Jack Tieberg, Curtis Leyk, D.V.M., Aaron Stephan, Ph.D.
Once Inc., Plymouth, MN
Quantification of eggshell bacterial reduction by UVC and chemical disinfection methods
BACKGROUND
Fertile eggs are often contaminated with bacteria, which can reduce
hatchability and chick quality Therefore, heavily contaminated eggs (e g
“floor eggs”) are generally not suitable for hatching However, given the high
value of GP, GGP, and Pedigree Stock eggs, disinfection procedures that
increase the hatchability of the eggs and hatched chick quality have significant
value Two methods for disinfection of eggs include the use of chemical
disinfectants or the use of Ultraviolet C ( light Chemical disinfectants can
include quaternary ammonium compounds, oxidizing agents, or alcohols UVC
is a type of electromagnetic radiation that can be used in biosecurity due to its
ability to cause covalent modifications to biological molecules including
nucleic acids and proteins Germicidal UVC light emitted from mercury lamps
has a wavelength of 254 nm and is effective at killing microorganisms such as
viruses and bacteria
OBJECTIVE
The objective of this study was to determine the baseline bacterial contamination
levels of non disinfected eggs laid in nest boxes (“nest eggs”) and eggs laid on
the floor (“floor eggs”) and to compare bacterial reduction between chemical
disinfection and disinfection using UVC.
METHODS AND MATERIALS
Eggs were sourced from commercial Hy line W 36 layer hens (aged 84
weeks) as a proxy for breeder eggs and were housed in a research pen
setting that included nest boxes and perches The experimental design was
completely randomized 2 x 2 x 2 factorial design with 2 levels of egg source
(nest or floor), 2 levels of UVC treatment (yes or no) and 2 levels of chemical
disinfection (yes or no) Ten eggs were tested for each factor/level
combination (n 10 All eggs were treated in the following groups:
1) No treatment (Control) (Eggs were placed directly on a setter tray (side by side, 2 columns by 5 rows) and set aside for recovery and plating
2) 5 minute UVC exposure Eggs were placed directly on a setter tray (side by side, 2 columns by 5 rows) and placed into a Bioshift UVC Chamber (ONCE inc Plymouth MN) The chamber ran for 5 minutes, and the tray was set aside for recovery and plating The minimum dosage of UVC to the exposed eggs was estimated at 210 mJ /cm 2 in 5 minutes
3) Chemical disinfection with (n Alkyl (C 12 68 C 14 32 Dimethyl
Ethylbenzyl Ammonium Chloride) n Alkyl (C 12 68 C 14 32
Dimethyl Ethylbenzyl Ammonium Chloride (Clorox wipes)
Eggs were individually wiped with a single Clorox wipe for 10 s Each egg
used a new wipe The wiped eggs were placed on setter tray and set aside
for recovery and plating
4) Chemical disinfection and a 5 minute UVC exposure Eggs
were individually wiped with a single Clorox wipe for 10 s Each egg
used a new wipe The wiped eggs were placed on setter tray (side by side, 2
columns by 5 rows) and placed into the BioShift UVC Chamber The chamber
ran for 5 minutes, and the tray was set aside for recovery and plating
This treatment process was the same for both nest and floor eggs
Following treatment, eggs were washed with 10 mL sterile Phosphate
Buffered Saline ( Invitrogen) and 1 mL of the wash was used to prepare a
10 x dilution series, which was then plated on non selective Tryptic Soy Agar
plates ( Sigma Aldrich) and incubated for 24 hours at 37 ⁰ C Colonies
were counted and compared to the no treatment (control group) which was
used to establish a baseline of contamination for each group Following the
counting of colonies and an established quantification of bacterial
contamination, a 3 way analysis of variance (R version 4 2 3 was performed
The 3 way analysis was used to compare bacterial contamination differences
based on egg source, UVC treatment, and chemical treatment while also
looking for interactions between egg source and UVC treatment, egg source
and chemical treatment and lastly UVC treatment and chemical treatment.
RESULTS
Eggs collected from the floor had on average 76 times more bacteria
compared to eggs collected in nest boxes UVC irradiation of nest eggs
resulted in a 1 41 log ₁₀ reduction of eggshell bacteria Chemical disinfection of
nest eggs resulted in a 2 19 log ₁₀ reduction, and combined UVC plus chemical
disinfection of nest eggs resulted in a 3 10 log ₁₀ reduction showing an additive
effect UVC irradiation of floor eggs resulted in a 1 32 log ₁₀ reduction of
eggshell bacteria Chemical disinfection of floor eggs resulted in a 2 11 log ₁₀
reduction, and combined UVC plus chemical disinfection of floor eggs resulted
in a 3 52 log ₁₀ reduction A 3 way analysis of variance (R version 4 2 3 showed
significant differences in egg source (p 0 001 UVC treatment (p 0 001
and chemical treatment (p 0 001 but no interactions between egg source
and UVC treatment ( 0 05 egg source and chemical treatment ( 0 05 or
UVC treatment and chemical treatment ( 0 05 (Results and Graphs listed
below).
Results
CONCLUSIONS
The results of this experiment indicate the ability of UVC, chemical disinfectant
and a combination of the two are effective at reducing bacterial contamination
on eggshells In a Breeder house with approximately 15 000 birds, disinfection
with UVC on fertile eggs could prove as a cost effective approach Factoring in
fixed costs and labor the UVC disinfection is estimated to cost 0 057 dz and
chemical disinfection is 1 45 /dz Altogether the results of this study can help a
breeder decide on the most cost effective approach to disinfecting fertile eggs
for hatching.
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Keywords: UVC, Biosecurity, Breeders, Eggs, Disinfection.
