To produce the best chicks, eggs must be kept at a very precise temperature, humidity and ventilation during incubation. However, it is often difficult to know what’s happening beneath the surface of each shell. Drawing on years of experience and practical know-how, Cobb experts rely on key measurements that help identify the right environment to ensure chicks are strong and healthy when they hatch. Uniformity of Embryo Temperatures Embryo temperatures can be accurately estimated by scanning eggshells at their equator. Using a thermoscan thermometer, test fertile eggs between 15 and 16 days of incubation. Embryo temperatures are directly related to hatchability, as anything too cold or too warm can impact hatch times and chick welfare while in the hatcher trays. Hatch Window The hatch window – which is the time between when the first and last chick hatch – should be roughly 30 hours. Ideally, no more than 25 percent of chicks should be hatched 23 hours before chicks are pulled (removed from the hatcher). 70-80 percent of chicks should hatch approximately 12 hours before pull. Check chicks’ temperatures before pulling, targeting an internal temperature of 104°F. If the eggs hatch too early, chicks become susceptible to problems such as overheating and dehydration, which could impact seven- and 14-day mortality rates and overall performance. If the chicks are hatching too late, the result could be poor hatchability, poor chick quality and live embryo unhatched eggs. Factors affecting hatch include: Pre-heating eggs for too long before setting. Incorrect temperature, humidity and ventilation. Hot spots inside the setter and hatcher. Seasonal temperature changes effecting the hatchery environment. Too many fertile eggs in the hatcher. Incorrect setting patterns in multi-stage machines. Egg storage time and temperature. Cleanliness of eggshells Excess meconium (waste) residue on eggshells is a good indication that chicks have either hatched too early or stayed in the hatcher trays too long. Leaving chicks in the hatcher too long is the difference between great and good mortality. In addition to incubation environment, several other factors also impact chicks’ overall health and performance, such as transportation, brooding, feed and water management and more. Download our Hatchery Management guide or visit the Cobb Academy for additional resources.