Mark Hagen, M.Ag.
Review Performed at:
Department of Animal and Poultry Science
University of Guelph
Guelph, Ontario, Canada
The egg is one of nature's most incredible self-contained life capsules. It contains all of the balanced nutrients and, if fertilized, all of the genetic material for the creation of a new life.
Artificial incubation goes back thousands of years when the ancient Chinese and Egyptians operated large hatcheries that were quite successful. Up until ten years ago most of the scientific information concerning artificial incubation applied to precocial species important to the poultry industry. Presently large commercial poultry incubators fit tens of thousands of eggs at a time and, due to selection, most hatch.
The incubation of exotic bird eggs, usually in small numbers, has recently become a popular way to try and increase production but unfortunately often leads to failure. There is a desire to improve artificial incubation techniques as diets to hand-feed altricial birds right from hatch are becoming available and more breeders are confident that they can raise a baby themselves.
The topic of incubation could fill a book with many different techniques leading to a successfully hatched egg. Having the right equipment is as important as knowing the process. Temperature, humidity, ventilation, egg turning and sanitation are all important factors in the proper incubation of eggs (Brown, 1979). This paper will discuss these factors as well as some characteristics of parrot eggs, their proper collection and assistance techniques for dried out eggs.
Benefits of Artificial Incubation
The production of rare avicultural species can be significantly increased by artificial incubation. Eggs normally lost to parental neglect, predation, extremes of environmental conditions, pathogen infection and other calamities can be saved (Reininger, 1985). Many pairs lay a second clutch and in some cases triple clutch to replace eggs that are removed.
Van Der Heyden (1987) claims that artificially incubating to increase egg production is risky and that many aviculturists have lost more than they've gained by it. This may be due to improper techniques, poor parental nutrition and other factors that can be corrected.
Surrogate/foster parents have been successfully used to incubate and raise eggs (Gee, 1983; Harrison, 1987; Stoodley, 1984) with the same benefits as artificial incubation. Some species, such as the Monk Parakeet, make better foster parents than others. Possible disease spread, unacceptance by the foster pair and the cost (space) of maintaining them are factors which may make fostering less desirable.
HARI raised 12 babies from one of our Blue & Gold Macaw pairs which produced 18 eggs in 14 months. The first two clutches were pulled for artificial incubation within a week of being laid. Then, twice they laid again a month after we pulled three week old babies from them. Unfortunately the demand for unrelated, parent raised, captive bred breeding stock is rather small. As a result, we have to incubate (or pull at a very young age) and hand rear most of our babies for pet stock.
In different species of birds that have the same egg weight the incubation period is inversely related to the metabolic rate and the egg shell gas conductance (Rahn et al., 1974) thus similar sized eggs from different species may have different incubation periods.
The contents of fresh psittacine eggs contain slightly more solids, 19.4% (Bucher, 1983) than is typical for altricial, or semi-altricial species, which contain 17% solids (Ar and Rahn, 1980). When compared on the basis of maturity at hatching, the water fraction is significantly different between fresh altricial and precocial eggs which contain 28% solids (Ar and Rahn, 1980).
In six parrot species studied by Bucher (1983) the average incubation period was 40% longer than that of birds in general, when compared on the basis of egg mass using the data compiled by Ar and Rahn (1978), and because of the prolonged incubation periods the total embryonic energy metabolism is greater than predicted for altricial species. Bucher (1983) found that pre-piping and hatching levels of oxygen consumption are lower than in the same size eggs of precocial species.
Clutch size within the psittacines varies from one egg up to six, with two or three being average for most species (Saunders et al. 1984; Smith and Saunders, 1986;
Saunders et al. (1984) found that amoung the graminivore-frugivores, the hole-nesting psittacines produce larger clutches, have longer incubation and nestling periods than the open-nesting Columbiformes.
Egg Collection and Record Keeping
Eggs left with the parents for several days of natural incubation before artificial incubation has been found to increase the hatchability (Burnham, 1983). To enhance successful copulation in wild pairs that are easily stressed, no eggs should be collected from the nest boxes until clutch completion. Some pairs do not incubate their eggs well if at all and their eggs must be pulled immediately for artificial incubation. To check for proper brooding with pairs which may leave the nest before they can be observed, one must feel the eggs (with clean hands) for warmth.
When an egg is pulled, it is labelled with a code representing the species, pair (A,B,C,...) and egg number. For instance the eighth egg from our second pair of Blue & Gold Macaws to breed is labelled BGM-B-8. The seventh egg from our third pair of Medium Sulphur-Crested Cockatoos MSC-C-7, etc. By using a soft carbon pencil every egg is identified along with approximate date of lay. Eggs left with the parent pair are not labelled but are recorded.
Rowe (1986) describes a portable incubator used to transport eggs collected in the wild and brought into captivity.
Disinfection of Eggs and Incubator Prior to Incubation
Eggs laid in dirty boxes can be covered by contaminating microorganisms from the feces or feather material of the parents or previous nestlings. There is some controversy as to benefit of cleaning, washing, treating with antibiotics or disinfecting eggs. It may be best to leave very dirty eggs in the nest but if they are to be set, some cleaning and disinfecting should probably be done. Even visually clean eggs may harbour a significant amount of bacteria or viruses on their shells and unless disinfected can spread this to other eggs in the incubator.
Eggs which have been soiled by feces can be carefully dry cleaned with fine sand paper or steel wool. Gently flick away the feces and minimize scratching the cuticle or pressing the dirt through the pores and into the egg.
Older egg submersion washing systems used by the poultry industry often served to spread and multiply bacterial contamination if wash water was too cold or re-circulated too often inactivating the disinfectant. When the wash water has a lower temperature than that of the eggs, the result is a cooling and contraction of the egg contents, which serves to draw wash water and associated bacteria through the shell pores contaminating the egg.
This temperature-differential effect has been used to introduce into eggs both water, if they have lost excessive weight (Gee, 1983), and antibiotics to control certain egg-transmitted bacterial infections (Ekperigin and McCapes, 1977). Eggs are preheated in a disinfectant solution and then immersed in a cold antibiotic solution for 2.5 minutes with no adverse effect on hatchability (Ekperigin and McCapes, 1978).
When the goal is to remove the surface contamination, all eggs should be dipped in a disinfectant solution which is always warmer than the egg, carefully wiped with a paper towel (which is dipped often to warm it up and clean it) and then quickly dried. New automated washing systems use a warm pressure wash spray containing a detergent, a hot water rinse containing a disinfectant and air blow drying (Kuhl, 1988).
Mandl et al. (1987) studied the efficacy of various disinfectants on broiler breeder eggs contaminated with salmonella. No adverse effects on hatchability were obtained when fresh eggs were soaked in 2 % solutions of aldehydes, phenols or quaternary ammonium compounds for five minutes but were significantly reduced by a 5 % solution of an iodophor compound.
Fumigation of eggs has been a common method to kill shell surface micro-organisms. Fumigation should only be done with fresh eggs, older eggs can be killed. Incubators made out of porous wood or polystyrene and others with hard to reach areas can only be effectively disinfected by fumigation. Researchers at the University of California, Davis fumigate using 1.22 ml formalin (37% formaldehyde) and 0.6 g potassium permanganate per cu ft of incubator for 20 minutes (Cutler et.al., 1985). However, egg fumigation is dangerous to the breeder who can not exhaust it directly outside after fumigation. The gas is poisonous and smells horrible. It is also inconvenient for the average breeder who has small numbers of eggs over a longer period of time.
Delaying the setting of eggs allows a larger number of them to be set at the same time. This technique saves labour and simplifies the incubation and transfer of large numbers of eggs to the hatcher. It is also used by researchers studying diets, as the growth of baby chicks can begin at the same time.
Hatching eggs can be stored under appropriate conditions for up to a week prior to incubation without a significant loss in hatchability. Pre-incubation storage of cockatiel eggs at a temperature of 13°C (55°F) and relative humidity of 60% does not reduce hatchability until after four days of storage (Cutler et. al., 1985).
Cutler et. al. (1985) demonstrated that bagging cockatiel eggs during the storage period appeared to increase the storage time and improve viability. Storage of the eggs in plastic bags appears to reduce the rate of dehydration and pH change due to CO2 loss from the egg.
It is recommended to gradually warm cooled eggs from storage up to room and then incubation temperatures (Haigh, 1984).
For most exotic bird breeders working with small numbers of rare and valuable eggs, the risk associated with storage is unwarranted and the technique is not really needed.
Setting and Turning
When setting in trays, the proper orientation of the egg during incubation is with the small end pointed down. The air cell should grow at the blunt end. There is some controversy over the positioning of the egg, in a tray or on rollers. Most trays are held at 45° and rotate the eggs 90° from one side to the other, although the eggs are held in the vertical position in the tray. Rollers are able to turn the eggs completely and the eggs can be set in a more natural horizontal position. No scientific studies have compared rollers vs. trays although some breeders report better success with rollers.
Turning prevents the embryo from fusing with the eggshell membranes. If this happens the embryo will stick to the shell and development can be fatally distorted or the chick may be malpositioned for proper hatching.
Cheaper incubators are available with manual or hand turning but the savings are questionable for several reasons. Eggs should be turned at least three times a day or better still once every two hours for the first 75% of the incubation period. Manual turning may simply require turning or pulling a knob but forgetting to this will reduce hatchability. Turning eggs directly by hand has many risks including; contaminating the eggs with micro-organisms, damaging the eggs by careless turning, or twisting the embryo by turning in the same direction and forgetting to turn them.
The turning of chicken eggs can be stopped at 16 days (normal incubation period 21 days) without adversely affecting hatchability (Wilson, 1988).
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