Chemerin concentration in egg white in layer and broiler hens during the laying period for 2 successive generations

Abstract

The genetic selection progress in layers and broilers makes poultry production one of the fastest growing industries. Objectives of the breeding companies are the stability or the increase in the laying rate and the production of viable chicks. New biomarkers are necessary to improve reproductive and egg performances. Chemerin (Chem) produced by oviduct accumulates in egg white (EW). Here, we hypothesized that EW Chem concentration was dependent on the stage of laying and on the breed (layer vs. broiler). In addition, they could be associated to laying performance and fertility parameters. In breeding companies, we collected during 2 successive generations (G0 (mother) and G1 (daughter)) eggs from 100 layers and 100 broilers hens during 5 d at 3 stages: before, after laying peak and at the end of laying period. For each egg, the EW was sampled to measure Chem concentration by ELISA assay. In each generation at the end of laying period, magnums from oviduct, where the EG is formed, were collected in layers and broilers in order to investigate Chem differential expression by RT-qPCR between both breeds. Chem concentration in EW was dependent on the time of laying period and its profile was differently regulated in layers and broilers. Indeed, it increased at the end of laying in layers whereas it decreased after the laying peak in broilers. At the end of laying period, Chem concentration in EW was almost 2-fold higher in layers than in broilers and this was confirmed in both G0 and G1 generations at the Chem mRNA and protein levels in the magnum. For the 2 successive generations, Chem concentration in EW was negatively correlated with the laying rate and the fertility parameter in broiler hens whereas it was negatively correlated with the egg quality (weight of whole egg and weight of albumen) and positively with the fertility rate at some time of laying in layer hens. Taken together, the Chem concentration in EW could be a potential predictive tool for reproductive parameters in genetic selection.

Keywords: broiler; chemerin; egg white; hens; layer.

Figure 1

Design experimental. Hundred layer and broilers hens and their offsprings were followed at 3 times of the laying period: before and after laying peak and at the end of laying. For each time and during 5 successive laying days, eggs were collected in order to weigh the whole egg, egg white (albumen), and yolk individually. For each egg, an albumen sample was stored at −20°C until use.

Figure 2

Egg performances for each breed for both generation during the cycle of laying. Egg, albumen, and yolk weight for the first generation G0 (A–C) and offsprings G1 (D–F) during the cycle of laying (n = 68–100 animals per breed). Data are shown as the mean ± SEM. Different capital letters indicate a significant laying period effect (E) and different asterisks ** indicate significant differences between layer and broiler hens as breed effect (G) at P < 0.01; ***P < 0.001 and ****P < 0.0001. An interaction between breed and period of laying (GxT) was analyzed.

Figure 3

Concentration of chemerin in egg white in each breed for both generation during the cycle of laying. Concentration of chemerin in egg white for layer and broiler breeds at first generation G0 (A, B) and second generation G1 (D, E) during different times of laying was determined by ELISA assay. For each generation, 1-way ANOVA to analyze the effect of laying period (A, B, D, and E) and the 2-way ANOVA were used to determine a breed (G) and a laying period (T) effect and an interaction (GxT) for the concentration of chemerin in egg white (C, F). Data are shown as the mean ± SEM. Different capital and lowercase letters indicate a significant laying period effect (E) and different asterisks **** indicate significant differences between layer and broiler hens as a breed effect (G) at P < 0.0001.

Figure 4

Expression of chemerin and its receptors in the magnum of the oviduct of layer and broiler hens at G0 and G1 generation. Relative mRNA expression of RARRES2 (chemerin gene) (A, B) and its 3 receptors CMKLR1 (C, D), GPR1 (E, F), and CCRL2 (G, H) in the magnum of broiler and layer oviduct at G0 and G1 generation quantified by RT-qPCR (n = 5–10). Values are expressed as mean ± SEM. Different asterisks * indicate significant differences between layer and broiler hens at P < 0.05; **P < 0.01 and ***P < 0.01.

Figure 5

Abundance of chemerin in magnum in each breed for both generation. Protein amount of chemerin in magnum of layer and broiler hens for the first generation G0 (A) and second generation G1 (B) detected by Western blotting. The ratio protein/Ponceau is represented. Different asterisks * indicate significant differences between layer and broiler hens at P < 0.05.