Continued from page 4

The "ideal" incubator

The ideal incubator serves as a "room within a room". The incubator should be able to provide its desired incubation parameters while resting in a thermostatically and humidity controlled room that remains independent of daily climactic conditions. Without this type of control, fluctuations should be expected within the incubator unit. Construction of this unit should be with nonporous materials for two reasons: improved temperature and humidity control and improved ability to effectively clean and sterilize.

Temperature:

The temperature settings of the incubator generally control the developmental speed of the embryo. Individual testimonials of temperatures ranging from 99.0 to 99.3 F( 37.2-37.4 C) have proven successful for psittacine egg incubation. The heat of the incubator should be consistent, and uniformly distributed within the unit. Consistency and accuracy is attained by regularly monitoring temperature with multiple thermometers. It is not recommended that the operator "trust" any one thermometer or piece of monitoring equipment. Uniform distribution of temperature is accomplished through the air circulation (fan) system within the unit. Those units with low air turnover should be expected to vary in their ability to distribute temperature evenly throughout the unit - particularly when the unit becomes progressively filled with eggs. Those incubators that have been altered for improved ventilation may actually have induced an increased temperature variability through increased heat loss.

Humidity:

Relative humidity controls the rate of weight loss of the egg during the incubation process. As the eggs are incubated, weight loss through water evaporation is a normal process. "Wet chicks" is a term used to describe chicks that have demonstrated inadequate weight loss during the incubation process. "Wet" altricial chicks tend not to show the classic edema demonstrated by precocial chicks, but may simply have a weaker than normal hatch, increased tendency to splay the legs and possibly immunosuppression linked problems. "Dry or sticky chicks" generally refers to those birds that have lost excessive weight during the incubation process.

Egg turning:

Rotation of the eggs is perhaps one of the most overlooked aspects of incubation. Turning the eggs is mandatory to allow for uniform development of the vascular supply of the embryo throughout the embryonic membranes. Without this web of vessels, the developing embryo will become deprived of adequate oxygen exchange and can potentially die. General poultry recommendations for egg turning are a 90 degree turn, a minimum of four times per day. The turning mechanism of the incubator should be smooth, as rough turning can be associated with an increase in early embryonic mortality.

Obviously, mechanical turning as well as hand turning of eggs can potentially be too rough, resulting in an increase in embryonic mortality. Careful evaluation of the turning processes of an incubation system is strongly advised for this reason.

Weight loss calculations:

Egg weight losses can be calculated using the following formula:

1. Calculate the grams lost per day of incubation.

Starting weight - current weight
________________________

Days incubated

Example: 
26.00 gm - 24.05 gm         1.95 gm
                  ________________     =  ______  = 0.14 gm / day
                  
	               14 days                       14 days


2. Calculate anticipated weight loss for the total incubation period.

Grams lost / day X 28 days incubation period

Example:
 0.14 gm / day X 28 days incubation period = 3.9 gm


3. Calculate anticipated weight loss as a percentage of the original weight.

Anticipated weight loss

__________________ X 100

Starting weight

                  
Example: 
	      3.9 gm                           
	      ______    X 100 = 15%
                                                            
	     26.00 gm 

Most avian species eggs lose in the range of 15% (13-16%) of their original weight during the incubation process. This weight loss is regular and consistent throughout the entire period, and as a result, these calculations allow for predictability of the ultimate percentage loss to be anticipated. This linear weight loss relationship is a grossly underutilized monitoring tool in psittacine egg artificial incubation at present time, and as a result, allowing for weight loss deficits to not to be easily recognized or prevented.

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