Here is some info I found on edema Nova.
Like other metabolic diseases which appear at calving time, the causes of udder edema can usually be traced to feeding and management practices during the dry period.
In udder edema, there is an accumulation of fluid in the udder. Accumulation begins at the base of the udder and, in mild cases, may be present around only one or two quarters. As the severity of the edema increases, the entire udder becomes affected and fluid may spread through the abdominal area, the thighs and vulva.
There does not appear to be one single cause of udder edema. Normal metabolic changes, genetics and nutrition likely all play a role.
Metabolic Changes
Most cows experience some edema prior to calving due to hormonal and physiological changes, which take place prior to calving.
Increasing pressure, caused by fetal growth, results in a restriction of blood and lymph flow away from the udder in late pregnancy. This occurs concurrently with an increased blood flow to the udder. Smaller blood vessels and a reduced fluid flow is likely the reason why heifers are more prone to udder edema than are cows.
There is a drop in blood proteins as the cow transfers immunoglobulins (proteins) to colostrum. This is thought to increase the permeability of the blood vessels allowing an increase in fluid buildup.
Changes in hormone levels are also believed to play a role in udder edema. This may be why the dairy you spoke of finds that lute works for edema.
Genetics
Increased susceptibility to udder edema is an inherited trait.
Nutrition
There are several nutrition factors implicated in udder edema.
High intakes of potassium during the dry period predispose cows to udder edema by increasing fluid retention. Potassium levels in dry cow forages are often over 2% - much higher than required. Feed forages with low potassium such as grass (eg. timothy) hays and corn silage (in limited amounts) during the dry period. Intake of potassium should not exceed 250g.
A high sodium (ie. salt) intake also predisposes cows to udder edema by increasing fluid retention. Limit salt intake during the dry period to 30g (one ounce) per day. If salt is fed free choice, provide it in block form rather than loose as this will decrease consumption. Remove any sodium bicarbonate buffer, which may be present in the feed, typically from the milking cow diet. Check the water for sodium levels as some areas in Manitoba have high sodium, or salty, water.
Low magnesium during the dry period has been implicated in udder edema. Ensure close-up dry cow rations contain 0.4% magnesium.
Excessive grain intakes prior to calving have been associated with increased incidence of udder edema. Feed a dry cow diet that is properly balanced for protein and energy.
Ensure levels of zinc and vitamin E are adequate in the close-up dry period (40 mg/kg and 1200 IU/day respectively). Both help to reduce the effects of oxidative stress on the udder. Oxidative damage can be triggered by the release of iron in times of stress, trauma or nutritional imbalance.
http://www.gov.mb.ca/agriculture/livest ... 18s05.html
I would get your nutritionist involved and find out exactly what your TMR contains for salt and minerals and add into that the % of salt content in the water they consume.
