Variable water quality may be key to milk fever outbreaks

25 January 2002




Variable water quality may be key to milk fever outbreaks

By Richard Allison

DIFFERENCES in water mineral content may explain why some transition cow rations fail to prevent cases of milk fever, says one US expert.

When investigating metabolic problems, such as milk fever, water quality is rarely considered, says Agri-King nutritionist Dave Casper.

"The impact of water quality was investigated using data from 1500 US farms routinely tested for mineral concentration by the Agri-King lab. Results showed considerable variability, sodium levels covered a range of more than 900ppm."

Mineral composition also varied year to year from the same water source, suggesting that on-farm tests are needed at least once a year, says Dr Casper.

Water quality in the UK is just as variable, warns the companys UK manager David Donaldson. "Many herds drink from a mains supply which can be highly chlorinated and some areas in Devon have iron rich water."

He believes a move to feeding drier rations to dry cows has increased water consumption.

These minerals in water can interact with those from the ration, says Dr Casper. A high intake of sulphates from water may induce selenium deficiency, increasing the risk of retained placenta, ketosis and metritis in fresh cows.

Similarly, he adds, high levels of chlorides in water may cause calcium deficiency and increase the risk of milk fever occurring when no additional calcium is fed.

To minimise milk fever risk, dry cow rations are typically formulated with a dietary cation anion difference (DCAD) of less than -26.3meq/kg dry matter. But this calculation only considers mineral supply from the ration, he says.

"Differences in water quality can lead to a 30% difference in the total meq/kg DM intake of minerals, despite feeding the same dry cow ration. Water with high chloride and sulphate concentrations can supply a substantial amount of anions and supplementary anionic salt may not be required."

More importantly, without considering minerals from water, a more negative DCAD may be achieved than intended. Dr Casper warns that this will also cause metabolic problems, such as poor intakes and acidosis.

The effect of water quality helps to explain why some transition cow rations fail to prevent milk fever, says Mr Donaldson.

"In light of this, some producers in the UK and Ireland are now monitoring water quality and using this data to adjust dry cow rations."

Water analysis carried out 3-4 times a year will typically cost about £100, much less than the cost of one milk fever case, he adds. &#42


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