The influence of strain and age on some egg quality parameters of commercial laying hens

The experiment was conducted to evaluate the influence of strain and age on some egg quality parameters (egg weight and egg shell strength) of commercial laying hens. Layers of lines ISA Brown and DeKalb White were examined in period of nine months. Both lines were at same age (28 weeks) and were confined in common facility in battery cages. Laying hens were reared and fed according to standard breeding technology. Once a month 25 eggs of each line were taken to be examined for eggshell strength and egg weight, or in other words, total 450 table eggs were tested. Analises were done in Laboratory for testing egg quality by gaudges Egg Multi Tester EMT 5200 and Egg shell Gauge (Robotmation Co. Ltd., Tokyo, Japan) which have computerised equipment to examine quality and physical characteristics of eggs. Statistic analyses on results were done by computer sub-programme ANOVA and Fisher's LSD test to determine the level of statistical significant difference between examined factors. Egg weight was under significant impact of age (P ? 0,05), but not under the influence of strain, although eggs of ISA Brown line were insignificantly heavier than eggs of DeKalb White line. Eggs were heaviest at layers with older age, while they were lightest at younger birds. The results have shown significant differences (P ? 0,05) in eggshell strength compared to line influence (genotype) and months of age. Eggs from ISA Brown laying hens had much better and eggshell strength than those eggs from DeKalb White. Correlations between eggshell strength and egg weight were with significant (R < 0,05) negative value, which indicating that with increasing egg weight decreases of eggshell strength.