Cleaning and disinfection for free range farms

Published on : 30 Aug 2022

Effective cleaning and disinfection plays a key role in maintaining good biosecurity and bird health, however, implementing this does have its challenges, especially for free-range units.

The stages for cleaning and disinfecting the inside of a house are the same across the poultry industry. These include the removal of organic matter (litter), removal of dust, removal and cleaning of equipment and house specific boots/overalls, cleaning water lines and checking for signs of rodents and responding appropriately. The key point is to allow enough time to do this process thoroughly. Plan for at least two weeks downtime.

Further challenges are presented in terms of cleaning and disinfection for free-range birds due to their access to the external environment. The areas around the pop holes also allow contaminants from outside to enter the house, the range can attract wildlife and pests, especially if feed or water is accessible, and the range is at risk of contamination from other environmental factors such as dust from nearby farms and wildlife faeces. This raises the issue of how to clean and disinfect an area which is predominately soil and which is continually exposed to external disease challenges.

Inside the house
The first step is cleaning. This should take place soon after the birds have been removed unless an important Salmonella strain is present, when it may be best to let bacterial levels subside before disturbing dust and removing litter, especially on a multi-age site. 

Effective cleaning is equally, if not more important than disinfection, as cleaning removes the bulk of the muck and therefore the interfering substance that limit the effect of disinfectants, and effective cleaning is needed to allow disinfectants to reach all surfaces as well as to reduce pests such as red mite, litter beetles or flies prior to treatment.

After the house has been depopulated, dry cleaning can begin. All organic matter (litter/muck and dust) should be removed from the floor, surfaces and belts. Removing the litter removes the majority of the disease risk as pathogenic organisms such as Salmonella can multiple and survive well in faeces. Any feed remaining in feeders should be removed as quickly as possible to avoid attracting rodents or other wildlife into the house. Salmonella has been found to survive in dust for up to nineteen years and can be a cause of re-infection between flocks. Remember to check areas such as high ledges, ceilings and fans, which may be difficult to reach, and nest boxes and belts, which can be inaccessible. This is especially important in layer houses as the birds will have been in place for around a year and a substantial amount of dust is likely to have built up.

Then any equipment such as perches, raised flooring, nest boxes and multi-tier system equipment which is removable, should be taken out of the house for thorough cleaning and disinfection. The benefit of this is that equipment can harbour pests, or may be difficult to clean in-situ. Removal allows a thorough inspection of the equipment for damage as well as inspection of the house. It also makes the house easier to clean, with fewer obstructions to clean around. Any house- specific equipment, clothing and foot wear should also be removed for thorough cleaning and disinfection.

At this point the water lines should be cleaned using an appropriate product, usually an oxidising disinfectant such as peracetic acid, to flush through the system. There is a chance that some nipple drinkers can become blocked by dislodged biofilm after flushing so it is important to remember to check them before reintroducing new birds and to use a two stage cleaning programme to dissolve biofilm then dislodge it if needed.

After dry cleaning has taken place, wet cleaning can begin. It is not possible to effectively disinfect a dry-cleaned house and this practice is likely to lead to a build-up of disease organisms and pests. Surfaces should be soaked and a detergent applied. Detergents help to loosen dried- on dirt and grease, and may be beneficial for layer houses where birds have been in place for many weeks and muck has been allowed to build up. It is essential to give the water and detergent time to work, to soak in. This then makes removal of dried material much easier during the wash down stage. Wash down all surfaces, removing any remaining detergent and organic matter. 

Once these steps have taken place this is the time to check carefully, using a powerful torch and white moist wipes, how thorough the cleaning has been, have any areas been missed, especially underneath low surfaces or on top of high ones, behind fixed equipment, especially in and around vents, nest boxes and egg belts,  in cracks in the floor or walls and in feeding systems.  If the cleaning is not of the standard you require this is the time to repeat it. Disinfectants do not work well if there is still muck in the house so removing it thoroughly while you have the chance is important. If feeders, troughs/chains and/or drinkers/ remain in the house during cleaning, make sure these receive the same level of cleaning and that any excess water is removed to allow them to dry before disinfecting. Leaving wash water in these will cause additional dilution of the disinfectant when it is applied, making it less likely to be effective in killing any bacteria present, which may even multiply if the disinfectant is diluted by residual water. 

Once you are happy with the standard of cleaning, the house should be allowed time to dry. The drying steps do increase the length of the process but they are key because bacteria and viruses can survive much better in wet conditions and allowing the house to dry reduces any bacterial load present. A minimum of 24h drying time is recommended, although the longer the better. 

If maintenance tasks are required, now is the time to carry them out. Be aware that these can dislodge trapped muck and dust which can re-contaminate the area which may need re-cleaning following major maintenance work.

The next step is to apply a disinfectant. The first challenge here is selecting which disinfectant to use. This may already be outlined in your biosecurity plan however it is worth revisiting your selection to check it is still appropriate for the task required. 

The activity of disinfectants is affected by their active chemicals, the temperature they will be used at, the amount of organic matter present, the hardness and cleanliness of the water used to dilute it and possible interactions with any detergent which has not been rinsed away. Disinfectants used should also be approved by Defra for use against notifiable and zoonotic diseases which fall under Disease Orders. All approved products appear on a public list (http://disinfectants.defra.gov.uk/ DisinfectantsExternal/Default.aspx?Module=ApprovalsList_SI) along with the manufacturer details and concentration for which they have been approved for each disease. For poultry the Orders of interest are Poultry Orders which covers Newcastle disease and Avian Influenza and General Orders which covers Salmonella and other bacteria. The concentration of disinfectant required to pass each test will vary and it is recommended to use the General Orders (GO) concentration as this will kill viruses as well as bacteria, whereas the Diseases of Poultry Orders concentration is unlikely to eliminate Salmonella. The Lion Code stipulates that “Only Defra-approved disinfectants shall be used during clean-out. Those in use must be Defra approved for both General Orders (e.g. Salmonella control) and for diseases of poultry”. The same applies for disinfectants used in boot dips on Lion Code farms.

Before starting disinfection check that the product you have on site is in date and check the Defra Approved concentration on the Defra website as the list is live and approved concentrations do change over time.

Research carried out by APHA has investigated how different disinfectants perform when used in boot dips and for surface disinfection, and there are differences between the different test environments. For use in boot dips, chlorocresol-based disinfectants performed the best, they were able to cope with increasing levels of organic matter, as more muck would be added each time the boot dip was used. The chlorocresol-based products also remained active for the longest period of time. However, for surface disinfection glutaraldehyde-based products, especially those in combinations with formaldehyde, rather than just quaternary ammonium compounds, were most effective for killing Salmonella. Both studies included disinfectants at GO and half GO concentrations, with products tested at half the GO concentration usually failing. This highlights the importance of ensuring disinfectants are used at the recommended concentration. 

Disinfectants should be applied in accordance with the manufacturers’ safety guidelines, wearing appropriate protective clothing and ensuring a good coverage is achieved on all surfaces. Contact time is important, to allow the disinfectant to be fully effective so disinfectants should be applied to saturation point at high pressure and then left to dry on verandas and any service areas such as egg rooms or stores should be cleaned and disinfected to the same standard as the rest of the house.

After disinfection and before birds are placed, continue to maintain good biosecurity. Do not store equipment in the clean house, ensure boot dips or boot changes are in place and used if staff need to re-enter, and maintain rodent and pest control.  Be especially careful when using vehicles that enter the clean house to set it up or deliver birds.

Mobile units
Mobile units require the same level of cleaning and disinfection as a fixed structure house, however this will require the house to be moved to a clean area and good drainage during cleaning and disinfection in a way that avoids transferring contamination. The dry cleaning steps will include the removal litter and dust from the internal surfaces of the house, and the removal of slats, nesting boxes and artificial scratching areas as well as any other removable equipment. The build-up of manure beneath the house is a potential harbourage site for rodents and other pests, and therefore disease. Disturbing these during cleaning has the potential to spread disease from one house to another and active rodent control is required. Cleaning should also include the removal of wild bird droppings from the external surfaces of the house.

Wet cleaning and disinfection can then take place as discussed above.

Range
Cleaning the range is more difficult and good range management is the best solution, i.e. preventing puddles forming which can attract wildlife, not feeding the birds in the range and having a robust external fence and hedge in place which limits access by foxes, feral cats etc. and dust contamination from any nearby farms. The area closest to the house is most likely to be contaminated, where birds have congregated after leaving and to get back into the house, especially in shaded or poorly drained areas.. 

If a serious Salmonella has been present, the surface layer of muck around the house should be scraped away, the immediate surroundings safely sprayed with 5% formalin. Products are available to help disinfect the range, generally in the form of lime-based powders and one of these can be applied after the formalin has dried or soaked in. These products alter the pH of the soil making it less attractive for the survival of bacteria. It should be noted that none of these dry powder products are Defra- approved as the Defra testing scheme only tests products applied as liquids. 

External areas
The environment around the farm has the potential to contaminate the house and infect the birds with pathogens, through airborne transmission or, more likely in most cases, by staff or visitors walking contamination in or contamination being picked up by equipment. It is important to ensure the areas immediately surrounding houses, particularly access routes, are also included during cleaning and disinfection. These include entrances to houses, ante rooms, concrete aprons and surrounds, areas around feed bins, including where feed delivery lorries have access to and dead bird bins. Cleaning and disinfecting these areas regularly and at depopulation will help minimise the risk of infection across the whole farm. 

Cleaning and disinfection is a basic prerequisite, not a new solution, however doing it well can have real benefits to bird health, production and disease control.