©2014 Poultry Science Association, Inc.
The length of storage of emu eggs
and resultant effects on hatchability
Zachary Lowman1 and Carmen Parkhurst
Prestage Department of Poultry Science, North Carolina State University, Raleigh 27606
Primary Audience: Researchers, Emu Producers, Hatchery Managers
SUMMARY
Emu (Dromaius novaehollandiae) are a large flightless bird and are members of the Ratite
family. Emu originated from Australia and have long been raised for their meat and oil. The
cost associated with raising emu is high, which makes emu meat and products expensive. Emu
have very low hatchability rates when compared with other commercial poultry. To date, little
research has been published on egg storage conditions of emu eggs, which may contribute to the
decreased hatchability of the eggs. In this study, eggs were stored for times ranging from 1 to 8
wk and subsequent effects on moisture loss and hatchability was recorded. We found significant
differences (P < 0.0104) in hatchability of emu eggs due to storage time. Significant differences
(P < 0.0001) were also found in moisture loss due to egg storage. Based on these data, 2 wk of
egg storage appears to be the optimal storage time. After 3 wk of storage, hatchability begins
to decrease.
Key words: emu, egg storage, hatchability
2014 J. Appl. Poult. Res. 23:759–762
http://dx.doi.org/10.3382/japr.2014-01004
DESCRIPTION OF PROBLEM
Emu (Dromaius novaehollandiae) are large
flightless birds and are members of the Ratite
family. They originated in Australia and have
long been raised for their meat and oil. Emu
meat has been shown to be low in cholesterol
and fat [1], and the oil is highly valued because
of its antibacterial, anti-inflammatory, and burn
wound-healing properties [2, 3]. The hatch rate
of emu is much lower than that of other commercial avian species, with reported hatch rates
ranging from 56 to 68% [4, 5]. These very low
hatch rates are an issue for emu producers due
to the fact that emu are expensive to raise and
maintain and have a lower rate of lay in comparison to current commercial poultry. The in1
Corresponding author: [email protected]
creased cost associated with emu production
is attributed to the fact that emu are such large
birds, are slow growing, have a low FCR, long
incubation period, and a very limited season of
lay. However, even with the very high cost associated with raising emu, little research has
focused on areas of emu production, especially with regard to egg storage, incubation, and
hatchability.
Egg storage is a crucial factor to consider
when setting up an incubation program. It has
been found in poultry that no single set storage
time is optimum, and many contributing factors must be considered. Storage time will vary
depending on the age of the bird, differences in
strains, and many other factors [6]. Extended
storage of chicken and turkey hatching eggs has
760
been shown to cause increased embryo mortality [6, 7], decreased hatchability [6, 7], variation
in hatch time [8], decreased egg quality [6], and
increases in pH of the albumen to above optimal levels [9]. However, virtually no research
has been conducted on emu egg storage in comparison to the amount of literature available on
current commercial poultry. Recommendations
vary greatly in regards to temperature, humidity,
and duration; however, many of these practices
come from emu producers and have very little,
if any, scientific basis.
Many factors can alter moisture loss during
storage and incubation and are typically monitored. The age of the flock has been shown to
have a significant effect on shell thickness, pore
length, and pore numbers, thereby increasing
moisture loss [6]. Females from young flocks
have been shown to produce thicker egg shells,
and as the hen ages throughout in her lay cycle
the shells become thinner [10, 11]. The porosity
of eggs is lower in younger birds, but as production increases so does porosity of the egg [10].
Some researchers suggest that humidity levels
during egg storage are not a major factor to consider [12] or that moisture loss is not the cause of
high mortality as a result of long-term egg storage [13]. As many emu producers have mixedage flocks and a lack of uniformity in genetic
lines in comparison to other commercial poultry
producers, most attention appears to be focused
on storage length and storage temperature.
The recommended storage temperature for
the emu egg has a wide range with no specific
target temperature; some sources suggest storage temperatures of 54.4 to 64.4°F [14], but
Brake and Rosseland [15] suggest a storage temperature of 75°F for only 1 d of storage and 55°F
for longer periods of time. Delf and Roseland
[16] suggest initial storage at 69.8°F and gradually reducing the temperature during storage to
59.9°F. Some producers store eggs in normal refrigerators with temperatures ranging from 40 to
60°F [17].
Length of storage is possibly the most disputed factor. Egg storage, even if just over night, is
recommended on all emu eggs, including freshly
laid eggs. Brake and Rosseland [15] suggest that
fresh eggs be stored at 70 to 75°F overnight to
allow for the breakdown of the albumen. Some
sources say that eggs should be stored no lon-
JAPR: Field Report
ger than 7 d [14], yet others suggest eggs can
be stored up to 21 d with minimal decreases in
hatchability. The 21-d storage time is thought to
be similar to what eggs undergo in the wild [15].
However, 28 d of storage is the standard storage
time for most producers, but reports of storage
up to 44 d before incubation have been noted
[17]. The objective of our study was to examine
the effects that storage time may have on hatchability of emu eggs over short or long periods
of time.
MATERIALS AND METHODS
Emu are expensive to raise, and it is difficult
to simulate commercial production; therefore,
our trial was conducted in collaboration with a
local commercial emu producer in North Carolina. The trial consisted of 256 emu eggs that
were hatched in 7 different batches, with batches
ranging from 14 to 81 eggs per set due to incubator and rearing constraints as well as the
irregular laying pattern of the birds. Eggs were
picked up 3 times daily and the condition of the
egg was noted. Each egg was dated, labeled, and
weighed. The eggs were then placed in an egg
cooler that was maintained at 55°F and 60%
RH. Egg weights were then recorded again just
before setting in the incubator, and once more
at 4 d of incubation. All eggs were incubated in
Hatchrite Incubators [18] at 97 to 97.5°F and
RH of 30 to 33% for 49 d. The eggs were then
transferred into a NatureForm hatcher [19] at
97°F and 50% RH.
Hatchability and moisture loss were analyzed
based upon storage times with storage ranging
from 0 to 8 wk. The program JMP Pro 10 [20]
was used to analyze data using the Chi square
and one-way ANOVA features.
RESULTS AND DISCUSSION
Researchers have long studied the optimum
storage time for eggs for commercially raised
poultry [6–8]. In our trial, significant differences
(P < 0.0104) in hatchability of emu eggs were
observed due to storage time (Table 1). Very high
rates of hatch were recorded from eggs that were
stored less than 1 wk, with the mean hatchability
being 90.81%. A slight decrease in hatchability,
85.11 and 69.46%, was noted for eggs that were
Lowman and Parkhurst: STORAGE OF EMU EGGS
stored for 2 and 3 wk, respectively. The hatchability after storage for 1 to 3 wk of age is surprisingly higher than expected when compared
with hatch rates reported previously [5]. These
data are in agreement with Brake and Rosseland
[15] in that emu eggs can be store for up to 3 wk
with minimal loss in hatchability. Majewaska
[5] reported a 1.68% decrease in hatchability per
day for emu eggs that are stored for more than
7 d. Chicken eggs have been said to decrease
hatchability by up to 5% per day when stored
longer than 7 d [8]. Drastic decreases in hatchability (50.46%) were noted for eggs stored 3
wk, dropping to 9.09% hatchability at 8 wk of
storage. These data are very similar to reports
made on chicken and turkey egg storage for the
first 2 wk (storage conditions ranging from 12–
14°C, 60–70% RH) [6, 8], with the exception
that emu eggs can be stored for 3 wk with minimal losses. Storage for this length of time may
be necessary in emu operations due to specific
challenges associated with emu production.
Not surprisingly, a significant (P < 0.0001)
increase in moisture loss from eggs due to storage was observed. These moisture losses ranged
from a mean loss of 2.7% from the eggs stored
less than 1 wk, to 16.20% in the eggs stored for
more than 6 wk (Table 2). The high moisture
loss percentages were not expected, especially
compared with chicken eggs. Zakaria et al. [21]
reported weight losses ranging from 0.41 to
0.53% after 10 d of storage under similar conditions (14–16°C and 60–70% RH). Others reported that eggs stored for 34 d only lost about
1% of weight [13]. Mather and Laughlin [22]
reported weight loss of 0.5% for chicken eggs
Table 1. Length of storage on hatchability of emu eggs
Storage
length, d
0–6
7–13
14–20
21–27
28–34
35–41
42–48
49–55
56–63
a–d
Hatchability,
%
SE
90.82a
85.18ab
69.5abc
50.46bcd
41.00cd
64.29abcd
30.68cd
12.50d
9.09d
8.71
11.52
11.52
13.31
16.29
23.05
16.3
23.05
23.05
Different superscripts among means denote significance
at P < 0.05.
761
Table 2. Storage effect on moisture loss for emu eggs
(%)1
Storage
length, d
0–6
7–13
14–20
21–27
28–34
35–41
42–48
49–63
Moisture
loss
e
2.73
5.62de
7.25cd
9.10bcd
12.00ab
10.00abcd
16.20a
14.50abc
SE
0.82
0.88
0.79
1.00
1.12
1.59
1.42
2.24
a–e
Different superscripts among means denote significance
at P < 0.05.
1
Eggs were stored at 55°F and 60% RH.
stored for 7 d and 1.1% loss in eggs stored 14
d. Several researchers stated that humidity during storage is not a major factor to consider [12]
and that moisture loss is not the cause of high
mortality as a result of long-term eggs storage
in chicken eggs [13]. However, from our trial, it
is evident that weight loss percentages appeared
to be much greater in emu eggs during storage
than in chicken eggs. More research is required
to determine the role that humidity during storage has on emu egg hatchability.
CONCLUSIONS AND APPLICATIONS
1. Optimal hatchability of emu eggs is
achieved when eggs are stored for less
than 7 d.
2. Emu eggs can be stored for up to 3 wk
with minimal decreases in hatchability.
3. Storage of emu eggs for more than 3 wk
causes a significant decrease in hatchability.
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