In young male domestic fowls, the effects of weekly 8‐h advance or delay shifts on growth and circadian rhythm of the core temperature were evaluated. The results indicate that the growth rate was significantly higher only in the birds of the advance schedule. ANOVA results suggest statistically significant inhibition in the growth rate of delay‐schedule birds. Further, the birds of the control group exhibited a circadian rhythm in core temperature. This rhythm disappeared in delay‐schedule birds soon after imposition of the shifts and reappeared on the 3rd post‐shift day. This phenomenon was found to be uncommon among the advance‐schedule birds. The poor growth rate of the delay‐schedule birds could be attributed to desynchronization of core temperature circadian rhythm.