Plasma, Follicular, and Uterine Levels of Prostaglandins in Chickens Laying Soft-Shelled and Shell-Less Eggs

Not all eggs produced by chickens are laid at the expected time of oviposition. Some eggs are laid prematurely, which result in inadequate shells. These uncollectible eggs are referred to as soft-shelled (partial calcification) or shell-less (no calcification) eggs. Of all soft-shelled or shell-less eggs that were laid in the present study, 57% were expelled prematurely. To determine whether prostaglandins were correlated with the expulsion of soft-shelled or shell-less eggs, prostaglandin F2alpha (PGF2alpha), 13,14-dihydro-15 keto prostaglandin F2alpha (PGFM), and 13-14-dihydro-15 keto prostaglandin E2 (PGEM) were measured in the peripheral plasma and follicular and uterine tissues of hens laying soft-shelled eggs and shell-less eggs. Controls were represented by hens laying hard-shelled eggs (normal calcification). Plasma concentrations of PGFM increased (P less than .01) upon the premature oviposition of soft-shelled eggs but not shell-less eggs. The source of the peripheral PGFM may have been the preovulatory follicle, because PGF2alpha levels were higher (P less than .07) in the soft-shelled or shell-less egg layers when compared with the controls. Plasma and tissue levels of PGEM did not differ between hens laying soft-shelled or shell-less eggs versus hard-shelled eggs. These results suggest that PGF2alpha and PGFM are involved in the premature oviposition of some chicken eggs.