Effects of dietary corticosterone on yolk colors and eggshell quality in laying hens.

The objective of this study was to investigate the effects of dietary corticosterone on egg quality. For 2 weeks hens received either control or experimental diet containing corticosterone at 30 mg/kg diet. Feed intake and egg production were monitored daily, and body weight measured weekly. Egg weights and egg quality were measured daily. Corticosterone treatment resulted in a remarkable increase in feed intake and sharp decrease in egg production compared with control (p<0.05) whereas body weight remained unchanged. Decreased albumen height, but no changes in egg weight, led to decreased Haugh unit (p<0.05). Corticosterone caused elevated eggshell thickness (p<0.05) without altering weight and strength, suggesting possible changes in shell structure. Yolk color and redness were increased by corticosterone (p<0.05) but lightness and yellowness were either not changed or inconsistent over the time period of measurements. Increased concentrations in plasma were also found for corticosterone, glucose, cholesterol, creatinine, uric acid, albumin, aspartate aminotransferase, creatine kinase, lactate dehydrogenase, total protein, and amylase (p<0.05), suggesting that corticosterone increased protein breakdown, renal dysfunctions and pancreatitis. Together, the current results imply that dietary corticosterone affects egg quality such as yolk colors and shell thickness, in addition to its effects on feed intake and egg production.