Evaluation of different egg quality traits and interpretation of their mode of inheritance in White Leghorns

Abstract

Aim:The experiment was carried out to evaluate different external and internal egg quality traits and to figure out their mode of inheritance from a set of hierarchically classified data.Materials and Methods:The data collected from 548 progenies (1 egg from each progeny) of 282 dams mated to 47 sires (1 sire mated to 6 dams) of a White Leghorn flock were used in the present study. Phenotypic means and their standard errors were calculated for all the quality traits. Heritabilities were estimated for these traits separately from “sire,” “dam” and “sire+dam” (full-sib) components of variance using Statistical Package for Social Sciences-17 program.Results:External quality traits such as; egg weight, length, width, shape index, surface area, shell weight, shell thickness, shell ratio, and internal quality traits such as; length, width, height, and weight of albumen and yolk, albumen index, albumen ratio, Haugh unit (H.U.), yolk diameter, yolk index, yolk ratio, and yolk albumen ratio were measured in 548 eggs of the experimental White Leghorn flock. The eggs were found to have optimum weight (57.78±0.20 g), shape index (73.53±0.18) and shell characteristics (6 g, 0.32 mm) as per its genetic potential. Higher values for albumen height (8.41±0.04) mm and H.U. (92.00±0.19) are attributable to the freshness of eggs and proper age of hens. Heritability estimates from “sire” component of variance were higher than “dam” and “sire+dam” components for the traits like egg weight, length, width, shape index, surface area, albumen width, albumen index, H.U., yolk width, yolk height, yolk weight, and yolk index whereas for rest of the traits the values estimated from “dam” component were higher. Estimates from “sire+dam” component were intermediate to the estimates derived from “sire” and “dam” components.Conclusion:The heritability estimates from different egg quality traits were moderate to high. Since most of the traits have high heritability values, these traits can be improved by mass selection.

Heritability estimates of egg weight and egg shell weight in Ikenne, Nigeria

“…The mean egg weight registered 55.02g at 25 weeks, 62.20g at 51 weeks and 63.29g at 72 weeks with a corresponding mean value of 60.17g for the overall ages of the hen depicting an increasing trend. These reports are similar to 57.78g registered by Rath et al [7] for egg weight at 50 weeks employing white leghorns; 48.1-63.9g reported for single Comb and white leghorn at 25 -65 weeks of age obtained by Chen et al [18]. Sreenivas et al [11] recorded 50.01 -53.89g for three pure lines and one control lines of white leghorns at 40 weeks.…”

“…Minelli et al [23] reported 6.00g at 28 -32 weeks, 6.16g at 47 -50 weeks and 6.29g at 70 -73 weeks of age. Rath et al [7] 6.00g at 50 weeks recorded for white leghorns. Tumova et al [33] obtained 6.91 -7.81g at 28 -60 weeks of age in New Black breed; and 6.50 -6.91g for litter raised Hisex Brown at 60 weeks.…”

“…These estimates generally agreed with the report in literature. Rath et al [7] obtained values of 0.443±0.160 and 0.223±0257 for heritability estimates of egg weight and egg shell weight respectively at 50 weeks of age for white leghorns using half-sib correlation analysis adopted to multifarious species and evaluated using PROC VARCOMP of restricted maximum likelihood (REML) method of statistical package for social science (SPSS). Begli et al [10] registered 0.45±0.09 and 0.23±0.08 for heritability estimates of egg weight and egg shell weight respectively at 30 weeks using half-sib correlation analysis adopted to multifarious species and employed restricted maximum likelihood of ASREML software for the estimation of variance component.…”

“…However, low estimates of 0.1277±0.0091 and 0.0004 0.065 were registered for egg weight and egg shell weight respectively when the age variance was excluded from the computation. This variation could be attributed to the removal of age variance which determines its developmental processes and hence robust the nonadditive gene actions thereby culminating into low, and more accurate estimates of heritability of the traits compared to the report of other genetic researchers [6][7][8][9]. Exception of the values of 0.180±0.122 and 0.161±0.079 obtained for egg weight and egg shell weight for IWI strain of white leghorns using full sib correlation method of mixed model least squares and maximum likelihood (LSMLML) computer software at 40 weeks by Sreenivas et al [11].…”

“…Heritability estimates are usually categorized into three classes viz: low (0 -0.19), moderate (0.2 -0.39) and high (0.4 and above) with its values in all classes ranging from 0 -1 or 0 -100%. Literature estimates cited in this paper are within the range of low to high [6][7][8][9][10][11]. Therefore, the aim of this research was to determine the heritability estimates in order to assess the inheritance pattern of various egg quality traits under the influence of age variance in Bovan Nera Black laying chickens.…”