Genetic parameters of egg quality traits on different pedigree layers with special focus on dynamic stiffness

Abstract

Egg quality traits are of utmost importance in layer breeding programs due to their effect on profitability in the egg production industry and on the production of quality chicks. Therefore, the aim of this study was to analyze and estimate genetic parameters of different quality traits: egg weight, breaking strength, dynamic stiffness (Kdyn), egg shape index, eggshell thickness, and albumen height. Eggs were obtained from 4 pure lines of birds. Two different tests were performed: a white breeding program, with eggs from a male and female line of a white egg layer program that were analyzed at 67 to 70 wk of age, and a brown breeding program, with eggs from a male and female line of a brown egg layer program that were analyzed at 32 to 36 wk of age. In general, heritabilities were moderate to high for all traits (h² = 0.23 to 0.71). A high genetic correlation was estimated in both tests between breaking strength and Kdyn (rg = +0.40 to +0.61). Shell thickness was also positively correlated with breaking strength (rg = +0.50 to +0.63) and Kdyn (rg = +0.28 to +0.69). These moderate relationships demonstrate that the strength of an egg not only relies on the shell thickness but also on the quality and uniformity of eggshell construction. Dynamic stiffness might be preferred for breeding purposes due to its lower negative genetic correlation with egg weight and its higher heritability (h² = 0.35 to 0.70) compared with breaking strength (h² = 0.23 to 0.35). Breaking strength and Kdyn were positively correlated with shape index, which confirms that round eggs will show higher shell stability. Therefore, it is necessary to monitor egg shape to maintain an optimal form.

Differences in oviposition and egg quality of various genotypes of laying hens

“…Rounder eggs were observed in the morning (P ≤ 0.001), and the measurement was also affected by the interaction between genotype and oviposition time (P ≤ 0.007), with the highest values for Bovans Brown at 12:00 h and the lowest for Bovans Sperwer at 9:00 h. This interaction may explain the contradictory results of the effect of oviposition time on egg shape index. Roland (1978) and Blanco et al (2014) observed rounder eggs in the afternoon, whereas Tumova and Ebeid (2005) observed rounder eggs in the morning. The egg shape index is associated with egg shell quality, as rounder eggs better maintain egg shell quality (Roland 1978).…”

“…Commercially available genotypes produce eggs of different weights, and the proportion of egg components varies as well (Johnston and Gous 2007;Tumova and Ledvinka 2009). Notwithstanding, differences among genotypes in albumen quality (Suk and Park 2001;Tumova et al 2011), yolk quality (Tumova et al 2011), and egg shell quality (Suk and Park 2001;Tumova et al 2011;Kaur et al 2013;Blanco et al 2014) have been observed.…”

Ovarian Morphology and Egg Quality Traits of Egyptian Selected Strain for Egg Production Compared with Commercial Laying Strains

“…Egg quality traits including egg weight (EW) , shell thickness (ST), and shell index (SI) are very important traits in layer breeding programs due to their effect on profitability in the egg production industry (Blanco et al, 2014). EW has great economic importance in poultry breeding and is considered among the major breeding objectives (Savegnago et al, 2011).…”

“…This is due to their effect on profitability in the egg production industry and on the production of quality chicks. The ST and SI are positively correlated with breaking strength (Blanco et al, 2014). Also, eggshell with lower quality than desired may lead to contamination of the important content (yolk and albumen), compromising the dietary health of consumers and determined the number of salable eggs output in the layer industry (Cordeiro et al, 2017).…”

“…Also, different genetic selection programs that were used in poultry breeding for almost a hundred years, led to positive effects in improving production performance in poultry (Buzała et al, 2015). Selection index, in layers breeding programs, that includes more than 30 closely related traits made it possible for balanced genetic improvements in different traits even when the traits are negatively correlated (Blanco et al, 2014). Productive performance, in layer breeds, can be assessed through parameters such as ovary morphology, during sexual maturation, at first oviposition, and at the end of lay Robinson et al, 2001).…”