Changes in the plasma LH, progesterone, and estradiol during the ovulatory cycle of the duck (Anas platyrhynchos domestica) exposed to different photoperiods

Adipokines Expression and Effects in Oocyte Maturation, Fertilization and Early Embryo Development: Lessons from Mammals and Birds

Some evidence shows that body mass index in humans and extreme weights in animal models, including avian species, are associated with low in vitro fertilization, bad oocyte quality, and embryo development failures. Adipokines are hormones mainly produced and released by white adipose tissue. They play a key role in the regulation of energy metabolism. However, they are also involved in many other physiological processes including reproductive functions. Indeed, leptin and adiponectin, the most studied adipokines, but also novel adipokines including visfatin and chemerin, are expressed within the reproductive tract and modulate female fertility. Much of the literature has focused on the physiological and pathological roles of these adipokines in ovary, placenta, and uterine functions. The purpose of this review is to summarize the current knowledge regarding the involvement of leptin, adiponectin, visfatin, and chemerin in the oocyte maturation, fertilization, and embryo development in both mammals and birds.

Plasma Concentrations of Immunoreactive (ir)-Inhibin, Gonadotropins and Steroid Hormones during the Ovulatory Cycle of the Duck

The present study was undertaken to determine changes in circulating levels of immunoreactive (ir)-inhibin, FSH, LH, estradiol-17beta, progesterone, and testosterone during the ovulatory cycle of Shao ducks. Serial blood samples were taken from two groups of laying ducks for measurement of ir-inhibin, gonadotropins, and steroid hormones at 2 h intervals for 24 h. Plasma concentrations of ir-inhibin did not change significantly during the ovulatory cycle. The highest level of plasma ir-inhibin was observed 6 h prior to ovulation, which coincided with a decreased level of plasma FSH. One FSH surge was found 12 h after ovulation. Estradiol-17beta, progesterone, and testosterone were also determined during the ovulatory cycle. Two peak values were detected for estradiol-17beta 8 h before ovulation and 4 h after ovulation, while progesterone started to increase 4 h before ovulation and reached a peak at ovulation. The highest level of plasma testosterone was detected around the time of ovulation. These results suggest that inhibin may be involved in the control of FSH secretion during the ovulatory cycle. In addition, both LH and progesterone are of importance in the ovulation process of Shao ducks.

Preovulatory surge patterns of luteinizing hormone, progesterone, and estradiol-17β in broiler breeder hens fed ad libitum or restricted fed

Spontaneous ovulations are induced by preovulatory surges of luteinizing hormone (LH) and progesterone (P4) during ovulatory cycles in birds, but estradiol-17beta (E2) levels are relatively constant. Egg production is enhanced in restricted fed (RF) in comparison with ad libitum fed (FF) broiler breeder hens, but changes in concentrations and peripheral patterns of LH, P4, and E2 during ovulatory cycles in broiler breeder hens are poorly documented. The hypothesis of this study was that high resolution patterns of peripheral LH, P4, and E2 during preovulatory surges would not be different between FF and RF broiler breeder hens. Seven FF and 6 RF broiler breeder hens were photostimulated with 16 L:8 D at 22 wk of age. At 28 wk of age, the hens were cannulated for serial blood sampling and switched to a 24L:0D photoperiod to allow preovulatory surges of LH and P4 to run freely. Three days after cannulation, hens were serially bled every 12 min for 36 h. The FF hens were heavier than the RF hens (5.60 +/- 0.35 vs. 3.60 +/- 0.28 kg, respectively; P < 0.01). During the 10 d before cannulation, total egg production of the FF and RF hens (8.3 +/- 1.4 and 6.8 +/- 1.3 eggs, respectively; P = 0.08) and normal egg production (5.6 +/- 1.8 and 6.5 +/- 1.8 eggs, respectively; P = 0.37) were not different. The FF hens, however, had more abnormal eggs than the RF hens (2.7 +/- 1.7 and 0.3 +/- 0.8 eggs, respectively; P < 0.01). None of the hormonal measurements was different between the FF and RF hens (P > 0.05). The concentrations of hormones for the FF and RF hens, respectively, were as follows: baseline LH (2.79 +/- 0.45 vs. 2.94 +/- 0.60 ng/mL) and P4 (1.68 +/- 0.56 vs. 1.41 +/- 0.43 ng/mL), overall mean LH (3.18 +/- 0.45 vs. 3.10 +/- 0.46 ng/mL) and P4 (2.32 +/- 0.55 vs. 2.09 +/- 0.91 ng/ mL), preovulatory surge amplitude of LH (5.43 +/- 1.27 vs. 3.88 +/- 1.24 ng/mL) and P4 (6.08 +/- 2.09 vs. 6.71 +/- 3.91 ng/ mL), preovulatory surge duration of LH (7.52 +/- 1.80 vs. 5.74 +/- 3.18 h) and P4 (7.52 +/- 1.42 vs. 8.20 +/- 1.24 h), and overall mean E2 (0.25 +/- 0.05 vs. 0.23 +/- 0.05 ng/mL). In conclusion, there were no differences in total egg production or normal egg production between FF and RF broiler breeder hens, but the FF hens laid more abnormal eggs. Also, there were no differences in the concentrations or peripheral patterns of LH, P4, and E2 during preovulatory surges between the FF and RF broiler breeder hens.

Frequency of Luteinizing Hormone Surges and Egg Production Rate in Turkey Hens1

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-P(4) 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-17beta. 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.

Effect of exogenous progesterone on luteinizing hormone secretion in domestic turkey hens at different reproductive states

To determine effects of progesterone (P4) treatment on luteinizing hormone (LH) secretion in turkey hens, two trials were conducted. Trial 1 was to determine changes in LH, P4, and testosterone (T) during photostimulation. Photosensitive turkey hens were maintained under short days (SD) of 6 h light and 18 h dark. At the beginning of Trial 1, blood samples were taken daily for 4 days, then one-half of the hens were switched to long days (LD) of 14 h light and 10 h dark, and daily blood samples were continued until 5 days after eggs were laid by all the hens switched to LD. Concentrations of LH, P4, and T increased significantly 1 day after switching hens from SD to LD, but the increase in P4 was initially low with a further increase occurring by 3 days prior to first eggs. In Trial 2, turkey hens were injected with exogenous P4 to determine if P4 is an initiator of the preovulatory surge of LH. P4 or vehicle were injected im in hens at three different reproductive states: (1) while hens were maintained under SD, (2) on the 5th day after hens were switched from SD to LD, and (3) after hens were laying for 1 week. The hens were serially bled at 10-min intervals for 8 h to monitor changes in LH and P4. After 2 h of serial bleeding, P4 or vehicle was injected and bleeding was continued for an additional 6 h. After P4 injection, its concentration increased rapidly from a base level of 0.25-1.20 ng/ml to a postinjection high level of 4.42-6.10 ng/ml within 20 min. The high level of P4 was then maintained throughout the remaining 6 h. No increases of LH secretion were observed after P4 or vehicle injection in hens at either State 1 or State 2. Small increases of LH secretion were detected about 2 h after P4 injection in hens at State 3, but these increases were not significantly above vehicle-injected controls. Thus, there was no positive feedback effect of P4 injection on LH secretion in this trial. These results suggest that P4 might not induce LH secretion in immature or mature turkey hens and might not be the factor which induces the preovulatory surge of LH in laying turkey hens. Nonsteroidal factors of ovarian origin might be involved in regulating the preovulatory surge of LH in turkey hens.

Changes in plasma concentrations of luteinizing hormone, progesterone, and testosterone in turkey hens during the ovulatory cycle

Changes in luteinizing hormone (LH), progesterone, and testosterone concentrations were determined in blood samples taken every 10 min for 26 hr during an ovulatory cycle in laying turkey hens. During the 26-hr sampling period, one peak of both LH and progesterone and numerous peaks of testosterone were detected. The concentration of LH in plasma increased from basal level (2.44-4.0 ng/ml) to maximum level (8.57-24.3 ng/ml) over 1 to 2 hr and then declined over 3 to 5 hr to a basal level. The duration of the descending portion of the peak was about double that of the ascending portion. The concentration of progesterone increased rapidly from a basal level of 1.18-1.65 ng/ml to a peak of 6.18-11.87 ng/ml and then maintained a plateau before rapidly declining to basal level. The concentration of testosterone increased from a basal level of 0.06-0.09 ng/ml to a peak level of 0.13-0.30 ng/ml. All maximum levels of testosterone preceded those of LH, and all maximum levels of LH preceded those of progesterone. The durations of the progesterone peaks were longer than those of the LH peaks. Progesterone concentrations returned to basal level after LH had returned to basal level, although the initial increase in progesterone concentration was earlier, later, or at the same time as LH. Peak durations of testosterone were variable. The preovulatory surges of LH and progesterone of five of nine sets of samples started at the end of the scotophase and ended during the beginning portion of the photophase. In three of nine sets both the start and the end occurred druing the scotophase and in one of nine sets during the photophase. It was concluded from this study that the patterns of secretion of LH, progesterone, and testosterone were similar in that the preovulatory surge was superimposed on a relatively stable basal level, while the temporal relationships of the ovulatory surges of these hormones were variable. The preovulatory surges were more tightly associated with ovulation rather than with photoperiod. Neither progesterone nor testosterone might be an initiator of the LH surge prior to ovulation.

Avian reproductive endocrinology

Hypothalamic-releasing factors regulate the secretion of anterior pituitary hormones. The anterior pituitary gland secretes the same six hormones as found in mammals: FSH, LH, prolactin, GH (somatotropic hormone), ACTH, and TSH, plus the melanotropic hormone. The endocrine hormones of the avian posterior pituitary gland concerned with reproduction are mesotocin and AVT. The pineal gland, through the secretion of the hormone melatonin, modulates the periodic autonomic functions of the central nervous system. The ovary produces estrogens, progestogens, and androgenic compounds. The testes produce testosterones and progesterone. The thyroid glands produce two hormones, T4 and T3. The avian adrenal glands produce corticosterone and aldosterone. The bursa of Fabricius is considered an endocrine organ since it is involved in the production of humoral factors. The male reproductive system undergoes hormonal changes associated with puberty, the breeding season, and molt. Some avian species undergo a type of disintegration and seasonal reconstruction of the testis and epididymis. The relationship of the ovarian follicular hormones and the plasma hormones varies depending on the stage of the reproductive cycle and the seasonal photostimulation. Female birds may conceive in the absence of a mate as a result of the fertile period phenomena. The blood chemistry of laying birds is different from that seen in nonlaying hens. Domestication has had a definite influence on the hormone cycles of some avian species. This may lead to certain reproductive problems.

Seasonal changes in gonadal steroids of a monogamous versus a polyandrous shorebird

We examined the relationship between circulating levels of gonadal steroids (testosterone, progesterone, and estradiol) and breeding behavior in semipalmated sandpipers (Calidris pusilla) and red-necked phalaropes (Phalaropus lobatus) breeding sympatrically at La Pérouse Bay, 40 km east of Churchill, Manitoba. Semipalmated sandpipers are territorial and monogamous. Both parents incubate equally. Red-necked phalaropes are nonterritorial and polyandrous. Only male phalaropes care for eggs and young. Gonadal steroid hormone profiles were not reversed in the sex-role-reversed species. There was little difference in testosterone profiles between males of the territorial and nonterritorial species.

Annual cycles of plasma gonadotropins and sex steroids in Japanese common pheasants, Phasianus colchicus versicolor

Plasma levels of FSH, LH, and sex steroid hormones were monitored individually in 5 male and 15 female Japanese common pheasants once to thrice monthly for 13 months. The birds were reared in outdoor cages, each containing 1 male and 5 females, under natural conditions of temperature and photoperiod. Around the period of egg laying from April 19 to July 6, plasma levels of FSH, LH, estradiol-17 beta (E2), and progesterone (P) in females were high. The increases in circulating FSH and E2 occurred earlier (in March) than those in LH and P (from April to May); decreased levels were observed first for LH in mid-June, second for P and E2 in late June, and last for FSH in June to August. Regression analysis revealed that the temporal course in titer of E2 is better rationalized as being dependent on the level of FSH rather than LH, whereas that of P is more dependent on LH than on FSH. In males, FSH was elevated only in March to June, whereas the temporal course of plasma levels of LH was clearly bimodal with maxima in February and in September. The titer of testosterone (T) was high in March to June, coinciding approximately with the maximum level of FSH. FSH was positively correlated with T, whereas LH was not in a simple correlation analysis. However, multiple-correlation analysis revealed that the change in T was better explained by considering the influence of both FSH and LH.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal changes in prolactin and luteinizing hormone in the polyandrous spotted sandpiper, Actitis macularia

The polyandrous spotted sandpiper (Actitis macularia) is a species characterized by female dominance over males and predominant male parental care. Prolactin (Prl) and luteinizing hormone (LH) were analyzed in plasma samples obtained serially from individuals across different stages of the breeding season. The reproductive status of each sampled individual was known in detail. Similar Prl values were obtained independently by two different assays. Males tended to have higher plasma Prl levels than females throughout the breeding season. Prl was significantly elevated in both sexes by the first few days of incubation. This rapid rise in Prl may indicate its role in brood patch development and the onset of incubation behavior. In males Prl continued to rise during incubation, whereas it remained constant in females. Higher levels of Prl in males than females, especially late in incubation, reflects the greater contribution of males to incubation. LH declined markedly in males and females from prelaying to early incubation. There was a significant negative correlation between Prl and LH among males, especially from the prelaying to early incubation phases of the season. There was no such correlation among females.

Seasonal variation in pituitary responsiveness to luteinizing hormone-releasing hormone of mallards and canvasbacks

Endocrine profiles of wild mallards (Anas platyrhynchos) and canvasbacks (Aythya valisineria) were determined during the spring and the summer. Males and females of each species were treated with a single intravenous injection of 12 micrograms of synthetic luteinizing hormone-releasing hormone (LHRH). Preinjection and postinjection blood samples were collected and LH levels were determined by radioimmunoassay. LHRH evoked a brisk and significant elevation in serum LH in all ducks indicating the pituitary glands of both species contain readily releasable pools of LH. In March, the preinjection baseline levels of LH in the two groups did not differ. However, mallards responded to LHRH with a twofold increase in serum LH, while canvasbacks responded with a fourfold increase (F = 17.1, P less than 0.001). At the summer blood sampling period, mallards had significantly higher circulating levels of serum LH than canvasbacks (F = 35.9, P less than 0.001). Both species responded to LHRH with a twofold increase in circulating LH. These data indicate that seasonal variations in reproduction shown by the two species in captivity may be associated with differences in LHRH-sensitive pools of LH.

Serum levels of luteinizing hormone (LH), prolactin, estradiol, and progesterone in laying and nonlaying canvasback ducks (Aythya valisineria)

Temporal changes in the levels of serum luteinizing hormone (LH), prolactin, estradiol, and progesterone associated with the reproductive patterns of 53 wild captive canvasback ducks were measured. The reproductive endocrinology of both laying and nonlaying females was compared in this 3-year study. Females that remained sexually inactive had ovaries with small, undeveloped follicles. Nonlaying ducks also had lower serum levels of LH (P less than 0.01), prolactin (P less than 0.05), estradiol, and progesterone than those of laying ducks in mid-April (during prelay), mid-May (on the fourth day of egg production), and mid-June (during postlay and incubation). Prolactin levels of both layers and nonlayers increased over this time interval (P less than 0.01) but levels of nonlayers were significantly lower than those of layers for the three blood-sampling dates. The low prolactin levels demonstrate that reproductive failure was not a result of inhibition by high serum prolactin levels. Intravenous injections of luteinizing hormone-releasing hormone (LHRH) in female canvasbacks resulted in significantly elevated (P less than 0.01) serum LH on the prelay blood sampling date. Lack of reproduction in nonbreeding canvasbacks was thus associated with low circulating serum LH levels but with LHRH-sensitive pituitary pools. These data suggest that lack of reproduction was a result of the failure of the hypothalamus to release releasing factors. The serum hormones of laying canvasbacks varied temporally with stages of the nesting cycle. LH levels increased prior to egg laying and fluctuated during the laying period. LH levels decreased at the onset of incubation but increased after loss of clutch, with renesting activity. Serum prolactin levels of layers were low prior to egg laying and increased gradually through laying of the first clutch, the renesting period, and laying of the second clutch. The highest prolactin levels occurred in ducks incubating their eggs. Prolactin levels decreased in ducks that failed to incubate their eggs. Serum estradiol levels increased sharply between 2 and 5 weeks prior to egg laying and remained high until the second day of egg production. Estradiol levels decreased when the fourth egg was produced, and remained low through the laying of the first clutch, the renesting period, and laying of the second clutch. Progesterone fluctuated widely through the nesting cycle, showing several major peaks before laying and another during incubation.

Time relationships between oviposition, ovulation and egg formation in Khaki Campbell ducks

1. Ten-month-old Khaki Campbell ducks were killed between 5 min and 15 h after oviposition. Time of oviposition and interval between eggs were recorded prior to killing. 2. Oviposition generally occurred between 04.00 and 06.00 h, 7 to 9 h after the onset of the dark period the previous day. Ninety-seven percent of eggs were laid by 07.00 h. 3. The mean +/- SD time interval between consecutive ovipositions was 24.0 +/- 0.3 h, with a range from 23.5 to 24.5 h. 4. It was estimated that ovulation occurred on average 10 min after oviposition, and the ovum spent 15 to 30 min in the infundibulum, 2.5 to 3 h in the magnum, 2 to 2.5 h in the isthmus and 18.6 h in the shell gland.

Influence of ingested petroleum on the reproductive performance and pituitary-gonadal axis of domestic ducks (Anas platyrhynchols)

1. The chronic ingestion of a sublethal dose (5%) of dietary North Sea crude oil delayed the onset of lay in adult Khaki Campbell ducks transferred from a short (8L:16D) to long day (16L:8D) photoperiod and greatly reduced the rate of oviposition and quality (weight and shell thickness) of the eggs subsequently laid. 2. Refeeding the oil-fed birds with the uncontaminated control diet stimulated the rate of egg production and improved egg quality, but in both cases not to the level in the controls. 3. Food intake and the plasma calcium level in the petroleum-fed birds were reduced, but these effects are unlikely to be causally responsible for the adverse effects of petroleum on avian reproduction. 4. Gonadotrophic (luteinizing hormone, LH) hormone secretion in the oil fed birds was not suppressed and the impairment of reproductive performance was not due to low plasma LH levels. 5. The reduced rate of lay in the oil-fed birds was accompanied by low gonadal steroid (progesterone) levels. The detrimental effects of oil and reproduction may be due to direct or indirect effects on the ovary or shell gland.