Comparison of physical quality and composition of eggs from historic strains of single comb white leghorn chickens

The effect of long-term genetic selection on physical quality and compositi on of eggs was determined by analyzing eggs acquired from Agriculture Canad a: Ottawa Control Strain 5 (CS5) from a 1950 base population, 7 (CS7) from a 1958 population and 10 (CS10) from a 1972 population. Eggs from the H&N " Nick Chick" current commercial strain (CCS) were also included. Eggs were c ollected monthly over a 62-wk laying period and analyzed for egg, albumen, shell and yolk weight; albumen protein, solids and pH; percentage yolk soli ds and fat; Haugh units; and specific gravity. Significant (P < 0.05) differences found between strains included a progres sive increase in weight of eggs from the CS5 to CCS. Although the eggs incr eased in size, no significant differences were found between strains for sp ecific gravity or percentage shell weight. Yolk weights of eggs from the st rains examined did not differ. However, the percentage of yolk found in cur rent strain eggs was significantly lower (P < 0.05), with a subsequent high er percentage albumen due to the increase in egg size of the CCS. Haugh uni ts were significantly higher in the CS10 and CCS strains than in the other strains. No significant differences between strains were seen in albumen pr otein, solids, pH, or yolk solids. Mean percentage yolk fat assay values fo r eggs from the CS5, CS7, CS10, and CCS strains were 33.08, 32.68, 32.84, a nd 32.40, respectively. Percentage yolk fat values obtained from CCS were s ignificantly lower (P < 0.05) than those obtained from the other strains. T he results from this study indicate that genetic selection has produced lar ger eggs containing a lower percentage of yolk white overall egg quality ha s been maintained or improved.