Coordinate Pattern of Secretion of Luteinizing Hormone and Testosterone in Mature Male Turkeys Under Continuous and Intermittent Photoschedules

Abstract

Secretory patterns of luteinizing hormone (LH) and testosterone (T) were determined in sexually mature male turkeys housed under Continuous [14 h light (L): 10 h dark (D), n = 3)] or Intermittent [8 x (1L:2D), n = 3] photoschedules. Jugular vein cannulas were implanted on Day 0 and serial blood samples were taken at 5-min intervals for 12 h on Day 3 and again 4 to 7 d later. Most increases in T concentration were preceded by an increase in LH concentration for both photoschedules. Treatment differences for overall mean T [1.77 +/- .58 (SE) ng/mL], baseline T (.92 +/- .30 ng/mL), T peak number (6.1 +/- 1.2 per 12 h), T peak amplitude (2.77 +/- 1.70 ng/mL), or T peak length (79 +/- 24 min) were not significant (P > .05). The number of LH peaks was greater in the Continuous than Intermittent group (11.7 +/- .6 vs 6.8 +/- 1.4 per 12 h, P < .05), but there were no treatment differences in overall mean LH (4.56 +/- 2.09 ng/mL), baseline LH (4.10 +/- 2.11 ng/mL), LH peak amplitude (2.80 +/- .92 ng/mL), or LH peak length (15.9 +/- 3.1 min). There were no differences in T or LH concentrations between the photo- and scotophases in the continuous group, and pulses of both were seen in both phases in both lighting treatments. It was concluded that minor differences in patterns of LH secretion may occur between Continuous and Intermittent stimulatory lighting treatments in sexually mature male turkeys.