Estradiol-17ß Is Influenced by Age, Housing System, and Laying Performance in Genetically Divergent Laying Hens (Gallus gallus f.d.)

Abstract

The estrogen estradiol-17ß is known as one of the major gonadal steroid hormones with different functions in reproduction. In this study we analyzed estradiol-17ß concentration in laying hens of four pure bred chicken laying lines at four different time intervals of the laying period (17th-19th week of age, 33rd-35th week of age, 49th-51st week of age, and 72nd week of age). The high performing white egg (WLA) and brown egg (BLA) layer lines as well as the low performing white (R11) and brown (L68) layer lines were kept in both single cages and a floor housing system. We investigated whether there were differences in estradiol -17ß concentrations between lines at different ages that could be related to selection for high egg production or phylogenetic origin of the animals, and whether there was an influence of housing conditions on estradiol-17ß. Estradiol-17ß concentrations differed between high and low performing layer lines at all time intervals studied. High performing hens showed higher estradiol-17ß concentrations compared to low performing hens. In all lines, highest estradiol-17ß concentration was measured at their 49th to their 51st week of age, whereas the peak of laying intensity was observed at their 33rd to their 35th week of age. Additionally, hens with fewer opportunities for activity housed in cages showed higher estradiol-17ß concentrations than hens kept in a floor housing system with more movement possibilities. We could show that laying performance is strongly linked with estradiol -17ß concentration. This concentration changes during laying period and is also influenced by the housing system.

Keywords: cage housing; egg laying performance; estradiol; floor housing; housing condition; keel bone damage; laying hen; laying intensity.

FIGURE 1

Estradiol-17ß blood plasma concentration (pg/ml) and laying intensity (%) of four different layer lines kept in different housing systems and investigated at four time periods (17th, 18th, and 19th week of age (before start of laying); 33rd, 34th, and 35th week of age (maximum of egg production); 49th, 50th, and 51st week of age (decrease in egg production in low producing lines) and 72nd week of age (end of experiment). The laying intensity is shown after each week of blood sampling (A) Estradiol-17ß concentration of the two high performing layer lines (WLA, BLA) and the two low performing layer lines (L68, R11) respectively cage-housed and floor-housed laying hens (B), consisting of WLA, BLA, L68, and R11 hens) during their laying period (C) Laying intensity of all four-layer lines and of cage-housed and floor-housed laying hens (D) during their laying period.