Effects of turkey breeder hen age, strain, and length of the incubation period on survival of embryos and hatchlings

Embryonic growth relationships exist for egg weight, eggshell conductance, and length of the incubation period. These relationships have been well est ablished for comparisons of embryonic development across species; however, very little is known about these relationships within a species. The hypoth esis was tested that survival of embryos in turkey eggs could be changed by manipulating incubation periods. Fertile eggs were obtained three times fr om the same breeder flocks (two strains). Two incubator temperature treatments were used to create two different incu bation periods for the eggs. Eggs produced at 33 weeks of age hatched bette r at shorter incubation periods, eggs produced at 43 weeks of age hatched e qually well at both incubation temperatures, and eggs produced at 54 weeks of age hatched better at longer incubation periods. Livability for 5 days i n brooder houses was highly variable but indicated survival differences bet ween strains. Additionally, longer incubation periods produced poults that lived better than did controls. The results suggest that the conductance co nstant principle, which describes the relationship among egg weight, length of incubation, and eggshell conductance, can be used in commercial hatcher ies to improve embryo survival and poult quality.