EMBRYONIC MORTALITY IN LAYING STRAINS RIR AND BPR DURING INCUBATION

Fertility of hatching eggs, hatchability and embryonic mortality were investigated in three original strains (RIR, BPR-1 and BPR-2) during p edigree hatching in five periods - by the 3rd, 7th, 14th, 20th day and at the stage of breaking through the eggshell. Average hatchability o f all three strains was 76.6%, the share of ''clear'' eggs made 13.3% and embryonic mortality amounted to 10.1%. The peaks of embryonic mort ality of all three strains were recorded in two periods - on the seven th day and at the end of incubation. It was on average 18.4% out of th e total embryonic mortality on the seventh day of incubation, 33.4% on the twentieth day of incubation and 37.1% at the moment of breaking t hrough the eggshell. With respect to between-the-strains differentiati on, the highest embryonic mortality was observed in the two strains wi th higher coefficients of inbreeding BPR-2 (12.8%) and RIR (12.6%) tha n in strain BPR-I (4.7%). There was not however any marked difference between the strains in the distribution of dead embryos in the course of incubation. The embryonic mortality of all three strains is typical of inbredized strains by its pattern (increase at the moment of break ing through the eggshell).