What is the ‘Hatch Window?’ The term hatch window – also known as the spread of hatch – is used to describe the time span between the hatching of the first and last chick after the eggs have been transferred from the setter to the hatcher. Ideally, no more than 25 percent of chicks should hatch at 23 hours before pull and 75 percent of chicks should hatch approximately 13 hours before pull. If the eggs are hatching too early, the chicks become susceptible to problems such as dehydration. Dehydration to chicks this early could lead to increased 7- and 14-day mortality and/or poor broiler performance. If the chicks are hatching too late, the result could be poor hatchability, chick quality problems, increased pipped eggs and live embryo unhatched eggs. Factors Affecting Hatch Window Whether chicks hatch early or late, there are many factors that impact the hatch window, and subsequently, the overall health of chicks. Factors affecting early hatch include: Extended pre-heating periods Setting eggs too early. Too many hours of incubation Incorrect setter/hatcher temperature and humidity Hot spots inside the setter and hatcher Incorrect ventilation Seasonal temperature changes effecting the hatchery environment Too many fertile eggs in the hatcher Egg size Factors affecting late or delayed hatching include: Setting eggs too late Incorrect setter/hatcher temperature and humidity Incorrect ventilation Seasonal temperature changes effecting the hatchery environment Eggs which have been stored for long periods Eggs which have stored at too low a temperature Incorrect setting patterns in multi-stages machines Disease and fertility problems Although we know a lot about embryo development, incubation is still somewhat of a mystery. Closely monitoring the hatch window is a good indication of what is happening during setting or if any changes need to occur to maximize hatchability. It is the hatchery manager’s responsibility to know the condition of the chicks at pull as well as the seven-day customer and/or company mortality. This data helps him or her maintain optimal conditions during incubation and establish proper ventilation. For more advice on ventilation during incubation, watch this video from Hatchery Specialist and member of Cobb’s World Technical Support team – Steve Tweed.