Plasma gonadotropins and ovarian hormones during the estrous cycle in high compared to low ovulation rate gilts

Mature gilts classified by low (12 to 16 corpora lutea [CL], n = 6) or high (17 to 26 CL, n = 5) ovulation rate (OR) were compared for plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, estradiol-17beta, and inhibin during an estrous cycle. Gilts were checked for estrus at 8-h intervals beginning on d 18. Blood samples were collected at 8-h intervals beginning on d 18 of the third estrous cycle and continued for one complete estrous cycle. Analysis for FSH and LH was performed on samples collected at 8-h intervals and for ovarian hormones on samples collected at 24-h intervals. The data were standardized to the peak of LH at fourth (d 0) and fifth estrus for the follicular phase and analyzed in discrete periods during the periovulatory (-1, 0, +1 d relative to LH peak), early-luteal (d 1 to 5), mid-luteal (d 6 to 10), late-luteal (11 to 15), periluteolytic (-1, 0, +1 d relative to progesterone decline), and follicular (5 d prior to fifth estrus) phases of the estrous cycle. The number of CL during the sampling estrous cycle was greater (P < 0.005) for the high vs low OR gilts (18.8 vs 14.3) and again (P < 0.001) in the cycle subsequent to hormone measurement (20.9 vs 14.7). For high-OR gilts, FSH was greater during the ovulatory period (P = 0.002), the mid- (P < 0.05) and late-luteal phases (P = 0.01), and tended to be elevated during the early-luteal (P = 0.06), but not the luteolytic or follicular periods. LH was greater in high-OR gilts during the ovulatory period (P < 0.005), but not at other periods during the cycle. In high-OR gilts, progesterone was greater in the mid, late, and ovulatory phases (P < 0.005), but not in the follicular, ovulatory, and early-luteal phases. Concentrations of estradiol-17beta were not different between OR groups during the cycle. Inhibin was greater for the high OR group (P < 0.005) during the early, mid, late, luteolytic, and follicular phases (P < 0.001). The duration of the follicular phase (from last baseline estrogen value to the LH peak) was 6.5 +/- 0.5 d and was not affected by OR group. These results indicate that elevated concentrations of both FSH and LH are associated with increased ovulation rate during the ovulatory phase, but that only elevated FSH during much of the luteal phase is associated with increased ovulation rate. Of the ovarian hormones, both inhibin and progesterone are highly related to greater ovulation rates. These findings could aid in understanding how ovulation rate is controlled in pigs.     

Expression of steroidogenic enzymes and synthesis of steroid hormones during development of ovarian follicles in prepubertal goats

Expression of mRNAs encoding cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17 -hydroxylase (P450c17), and cytochrome P450 aromatase (P450arom) were characterized by the RT-PCR technique and concentrations of progesterone (P4), testosterone (T0) and estradiol (E2) were measured by radioimmunoassay during follicular development of prepubertal goats. Synthesis of mRNAs encoding P450scc and P450c17 began in preantral follicles, but mRNA encoding P450arom was not detectable until early antral formation. While mRNA for P450scc was expressed in both theca and granulosa cells, mRNA for P450c17 was expressed only in theca cells while P450arom mRNA only in granulosa cells. In nonatretic follicles from prepubertal ovaries, the relative quantity of mRNA expression of all the three enzymes increased with follicle size; however, while the concentration of P4 and E2 increased, that of T0 decreased with follicle size. While expression of mRNA encoding P450scc was unaffected, that of P450c17 mRNA decreased to the lowest level and mRNA for P450arom became undetectable following atresia; accordingly, while the concentration of P4 increased in the atretic medium follicles, that of T0 and E2 decreased to the lowest level after atresia. While the adult follicular stage follicles showed a similar cytochrome expression as the nonatretic follicles of prepubertal goats, the former contained higher levels of E2 and P4 than the latter. The presence of corpus luteum in an ovary decreased expression of P450scc, significantly in large follicles while it increased concentration of P4. These findings indicated that (1) similar to other species, changes in follicular steroid production in goats were explained in large measure by changes in steroidogenic enzyme expression; (2) while mRNA expression was similar, activities of some of the steroidogenic enzymes may differ between sexually mature and immature goats.     

Effect of the gonadotrophins treatment on morphological alterations in ovary and peripheral plasma concentrations of steroid hormones in gilts

The present study was designed to examine the influence of gonadotrophins treatment on the ovarian morphology changes and plasma concentrations of steroid hormones in peripheral blood. The experiment was performed on sexually pubertal gilts (Large White x Landrace) of similar age (7-8 months) and body mass (100-110 kg) with two controlled subsequent estrous cycles. The animals were randomly divided into four groups: two control consisting of pigs with the luteal phase (n = 9, the 10th day of the estrous cycle) and the follicular phase (n = 6, the 20th day of the estrous cycle) and two experimental ones consisting of animals with both mentioned periods (n = 7 and n = 9) treated with gonadotrophins (PMSG and hCG). The gilts in the luteal phase were injected (s.c.) with gonadotrophins at a daily dose of PMSG 400 and hCG 200 IU from the 16th to the 27th day (the 6th day of the next estrous cycle). The gilts in the follicular phase, were injected with the same dose of gonadotrophins but from the 8th to the 19th day of the estrous cycle. Plasma concentrations of P4, A4, T, E1, E2 and metabolite of PGF2 alpha-PGFM were determined by radioimmunoassay (RIA) method. Injections of PMSG and hCG in both experimental groups produced several times enlarged: weight, size and volume of ovaries and alterations in a number of structural elements as compared with those found in the control animals. The morphological elements presented in ovaries: corpora haemorrhagica, corpora lutea, regular and atretic follicles and first of all cysts by distinctly differentiation thickness of the walls are characteristic for cystic ovarian degeneration. Plasma concentrations all determined hormones after gonadotrophins treatment in experimental groups were increased except E1 (insignificant decrease) in luteal phase as compared with those found in the control groups. Statistically significant increase (p < 0.001) in plasma concentrations of P4, A4, and T in both experimental groups and E2 (p < 0.001) in luteal phase were noted. In peripheral plasma concentrations increase of E1 and E2 in follicular phase of the estrous cycle were insignificant.     

Opsonic activity in mammary secretion and serum of gilts during the lactation period.

Opsonic activity was studied in mammary secretion and serum during lactation in four healthy gilts. The opsonic activity was determined as peak chemiluminescence and time to peak chemiluminescence in a luminol enhanced chemiluminescence assay. The peak chemiluminescence was significantly (p less than 0.05) higher in mammary secretion around parturition than later in lactation. No changes in the opsonic activity were seen in serum during lactation. Overall, the peak chemiluminescence and time to peak chemiluminescence were significantly higher (p less than 0.001) and shorter (p less than 0.05) respectively, in serum than in mammary secretion. The present study indicates that the opsonic activity is highest in mammary secretion around parturition but decreases later in lactation, and that this change is confined to the mammary gland.     

Pubertal changes in the secretion of gonadotropic hormones, testicular gonadotropic receptors and testicular function in the ram

Developmental changes in pituitary content and secretory patterns of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL), testicular size and steroidogenic function, testicular LH- and FSH-binding activity, and growth of the accessory sex organs were examined for 24 Dorset X Leicester X Suffolk rams (born in March) every 30 days from 30 to 150 days of age, and again at 200 days. Pituitary LH and FSH contents increased between 30 and 60 days of age and remained constant until 150 days, when contents were somewhat greater than on either 120 or 200 days. LH-pulse amplitude and frequency, and mean FSH concentration, were highest at 60 and (or) 90 days of age. Testicular growth increased dramatically between 90 and 150 days of age in association with increases in the number of LH- (100-fold) and FSH- (33-fold) binding sites in the testis and a small increase in blood testosterone concentration (1 ng/ml). During the same period, pituitary content and blood concentration of PRL increased to maximal values, epididymal, vesicular gland and bulbourethral gland weights increased 6-fold, and body weight doubled. Between 150 and 200 days of age, testosterone concentration increased considerably (8 ng/ml), as did LH-pulse frequency and the amount of LH- and FSH- binding in the testis; the reproductive organs continued to grow at a rate faster than that of the body as a whole. Testicular development of ram lambs was accompanied by increases in the secretion of all three pituitary hormones with gonadotropic properties, and in the number of LH and FSH receptors.     

Feasibility of detecting steroid hormones in cattle feces for monitoring ovarian function

Faecal material from four non pregnant cows was withdrawn in two-day intervalls during a four-week period. At the same time bloodsamples were taken to monitor the ovarian function. Clinical and ultrasonographical examinations were recorded in parallel. To look for the stability of the faecal steroid analogues for P4 (Progesterone) and E2 (Estradiol-17 beta) faecal material was stored at 37 degrees C and samples from that analyzed in two-day intervals. The P4 (Progesterone)-analogues values in the faeces showed good correlation to cycling ovarian functions as monitored by bloodlevels from P4, clinical examination and ultrasonography. In contrast the E2-analogues values showed no cycling pattern. One cow however showed ovarian cysts which was monitored in the P4 values for blood and faeces. Concerning the stability of the steroid analogues it could be demonstrated that the P4-values show a steady decrease with minimum values of 20 ng/g dry material. During the first four days after sampling reliable values for clinical interpretations can be found. The concentrations for E2 are very inconstant and so far not of interest. The investigation shows that the faecal steroid P4 can be used for monitoring ovarian function. It has to be analyzed within four days after sampling when stored at room temperature.     

In situ hybridization analysis of ovarian prostaglandin endoperoxide synthase mRNA throughout the periovulatory period of the ewe.

Cellular alterations in level of expression of mRNA encoding for prostaglandin endoperoxide synthase were quantified within ovarian tissues of sheep obtained before, during and after induction of the preovulatory surge of LH and ovulation with LHRH. This was accomplished by isotopic in situ hybridization using a selective cRNA probe to ovine prostaglandin endoperoxide synthase mRNA. A significant elevation in mRNA was detected within the theca interna of the preovulatory follicle at 8, 16 and 24 hr following administration of LHRH. Very close to the time of ovulation (ie., at 24 hr post-LHRH) a marked rise in mRNA was observed in association with epithelial cells covering the apical surface of the follicle. Ovarian cyclooxygenase metabolites of arachidonic acid produced during the ovulatory process in the ewe originate within the thecal layer and germinal epithelium of the follicle destined to ovulate.     

Dynamics of changes in the cytological picture of vaginal smears and circulating ovarian hormones during the puerperal period in ewes]

A postparturient period is characterized by low basal secretion of adenohypophysis gonadotropins with the following appropriate changes in ovarian hormones and their response to the morphology of vaginal epithelium. In this study the dynamics of the cytological picture of vaginal swabs and ovarian hormones 17 beta-oestradiol (E2) and progesterone was investigated in the puerpery of ewes. The objective was to obtain and extend the knowledge of cytological changes in vaginal epithelium and levels of ovarian hormones of ewes after parturition and of their relationships from the first several days after lambing until the 51st day of the period of observation. Vaginal swabs for vaginal cytology were taken from nine ewes on days 1, 4, 7, 14, 17, 21, 25, 34, 42 and 51 after parturition. These swabs were fixed in ether-alcohol 1:1, stained according to the Faltínová-Zidovsky method, embedded in Canada balsam and evaluated by differentiation of cells according to Luksh (1953). Blood samples for E2 and P4 determinations were taken from the jugular vein in the same intervals as vaginal swabs. The serum was centrifuged and stored at -18 degrees C until use. E2 and P4 concentrations were determined radioimmunologically, using kits RIA-test ESTRA and RIA-test PROG from URVJT Kosice. A statistically significant decline (P < 0.05) of percentual representation of basal and parabasal cells (Fig. 1, Tab. I) on day 7 after lambing was replaced by their multiplication from day 14 reaching the values of 66.07 +/- 3.95 on day 42. A statistically significant decrease in intermediary flat cells (Fig. 2, Tab. II) was observed on days 14 (P < 0.001), 34 and 42 (P < 0.01; P < 0.001), in comparison with the first day after lambing. An evaluation of intermediary convoluted cells revealed their highest percentage on days 1 and 17 after parturition (34.65 +/- 4.77-20.62 +/- 12.57) and their decline to values in the range of 6.77 +/- 1.46-7.66 +/- 2.25 on the remaining days of the period of observation. Percent occurrence of superficial flat cells (Fig. 3, Tab. I) ranged from 3.9 +/- 1.10 to 10.63 +/- 7.23 from day 1 to day 51 after lambing. The lowest percentual representation (1.32 +/- 0.79-4.10 +/- 1.89) was recorded for superficial convoluted cells. Multiplication of the evaluated cells was observed, reaching the highest but insignificant representation (P > 0.05) on day 25 of postparturient investigation: 4.10 +/- 1.89 (Fig. 3, Tab. I). 17 beta-oestradiol (E2) concentrations were compared to the -1st day before parturition, when its values varied at the level of 2.45 +/- 0.64 nmol/l serum.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characterization of ovarian morphology and reproductive hormones in Zhedong white geese (Anser cygnoides domesticus) during the reproductive cycle

Zhedong white goose (Anser cygnoides domesticus) is a native Chinese breed with strong broodiness and low egg production, which is related to the physiology of reproduction. However, thus far, the physiology of goose reproduction has not been well elucidated. In the present study, the ovarian morphology and reproductive hormones of Zhedong white geese were investigated during the reproductive cycle (the laying and brooding periods). The results showed that the surface of the ovary was atrophied and follicular atresia appeared to some extent in the brooding period compared with the laying period. The concentrations of follicle-stimulating hormone, progesterone and luteinizing hormone were significantly higher than those in the brooding period (p < 0.05). In contrast, the concentrations of prolactin (PRL) and anti-Müllerian hormone (AMH) in the laying period were significantly lower than those in the brooding period (p < 0.05). In addition, the mRNA expression levels of PRL, AMH, dopamine-β-hydroxylase (DβH) and cytochrome P450 side-chain cleavage enzyme (P450scc) were detected in the hypothalamus, pituitary and ovaries by using real-time polymerase chain reaction. The results showed that AMH mRNA was expressed specifically in ovary tissue. The expression levels of DβH and PRL in the brooding period was significantly higher than those in the laying period in the three tissues, especially in the early and middle stages of the brooding period. Moreover, AMH mRNA expression in the ovaries presented the same trend. In addition, P450scc mRNA was highly expressed in both the ovary and pituitary in the laying period. These results revealed the remarkable features of ovarian morphology and characterized the hormonal pattern and expression profile during the reproductive cycle, all of which contribute to understanding the differences in reproductive physiology between the laying and brooding periods in Zhedong white geese.     

Comparison of luteinizing hormone and steroid hormone secretion during the peri- and post-ovulatory periods in Mangalica and Landrace gilts

The objective of this study was to determine plasma concentrations of luteinizing hormone (LH), progesterone (P4) and estradiol-17beta (E2) in Mangalica gilts (M), a Hungarian native breed, and compare them with Landrace gilts (L) during the peri- and post-ovulatory periods. The estrous cycle of gilts was synchronised by Regumate feeding, and ovulation was induced with a gonadotropin-releasing hormone (GnRH) agonist. Blood sampling was carried out via indwelling jugular catheters three times a day and in 2-h intervals during a 16-h period after the GnRH application. The concentrations of LH, E2 and P4 were determined by immunoassays. Gilts of both breeds showed a typical gonadotropin and gonadal hormone secretion pattern. Preovulatory E2 peaks were observed on day 2 (M) and day 4 (L) after the last Regumate feeding. Highest E2 concentration was different between M and L breeds (46.5 +/- 5.7 vs. 26.0 +/- 6.8 pg/ml, P < 0.05). Maximum LH levels measured up to 6 h after GnRH were not different between M and L breeds (11.5 +/- 4.1 vs. 6.6 +/- 2.3 ng/ml). Both LH amounts during surge (41.1 +/- 15.9 vs. 27.5 +/- 6.1 ng/ml) and total over LH release (73.4 +/- 22.2 vs. 50.0 +/- 8.7 ng/ml) did not differ significantly between M and L breeds. P4 concentrations started to rise on day 6 after Regumate feeding and increased significantly from 0.6 +/- 0.3 and 0.7 +/- 0.4 ng/ml to maximal 14.0 +/- 2.4 and 11.3 +/- 2.1 ng/ml in M and L breeds, respectively. Mean P4 secretion was higher in M on days 10-15 (12.9 +/- 2.6 vs. 9.3 +/- 2.2 ng/ml; P<0.05). At the same time the number of corpora lutea was lower in M compared to L (10.3 +/-1.5 vs. 17.8 +/- 5.0, P<0.05). In our experiment, there was no evidence that differences in the secretion of analysed hormones during the peri- and post-ovulatory periods are a possible cause of usually lower fecundity in Mangalica gilts.     

Effect of carazolol on the oestrous behaviour and concentrations of luteinising hormone and steroids in lactating cows during the periovulatory period

Twelve multiparous, cycling, lactating Holstein-Friesian cows were synchronised with prostaglandin F(2alpha) and treated with either 2.5 mg carazolol or saline. There were no differences between the peripheral blood concentrations of oestradiol or progesterone, but in the cows treated with carazolol the periovulatory surge of luteinising hormone was delayed, and oestrous behaviour was expressed later than in the control cows.     

The effect of steroid hormone doses after ovariectomy on the peripheral hormone processes and uterine development in gilts. 2. Effects on gilts during early pregnancy

Experimental studies were conducted into ovariectomized pregnant gilts to establish effects of exogenic hormone administration, with endogenic ovarian steroids excluded, upon uterus and fetus development as well as on hormone levels in blood plasma, endometrium, and allantoic fluid. Hormone concentrations in blood plasma were found to depend clearly on hormone doses applied after ovariectomy to preserve pregnancy. 2 to 3 weeks of smooth gravidity, following ovariectomy, were ensured on the 6th or 14th day after KB1 by daily application of very low doses of progesterone only (80 mg) or in combination with estrogens, the ratio being 480:1.     

Role of glial cells,growth factors and steroid hormones in the control of LHRH-secreting neurons

The mechanisms through which steroid hormones influence the LHRH system are not completely clarified and still represent a crucial and debated field of research in the neuroendocrine control of reproduction. Several data indicate that glial cells influence the activity of hypothalamic LHRH-secreting neurons, via the release of growth factors. It is now well known that glial cells express different kinds of steroid receptors and consequently may be considered as a target for the action of steroid hormones. To this purpose, the possibility that the effects of steroid hormones on LHRH neurons may be mediated by glial elements has been taken in consideration and observations supporting this hypothesis have been reported and discussed here. The results so far obtained strongly suggest that steroid hormones and growth factors, in order to exert their modulatory actions on LHRH dynamic, act in an integrated manner at the level of hypothalamic astrocytes.     

Beneficial effects of a decreased meal frequency on nutrient utilization,secretion of luteinizing hormones and ovarian follicular development in gilts

Background: Replacement gilts are typically fed ad libitum, whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits. The objective of this study was to investigate the effect of meal frequency on the metabolic status and ovarian follicular development in gilts.Methods: A total of 36 gilts(Landrace × Yorkshire) with an age of 150±3 d and a body weight of 77.6±3.8 kg were randomly allocated into one of three groups(n = 12 in each group), and based on the group allocation, the gilts were fed at a frequency of one meal(T1), two meals(T2), or six meals per day(T6) for 14 consecutive weeks. The effects of the meal frequency on growth preference, nutrient utilization, short-chain fatty acid production by gut microbial, the post-meal dynamics in the metabolic status, reproductive hormone secretions, and ovarian follicular development in the gilts were measured.Results: The gilts in the T1 group presented a higher average daily gain(+ 48 g/d, P 0.05) and a higher body weight(+ 4.9 kg, P 0.05) than those in the T6 group. The meal frequency had no effect on the apparent digestibility of dry matter, crude protein, ether extract, ash, and gross energy, with the exception that the T1 gilts exhibited a greater NDF digestibility than the T6 gilts(P 0.05). The nitrogen balance analysis revealed that the T1 gilts presented decreased urine excretion of nitrogen(-8.17 g/d, P 0.05) and higher nitrogen retention(+ 9.81 g/d, P 0.05), and thus exhibited higher nitrogen utilization than the T6 gilts. The time-course dynamics of glucose, α-amino nitrogen, urea, lactate, and insulin levels in serum revealed that the T1 group exhibited higher utilization of nutrients after a meal than the T2 or T6 gilts. The T1 gilts also had a higher acetate content and SCFAs in feces than the T6 gilts(P 0.05). The age, body weight and backfat thickness of the gilts at first estrous expression were not affected by the meal frequency, but the gilts in the T1 group had higher levels of serum luteinizing hormone on the 18 th day of the 3 rd estrus cycle and 17β-estradiol, a larger number of growing follicles and corpora lutea, and higher mRNA expression levels of genes related to follicular development on the 19 th day of the 3 rd estrus cycle.Conclusions: The current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts, and thus provide new insights into the nutritional strategy for replacement gilts, and the dietary pattern for other mammals, such as humans.     

Characterization of immunoreactive IGF-I pattern during the peri-ovulatory period of the oestrous cycle of thoroughbred mares and its relation to other hormones

The aim of this study was to characterize ir-IGF-I pattern and its relation to other hormones during the oestrous cycle in mares. Nine non-pregnant non-lactating pluriparous thoroughbred mares were used. The studied mares were examined ultrasonically and bled daily to follow the ovarian changes and the hormonal milieu for a complete Interovulatory interval (IOI). Two (minor and major) follicular waves were characterized per IOI in thoroughbred mares. The largest follicle of the first follicular wave (DF1) was firstly detected at D - 1.75 ± 0.47 with a growth rate of 2.78 ± 0.14mm/day and maximum diameter of 22.45 ± 0.75mm on day 6.65 ± 0.82. The largest follicle of the second follicular wave (DF2) had a growth rate of 2.15 ± 0.29 mm/day, reached a maximum diameter of 42.70 ± 2.63 mm on D 19.25 ± 0.43. Ir-IGF-I increased significantly prior to ovulation and had a similar pattern to oestrogen (r = 0.84, p < 0.05), suggesting that the ovarian follicles are the main source of circulating ir-IGF-I during the oestrous cycle of mares and that ir-IGF-I may be a crucial factor in follicular differentiation and maturation. In conclusion, this study demonstrated that ir-IGF-I is secreted during the oestrous phase of the cycle concomitant with the development of the future ovulatory dominant follicle, and it may act in synergy with other hormones for the selection and differentiation of the dominant follicle.     

Disease control during the colonial period in Australia

The first permanent European settlers of Australia arrived in 1788 to establish a penal colony at Sydney, New South Wales (NSW). As the colony grew and wool production increased, more free settlers and emancipists developed farming in inland Australia. During the 1840s veterinarians commenced arriving in small numbers but they were not closely associated with the development and execution of disease control programs, which was left to lay inspectors of stock. The arrival of William Tyson Kendall and coordinated action with Graham Mitchell led to the establishment of a private veterinary college following the passage of veterinary surgeons legislation in Victoria. From this time, veterinarians came to be appointed to positions formerly occupied by lay inspectors and the veterinary profession was able to take up the role of planning and executing government-led disease control programs. From a colony relying on wool for export to the UK, technical advancements in meat freezing and pasture improvement widened the range and increased the quantity of exported products. Before the advent of veterinary advances, sheep scab was eradicated, a vaccine was developed for anthrax and glanders infection of horses was prevented entry to Australia. Graduates from the Melbourne Veterinary College spread across Australia and in this period a conservative quarantine policy was developed following inaction to control an outbreak of contagious bovine pleuropneumonia (CBPP) and the escape of rabbits to form a plague across the continent. Coordinated control of CBPP had to await the next century and advancement of technology increased our understanding of bacteriology and immunity of infectious diseases. Veterinary services were provided to the militia sent by the colonies to the Boer Wars in South Africa 1987-1901 and the veterinarians from Victoria were led by an Australian trained veterinarian.