartarum. This grows on dead plant material at the base of pasture. Its spores release a toxin, sporidesmin, which when ingested by cattle causes damage to the liver and bile ducts.
Clinical signs of FE in dairy cows include; a drop in milk production, shade seeking, inappetence, ill-thrift, weight loss, weakness, photosensitisation (severe and painful ‘sunburn’) and in some cases death. Although only a small number of cows may ‘break-out’ with skin lesions, be aware that many cows in your mob may be sub-clinically affected and have liver damage without showing external signs. This number on some farms can be as many as 10 sub-clinically affected cows for every clinical case.
Body condition is an important factor to manage in herds affected by facial eczema. Ideally cows should be at BCS 5 and heifers at BCS 5.5 (1-9 scale) prior to calving. This will reduce the risk of developing metabolic conditions, infectious diseases, and will maximise productivity and future reproductive performance.
Avoid overfat cows (BCS 6+) as low dry matter intake in late gestation can see them mobilise excess body fat. Mobilisation of fat places additional stress on the liver, predisposing to metabolic issues such as ketosis, fatty liver and milk fever.
Feed for cows affected by FE should provide readily available energy, without excess protein, so that the liver doesn’t have to work too hard to metabolise it. High energy, starchy supplements such as maize silage or meal are good options. As with all transition diets, introduce gradually and avoid any sudden changes in diet. Aim to incorporate some post-calving rations into the pre-calving diet to provide enough time for the rumen microorganisms to adapt. Failure to slowly transition cows onto a diet can lead to acute or sub-acute rumen acidosis.
Other treatment options include vitamin and mineral injections to stimulate the immune system, increase appetite and reduce the incidence of milk fever. Consider injecting with vitamin B12 during clinical disease, two weeks prior to calving and again as cows enter the colostrum mob. HidejectTM (vitamin A, D and E) reduces the incidence of metabolic issues and is recommended one week prior to calving.
The challenge is deciding which animals to treat, as many within a mob may be sub-clinically affected. Your veterinarian will be able to assist you when making decisions around this. It is possible to check serum GGT levels as a measure of residual liver damage in individual cows and as a selection tool for which cows require extra care.
Finally, when managing cows affected by FE, injectable copper preparations are not recommended as a damaged liver is very susceptible to copper toxicity.