Page 94 - Hand rearing birds second

78 Hand-Rearing Birds

Table­4.1­ Incubation parameters for ratites.

Egg­Weight­ Relative­ Days of Weight­Loss­ Approx.­Chick­Weight­
Species (g) Temperature Humidity Incubation over­Incubation at­Hatching­(g)

Ostrich 1300–1700 36.0–36.5 °C 20–40% 42 15% 860–1100
96.8–97.7 °F
Emu 550–600 36.1–36.4 °C 25–40% 50–52 10–15% 360–400
97.0–97.5 °F
Rhea 500–800 36.4 °C 30–60% 36–40 15% 330–530
97.5 °F
Cassowary 500–800 35.5–36.7 °C 57–64% 47–57 12–15% 330–530
95.9–98.1 °F
Kiwi 400–450 35.5–36.5 °C 60–65% 70–90 280
95.9–97.7 °F

Although recommended incubation parameters are listed in many texts and references (Jensen
et al. 1992; Tulley and Shane 1996; Huchzermeyer 1998; Minaar 1998; Doneley 2006; Romagnano
et al. 2012; Biggs 2013), considerable variation can result from farm and location‐related factors,
such as type of incubator, number of eggs being hatched, and ambient temperature and humidity.
General incubation guidelines are presented in Table 4.1.
The environmental quality inside the incubator is of paramount importance to embryo develop-
ment and growth. Eggs should be examined and weighed at weekly intervals to ensure that weight
loss and embryo development are progressing appropriately. As in other avian species, abnormal
embryo development and embryonic mortality may be associated with elevated or depressed tem-
perature or humidity, with inadequate or inappropriate egg‐turning, or with bacterial or fungal
contamination. Adequate air flow through the incubator is particularly important to provide suf-
ficient oxygen for the large embryos and to ensure that incubator temperature does not rise exces-
sively. Specific incubators are manufactured for ostriches and emus in order to provide the
appropriate frequency and mechanics of egg rotation. Ostrich eggs are set air cell up, and are
rotated over a 90° arc, 45° each side of vertical. Emu and cassowary eggs are generally laid on their
sides and are rotated back and forth around the long axis with a series of roller bars. Visual assess-
ment of embryonic development (i.e. candling eggs) requires strong light sources to pass through
the thick shells of ostrich and rhea eggs. An infrared candler may be used for dark‐shelled emu
eggs (Figure 4.2).

­ Initial­Care,­and Stabilization

Ratite eggs are moved to a hatcher 1–4 days before the end of incubation to provide higher humid-
ity, slip‐free flooring, and reduce contamination in the incubator. Chicks may take 1–3 days from
internal pipping (entry into the air cell) to external pipping (opening of the shell). It may take
several hours to days for the chick to fully emerge from the egg. Ratite chicks open their shells by
a combination of pushing with their legs and head. Hatching problems are almost always a result
of weak chicks due to incubation difficulties, inadequate nutrient stores provided by the hen, or
embryonic developmental anomalies. It is a quite common practice to assist hatch in ostrich chicks