Changes in Plasma Concentrations of Luteinizing Hormone, Progesterone, and Estradiol-17β in Peripubertal Turkey Hens under Constant or Diurnal Lighting1

Abstract

Possible circadian fluctuations and long-term changes in concentrations of reproductive hormones in peripubertal female birds is poorly documented in comparison with mammalian species. Our objective was to document changes in concentrations of several reproductive hormones the several days before and after initial pubertal preovulatory surges of LH in turkey hens photostimulated with either constant (24L:0D) or diurnal (14L:10D) lighting. The hens were cannulated for hourly blood sampling, starting 10 days after photostimulation and continuing until all hens had laid at least two eggs. First eggs were oviposited between 16 and 24 days after photostimulation, and egg production ranged from two to nine eggs/hen during the experimental period. With both lighting treatments, concentrations of LH declined slightly, concentrations of progesterone (P(4)) increased, and concentrations of estradiol-17beta (E(2)) were constant the 3-4 days prior to initial LH surges with no circadian fluctuations in hormone concentrations. Most (10 of 13) initial preovulatory surges of LH were coupled with ovulations, and all LH surges were coupled with P(4) surges. Those LH and P(4) surges not coupled with ovulations (blind surges) occurred with both lighting treatments, but the incidence of blind surges was higher with diurnal lighting. The interval between LH and P(4) surges was longer between the first and second surges than between subsequent surges, when the interval was approximately 26 h. The duration of LH surges (7.4 +/- 3.0 h) was shorter than that of P(4) surges (10.0 +/- 2.0 h). We conclude that, in the peripubertal female turkey, 1) prior to puberty (first LH-P(4) surges), there are no circadian fluctuations in concentrations of LH, P(4), and E(2), 2) 3 days prior to initial LH surges, E(2) concentrations are stable, LH concentrations decline slightly, and P(4) concentrations increase, and 3) surges of LH are coupled to surges of P(4) but LH-P(4) surges are not always coupled to ovipositions (blind surges), possibly because of internal ovulations.

Characterization of ovarian follicles, serum steroid hormone concentration, and steroidogenic gene expression profiles in the developing ovarian follicles in White King pigeons

“…From LI5 to LI7, the growth rate of F1 and F2 slowed, with the change pattern similar to P 4 . The E 2 in turkey hens does not change much during the egg production period ( Bacon et al, 2002 ; Brady et al, 2019 ), which was consistent with these results. Although T concentrations fluctuated, its overall trend decreasing during the LI of the pigeon.…”

Progesterone Injection and Egg Production in Turkey Hens1

“…Concentrations of P 4 24 h after injection of P 4 at dosages of 0.33 or 0.50 mg kg Ϫ1 day Ϫ1 were similar to ovulatory surge levels in laying turkey hens. It has previously been reported [1,34] in turkey hens that ovulatory surges of LH occur only when P 4 levels have been at baseline for several hours. This suggests that if P 4 does not drop below ovulatory surge levels, then ovulatory surges of LH may be blocked, thereby blocking ovulation.…”

“…In the younger hens, however, the oviduct was maintained at a weight comparable to that of laying hens, whereas the ovary was maintained in a stimulated state that was different from that of laying hens. Ovulatory surge levels of P 4 in plasma of laying turkey hens range from between approximately 5 and 8 ng/ml, whereas baseline levels between surges range between 1 and 2 ng/ml [1,34]. The data from experiments 2 and 6 indicate that baseline levels of P 4 24 h after injection were associated with dosage injected and peaked between 2.5-and 6-h postinjection at levels approximately 3.3-fold higher than the baseline associated with each dosage.…”

Age-related changes in the gross anatomy of the reproductive organs, and associated steroid hormone profiles in male and female guinea fowls (Numida meleagris)

“…The increase in progesterone concentrations 6–4 h before ovulation ( Bacon et al., 2002 , Etches, 1990 ) is predominantly the result of increased secretion by the largest preovulatory follicle ( Etches, 1990 ). Similarly, preovulatory follicle secretion of oestradiol increases in each of the four largest follicles 6–3 h prior to ovulation and is greatest in the third- and fourth-largest follicles.…”