How clean is your cow shed?

Ideally, do it as soon as possible after the last calf leaves the shed. There should be easy access for machinery for efficient removal of soiled bedding. This may involve demountable pens with drop pins or clips, or slide doors to gain access to larger pens.

Manual removal of soiled bedding is time-consuming and labour intensive and will ultimately lead to the job not getting done. Calf sheds should be designed to reduce the time spent on manual labour which in itself reduces the risk of personal injury.

Disinfectants will not clean dirt

Disinfectants will not clean dirt and all organic material including soiled bedding and dried manure must be removed prior to disinfection. This means the pen walls and floors should be washed thoroughly with soap and water, and allowed to dry prior to the application of a disinfectant. Pen walls should be made of a non-porous material to allow thorough cleaning.

Time and UV light alone will greatly reduce the number of pathogens in the environment.

There is an array of disinfectants used for varying purposes on dairy farms. Some are more suitable for housing and others for feeding equipment. It is important to know which disinfectant is suitable for what purpose and which mixing rates are safe to use and when.

In calf sheds, a disinfectant needs to be effective against pathogenic viruses, bacteria and protozoa such as Cryptosporidium parvum. For viruses and bacteria, there are many disinfectants available. However the oocysts (eggs) from Cryptosporidia are very stable in the environment and relatively resistant to chlorine-based disinfectants. This can create a problem in calf sheds in that cryptosporidiosis can recur year after year.

Few products are registered for the disinfection of Cryptosporidia oocysts either overseas or in Australia and a holistic approach is required for control.

This includes twice daily pick-up of calves from the calving area, rotation of calving paddocks, good colostrum management, having a clean calf trailer, all-in all-out rearing system and clean ad lib fresh water. Cryptosporidia thrives in damp conditions and calves with access to outside paddocks at a young age can be vulnerable, as the cleanliness of this environment is less controlled.

The main classes of disinfectants commonly used are:

Oxidising agents (e.g. Virkon-S): effective against many bacteria, a broad range of viruses, fungi and bacterial spores. They are relatively stable in the presence of organic material and as such are commonly and effectively used to disinfect calf sheds. They can cause moderate skin irritation and damage some metals.

Chlorine-based compounds (e.g. household bleach): eliminate most viruses, bacteria, moulds, and algae, but not bacterial spores. These compounds are good disinfectants on clean surfaces and are more active in warm water.

However they can irritate the skin and damage clothing, rubber goods and some metals. Chlorine-based disinfectants are generally compatible with soaps but should never be mixed with acids. They are ideal for disinfecting feeding equipment which has already been cleaned with soapy water.

Phenolics: generally active against bacteria, some viruses, and fungi, but not bacterial spores. Phenolics have good activity in the presence of some organic material but are ineffective against rotaviruses which can limit their use in calf sheds.

Quaternary ammonium compounds: effective against many bacteria and some viruses, but not moulds or bacterial spores. Older quaternary ammonium compounds are good on relatively clean surfaces but newer quaternary ammonium compounds can retain activity in the presence of some organic material. They are generally used for the disinfection of the vat or milking machine equipment.

Iodophors (iodine-based compounds): have been used as antiseptics and disinfectants for many years. Iodophors are good disinfectants, but are less effective in the presence of organic debris which limits their use as a disinfectant for calf sheds.

They are generally less toxic than other disinfectants, but can stain clothes and some surfaces. They are ideal for the disinfection of calf navels (in a 7% solution).

Farmers commonly ask about the use of lime in calf sheds. Lime has a positive drying effect and raises surface pH, which helps inhibit bacterial growth. However there is little evidence to suggest lime reduces the number of pathogens and it should be used with a suitable disinfectant.

Regardless of the disinfectant used, always read the label carefully and wear the appropriate personal protective equipment.

All disinfectants used for calf sheds as a control measure for disease should be registered by the Australian Pesticides and Veterinary Medicines Authority (APVMA).

• Gemma Chuck is a vet with Apiam Animal Health Ltd in Victoria.