Hatchability of Chicken Embryos Exposed to Acute High Temperature Stress at Various Ages

Abstract

Two experiments were conducted in which chicken embryos of various ages were subjected to acute high temperature stress to determine the effect on embryonic mortality and hatchability. Embryos were incubated at a temperature of 37.5 C (control) until they were 3, 7, 11, 16, or 19 days of age. Embryos of each age were separated into five groups and exposed to an incubation stress temperature of 43.3 C for various lengths of time. After exposure, the embryos were placed back into control incubators until hatching.Exposing 3-day-old embryos for 12 hr to a temperature of 43.3 C decreased hatchabiltiy of fertile eggs to approximately 50% of controls. A similar decrease occurred with 7-day-old embryos after only 4 hr of heat stress and with the 11 and 16-day-old embryos after 7 hr of stress. More than 50% reduction in hatchability occurred after 5 hr of heat stress with 19-day-old embryos. These results indicated that 3-day-old embryos are more resistant to heat stress and 7-day-old embryos less resistant to heat stress than previously indicated in the literature. Chicks that hatched following severe heat stress had wiry down, were usually weak and/or inactive, and often were unable to stand.