Typically, papers on single-stage incubation focus on the benefits of all-in-all-out incubator management from the points of hatchability (number of chicks) and uniformity (chick quality). Much less is written about the positive impact of single-stage incubation management on hatchery hygiene. Yet when food safety is such a pivotal issue for the modern hatchery, from tracking and tracing to physical hygiene and biosecurity measures, this is a major benefit that should not be overlooked.
Hastings’ invention of the forced-draught incubator in 1911 was a great step forward in the technology of large scale incubators. Cooling in these early, forced-draught machines was mainly based on air cooling to prevent the eggs from overheating, and very little on water cooling. The air temperature was controlled at a fixed set point, by balancing the heat produced by older stage embryos with the heat-absorption demands of the younger embryos: so-called multi-stage incubation.
That innovation has been with us for almost 100 years. And despite an explosion in the physical scale of commercial hatcheries, and massive advancements in climate control technology – simplicity of incubator management, slow replacement rates for hatchery equipment and low labour costs in many countries mean that multi-stage incubation is still favoured by many hatcheries today.
The simplicity of multi-stage management stems from the fact that new, unincubated eggs are placed alternately with eggs containing older, heat producing embryos.
New eggs are placed regularly, once or twice a week. In the multi-stage system, the climate is controlled by the eggs.
Conversely, single-stage incubation is based on climate control technology, geared specifically to meeting the demands of the growing embryo. The incubator climate controller provides the embryo with heat and cooling as required. Set points of temperature, relative humidity and ventilation are adjusted, according to embryonic age. Eggs are placed in empty, disinfected incubators.
Single-stage hatchery management may also be based on the daily routine. Single-stage incubation programmes, once set-up for different eggs types, can be applied routinely.
Hygiene and food safety
The climate in a multi-stage incubator is controlled by levels of heat production in ‘older’ eggs, which heats the freshly placed eggs by air transfer. However, ‘older’ eggs are not only a source of heat. They are also a source of micro-organisms, for example bacteria or fungi, which can contaminate the ‘younger’ eggs. Add to this the risk of exploding or gaseous eggs, and contamination early in life may have lasting implications, leading to contaminated broilers with decreased performance, higher mortality – and ultimately contaminated meat products.
Thus, from a hygiene and food safety point of view, the multi-stage incubator becomes a source of contamination, which may lead to economic losses at hatchery level due to lower hatching rates and chick mortality.
The whole production chain is controlled by strict legislation for chain management (tracking and tracing) and hygiene. The integration of a single-stage hatchery in such poultry production systems is a simple task, because the principle of all-in-all-out makes the tracking and tracing of different batches of eggs easy.
To fill the multi-stage incubator, a batch of eggs from one supplier must often be separated into smaller batches and placed in different setters. This complicates tracking and tracing, making errors more likely to arise.
And the multi-stage incubator is never completely empty making thorough disinfection almost impossible. Single-stage incubation, however, allows for the machines to be thoroughly cleaned and disinfected every 18 days (between batches of eggs).
To enhance food safety at hatchery level in the production chain, the single-stage incubation process delivers benefits not available through multi-stage incubation by:
- Preventing cross-contamination from older to younger egg batches, because eggs of different ages need not be mixed.
- Facilitating the simple identification, tracking and tracing of each hatch.
- Enabling thorough cleaning and disinfection between hatch cycles.