Phospholipid Content of the Chicken Shell Gland and Its Relationship to Egg Shell Strength

Egg shell strength declines during the latter part of the laying cycle. Shell gland (uterine) lipids have been postulated to be associated with this decline. A membrane-bound Ca2+-adenosine triphosphate (ATP)ase has been shown to require phospholipids for maximum activity. It is hypothesized that the age-associated decline in shell strength is the result of alterations in shell gland phospholipids. Shell strength, as assessed by shell surface density, of eggs from two commercial strains of hens in their first cycle of lay was monitored during the latter half of the laying cycle and following an induced molt. Significant differences were not detected in abdominal fat weight, oviduct weight, or total lipid concentration of the shell gland of hens that produced premolt strong egg shells (SES) and weak egg shells (WES). The SES hens had higher concentrations of shell gland phosphatidylcholine (PC) and lower concentrations of shell gland phosphatidylethanolamine (PE) than WES hens. The ratio of PC:PE was significantly lower in WES hens in the premolt than in the postmolt phase. An improvement in shell strength after the induced molt was associated with an increase in shell gland PC:PE ratio. These results indicate that the weak egg shells produced towards the end of lay are laid by hens whose shell gland contains less PC and a lower ratio of PC:PE. The differential response after an induced molt supports the hypothesis of a cause and effect relationship. These alterations could affect the function of Ca2+-ATPase and egg shell calcification.