Defective eggs and their relationship to egg yield, egg and body weight in hens of five original laying lines

We investigated 3 985 individually housed hens of five original laying lines of two breeds RIR and BPR. The proportion of abnormal eggs out of the eggs laid before the age of 240 days ranged between 7.0% and 9.7%, in dependence on the line. The average number of cracked eggs ranged between 2.5% and 4.4%, double-yolk eggs between 2.2% and 3.0% and shell-less eggs between 2.0% and 2.7%. The correlation between the number of eggs laid at the beginning of the laying period and during the period of observation, and the frequency of double-yolk eggs was positive (rP = 0.00 to rP = 0.21) and mostly statistically highly significant (P < 0.01). On the other hand, statistically highly significant negative correlations (P < 0.01) were found between the number of eggs laid during the period of observation and the frequency of cracked eggs, where the correlations in the individual lines ranged between rP = -0.04 and rP = -0.23. Positive correlations, mostly statistically highly significant (P < 0.01), were found between the number of eggs laid during the period of observation and the frequency of shell-less eggs (rP = 0.00 to rP = 0.15). With the increasing weight of eggs the frequency of abnormal eggs also increased, in particular of double-yolk eggs (rP = 0.08 to rp= 0.32), for the most part statistically highly significantly (P < 0.01). The correlations between the individual types of abnormal eggs were positive. Statistically highly significant correlations (P < 0.01) were discovered between the frequency of double-yolk eggs and cracked eggs (rP = -0.02 to rp= 0.22) on the one hand and, between double-yolk eggs and shell-less eggs (rP = 0.16 to rP = 0.24) on the other.