Research Article Open Access

Phenotypic Correlation between Egg Quality Indices in 85- Weeks-Old Layer Chicken Genotypes

Abstract

Phenotypic correlations between egg quality indices were evaluated in aged Shaver Brown (SB) and Nigerian 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 (YR, AR and SR) and indexes (YI, AI and SI); Y/A ratio and Haugh Unit (HU); Shell Thickness (ST), Volume (SV), and Density (SD). Pearson’s correlation method was employed for the analysis and none zero coefficients were interpreted as perfect (0.95-1.00), near perfect (0.94-0.85), very strong (0.84-0.75), strong (0.74-0.65), moderate (0.64-0.45), weak (0.44-0.25), or very weak (0.24-0.10). EW correlated perfectly with ESA, EV, ESG and SV in both genotypes; moderately with SW, SR, YW and AW in HEN eggs but near perfectly with AW, strongly with SR, and moderately with ST, SI, YW, AH and AI in SB. YW correlated moderately with HU, SV and SR, and weakly with AW, AH, AD, AI, SD, and SI in HEN eggs while in SB eggs, it had moderate correlations with HU, and weak correlations with AW, SV, SR, and SI. AW was moderately correlated with SV and weakly correlated with Y/A ratio, SW, and SR in HEN eggs but near perfectly with SV, strongly with SR, and moderately with ST and SI in SB eggs. Genotypic differences in strength and/or direction of correlation between egg quality traits could be due to differences in degree and direction of genetic selection for egg traits between genotypes. Therefore, phenotypic correlation could guide non-invasive determination and genetic improvement of egg quality traits in domestic chickens.

Cosmas Chikezie Ogbu*

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