Cow footbaths: chemical dilution rate

It’s vital to know the volume of your footbath so you use the correct amount of chemical. This page explains recommended dilution rates and how to calculate how much you need.

Several disinfectants have been shown to be beneficial in controlling digital dermatitis (DD):

• Formalin, diluted at 2–4%
• Glutaraldehyde, diluted at 2–4%
• Copper sulphate, diluted at 4–5% for non-acidified and 1–2% for a buffered acidified solution

Other commercial products claiming to control DD contain peracetic or organic acids, and there is some evidence to support their use. There isn’t a perfect footbath disinfectant.

Formalin: is banned in a few countries due to possible human health problems from carcinogenic fumes if not handled carefully. Only use it when you have plenty of ventilation (outside, for example). Formalin is a natural gas and evaporates rapidly, so it’s not an environmental risk, and in slurry stores it degrades to carbon dioxide and water.

Glutaraldehyde: also carcinogenic.

Copper sulphate: is banned in some countries because it accumulates in soils, creating an environmental hazard if discarded onto pasture. You can use acidified copper sulphate to enable lower levels of copper sulphate to be used to achieve the same effect in the footbath. This can also reduce the cost, as copper sulphate is relatively expensive compared with formalin.

Antibiotics aren’t suitable for use in footbaths. As well as being expensive, there’s no evidence that they’re any more effective than other disinfectants. Their use in footbaths is also irresponsible, as it risks antibiotic resistance developing in the environment.

Parlour washings have been largely discredited and should not be used. Their high pH can deactivate formalin, glutaraldehyde and copper sulphate, and the soaps can soften the skin, making cows more prone to DD.

Hypochlorite is particularly adversely affected by organic matter (such as faeces), so it’s quickly rendered ineffective in a footbath.

How much chemical do you need to add for the volume of your footbath?

It’s essential to know the volume of your footbath so that you can calculate how much chemical to add to make the right dilution rate.

To calculate the volume, measure the width, length and depth in cm. Multiply them together, then divide by 1,000 to give the answer in litres.

For example, a footbath that’s 60 cm wide, 300 cm long and 12 cm deep has a volume of (60 x 300 x 12)/1000 = 216 litres.

If your footbath is on a slope, take the average depth from the middle.

For automated systems, calculate how much chemical you’re using each week to check the calibration is still correct.

For example, a 300 litre automatic footbath operating at three fresh baths per day, using automatically dispensed formalin, will use approximately 1,000 litres of formalin a month for a 4% solution: 3 x 300 litres per day, 7 days per week = 6,300 litres; at 4% = 250 litres formalin per week.

You can use the AHDB Footbath Calculator to calculate how much chemical to add to get the correct dilution rate. 

Formalin

Formalin is a 37% solution of formaldehyde.

If you’re using formalin, we recommend using a 2% strength for a week, before increasing it to 4%. This allows the cows to get used to it.

A 2% strength can also be used for a maintenance level in herds where DD is well controlled.

• For 4% strength, dilute 40 ml of formalin in 960 ml water
• For 2% strength, dilute 20 ml of formalin in 980 ml water

Copper sulphate 5%

If you’re using copper sulphate crystals, use 50 g of crystals per 1 litre of water. Remember that some of the copper remains in suspension rather than fully dissolving.

Acidified copper sulphate solutions mean a greater proportion is dissolved and you can use a lower concentration.