Aspectos cria e hibridacion de choiques

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Sarasqueta, D. V.- “Aspects of Rearing,
Reproduction and Hybridization of darwin´s rhea or
Choique (Rhea pennata syn. Pterocnemia pennata,
spp pennata”).
Paper 3. Pages 35-44
In: Proceedings of the 3rd. International Ratite
Science Symposium of the World´s Poultry Science
Association (WPSA) & XII World Ostrich
Congress.
Madrid 14-16 de Octubre de 2005.
Editado: Eduardo Carbajo, Madrid, Spain.

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PAPER 3
Aspects of Rearing, Reproduction and Hybridization of Darwin’s Rhea
or Choique (Rhea pennata syn. Pterocnemia pennata, spp pennata).
Daniel Victorino Sarasqueta, Veterinarian.
Instituto Nacional de Tecnología Agropecuaria (INTA). EEA-Bariloche, Argentina.
dsarasqueta@bariloche.inta.gov.ar
Key Words: Rearing, Growout, Reproduction, Hybridization, Autochthonous.
Introduction
The aim of this study was to contribute towards the implementation and development of the
ratite industry in Argentina, based on an autochthonous species from the Patagonian region:
Darwin’s Rhea, also known as Choique or Ñandú de Patagonia. To date, there is no ratite
industry in South America.
The rhea is a flightless bird that originated and evolved in the South American continent, i.e.
present-day rheas and their ancestors (the different biological forms that developed over time,
stemming from a common ancestor and developing into today’s species) have lived in South
America for millions of years. It is believed that the first ancestors of this line already existed in
South America when it split away from the Supercontinent Gondwana during the Late
Cretaceous, approximately 90 million years ago. (Camacho, 1990; Bonorino, 1990; Clarke,
2004; Valverde, 2004).
Today, there are two rhea species:
a) Greater rhea (Rhea americana), also known as Ñandú común or Ñandú moro, which includes
five subspecies (R. a. americana, R. a. intermedia, R. a. nobilis, R. a. araneipes and R. a.
albescens). Its natural distribution area covers the Pampa, Chaco and Mesopotamia regions of
Argentina; Uruguay; northeast, southeast and southwestern Brazil, Paraguay and eastern
Bolivia. (del Hoyo, 1992).
b) Lesser rhea (Rhea pennata syn. Pterocnemia pennata), also known as Ñandú petiso, which
includes three subspecies: Choique or Ñandú de Patagonia (R.. p. pennata) and Ñandú
cordillerano, de la Puna or Suri, which has two subspecies (R.. p. garleppi and R.. p.
tarapacensis) (del Hoyo, 1992). The Choique’s distribution area covers the Patagonian region
of Argentina and Chile –except for Tierra del Fuego – and southern Mendoza Province; and in
Chile it lives in XIº Región (Aysén) and XIIº Región (Magallanes). The distribution of the Suri
is southern Peru, southwest Bolivia, northeast Chile and northwest Argentina; where it lives at
altitudes of 3.800-3.900 m. above sea level (Cajal, 1988).
At the present day the international status of Choique is: 1- Wild population is in Apendix I
(CITES); and 2- Farm population is in Apendix II (CITES).
Like the wild camelids (guanaco and vicuña), it is possible, rheas have been hunted by man ever
since his arrival to South America (12.000 B.C.), as a source of food, utensils and clothing.
“Fat” Choique flesh was one of the main, tastiest foods for the Tehuelche natives who inhabited
the Patagonian region. They ate rhea flesh, fat, bone marrow, blood, gizzard (muscular stomach)
and heart. They used the leg tendons to make straps for their hunting slings (“boleadoras”) and
to sew the guanaco hide they used for building their dwellings (“toldos”), while the hides were

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used for making blankets (Musters, 1979). Over the years, Choiques have been put to use by
means of different techniques and for different purposes, varying from subsistence hunting (for
food) to poaching (for the sale of the products).
I expect the future relationship between man and rhea in this region to involve sustained
production on farms for commercial purposes, with wild populations being preserved and used
as a source of new “genes” in order to maintain the diversity of the flocks raised in captivity.
Commercial production in captivity and the protection of wild populations should work as a
“symbiotic” relationship, providing a source of productive diversification and economic benefit.
Thus, if people perceive this autochthonous species as economically valuable, they should feel
encouraged to ensure its permanent conservation.
The study described in this paper was conducted in two stages. The first stage was carried out at
Estación Experimental de Trelew INTA (Chubut Province), from 1980 to 1984; while the
second stage was carried out from 1991 to date (2005) at Estación Experimental de Bariloche
del INTA (Río Negro Province). The study pioneered a focus on rhea production in Argentina,
with no similar antecedents except for one proposal for the use of the Greater Rhea in Buenos
Aires Province (Daireux, 1944). Other studies on these species have focused mainly on
biological aspects (Brunning D., 1974).
Materials and Methods.
At the time the original stock of birds was set up, there were no rhea farms, so specimens were
taken from the wild, which, in addition, ensured that the genetic material being used was
representative. During the first stage (1980) newly hatched chicks (“charitos”) were captured
and raised artificially. During the second stage (1991) it was decided to collect fertile eggs from
wild nests, in order to avoid introducing into the farm any of the endo- or ectoparasites that
infest wild chicks. Wild nests were located by walking and riding over lands where there were
wild rheas. The eggs that were collected showed signs of embryonic development, so the heat
chain (36 ºC) was preserved during the time it took to transfer them to the incubators, where the
incubation process was completed. The first incubator used had a system of dry bulb and wet
bulb thermometers which prevented relative humidity (RH) from dropping below 57-60 %, and
wild eggs were incubated under these conditions. This method was subsequently replaced by an
electronic system that enabled RH to be set at the desired precision.
After the initial stock had been formed, eggs were incubated either artificially (AI) or naturally
(by the male). The variables used in AI were: temperature = 36.2 - 36.4 ºC, relative humidity =
45% (ranging from 42 to 49 % according to egg size) and automatic turning once per hour. The
hatching trays were placed inside the incubator (at the bottom).
The chicks were raised using a system of brooders fitted with infra-red lamps and a floor or
“bed” of sand, and fed on specific formulated concentrate (starter) for rheas. Connected to each
brooder was an outdoor brooding pen, to provide a space for the chicks to graze, exercise and
receive sunshine. After hatching, the chicks remained in the hatching trays for 8 to 12 hours
until their lungs dried. Then, the umbilicus was disinfected with iodine, body weight recorded
and a numbered plastic tag attached to one leg. Finally, the chicks were transferred to the
brooders installed in the brooding facility, where they remained until they were 3 to 5 months
old. They were fed on formulated concentrate (Starter), administered ad-libitum, with the
following composition: raw protein: 22 %; crude fiber: 9 %; 2.852 Kcal (11.9 MJ) ME; Ca 1.25
%; P: 0.6 %. In addition, they were given green leguminous fodder (Trifolium repens – white
clover) either by direct grazing or supplied chopped from outside the pen.
Twenty adults were used as breeders, and the data presented in this paper are based on these.
They were fed on formulated concentrate (Breeder) with the following composition: Raw
protein: 20 %; Crude fiber: 14 %; 2.408 Kcal (10 MJ); Ca 2.2 %; P: 0.55 %).

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Live weight was measured using electronic scales. Juvenile weight was recorded at hatch and at
the end of the brooding period; adult weight was recorded before and after the breeding season.
Live weight data for growout birds were obtained mainly from the farm “La Granja” in
Neuquén Province, where a similar brooding technique and the same balanced feed were used.
The protein content in the formulated concentrate that was fed to the growout category was 20
%, even though 18 % is suggested for this class (Godoy & Malceñido, 2003). At present, there
is no commercially available formulated concentrate of this type.
Juveniles and adults were identified by a numbered plastic tag, color-coded by sex,
attached to the distal region of the tibiotarsus or middle of the tarsus-metatarsus.
Female production was monitored daily during the egg-laying period and hours, either by direct
observation or through binoculars. The variation of egg shape among females was also useful in
monitoring their production.
The farm facility was divided into the following areas: 1- Brooder facility comprising brooders
and brooding pens; 2- Incubation room and 3 – Breeding pens. Growout pens were not built due
to the limited space available.
The breeding pens had a surface area of about 800 m2 (20 x 40 m ), and included feeders, water
troughs and shelters, all connected by means of an interior passage. The surrounding wire mesh
fencing was 1.80 m high, while interior fencing was 1.60 m high.
Specimens of the two rhea species were raised in separate pens, in order to study the biological
and productive aspects of pure species. Once these data had been collected, hybridization tests
were started.
Results and Discussion.
Incubation- The mean artificial incubation period was 37.5 days (maximum 41 days; minimum
32 days). Early hatching of chicks obeys a natural synchronization effect, which does not affect
chick development. Average egg weight loss during the incubation period was 12.55 % of the
initial weight (maximum 24 %; minimum 7.1 %), considering only chicks that survived for
more than one day. Average chick weight at hatch was 422.17 g. (maximum 530 g.; minimum
310 g.), equivalent to 65.2 % (maximum 74.1 %; minimum 57 %) of initial egg weight.
When incubation was natural, it lasted 40 to 42 days. It was difficult to determine the exact date
on which natural incubation began. Incubating males developed an “incubation patch” –a patch
devoid of feathers located behind the sternum, on the abdomen and inner thighs (temporary
apteria), to improve heat transfer. The feathers that were shed were used for the nest lining.
During the incubation stage, the male usually leaves the nest for short periods during the day
(about 20 to 31 minutes), generally at the hottest time of the day. During incubation, the male
drinks and eats very little, living mainly on the fat reserves accumulated during the season when
feed intake is greater (autumn).
When natural incubation is used as a technique for reproduction management on a farm, one
problem is that embryonic development cannot be monitored. Another risk is that the male
might abandon the nest when certain kinds of disturbance occur. Specific pens need to be
designed and there has to be a high male: female ratio (near or greater than 1:5) among breeders.
Nests are usually made up of 20 to 30 eggs. If there are more, the male is less likely to be able
to provide adequate incubation. When males begin to incubate, the females are moved to other

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pens with other males. When the chicks hatch, it must be decided whether to leave them with
the male for 3 or 5 months, or remove them within the first few days to be raised artificially.
Chick (“charito") raising. Average feed intake during the first 3.3 months (99 days) was 250-
300 g/day/animal.
Tables 1 and 2 show the data for live weight and daily weight gain during the brooding phase,
obtained at INTA-Bariloche and the farm “La Granja”.
For the juvenile categories, at least the following live weights should be recorded: hatch weight,
weight at the end of the brooding stage and weight at the end of the growout stage.
Table 1. Age and live weight of Choique chicks at the end of the brooding stage at different
ages.
EEA-Bariloche (INTA), Río Negro, Argentina.
Age (months) 2.4 (72 days) 3.3 (99 days) 4.2 (126 days) 5.8 (174
days)
Average Live Weight
(L.W.) kg.
8.666 10.656 14.141 18.045
Maximum L.W. kg 10.8 16.6 21.6 22.9
Minimum L.W. kg. 6.8 5.8 8.4 12
Average Weight gain
(WG)
(g/day)
109.1 99.5 110.5 105.5
Maximum WG (g/day) 135 145.1 160 133.7
Minimum WG (g/day) 95.6 51.5 68 77.1
n 9 46 72 33
Table 2. Age and live weight of Choique chicks at the end of the brooding stage for
different years, at “La Granja”, Neuquén, Argentina.
Year 2002-2003 2004-2005
Average age (months) 3.52 (105.6 days) 3.57 (107.1 days)
Average Live Weight (L.W.) (kg) 13.2 10.27
Maximum L.W. kg. 17.5 19.8
Minimum L.W. kg. 7 3.1
Average Weight Gain (WG)
g/day
120.4 93.6
Maximum WG g/day 168.5 133.9
Minimum WG g/day 85 54.8
n 33 44
Health. During the brooding phase (the first 3 to 5 months of age), affections occurred mainly
during the first three or four weeks, except for accidents. The most frequent problems were
impaction, infection of the umbilicus and/or vitelline sac, hypothermia (due to cold nights),
diarrhea – enteritis and leg problems. To a lesser extent, there were incomplete absorption of the
vitelline sac, broken bones and injuries, splay legs, intussusception, ulcer of the cornea,
prolapsed cloaca, twisted neck at hatch. It is worth highlighting that several cases of leg
problems were corrected by administering B-complex vitamins plus a mineral-polivitamin.
As rhea farming develops and the number of birds per unit of surface area increases, deficient
nutritional management, productive pressure and contact with other species are likely to create
conditions favorable to the appearance of new diseases, whether infectious or nutritional.

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During the course of this study, small groups of 20-40 chicks were observed each year. Under
these conditions, survival rates were usually over 80%.
Growout. For this study, the growout phase was considered to be the period of growth between
the age 3 or 5 months and the beginning of an individual’s sexual development, usually
occurring between 20 and 24 months of age. For animals assigned to production of meat, hide,
etc. the growout phase ends at about one year of age.
At this stage, feed intake was de 500-550 g/ day/ bird of formulated concentrate. The food
conversion index during this stage varies from 5: 1 to 10: 1.
When conditions regarding nutrition, health, production control and selection are optimum, it is
feasible to produce animals for slaughter with the following characteristics: 22-24 Kg. live
weight at 8 months, 24-28 Kg. live weight at 10 months, and 28-30 Kg. live weight at 12
months of age (Table 3).
Table 3. Live weight and weight gain for Choiques at different ages.
Age (months) 3.3 (99 days) 5.5 (165 days) 14 (422 days) 27 (820 days)
Average weight Kg 10.2 17.4 28.4 32.3
Maximum weight Kg.
Minimum weight Kg.
16.6
5.6
22.9
12
33
24
37.8
26.3
Average Weight gain *
(WG) (g/day)
97.1 102 65.8 38.9
Maximum WG (g/day) *
Minimum WG (g/day)
145.1
51.5
133.7
77.1
74.8
56.9
45.6
31
Average WG for Period
3.3-5.5 (g/day)
109 (66 days)
5.5-14 (g/day)
42.8 (257 days)
14-27 (g/day)
11.5 (398 days)
Food Conversion Index
Period
2.5-3: 1 4-5: 1 11-12: 1 48-52:1
n 60 29 29 42
* accumulated
According to the data in Table 3, growth rate (g/day) and food conversion index (CI) show that
it is not worth extending the growout to slaughter beyond 14 months of age, because the growth
rate drops substantially and the CI reaches two digits (> 10:1). It may be estimated that weight
gain decreases as from 5.5 months of age by about 7.7 g per month. Thus, by month 12, a bird
would be gaining 60 g/day with a CI of 8.3: 1 and as from month 14, the CI would be 11.7: 1.
According to these data, when the growth rate is lower than 42.8 g/day, it is not worth extending
the growout phase when the priority is meat production, so the optimum age for slaughter is
considered to be 10-12 months. If the value of the hide, fat or larger muscle size (meat cuts)
made it worthwhile, the growout could be extended beyond 14 months.
A good strategy is to attain the highest weight possible by the end of the growout stage, making
the most of the greater daily weight gain during this stage, in order to shorten growout time and
minimize the time during which food conversion is inefficient, and, if possible, ending growout
before winter.

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Reproduction. Both males and females usually attained sexual maturity between 20 and 24
months of age, although some precocious individuals matured between 12 and 14 months of
age.
The breeding season in Northern Patagonia, where this study was conducted, occurred from
April/May to December. The non-breeding season was from January to April. During that time,
both in the wild and on farms where natural incubation was used, the males were dedicated to
raising their chicks. In southern Patagonia, due to the weather, this behavior may occur up to
one month later.
The first breeding-related behavior (song and competition among males) was observed during
autumn (April – May). Sexual behavior such as wing spreading, courting and copulation
occurred in late June and July (winter).
Copulation lasted and average 3 minutes (maximum 18´; minimum 2.3´). The females that
copulated normally during the season, at least once before each oviposition, showed signs of
skinning, bruising, remains of skin, small blood clots and loss of outer feathers on their backs
(“mating patch”)
Nest building starts at the end of autumn (June), almost simultaneously with courting behavior.
The males may dig several holes before building the definitive nest. During the study, the males
built their nests at the same sites as previous years, and only changed sites if they were
disturbed.
The Oviposition season began in mid-winter (August) and ended in early summer (December).
The start of the oviposition season was linked to weather conditions during the previous months,
with harsh winters with heavy frost and heavy snowfall delaying it (September), and warm
winters bringing it forward (July).
Average duration of the breeding seasons during the study was found to be 136.7 days (4.5
months). The shortest season occurred in 1995, and lasted 77 days (2.5 months), while the
longest was in 2000 and lasted 186 days (6.2 months). Winter 1995 was the harshest since the
beginning of the study (1991). Average individual oviposition season (time between first and
last egg laid by an individual female) was 107.6 days (3.5 months).
The male to female ratio used during the study was 1 M : 3 F.
Fourteen-year-old females still form and lay eggs.
Egg features. Eggs are light green and speckled with white spots (calcium phosphates; Cremona
V., 2004) of varying in size and distribution. Eggs are usually oval, with one pointed tip and one
rounded tip, but a few may be long or nearly round. Eggs without a shell are occasionally found.
Average egg weight was 620-650 g (maximum 875 g; minimum 385 g). Some very small eggs
weighing 250-350 grams were found. Length (longitudinal or greater axis) was 12.5 to 14.5 cm,.
and width (transversal or lesser axis), 8.5 to 9.5 cm.
Monitoring of female production. Females were monitored during this study (in Trelew and
Bariloche) with the aim of describing their behavior during oviposition, and it was found that
there is an optimum egg-laying time (the last hours of daylight, between 3:30 p.m. and dusk).
Each female was found to produce an egg type having its own particular features (“shape”),
which lasts throughout her lifetime. The distinctive shape of the eggs laid by each individual
female enabled us to monitor them. This method can be used for breeding groups of not more
than 5 or 6 females.

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The following features were considered to determine egg shape: silhouette (oval, long, tear-
shaped, rounded, etc.); color, type of shell (smooth, porous, etc.); scars or marks; size and
distribution of the white speckles, weight (g); length (cm), width (cm). All these data are
complemented by information regarding the pen of origin, date and time of laying.
Considering the number of eggs laid and their average weight, the production in egg weight
(Kg) produced by each female per season is obtained. Table 4 shows that females H4 and H40
produced 70 to 85 % of their live weight (May/June) in eggs during a season. These females are
considered to have high production. Other females, such as H21, which produced 16.9 % of her
body weight in eggs, are classed as having low production.
A complete “productive profile” is constructed for each female by considering both oviposition
capacity and data regarding the fertility and hatchability of her eggs. Then, by adding
information on the survival, growth rate, conversion index, live weight, slaughter yield, etc. of
her descendants, a complete data base (production control) can be set up and used for making
adequate selection choices.
There should be genetic diversity within the Choique stock in order to avoid inbreeding. Within
this diversity, there will be some birds whose behavior or productive features are inappropriate
for breeding in captivity, and these should be removed from the system. It is more efficient to
keep a high production female than one with low oviposition, since both will have similar food
intake.
The weight of the eggs that each female lays is not constant throughout the season. Egg weight
may vary by over 100 g. Egg shape, however, does not change.
The interval of time between two consecutive eggs laid by one female varies according to the
time of the laying season considered. For example, for female H40 (Table 4), if the entire
season is considered, the interval is 2.8 days, but if maximum egg-laying periods are
considered, it is 1.8 days. This is because there are periods of time (days or weeks) during the
season when no eggs are laid due to the weather conditions or to individual factors.
Table 4 Egg-producing capacity of seven females. EEA-Bariloche (INTA).
Female
Nº 4
Female
Nº 5
Female
Nº 6
Female
Nº 7
Female
Nº 21
Female
Nº 40
Female
Nº 54
Length of oviposition
(days)
145 106 109 104 74 126 86
Number of eggs 43 37 35 30 14 44 25
Interval between eggs
(days)
3.3 2.86 3.1 3.4 5.2 2.8 3.4
Average egg weight
(grams)
623.4 587.4 687.3 628.5 561.3 658.7 653.3
Total grams of eggs
produced
26.809 21.733 24.055 18.856 7.858 28.986 16.333
Live weight females
(May/June)
35.4 36.2 32.6 33.4 46.4 34.4 39.4
Ratio grams produced/
live weight female (%)
75.7 60 73.7 56.4 16.9 84.2 41.4
Table 5 Duration of oviposition, number of eggs, fertility and hatchability for females Nº 4 and
Nº 40 (EEA-Bariloche).
Female Nº 4 Female nº 40
Oviposition duration (days) 156 126
Number of eggs 48 44

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Number of fertile eggs 36 28
Fertility % 75 63.3
Number of hatched eggs 20 19
Hatchability % 55.5 67.8
Body Weight of Breeders. Adult Choique live weight is always recorded one month prior
(May/June) to the beginning of reproductive behavior (copulation, oviposition). Average live
weight for adults was 38.4 Kg. For males, live weight was 41.7 Kg, while for females, average
live weight was 35.2 Kg. Average weight for females was 15.5 % lower than for males. Table 6
compares these data with those obtained at the farm “La Granja”.
During the year there are fluctuations in live weight according to the season and to sexual
activity. During the breeding season, all birds lose weight – males lose weight due to the
expenditure for incubation, fighting, courting, copulating, etc., and females due to oviposition,
copulation and a certain anorexia (Angel, 1996). Weight loss for both sexes is in the range of 15
to 20 % of the live weight recorded at the beginning of the breeding season (May/ June). During
the months following breeding (January – April) the adults regain lost weight, and this is the
time of year when feed intake is greatest. To keep a good record of the annual evolution of live
weight of breeders, they should be weighed before (May/ June) and after (February/ March) the
breeding season.
Table 6. Live weight of adults compared between INTA-Bariloche and the
farm “La Granja”.
INTA-Bariloche La Granja
Average live weight kg
Maximum weight kg
Minimum weight kg
38.4
48.8
26.6
32.1
38
26.3
Average weight Males kg
Maximum weight kg
Minimum weight kg
41.7 (n=6)
48.8
36.5
34.2 (n=22)
38
26.3
Average weight Females kg
Maximum weight kg
Minimum weight kg
35.2 (n=14)
46.6
26.6
30 (n=20)
34
26.5
Difference between M and F 6 (15.5 %) 4.2 (12.1%)
Age years > 2 >2
Time of year May/ June March
n 20 42
Table 6 shows the live weights recorded at INTA-Bariloche and the farm “La Granja”. The
difference in average adult weight is attributed to the fact that weights were recorded at different
times of year. At INTA-Bariloche, weights were recorded during May/June, when the birds’
physical condition was at its best, while at La Granja, weights were recorded in March, when
the birds were recovering their breeding expenditure and needed to accumulate reserves.
Food intake. For adults (breeders) annual intake of formulated concentrate was 669 g/day /bird,
or sometimes less if complemented with grazing. Feed intake is not constant throughout the
year, but varies according to reproductive behavior. During the breeding season, both males and
females eat less and increase their energy expenditure; e.g. during natural incubation, males
hardly feed, and live on reserves (fat) accumulated during the non-breeding season (autumn),
while females spend energy on egg production. Thus, during the breeding season, their feed
intake drops by up to 40-50%. This pattern is similar for emus (Angel, 1996). Annual feed

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intake follows a curve which is equivalent to the curve for the evolution of live weight, but
precedes it (the birds feed first, then weight gain). The greatest intake can therefore be seen to
occur in late summer – autumn (900-1000 g/ day/ bird) and lowest intake (350-450 g/ day/
animal) during the breeding season (July – December).
Graph 1. Graph showing annual intake of formulated concentrate by adult
Choique, INTA- Bariloche.
Hybridization. Beginning in 1997, a series of experiments was conducted with the aim of
finding out if it is feasible to produce hybrid birds by crossing different rhea species (Rhea
americana and Rhea pennata).
From a biological standpoint, the purpose of producing hybrids is to gain further knowledge,
while from a production standpoint, it is to seek a possible method for increasing individual
rhea productivity, i.e. to maximize the reproductive and/or productive efficiency of individual
birds and hence, of the system.
This line of work aimed to ascertain whether, in addition to the biological feasibility of
producing hybrids, there was Hybrid Vigor or Heterosis (“the superiority of crosses (F1) as
compared to the progenitor lines (F)”), regarding some trait which would be useful to
production (growth rate, body weight, feed intake and conversion; number of eggs, fertility,
survival, etc.). The “industrial cross breeding” technique is widely used, both in modern poultry
production and traditional livestock farming (cattle, sheep, swine, etc.).
In order to try to prevent behavior barriers from appearing during the breeding season, chicks of
both species were raised together from the time they hatched.
First of all, attempts were made to cross the species, for which two breeding groups were set up,
with Ñandú común and Choique males as fathers.
It was possible to produce hybrid ÑC (Male) x CH (Female); but so far it has not been possible
to get CH (Male) x ÑC (Female) to mate naturally. In this case, females (ÑC) showed
willingness to mate, but males (CH) were reluctant to do so, although they did mate with
females of their own species. Attempts to achieve this cross will continue to be made.
At present, the Hybrid lot is made up of 22 birds.
Results of the crosses attempted so far are:

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Ñandú común (Male) x Choique (Female): eggs and fertile descendants (F1: ÑC x CH).
Hybrid (F1) x Hybrid (F1): eggs and fertile descendants (F2).
Hybrid F1 (Male) x Choique (Female): fertile eggs and descendants.
Choique (Male) x Ñandú común (Female): no mating occurred.
Ñandú común (Male) x Hybrid F1 (Female): no mating or egg laying occurred.
Characteristics of Hybrid F1 (ÑC x CH). The descendants of the cross between pure rhea
species are morphologically similar to the Ñandú común. They have slightly “brownish” gray
feathers, which are uniform over the entire surface. Black patches on the head, neck and breast
are absent or very pale. The white patches which are typical of the Choique can only be seen on
adult hybrids as small white bands on the breast area (pectum); which become noticeable after
sexual maturity is attained, though to a lesser degree than in the Choique. The iris is a light
grayish-green color. The scales or keratinized epidermal rings covering the tarsus-metatarsus
(podotheca) are similar to those on the Ñandú común, but cover only the lower two thirds;
above which there are polygonal scales, as in Choique. Body height (digits-crown) is equivalent
to the Ñandú común. Body mass, especially in females, is greater than in ÑC progenitors. This
outward appearance of birds of this class is uniform.
Average F1 chick weight at hatch is 431.3 grams (maximum 530 g; minimum 380 g) equivalent
to 65.3 % of initial egg weight. Incubation period was 37.25 days (maximum 40 days; minimum
35 days).
Growth and body weight of F1 hybrids was estimated during an indoor trial (without access to
brooding pens) together with Choique chicks. Brooding conditions were the same for both, and
the trial lasted from hatching to 6.4 months of age. The growth rate for F1 chicks was 18 %
higher than for Choiques, with F1 chicks reaching the same live weight as Choiques 36 days
earlier.
Table 2. Average weight of Choique chicks compared to Hybrid chicks.
Average age
Months days
Live weight
average kg
Average gain
g/ day
Live weight kg
Maximum Minimum
Choiques 6.4 (192) 21.08 111.36 22.9 18.8
F1 Hybrids 5.2 (156) 21.795 136.25 23 21
F2 Hybrids 5.5 (166) 8 45.4
Once F1 chicks reached sexual maturity, at two years of age (some specimens attained sexual
development at one year of age), they mated naturally, producing fertile eggs.
F1 eggs were similar to ÑC eggs: yellow-colored with a subtle greenish tint, without white
speckles. Laying hours were similar to those of Choique females (from mid-afternoon to dusk).
These eggs were larger than those laid by pure species, weighing an average 725 grams
(whereas average Choique egg weight was 620-650 g).
The oviposition season began in September and ended, as for Choiques, in late December / early
January.
The pattern of annual feed intake for F1 hybrids was similar to Choiques; with a minimum
during the breeding season (September) and a maximum during the non-breeding season
(February-March).

12
Based on personal observation during the daily handling of different species, it was noticed that
the F1 hybrids had the most docile behavior, while the Ñandú común had the most nervous or
excitable temperament, and the Choique was somewhere in between. The docile character of the
hybrids was apparent either during handling maneuvers or due to the fact that they were not
aggressive towards humans during the breeding season.
Characteristics of F2 Hybrids (Hybrid F1 x Hybrid F1). The descendants obtained from crossing
F1 hybrids is called F2. Average hatch weight for F2 Chicks was 446.5 grams (maximum 539
g.; minimum 400 g) equivalent to 61.5 % of initial egg weight.
The viability of F2 chicks was not good during the first seasons, but improved during the last
season when Relative Humidity during incubation was reduced to 42%.
Backcrossing of Hybrid F1 (Macho) x Choique (Female). This cross was done for the first time
during the 2004 season. A trio made up of one (1) male and two (2) females was set up.
Average weight of the chicks hatched during the hatching season was 393.8 grams, equivalent
to 64.2 % of initial egg weight.
Up to their present age of 4.5 months, their growth and development has produced a variety in
size and morphology. Some have grown well, while others show little growth for their age.
Average live weight at this age is 12.4 kg. (maximum 18.5 kg.; minimum 4.2 kg.; n= 7);
average weight gain up to 4.5 months of age has been 87.2 g/ day (maximum 128.2 g; minimum
26.9 g/day).
Their appearance and plumage (ptilosis) are similar to the Ñandú común; the iris is light
greenish to light brown; they have keratinized epidermal rings similar to those of the Ñandú
común only on the lower third (distal epiphysis) of the tarsus-metatarsus (“leg”), while the rest
of the bone is covered by skin with rounded, keratinized epidermal “scales” similar to those of
the Choique. Like Choiques, they have feathers on the upper third of the “leg” (proximal
epiphysis). This appearance may undergo changes as the birds grow into adults, particularly
after sexual maturity is attained.
Backcross Ñandú común (Male) x Hybrid F1 (Female). In another pen, a pair of adults was set
up (1 Male and 1 Female), aged 12 and 5 years respectively. This pair was not observed to mate
or lay eggs, possibly due to the female’s lack of reproductive behavior, although the male did
show reproductive behavior and even built a nest. It is assumed that female’s behavior was due
to the fact that she was moved to a different pen after the start of the season (stress).
Conclusions.
Sustained rhea production, whatever the species or farming system implemented (extensive,
intensive, etc.) could be a farming option which would complement and diversify traditional
livestock farming in marginal areas such as Patagonia. Rhea farming, based on the use of an
autochthonous wild species, should produce sustained economic benefit and guarantee the
conservation of wild rheas. All farmers, businessmen, professionals, etc. involved in the value
chain should be aware of and take part in the protection of wild Choique populations, to ensure
their survival and well-being (Wildlife Welfare). These wild populations should be used only as
a source of new “genes” to add to captive stock.
Rhea farming in Argentina today is somewhere in between the “breeder selling” stage and the
“product selling” stage. To enter the “product selling” stage competently on national and
international markets, we need to overcome the limitation posed by the lack of slaughterhouses
legally authorized by the national authority for Animal Sanitation (SENASA) for the slaughter
of rheas.

13
Although a model for rhea production has been implemented in South America, there is still
room for improvement, because biological and productive knowledge of this species is being
gained together with the design, implementation and ordering of a productive system. Present
knowledge enables sustainable rhea farming, but in order to increase efficiency, further
knowledge is needed in certain fields (behavior, breeding, nutrition, sanitation, economy,
product development, etc.).
We need accurate knowledge of the nutritional requirements, especially vitamins, mineral traces
and essential acids for all categories of birds. Regarding sanitation it is essential to conduct an
in-depth diagnostic survey of the infectious affections (bacteria, virus, etc.) that arise when
rheas are farmed, especially the Chick category.
Finally, substantial investment (government and/or private) in research and industrial
infrastructure is needed in order to develop, expand and perfect the system,. Thus, farmers
would be encouraged to invest in equipment, infrastructure and training in order to improve
their productive parameters. Professionals would to specialize in Nutrition, Reproduction, etc.
and farms would be encouraged to specialize in one stage of the system (e.g. fattening). Birds
for reproduction, and their descendants, should be carefully selected and monitored, in order to
achieve the genetic improvement of the stock reared in captivity, because at present, not all
adults used as breeders are really efficient.
Once present limitations have been overcome, prospects for Choique production look
promising, thanks to the unquestionable quality and usefulness of their products.
The data on body weight presented in this paper were obtained from regularly monitored birds
hatched from wild eggs, and provide new information on Choique growth, development and
productive potential. This weight monitoring technique should be applied at all farms for all
Choique categories. At least the following weights should be recorded at all farms: hatch
weight, weight at the end of the brooding stage , live weight at the end of the growout stage and
live weight of breeders before and after the breeding season.
Another way to increase productive efficiency is by means of inter-species cross breeding
(Hybrids).
In order to work out final considerations on the use of Hybrids in the production system, further
research should be conducted on a greater number of birds, which should be of high genetic
quality. Some positive features observed in hybrids so far are: 1-Fertility between pure species
and their descendants (F1); 2-Favorable growth rate during the first months for F1 (136.25
grams/ day).
In the light of the results obtained from rhea hybridization, it would be timely to conduct a
taxonomical revision of the genera, species and subspecies in the Family Rheidae.
References
Angel, C. R., 1996. Ratite Nutition. Chapter 2. In: Ratite Management, Ed. Tully, T and S. M.
Shane. Krieger P. C., Malabar, Florida.Usa.
Bonorino, G.G., 1990. Una Historia de 500 millones de años. Ciencia Hoy, 2:7, 12-17.
Brunning, D.F., 1974. Social structure and reproductive behavior in the Greater Rhea. In: Living
Bird, Thirteenth Annual, 1974. Cornell Laboratory of Ornithology, 1974.
Cajal, J L.,1988. The Lesser Rhea in Argertine Puna Region: Present Situation. Biological
Conservation 45: 81-91. England.
Camacho, H.H., 1990. La biografía historica y la deriva de los continentes. Ciencia e
Investigación, 44: 81-91.

14
Cannon, H.H.; R. E. Carpenter & R. A. Akerman, 1986. Synchronus Hatchings and oxygen
consumption of Darwin´s Rhea eggs (Pterocnemia pennata). Physiol. Zool., 59:1, 95-108.
Cho, P., P. Bronw & M. Anderson (1984). Comparative gross anatomy of ratites. Zoo Biology,
3: 133-144.
Clarke, J. A; C. P. Tambussi; J. I. Noriega; G. M. Erickson & A. Ketcham, 2004. Definitive
fossil evidence for the extant avian radiaton in the Cretaceous. Nature 3150.
Cremona, V. et al., 2004. Informe de Laboratorio Nº 46-04, Laboratorio de Suelos. EEA-
Bariloche (INTA).
Daireux, G., 1944. La cría del ganado en la estancia moderna (Manual del Estanciero), 5ª
Edición. Buenos Aires, Argentina.
Del Hoyo, J., A., Elliot J. & J. Sargatal, 1992. Handbook of the Birds of the World. Volomen I,
Ostrich to Ducks. ICBP, Link Edit., Barcelona.
Fowler, M.E., 1991. Comparative Clinical Anatomy of Ratites J. Zoo. Wild. Med., 22:204-227.
Godoy,Y.E. & Malceñido W., 2003. Produccion carne de Ñandú (Rhea americana):
Requerimientos proteicos para el crecimiento. Tesis Graduación Ingeniero Agronomo, Facultad
de Agronomía, Universidad de la Republica., Montevideo.Uruguay.
Musters,G., 1979. Vida entre los Patagones. Editorial Solar/Hachette, Buenos Aires.
Sarasqueta, D., 1995. Incubación y cría de Choiques (Pterocnemia pennata).Comunicación
Tecnica Nº 88, Área Recursos Naturales-Fauna, EEA-Bariloche INTA. Bariloche, Argentina
Sarasqueta, D., 1997. Cría de Ñandúes. Capitulo 19. En: Cría de Avestruces, Emues y Ñandúes,
2º Edición. Real Escuela de Avicultura, Barcelona. España.
Sarasqueta, D., 2004. Cría y reproducción de Choiques en cautividad (Rhea pennata syn.
Pterocnemia pennata). Primer Congreso Latinoamericano sobre Conservación y Cría
Comercial de Ñandúes. Trabajo completo disponible en: http: //www.webcongress.net
(22/06/2004).
Valverde, F., 2004. Los Ñandúes son aves, y las aves son Dinosaurios. Primer Congreso
Latinoamericano sobre Conservación y Cría Comercial de Ñandúes. Trabajo completo
disponible en: http: //www.webcongress.net (22/06/2004).
Vince, M.A., 1969. Embrionic communication, repiration and sinchronization of hatching. In:
Bird vocalization. De.R.A. Hinde, 233-260. Cambridge University Press.
Acknowledgements: We would like to thank Julio Cesar and Jorge Rene Laurin of “La Granja”
farm for their cooperation; the company ALIBA S.A. for donating the feed for the study; and
Nestor Maceira for reviewing the manuscript so thoroughly.

15
PAPER 3
Aspects of Rearing, Reproduction and Hybridization of Darwin’s Rhea
or Choique (Rhea pennata syn. Pterocnemia pennata, spp pennata).
Daniel Victorino Sarasqueta, Veterinarian.
Instituto Nacional de Tecnología Agropecuaria (INTA). EEA-Bariloche, Argentina.
dsarasqueta@bariloche.inta.gov.ar
Key Words: Rearing, Growout, Reproduction, Hybridization, Autochthonous.
Introduction
The aim of this study was to contribute towards the implementation and development of the
ratite industry in Argentina, based on an autochthonous species from the Patagonian region:
Darwin’s Rhea, also known as Choique or Ñandú de Patagonia. To date, there is no ratite
industry in South America.
The rhea is a flightless bird that originated and evolved in the South American continent, i.e.
present-day rheas and their ancestors (the different biological forms that developed over time,
stemming from a common ancestor and developing into today’s species) have lived in South
America for millions of years. It is believed that the first ancestors of this line already existed in
South America when it split away from the Supercontinent Gondwana during the Late
Cretaceous, approximately 90 million years ago. (Camacho, 1990; Bonorino, 1990; Clarke,
2004; Valverde, 2004).

16
Today, there are two rhea species:
a) Greater rhea (Rhea americana), also known as Ñandú común or Ñandú moro, which includes
five subspecies (R. a. americana, R. a. intermedia, R. a. nobilis, R. a. araneipes and R. a.
albescens). Its natural distribution area covers the Pampa, Chaco and Mesopotamia regions of
Argentina; Uruguay; northeast, southeast and southwestern Brazil, Paraguay and eastern
Bolivia. (del Hoyo, 1992).
b) Lesser rhea (Rhea pennata syn. Pterocnemia pennata), also known as Ñandú petiso, which
includes three subspecies: Choique or Ñandú de Patagonia (R.. p. pennata) and Ñandú
cordillerano, de la Puna or Suri, which has two subspecies (R.. p. garleppi and R.. p.
tarapacensis) (del Hoyo, 1992). The Choique’s distribution area covers the Patagonian region
of Argentina and Chile –except for Tierra del Fuego – and southern Mendoza Province; and in
Chile it lives in XIº Región (Aysén) and XIIº Región (Magallanes). The distribution of the Suri
is southern Peru, southwest Bolivia, northeast Chile and northwest Argentina; where it lives at
altitudes of 3.800-3.900 m. above sea level (Cajal, 1988).
At the present day the international status of Choique is: 1- Wild population is in Apendix I
(CITES); and 2- Farm population is in Apendix II (CITES).
Like the wild camelids (guanaco and vicuña), it is possible, rheas have been hunted by man ever
since his arrival to South America (12.000 B.C.), as a source of food, utensils and clothing.
“Fat” Choique flesh was one of the main, tastiest foods for the Tehuelche natives who inhabited
the Patagonian region. They ate rhea flesh, fat, bone marrow, blood, gizzard (muscular stomach)
and heart. They used the leg tendons to make straps for their hunting slings (“boleadoras”) and
to sew the guanaco hide they used for building their dwellings (“toldos”), while the hides were
used for making blankets (Musters, 1979). Over the years, Choiques have been put to use by
means of different techniques and for different purposes, varying from subsistence hunting (for
food) to poaching (for the sale of the products).
I expect the future relationship between man and rhea in this region to involve sustained
production on farms for commercial purposes, with wild populations being preserved and used
as a source of new “genes” in order to maintain the diversity of the flocks raised in captivity.
Commercial production in captivity and the protection of wild populations should work as a
“symbiotic” relationship, providing a source of productive diversification and economic benefit.
Thus, if people perceive this autochthonous species as economically valuable, they should feel
encouraged to ensure its permanent conservation.
The study described in this paper was conducted in two stages. The first stage was carried out at
Estación Experimental de Trelew INTA (Chubut Province), from 1980 to 1984; while the
second stage was carried out from 1991 to date (2005) at Estación Experimental de Bariloche
del INTA (Río Negro Province). The study pioneered a focus on rhea production in Argentina,
with no similar antecedents except for one proposal for the use of the Greater Rhea in Buenos
Aires Province (Daireux, 1944). Other studies on these species have focused mainly on
biological aspects (Brunning D., 1974).
Materials and Methods.
At the time the original stock of birds was set up, there were no rhea farms, so specimens were
taken from the wild, which, in addition, ensured that the genetic material being used was
representative. During the first stage (1980) newly hatched chicks (“charitos”) were captured
and raised artificially. During the second stage (1991) it was decided to collect fertile eggs from
wild nests, in order to avoid introducing into the farm any of the endo- or ectoparasites that
infest wild chicks. Wild nests were located by walking and riding over lands where there were
wild rheas. The eggs that were collected showed signs of embryonic development, so the heat
chain (36 ºC) was preserved during the time it took to transfer them to the incubators, where the

17
incubation process was completed. The first incubator used had a system of dry bulb and wet
bulb thermometers which prevented relative humidity (RH) from dropping below 57-60 %, and
wild eggs were incubated under these conditions. This method was subsequently replaced by an
electronic system that enabled RH to be set at the desired precision.
After the initial stock had been formed, eggs were incubated either artificially (AI) or naturally
(by the male). The variables used in AI were: temperature = 36.2 - 36.4 ºC, relative humidity =
45% (ranging from 42 to 49 % according to egg size) and automatic turning once per hour. The
hatching trays were placed inside the incubator (at the bottom).
The chicks were raised using a system of brooders fitted with infra-red lamps and a floor or
“bed” of sand, and fed on specific formulated concentrate (starter) for rheas. Connected to each
brooder was an outdoor brooding pen, to provide a space for the chicks to graze, exercise and
receive sunshine. After hatching, the chicks remained in the hatching trays for 8 to 12 hours
until their lungs dried. Then, the umbilicus was disinfected with iodine, body weight recorded
and a numbered plastic tag attached to one leg. Finally, the chicks were transferred to the
brooders installed in the brooding facility, where they remained until they were 3 to 5 months
old. They were fed on formulated concentrate (Starter), administered ad-libitum, with the
following composition: raw protein: 22 %; crude fiber: 9 %; 2.852 Kcal (11.9 MJ) ME; Ca 1.25
%; P: 0.6 %. In addition, they were given green leguminous fodder (Trifolium repens – white
clover) either by direct grazing or supplied chopped from outside the pen.
Twenty adults were used as breeders, and the data presented in this paper are based on these.
They were fed on formulated concentrate (Breeder) with the following composition: Raw
protein: 20 %; Crude fiber: 14 %; 2.408 Kcal (10 MJ); Ca 2.2 %; P: 0.55 %).
Live weight was measured using electronic scales. Juvenile weight was recorded at hatch and at
the end of the brooding period; adult weight was recorded before and after the breeding season.
Live weight data for growout birds were obtained mainly from the farm “La Granja” in
Neuquén Province, where a similar brooding technique and the same balanced feed were used.
The protein content in the formulated concentrate that was fed to the growout category was 20
%, even though 18 % is suggested for this class (Godoy & Malceñido, 2003). At present, there
is no commercially available formulated concentrate of this type.
Juveniles and adults were identified by a numbered plastic tag, color-coded by sex,
attached to the distal region of the tibiotarsus or middle of the tarsus-metatarsus.
Female production was monitored daily during the egg-laying period and hours, either by direct
observation or through binoculars. The variation of egg shape among females was also useful in
monitoring their production.
The farm facility was divided into the following areas: 1- Brooder facility comprising brooders
and brooding pens; 2- Incubation room and 3 – Breeding pens. Growout pens were not built due
to the limited space available.
The breeding pens had a surface area of about 800 m2 (20 x 40 m ), and included feeders, water
troughs and shelters, all connected by means of an interior passage. The surrounding wire mesh
fencing was 1.80 m high, while interior fencing was 1.60 m high.
Specimens of the two rhea species were raised in separate pens, in order to study the biological
and productive aspects of pure species. Once these data had been collected, hybridization tests
were started.

18
Results and Discussion.
Incubation- The mean artificial incubation period was 37.5 days (maximum 41 days; minimum
32 days). Early hatching of chicks obeys a natural synchronization effect, which does not affect
chick development. Average egg weight loss during the incubation period was 12.55 % of the
initial weight (maximum 24 %; minimum 7.1 %), considering only chicks that survived for
more than one day. Average chick weight at hatch was 422.17 g. (maximum 530 g.; minimum
310 g.), equivalent to 65.2 % (maximum 74.1 %; minimum 57 %) of initial egg weight.
When incubation was natural, it lasted 40 to 42 days. It was difficult to determine the exact date
on which natural incubation began. Incubating males developed an “incubation patch” –a patch
devoid of feathers located behind the sternum, on the abdomen and inner thighs (temporary
apteria), to improve heat transfer. The feathers that were shed were used for the nest lining.
During the incubation stage, the male usually leaves the nest for short periods during the day
(about 20 to 31 minutes), generally at the hottest time of the day. During incubation, the male
drinks and eats very little, living mainly on the fat reserves accumulated during the season when
feed intake is greater (autumn).
When natural incubation is used as a technique for reproduction management on a farm, one
problem is that embryonic development cannot be monitored. Another risk is that the male
might abandon the nest when certain kinds of disturbance occur. Specific pens need to be
designed and there has to be a high male: female ratio (near or greater than 1:5) among breeders.
Nests are usually made up of 20 to 30 eggs. If there are more, the male is less likely to be able
to provide adequate incubation. When males begin to incubate, the females are moved to other
pens with other males. When the chicks hatch, it must be decided whether to leave them with
the male for 3 or 5 months, or remove them within the first few days to be raised artificially.
Chick (“charito") raising. Average feed intake during the first 3.3 months (99 days) was 250-
300 g/day/animal.
Tables 1 and 2 show the data for live weight and daily weight gain during the brooding phase,
obtained at INTA-Bariloche and the farm “La Granja”.
For the juvenile categories, at least the following live weights should be recorded: hatch weight,
weight at the end of the brooding stage and weight at the end of the growout stage.
Table 1. Age and live weight of Choique chicks at the end of the brooding stage at different
ages.
EEA-Bariloche (INTA), Río Negro, Argentina.
Age (months) 2.4 (72 days) 3.3 (99 days) 4.2 (126 days) 5.8 (174
days)
Average Live Weight
(L.W.) kg.
8.666 10.656 14.141 18.045
Maximum L.W. kg 10.8 16.6 21.6 22.9
Minimum L.W. kg. 6.8 5.8 8.4 12
Average Weight gain
(WG)
(g/day)
109.1 99.5 110.5 105.5
Maximum WG (g/day) 135 145.1 160 133.7
Minimum WG (g/day) 95.6 51.5 68 77.1
n 9 46 72 33

19
Table 2. Age and live weight of Choique chicks at the end of the brooding stage for
different years, at “La Granja”, Neuquén, Argentina.
Year 2002-2003 2004-2005
Average age (months) 3.52 (105.6 days) 3.57 (107.1 days)
Average Live Weight (L.W.) (kg) 13.2 10.27
Maximum L.W. kg. 17.5 19.8
Minimum L.W. kg. 7 3.1
Average Weight Gain (WG)
g/day
120.4 93.6
Maximum WG g/day 168.5 133.9
Minimum WG g/day 85 54.8
n 33 44
Health. During the brooding phase (the first 3 to 5 months of age), affections occurred mainly
during the first three or four weeks, except for accidents. The most frequent problems were
impaction, infection of the umbilicus and/or vitelline sac, hypothermia (due to cold nights),
diarrhea – enteritis and leg problems. To a lesser extent, there were incomplete absorption of the
vitelline sac, broken bones and injuries, splay legs, intussusception, ulcer of the cornea,
prolapsed cloaca, twisted neck at hatch. It is worth highlighting that several cases of leg
problems were corrected by administering B-complex vitamins plus a mineral-polivitamin.
As rhea farming develops and the number of birds per unit of surface area increases, deficient
nutritional management, productive pressure and contact with other species are likely to create
conditions favorable to the appearance of new diseases, whether infectious or nutritional.
During the course of this study, small groups of 20-40 chicks were observed each year. Under
these conditions, survival rates were usually over 80%.
Growout. For this study, the growout phase was considered to be the period of growth between
the age 3 or 5 months and the beginning of an individual’s sexual development, usually
occurring between 20 and 24 months of age. For animals assigned to production of meat, hide,
etc. the growout phase ends at about one year of age.
At this stage, feed intake was de 500-550 g/ day/ bird of formulated concentrate. The food
conversion index during this stage varies from 5: 1 to 10: 1.
When conditions regarding nutrition, health, production control and selection are optimum, it is
feasible to produce animals for slaughter with the following characteristics: 22-24 Kg. live
weight at 8 months, 24-28 Kg. live weight at 10 months, and 28-30 Kg. live weight at 12
months of age (Table 3).
Table 3. Live weight and weight gain for Choiques at different ages.
Age (months) 3.3 (99 days) 5.5 (165 days) 14 (422 days) 27 (820 days)
Average weight Kg 10.2 17.4 28.4 32.3
Maximum weight Kg.
Minimum weight Kg.
16.6
5.6
22.9
12
33
24
37.8
26.3
Average Weight gain *
(WG) (g/day)
97.1 102 65.8 38.9
Maximum WG (g/day) *
Minimum WG (g/day)
145.1
51.5
133.7
77.1
74.8
56.9
45.6
31
3.3-5.5 (g/day)
109 (66 days)
Average WG for Period 42.8 (257 days)

20
5.5-14 (g/day)
14-27 (g/day)
11.5 (398 days)
Food Conversion Index
Period
2.5-3: 1 4-5: 1 11-12: 1 48-52:1
n 60 29 29 42
* accumulated
According to the data in Table 3, growth rate (g/day) and food conversion index (CI) show that
it is not worth extending the growout to slaughter beyond 14 months of age, because the growth
rate drops substantially and the CI reaches two digits (> 10:1). It may be estimated that weight
gain decreases as from 5.5 months of age by about 7.7 g per month. Thus, by month 12, a bird
would be gaining 60 g/day with a CI of 8.3: 1 and as from month 14, the CI would be 11.7: 1.
According to these data, when the growth rate is lower than 42.8 g/day, it is not worth extending
the growout phase when the priority is meat production, so the optimum age for slaughter is
considered to be 10-12 months. If the value of the hide, fat or larger muscle size (meat cuts)
made it worthwhile, the growout could be extended beyond 14 months.
A good strategy is to attain the highest weight possible by the end of the growout stage, making
the most of the greater daily weight gain during this stage, in order to shorten growout time and
minimize the time during which food conversion is inefficient, and, if possible, ending growout
before winter.
Reproduction. Both males and females usually attained sexual maturity between 20 and 24
months of age, although some precocious individuals matured between 12 and 14 months of
age.
The breeding season in Northern Patagonia, where this study was conducted, occurred from
April/May to December. The non-breeding season was from January to April. During that time,
both in the wild and on farms where natural incubation was used, the males were dedicated to
raising their chicks. In southern Patagonia, due to the weather, this behavior may occur up to
one month later.
The first breeding-related behavior (song and competition among males) was observed during
autumn (April – May). Sexual behavior such as wing spreading, courting and copulation
occurred in late June and July (winter).
Copulation lasted and average 3 minutes (maximum 18´; minimum 2.3´). The females that
copulated normally during the season, at least once before each oviposition, showed signs of
skinning, bruising, remains of skin, small blood clots and loss of outer feathers on their backs
(“mating patch”)
Nest building starts at the end of autumn (June), almost simultaneously with courting behavior.
The males may dig several holes before building the definitive nest. During the study, the males
built their nests at the same sites as previous years, and only changed sites if they were
disturbed.
The Oviposition season began in mid-winter (August) and ended in early summer (December).
The start of the oviposition season was linked to weather conditions during the previous months,
with harsh winters with heavy frost and heavy snowfall delaying it (September), and warm
winters bringing it forward (July).
Average duration of the breeding seasons during the study was found to be 136.7 days (4.5
months). The shortest season occurred in 1995, and lasted 77 days (2.5 months), while the
longest was in 2000 and lasted 186 days (6.2 months). Winter 1995 was the harshest since the

21
beginning of the study (1991). Average individual oviposition season (time between first and
last egg laid by an individual female) was 107.6 days (3.5 months).
The male to female ratio used during the study was 1 M : 3 F.
Fourteen-year-old females still form and lay eggs.
Egg features. Eggs are light green and speckled with white spots (calcium phosphates; Cremona
V., 2004) of varying in size and distribution. Eggs are usually oval, with one pointed tip and one
rounded tip, but a few may be long or nearly round. Eggs without a shell are occasionally found.
Average egg weight was 620-650 g (maximum 875 g; minimum 385 g). Some very small eggs
weighing 250-350 grams were found. Length (longitudinal or greater axis) was 12.5 to 14.5 cm,.
and width (transversal or lesser axis), 8.5 to 9.5 cm.
Monitoring of female production. Females were monitored during this study (in Trelew and
Bariloche) with the aim of describing their behavior during oviposition, and it was found that
there is an optimum egg-laying time (the last hours of daylight, between 3:30 p.m. and dusk).
Each female was found to produce an egg type having its own particular features (“shape”),
which lasts throughout her lifetime. The distinctive shape of the eggs laid by each individual
female enabled us to monitor them. This method can be used for breeding groups of not more
than 5 or 6 females.
The following features were considered to determine egg shape: silhouette (oval, long, tear-
shaped, rounded, etc.); color, type of shell (smooth, porous, etc.); scars or marks; size and
distribution of the white speckles, weight (g); length (cm), width (cm). All these data are
complemented by information regarding the pen of origin, date and time of laying.
Considering the number of eggs laid and their average weight, the production in egg weight
(Kg) produced by each female per season is obtained. Table 4 shows that females H4 and H40
produced 70 to 85 % of their live weight (May/June) in eggs during a season. These females are
considered to have high production. Other females, such as H21, which produced 16.9 % of her
body weight in eggs, are classed as having low production.
A complete “productive profile” is constructed for each female by considering both oviposition
capacity and data regarding the fertility and hatchability of her eggs. Then, by adding
information on the survival, growth rate, conversion index, live weight, slaughter yield, etc. of
her descendants, a complete data base (production control) can be set up and used for making
adequate selection choices.
There should be genetic diversity within the Choique stock in order to avoid inbreeding. Within
this diversity, there will be some birds whose behavior or productive features are inappropriate
for breeding in captivity, and these should be removed from the system. It is more efficient to
keep a high production female than one with low oviposition, since both will have similar food
intake.
The weight of the eggs that each female lays is not constant throughout the season. Egg weight
may vary by over 100 g. Egg shape, however, does not change.
The interval of time between two consecutive eggs laid by one female varies according to the
time of the laying season considered. For example, for female H40 (Table 4), if the entire
season is considered, the interval is 2.8 days, but if maximum egg-laying periods are
considered, it is 1.8 days. This is because there are periods of time (days or weeks) during the
season when no eggs are laid due to the weather conditions or to individual factors.

22
Table 4 Egg-producing capacity of seven females. EEA-Bariloche (INTA).
Female
Nº 4
Female
Nº 5
Female
Nº 6
Female
Nº 7
Female
Nº 21
Female
Nº 40
Female
Nº 54
Length of oviposition
(days)
145 106 109 104 74 126 86
Number of eggs 43 37 35 30 14 44 25
Interval between eggs
(days)
3.3 2.86 3.1 3.4 5.2 2.8 3.4
Average egg weight
(grams)
623.4 587.4 687.3 628.5 561.3 658.7 653.3
Total grams of eggs
produced
26.809 21.733 24.055 18.856 7.858 28.986 16.333
Live weight females
(May/June)
35.4 36.2 32.6 33.4 46.4 34.4 39.4
Ratio grams produced/
live weight female (%)
75.7 60 73.7 56.4 16.9 84.2 41.4
Table 5 Duration of oviposition, number of eggs, fertility and hatchability for females Nº 4 and
Nº 40 (EEA-Bariloche).
Female Nº 4 Female nº 40
Oviposition duration (days) 156 126
Number of eggs 48 44
Number of fertile eggs 36 28
Fertility % 75 63.3
Number of hatched eggs 20 19
Hatchability % 55.5 67.8
Body Weight of Breeders. Adult Choique live weight is always recorded one month prior
(May/June) to the beginning of reproductive behavior (copulation, oviposition). Average live
weight for adults was 38.4 Kg. For males, live weight was 41.7 Kg, while for females, average
live weight was 35.2 Kg. Average weight for females was 15.5 % lower than for males. Table 6
compares these data with those obtained at the farm “La Granja”.
During the year there are fluctuations in live weight according to the season and to sexual
activity. During the breeding season, all birds lose weight – males lose weight due to the
expenditure for incubation, fighting, courting, copulating, etc., and females due to oviposition,
copulation and a certain anorexia (Angel, 1996). Weight loss for both sexes is in the range of 15
to 20 % of the live weight recorded at the beginning of the breeding season (May/ June). During
the months following breeding (January – April) the adults regain lost weight, and this is the
time of year when feed intake is greatest. To keep a good record of the annual evolution of live
weight of breeders, they should be weighed before (May/ June) and after (February/ March) the
breeding season.
Table 6. Live weight of adults compared between INTA-Bariloche and the
farm “La Granja”.
INTA-Bariloche La Granja
Average live weight kg
Maximum weight kg
Minimum weight kg
38.4
48.8
26.6
32.1
38
26.3
Average weight Males kg
Maximum weight kg
41.7 (n=6)
48.8
34.2 (n=22)
38

23
Minimum weight kg 36.5 26.3
Average weight Females kg
Maximum weight kg
Minimum weight kg
35.2 (n=14)
46.6
26.6
30 (n=20)
34
26.5
Difference between M and F 6 (15.5 %) 4.2 (12.1%)
Age years > 2 >2
Time of year May/ June March
n 20 42
Table 6 shows the live weights recorded at INTA-Bariloche and the farm “La Granja”. The
difference in average adult weight is attributed to the fact that weights were recorded at different
times of year. At INTA-Bariloche, weights were recorded during May/June, when the birds’
physical condition was at its best, while at La Granja, weights were recorded in March, when
the birds were recovering their breeding expenditure and needed to accumulate reserves.
Food intake. For adults (breeders) annual intake of formulated concentrate was 669 g/day /bird,
or sometimes less if complemented with grazing. Feed intake is not constant throughout the
year, but varies according to reproductive behavior. During the breeding season, both males and
females eat less and increase their energy expenditure; e.g. during natural incubation, males
hardly feed, and live on reserves (fat) accumulated during the non-breeding season (autumn),
while females spend energy on egg production. Thus, during the breeding season, their feed
intake drops by up to 40-50%. This pattern is similar for emus (Angel, 1996). Annual feed
intake follows a curve which is equivalent to the curve for the evolution of live weight, but
precedes it (the birds feed first, then weight gain). The greatest intake can therefore be seen to
occur in late summer – autumn (900-1000 g/ day/ bird) and lowest intake (350-450 g/ day/
animal) during the breeding season (July – December).
Graph 1. Graph showing annual intake of formulated concentrate by adult
Choique, INTA- Bariloche.
Hybridization. Beginning in 1997, a series of experiments was conducted with the aim of
finding out if it is feasible to produce hybrid birds by crossing different rhea species (Rhea
americana and Rhea pennata).
From a biological standpoint, the purpose of producing hybrids is to gain further knowledge,
while from a production standpoint, it is to seek a possible method for increasing individual
rhea productivity, i.e. to maximize the reproductive and/or productive efficiency of individual
birds and hence, of the system.

24
This line of work aimed to ascertain whether, in addition to the biological feasibility of
producing hybrids, there was Hybrid Vigor or Heterosis (“the superiority of crosses (F1) as
compared to the progenitor lines (F)”), regarding some trait which would be useful to
production (growth rate, body weight, feed intake and conversion; number of eggs, fertility,
survival, etc.). The “industrial cross breeding” technique is widely used, both in modern poultry
production and traditional livestock farming (cattle, sheep, swine, etc.).
In order to try to prevent behavior barriers from appearing during the breeding season, chicks of
both species were raised together from the time they hatched.
First of all, attempts were made to cross the species, for which two breeding groups were set up,
with Ñandú común and Choique males as fathers.
It was possible to produce hybrid ÑC (Male) x CH (Female); but so far it has not been possible
to get CH (Male) x ÑC (Female) to mate naturally. In this case, females (ÑC) showed
willingness to mate, but males (CH) were reluctant to do so, although they did mate with
females of their own species. Attempts to achieve this cross will continue to be made.
At present, the Hybrid lot is made up of 22 birds.
Results of the crosses attempted so far are:
Ñandú común (Male) x Choique (Female): eggs and fertile descendants (F1: ÑC x CH).
Hybrid (F1) x Hybrid (F1): eggs and fertile descendants (F2).
Hybrid F1 (Male) x Choique (Female): fertile eggs and descendants.
Choique (Male) x Ñandú común (Female): no mating occurred.
Ñandú común (Male) x Hybrid F1 (Female): no mating or egg laying occurred.
Characteristics of Hybrid F1 (ÑC x CH). The descendants of the cross between pure rhea
species are morphologically similar to the Ñandú común. They have slightly “brownish” gray
feathers, which are uniform over the entire surface. Black patches on the head, neck and breast
are absent or very pale. The white patches which are typical of the Choique can only be seen on
adult hybrids as small white bands on the breast area (pectum); which become noticeable after
sexual maturity is attained, though to a lesser degree than in the Choique. The iris is a light
grayish-green color. The scales or keratinized epidermal rings covering the tarsus-metatarsus
(podotheca) are similar to those on the Ñandú común, but cover only the lower two thirds;
above which there are polygonal scales, as in Choique. Body height (digits-crown) is equivalent
to the Ñandú común. Body mass, especially in females, is greater than in ÑC progenitors. This
outward appearance of birds of this class is uniform.
Average F1 chick weight at hatch is 431.3 grams (maximum 530 g; minimum 380 g) equivalent
to 65.3 % of initial egg weight. Incubation period was 37.25 days (maximum 40 days; minimum
35 days).
Growth and body weight of F1 hybrids was estimated during an indoor trial (without access to
brooding pens) together with Choique chicks. Brooding conditions were the same for both, and
the trial lasted from hatching to 6.4 months of age. The growth rate for F1 chicks was 18 %
higher than for Choiques, with F1 chicks reaching the same live weight as Choiques 36 days
earlier.
Table 2. Average weight of Choique chicks compared to Hybrid chicks.

25
Average age
Months days
Live weight
average kg
Average gain
g/ day
Live weight kg
Maximum Minimum
Choiques 6.4 (192) 21.08 111.36 22.9 18.8
F1 Hybrids 5.2 (156) 21.795 136.25 23 21
F2 Hybrids 5.5 (166) 8 45.4
Once F1 chicks reached sexual maturity, at two years of age (some specimens attained sexual
development at one year of age), they mated naturally, producing fertile eggs.
F1 eggs were similar to ÑC eggs: yellow-colored with a subtle greenish tint, without white
speckles. Laying hours were similar to those of Choique females (from mid-afternoon to dusk).
These eggs were larger than those laid by pure species, weighing an average 725 grams
(whereas average Choique egg weight was 620-650 g).
The oviposition season began in September and ended, as for Choiques, in late December / early
January.
The pattern of annual feed intake for F1 hybrids was similar to Choiques; with a minimum
during the breeding season (September) and a maximum during the non-breeding season
(February-March).
Based on personal observation during the daily handling of different species, it was noticed that
the F1 hybrids had the most docile behavior, while the Ñandú común had the most nervous or
excitable temperament, and the Choique was somewhere in between. The docile character of the
hybrids was apparent either during handling maneuvers or due to the fact that they were not
aggressive towards humans during the breeding season.
Characteristics of F2 Hybrids (Hybrid F1 x Hybrid F1). The descendants obtained from crossing
F1 hybrids is called F2. Average hatch weight for F2 Chicks was 446.5 grams (maximum 539
g.; minimum 400 g) equivalent to 61.5 % of initial egg weight.
The viability of F2 chicks was not good during the first seasons, but improved during the last
season when Relative Humidity during incubation was reduced to 42%.
Backcrossing of Hybrid F1 (Macho) x Choique (Female). This cross was done for the first time
during the 2004 season. A trio made up of one (1) male and two (2) females was set up.
Average weight of the chicks hatched during the hatching season was 393.8 grams, equivalent
to 64.2 % of initial egg weight.
Up to their present age of 4.5 months, their growth and development has produced a variety in
size and morphology. Some have grown well, while others show little growth for their age.
Average live weight at this age is 12.4 kg. (maximum 18.5 kg.; minimum 4.2 kg.; n= 7);
average weight gain up to 4.5 months of age has been 87.2 g/ day (maximum 128.2 g; minimum
26.9 g/day).
Their appearance and plumage (ptilosis) are similar to the Ñandú común; the iris is light
greenish to light brown; they have keratinized epidermal rings similar to those of the Ñandú
común only on the lower third (distal epiphysis) of the tarsus-metatarsus (“leg”), while the rest
of the bone is covered by skin with rounded, keratinized epidermal “scales” similar to those of
the Choique. Like Choiques, they have feathers on the upper third of the “leg” (proximal
epiphysis). This appearance may undergo changes as the birds grow into adults, particularly
after sexual maturity is attained.
Backcross Ñandú común (Male) x Hybrid F1 (Female). In another pen, a pair of adults was set
up (1 Male and 1 Female), aged 12 and 5 years respectively. This pair was not observed to mate

26
or lay eggs, possibly due to the female’s lack of reproductive behavior, although the male did
show reproductive behavior and even built a nest. It is assumed that female’s behavior was due
to the fact that she was moved to a different pen after the start of the season (stress).
Conclusions.
Sustained rhea production, whatever the species or farming system implemented (extensive,
intensive, etc.) could be a farming option which would complement and diversify traditional
livestock farming in marginal areas such as Patagonia. Rhea farming, based on the use of an
autochthonous wild species, should produce sustained economic benefit and guarantee the
conservation of wild rheas. All farmers, businessmen, professionals, etc. involved in the value
chain should be aware of and take part in the protection of wild Choique populations, to ensure
their survival and well-being (Wildlife Welfare). These wild populations should be used only as
a source of new “genes” to add to captive stock.
Rhea farming in Argentina today is somewhere in between the “breeder selling” stage and the
“product selling” stage. To enter the “product selling” stage competently on national and
international markets, we need to overcome the limitation posed by the lack of slaughterhouses
legally authorized by the national authority for Animal Sanitation (SENASA) for the slaughter
of rheas.
Although a model for rhea production has been implemented in South America, there is still
room for improvement, because biological and productive knowledge of this species is being
gained together with the design, implementation and ordering of a productive system. Present
knowledge enables sustainable rhea farming, but in order to increase efficiency, further
knowledge is needed in certain fields (behavior, breeding, nutrition, sanitation, economy,
product development, etc.).
We need accurate knowledge of the nutritional requirements, especially vitamins, mineral traces
and essential acids for all categories of birds. Regarding sanitation it is essential to conduct an
in-depth diagnostic survey of the infectious affections (bacteria, virus, etc.) that arise when
rheas are farmed, especially the Chick category.
Finally, substantial investment (government and/or private) in research and industrial
infrastructure is needed in order to develop, expand and perfect the system,. Thus, farmers
would be encouraged to invest in equipment, infrastructure and training in order to improve
their productive parameters. Professionals would to specialize in Nutrition, Reproduction, etc.
and farms would be encouraged to specialize in one stage of the system (e.g. fattening). Birds
for reproduction, and their descendants, should be carefully selected and monitored, in order to
achieve the genetic improvement of the stock reared in captivity, because at present, not all
adults used as breeders are really efficient.
Once present limitations have been overcome, prospects for Choique production look
promising, thanks to the unquestionable quality and usefulness of their products.
The data on body weight presented in this paper were obtained from regularly monitored birds
hatched from wild eggs, and provide new information on Choique growth, development and
productive potential. This weight monitoring technique should be applied at all farms for all
Choique categories. At least the following weights should be recorded at all farms: hatch
weight, weight at the end of the brooding stage , live weight at the end of the growout stage and
live weight of breeders before and after the breeding season.
Another way to increase productive efficiency is by means of inter-species cross breeding
(Hybrids).

27
In order to work out final considerations on the use of Hybrids in the production system, further
research should be conducted on a greater number of birds, which should be of high genetic
quality. Some positive features observed in hybrids so far are: 1-Fertility between pure species
and their descendants (F1); 2-Favorable growth rate during the first months for F1 (136.25
grams/ day).
In the light of the results obtained from rhea hybridization, it would be timely to conduct a
taxonomical revision of the genera, species and subspecies in the Family Rheidae.
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Acknowledgements: We would like to thank Julio Cesar and Jorge Rene Laurin of “La Granja”
farm for their cooperation; the company ALIBA S.A. for donating the feed for the study; and
Nestor Maceira for reviewing the manuscript so thoroughly.

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