Agriculture, farming, animal husbandry, animal health, disease, Facial Eczema, prevention, dairy cattle, zinc sulphate, using in-line dispensers, dairy cattle.
By Dr Clive Dalton
Original 1991 information written by Dr Barry Smith and Dr Neale Towers, Ruakura Agricultural Research Station, Hamilton, New Zealand.
11. FACIAL ECZEMA: (Dairy cattle). Zinc sulphate. Using in-line dispenser.
There are a number of in-line dispensers or dilutors available commercially. Those, which add a constant proportion of a concentrate into the reticulation system, will give best control of dose rates. While it is not necessary to know exactly what the dilution rate is, those systems with variable dilution rates will be easier to set up to provide the correct dose rates.
- Check that it will function with the water pressures, flow rates and daily consumption expected for your property.
- The dispenser should be installed in a sheltered position protected from frost, and at a convenient location for daily refilling.
- The dispenser is best installed on a by-pass line so it can be disconnected when not required without interrupting the water supply.
- The dispenser should be downstream of household or dairy shed water draw-off.
- A source of water will be required for refilling the concentrate tank.
- Fit an in-line filter if your water supply is sandy or gritty to protect the working parts of the dispensers.
- A tank or drum equipped with a sight glass and holding enough concentrate to last between servicing. Alternatively a dip stick can be used to measure the tank contents.
- The size of the tank can be estimated by dividing the maximum daily water consumption of the herd by the dilution ratio of the dispensing unit.
200 cow herd @ 100 litres drinking water/cow/day (maximum) using a unit which adds 1 part concentrate to 128 parts of water.
Concentrate tank size - 200 x 100/128 = 156 litres .
The concentrate tank may be larger than the calculated volume.
1. Set the daily refilling level on the concentrate reservoir.
2. Adjust the dispenser (or tank volume) so that each day half to three-quarters of the solution in the concentrate reservoir is injected into the water supply each day.
- Mark a temporary "FULL" line on the tank and fill to the mark with water.
- Turn on dispenser and record the water level in the tank 24 hours later.
- Refill and repeat two or three times.
- Adjust the position of the "FULL" line or alter the dispenser dilution rate so that from one half to three-quarters of the water in the concentrate tank is used each day.
- Mark two lines at one quarter and one half of the "FULL" line.
- Measure the average daily draw-off from the concentrate tank filled with water.
- The "FULL" line should then be marked at 1.5 times the average daily draw-off. Mark the half and quarter lines in the same way.
- Calculate the amount of zinc sulphate to be added each day.
- Multiply the dose rate for each class of livestock by the number of animals and total these figures.
How much zinc sulphate would a farm with 160 Friesian milking cows, 65 yearlings, and 40 calves need each day?
160 COWS x 36 g = 5760g
65 yearlings x 22 g = 1430g
40 calves x 15 g = 600g
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.
- At the same time each day, add the daily total amount of zinc sulphate to the concentrate reservoir.
- Refill to the “FULL” line with clean water and stir to dissolve the zinc sulphate.
- An in-line dispenser can be used to protect stock at locations which cannot be serviced daily. In this case, the concentrate tank must be large enough to ensure that only half to three quarters of the concentrate is used in the intervals between servicing.
- At each visit, add enough zinc sulphate to last until the next visit. So multiply the daily requirement by the number of days until next serviced.
- Refill the concentrate tank to the “FULL” line.
- Throughout the season adjust the position of the FULL and EMPTY lines or the dispenser dilution rate so that before refilling the concentrate level falls between the two lines on most days.
- Do not be concerned about the occasional day when either more (a very hot dry day) or less (a wet day) concentrate is used.
- Adjust position of "FULL" and "EMPTY lines or dilutions rate only when the concentrate level is consistently outside these limits.
- If wet weather causes very low usage of the zinc concentrate for 2-3 days stop adding zinc sulphate for a few days until the concentrate level again drops to the half empty line.
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.