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Hatching eggs are commonly disinfected prior to incubation. For many years, the disinfectant of choice has been formaldehyde (or formalin, which is 37% formaldehyde in water). Formaldehyde is easily converted into a gas, so that all that is needed for it to reach the total surface of all the eggs in the fumigation room is a little air recirculation. Formaldehyde is also an effective and inexpensive disinfectant. However, its carcinogenic properties mean that more and more countries are banning its use, so that hatcheries are looking for an alternative, also with improved labour conditions in mind.

Several good alternative disinfectants are available, which once properly applied and dosed achieve a good microbial death rate on the eggshell and have no negative effects on hatchability and chick quality. Examples are products based on hydrogen peroxide and peracetic acid or on quaternary ammonium compounds and glutaraldehyde. Electrolyzed oxidizing water has also shown good results. These alternatives do however have one big disadvantage, which is that they cannot be applied as a gas. Rather, they are liquids and need to be applied as such. The main challenge therefore is to distribute these liquid disinfectants evenly and in the right amount over the total egg surface of all the eggs loaded on the setter trays in the fumigation room. Another challenge is to limit the time between loading and unloading the fumigation room to the 1 to 1½ hours that was previously needed when applying formaldehyde, so as not to disturb the workflow in the hatchery.

The best option for distribution is ‘dry fogging’, which is the creation of droplets of 5 to 10 microns. These droplets fill the room as a dense fog, ensuring contact with each and every egg. If the droplets are bigger than this, the eggs close to the nozzle will be overdosed and the eggs in the centre of the trolley will remain untouched. Overdosing may lead to closing of the egg pores or damage to the protective cuticle, depending on the disinfectant used, while under-dosing will give poor disinfection results.

Dry fogging sounds easier than it is. While there are many devices available that claim to create small droplets, they often produce droplets over a large range, with only a small proportion below 10 microns. For proper dry fogging, high-quality, fully tested compressed-air supported nozzles are required. The number of these nozzles per fumigation room should ideally be based on 15 minutes fogging time. The rest of the one hour disinfection process is then available for 30 minutes contact time and 15 minutes extraction time. Water is used as a carrier for the disinfectant and dosing should be properly calculated based on the required active ingredient per cubic metre fumigation room.

Advice

  • Invest in good technology that is able to create droplets of 5–10 microns for optimal distribution of the liquid disinfectant over the entire surface of every egg.
  • Ask the nozzle supplier to help calculate the dilution ratio and the total quantity of liquid needed to cover all the eggs without excessive wetting.
  • Evaluate the disinfectant type, dilution ratio and quantity based not only on the reduction in microorganisms, but also on their effects on weight loss during incubation, the cuticula, hatchability and chick quality.
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