Correlation between the age of pinealectomy and the development of scoliosis in chickens

Study Design. Pinealectomy induces experimental scoliosis in chickens. This study analyzed the correlation between the age at which pinealectomy was p erformed and the development of scoliosis in chickens. Objective. To investigate the differences in the rate or magnitude of scoli osis and the type of curvature in chickens pinealectomized at different lim es after hatching. Summary of Background Data. Scoliosis develops in almost ail chickens pinea lectomized within 3 days after hatching, hut there are no data on whether t he condition will develop in chickens pinealectomized earlier or later afte r hatching. Methods. In this study, 106 female white leghorn chickens were divided into six groups: four pinealectomy groups (pinealectomy was performed 2, 4, 11, or 18 days after hatching in Groups P-2, P-4, P-11, and P-18, respectively ), a control group (Group C), and a sham operation group (Group S), Ventrod orsal radiographs of the spine were taken at 4-week intervals until the age of 12 weeks. At 12 weeks, a 1-mL sample of blood was taken from the heart at the middle of the dark cycle, and the serum melatonin concentration was measured by radioimmunoassay. Results. At the age of 12 weeks, scoliosis was present in 63.6% of the chic kens in Group P-2, 72.7% in Group P-4, 81% in Group P-11, and 70% in Group P-28, and the Cobb angles in the scoliotic chickens averaged 32.6, 29.8, 23 .8, and 22.3 degrees in the respective groups. There were no significant di fferences in the rate or magnitude of scoliosis and the type of curvature a mong the pinealectomy groups at the age of 12 weeks. At the age of 12 weeks , the serum melatonin levels at the middle of the dark cycle in the pineale ctomized chickens were significantly lower than those of chickens in Groups C and S. However, there were no differences in the serum melatonin levels between scoliotic and nonscoliotic pinealectomized chickens. Conclusions. Findings from this study show that scoliosis develops in 60% t o 80% of chickens pinealectomized within 18 days after hatching, and that s coliotic development is not influenced by the age at which pinealectomy is performed. However, this study suggests that melatonin plays a complicated role in spinal development, inasmuch as the serum melatonin levels after pi nealectomy approximated zero. Yet scoliosis did not develop in all pinealec tomized chickens.