Phenotypic correlation between egg quality indices in 85-weeks-old layer chicken genotypes

Abstract

Abstract Phenotypic correlations between egg quality indices were evaluated in aged Shaver Brown (SB) and heavy ecotype native (HEN) hens. Studied traits were egg, yolk, albumen and shell weights (EW, YW, AW and SW); egg length (EL), surface area (ESA), volume (EV), specific gravity (ESG) and shape index (ESI); egg, yolk and albumen diameters (ED, YD and AD); yolk and albumen heights (YH and AH); yolk, albumen and shell ratios and indexes (YR, AR and SR) and (YI, AI and SI); Y/A and Haugh unit (HU); shell thickness (ST), volume (SV), and density (SD). Pearson’s correlation method was employed and none zero coefficients were interpreted as perfect, near perfect, very strong, strong, moderate, weak, or very weak. EW perfectly correlated with ESA, EV, ESG and SV, and very weakly with ESI and SD in both genotypes; moderately with EL, SW, SR, YW and AW, and weakly with SD, YD and AH in HEN eggs but near perfectly with AW, strongly with EL and SR, moderately with ST, SI, YW, AH and AI, and weakly with YH and AR in SB. YW very strongly correlated with YR, strongly with YD and Y/A, moderately with YI, HU, SV and SR, and weakly with YH, AW, AH, AD, AI, SD, and SI in HEN eggs while in SB eggs it had very strong correlations with YR and Y/A, moderate correlations with YD and HU, and weak correlations with AW, SV, SR, and SI. AW was strongly correlated with AR, moderately with SV, and weakly with Y/A, SW, and SR in HEN eggs but near perfectly with SV, strongly with SR, and moderately with AH, ST, and SI in SB eggs. In HEN eggs, SW had very strong correlation with SI, moderate correlations with SV, SD, and SR and weak correlation with ST but very strongly correlated with SD, strongly with SI, and moderately with SR in SB. Variations in direction and/or strength of correlation suggest genotypic effects due to differences in degree and direction of genetic selection. Therefore, phenotypic correlation could guide non-invasive determination and genetic improvement of egg quality traits in domestic chicken genotypes.