Chicken white egg chemerin as a tool for genetic selection for egg weight and hen fertility

Abstract

Embryo mortality rate, which can reach up to 40% in avian species, is a major issue for breeding. It is therefore important to identify new embryo development biomarkers for genetic selection to improve reproductive performances. We have recently shown that chemerin is expressed in the oviductal hen magnum, accumulates in egg white, is correlated with embryo survival and could thus be used as a molecular marker of embryo development. Eggs from seven hen breeds (n = 70) were collected during five successive days at the end of the laying period. After weighing eggs, yolk and albumen, an egg white sample from each egg was collected and a blood sample was taken from each hen. Chemerin concentrations in albumen and blood samples were measured by a specific home made ELISA assay. Hen's plasma and egg's albumen chemerin levels were found to be correlated with reproductive parameters such as fecundity, fertility, embryo mortality, hatchability and laying rates. The inter-hen chemerin level variability in albumen was higher than intra-hen except for one breed (R+). We observed significantly different levels of chemerin in egg white between breeds. However, chemerin concentrations in egg white were not significantly associated to variations of hen plasma chemerin levels. Interestingly, we observed negative correlations between albumen chemerin concentrations and egg weight (r = -0.43, p = 0.001), between albumen weight (r = -0.40, p = 0.002), and between yolk weight (r = -0.28, p = 0.03). We also showed negative correlations between egg white chemerin concentrations and fecundity (r = -0.32, p = 0.011) and fertility (r = -0.27, p = 0.04) whereas no significant correlation was observed with the laying rate. Taken together, these results suggest that egg white chemerin concentration might be a good biomarker for genetic selection for egg weight and fertility in hens, provided these data are confirmed on a larger scale.

Keywords: chemerin; egg performance; egg white; fertility; hen.

FIGURE 1

Experimental design. Seventy fasted hens (54 weeks-old, end of laying) from seven Rhode Island breeds (n = 10 hen per breed) were used. During five days of laying, eggs were successively collected in order to weigh the egg, egg white (albumen) and yolk individually. For each egg, an albumen sample was stored at −20°C until use. At the end of the protocol, all hens were euthanized by electrical stunning and bled out for blood sample collection.

FIGURE 2

Concentration of chemerin in plasma (A) and egg white (B) in each breed of hen as determined by ELISA assay. Concentration of chemerin in plasma (A) and in egg white from eggs (B) was determined by ELISA assay in seventy 54-old hens from seven different breeds. Data are shown as the mean ± SEM; n = 6–10 animals per breed. Groups showing different letters are significantly different (p < 0.05).

FIGURE 3

Concentration of chemerin in egg white by two methods of analysis. (A) Protein abundance of chemerin detected by western blotting within 3 or 4 or 5 egg whites laid successively in two hens named C254 and C261, respectively (n = 4–5). (B) Chemerin concentration determined by ELISA assay within the same egg whites samples as (A). Data are shown as the mean ± SEM; n = 4 to 5 samples per animal. Significant differences are indicated by p < 0.01 ** and ***p < 0.001. (C) Sixty-one egg white samples from eggs laid by different hens were collected and analysed by both ELISA and Western-blot assays. Correlation between chemerin concentration within albumen obtained by western blotting and ELISA assay (n = 61) is shown.

FIGURE 4

Abundance of chemerin in egg white of different avian species. (A) Protein amount of chemerin in egg white from egg of different avian species was detected by western blotting. Data are shown as the mean ± SEM; n = 3 egg white samples from different animals of various avian species. Groups showing different letters are significantly different (p < 0.05). (B) Chemerin protein expression in human, mouse and chicken blood plasma samples (n = 3 for each species). All plasma samples contained equal amounts of proteins, as confirmed by staining the nitrocellulose membrane with Red Ponceau.