Age related modulation of circadian time structure of blood, plasma and tissue variables in male domestic fowls.

ABSTRACT

To study modulation of circadian time structure of 11 blood, plasma and tissue variables in male domestic fowls, as a function of age, three experiments were made in one-day-old fowls (72) standardized by 12L12D. In the first experiment, at 6 week age, 24 birds were killed by decapitation, four each at six different circadian stages (2, 6, 10, 14, 18 and 22 hr after light onset, HALO). Equal number of birds were killed at similar circadian stages at the age of 12 and 18 week in the second and the third experiments, respectively. Age affected both, the circadian patterns and the mesors (24 hr mean values). The circadian pattern included amplitude (half of the total extent of variation) and acrophase (estimated time of peak) for each variable. The results clearly suggest that the pattern of circadian rhythm may vary as a function of age of the bird.