Effect of Long-Term Selection for Non-Destructive Deformation on Egg Shape in White Leghorns

Abstract

Several conventional traits, including eggshell thickness, are commonly being improved genetically as a means to increase eggshell strength. At the same time, researchers have come to recognize that factors related to egg geometry, such as egg shape, are important determinants of the variability remaining in eggshell strength, after conventional traits have been considered. Therefore, given that the value of the egg shape index -the egg's width to length ratiodepends highly on the hen strain, it is necessary to examine the relationship between eggshell strength and shape index more closely in a variety of breeds. From this perspective, by using REML methodology under a five-trait animal model, we analyzed a two-way selection experiment for non-destructive eggshell deformation in 31 generations of White Leghorns, to evaluate the effect of selection for eggshell strength on egg shape. In the strong line, which refers to the line that was selected for decreased non-destructive deformation value, the genetic correlation between eggshell breaking strength and shape index was 0.285±0.055, whereas that between non-destructive deformation and shape index was −0.021±0.063. In the weak line, these values were 0.244±0.055 and −0.093±0.060, respectively. The heritability estimates were 0.381±0.033 for non-destructive deformation, 0.349±0.029 for eggshell breaking strength, and 0.544±0.027 for shape index in the strong line, and 0.408±0.031, 0.468±0.032, and 0.484±0.028, respectively, in the weak line. The genetic correlation between eggshell breaking strength and shape index suggests that rounder eggs are somewhat more resistant to breakage than more elongated eggs. The moderately high heritability estimates for shape index indicate the potential to improve egg shape through genetic gain.

Akkermansia muciniphila Promotes Bone Development and Improves Eggshell Quality during the Sexual Maturity Period of Laying Hens by Increasing Osteogenesis

“…Therefore, we assessed egg quality at 20 weeks to investigate the relationship between bone physiology and eggshell quality. It has been reported that the egg shape index exhibited a positive correlation with the eggshell strength [65,66]. Our findings reveal that eggs in the Akk group exhibited improved egg shape index and eggshell strength.…”

Yacon (Smallanthus sonchifolius) root extracts affect laying performance, egg quality, serum biochemical parameters and intestinal microbiota in hens

“…supplementation had no significant effects on egg surface area, but improved the egg shape index [8]. It was reported that there was correlation between shape index and eggshell breaking strength, indicating the rounder chicken eggs arebeing somewhat more resistant to breakage than more elongated eggs [20]. However, quail eggs with a shape index >78% had the highest hatchability rate than those rounder eggs [21].…”