Genetic analysis for dynamic changes of egg weight in 2 chicken lines

Abstract

One of the main concerns for poultry producers is how to maintain egg uniformity and stability in size and weight following the rapid growth during the early laying period. In this study, we aimed to investigate the increase in egg weight with advancing hen age, and to estimate genetic parameters of these increment traits in 2 pure lines of chickens (i.e., 2,010 White Leghorn and 1,200 brown-egg dwarf hens), using the restricted maximum likelihood method with the DMU procedure. We collected age at first egg (AFE), first egg weight (FEW) and kept records of egg weight per 10 wk from 30 to 60 wk of age. Meanwhile, the increments of egg weight were calculated for the evaluation of age-dependent dynamic changes. The increment of egg weight gained dramatically before 30 wk of age and became slower with the advance of age. Heritability estimates of AFE were larger than 0.32, and the low to moderate genetic correlations between AFE and FEW were observed in the 2 lines. The FEW showed high variation level compared with egg weights at later ages in the 2 lines, and had moderate heritability estimates in White Leghorns (0.20) and dwarf hens (0.33). Egg weights at different ages were highly heritable in the 2 lines (h(2) ≥ 0.35), and had strong genetic and phenotypic correlations among different ages. The estimates of heritability for most increment traits were low to moderate, especially those increments for 10-wk intervals ranging from 0.00 to 0.14. The genetic correlations among 3 consecutive egg weight increments for 10-wk intervals were low to moderate. Our results in the 2 lines should provide important insights into the genetic architecture of increment traits and offer some suggestions for producing uniform and stable eggs in response to advancing age.

Genome-wide association study dissects genetic architecture underlying longitudinal egg weights in chickens

“…The results were also supported by the fact that the four independent SNPs exerted consistent effects on all egg weights. In poultry industry, maintaining good stability without significant increase after laying peak is another great concern [ 3 , 4 ]. We previously conducted a genetic analysis for the increment traits of egg weight with advancing hen age [ 4 ], in which the increment of EW was defined as the difference between two EWs at neighboring ages.…”

“…In poultry industry, maintaining good stability without significant increase after laying peak is another great concern [ 3 , 4 ]. We previously conducted a genetic analysis for the increment traits of egg weight with advancing hen age [ 4 ], in which the increment of EW was defined as the difference between two EWs at neighboring ages. The low heritability estimates reflect that EWs at different ages may share similar genetic causes, and calculating the difference values may eliminate the same additive effects between them.…”

“…In poultry industry, egg weight has always been an economically important trait, and is usually regarded as the major breeding objective and research goal [ 1 – 4 ]. As a sensory feature at first glance, egg weight demonstrates a critical impact on consumption due to diverse preferences towards size worldwide [ 5 , 6 ].…”

“…Multiple lines of evidence have suggested that egg weights are mainly determined by genetic factors and they all show considerable heritability estimates [ 4 , 10 , 11 ]. Currently, 77 quantitative trait loci (QTL) involved in egg weight, located on 17 different chromosomes, have been deposited in the AnimalQTLdb ( http://www.animalgenome.org/cgi-bin/QTLdb/index ).…”

Functional and whole regression-based genome-wide association analyses for weight measurements of chicken eggs

“…EWs have been considered among the important selection targets for both customers and producers, especially during certain laying periods [26,29]. In this study, Table 3.…”