Han-Ken Liu

Frequency of luteinizing hormone surges and Egg production rate in Turkey hens

Abstract Whether the interval between preovulatory surges of LH was different between lines of turkey hens with either poor (RBC3 line, peak at 55%) or excellent rate of egg production (Egg line, peak at 85%) was examined. Laying hens were cannulated and bled hourly for 10 days at peak of production. A constant light photoschedule was used to avoid diurnal masking of innate circadian rhythms. The mean interval between LH surges in the RBC3 line was longer than in the Egg line and had a higher coefficient of variation. A few longer LH surge intervals (>72 h) were found in some RBC3 line hens (2 of 7 hens), but none were found in Egg line hens (0 of 11 hens). All progesterone (P4) surges were coupled with LH surges, but not all LH-P4 surges were coupled with ovipositions (blind LH-P4 surges). The percentage of blind LH-P4 surges was not different between lines. The baseline concentration of LH was higher in Egg line than RBC3 line hens, but LH surge amplitude, and surge duration were not different. The baseline and surge amplitude concentrations of P4 were not different between lines, nor was the concentration of estradiol-17β. The longer interval between LH surges was the major factor tested that was associated with the poorer egg production rate in RBC3 line hens in comparison to Egg line hens. A higher incidence of blind LH surges further contributed to lower egg production in RBC3 line turkey hens.

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

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 (P4) increased, and concentrations of estradiol-17β (E2) 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 P4 surges. Those LH and P4 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 P4 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 P4 surges (10.0 ± 2.0 h). We conclude that, in the peripubertal female turkey, 1) prior to puberty (first LH-P4 surges), there are no circadian fluctuations in concentrations of LH, P4, and E2, 2) 3 days prior to initial LH surges, E2 concentrations are stable, LH concentrations decline slightly, and P4 concentrations increase, and 3) surges of LH are coupled to surges of P4 but LH-P4 surges are not always coupled to ovipositions (blind surges), possibly because of internal ovulations.

Progesterone Injection and Egg Production in Turkey Hens

Abstract An arrest in laying associated with either a polyovarian follicle (POF) or a polycystic ovarian follicle (PCOF) syndrome has been reported in turkey hens photostimulated at an early age with a constant-light photoperiod. Hens expressing the POF or PCOF syndrome had stopped laying for several weeks, but the ovary contained an increased number of mature-size and larger follicles (POF hens), which were cystic (PCOF) in some of the hens. Hens with the POF or PCOF syndrome had plasma progesterone (P4) concentrations that were relatively high and without surges. We hypothesized that high plasma P4 concentrations may block ovulatory surges of LH but not the growth or maintenance of hierarchical follicles leading to development of the POF or PCOF syndrome in turkey hens. In the first six studies, hens were photostimulated with either a 14L:10D or a 24L:0D photoperiod and, after laying for 1–38 wk, were then injected daily for up to 14 days with P4 (up to 1.50 mg kg−1 day−1) and necropsied. At all ages, the oviposition rate was reduced at a P4 dosage of 0.17 mg kg−1 day−1. With dosages of 0.33 mg kg−1 day−1 or greater, however, ovipositions stopped in most hens within approximately 2 days. For hens laying for less than 15 wk, oviductal weight and number of hierarchical follicles of P4-injected hens were not different from control vehicle-injected hens, but the numbers of mature, cystic, and atretic follicles were increased. For hens laying for 38 wk, when treated with P4, oviductal weight and number of hierarchical follicles decreased, but number of atretic follicles increased. No effect of photoperiod was found on egg production, oviductal weight, or follicle number, and none of the hens developed POF or PCOF syndrome in these experiments. Two additional experiments were conducted with hens early in the reproductive period that had been photostimulated with 14L:10D or 24L:0D and injected with P4 (0.33 mg kg−1 day−1) for 10 or 12 days but not necropsied until 3 wk after the last injection. Most of the hens photostimulated with the 24L:0D photoperiod and injected with P4, and a few of the hens photostimulated with the 14L:10D photoperiod and injected with P4, had developed the PCOF syndrome when necropsied. The hens with the PCOF syndrome had high levels of P4 when necropsied. From these studies, we concluded that the PCOF syndrome can be induced early in the reproduction period by photostimulating turkey hens with a 24L: 0D photoperiod, injecting them for 10 to 12 days with P4 at a dosage of 0.33 mg kg−1 day−1, and then waiting 3 wk for the PCOF syndrome to develop.