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The emu (Dromaius novaehollandiae): A review of its biology and commercial products

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Widely distributed throughout the Australian continent, the emu has been hunted by man for thousands of years. Emu farming for oil, meat and skins, both inside and outside Australia, has been seen as feasible from the end of the 1980s. This paper reviews the basic biology of the emu with emphasis on breeding and nutrition before then describing the main commercial products of this species. It is concluded that the emu industry is hampered by a lack of clinical validation of the value of the oil, high costs of production, and inadequate market outlets.
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The emu (Dromaius novaehollandiae): a review of its biology and
commercial products
James Sales*
Institute of Animal Science, Pratelstvi 815, 104 00 Prague Uhrineves, Czech Republic
ABSTRACT
Widely distributed throughout theAustralian continent, the emu has been hunted by man for thousands of years. Emu farming
for oil, meat and skins, bothinside and outsideAustralia, has been seen as feasible from the end of the 1980s.This paper reviews
the basic biology of the emu with emphasis on breeding and nutrition before then describing the main commercial products of
this species. It is concluded that the emu industry is hampered by a lack of clinical validation of the value of the oil, high costs
of production, and inadequate market outlets.
Keywords: emu, ratite, breeding, marketing
1. INTRODUCTION
Emus have been hunted by humans, certainly been
the emu’s greatest predator since the Middle Upper
Pleistocene (Boland, 2003), for over 60,000 years
throughout much of inland Australia (Kirk, 1981). In
addition, emus have often been the targets of persecu-
tion by European settler pastoralists, such as the
infamous ‘Emu Wars’ staged in 1932 in Western
Australia (Breckwoldt, 1983). Despite an attempt in
1970 to farm emus in Western Australia for leather
production, emus were only recognised as an agricul-
tural commodity in Australia in 1987 (Drenowatz
et al., 1995). Since, it has become popular on farms
with notable flocks in the USA, Europe, Asia
(O’Malley, 1995) and in Africa. A great deal of
popular literature that is available to existing and
potential investors in the emu as a farm animal is
not scientifically sound. Furthermore, much of the
existing scientific literature about the farmed emu is
fragmented, and difficult to interpret. This manuscript
briefly reviews the biology of the emu, then describes
its characteristics that contribute to its potential as a
production animal.
2. BIOLOGY
2.1 Systematics and genetics
The family Dromaiidae is restricted to a single extant
species, Dromaius novaehollandiae, which is one of
the most characteristic components of the modern
Australian avifauna. The three living subspecies are
Dromaius novaehollandiae novaehollandiae in
Central and South Queensland, Victoria and
Southern Australia, Dromaius novaehollandiae wood-
wardi in Northwestern and Western Australia and the
Northern Territory, and Dromaius novaehollandiae
rothschildi in Southwestern Australia (Howard and
Moore, 1984). The Tasmanian population, possibly
specifically distinct, and two dwarf species,
Dromaius baudinianus on Kangaroo Island and
Dromaius ater on King Island, have gone extinct
within the past 200 years (Boles, 2001). Fossil
records of emus were reviewed by Patterson and
Rich (1987). Although emus are distributed
throughout most of Australia, they avoid heavily
populated areas, dense forest and arid areas
(Davies, 1963).
Most cladistic analyses using skeletal, molecular and
oological data agree on a close relationship between
cassowaries and emus (Zelenitsky and Modesto, 2003).
Phylogenetic analyses indicate that ostriches (Africa)
are basal and rheas (South America) cluster with living
Australasian (emu, cassowary and kiwi) ratites (Van
Tuinen et al., 1998). In Australia, although conducted
on a limited number of populations, total gene diver-
sity, both on farms and from wild populations, was
found to be high (0.79 – 0.89), and general agreement
between expected and observed heterozygosity values
suggested that populations were not inbred (Hammond
et al., 2002).
Avian and Poultry Biology Reviews 18 (1), 2007, 1 – 20
*To whom correspondence should be addressed: E-mail: James_Sales_1@hotmail.com doi: 10.3184/135704807X222531
In the emu, where 4.48% of the genome was probed
with 23 microsatellites (Roots and Baker, 2002), nine
macrochromosomes show remarkable homology with
those of the domestic chicken, indicating strong conser-
vation of karyotype through evolution (Shetty et al.,
1999). The sequence of the gender determining gene
DMRT1 from the emu has 88% homology with chicken
DMRT1, and 65% with human DMRT1 (Shetty et al.,
2002).
2.2 Behaviour
As emus do distribute large quantities of seeds, and
might also play an important role in facilitating germi-
nation of the seeds, they could prove an important link
between fragments of remnant vegetation by helping to
maintain the genetic mix in plant communities (Noble,
1975; Rogers et al., 1993; McGrath and Bass, 1999).
Although wild emus in Western Australia have been
viewed as essentially solitary or pair-living, groups of
more than three birds have often been reported (Long,
1959; Pople et al., 1991; Coddington and Cockburn,
1995; Hough et al., 1998; Boland, 2003). Hough et al.
(1998) found that overall vigilance was unaffected by
group size in wild emus, with birds spending more time
vigilant early in the day. However, Boland (2003)
reported that, similar than in ostriches (Bertram,
1980) and rheas (Martella et al., 1995), vigilance
decreased as group size increased.
When frightened by a predator or other potential
threat, emus typically flee by running at speeds
approaching 50 km h
1
(O’Brien, 1990). Captive adult
emus, both in the Northern and Southern hemisphere,
spend most of their time during daylight hours on either
sitting (28 – 24%) or standing (22 – 28%). A lot of
sitting is done in a crouching position, even to
perform activities such as drinking, preening and
pecking (Sales and Horban
˜czuk, 1998a).
2.3 Anatomy
Female emus attain a weight of 55 kg and height of
1.8 m, compared to 38 kg and 1.5 m, respectively, for
males (Fowler, 1991). Together with successful digital
methods and the use of a fibre optic proctoscope to sex
young and adult emus (Samour et al., 1984), a reliable
two-primer cleaved amplified polymorphics sequence
assay has been developed for reliable sex identification
of the emu (De Kloet, 2001).
The feathers of the emu are, similar than those of the
cassowary, double, each with an after shaft almost
equal in length to the main feather. No oil gland is
found (Pycraft, 1901). The wings, with a single clawed
digit (Maxwell and Larsson, 2007), are tiny stub-like
appendages that hang from the anterior region of the
body. Leg feathering ends slightly above the tibiotarsal-
metatarsal joint (Cho et al., 1984).
Emus have 54 vertebrae in the axial skeleton,
compared to 56 in the ostrich (Mivart, 1877).
Contrary to two digits in the ostrich foot, the emu
foot, similar to the rhea and cassowary, has three
digits (Fowler, 1991).
The tongue has a serrated edge (Cho et al., 1984), and
the flexible cartilaginous tracheal rings are interrupted
by a 6 to 8 cm long cleft on the ventral surface. Whereas
a thin membrane covers the cleft in the chick, an
expandable pouch of approximately 30 cm long forms
cranial to the cleft as the bird matures. When air is
directed into the pouch the skin of the neck expands and
a booming sound by the female, and growling sound by
the male, is produced (Murie, 1867; Cho et al., 1984;
Fowler, 1991).
Compared to a tan colour in cassowaries, ostriches
and rheas, gonads are black in the emu (Cho et al.,
1984). The epididymis is, as in ostriches and rheas,
subdivided into a main part and an appendix epididy-
midis (Budras and Meier, 1981). Lymph heart myocytes
in emus, like in ducks and rheas, slowly but progres-
sively differentiate a cytomorphology that resembles in
some aspects smooth muscle during development
(Budras et al., 1987).
Intrapulmonary chemoreceptors in the paleopulmonic
lung of the emu exhibit similar characteristics to those
in birds that possess varying amounts of neopulmonic
parabronchi, such as the duck and chicken (Burger et al.,
1976a,b). Although the wet weight of the heart of the
emu is approximately 30 times that of the domestic
chicken, the time course of atrial and ventricular
activation is identical (Goldberg and Bolnick, 1980).
2.4 Physiology
Basal metabolic rate of emus is only 61 – 79% (Buttemer
and Dawson, 1989; Maloney and Dawson, 1993) of the
rate predicted by the equation reported by Aschoff and
Pohl (1970) for non passerine birds and varies according
to gender. Although body weight was similar (37.0 and
39.7 kg, respectively), metabolic rate differed between
males (2.53 ml O
2
kg
1
min
1
) and females (3.08 ml
2James Sales
O
2
kg
1
min
1
) in winter. However, in summer body
weight differed between males (40.7 kg) and females
(45.5 kg), whereas a lower basal metabolic rate was
maintained in males (2.42 versus 2.95 ml O
2
kg
1
min
1
). Maloney and Dawson (1993) speculated
that this could be related to a reduction of basal
metabolic rate by males during the inactive incubation
period. Mean respiratory and heart rate of 7.1 breaths
min
1
and 41 beats min
1
, respectively, have been
reported for resting emus of 38.3 kg body weight
(Crawford and Lasiewski, 1968). Grubb et al. (1983)
reported cardiac output of 67.9 ml kg
1
min
1
, blood
pressure of 149.3y116.2 mmHg, and stroke volume of
1.52 ml kg
1
for emus with a similar to above body
weight.
Body temperatures for males were 37.7
C in both
summer and winter, and 38.3
C and 38.2
C in summer
and winter, respectively, for females (Maloney and
Dawson, 1993). Body temperature of incubating male
emus (37.8
C) varies less throughout the incubation
period than that of non-incubating birds (Buttemer and
Dawson, 1989). Emus are able to maintain a constant
body temperature within the ambient temperature range
of 5to45
C. During a falling ambient temperature
the emu regulates its body temperature initially by
reducing conductance and then by increasing heat
production, whereas cutaneous evaporative water loss
in addition to panting are used during high ambient
temperatures (Maloney and Dawson, 1994a).
Morphometric and physiological observations of the
lung of the emu suggest that this bird has a relatively
low demand for oxygen, consistent with the evolution
of a bird of relatively large body mass and low surface
area, in a warm environment, and with few effective
predators (Maina and King, 1989). An increased meta-
bolic demand for oxygen at low ambient temperatures
is achieved in the emu by a combination of a higher
tidal volume and oxygen extraction. At higher ambient
temperatures ventilation is increased through a higher
respiratory frequency to facilitate respiratory water loss
(Maloney and Dawson, 1994b). During a 3 – 4 hour
heat stress created by increasing ambient air tempera-
ture from 21 to 46
C emus intensified their respiratory
frequency from 5.3 to 52.9 breaths min
1
.
Exceptionally the emu is not susceptible to the respira-
tory alkalosis that overtakes most other birds after
prolonged panting when heat stressed (Jones et al.,
1983). Beak, lower leg, neck, foot and toe surface
temperatures are controlled in emus to alter heat
exchange with the environment (Phillips and
Sanborn, 1994). Resultant heat from absorption of
radiation close to the surface of the plumage of the
emu is prevented from flowing to the skin by the coat’s
insulation (Maloney and Dawson, 1995).
Osmoregulation, defined as the turnover of water and
homeostasis of water and the major electrolytes of
plasma and extracellular fluids, has been extensively
studied in the emu (Dawson et al., 1983, 1984, 1985,
1991; Skadhauge et al., 1991; Thomas, 1997). Body
hydration status is about 61% of body weight, with a
water turnover of 45 ml kg
1
d
1
in hydrated emus
(Dawson et al., 1983). Although the emu has a limited
ability to concentrate urine, with a maximal urine to
plasma osmotic ratio of only 1.4 to 1.5, the capacity of
its cloaca-rectum to absorb water and sodium chloride
is considerable. Furthermore, the kidney is efficient at
recovering water and electrolytes (Dawson et al.,
1991). During incubation the male gained water
through drinking surface water, preening of rain-
soaked feathers, direct and indirect intake of water
from food through water content and oxidation, respec-
tively, and metabolic water formation from oxidation
of the bird’s energy stores (Buttemer and Dawson,
1989).
Similar to ostriches, thyroid function is abnormally
low in emus compared to other avian species, and may
explain neotenous characteristics of ratites. Thyroxine
concentrations increase during the last weeks of incu-
bation to stay, together with tri-iodothyronine, high
during the first 3 days of life, whereafter it falls to a
constant low level. Plasma concentrations of growth
hormone are high at the time of hatching and decrease
gradually over the first 22 weeks of life, whereafter
concentrations are variable, similar than in other bird
species (Blache et al., 2001a).
3. REPRODUCTION
3.1 Sexual behaviour and egg laying
Although the mating system of emus has previously
been assumed as monogamous (Davies, 1972, 1976;
Handford and Mares, 1985), more recent research
(Coddington and Cockburn, 1995) indicates mono-
gamy, sequential polyandry and promiscuity.
Furthermore, serial polyandry had earlier been reported
in captive emus (Fleay, 1936; Kendeigh, 1952; Curry,
1979; O’Brien, 1990). The social mating system of the
captive emu is mainly of a monogamous type, but a
few males will be promiscuous before they start
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 3
incubating. This is also true for some females after
their mate has started incubating. In addition, there are
significant numbers of extra-pair copulations
(Coddington and Cockburn, 1995; Blache et al.,
2000). Although the last male to mate does not
always fertilise all of the eggs that are subsequently
produced, for inseminations one week apart, last-male
precedence is dominant in emus (Taylor et al., 2000a).
Intra-specific brood parasitism has been proven with
the use of molecular markers in the emu. Of 106 chicks
sampled during one breeding season in Australia, 51%
were not fathered by the male that incubated them
(Taylor et al., 2000b).
The emu is a prolific breeder with an annual
reproductive cycle, both in the wild and captivity, in
which egg-laying and sperm production start in the
autumn and last until spring before food resources
become limited by the start of the dry season
(Davies, 1976; Malecki et al., 1998). Photoperiod is
the main controlling factor in the timing of the
breeding season (Blache et al., 2001b; Sharp et al.,
2005). Dissipation of photorefractoriness by short days
in autumn increases secretion of gonadotrophins to
levels that are sufficient to support full reproductive
condition in the emu, resulting in the initiation of
breeding. An increase in prolactin secretion, which,
unusually for birds, increases in emus while the days
are still short, might play an important role in the
termination of the breeding cycle (Blache et al., 2001b;
Sharp and Blache, 2003).
Although adult emus are generally quite docile when
often handled by humans, they could become more
aggressive during the breeding season (Long, 1959;
Davies, 1976). Both sexes vocalise strongly, and fluff
out the feathers on the front of the neck in commu-
nicative postures (Fleay, 1936; Curry, 1979;
Coddington and Cockburn, 1995), with often curving
their necks into a slight S-shape. When they identify
with each other, they will raise their heads, and males
may attempt to follow the female and place their heads
over the female’s back. Signs showing interest by
females include a gradually lowering of the head,
raising of the tail, and crouching into the mating
position (Malecki, 1993).
The male starts incubating as soon as 5 to 10 eggs are
laid for a period of around 56 days (Gaukrodger, 1925;
Long, 1959; Davies, 1976), during which he might lose
17 to 20% of his body weight (Dawson et al., 1984).
Female emus can store viable sperm in their reproduc-
tive tract for up to 21 days, allowing them to continue
to lay fertilised eggs after their partner has started
incubating and consequently lost his sexual drive
(Malecki, 1997). It is suggested, based on an increase
in sperm concentration in the outer perivitelline layer
of the egg, that emus copulate weekly rather than daily.
Whereas male fertility can be influenced by season and
egg incubation, female fertility will continue as long as
she is supplied with sperm on a weekly basis, as the
frequency of sperm supply is sufficient to compensate
for the rate of sperm lost from the oviduct (Malecki and
Martin, 2002a). A mean number of 25.3 eggs per
female for a season, with the spread of laying 83.8
days, starting in April, reaching a peak in June and
finishing in September, have been reported for a
captive population of emus in Western Australia.
Clutch size was 6.7 eggs, with 3.4 clutches per
female over the laying season. Most eggs were laid at
3 day intervals with an inter-clutch period of 6.4 days.
Females laid fertilised eggs for 6 to 24 days after
natural or artificial insemination, with a fertile period,
estimated from clutch size and egg interval, of 20.1
days (Malecki and Martin, 2002b).
For the purpose of artificial insemination two
methods for collecting semen from male emus with
the use of an artificial cloaca have been developed. A
semen collector stimulates erection and subsequent
ejaculation using the artificial cloaca when the male
mounts a female teaser in the first method. In the
second method males are trained to development
sexual behaviour towards the semen collector, and
semen is collected when the male mounts the collec-
tor’s back (Malecki et al., 1997a). In experiments on
the influence of collection frequency (every 1, 2 or 4
days for 16 days; once, twice or three times daily for 6
days) on semen collection, the mean ejaculate had a
volume of 0.61 ml (range 0.27 – 1.39). It contained
1.94610
9
sperm (range 0.71 – 4.75) at a concentration
of 3.34610
9
sperm ml
1
(range 1.81 – 4.67). Over a 6
day period twice-daily collection produced the highest
output of semen volume (5.8 ml) and number of
spermatozoa (19.8610
9
), compared to collection at
one or three times a day (Malecki et al., 1997b).
During twice weekly semen collection at twice a day
over an 8 week period from July to September in
Australia production of semen and spermatozoa
declined (Malecki et al., 2000). Based on objective
evaluation of membrane integrity and fertilising ability
(Malecki et al., 2005a), emu spermatozoa could be
stored undiluted at 20
C for up to 6 hours. However,
for storage at 4
C, spermatozoa needed to be diluted,
4James Sales
and could also only be stored for up to 6 hours
(Malecki et al., 2005b).
3.2 Egg, incubation and rearing
Characteristics of the emu egg are presented in Table 1.
According to Vleck et al. (1980), the relative low water
vapour conductance, 51.8 mg d
1
Torr
1
(Ar et al.,
1974), might be an adaptation to prevent excessive
water losses during incubation in the semi arid and arid
regions of Australia. However, Buttemer et al. (1988)
suggested the reflection of a set point for total water
loss similar to that associated with optimal hatchability
in chickens.
The green colour of the emu eggshell is attributed to
the methyl ester of the pigment biliverdin IXa(Tixier,
1945). Emu eggshell consists of a black or very brown
granulated outside layer, thin white fibrous layer, thick
green spongy layer, and white mammillary inner layer
(Tyler and Simkiss, 1959). Contradictory to egg shells
from other avian species pores do not traverse the shell
of the emu egg directly, but vent into a plexus of
channels running just under the outer surface of the
shell, which open independently via short pores to the
atmosphere (Board and Tullett, 1975). The eggshell
consists of 95% calcium carbonate in the form of
calcite (Mann, 2004). Comparable to ostrich and
rhea, and contradictory to chicken and goose, the
emu eggshell matrix contains two different C-type
lectin-like proteins as major components, indicating
that the occurrence of these proteins might be wide-
spread among ratites (Mann, 2004).
Chemically, albumen has 0.05% lysosome whereas
sialic acid content is 3.1%, compared to values of 3.4
and 0.29%, respectively, in the egg white of the
domestic hen (Osuga and Feeny, 1968). Time for
deposition of yolk in the emu egg varied from 25 to
28 days, with 31 to 39 days between the onset of yolk
deposition and oviposition (Hirsch and Grau, 1981).
Oxygen consumption of the emu embryo increases
exponentially during the first 70% of incubation, and
reaches a maximum value of 97.5 ml h
1
at day 38 and
thereafter it declines. This decline was interpreted by
Vleck et al. (1980) as the completion of growth.
However, oxygen consumption increases again just
prior to pipping (first breaking of the shell) at day 49.
The time between pipping and hatching was found to
be 18.5 hours (Vleck et al., 1980). Mean heart rate of
embryos decrease from about 175 bpm at 75% of
incubation to about 140 bpm at 95% (Tazawa et al.,
2000). The physiological capacity for endothermy of
the emu develops prior to hatching (Dzialowskia et al.,
2007).
Temperatures of naturally incubated eggs rise stead-
ily from 32 to 34
C over the first 10 days of
incubation, remain at 34
C for the next 15 days,
and gradually rise to 36
C by day 35 to remain
there until hatching time. These differences in egg
temperature resulted in an increase in water losses
from 907 mg day
1
during the first 25% of incubation
to 1,243 mg d
1
at day 39. Both egg temperature and
embryo development was inversely related to thermal
sensitivity of embryonic oxygen consumption. It was
postulated by Buttemer et al. (1988) that the pattern of
rising incubation temperatures aid in hatching synchro-
nisation for all members of a clutch. According to Ar
and Rahn (1980) avian eggs, irrespectively of incuba-
tion period and fresh egg weight, lose on average 15%
of their initial weight during incubation. However,
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 5
Table 1 Emu egg and embryo characteristics (Tyler and Sim-
kiss, 1959; Ar et al., 1974; Van Vleck et al., 1980; Beutel et al.,
1983; Buttemer et al., 1988; Szczerbinska et al., 1999;
Dzialowski and Sotherland, 2004; Reddy et al., 2004; Majewska,
2001)
Component Values
Egg
Weight (g) 450 to 637
Length (mm) 130 to 290
Breadth (mm) 90 to 102
Shape index 35.2 to 66.07
Volume (cm
3
) 572
Egg surface area (cm
2
) 337
Specific gravity 1.290
Water vapour conductance (mg d
1
Torr
1
) 45.7 to 51.8
Shell thickness (mm) 0.45 to 1.10
Shell weight (%) 13 to 18
No pores cm
2
eggshell 39.4
Porosity (mgH
2
O loss d
1
cm
2
) 2.37
Albumen index 0.179
Albumen weight (%) 29 to 47
Moisture (%) 88.67 to 90.84
Protein (%) 9.16 to 9.58
Fat (%) 0.38
Ash (%) 0.73 to 1.71
Yolk index 0.171
Yolk weight (%) 41 to 53
Moisture (%) 43.15 to 45.86
Protein (%) 15.54
Fat (%) 35.84 to 38.16
Ash (%) 1.78 to 1.96
Embryo (day 46)
Metabolic rate (ml O
2
h
1
) 107.8
Hatchling
Weight (g) 393 to 414
Yolk-free weight (g) 301
naturally incubated emu eggs lost only about 10% of
their initial weight during the incubation period, attrib-
uted to the low water vapour conductance already
described (Buttemer et al., 1988).
Although a higher incubation temperature shortened
the duration of artificial incubation, it decreased hatch-
ability and increased the percentage of dead embryos
(Table 2). Hatchability, as a percentage of eggs set, was
68.3, 55.3 and 56.0% for 113 emu eggs stored before
artificial incubation for 7, 14 or 21 days, respectively.
Corresponding values for dead embryos were 22.0,
31.9 and 32.0%, respectively (Majewska, 2001). It
was found by Bowthorpe and Voss (1968) that a
captive male emu turned the eggs from 2 to 4 times a
day.
Emu chicks are precocious and become ambulatory
within 2 days after hatching. This results in attending
males in the wild shifting duties from egg incubation to
rearing the chicks (Buttemer et al., 1988). In a zoo
environment (Bowthorpe and Voss, 1968), it was
necessary to coax the first chicks born to start eating.
Studies are needed to determine the emergence and
occurrence of a pecking order in emu chicks and their
relationship to growth (Elston et al., 1998).
4. NUTRITION
Similar to other ratites (Sales, 2006), emus have
exceptionally slow growth rates relative to other
domestic poultry species, such as broiler chickens
(Table 3). According to the model illustrated in
Table 3 emus would reached a body weight of about
40 kg, established by the industry as the slaughtering
point, at 584 days. Due to an increase in maintenance
requirements cost per unit of gain increases after the
point of inflection, which can be described as the point
of highest growth velocity (Goonewardene et al.,
2003). Emus are slaughtered at 497 days beyond this
point (Table 3).
Literature on the anatomy of the digestive tract of the
emu and food selection in the wild has been compared
to that of the ostrich by Angel (1996), O’Malley
6James Sales
Table 2 Hatching performance at different incubation temperatures (Szczerbin
˜ska et al., 2003)
Component 36.4C 36.7C 37.1C
Eggs set 66 62 51
Weight (g) 662.9 670.3 650.8
Fertility (%) 93.9 87.1 88.2
Weight loss (%) 13.8 13.4 13.4
Hatchability of eggs set (%) 71.2 58.1 49.0
Dead embryos (%) 13.7 25.8 25.5
Hatched chicks 47 36 25
Assisted chicks 4 2 1
Duration of incubation (days) 51.5 51.1 49.4
Weight of chicks (g) 446.8 463.8 428.0
Deaths until 3 weeks of age (%) 4.3 8.0 2.8
Table 3 Growth characteristics of emus (1 to 240 days) compared to broilers (1 to 42 days) based on the
Richard’s (y
t
¼A(1be
-kt
)
m
) model (Goonewardene et al., 2003)
Parameter Symbol Units Emu Broiler
Asymptote (mature weight) A kg 49.5 4.6
Constant b 0.965 0.106
Maturing rate k d
1
0.0037 0.0463
Shape parameter m 1.53 44.34
Time of inflection T
I
d 105 32
Weight at inflection W
I
kg 9.8 1.7
Absolute growth rate AGR g d
1
68.4 54.0
Absolute maturing rate AMR d
1
0.0014 0.0017
Relative growth rate RGR g d
1
0.0107 0.0474
Degree of maturity at T
I
UT
I
% 19.8 36.3
A¼asymptote or mature weight when time (t)!1;b¼an integration constant; k ¼coefficient of relative growth
also called a maturing index establishing the rate at which weight (Wt) approaches the mature weight A;
m¼shape parameter that determines the time of inflection (T
I
) and the weight at inflection (W
I
);GR ¼the first
derivative of the function with respect to age (dWtydt); AMR ¼the instantaneous growth rate relative to the mature
weight A; RGR ¼instantaneous growth rate relative to current weight; UT
I
¼degree of maturity at inflection (T
I
).
(1995), and Sales (2004), and to that of all other extant
families of ratites (ostrich, rhea, cassowary and kiwi) by
Sales (2006). High fibre digestibility (35 – 45% of
neutral detergent fibre) and contribution of fibre diges-
tion to energy requirements (50% of maintenance
requirements) had been reported in adult emus (Herd
and Dawson, 1984). However, the emu’s digestive
system lacks special digestive adaptations (huge caeca
or colon) needed for fibre fermentation. Whereas the
colon represents 54.9% of the length of the total
digestive tract in the ostrich (O’Malley, 1995), it is
only 6.5% of total length in the emu (Table 4). The
caecum length of a male rhea (25 kg body weight) was
found to be 0.48 m, compared to a value of 0.12 m
reported for emus (Table 4). The structure of the
digestive tract of the emu (Table 4) is more comparable
to that of the domestic chicken, with values of 78 and
6% for the small intestine (dueodenum, jejunum and
ileum) and colon as proportion of total digestive tract
length, respectively (Feltwell and Fox, 1978), than to
ostriches and rheas. A further inconsistency to the
reported high fibre digestibility is the rapid intestinal
passage of 5.5 h of digested plant particulate matter in a
compound diet (Herd and Dawson, 1984), although
some food items such as seeds may stay for up to a
week in the digestive tract of the emu. The latter
illustrates that gut retention times depend in part on
the nature of the item ingested (Wilson, 1989). Indeed,
Farrell et al. (2000) found that dry matter digestibility
and metabolisable energy values of diets containing
different fibre sources were similar between emu chicks
and adult cockerels (Table 5). The diet containing
lucerne showed a higher digestibility of dry matter
and metabolisable energy value for the 4.5-month old
emus than for older birds, with all other diets presenting
similar values between age groups.
Depending on season, wild emus consume high
quality shrubs, annual grasses, and insects in inland
Western Australia, without any preference for dried
herbage or grass and mature leaves of shrubs (Davies,
1978). Habitat usage in the wild appeared to be related
to availability of food and water, and to a lesser extent,
shelter (Quin, 1996). Compared to the domestic
chicken, low maintenance requirements for nitrogen
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 7
Table 4 Dimensions of the digestive tract and characteristics of gut contents of wild adult (body weight
of 36 kg) emus (Herd and Dawson, 1984)
Component Dimensions Gut contents
Length (m) % of total length Osmolarity (mOsm kg
1
)pH
Oesophagus 0.76 17.1 340 6.8
Proventriculus 0.14 3.1 328 2.8
Gizzard 0.11 2.5 290 2.5
Duodenum 0.50 11.2 681
a
6.7
a
Jejunum 1.23 27.6
Ileum 1.42 31.9 367 8.2
Cecum 0.12 –
Colon 0.29 6.5 323 7.2
a
Duodenum þjejunum.
Table 5 Dry matter (DM) digestibility coefficients and apparent metabolisable energy (AME) of diets with different roughage sources
compared between emus and adult cockerels (Farrell et al., 2000)
Diet Emus Cockerels
Chicks Juveniles
(4.5 months, 11 kg body weight) (9 months, 21 kg body weight)
DM AME
(MJ kg
1
DM)
DM AME
(MJ kg
1
DM)
DM AME
(MJ kg
1
DM)
Basal 0.79 15.65 0.74 14.88 0.73 14.96
Basal þpollard 0.64 12.78 0.72 14.51 0.69 14.15
Basal þlucerne 0.65 12.79 0.54 11.08 0.69 14.04
Basal þrhodes grass 0.62 12.32 0.64 12.86 0.65 13.12
Basal þwheat straw 0.65 12.85 0.64 12.83 0.61 12.63
(0.09 versus 0.34 g kg
0.75
d
1
) and energy (284 versus
405 kJ kg
0.75
d
1
) is probably related to a low basal
metabolism and some form of urine nitrogen recycling
(Dawson and Herd, 1983). As a guideline for possible
feed formulation, the amino acid requirements of
growing emus have been estimated at age intervals
with the use of a mathematical model utilised for
commercial poultry production by O’Malley (1996),
and compared to values determined with ostriches by
Sales (2004, 2006). According to this model a lysine
requirement of 0.76 g lysine MJ
1
metabolisable
energy for 3 to 4 week old emus has been estimated
(O’Malley, 1996). This is lower than a dietary lysine
value of 0.83 – 0.90 g MJ
1
metabolisable energy been
found as optimal for maximum growth rate and
minimum food conversation ratio in young growing
(23 – 65 days) emus (Mannion et al., 1999). Results
(Blake and Hess, 2004) indicate that a dietary concen-
tration of 14% protein failed to support maximum
growth (Table 6). However, birds fed the 14%
protein diet showed compensatory growth, as indicated
by the highest body weight gain during days 135 to 176
days of growth. Although absolute carcass weight was
higher in females than males, neither dietary protein
level nor gender had any effect on carcass yields.
Decreasing the selenium content of a commercial
emu breeder diet from 1.55 to 0.52 ppm increased egg
production by 23%, and there was an overall reduction
in leg deformities in chicks (Kinder et al., 1995).
Encephalomalacia, characterised by backward stag-
gering, lack of coordination, general weakness, and
sitting on hocks with heads retracted backwards, had
been associated with vitamin E deficiency in emus
(Aye et al., 1998).
Dawson et al. (1984) showed that emus devote a
large proportion of their time to active feeding early in
the day. Food intake of emus in the wild and on farms
in Australia increases at the end of the breeding season
(O’Malley, 1996; Blache and Martin, 1999), during
which body fat reserves lost during the winter are
quickly replaced (Davies, 1978). Glatz (2001) found
that feed withdrawal resulted in birds being more
restless and aggressive towards each other compared
to birds with food available.
Emus can remain in water balance without drinking
only if the food has a high (50 77%) water content
(Dawson et al., 1983). According to Maloney and
Dawson (1998) adult emus ceased food intake by the
fourth day of water restriction. The major part of the
water from the kidneys and ileum can be reabsorbed in
the lower gut on both high and low sodium chloride
intake. An apparently high transport capacity of the
lower gut is aided by a high degree of folding of the
mucosal surface (Skadhauge et al., 1991).
5. PRODUCTS
Ever since the start of the development of the commer-
cial emu industry around 1990 most of the attention
focused on oil production and its potential use in the
cosmetic, pharmaceutical and medicinal industries.
However, emus are also valued for their low-fat red
meat, and hides in making of leather products. Other
potentially marketable emu products include feathers,
eggs, egg shells, toenails, bones, and manure
(Fronteddu, 2001).
5.1 Oil
Emu oil is derived from both retroperitoneal and
subcutaneous adipose tissue sites (Yoganathan et al.,
2003). The native Aboriginal and early white settlers in
Australia used the liquid fat from emus to facilitate
wound healing and discomfort from musculo-skeletal
8James Sales
Table 6 Body weight and feed consumption of emus fed varying levels of dietary protein (Blake and Hess, 2004)
Measurement Dietary protein Day of experimental period
level (%)
15 30 43 79 108 135 176 248
Body weight (kg) 14 12.04 13.77 15.03 18.24 21.77 24.04 28.37 35.23
16 12.56 14.42 16.06 19.82 23.72 26.42 30.52 38.08
18 12.34 14.25 15.88 19.65 23.11 25.85 29.12 36.29
Feed consumption (kg) for period 14 5.48 7.98 6.90 17.40 23.08 18.75 33.14 81.81
16 6.07 8.45 7.86 18.64 22.86 21.41 36.74 80.95
18 5.86 8.48 7.17 17.99 22.61 18.10 33.16 78.25
Seventy-two emus (mean age 107 days) were randomly distributed among six pens (4.2624.2 m) with 12 birds pen
1
. Two pens each were fed either a
14, 16, or 18% protein (11.97 MJ kg
1
metabolisable energy) maize-soybean meal diet from day 0 to 176. From day 176 to 273 a 14% protein finisher
diet containing either 11.97 MJ kg
1
or 12.90 MJ kg
1
metabolisable energy was fed to each of two pens fed the same protein level prior to day 176.
disorders. Rendering procedures of emu fat at tempera-
tures up to 15
C produced a thick oil, that can be
cleared (approximately 80% vyv) by filtering at 2
C
(Whitehouse et al., 1998).
The fatty acid composition of fat from two different
regions in the emu is shown in Table 7. Higher values
than reported in Table 7 were reported for emu oil
supplied by a commercial producer (Fukushima et al.,
1999) for the ratio of n-6 to n-3 (13.7) and polyunsa-
turated to saturated (0.7) fatty acids. Differences in
fatty acid composition of oil due to type of adipose
tissue, dietary fat and gender have been reported
(Beckerbauer et al., 2001). The a-linolenic acid
(C18 :3n-3) content in the total triglyceride fraction
varies from almost zero in many farmed birds, up to
20% in some feral birds, reflecting the influence of the
diet on oil composition (Whitehouse et al., 1998).
In a double blind clinical study by Zemtov et al.
(1996), emu oil was found to be more cosmetically
acceptable with better skin penetrationypermeability
compared to mineral oil. The latter ability to penetrate
easily through the stratum corneum barrier might be
explained by the high concentration of non-polar
monounsaturated fatty acids in emu oil. Furthermore,
it appears that emu oil has better moisturising proper-
ties and superior texture compared to mineral oil.
However, 18% of the participants in the study by
Zemtov et al. (1996) found emu oil to cause pimples,
that does not support the claim that emu oil is non-
comedogenic. Rather, it shows emu oil to have a low
incidence of comedogenicity (Fronteddu, 2001).
Compared to coconut oil, crude and refined emu oil
at 10% dietary inclusion lowered plasma total choles-
terol and low-density lipoprotein, and aortic choles-
terol ester concentrations, with no difference in
plasma high-density lipoprotein or triacylglycerol, in
hypercholesterolemic hamsters. This demonstrates that
emu oil is capable of reducing aortic early athero-
sclerosis in this species (Wilson et al., 2004).
However, a commercial emu oil, containing about
15% linoleic acid (C18 :2n-6), and included at 5%
in a cholesterol-enriched diet, has the same effect on
serum and liver cholesterol levels of rats as dietary
beef tallow and lard (Fukushima et al., 1999).
Twice-daily application of emu oil lotion (mixture of
emu oilyfat, vitamin E, and botanical oil) immediately
after creation of full-thickness skin defects till day six
delayed wound healing in rodents. However, adminis-
tration of oil 48 hours after defect creation caused a
two-fold promotion of wound contraction, epitheliali-
sation, and infiltration of organised granulation tissue.
No such effects were exerted by pure emu oil, furasin,
cortaid, or polysporin. Although the mechanism
responsible for the above beneficial effects of emu oil
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 9
Table 7 Fatty acid composition (% of total fatty acids) of emu fat and meat (Wang et al., 2000)
Fatty acid Fat Meat
Abdominal Back
C14 :0 0.45 0.36 0.40
C16 :0-isomer ND ND 3.95
C16 :0 22.40 21.51 18.48
C18 :0 8.25 9.11 10.42
SFA 31.20 30.97 33.30
C16 :1 4.37 3.31 3.49
C18 :1n-9 48.31 49.91 34.97
C18 :1n-7 2.35 2.10 2.66
C20 :1 0.54 0.49 0.16
MUFA 56.00 56.19 41.95
C18 :2n-6 11.38 10.95 15.19
C20 :4n-6 ND 0.14 5.37
n-6 PUFA 11.52 10.99 21.17
C18 :3n-3 1.86 1.79 1.31
C20 :5n-3 ND ND 0.41
C22 :5n-3 ND ND 0.47
C22 :6n-3 ND ND 0.88
n-3 PUFA 1.86 1.79 3.07
PUFA 13.45 12.77 24.08
n-6 :n-3 6.39 6.33 6.97
P:S 0.43 0.42 0.72
SFA ¼saturated fatty acids; MUFA ¼mono-unsaturated fatty acids; PUFA ¼polyunsaturated fatty acids; P:S ¼ratio of
polyunsaturated to saturated fatty acids; ND ¼not detected.
lotion remains to be determined, anti-inflammatory,
anti-catalytic, mitogenic and lipophilic properties
might be possible (Politis and Dmytrowich, 1998). It
was found that treatment with emu oil improved
consequences of burns caused by fire or hot water
that had affected 5 to 60% of the bodies of 125 children
(Lagniel and Torres, 2007).
Block et al. (1996) stated that oils rich in the n-9 fatty
acid, oleic acid (C18 :1n-9), and the n-3 fatty acids,
such as a-linolenic acid (C18 :3n-3), eicosapentaenoic
acid (C20 :5n-3), and docosahexaenoic acid (C22 :6n-
3), are associated with anti-inflammatory activity when
compared to the proinflammatory actions of the n-6
fatty acid, linoleic acid. Emu oil contains significantly
less of the above reported anti-inflammatory fatty acids
than is found in olive oil, flaxseed oil and fish oil
(Yoganathan et al., 2003). However, swelling and
oedema due to auricular inflammation induced by
croton oil in mice were significantly reduced within
12 hours of treatment with either emu or porcine oil
(Lo
´pez et al., 1999). Furthermore, tissue concentrations
of two different cytokines, interleukin (IL-1a) and
tumor necrosis factor-a(TNF-a), that are often desig-
nated as proinflammatory cytokines, were significantly
reduced by emu oil application in mice treated similarly
to the above (Yoganathan et al., 2003). In rats with
adjuvant-induced polyarthritis, significant reductions in
paw swelling (up to 84%) and arthritis score (up to
70%) were found after exposure to emu oil (Snowden
and Whitehouse, 1997). However, considerable varia-
bility in effectiveness of some commercial oil samples
has been reported (Whitehouse et al., 1998).
5.2 Meat
Literature on emu meat has been compared to ostrich
and rhea meat by Sales and Horban
˜czuk (1998b) and
Sales (2002). In Australia abattoirs specific for the
slaughtering of emus were designed at the beginning
of the 1990’s (Tuckwell, 1993), and trade names have
been assigned to emu muscles (Australian Quarantine
and Inspection Services, 1993). The pelvic limb
musculature of the emu has been described in detail,
and compared to older literature, by Patak (1988) and
Patak and Baldwin (1998). Four bellies, and not the
usual three, in the Muscularis gastrocnemius (the most
powerful muscle in the shank) distinguish emus from
other avian species. Furthermore, contribution of the
pelvic limb muscles of emus to total body weight is
similar to that of the flight muscles of flying birds
(Patak and Baldwin, 1998). The relatively wide distri-
bution and occurrence (28%) of slow-tonic glycolytic
fibres in the M. pectoralis pars thoracica of the emu
(Rosser and George, 1984) could represent the ances-
toral avian M. pectoralis, neoteny, or be an effect of
flightlessness (Rosser and George, 1985).
Carcass characteristics of emus are presented in
Table 8. Internal (abdominal) and external (breast and
back) fat were removed together with the skin, and not
included in carcass weight. Different definitions of
carcass weight complicate comparisons between
species. The distribution of meat production among
the different muscles of the pelvic limb is indicated in
Table 9.
10 James Sales
Table 8 Mean body weight, carcass weight and weight of by-
products of emus (Sales et al., 1999)
Component kg
Body weight 41.00
Hot carcass weight 20.29
Cold carcass weight 19.62
Total meat 14.05
Total fat 11.47
Total bone 4.27
Neck 1.30
Feathers 0.69
Blood 1.41
Wings 0.11
Feet 1.38
Tail 0.29
Head 0.30
Heart 0.34
Lungs 0.25
Trachea 0.24
Empty gizzard 0.51
Proventriculus 0.10
Liver 0.41
Viscera 1.08
Table 9 Mean weight of the different muscles (untrimmed) from
the emu carcass (body weight of 41 kg) from both sides (Sales
et al., 1999)
Muscle Weight (kg)
M. obturatorius medialis 0.29
M. iliotibialis lateralis 1.74
M. femorotibialis medius 0.82
M. flexor cruris lateralis 0.64
M. iliotibialis cranialis 1.02
M iliofibularis 1.22
M. gastocnemius pars interna 1.30
M. gastocnemius pars externa 0.91
M. fibularis longus 0.98
M femorotibialis externa et interna 0.61
M. iliofemoralis 0.33
M. ambiens 0.13
Similar to ostrich (Sales and Mellett, 1996) and rhea
meat (Sales et al., 1998), relatively high final pH values
(46.0) that cause a dark colour, high water-holding
capacity and limited shelf-life in meat and is normally
associated with pre-slaughtered stress, have been
reported for emus that were slaughtered immediately
upon arrival at the abattoir. However, a resting period
of two weeks near the abattoir resulted in ‘normal’ final
pH values of around 5.6 (Berge et al., 1997). Although
different among muscles, pH decline rates in emu
muscles were such that toughening due to cold short-
ening or the effects of pale soft exudative conditions
were eliminated (Trout et al., 2000).
Moisture (75.0 – 75.9%), protein (20.5 – 21.1%) and
lipid (0.9 – 1.2%) contents did not differ among five
different emu muscles. By contrast, pigment (22.0 –
29.0 Fe mgg
1
), total (0.40 – 0.75%) and heat-stable
(0.32 – 0.62%) collagen content showed wide variations
among muscles. With an increase in animal age from 6
to 20 months, collagen content stayed constant, but
collagen heat solubility decreased from 21 to 15%
(Berge et al., 1997).
The creatine level in fresh ground emu meat (695 mg
100 g
1
) is lower than that in beef (786 mg 100 g
1
).
However, after thermal processing higher levels were
detected in emu jerky (1,553 mg 100 g
1
) than in beef
jerky (1,518 mg 100 g
1
). This demonstrates the poten-
tial of a processed emu meat snack to be considered as
a functional food for athletes looking for performance
enhancement, and who are interested in consuming
greater qualities of creatine from a natural food
source (Pegg et al., 2006). Cholesterol content reported
for raw emu meat varies from 32.2 (Beckerbauer et al.,
2001) to 98.0 mg 100 g
1
(Daniel et al., 2000) and
differences are probably related to techniques to quan-
tify cholesterol among laboratories.
A higher polyunsaturated to saturated ratio of 0.9
than presented in Table 7 has been reported for emu
meat by Mann et al. (1995). The fatty acid profile of
the M. iliofibularis was not influenced by either gender
or source of dietary fat (soybean oil high in unsaturated
fat or beef tallow high in saturated fat) fed for 9 weeks
during the finisher phase (Beckerbauer et al., 2001).
The mineral composition of emu meat is presented in
Table 10. No barium, beryllium, cadmium, lead,
molybdenum, nickel, silver, titanium, vanadium or
zirconium could be detected. The influence of muscle
and cooking on the chemical composition of emu meat
is illustrated in Table 11. Cooking of meat increases the
concentration of most nutrients because of moisture
loss during heating.
Compared to beef, emu meat was rated via sensory
evaluation as either more tender, juicier and more
flavourful (Adams et al., 1997), or to be similar in
overall flavour, juiciness and palatability (Offerman
and Sim, 1996). Broiling to 60
C resulted in more
tender and juicier meat than 66 or 75
C. Tenderness,
juiciness, meat-flavour intensity and objective evalua-
tion of tenderness (Warner – Bratzler shear values)
differed among different emu muscles, with muscles
from the thigh more tender than those from the drum.
However, no differences were found between meat
originating from non-breeding versus breeder birds
(Fitzgerald et al., 1999). Sensory evaluation (Berge
et al., 1997) rated emu muscles from most to least
tender (grilled to endpoint temperature of 60
C) as
follows: M. iliofibularis,M. iliotibialis cranialis,
M. flexor cruris lateralis,M. gastrocnemius lateralis,
M. iliotibialis lateralis,M. femorotibialis medius,
M. gastrocnemius medialis,M. fibularis longus.
Tenderness increased in the order of decreasing total
collagen or insoluble collagen contents, indicating that
the content and heat stability of the intramuscular
connective tissue are the major factors of toughness
in emu meat when cooked to 60
C. Emus fed beef
tallow as source of dietary fat during the finishing
phase produced more tender and juicy meat cuts with
less connective tissue than did similar cuts from emus
fed soybean oil (Beckerbauer et al., 2001). Although
variable among muscles, fresh emu meat has a low
colour stability. This, together with intramuscular
lipids that oxidise very rapidly, complicate assurance
of consumer acceptability after a period of more than
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 11
Table 10 Mineral composition of emu meat (Pegg et al., 2006)
Mineral mgg
1
meat
Aluminum 0.7
Boron 0.5
Calcium 50
Chromium 0.17
Cobalt 0.10
Copper 2.3
Iodine 50.3
Iron 50
Magnesium 250
Manganese 0.30
Phosphorus 2,300
Potassium 3,100
Selenium 1.1
Sodium 470
Strontium 0.06
Zinc 36
3 days of retail display in contact with air (Berge
et al., 1997).
Flavour and aftertaste of patties made from lean
beef were rated as more acceptable by consumers
than those made from ground emu meat, probably
related to the higher fat content in beef that resulted
in more flavour and tenderness. Unfamiliarity with
emu meat could also have contributed to these
results. Fat might also be involved in a higher
cooking loss in beef patties than patties made from
emu meat (Miller and Holben, 1999). According to
physio-chemical (pH, extract release volume, thiobar-
bituric acid values) and sensory (colour, flavour,
juiciness, tenderness, overall acceptability) evalua-
tion, patties and sausages made from emu meat are
acceptable for up to 42 days of refrigerated (4
C)
and 90 days of frozen (18
C) storage. Frying
resulted in more organoleptical acceptability of the
latter products than moist cooking (Prabhakara Reddy
et al., 2004). Jerky made from emu meat was rated
as tougher than that made from beef or turkey by
both subjective consumer and objective evaluation,
but also rated the chewiest and most palatable (Carr
et al., 1997). Restructuring emu steaks with combi-
nations of different binders (fibrinogenythrombin,
alginycalcium lactate, phosphateysalt) resulted in
higher pH values and cooked yields, but lower
binding strength, compared to restructured beef
steaks (Shao et al., 1999).
5.3 Skins
Emu skin thickness, measured from the skin surface to
the deep border of the lamina elastica, ranged from 1.7
to 4.2 mm. The epidermis contains a stratum corneum
and cellular epidermis, whereas the dermis of the skin
of adult emus is divided into the stratum superficiale,
stratum compactum,stratum laxum and lamina elas-
tica.Thestratum laxum consists predominantly of
adipose tissue. The cellular epidermis (16.8 versus
10.6 mm) and stratum compactum (492.0 versus
419.2 mm) were found to be thicker in male than
female emus. However, collagen density within the
superficial dense connective tissue layers of the dermis
was highest in females (Weir and Lunam, 2004). In
contrast to the ostrich that has a main area of raised
quill follicles, the entire skin surface of the emu is
covered with follicles (Macnamara et al., 2003).
Image analysis seems to be a promising technique to
visually characterise chromium tanned emu skin and
evaluate abrasion resistance. Colourfastness to dry-
cleaning indicates that emu skin minimally stains
cotton, nylon and wool while changing colour itself.
However, colourfastness due to laundering causes the
skin to shrink and results in staining acetate, cotton,
nylon, polyester and wool. The belly region has less
bending rigidity, and thus better drape and higher
strength, than the back region (Von Hoven et al.,
1999). Emu skin has a similar tensile extensibility to
12 James Sales
Table 11 Influence of muscle and cooking on chemical composition of emu meat (Daniel et al., 2000)
Nutrient M. gastrocnemius pars interna M. iliotibialis lateralis
Raw Cooked
a
Raw Cooked
a
Moisture (g 100 g
1
) 74.7 64.3 73.5 62.0
Protein (g 100 g
1
) 22.3 32.4 23.4 33.7
Fat (g 100 g
1
) 1.8 20.1 2.0 2.7
Ash (g 100 g
1
) 1.2 1.3 1.2 1.4
Calories (Kcal 100 g
1
) 111.1 148.2 116.9 158.8
Cholesterol (mg 100 g
1
) 98.0 130.6
Minerals (mg 100 g
1
)
Potassium 315 312 320 325
Sodium 94.0 117.5 89.3 110.0
Calcium 5.19 5.74 5.41 7.11
Iron 5.46 7.27 5.41 6.89
Zinc 3.65 5.09 3.18 4.32
Vitamins
Vitamin B
12
(mg 100 g
1
) 2.26 24.00 2.24 2.20
Vitamin A (IU 100 g
1
) 16.9 9.7 14.8 10.6
Thiamin (mg 100 g
1
) 0.41 0.41 0.41 0.42
a
Grilled, endpoint temperature of 63C.
ostrich skin, and a rigidity value comparable to pig skin
(Von Hoven, 2002).
On some Australian farms emus are declawed on the
day of hatching by removing the distal phalangeal joint
with a beak-trimming machine, whereas the toe pad
under the claw is retained. This is done to prevent
injuries to handlers and reduce damage to skins during
aggressive behaviours (Frapple et al., 1997; Lunam and
Glatz, 2000). Behavioural evidence has been presented
that declawing does not compromise the locomotor
ability of emus, and has the benefit of improving the
social structure in groups by reducing stereotype
behaviour and aggression (Glatz, 2001).
6. DISEASES
Reference serum biochemical values for adult emus are
presented in Table 12. According to Okotie-Both et al.
(1992) there were no linear relationships between age
(1 to 48 months) of emus and analyte values, nor any
influence of gender. However, values for emus differ
substantially from ostriches. Red blood cells of the emu
contain no 2,3-diphosphoglycerate at any stage of
development (Bartlet, 1982).
A progressive neurodegenerative disorder, causing
ataxia, tremor, circling, lethargy, and inappetence in
the first months of life, and death by 6 months of age,
has been identified in emus (Bermudez et al., 1995;
Kim et al., 1996). Although lysosomal pathology
suggested a gangliosidosis disorder (Bermudez et al.,
1997) with partial-galactosidase deficiency (Freischu¨tz
et al., 1997; d’Azzo et al., 1995), more recent studies
(Giger et al., 1997) demonstrated severe hepatichepar-
ansulfate accumulation and deficient activity of lyso-
somal-N-acetylglucosaminidase. An autosomal
recessive mode of inheritance was demonstrated in
that both parents of affected birds had intermediate
levels of lysosomal-N-acetylglucosaminidase. The
liver of infected birds had elevated levels of enzymes
involved in glycosaminoglycan metabolism, whereas
other lysosomal enzymes were within the normal
range. These findings indicated that affected emus
had an avian lysosomal disease homologous to the
human disorder Sanfilippo syndrome type B (Giger
et al., 1997).
Emus are susceptible to intranasal inoculation with
the highly pathogenic H5N1 avian influenza virus that
emerged in Hong Kong in 1997 (Leigh Perkins and
Swayne, 2002). Avian influenza virus subtypes H5N2,
H7N1 (Panigraphy et al., 1995), H3N2, H5N9, H7N3
(Panigraphy and Senne, 1998), and H10N7 (Woolcock
et al., 2000), all nonpathogenic for chickens, were
isolated from emus in the USA. Furthermore, the low
pathogenic H9N2 avian influenza virus was found in
sick emus in China (Kang et al., 2006). The presence of
avian influenza virus and antibodies in emus suggest
susceptibility to this virus that causes syndromes
ranging from subclinical infection to an acute,
systemic, and fatal disease (Panigraphy et al., 1995).
A case of necrohemorrhagic enteritis and secondary
Escherichia coli septicemia was associated with a
combination of adenovirus and rotavirus infection in
a 2 week old emu chick (Hines et al., 1995). Avian
tuberculosis, caused by Mycobacterium avium (Rao
and Chowdary, 1980; Shane et al., 1993; Pocknell
et al., 1996), and malaria due to a Plasmodium
species (Fox et al., 1996), had occurred in captive
emus. Campylobacter species have been identified in
caecal samples from emus, showing the potential of
emus as pools of these food borne pathogens that could
be transmitted to humans (Oyarzabal et al., 1995). A
Campylobacter-like organism, known as Lawsonia
intracellularis, has been associated with rectal prolapse
and proliferative enteroproctitis (Lemarchand et al.,
1997). Based on etiology (Cryptosporidia spp.), epide-
miology, and histopathology the latter condition is
different from the phallic prolapse and cloacitis
described in South African ostriches (Pernith et al.,
1994).
Verminous encephalitis, caused by the nematode
Baylisascaris (Kazacos et al., 1982), resulting in
ataxia followed by bilateral leg paralysis, was first
identified in emus in 1978 (Winterfield and Thacker,
1978). A later outbreak of this disease was attributed
to the neurotrophic nematode Chandlerella quiscali
(Law et al., 1993). Infections with Eastern equine
The emu (Dromaius novaehollandiae): a review of its biology and commercial products 13
Table 12 Range of biochemical reference values in the blood of
adult emus (Fudge, 1995)
Parameter Values
Protein (g 1 g
1
) 0.34 – 0.44
Glucose (mg l
1
) 11.4– 20.3
Cholesterol (mg l
1
) 4.2 – 16.6
Uric acid (mg l
1
) 0.07 – 0.87
Creatinine (mg l
1
) 0.01– 0.04
Creatinine phosphokinase (IU l
1
) 70 – 818
Lactate dehydrogenase (IU l
1
) 318– 1,243
Aspartate aminotransferase (IU l
1
) 80 – 380
Phosphorus (mg l
1
) 0.38 – 0.72
Calcium (mg l
1
) 0.88 – 1.25
encephalitis (Tully et al., 1992; Brown et al., 1993;
Veasey et al., 1994; Day and Stark, 1996), Western
equine encephalitis (Ayers et al., 1994), and St. Louis
encephalitis (Day and Stark, 1996; 1998) have all been
reported in emu flocks in the USA. Emus can
apparently tolerate a small number of the lungworm
Cyathostoma variegatum without obvious adverse
effects. However, at high loads or in combination
with other stressors this nematode causes morbidity
and mortality (Rickard et al., 1997).
7. CONCLUSIONS
The benefit of the emu as a production animal is the
large variety of products than can be obtained from it.
Furthermore, the emu is adaptable to a wide range of
environmental conditions. Compared to the ostrich and
rhea, emus are more docile, and easier to handle.
However, development of the emu industry is
hampered by a lack of knowledge about emu products
by the general public, created through insufficient
marketing and promotion. The emu industry is centered
on the value of the oil rendered from fat, especially
seen from the several patents that are disclosed on it.
However, very few of the anecdotal claims regarding
the value of the oil, from treating of arthritis to
preventing heat, friction and wear between metal
surfaces, are supported by scientific clinical trials. No
‘active’ components responsible for the therapeutic
claims of emu oil could yet be identified. The question
arises if the fat from the emu was used many years ago
by the Aboriginals of Australia because it was easy to
obtain? Furthermore, if there are ‘active components’
in emu fat, how will it be influenced by husbandry
practices, and then especially feeding of artificial diets,
under captive conditions? Are the ‘active components’,
if any, originating from or stimulated by the natural
diet?
Regarding emu meat, a much higher volume of a
similar product could be obtained from ostriches. The
emu is a seasonal breeder. With limited production of
emu meat from countries in the northern hemisphere
currently, regular restrictions on the transfer of ratite
meat among countries, and the limited shelf-life of emu
meat, fresh emu meat will only be available for around
six months of the year. This complicates agreements
with meat outlets that demand a constant supply
throughout the year. Processed emu meat products
with a long shelf-life should receive more attention.
Emu leather is not characterised by the huge quill
marks of ostrich leather that are preferred by the
already established ostrich leather market. A potential
market has to be exploited specifically for emu leather,
detached from ostrich leather.
The emu industry has been characterised in all
countries where it is practiced by a ‘breeder’ phase,
when demand exceeded supply. This resulted in extre-
mely high priced ‘breeder’ birds, and lots of invest-
ment. However, within a few years ‘slaughter’ birds
were available, with no market outlets. Prices dropped
to almost nothing, as there was no return for production
costs, and most investors lost interest.
Seeing the high production costs, it is doubtful that
the emu industry would ever get to the extent of, for
example, the poultry or beef industries. The aim should
be to concentrate on the diversity of products, especially
products with high price in exclusive markets.
Consumer education, product development and stan-
dardisation of products should be the key factors in
creation of the emu industry. However, to develop and
promote a product, the raw material has to be available.
Thus, establishment of bird numbers should not be
forgotten, and the latter will not be possible without
sound scientific research on production parameters.
Parameters on incubation and growth of emus under
captive conditions are limited, and warrant investiga-
tion. Digestibility values of feed ingredients are absent,
and the use of fibre in the emu diet is controversial. Too
much is relied on diets formulated for ostriches, a
species with a total different digestive system than the
emu. The finding that feed availability has an influence
on behaviour of emus need further research for possible
incorporation into feed management strategies.
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20 James Sales
... Она является эндемическим для Австралии видом, относящимся к семейству Casuariidae. В настоящий момент в Австралии, США, Канаде, в ряде европейских, азиатских и африканских стран эму содержат и как хозяйственную птицу, получая мясо, жир и шкуры (Pegg et al., 2006;Sales, 2007;Farrell, 2021). В диком состоянии половая зрелость у эму наступает в 2-3-летнем возрасте, а в условиях интенсивного содержания -около 20-месячного возраста (Patodkar et al., 2009). ...
... В диком состоянии половая зрелость у эму наступает в 2-3-летнем возрасте, а в условиях интенсивного содержания -около 20-месячного возраста (Patodkar et al., 2009). Средняя яйценоскость за один цикл 25 яиц (Malecki and Martin, 2002), а продолжительность инкубационного периода около 56 дней (Sales, 2007). Скорлупа яиц имеет насыщено темно зеленый цвет, что связано с отслаиванием большого количества пигмента биливердин. ...
... Given data availability, we settled on a total of 21 species (13 extinct; 8 extant) from five different functional/taxonomic groups: (i) 5 vombatiform herbivores: Diprotodon optatum (2786 kg; extinct) (Wroe et al., 2004), Palorchestes azael (1000 kg; extinct) (Richards et al., 2019), Zygomaturus trilobus (500 kg; extinct) (Johnson, 2006), Phascolonus gigas (200 kg; extinct) (Johnson, 2006), and Vombatus ursinus (common wombat; 25 kg; extant) (McIlroy, 1996;Saran et al., 2011); (ii) 7 macropodiform herbivores: Procoptodon goliah (250 kg; extinct) (Johnson and Prideaux, 2004), Sthenurus stirlingi (150 kg; extinct) (Johnson and Prideaux, 2004), Protemnodon anak (130 kg; extinct) (Johnson, 2006), Simosthenurus occidentalis (120 kg; extinct) (Johnson, 2006), Metasthenurus newtonae (55 kg; extinct) (Johnson, 2006), Osphranter rufus (red kangaroo; 25 kg; extant) (McIlroy, 2008), and Notamacropus rufogriseus (red-necked wallaby; 14 kg; extant) (Strahan, 1991); (iii) 3 omnivorous (but primarily plant-eating) large birds: Genyornis newtoni (200 kg; extinct) (Johnson, 2006), Dromaius novaehollandiae (emu; 55 kg; extant) (Sales, 2007), and Alectura lathami (brush turkey; 2.2 kg; extant) (Jones et al., 1995); (iv) 4 carnivores: Thylacoleo carnifex (marsupial 'lion'; 110 kg; extinct) (Johnson, 2006), Thylacinus cynocephalus (marsupial 'tiger'; 20 kg; extinct) (Jones and Stoddart, 1998), Sarcophilus harrisii (devil; 6.1 kg; extinct in mainland Australia, but extant in Tasmania -see below) (Guiler, 1978), and Dasyurus maculatus (spotted-tail quoll; 2.0 kg; extant) (Belcher et al., 2008); and (v) 2 monotreme invertivores: Megalibgwilia ramsayi (11 kg; extinct) (Johnson, 2006), and Tachyglossus aculeatus (short-beaked echidna; 4.0 kg; extant) (Nicol and Andersen, 2007). ...
... (M in g) (Allainé et al., 1987). For Dromaius (Sales, 2007), we used the average of 6.7 eggs clutch À1 and 3.4 clutches year À1 , an assumed sex ratio of 1:1, and nest success (0.406) and hatching probabilities (0.419) for ostriches (Kennou Sebei et al., 2009). For Alectura, we used the annual mean of 16.6 eggs pair À1 for Leipoa ocellata (Bode and Brennan, 2011), a hatching success of 0.866 for Alectura lathami (Jones, 1988), and an assumed 1:1 sex ratio. ...
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The causes of Sahul’s megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as eight extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.
... −1 ) (Abdalla and Maina, 1981). The emu is a large bird that evolved in a continent (Australia) that historically had low level of predation, especially from placental mammals (Sales, 2007). For the nonvolant mammals, the highest mass-specific respiratory surface area of 43 cm 2 g −1 has been reported in lungs of shrews, e.g., Crocidura flavescens and Sorex sp. ...
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Among the air-breathing vertebrates, regarding respiratory efficiency, the avian respiratory system rests at the evolutionary zenith. Structurally, it is separated into a lung that serves as a gas exchanger and air sacs that mechanically ventilate the lung continuously and unidirectionally in a caudocranial direction. Largely avascular, the air sacs are delicate, transparent, compliant and capacious air-filled spaces that are not meaningfully involved in gas exchange. The avian lungs are deeply and firmly attached to the vertebrae and the ribs on the dorsolateral aspects, rendering them practically rigid and inflexible. The attachment of the lung to the body wall allowed extreme subdivision of the exchange tissue into minuscule and stable terminal respiratory units, the air capillaries. The process generated a large respiratory surface area in small lungs with low volume density of gas exchange tissue. For the respiratory structures, invariably, thin blood-gas barrier, large respiratory surface area and large pulmonary capillary blood volume are the foremost adaptive structural features that confer large total pulmonary morphometric diffusing capacities of O2. At parabronchial level, the construction and the arrangement of the airway- and the vascular components of the avian lung determine the delivery, the presentation and the exposure of inspired air to capillary blood across the blood-gas barrier. In the avian lung, crosscurrent-, countercurrent- and multicapillary serial arterialization systems that stem from the organization of the structural parts of the lung promote gas exchange. The exceptional respiratory efficiency of the avian respiratory system stems from synergy of morphological properties and physiological processes, means by which O2 uptake is optimized and high metabolic states and capacities supported. Given that among the extant animal taxa insects, birds and bats (which accomplished volancy chronologically in that order) possess structurally much different respiratory systems, the avian respiratory system was by no means a prerequisite for evolution of powered flight but was but one of the adaptive solutions to realization of an exceptionally efficient mode of locomotion.
... edlist.org), while ostriches, emus and rheas are commercially farmed for the production of meat, eggs, feathers and leather (Carbajo, 2006;Sales, 2007). Many paleognath birds have only slight sexual dimorphism even as adults and their sex cannot be easily identified by external morphology (Schulenberg, ...
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Embryos, juveniles, and even adults of many bird species lack pronounce external sexually dimorphic characteristics. Accurate identification of sex is crucial for research (e.g. developmental, population, and evolutionary studies), management of wildlife species, and captive breeding programs for both conservation and poultry. An accurate molecular sexing method applicable across the entire bird radiation is theoretically possible thanks to the long‐term stability of their ZZ/ZW sex chromosomes, but current methods are not applicable in a wide range of bird lineages. Here, we developed a novel molecular sexing method based on the comparison of gene copy number variation by quantitative real‐time PCR (qPCR) in conserved Z‐specific genes (CHRNA6, DDX4, LPAR1, TMEM161B, VPS13A), i.e. genes linked to Z but absent from W chromosomes. We tested the method across three paleognath and 70 neognath species covering the avian phylogeny. In addition, we designed primers for four Z‐specific genes (DOCK8, FUT10, PIGG and PSD3) for qPCR‐based molecular sexing in three paleognath species. We have demonstrated that the genes DOCK8, FUT10, PIGG and PSD3 can identify sex in paleognath birds and the genes CHRNA6, DDX4, TMEM161B, and VPS13A can reveal sex in neognath birds. The gene LPAR1 can be used to accurately identify sex in both paleognath and neognath species. Along with outlining a novel method of practical importance for molecular sexing in birds, our study also documents in detail the conservation of sex chromosomes across the avian phylogeny.
... Among them, almost all neognath birds are definite contact incubators, having Type 2 misorientation angle distribution in their eggs ( Figure 5-9). Palaeognaths also spend the majority of their time sitting on a nest (Bertram and Burger 1981;Jolly 1989;Colbourne 2002;Sales, 2006Sales, , 2007Brennan 2009;Cooper et al. 2010;Bonato et al. 2015 (Lea and Klandorf 2002), which is a common feature in neognaths. ...
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Eggshells are biominerals that provide reproductive information of vertebrates. In paleontology, fossil eggshells offer a unique chance to investigate the reproductive paleobiology of extinct taxa because diverse information inscribed in fossil eggshells are unavailable from other types of fossils such as fossil bone and trace fossi ls. In addition, geologic information has been added to once-purely-biogenic-biomineral because fossil eggshells have experienced fossilization process . Being a discipline with biogenic calcite, compared to other fields of vertebrate paleontology, fossil eggshell research can share diverse methodologies with other fields of geology and biology, which are based on analytical approaches (e.g. mineralogy) . Hence, it can have broad implications to diverse fields including, but not limited to, paleontology per se, neontology, and sedimentology. In this dissertation, firstly, I focused on the microstructure and crystallography of fossil and modern eggshells using a device called Electron Backscatter Diffraction (EBSD), which has been a powerful tool in materials science and structural geology. The results can be summarized in the four points. First, the crystallographies of gekkotan and archosaur eggshells were completely different from each other, meaning that calcified eggshells of those clades are independent and homoplastic in their origin. Secondly, the presence of the external zone and squamatic zone in maniraptoran eggshells can be identified by comparing the linearity of grain boundaries of the two zones. In addition, the two different misorientation distribution pattern could be found between them. Thirdly, the crystallography of "geckoid‟ eggshells from Upper Cretaceous deposits in Europe confirmed that they are, in fact, maniraptoran dinosaur eggshells. Fourthly, the microstructural and crystallographic evolution of modern paleognath eggshells were investigated, which can be helpful to understand the evolution of eggshells in modern maniraptoran clades. Moreover, the dark color of fossil eggshells from the Korean Peninsula is mainly attributable to the presence of amorphous carbon, which can be detected by Raman spectroscopy. The amorphous carbon signal of Raman spectrum records the maximum paleotemperature that the fossil material experienced. The deconvolution approach of amorphous carbon in Raman spectrum developed by organic geochemist was adopted in this study, which allows estimating the maximum paleotemperature of fossil locality. These studies clearly show that EBSD can provide more objective results on the microstructure and crystallography of diverse amniotic eggshells than conventional techniques do. They are not only useful for correct identification and classification for fossil eggshells but also helpful to read latent paleobiological information. Notably, crystallographic data might be related to the ethological feature of Maniraptora because the strength of eggshells might be related to the microstructure and crystallography of eggshells. Raman spectroscopic results imply that fossil eggshells might be a useful material to infer the maximum paleotemperature of terrestrial basins. It is because the spectroscopic analysis has been usually focused on marine microfossils and kerogen organic materials rather than terrestrial macrofossils. If the same logic works in the biocarbonate of amniotic eggshells, fossil eggshells can be used as invaluable materials to infer the sedimentological and taphonomic setting of the terrestrial fossil-bearing deposits. In short, EBSD and Raman spectroscopy are essential tools to get novel information from eggshells that we had never acquired before. Along with this new technology, future research should be focused on combining statistical and analytical methods to correctly interpret hidden information from fossil and modern eggshells.
... Emus are capable of walking within two days after hatching (Sales, 2007). Yet femora and tibiotarsii of chicks and early juveniles tend to be "underbuilt" relative to adults as indicated by positive allometry in polar moment of area (Main & Biewener, 2007). ...
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Background Birds show adaptations in limb bone shape that are associated with resisting locomotor loads. Whether comparable adaptations occur in the microstructure of avian cortical bone is less clear. One proposed microstructural adaptation is laminar bone in which the proportion of circumferentially-oriented vascular canals (i.e., laminarity) is large. Previous work on adult birds shows elevated laminarity in specific limb elements of some taxa, presumably to resist torsion-induced shear strain during locomotion. However, more recent analyses using improved measurements in adult birds and bats reveal lower laminarity than expected in bones associated with torsional loading. Even so, there may still be support for the resistance hypothesis if laminarity increases with growth and locomotor maturation. Methods Here, we tested that hypothesis using a growth series of 17 homing pigeons (15–563 g). Torsional rigidity and laminarity of limb bones were measured from histological sections sampled from midshaft. Ontogenetic trends in laminarity were assessed using principal component analysis to reduce dimensionality followed by beta regression with a logit link function. Results We found that torsional rigidity of limb bones increases disproportionately with growth, consistent with rapid structural compensation associated with locomotor maturation. However, laminarity decreases with maturity, weakening the hypothesis that high laminarity is a flight adaptation at least in the pigeon. Instead, the histological results suggest that low laminarity, specifically the relative proportion of longitudinal canals aligned with peak principal strains, may better reflect the loading history of a bone.
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The objective of this study was to describe emus’ breeding performance in Brazil at different ages, grouped in couples or colonies. The duration of the breeding season and the production of eggs per female housed were recorded, and the productivity and breeding variables were associated with the variation of the photoperiod. The total production of the flock was 180 eggs, and the breeding season lasted 167 days (April-September), a period with an average of 11 h and 11min of daylight. The breeding season lasted 113, 133 and 82 days, the numbers of eggs produced per female were 7.29, 25.67 and 17.3, and productivity values were 31.6, 38.6, and 45.4% in the groups of birds with ages of two, four and seven years, respectively. The breeding season in 2016 occurred between April and August in Brazil. Older birds tended to start breeding later. The production rate observations indicated that earlier peak production was associated with lower egg production potential. Finally, there was a tendency for better breeding performance of birds housed in couples than in groups with more birds.
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