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By Dr Vincent Turblin , CEVA Animal Health, France
Nowadays, good cleaning and disinfection practices are widely acknowledged as part of the optimisation of the viable day old chick (DOC) production in a hatchery. Good egg hygiene has often proven to improve the viability and the quality of the DOC. Indeed, a strong bacterial penetration through the egg shell will affect several aspects in hatching quality, like early embryonic mortality, egg yolk infection, DOC mortality before hatching, besides a significant higher mortality and heterogeneity of the chicks during the first week of age.
Vertical and horizontal
Clearly, various micro-organisms can contaminate the hatching eggs in different ways. Vertical contamination will involve the reproductive tract of the hen, including the last part of it which is shared with the digestive tract (the cloaca). Thus, this vertical transmission of the pathogens could be pedagogically divided into two different ways of contamination of the hatching eggs:
Clearly, various micro-organisms can contaminate the hatching eggs in different ways. Vertical contamination will involve the reproductive tract of the hen, including the last part of it which is shared with the digestive tract (the cloaca). Thus, this vertical transmission of the pathogens could be pedagogically divided into two different ways of contamination of the hatching eggs:
· Transovarian transmission, in which the micro-organism is already located in the ovules even before the ovulation. SP and SG are probably the most well known examples of this kind of transmission.
· Contamination of the surface of the eggshell and thus penetration of the pathogen into the hatching egg. It occurs either during the oviposition through the contact with the cloaca of infected hens or immediately after through contact with contaminated faeces and litter. SE and ST can be considered as examples of such ways of vertical transmission.
Source inside hatchery
Horizontal contamination needs a source inside of the hatchery; a kind of reservoir from which air, water or manipulation of the eggs will spread the micro-organisms to the hatching eggs by direct contact. This is the case for E.coli, Pseudomonas and Staphylococus.
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Careful manual dipping of dirty eggs is essential to avoid temperature shock.
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It is important to consider that the environment of the laying house will deeply influence the shell cleanness. Even the quality of the digestion of the hens can also interfere with the quality of the egg (contamination aspect besides all the other nutrition transfers to the DOC). Indeed, after oviposition, those eggs non-contaminated vertically will still remain susceptible to the health status of the breeder flock (Salmonella) and to the pressure of bacteria responsible for hatching-egg putrefaction like Pseudomonas, which will be enhanced in diarrheic flocks.
Bacterial penetration
An intact cuticle is commonly acknowledged as an efficient barrier against penetration. Nevertheless, the immature cuticle of freshly laid eggs could be easily penetrated. Moreover it has to be considered that these freshly laid eggs will be in contact with tough materials on the nests or even the hens themselves can cause scratches on them, so it is a critical stage in bacterial penetration. Besides, there are thousands of pores on the egg shell which are essential for exchange of gases. Most of them are covered by a cuticle preventing liquid and bacterial penetration, but several others are not and thus allow the penetration of micro-organisms into the eggs.
An intact cuticle is commonly acknowledged as an efficient barrier against penetration. Nevertheless, the immature cuticle of freshly laid eggs could be easily penetrated. Moreover it has to be considered that these freshly laid eggs will be in contact with tough materials on the nests or even the hens themselves can cause scratches on them, so it is a critical stage in bacterial penetration. Besides, there are thousands of pores on the egg shell which are essential for exchange of gases. Most of them are covered by a cuticle preventing liquid and bacterial penetration, but several others are not and thus allow the penetration of micro-organisms into the eggs.
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Fumigation with formaldehyde has been the product of choice for a long time. This should take place under proper conditions and in a special room (photo: HatchTech).
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How to disinfect hatching eggs
Immediate application of the sanitiser as soon as the eggs are collected is of utmost importance. Failure to apply the sanitiser in a timely manner will give the opportunity to the bacteria to penetrate into the hatching eggs through the pores of the eggshell, thus reaching the shell membrane. Inside the eggs, the microorganisms will not be exposed to the sanitiser any more and, during the incubation process, they will find the ideal condition to multiply in the egg’s interior. Therefore, the disinfection aims at destroying the microorganisms before they enter into the egg.
Immediate application of the sanitiser as soon as the eggs are collected is of utmost importance. Failure to apply the sanitiser in a timely manner will give the opportunity to the bacteria to penetrate into the hatching eggs through the pores of the eggshell, thus reaching the shell membrane. Inside the eggs, the microorganisms will not be exposed to the sanitiser any more and, during the incubation process, they will find the ideal condition to multiply in the egg’s interior. Therefore, the disinfection aims at destroying the microorganisms before they enter into the egg.
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Source: World Poultry, Vol. 27, No. 7, 2011
