Effect of Blood Sampling and Administration of ACTH on Cortisol and Progesterone Levels in Ovariectomized Zebu Cows (Bos indicus)

Efficacy and Safety of Native and Recombinant Zona Pellucida Immunocontraceptive Vaccines Formulated with Non-Freund's Adjuvants in Donkeys

This study aimed to test zona pellucida (ZP) vaccines’ immunocontraceptive efficacy and safety when formulated with non-Freund’s adjuvant (6% Pet Gel A and 500 Μg Poly(I:C)). Twenty-four jennies were randomly assigned to three treatment groups: reZP (n = 7) received three doses of recombinant ZP vaccine; pZP (n = 9) received two doses of native porcine ZP; and Control group (n = 8) received two injections of placebo. Jennies were monitored weekly via transrectal ultrasonography and blood sampling for serum progesterone profiles and anti-pZP antibody titres. In addition, adverse effects were inspected after vaccination. Thirty-five days after the last treatment, jacks were introduced to each group and rotated every 28 days. Vaccination with both pZP and reZP was associated with ovarian shutdown in 44% (4/9) and 71% (4/7) of jennies, 118 ± 33 and 91 ± 20 days after vaccination, respectively (p > 0.05). Vaccination delayed the chances of a jenny becoming pregnant (p = 0.0005; Control, 78 ± 31 days; pZP, 218 ± 69 days; reZP, 244 ± 104 days). Anti-pZP antibody titres were elevated in all vaccinated jennies compared to Control jennies (p < 0.05). In addition, only mild local injection site reactions were observed in the jennies after treatment. In conclusion, ZP vaccines formulated with non-Freund’s adjuvant effectively controlled reproduction in jennies with only minor localised side effects.

Cow-level prevalence and risk factors for estrus detection inaccuracy in seasonal calving pasture-based dairy cows

High submission rates and pregnancies per AI are essential to ensure compact calving is achieved in seasonal calving pasture-based systems. Estrus detection inaccuracy (EDI) is one area that negatively impacts pregnancies per AI as it increases the inseminations per pregnancy with little probability of conception, while also having the potential to disrupt established pregnancies. The aims of this cross-sectional study were to provide cow-level estimates of EDI prevalence and determine cow-level risk factors for EDI in seasonal calving pasture-based systems. A total of 1071 milk samples were obtained from 984 cows on 19 farms in spring 2018 and analyzed by radioimmunoassay to determine the progesterone concentration at the time of artificial insemination. Based on a validation study on a subset of cows, an inaccurate estrus detection was described as a concentration of progesterone in foremilk of ≥3 ng/ml which corresponded to a composite milk progesterone value of 5 ng/ml. To investigate selected risk factors for EDI, we conducted statistical analyses using two multivariate logistic regression models, stratifying by insemination number (first versus repeat). The overall prevalence of EDI was 4.7% with a prevalence of 3.3% of EDI at first insemination and 14.1% at repeat insemination. Absence of a mounting abrasion (Adjusted odds ratio (AOR) = 3.0) was a significant risk factor for EDI on first insemination while abnormal preceding repeat interval (AOR = 9.5), the absence of an observed standing estrus (AOR = 12.5) and the absence of a mounting abrasion (AOR = 4.1) were significant risk factors for EDI on repeat insemination. The results indicate that cow-level estimated prevalence of EDI in a selection of pasture-based herds was low at first insemination but higher for repeat insemination. It confirms that certain cow-level risk factors existed for EDI, thus providing preliminary evidence for potential future investigation into the targeted use of on-farm progesterone assays in pasture-based herds.

Model-based exploration of the impact of glucose metabolism on the estrous cycle dynamics in dairy cows

BACKGROUND

Nutrition plays a crucial role in regulating reproductive hormones and follicular development in cattle. This is visible particularly during the time of negative energy balance at the onset of milk production after calving. Here, elongated periods of anovulation have been observed, resulting from alterations in luteinizing hormone concentrations, likely caused by lower glucose and insulin concentrations in the blood. The mechanisms that result in a reduced fertility are not completely understood, although a close relationship to the glucose-insulin metabolism is widely supported.

RESULTS

Following this idea, we developed a mathematical model of the hormonal network combining reproductive hormones and hormones that are coupled to the glucose compartments within the body of the cow. The model is built on ordinary differential equations and relies on previously introduced models on the bovine estrous cycle and the glucose-insulin dynamics. Necessary modifications and coupling mechanisms are thoroughly discussed. Depending on the composition and the amount of feed, in particular the glucose content in the dry matter, the model quantifies reproductive hormones and follicular development over time. Simulation results for different nutritional regimes in lactating and non-lactating dairy cows are examined and compared with experimental studies. The simulations describe realistically the effects of nutritional glucose supply on the ovulatory cycle of dairy cattle.

CONCLUSIONS

The mathematical model enables the user to explore the relationship between nutrition and reproduction by running simulations and performing parameter studies. Regarding its applicability, this work is an early attempt towards developing in silico feeding strategies and may eventually help to refine and reduce animal experiments.

REVIEWERS

This article was reviewed by John McNamara and Tin Pang (nominated by Martin Lercher).

Milk progesterone enzyme-linked immunosorbent assay as a tool to investigate ovarian cyclicity of water buffaloes in relation to body condition score and milk production

Background

Application of assisted reproductive technologies in buffaloes is limited to some extent by farmers’ inability to detect oestrus because of its poor expression. The present study aimed at investigating reliability of a milk progesterone enzyme-linked immunosorbent assay (ELISA) to assess the ovarian cyclicity during post partum, oestrus and post-breeding periods in water buffaloes.

Methods

Progesterone concentrations were measured by an ELISA in milk of 23 postpartum buffaloes in relation to oestrus, pregnancy, body condition score (BCS) and milk production. Two milk samples were taken at 10 days intervals, every month starting from day 30 and continued to day 150 post partum. BCS and milk production were recorded during sample collection. Milk samples from bred buffaloes were collected at Day 0 (day of breeding), Days 10–12 and Days 22–24. Defatted milk was preserved at −80°C until analysis. Pregnancy was confirmed by palpation per rectum on Days 70–90.

Results

Seventeen buffaloes had 47 ovulatory cycles, one to four in each, 13 were detected in oestrus once (28 % oestrus detection rate). Progesterone concentration ≥1 ng/ml in one of the two 10-day-interval milk samples reflected ovulation and corpus luteum formation. The intervals between calving to first luteal activity and to first detected oestrus varied from 41 to 123 days (n = 17) and 83 to 135 (n = 13) days, respectively. Eight buffaloes were bred in the course of the study and seven were found pregnant. These buffaloes had a progesterone profile of low (<1 ng/ml), high (≥ 1 ng/ml) and high (≥ 1 ng/ml) on Day 0, Days 10–12 and Days 22–24, respectively. Buffaloes cycling later in the postpartum period had fewer missed oestruses (P < 0.05). Buffaloes with a superior BCS had a shorter calving to oestrus interval and produced more milk (P < 0.05).

Conclusions

Milk progesterone ELISA is a reliable tool for monitoring ovarian cyclicity and good BCS may be an indicator of resuming cyclicity in water buffalo.

Low cortisol levels in blood from dairy cows with ketosis: a field study

BACKGROUND

An elevated plasma glucose concentration has been considered to be a potential risk factor in the pathogenesis of left-displaced abomasums (DA). Therefore the present study was performed to investigate if spontaneous disease (parturient paresis, metritis, ketosis etc) in dairy cows results in elevated concentrations of glucose and cortisol in blood as cortisol is the major regulator of glucose in ruminants.

METHODS

Cortisol, insulin, beta-hydroxybutyric acid (BHBA), non esterified fatty acids (NEFA), and serum calcium were analyzed in blood serum and glucose, in whole blood, from 57 spontaneously diseased cows collected at different farms. The cows were grouped according to the disease; parturient paresis, recumbent for other reasons, mastitis, metritis, ketosis, inappetance and others.

RESULTS

No elevated concentrations of cortisol or glucose were found in cows with metritis and mastitis but both cortisol and glucose were elevated in cows stressed by recumbency. Cows with ketonemia (BHBA > 1.5 mmol/l) did not have low concentration of glucose in blood but significantly low levels of cortisol. Some of these cows even had cortisol concentrations below the detection limit of the analysing method (< 14 nmol/l).

CONCLUSIONS

The study gives patho-physiological support to the treatment strategies of ketosis, recommending glucocorticoids, insulin etc. However further studies of this problem are needed to understand why cows with ketosis have low levels of cortisol and normal levels of glucose. To what extent elevated cortisol and glucose levels in hypocalcemic and recumbent cows are involved in the ethiology and /or the pathogenesis of DA also will need further research.

Effects of continuous elevated cortisol concentrations during oestrus on concentrations and patterns of progesterone, oestradiol and LH in the sow

This study investigated the effect of continuous elevated cortisol concentrations during standing oestrus on time of ovulation and patterns of progesterone, oestradiol and luteinising hormone (LH) in sows. The elevation of cortisol concentrations was achieved through repeated intravenous injections of synthetic adrenocorticotropic hormone (ACTH) every 2 h for approximately 48 h, from the onset of the second standing oestrus after weaning. Treatment was terminated when ovulation was detected (monitored by transrectal ultrasonography every 4h) or when the sow had received a maximum of 24 injections. The dose of ACTH (2.5 microg/kg) was chosen to mimic the cortisol concentrations seen during mixing of unfamiliar sows. The sows (n=14) were surgically fitted with jugular vein catheters and randomly divided into a control (C group where only NaCl solution were injected) or an ACTH group. Blood samples were collected every 2 h. In parallel with the blood sampling, saliva samples for cortisol analyses were taken from eight sows before onset of treatment and from four of the sows during treatment. There was no difference in time from onset of standing oestrus to ovulation between the two groups. The interval between the peaks of oestradiol and LH to ovulation was prolonged in the ACTH group compared to the C group (p<0.05), with a tendency towards an earlier decline of oestradiol in the ACTH group. Cortisol and progesterone concentrations were significantly elevated during treatment in the ACTH group (p<0.001), with cortisol peak concentrations occurring between 40 and 80 min after each ACTH injection. Cortisol concentrations in saliva and plasma were highly correlated (p<0.001). In conclusion, elevated cortisol concentrations from the onset of standing oestrus increase progesterone concentrations and prolong the interval between oestradiol and LH peaks to ovulation, the latter possible due to an early decline in oestradiol concentrations and a change of the LH peak outline. The effect these hormonal changes have on reproductive performance need to be further investigated. Saliva samples might be a useful and non-invasive method to assess cortisol concentrations in sows.

Response to GnRH on day 6 of the estrous cycle is diminished as the percentage of Bos indicus breeding increases in Angus, Brangus, and Brahman×Angus heifers

Angus (n=6), Brangus (5/8 Angus x 3/8 Brahman, n=6), and Brahman x Angus (3/8 Angus x 5/8 Brahman, n=6) heifers exhibiting estrous cycles at regular intervals were used to determine if the percentage of Bos indicus breeding influenced the secretory patterns of LH in response to a GnRH treatment on Day 6 of the estrous cycle. Heifers were pre-synchronized with a two-injection PGF(2 alpha) protocol (25 mg i.m. Day -14 and 12.5 mg i.m. Day -3 and -2 of experiment). Heifers received 100 microg GnRH i.m. on Day 6 of the subsequent estrous cycle. Blood samples were collected at -60, -30, and -1 min before GnRH and 15, 30, 60, 90, 120, 150, 180, 240, 300, 360, 420, and 480 min after GnRH to determine concentrations of serum LH. Estradiol concentrations were determined at -60, -30, and -1 min before GnRH. On Day 6 and 8, ovaries were examined by ultrasonography to determine if ovulation occurred. On Day 13, heifers received 25 mg PGF(2 alpha) i.m. and blood samples were collected daily until either the expression of estrus or Day 20 for heifers not exhibiting estrus to determine progesterone concentrations. There was no effect (P>0.10) of breed on ovulation rate to GnRH as well as size of the largest follicle, mean estradiol, and mean corpus luteum volume at GnRH. Mean LH was greater (P<0.05) for Angus (7.0+/-0.8 ng/mL) compared to Brangus (4.6+/-0.8 ng/mL) and Brahman x Angus (2.9+/-0.8 ng/mL), which were similar (P>0.10). Mean LH peak-height was similar (P>0.10) for Brangus (13.9+/-3.4 ng/mL) compared to Angus (21.9+/-3.4 ng/mL) and Brahman x Angus (8.0+/-3.4 ng/mL), but was greater (P<0.05) for Angus compared to Brahman x Angus. Interval from GnRH to LH peak was similar (P>0.10) between breeds. As the percentage of Bos indicus breeding increased the amount of LH released in response to GnRH on Day 6 of the estrous cycle decreased.

Effects of exogenous ACTH during oestrus on early embryo development and oviductal transport in the sow

This study was conducted to assess the effects of ACTH injections on the early development of embryos and their transportation to the uterus. Fifteen sows were monitored for ovulation using transrectal ultrasonography during the first two oestrous periods after weaning. The sows were randomly divided into a control group (C group, n = 8) and an ACTH-treated group (ACTH group, n = 7), and were all surgically fitted with intra-jugular catheters. From the onset of the second standing oestrus after weaning, the sows were injected (NaCl/synthetic ACTH) every 4 h. Blood samples were collected immediately before and 45 min after each injection. All sows were inseminated once 10-33 h before ovulation in their second oestrus after weaning. At 48 (n = 4) or 60 (n = 11) h after ovulation during their second oestrus, the sows were killed and the embryos retrieved from the oviduct and uterus. The embryos were counted and compared with the number of corpora lutea, cleavage rate was noted and, finally, the embryos were prepared for confocal laser scanning microscopy and transmission electron microscopy. There was no difference between the groups regarding cleavage rate, the cytoskeleton, or the number of active nucleoli. However, the ACTH group had significantly (p < 0.05) fewer ova/embryos retrieved (51%) than the C group (81%), and there was a tendency towards faster transportation to the uterus in the ACTH group, possibly because of high progesterone concentrations during treatment. To conclude, administration of ACTH every 4 h from onset of oestrus to 48 h caused significant loss of oocytes or embryos, and possibly faster transportation through the oviduct.

ACTH stimulation in four Asian bull elephants (Elephas maximus): an investigation of androgen sources in bull elephants

The phenomenon of musth is a very stressful event, both behaviorally and physiologically. An ACTH stimulation test was conducted in four adult Asian bull elephants to investigate the possibility that the classical hypothalamic-pituitary-adrenal (HPA) axis is active during musth, resulting in an increase in adrenally produced steroids. Serum cortisol, testosterone (T), androstenedione (A4), androstenediol (A5), and dehydroepiandrosterone (DHEA) were measured. Cortisol increased 3-10 times above baseline in response to ACTH stimulation, and DHEA doubled. A4 and A5 were erratic, while testosterone decreased significantly in all bulls. The pattern of results suggests that the adrenal steroid increase which occurs during musth results from some mechanism other than the classical HPA axis.

Effects of ACTH injections during estrus on concentrations and patterns of progesterone, estradiol, LH, and inhibin alpha and time of ovulation in the sow

This study investigated whether injections of ACTH for 48 h, from the onset of the second standing estrus after weaning, had any impact on time of ovulation and patterns of progesterone, estradiol, luteinizing hormone (LH), and inhibin alpha. The studied sows (n=15) were fitted with jugular vein catheters and randomly divided into a control (C group) and an ACTH group. From the onset of standing estrus, the sows were injected (NaCl or synthetic ACTH, 5 microg/kg) every 4h; blood samples were collected immediately before and 45 min after each injection. Ovulation was monitored using ultrasonography. The ACTH-group sows stopped displaying signs of standing estrus sooner after ovulation in their second estrus, but no impact was found on time of ovulation. There were no significant differences in the intervals between LH peak, estradiol peak, and the onset of standing estrus between the C and ACTH groups. The cortisol and progesterone concentrations were significantly elevated (p<0.001) in samples taken 45 min after ACTH injection. There were minor differences in estradiol and LH concentrations between the groups. Overall inhibin alpha concentrations were significantly higher during the treatment period in the ACTH than in the C group, but there were no significant differences between samples taken either 45 min or 4h after injection. In conclusion, injections of synthetic ACTH during estrus in the sow apparently disturb the duration of signs of standing estrus and the hormonal pattern of progesterone, and possibly of inhibin alpha, estradiol and LH.

Plasma hormones in neotropical and domestic cats undergoing routine manipulations

Many neotropical felines are threatened with extinction and information on their physiology is required to assist in conservation. Their reproduction in captivity is poor, particularly for the smaller species. Several factors may be responsible, but stress is probably the most important. We assayed cortisol, LH, FSH, prolactin, testosterone, estradiol, and progesterone in single blood samples obtained under sedation from seven neotropical species and, for comparison, in stressed and unstressed domestic cats. Cortisol was also assayed in serial blood samples obtained after ACTH administration in Leopardus tigrinus, L. wiedi and domestic cats. While, in general, the results were fairly consistent, there were some statistically significant differences between species that were large enough to be of practical importance.

The effect of ACTH stimulation on cortisol and progesterone concentrations in intact and ovariohysterectomized domestic cats

The objective was to evaluate the adrenocortical capacity for cortisol and progesterone production in female cats, both while intact and after ovariohysterectomy. Five privately owned female cats, 1-3 years old, were used in two trials while intact at an inactive stage of the cycle, and again in two trials, 2 weeks after ovariohysterectomy. The four trials were: intact saline injection control trial; intact ACTH injection (0.125 mg); ovariohysterectomized saline injection control trial; and ovariohysterectomized ACTH injection. Blood samples were obtained by an indwelling cephalic vein catheter at -30 and 0 min (immediately before injections) and at 60, 90, 120 and 180 min after injection. The mean basal pre-treatment concentrations of cortisol in the intact and ovariohysterectomized cats were 33 +/- 19 and 32 +/- 19 nmol/L, respectively; the corresponding values for progesterone were 1.1 +/- 0.6 and 0.7 +/- 0.6 nmol/L, respectively. Saline did not alter the serum cortisol or progesterone concentrations. In contrast, both cortisol and progesterone were elevated after ACTH, with peak values at 90 min and returned to basal levels at approximately 180 min. There was a positive correlation between cortisol and progesterone concentrations (r = 0.8, P < 0.05). In some instances, the procedure used to restrain the cats during blood collection induced increases in cortisol and progesterone of the same magnitude as when the ACTH was administered; these effects of restraint could alter the results of assisted reproduction efforts.

Impact of ACTH administration on the oviductal sperm reservoir in sows: The local endocrine environment and distribution of spermatozoa

The objective of the study was to investigate if short-term stress in sows (simulated by injections of synthetic adrenocorticotrophic hormone (ACTH)) during standing oestrus had a negative effect on the local environment in the utero-tubal junction (UTJ) and isthmus and the distribution of spermatozoa in these segments. Fourteen sows were monitored for ovulation using ultrasonography in two consecutive oestruses. The sows were fitted with jugular catheters and, from onset of the second oestrus, blood samples were collected every second hour. In the 2nd oestrus, seven sows were given ACTH every second hour, from the onset of standing oestrus until the sow ovulated (ACTH-group), whereas the other seven sows remained as controls (C-group) and were given NaCl solution. The sows were artificially inseminated 16-18 h before expected ovulation. Six hours after ovulation the sows were anaesthetised, and blood samples were repeatedly taken from veins draining the uterus and the UTJ-isthmus, respectively. This oviduct was thereafter removed and divided in four adjacent sections consisting of: (i) the UTJ, (ii) the first, and (iii) the second isthmus segment prior to (iv), the ampullary-isthmic junction (AIJ) and the ampulla. The three first-mentioned segments were flushed to retrieve spermatozoa, whereas the last one was flushed to collect oocytes/ova. The number of spermatozoa attached to the zona pellucida was counted. The concentrations of cortisol in jugular blood of the ACTH-group sows during the time of ACTH-injections were significantly higher than of the C-group sows (p<0.05), as were the levels of progesterone (p<0.001). Progesterone and cortisol concentrations measured in the blood samples draining the UTJ-isthmic region 6 h after ovulation did not significantly differ between the groups, but the C-group displayed significantly higher concentrations of progesterone in the UTJ-isthmic region compared with the levels measured in parallel samples taken of jugular blood (p<0.01). The C-group, but not the ACTH-group, also displayed a significant elevation in progesterone concentration 6h after ovulation compared with the basal levels before ovulation (p<0.01). Numbers of retrieved spermatozoa were not significantly different between the C-group and the ACTH-group. However, there was a tendency for a larger number of spermatozoa among sows in the ACTH-group, especially in the isthmic segment adjacent to the AIJ. In conclusion, simulated stress induced by injections of ACTH during standing oestrus results in elevated concentrations of progesterone before ovulation and may interfere with the rise of progesterone after ovulation. However, ACTH-injections appeared to augment transport of spermatozoa through the female genital tract of pigs.

Ultrasonographic appearance of the conceptus, fetal heart rate and profiles of pregnancy-associated glycoproteins (PAG) and prostaglandin F2α-metabolite (PGF2α-metabolite) after induction of fetal death with aglepristone during early gestation in cattle

A higher incidence of fetal losses, especially after the use of artificial reproduction techniques, asks for more intensive monitoring of bovine pregnancies. In this study, a model for fetal death (FD) was created by administering the antiprogesterone aglepristone twice, at Day 47 and 48 of gestation (n=5). Control heifers received the solvent (n=5). The temporal relationships between changes in ultrasonographic appearance of fetal fluids and membranes, fetal heart rate (FHR) and peripheral plasma levels of pregnancy-associated glycoprotein (PAG) and PGF2alpha-metabolite as determined by radioimmunoassay associated with FD were monitored at eight hour intervals around treatment. For the analysis of plasma levels the period under study was divided into five epochs (T1: before injection of aglepristone/solvent; T2: from first to second injection; T3: from second injection to FD; T4: from diagnosis of FD to 56 h later; T5: from 56 h to 104 h after diagnosis of FD). Control heifers produced healthy calves at term, but in treated heifers, FD occurred on average at 58 (range 48-80) h after first injection of aglepristone. Fetal death was always preceded by a visible reduction of the amount of allantoic fluid and by segregation of the allantochorionic membrane from the endometrium. FHR remained rather constant in both groups, but a (non-significant) drop in FHR around 8h before FD was diagnosed in four of five treated animals. All fetuses were expulsed after FD. Levels of PAG remained constant or even slightly increased in controls, but decreased in treated animals from T2 onward: levels during T4 and T5 significantly differed from those during T1 and from values in controls during T4 and T5 (P<0.01). PGF2alpha-metabolite levels did not change in the controls, but in the treated group they were significantly higher during T3 when compared to T1 (P<0.05). After this increase, a sharp decrease in PGF2alpha-metabolite level occurred, reaching a significantly lower level at T5 when compared to control animals (P=0.01). It is concluded, that FD induced by aglepristone is preceded by ultrasonographic visible changes in fetal membranes and fluids and a rise in PGF2alpha-metabolite and is followed by a drop in PAG and PGF2alpha-metabolite.

Environmental, genetic and social factors affecting the expression of estrus in beef cows

Genetic, social and environmental factors affecting behavioral estrus were evaluated in Angus (n = 10), Brahman (n = 10) and Senepol (n = 10) cows during a PGF2alpha synchronized estrus and subsequent spontaneous estrus. Cows were equally stratified by breed to two groups of 15. Both groups were pre-synchronized with a modified two-injection PGF2alpha protocol. At the start of the experiment, cows were treated with 25 mg PGF2alpha followed by a second and third administration of 12.5 mg PGF2alpha, 11 and 12 days later to induce synchronized estrus. The subsequent estrus was designated as spontaneous estrus. Behavioral estrus data including the onset and end of estrus, estrous duration and the total number of mounts received for the synchronized and spontaneous estruses were collected using HeatWatch". Interval from the third PGF2alpha, treatment to the onset of a HeatWatch" estrus occurred earlier (P < 0.05) in Angus (31 +/- 5 h) than Brahman (53 +/- 7 h) or Senepol (53 +/- 4 h) cows, with dominant Senepol and Brahman cows taking longer to exhibit estrus after PGF2alpha than subordinate cows. The duration of the synchronized estrus tended to be shorter (P < 0.06) in Senepol (12 +/- 3 h) than in Angus (19 +/- 2 h) or Brahman (17 +/- 2 h) cows. Behavioral estrus data between the two periods were confounded by greater temperature-humidity index (THI) values during spontaneous estrus. The THI during spontaneous estrus appeared (P = 0.09) to affect the duration of estrus (9 +/- 1 h versus 16 +/- 1 h) and did affect (P < 0.0001) the total number of mounts received (8 +/- 4 mounts versus 34 +/- 4 mounts) during spontaneous estrus compared to synchronized estrus. Breed had no effect (P > 0.10) on the duration and total number of mounts received during synchronized and spontaneous estruses. In conclusion, type of estrus (synchronized or spontaneous), THI, social dominance and breed exerted significant effects on characteristics associated with behavioral estrus in beef cattle in subtropical environments.

Postovulatory effect of repeated intravenous administration of ACTH on the contractile activity of the oviduct, ova transport and endocrine status of recently ovulated and unrestrained sows

The effect of repeated intravenous administration of ACTH (Synacthen depot) on the contractile activity of the oviduct, ova transport and endocrine status was studied in 11 Swedish crossbred (Landrace x Yorkshire) multiparous sows. In the second estrus after weaning, the ACTH group (Group A, n=6) sows were administered 0.01 mg/kg body weight of ACTH every 6 h commencing 4 to 8 h after ovulation, whereas the control group (Group C, n=5) sows were administered saline solution. Immediately after standing estrus, a Millar pressure transducer was placed about 3 cm into the isthmus via a laparotomy. Blood samples for hormonal analyses and pressure recordings of the oviduct were collected from all sows until slaughter. After slaughter, the genital tract opposite to the side with the transducer was retrieved, and 3 equal isthmic segments and the first third of the uterine horn portion adjacent to the UTJ were flushed separately for ova recovery. Cortisol levels were significantly (P<0.05) elevated after ACTH administration. Progesterone and PGF2alpha metabolite levels were significantly (P<0.05) elevated only after the first ACTH administration. No significant differences (P>0.05) were seen in the mean pressure and frequencies of phasic pressure fluctuations either before or after every ACTH administration between Groups A and C. No significant difference (P>0.05) was seen in the proportion of ova recovered in the different segments between Groups A and C. It can be concluded from the present study that the administration of ACTH (0.01 mg/kg body weight) to sows at 4 to 8 h after ovulation, and after each subsequent ACTH administration, elevates cortisol levels, whereas progesterone and PGF2alpha metabolite levels are elevated only after the first treatment, and that this has no effect on the mean isthmic pressure, the frequency of phasic pressure fluctuations or ova transport.

Plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite after ACTH (Synacthen Depot) administration in ovariectomized gilts

In order to elucidate the effect of stress on reproductive hormones, the present study was designed to investigate the effect of adrenocorticotropic hormone (ACTH) on the plasma levels of cortisol, progesterone, oestradiol-17 beta and prostaglandin F2 alpha metabolite in ovariectomized gilts. Ovariectomy and cannulation of the jugular vein were performed within 1 week of oestrous detection, under general anaesthesia. Approximately 1 week after surgery, two gilts were each administered ACTH (Synacthen Depot) intravenously, at a dose of 0.01 mg/kg body weight, and one gilt was given saline solution (5 ml). The reverse was performed on the following day. The administration of ACTH was followed by a concomitant elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta. Peak cortisol, progesterone and prostaglandin F2 alpha metabolite levels were reached at 80 +/- 10.0, 80 +/- 10.0 and 46.6 +/- 13.3 min after ACTH administration and the durations of the peaks were 181.8 +/- 19.8, 308.1 +/- 49.7 and 181.8 +/- 7.9 min, respectively. The total area under the curve for cortisol, progesterone and prostaglandin F2 alpha metabolite was significantly higher in the ACTH than in the control group. The present results indicate that during stress, cortisol, progesterone and prostaglandin F2 alpha levels are elevated while the level of oestradiol-17 beta is less affected. It can be concluded that the administration of ACTH to ovariectomized gilts, results in the elevation of cortisol, progesterone and prostaglandin F2 alpha metabolite but not of oestradiol-17 beta.

Endocrine response to pregnanolone

Neuroendocrine effects of the neurosteroids, pregnanolone and allopregnanolone have been demonstrated in rats. The endocrine effects of pregnanolone in humans have so far not been fully elucidated. This study has evaluated the effects of pregnanolone administration on part of the hypothalamus-pituitary-gonadal (HPG) axis throughout the menstrual cycle in control subjects and patients with premenstrual syndrome (PMS). Intravenous pregnanolone and vehicle were given to eight women with, and eight women without, PMS during the mid-follicular and late luteal phase. Following the drug administrations, progesterone, estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin plasma levels were measured. Intravenous pregnanolone induced a rise in progesterone levels in the follicular phase. In the luteal phase progesterone levels decreased in response to pregnanolone provocation. Pregnanolone did not induce any changes in estradiol, LH, FSH or prolactin plasma levels in either cycle phase. PMS patients and control subjects did not differ with respect to the endocrine effects of pregnanolone. In conclusion, our data show that pregnanolone, in moderate doses, appears not to have any adverse effects on the HPG axis, irrespective of cycle phase.

Seasonal patterns of sex steroids determined from feces in different social categories of Greylag geese (Anser anser)

Seasonal patterns of fecal 17beta-OH-androgen, estrogen, and progesterone equivalents of male and female greylag geese (Anser anser) were analyzed in a flock of free-living geese. These were compared among social categories determined by pairbond status and breeding success. The annual cycle was divided into 13 phases. Phasewise intra-sexual comparisons were made between social categories. The seasonal variation obtained from feces was in general agreement with the literature on plasma patterns in geese and other temperate-zone birds. However, there were distinct differences in seasonal hormone patterns among the social categories. In unpaired males, androgen was elevated for a longer period of time during sexually active phases compared with paired males. In male geese, high levels of androgen did not interfere with parenting but were related to pairbond status, whereas in females, androgen and progesterone were positively related to parental behavior. In the Fall, androgen, progesterone, and estrogen peaked only in unpaired males. In unsuccessful females, estrogen started to increase earlier in the Winter and was higher in amplitude and duration than that in females guarding offspring. In general, fecal steroids showed a clear-cut difference only between sexually active and parental phases of the year in the successfully breeding pairs, whereas unpaired males retained a hormonal state closer to sexually active phases throughout the year.

Priming effect of exogenous oestradiol on luteinizing hormone secretion in prepubertal lambs

The effect of repeated administration of oestradiol-17beta on luteinizing hormone (LH) secretion was studied in 3-month old female lambs (n = 20). Animals were randomly divided in five groups and treated or not treated (group I) with 1, 2 or 3 i.m. injections of oestradiol in corn oil vehicle (1 microg/kg). Animals were slaughtered 12 (group II) and 24 h (group III) after the first injection, 24 h after the second injection (group IV) and 24 h after the third injection (group V). Animals in groups IV and V were catheterized and blood samples were collected every 4 h starting before treatment until time of sacrifice. In the rest of the groups blood samples were taken at the time of slaughter. The number of follicles > 1 mm in diameter on the ovarian surface were recorded and classified according to size. Maximum levels of oestradiol ranged from 103 to 250 pmol/l and returned to baseline within 12 to 16 h after each injection. LH secretion showed a consistent pattern in all lambs, with increases between 8 and 16 h after each oestradiol injection. The highest amplitude and longest duration (8-12 h) of LH secretion was recorded after the second oestradiol injection. Preliminary data indicated that FSH secretion resembled that of LH. There was an increase in the number of follicles with a diameter of more than 2 mm. Plasma concentrations of progesterone and cortisol were low and did not differ within groups or between treatments. The findings confirm that the pituitary LH release system in ewe lambs is sensitive to the stimulatory effects of oestradiol long before puberty. Results indicate that priming with oestradiol increases pituitary LH release to subsequent challenges of oestradiol, but long time exposure to oestradiol may have a negative effect on LH secretion. Although none of the oestradiol-treated lambs ovulated, the increase in the number of large follicles with repeated injections of oestradiol suggests that small follicles were gonadotrophin-responsive and stimulated by the gonadotrophin release.

Effects of post-ovulatory food deprivation on oviductal sperm concentration, embryo development and hormonal profiles in the pig

Nutrition is one of the multiple factors that modulate reproduction in animals. The effect of 48 h food deprivation on reproductive and metabolic hormonal changes in relation to cleavage rates was studied. Insemination of 15 sows was performed 20-10 h prior to expected ovulation and ova were recovered at slaughter 65-91 h post ovulation. Blood samples were collected every second hour, beginning from the time of insemination until slaughter, for measurements of progesterone, cortisol, the prostaglandin F2alpha metabolite (15-keto-13,14-dihydro-PGF2alpha) and insulin levels. The embryos from the food-deprived sows (D-group) had fewer accessory spermatozoa in their zona pellucida (ZP) compared with the control sows (C-group). A lower cleavage rate of the embryos in the D-group compared with the C-group was detected. Plasma progesterone, cortisol and prostaglandin F2alpha metabolite levels were significantly higher in the D-group compared with the C-group. Food deprivation is associated with changes in reproductive and metabolic hormones that might lead to changes in the oviductal environment, culminating in a lower cleavage rate of the embryos and presence of fewer viable spermatozoa in the reservoir.

Plasma levels of progesterone and cortisol after ACTH administration in lactating primiparous sows

The effect of adrenocorticotropic hormone (ACTH) administration on progesterone and cortisol concentrations was determined in lactating primiparous sows. Physiological saline and 50 IU ACTH were administered on days 20 and 21 of lactation at 0900 hours via an indwelling jugular catheter. Blood samples for hormone analysis were collected via indwelling jugular catheters every 15 min (0800 to 1200 hours) and every 60 min (1300 to 1500 hours). Saline administration had no effect on progesterone nor cortisol concentrations in the lactating sows. Progesterone and cortisol concentrations increased (p < 0.001) within 15 min after ACTH administration. Progesterone and cortisol concentrations peaked (p < 0.01) within 45 min and had returned to pretreatment values within 120 min after ACTH treatment.

Plasma levels of progesterone and cortisol after ACTH administration in lactating primiparous sows

The effect of adrenocorticotropic hormone (ACTH) administration on progesterone and cortisol concentrations was determined in lactating primiparous sows. Physiological saline and 50 IU ACTH were administered on days 20 and 21 of lactation at 0900 hours via an indwelling jugular catheter. Blood samples for hormone analysis were collected via indwelling jugular catheters every 15 min (0800 to 1200 hours) and every 60 min (1300 to 1500 hours). Saline administration had no effect on progesterone nor cortisol concentrations in the lactating sows. Progesterone and cortisol concentrations increased (p < 0.001) within 15 min after ACTH administration. Progesterone and cortisol concentrations peaked (p < 0.01) within 45 min and had returned to pretreatment values within 120 min after ACTH treatment.