The process of embryonic mortality in seven initial laying strains during incubation

Abstract. In five segments of incubation (within the 4th day, on the 7th, 14th, 20th days and in the stage of breaking through the shell) we studied the fertility of hatching eggs, the hatchability and embryonic mortality of seven initial laying strains (RIR – 1, RIR – 2, RIR – 3, RIW – 1, SU – 1, BPR – 1 and BPR – 2) in the course of three egg sets of individual pedigree hatching. The average hatchability of all the seven strains was 71.5%, the proportion of unfertilised eggs was 11.3% and embryonic mortality reached 17.2%. The embryonic mortality of all the seven strains culminated in two periods, i.e. within the 4th day of incubation (36.9% of the total embryonic mortality) and at the end of incubation (from the 15th to 20th day of incubation – 23.4% and during breaking through the shell – 18.1%). In terms of the inter-line differences, the embryonic mortality was the highest in three lines, which had a higher coefficient of inbreeding (Fx < 12.5%), i.e. RIR – 1 (20.9%), BPR – 2 (20.3%) and RIW – 1 (23.7%). All the three lines bear the recessive gene (k⁺) on locus K, which is responsible for the rapid type of feathering using feathersexing. Within the 7th day of incubation the embryonic mortality was higher in both BPR lines (BPR – 1–58.1%, BPR – 2–53.6% of the total embryonic mortality), while in the last trimester of incubation and in the period of breaking through the shell it was the lowest (BPR – 1–30.8%, BPR – 2–36.2% of the total embryonic mortality).