ARTIFICIAL INCUBATION APPLIED TO SMALL NUMBERS OF ALTRICIAL BIRD EGGS
Artificial Incubation Applied to Small Numbers of Altricial Bird Eggs : Part 4


Incubation Room

The room where the incubator is located should be climate controlled at levels which assist the incubator rather than make it harder to meet the correct conditions for the eggs. Room temperature is best maintained between 24-26C (75-80F) and humidity between 60 to 70% r.h. Incubator heaters that are switched on frequently have a drying effect and activate humidifiers which tend to have a cooling effect. One system aggravates the other, producing poor conditions for incubation thus their use should be minimized by having stable room conditions.

Room temperature should not be too high or overheating and embryo mortality may occur. Some rooms are blessed with naturally ideal humidity conditions all year round, but with many it is necessary to add or remove moisture from the air. Humidifiers are especially important during dry periods such as in the winter and dehumidifiers during hot and humid summer weather. In areas where the climate is often hot and humid an incubator that has both minimum and maximum temperature and humidity controls may be the safest unit to use.



Fertility and Hatchability

Poor fertility and hatchability can be due to a number of factors including poor parental nutrition, poor parental stock (old or infirm birds), inbreeding, infection of the egg and improper incubation conditions (Flammer, 1984). Too low or too high incubation temperature and/or humidity may result in a delayed or early hatch of weak chicks with unretracted yolk sacs or death as chicks stick to the membranes or drown in excess fluid. A study of 1200 bugerigar eggs which failed to hatch found 73.3% to be infertile or clear, 14.8% as dead in shell mainly due to infections but also malposition, 11.1% because of early embryo death due to rupture of the yolk, infections or no specific cause, and about 1% due to deformed shells or lack of a yolk (Baker, 1988). Staphylococci was the most common bacteria found in infected eggs along with Streptocci, E. coli, Corynebacterium and Pseudomonas in that order of occurrence (Baker, 1988). This study shows the importance of egg sanitization to achieve maximum hatching rates.



Nutrition

Of 133 necropsies of embryos which failed to hatch or chicks which failed to survive the first month at the New York Zoological Park, 52 had lesions suggestive of a nutritional deficiency (Dolensek et al., 1979). This study found that chicks which failed to pip properly had myopathy of the hatching muscle (musculus complexus) as the most common malady. The hatchling's muscles were enlarged from edema, hemorrhage and necrosis suggestive of vitamin E and selenium deficiency (Dolensek et al., 1979).

The importance of vitamin supplementation of seed diets was demonstrated by Roudybush (1984) who found a hatchability of 68% in cockatiels fed a vitamin supplemented diet with only 20% of fertile eggs hatching on an unsupplemented diet. The diet was a standard Cockatiel seed mix (6 parts millet, 2 parts canary seed, 1 part each sunflower, safflower, and hulled oats by weight) to which 10% hulled millet was added. The supplemented group received the vitamins coated on the hulled millet.

Thus it is important to have a sound feeding program in place which supplies all the required nutrients to a laying hen. Especially important for multiple clutching and maximum egg production is the level of calcium in the diet as egg shells are primarily calcium carbonate. The importance of calcium homeostasis is further demonstrated by its essential role in hatching muscle contraction during the hatching process (George, 1978). Most breeding pellets have adequate levels of these nutrients but if seed or bean-vege diets are being fed then a vitamin-mineral supplement formulated to meet the deficiencies of these diets must also be given daily. Mixing pellets with seeds will not provide a complete diet to birds who only select out and eat their favorite seeds and simply crush the pellets or throw them to the side.



Assisting a Piping Chick

A chick which has piped but does not rotate may be saved with some delicate and risky assistance. This usually happens when the incubation humidity is too low and excessive water loss has resulted in the lack of proper lubrication of the membranes surrounding the chick. Do not mist the egg shell directly as this may drown the embryo or draw further moisture out of the egg, depending on the temperature of the egg and water.

Only, if after three days of piping the chick has not progressed in its rotation could it be carefully helped. Remove the shell above the air cell line with a pair of tweezers and lightly wet the membrane covering the chick with a fine mist of sterile warm distilled water, saline or lactated Ringers solution. If there are no blood veins within the membrane it can be cut and the head freed. Place the egg back into the hatcher, occasionally wet the membranes covering the chick and hope the chick will free itself. Death usually occurs when assisting chicks which have not yet resorbed the blood from the vessels in the egg membranes. It appears that the chorioallantoic circulation remains functional until shortly before hatching and remains even when yolk resorbtion is complete and the embryos are vocalizing (Bucher and Barnhart, 1984). Thus the correct time to assist an egg is hard to judge and its better to wait rather than have a chick bleed to death in your hands.

Some of the birds that HARI has tried to help out had unabsorbed yolk sacs. These eggs were sometimes first incubated by the parent birds who may not have kept the eggs warm enough and thus slowed their development or they were amazon and macaw eggs which may have not lost enough water during incubation. If you see an unabsorbed yolk sac immediately stop breaking away the shell and place the egg back into the hatcher. Hopefully the chick will free its self once the yolk sac has been absorbed. To speed up drying and prevent infection, swab some diluted tamed iodine onto a raw umbilicus or unretracted yolk sac.

Trying to assist a hatching egg can be very frustrating with most cases usually dying. All efforts should be made to have the correct incubation conditions so that eggs hatch naturally.



Summary

The best results in artificial incubation of bird eggs are achieved with; the careful collection and preparation of clean eggs; the use of a modern, automatic turning, forced air circulated incubator with reliable and steady solid state temperature controls. There are many new models of small scale incubators now available (Appendix 2). Some with advanced features are rather expensive but the hatching of just a few additional valuable parrot chicks can remunerate the increased cost.

Artificial incubation can be frustrating; it can be an art as well as a science. However loses as well as successes provide experience and information on each particular set-up and corrective measures can then be taken. Unfortunately some breeders operate on a trial and error system, waiting to see if their eggs will hatch under the conditions they have set up and only changing the conditions based on the way the eggs have died. Measuring the rate of egg weight loss and comparing it to accepted ranges can indicate if humidity changes are required before the egg is lost.

The optimum incubation temperatures for altricial bird eggs in forced air incubators appears to be between 36.9-37.5C (98.5-99.5F). The mean overall fractional weight loss (the percentage of the initial egg weight lost) (fn) for most altricial species is in the range 12-16% with the freshly laid to pip loss in the range 10-14%. The optimum fn for individual species may fall at either end of these ranges. It appears the level of incubator relative humidity needed to achieve maximum hatchability in some species is higher than those previously documented. More controlled scientific studies are needed to compare incubator relative humidity, egg weight loss and hatchability.

Once eggs have piped they should be moved to a hatcher which has a much higher humidity and slightly lower temperature than the incubator. Hatching takes about two days and then the laborious task of feeding a blind, helpless altricial chick can begin.



Part 5: References
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