May 12, 2009

Facial Eczema (FE). Farmer Information. Part 12. (Dairy cattle). Zinc sulphate. Direct addition to supply tank

Agriculture, farming, animal husbandry, animal health, disease, Facial Eczema, prevention, zinc, zinc sulphate, dairy cattle, addition of zinc to supply tank.

By Dr Clive Dalton

Original 1991 information written by Dr Barry Smith and Dr Neale Towers, Ruakura Agricultural Research Station, Hamilton, New Zealand.

12. Facial Eczema: (Dairy cattle). Zinc sulphate.  Direct addition to supply tank
  • On many farms trough water is drawn from a large supply tank which feeds water to the troughs at a constant pressure. 
  •  Most tanks are at least 22 000 litre (5000 gal) capacity and, when the tank capacity is sufficient to provide more than the expected daily draw-off by stock, the zinc sulphate can be added direct to the tank (Fig.1).
  • As a rule the tank should contain about 100 litres for every lactating cow or cow equivalent.

To calculate the amount of zinc sulphate to be added each day.

  • Use the table below to calculate the dose rate for each class of stock on the farm.
  •  Then total these figures.
How much zinc sulphate would a farm with 160 Friesian milking cows, 65yearlings and 40 calves need each day?

160 COWS x 36 g =5760
65 yearlings x 22 g = 1430
40 calves x 159 = 600
Total = 7790 g = 7.8 kg

Two forms of zinc sulphate
There are two forms of zinc sulphate available.
(1). Zinc sulphate heptahydrate is the material commonly available.
(2). Zinc sulphate monohydrate is now also being sold; this is a more concentrated form of zinc sulphate and is used at two-thirds the dose rates used for the heptahydrate.

  • Once calibrated, a volumetric measure is sufficiently accurate for regular use.  
  • Weigh out the required zinc sulphate into a plastic bucket. 
  • Level the surface and mark the height. Fill the bucket to this level each day.
Daily Maintenance
  • Add the daily zinc sulphate to the supply tank at the same time each day.
  •  The zinc sulphate should be dissolved in water before adding to the tank.
  • If the supply tank is regularly refilled, e.g. by a pump on a time switch, the zinc sulphate should be added just after filling.
Twice-weekly or weekly maintenance
  • If the supply tank is large enough to supply water for several days without emptying if the inlet is shut off, then it is not essential that zinc be added daily.
  •  At each visit add enough zinc sulphate to last until the next visit, i.e. multiply the daily requirement by the number of days until next serviced.
  • The greater the interval between servicing the greater the variation in zinc concentration in the supply tank and the greater the chance the water will occasionally be unpalatable to the stock.
  • Service as frequently as possible - do not leave more than half the number of days needed to empty the tank.
Concentrated zinc sulphate solutions are caustic. Wear protective goggle and avoid direct skin contact.

This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

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