ABSTRACT
Uncharacteristically large spreading area on a flat surface of broken egg negatively affects egg quality assessment and reduces eggs' economic value. In this study, we investigated the heredity of the egg content spreading area as well as the relationships between the egg content spreading area and egg quality traits and properties. We measured the total egg content spreading area (TECA), outer thin albumen area (OTAA), inner thick albumen area (ITAA), yolk area (YA), and egg quality traits for 1414 newly laid eggs from 487 27-wk-old White Leghorn pure line pullets. The genetic parameters of egg content spreading areas were estimated. The phenotypic and genetic correlations between egg content spreading area and egg quality traits were analyzed. The differences in the properties of eggs with similar egg weight but markedly different TECA were also analyzed. The heritability estimates for TECA, OTAA, ITAA, and YA were low to moderate, with values of 0.214, 0.176, 0.340, and 0.280, respectively. Egg weight was related to TECA with a phenotypic correlation of 0.450 (P < 0.01) and a genetic correlation of 0.349. A high genetic correlation (-0.731) was found between TECA and Haugh unit. In eggs with larger TECA, the weight and total solid content of outer thin albumen (OTA) and moisture content of inner thick albumen (ITA) were significantly higher, whereas the weight and total solid content of ITA was markedly lower, but no differences (P > 0.05) were found in the pH of OTA and ITA, moisture content of OTA, as well as the eggshell strength, thickness, and non-destruction and fracture deformation between eggs with similar egg weight but markedly different TECA. These results suggest that the egg content spreading area can be regulated via the direct selection strategy or indirect selection of the ratio of OTA to ITA in the breeding program.
Subject(s)
Chickens/physiology , Eggs/analysis , Ovum/physiology , Animals , Chickens/genetics , HeredityABSTRACT
Eggshell damages lead to economic losses in the egg production industry and are a threat to human health. We examined 49-wk-old Rhode Island White hens (Gallus gallus) that laid eggs having shells with significantly different strengths and thicknesses. We used HiSeq 2000 (Illumina) sequencing to characterize the chicken transcriptome and whole genome to identify the key genes and genetic mutations associated with eggshell calcification. We identified a total of 14,234 genes expressed in the chicken uterus, representing 89% of all annotated chicken genes. A total of 889 differentially expressed genes were identified by comparing low eggshell strength (LES) and normal eggshell strength (NES) genomes. The DEGs are enriched in calcification-related processes, including calcium ion transport and calcium signaling pathways as revealed by gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis. Some important matrix proteins, such as OC-116, LTF and SPP1, were also expressed differentially between two groups. A total of 3,671,919 single-nucleotide polymorphisms (SNPs) and 508,035 Indels were detected in protein coding genes by whole-genome re-sequencing, including 1775 non-synonymous variations and 19 frame-shift Indels in DEGs. SNPs and Indels found in this study could be further investigated for eggshell traits. This is the first report to integrate the transcriptome and genome re-sequencing to target the genetic variations which decreased the eggshell qualities. These findings further advance our understanding of eggshell calcification in the chicken uterus.
