Whole egg quality trait phenotypic correlations in aged layer chicken genotypes

Phenotypic correlations between egg weight (EW) and length (EL), diameter (ED), surface area (ESA), volume (EV), specific gravity (ESG), and shape index (ESI) were evaluated in Shaver Brown (SB), and Nigerian heavy ecotype (HE) hens using Pearson’s correlation method. None zero coefficients were interpreted as perfect, near perfect, very strong, strong, moderate, weak, or very weak. The EW, EL, ED, ESA, EV, and ESG differed significantly between genotypes (p < 0.000). Eggs from SB had higher values for these traits except ESG which was higher in HE eggs. Egg weight perfectly correlated with ESA, EV, and ESG, and very weakly with ESI in both genotypes; moderately with EL in HE but strongly with this trait in SB; perfectly with ED in HE, but very weakly with this variable in SB. Egg length had moderate positive correlations with ED, ESA and EV, moderate negative correlation with ESG, and a strong negative correlation with ESI in HE but very weak positive correlation with ED, strong correlations with ESA (r = - 0.718), EV (r = 0.706), and ESG (r = - 0.718), and weak negative correlation with ESI (r = - 0.267) in SB. Egg diameter was perfectly correlated with ESA, EV, and ESG in HE but, very weakly with these traits in SB. The observed variations in direction or strength of correlation between genotypes suggest significant genetic effects. Phenotypic correlation could hence be used to understand egg quality trait interrelationships in different layer chicken breeds, and guide non-destructive determination, and genetic improvement of whole egg quality traits.