Effects of Photoperiod and Age: RESULTS(5)

RESULTS(5)

LH pulse number and pulse amplitudes were highly variable between birds within groups and were not different between ages and between lighting treatments within ages (p > 0.05; Fig. 6, C and D). Overall mean and baseline levels of T were lower at 13 wk of age than at 23 and 35 wk of age (p < 0.05) but not different between 23 and 35 wk of age (Fig. 7, A and B). Overall mean and baseline concentrations of T were not different between the LL and SL groups at 13 wk of age but were higher in the LL group than the SL group at 23 wk of age. At 35 wk of age, the LL group demonstrated a higher overall mean level of T with no difference in T baseline level (Fig. 7, A and B). buy cheap antibiotics

The number of pulses of T increased from 13 to 23 wk of age but decreased to an intermediate level at 35 wk of age (Fig. 7C). Pulse amplitude of T was higher in the LL group at 23 wk of age (Fig. 7D) but was not influenced by lighting treatments at other ages. Concentrations of plasma T4 were determined in all samples of trial 2 (Fig. 8A) and for the first samples of serial bleedings of trial 3 (Fig. 8B). In trial 2, concentrations of T4 were higher at most ages in the LL group than in the SL group before 23 wk of age. After the SL group was switched to LD at 29 wk, no difference in concentration of T4 was observed between lighting treatments at any age. No differences in T4 concentration between lighting treatments were detected in trial 3. However, T4 concentration was higher at 13 wk than at 23 and 35 wk. Fig7Effects of Photoperiod FIG. 7. Overall mean (A), baseline (B), pulse numbers (C), and amplitude concentrations (D) of T (mean ± SD), trial 3. Different letters within a group (age or treatment within age) indicate significant differences (p < 0.05); n = 8 for each age, n = 4 for each age/treatment. Fig8Effects of Photoperiod FIG. 8. T4 concentrations (mean ± SD). A) From 12 to 35 wk of age, trial 2 (open symbols indicate LL, n = 8; solid symbols indicate SL, n = 9). * Difference between treatment groups at each age in A. B) From 13, 23, and 35 wk of age, trial 3 (n = 8 for each age, n = 4 for each age/treatment). Different letters within a group (age or treatment within age) indicate significant differences (p < 0.05).

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