Cooling periods enhance specific pathogen free (SPF) poultry egg hatchability

Poultry vaccine research is being conducted at a Cal Poly Pomona biosafety level 2 (BSL-2) facility. A central component of that research is the successful incubation and hatching of specific pathogen free (SPF) eggs. In an attempt to improve the percentage of SPF poultry eggs that hatched during incubation (hatchability), a simulated natural nesting cooling period was implemented once daily in two of four incubation groups. 159 SPF chicken eggs were acquired by a commercial supplier. Two incubation groups (n = 80) were maintained at a constant temperature of 37.5 °C. Two other incubation groups (n = 79) experienced a once daily 60 minute decrease in temperature (21.1°C), simulating the cooling an egg may experience when a hen leaves the nest. Eggs were incubated in a cabinet incubator within the BSL-2 facility, and all other incubation parameters were controlled (humidity, temperature, turning interval etc.). Candling to evaluate egg development occurred after the 1st and before the 3rd week of incubation. Heart rate was evaluated non-invasively before the 3rd week of incubation. The incubation groups without a cooling period had a hatchability rate of 82.5% and 90%, while the hatchability of the two groups with the cooling period were 94.9% and 100% respectively. In the absence of other unknown factors, this evidence suggests that including a daily 60 minute cooling period during incubation increases SPF poultry egg hatchability rates.