Hatchability and early chick growth potential of broiler breeder eggs with hairline cracks

Eggs with hairline cracks are often placed in incubators, as they can appear structurally sound and, hence, capable of producing a saleable chick. The relative incubation weight loss, embryonic mortality, hatchability, and early chick growth rates associated with normally shelled broiler eggs and those with hairline cracks under practical conditions are not known. To determine the incidence of hairline cracks, eggs from 5 commercial flocks of various strains were candied, and equal numbers of hairline-cracked and normal eggs were collected and incubated for 21 d. All eggs were weighed and candied at 18 d, and any nonviable eggs were removed. All unhatched eggs remaining after 21 d of incubation were broken open to assess the stage of embryonic development. Transfer weights, hatchability, and chick hatch weights were lower (P < 0.05) in hairline-cracked as compared with normal eggs, whereas the percentage of weight loss was higher in hairline-cracked eggs. Hatchability was 74.37% for normal eggs as compared with 50.52% for hairline-cracked eggs. The incidence of mid (8 to 14 d of incubation) and late (over and including 15 d of incubation) embryonic mortality was higher in hairline-cracked eggs as compared with normal eggs. Significantly more hairline-cracked eggs were contaminated, broken, or both during incubation as compared with normal eggs. An increase in chick mortality was associated with hairline-cracked eggs compared with the normal eggs during the 14-d chick growth trial. Hairline cracks reduced hatchability of hatching eggs, increased the likelihood of contamination in the incubator due to putrefaction, and resulted in greater chick mortality. For these reasons, hairline-cracked eggs should not be incubated.