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- Importance of temperature and egg position for contact incubation of eggs of the red-legged partridge (Alectoris rufa)

D. C. Deeming (1), C. Riches (2) & I. Pearce (3)

(1) Hatchery Consulting & Research, 9, Eagle Drive, Welton, Lincoln, LN2 3LP, United Kingdom;
(2) University of Lincoln, Riseholme Park, Lincoln, LN2 2LG, United Kingdom;
(3) Brinsea Products Ltd., Station Road, Sandford, Somerset, BS19 5RA, United Kingdom

Email: charlie@deemingdc.freeserve.co.uk

Abstract of a paper presented at Incubation and Fertility Research Group, 2004 Meeting at  University of  Lincoln, Lincoln, UK September 2004

The Contaq X8 incubator produced by Brinsea Products Ltd is an innovative approach to artificial incubation. In an attempt to mimic natural incubation in a nest, it relies on utilising heat exchange through contact between a plastic bubble full of air heated to the incubation temperature and the upper surface of the eggs in the machine. There is no other source of heat in the machine. Initial trials with prototypes of the design proved to be successful and popular with aviculturists and the Contaq X8 was launched as a commercial product in 2003. This machine is so different that it was not immediately obvious how it should be operated to the best advantage. In particular, would the principles applied with still-air incubation apply with contact incubation?

This first part of the study sought to investigate the appropriate temperature for the air in the bubble. The second part of this study sought to confirm that the temperature suggested in trial 1 as being suitable and also to study the effects of improving contact between the eggs and the bubble. The study used eggs of the red-legged partridge, rather than domestic fowl, because: 1) these birds produce sufficient numbers of eggs at any one time to run several incubators full of eggs in parallel; 2) at 20-g the partridge egg is comparable to eggs from more exotic species, such as parrots; and 3) although bred in captivity the red-legged partridge is relatively unselected and resembles a wild-type bird.

In trial 1, three Contaq X8 machines were used to incubated 100 partridge eggs each with the only difference being the temperature of the air within the bubble: 38.5ºC, 39.5ºC and 40.5ºC. Relative humidity was 55%RH. Eggs were set between plastic rollers and were turned (through 120º every hour) as a fabric mat moved under them. The control was a force-draught Octagon 100 machine (Brinsea Products Ltd) set at 37.5ºC that was used to hold 204 partridge eggs. Turning was every 30 minutes through 90º and humidity was controlled. In trial 2, two Contaq X8 machines, each holding 100 partridge eggs, were set at 40.5ºC and 55%RH. Here the eggs were set on the plastic rollers at 10 mm or 15 mm above the moving mat (which caused the rollers to move). Rubber “o”-rings threaded on to the rollers acted as spacers to prevent lateral movement during turning. An Octagon 100 machine set at 37.5ºC hold 102 partridge eggs acted as a control. For both trials, records were made of the following: upper surface shell temperature at various times during incubation (using an IR thermometer), the temperature and humidity on the display panel, weight loss of a sample of 30 eggs from each machine during incubation to 21 days, the numbers of chicks at intervals over the hatching period and the pattern of fertility and embryonic mortality.

In both trials, the temperature of the upper surface of the eggshell was ~3ºC lower than the bubble temperature. The control eggs had the shortest incubation period in both trials followed by eggs from contact incubators set at 40.5ºC and hatchabilities of these eggs were not significantly different from the control machines. In Trial 1, as bubble temperature decreased then the incubation was prolonged and hatchability was progressively lower. Eggs under a bubble temperature of 38.5ºC contained a large number of small, under-developed embryos that were alive upon opening the hatch debris but would never had hatched. Moreover, in the Contaq X8 machines setting eggs on the moving mat allowed “turning creep”, which meant that eggs moved from under the bubble leading to embryonic mortality early in incubation. In trial 2, raising the eggs (irrespective of height) nearer the bubble improved contact and hatchability was higher than the control. The rubber “o”-rings were effective at stopping “turning creep”.

Hence, hatchability equalled or exceeded that of the force-draught machine but only if the bubble temperature 40.5°C, which was ~3°C higher than conventional force-draught machines. Furthermore, this is ~1°C higher than the top of eggs in a still-air machine, i.e. 39.5°C. To maximise contact with the plastic bubble small eggs need to set on the rollers with “o”-ring spacers to prevent movement from under the bubble. It was concluded that contact incubation is an effective alternative to conventional artificial incubators used for small-scale incubation.

Thanks go to Mr Bernard Voce of Shelford Pheasantries, near Newark for supplying the eggs used in these studies.

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