Abstract
Summary
Pinealectomized cockerels (PX) were individually exposed to a thermocline (20 to 34°) throughout both phases of the light-dark cycle (12L:12D). Twelve birds from each surgical treatment, including sham operated (PN) and unoperated controls (C), were singly placed in the thermocline for 100 min during photophase and scotophase in 4-hr segments designated early (E), middle (M), and late (L). Prior to placement in the thermocline, PX birds had a lower mean T r (40.15°) than PN and C groups (40.64°). During photophase, PX birds selected a higher T a during the E and L segments, but preferred a T a similar to PN and C cockerels for M photophase (23°). This produced an interaction (P < 0.05) between pinealectomy and T a selection during photophase. The PX group had a T a preferendum of 29.7° for scotophase in contrast (P < 0.05) to 25.4° selected by PN and C birds. The average T a preferred by PX birds across both phases of the light-dark cycle was 28° (P < 0.05) while on the average, PN and C groups selected 24°.
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