Cuticle deposition duration in the uterus is correlated with eggshell cuticle quality in White Leghorn laying hens

Abstract

The cuticle formed in the uterus is the outermost layer as the first defense line of eggshell against microbial invasions in most avian species, and analyzing its genetic regulation and influencing factors are of great importance to egg biosecurity in poultry production worldwide. The current study compared the uterine transcriptome and proteome of laying hens producing eggs with good and poor cuticle quality (GC and PC, the top and tail of the cuticle quality distribution), and identified several genes involved with eggshell cuticle quality (ESCQ). Overall, transcriptomic analysis identified 53 differentially expressed genes (DEGs) between PC versus GC group hens, among which 25 were up-regulated and 28 were down-regulated. No differences were found in the uterine proteome. Several DEGs, including PTGDS, PLCG2, ADM and PRLR related to uterine functions and reproductive hormones, were validated by qPCR analysis. Egg quality measurements between GC and PC hens showed GC hens had longer laying interval between two consecutive ovipositions (25.64 ± 1.23 vs 24.94 ± 1.12 h) and thicker eggshell thickness (352.01 ± 23.04 vs 316.20 ± 30.58 μm) (P < 0.05). Apart from eggshell traits, other egg quality traits didn't differ. The result demonstrated eggshell and cuticle deposition duration in the uterus is one of the major factors affecting ESCQ in laying hens. PTGDS, PLCG2, ADM and PRLR genes were discovered and might play crucial roles in cuticle deposition by regulating the uterine muscular activities and secretion function. The findings in the present study provide new insights into the genetic regulation of cuticle deposition in laying hens and establish a foundation for further investigations.

Figure 1

Heatmap of the DEGs between GC and PC hen uterus during cuticle deposition from the transcriptomic analysis. GC, good cuticle; PC, poor cuticle.

Figure 2

Validation of the DEGs of GC versus PC hen uterus during cuticle deposition from the transcriptomic analysis. The qPCR was performed to quantify the relative gene expression level based on the 2^−ΔΔCT method. For gene expression data normalization, GAPDH was used as a reference gene. Fold changes between the GC (good cuticle) and PC (poor cuticle) group were calculated for the genes ADM, PLCG2, PRLR and PTGDS. The Y axis shows the fold changes.

Figure 3

Laying interval of GC and PC group hens. The laying interval between two consecutive ovipositions was determined (at least 4 ovipositions per hen) for GC (n = 196, 60 hens with 302 ovipositions) and PC (n = 180, 60 hens with 280 ovipositions) group hens of Flock-B at 28-week old (GC 25.64 ± 1.23 vs PC 24.94 ± 1.12, h; P < 0.01).

Figure 4

Eggshell ultrastructure of GC and PC group eggs by scanning electron microscope (SEM) (× 200). A and B, eggshell ultrastructure without and with a gas pore, respectively.