NC State Extension

Spray Sanitizing Hatching Eggs

Shell surface contamination of the hatching egg is inevitable in the breeder house environment. Normally, hatching eggs are not immediately set in the incubators upon lay but are one to ten days old before being set. During hatching egg storage there will be multiplication of any bacteria already on the shell surface (see Table 1). The greater the number of bacteria on the eggs, the greater the chance of those bacteria invading the interior of the egg.

Table 1.Effect of Egg Storage upon Shell Surface Contamination

Day 1 of Storage

Day 7 of Storage

Day 14 of Storage

Number of Bacteria/Egg



The goal of the breeder house manager is to use good management strategies to minimize shell contamination. These strategies include such practices as:

  • Keeping nests clean.
  • Keeping storage facilities clean.
  • Collecting eggs frequently.
  • Maintaining proper temperature and humidity in the egg room.

In addition to good management practices, procedures for sanitizing shell surfaces can prevent microbial invasion if used properly. One method used extensively in the past was fumigating hatching eggs with formaldehyde gas after collection. This procedure proved very effective but caused the Occupational Safety and Health Agency (OSHA) to express concerns for safety. An alternative to fumigation is spraying the shell surface with an egg shell sanitizer. Numerous sanitizers on the market have proven useful, but, to be effective, the sanitizer must be used correctly.

Proper Selection and Dilution

The use of an effective sanitizer is essential to minimize contamination of the shell surface. Different classes of sanitizers (Quaternary Ammonium, Phenolics, Peroxides, etc.) kill microbes in different ways. Therefore, to assure effective control, the specific procedures for each sanitizer must be followed meticulously. Some classes of sanitizers are more effective than others when used in adverse environmental conditions like poor water quality. A sanitizer used on the egg must be effective at controlling microbial populations yet not toxic to the developing embryo. The entire sanitizer formulation should be examined to assure that none of the other compounds in the formulation can have an negative effect. Even compounds which are normally used as a hatching egg spray can be toxic if they are used at a concentration greater than the manufacturer recommendation. Sanitizers have been evaluated for optimal dilution, and using a concentration above the recommendation could potentially harm the embryo. Care must also be exercised not to use a compound which can deter the movement of oxygen to the embryo through the shell.

Correct Application

Immediate application of the sanitizer as soon as the eggs are collected is of utmost importance. Failure to apply the sanitizer in a timely manner will allow bacteria an opportunity to enter the shell through the pores and reside in the shell membranes. There the bacteria will not be exposed to the sanitizer and can then cause contamination of the egg’s interior.

To kill as many organisms as possible all spray sanitizers need to be applied in a manner which will thoroughly wet the shell surface. If the spray is applied insufficiently on the egg shell surface it may not reach some organisms, or possibly only injure some which can usually recover if the proper conditions exist (see Table 2).

Table 2.

Total Bacteria Colonies on Shell Surface for Non-treated Controls and Eggs with
Inadequate and Adequate Coverage of Sanitizer

Non-Sanitized Controls

Misting with Sanitation (Inadequate)

Thorough Coverage with Sanitizer

121,263 colonies/egg 

43,830 colonies/egg 

331 colonies/egg 

Chemical egg sanitizers possess physical properties similar to those of household cleaners and disinfectants. For this reason, extreme care should be taken not to spill or splash the sanitizer in the eyes, on skin or on clothing.

Implications of Improper Sanitizing

Proper selection and use of a sanitizer is essential to good spray sanitation management and can prevent additional problems in the hatchery. Since most incubators have greater than a 40,000 egg capacity, thousands of eggs and chicks could become contaminated if an infected egg explodes, breaks or becomes cracked inside the incubator. The proper practice of good management strategies will prevent microbial outbreaks and aid in the production of quality chicks.

Prepared by Michael Wineland, Extension Poultry Specialist, and Carmen Christopher
North Carolina State University
6/96, PS Facts #23
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