The effect on hatchability of time post-oviposition until initiation of cool storage was examined using 2,742 eggs from 31-week-old Ross hens. Treatments were defined by the length of time that eggs remained at breeder house temperature, prior to cool storage. In treatments A, B and C, respectively, eggs were taken to the cooling room immediately after collection, after 5 hours in the aviary or after 10 hours in the aviary. From each treatment, 860 eggs were distributed into 10 replicates of 86 eggs each and stored for 4 days at 18.2 - 21.0ºC and 75% humidity. After cool storage, they were incubated. Embryo mortality in treatment A was higher than in B (P<0.05). The hatchability of eggs of treatment B was higher (P<0.05) than that of treatment A. Average chick weight at hatching was higher for treatment A than for treatment C (P<0.05). Eggs that were cooled beginning five hours after oviposition produced the highest incubation yield.
broiler breeder; egg; hatchability; embryo mortality; cool storage
