Season influences FSH concentration in ovariectomized Ile-de-France ewes

Ile-de-France ewes were ovariectomized during anoestrus or the mid-luteal phase of an oestrous cycle (day of ovariectomy = Day 0). In a short-term study, FSH concentrations were measured in blood samples collected hourly the day before and on Days 1, 3, 7 and 15 after ovariectomy (10 ewes per group). FSH concentrations increased significantly from 6.1 to 16.5 ng/ml within 1 day of ovariectomy and increased further to 47.1 ng/ml by Day 15. Differences between seasons of ovariectomy were not significant. In a long-term study, FSH concentrations were measured in blood samples collected hourly on Days 7, 15, 30, 60, 90, 120, 150 and 180 after ovariectomy in anoestrus or the breeding season (10 ewes per group). Further samples were taken (5 ewes/group) at 240 and 365 days after ovariectomy. The pattern of change in FSH after ovariectomy differed between the two seasons and the interaction between season and sampling day was significant. For ewes ovariectomized during anoestrus, FSH concentrations increased to a maximum by Day 180 and remained high thereafter. In contrast FSH increased more slowly in ewes ovariectomized in the breeding season and differences between the groups were significant from Day 90 to Day 270. However, both groups had similar FSH concentrations at Day 365. These results show that FSH concentrations increase rapidly after ovariectomy. There are seasonal differences in FSH concentrations in the absence of ovarian feedback with increases in FSH concentration around the time of the onset of the breeding season. Once FSH concentrations had reached a maximum, major seasonal changes were no longer apparent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive, hormonal and milk characteristics in ewe lambs treated with ovine growth hormone before breeding

One month before a fall breeding season, 30 6-mo-old fine-wool ewe lambs were allotted to one of three treatment groups consisting of either 0, 2.5 or 5 mg ovine growth hormone (oGH) daily for 10 d and then, on alternate days, for an additional 20 d. Five ewes from each treatment group were bled at hourly intervals for 8 h on Days 0 (first day of treatment), 9, 19 and 29. Milk yield and composition were examined on Day 21 post partum. Neither feed intake nor ewe weights differed (P > 0.20) among treatments. Serum insulin did not differ (P > 0.20) among treatments before or during the 5 h following treatment on Day 0 or 29; however, 6, 7 and 8 h after oGH administration, a linear, dose-dependent increase (P < 0.10) in serum insulin was noted. On Day 9, serum insulin differed linearly (P < 0.10) before and after treatment. On Day 19, serum insulin differed (P < 0.10) among the groups 2, 3, 6, 7 and 8 h following oGH treatment. One hour after treatment on Day 0, serum GH increased linearly (P < 0.01) among groups. Serum GH continued to rise 3 h after treatment and remained elevated through Hour 8 in ewes receiving oGH. Serum GH was increased (P < 0.01) before and after oGH administration on Days 9, 19 and 29 in GH-treated ewes. Percentage of ewes that cycled during treatment or breeding as determined by serum progesterone was similar (P > 0.20) among groups. Pregnancy rates did not differ (P > 0.20) in ewe lambs receiving 0 (70%), 2.5 (80%) and 5 (60%) mg oGH. No differences were detected (P > 0.40) in milk yield or composition among treatments. In fine-wool ewe lambs treated with 2.5 or 5 mg of exogenous oGH for 30 d before breeding, neither reproductive performance nor subsequent milk production were enhanced; however, these treatments increased serum GH and insulin.     

Effect of respiratory syncytial virus infection on the uptake of and immune response to other inhaled antigens

Groups of BALB/c mice were sham infected or inoculated intranasally (IN) with live RSV. From Day 4 to 8 after infection, the animals were exposed IN to ovalbumin (OVA) with or without alum adjuvant. At different intervals, levels of OVA concentration in serum, IgG-anti-OVA antibody activity in serum, and IgA-anti-OVA antibody activity in bronchial washings were determined, employing the ELISA technique. IgE-anti-OVA antibody titers in serum and bronchial washings were assessed by PCA. OVA concentrations in serum were significantly higher in RSV-infected animals compared to uninfected controls. The use of alum adjuvant also increased OVA uptake in uninfected animals but to a lesser extent than RSV infection. RSV-infected animals developed significantly higher OVA-specific antibody titers of IgG isotype in serum and IgA isotype in bronchial washings than the uninfected controls, while alum enhanced the immune response less markedly but still significantly in uninfected mice. An IgE antibody response to OVA in serum was demonstrable in 50% of RSV-infected mice immunized IN with OVA and alum, while all uninfected animals and RSV-infected animals immunized with OVA alone (without adjuvant) failed to develop a detectable IgE response. These findings suggest that infections with viral agents such as RSV may function as adjuvants for other antigens inhaled during acute respiratory infection. These observations may explain the alterations in the immune response to other antigens in patients with acute viral-induced bronchopulmonary diseases.     

Ultrasonographic evaluation of uterine involution and postpartum follicular dynamics in French jennies (Equus asinus)

Uterine involution and follicular dynamics during postpartum period were studied ultrasonographically in French jennies. For the study of uterine involution in postpartum jennies (n = 6, Group S), sonographic measurements of different parts of the uterus and endometrium were made at three-day interval, starting from the day of foaling and continued up to 33 days postpartum. Uterine dimensions were also recorded in non-pregnant jennies (n = 3, Group C) throughout a cycle and compared with the dimensions of Group S jennies observed on the day of complete involution. Follicular dynamics of first and second postpartum ovulatory cycles were studied and compared with that of the single estrous cycle of Group C jennies. Jugular venous blood samples of Group S jennies were collected at weekly intervals for 49 days, commencing at the appearance of first preovulatory follicle, to support the sonographic findings. The average involution period was 22.5 +/- 1.7 days. However, it was significantly delayed (P < 0.05) in jennies which came into first postpartum ovulatory heat within Day 9 than those who came later (25.0 +/- 1.0 versus 20.0 +/- 1.0). The endometrial layer was not discernible beyond Day 15 postpartum and thus was found to be unreliable index of uterine involution. The follicular growth rate (mm per day) and diameter (mm) of preovulatory follicle in postpartum jennies were similar to that in normal cycling jennies (P > 0.05). The first and second ovulations occurred at 14.6 +/- 0.8 and 39.0 +/- 0.8 days postpartum in Group S jennies. All the corpora lutea, either echogenic or centrally non-echogenic were functionally similar and had similar life span (P > 0.05). In conclusion, the postpartum reproductive events related to uterine involution and ovarian cyclicity apparently resemble that of mares.     

Serum amyloid-A (SAA) and haptoglobin (Hp) plasma concentrations in newborn calves

The concentrations of 2 major bovine acute-phase proteins, haptoglobin (Hp) and serum amyloid-A (SAA), were measured in plasma obtained shortly after birth from 22 healthy calves. In a separate group of diseased calves (n = 8), Hp and SAA concentrations were measured to determine whether newborn calves (up to 4 d old) are able to produce SAA and Hp. In blood samples taken directly after birth, the Hp plasma concentrations were all below the limit of detection. The mean SAA concentration was independent of weight (r = 0.063), degree of acidosis (r = -0.125), sex (p > 0.05), and were not different in calves born after different types of obstetrical help (p > 0.05). In the group of diseased calves, an increased Hp concentration was measured in only 2 of 8 animals, whereas the mean SAA concentration was significantly higher (p < 0.05) than in the healthy newborn calves. These data suggest that prenatal stress due to parturition does not form a stimulus for the production of acute-phase proteins in the fetal calf. The low Hp plasma concentrations might indicate that either it takes a few days to establish a detectable concentration of this protein, or that Hp production is not fully developed in newborn calves.     

Serum leptin levels and their response during laparoscopic and open cholecystectomy

We compared serum leptin responses during and after laparoscopic and open cholecystectomy, and assessed their correlation with the responses of inflammatory cytokines. Serum levels of leptin, interleukin-1alpha (IL-1alpha), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were measured by an enzyme-linked immunoassay in 31 patients who underwent laparoscopic cholecystectomy and in 24 patients who underwent open cholecystectomy. Serum samples were obtained preoperatively, at 10 and 30 min after the commencement of surgery, and at 6 and 24 h after the operation. The cumulative responses of leptin, IL-1alpha, IL-6 and TNF-alpha to surgery were calculated and the associations between them were evaluated. Serum leptin levels were significantly increased at 24 h after both procedures. The serum leptin concentration at this time point and the cumulative leptin response were significantly lower after laparoscopic cholecystectomy than after open cholecystectomy. Changes in serum IL-1alpha, TNF-alpha and IL-6 concentrations showed similar kinetics in both groups, with postoperative IL-6 levels being consistently lower in the laparoscopic cholecystectomy group. Cumulative IL-6 and TNF-alpha responses were significantly lower after laparoscopic cholecystectomy than after open cholecystectomy. The cumulative responses of leptin, IL-1alpha and IL-6 correlated significantly with each other. Leptin may be involved in the systemic inflammatory response to surgical injury, and the postoperative leptin elevation and cumulative leptin response are significantly lower after laparoscopic cholecystectomy than after open cholecystectomy.     

Role of short days in timing the onset and duration of reproductive activity in ewes under artificial photoperiods

The objective of this work was to evaluate the role of short photoperiod in timing the onset and duration of reproductive activity in ewes. The perception of photoperiod was disrupted by pinealectomy following transfer from long (17L:7D) to short (8.5L:15.5D) photoperiod and the subsequent reproductive response was monitored. Ovariectomized ewes given Silastic implants containing estradiol-17 beta were exposed to long days until Day 0 (May 24) and then were allocated to the following groups (n = 5-6/group): Group 1) short-day control--moved to short days; Groups 2 to 5) pinealectomy after 0, 30, 60, or 90 short days, respectively; Group 6) long-day hold--kept on long days; Group 7) long days after 60 short days--moved to short days on Day 0 and returned to long days on Day 60. Six ewes kept outdoors served as additional controls. Reproductive neuroendocrine activity was assessed from plasma LH concentrations, high values being indicative of the breeding season and low values indicative of anestrus. Time of reproductive neuroendocrine activity onset (LH rise) did not differ among animals in the 7 groups kept indoors, but was advanced (p less than 0.05) relative to that of ewes outdoors. In contrast, duration of the LH elevation differed among ewes in groups kept indoors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Luteinizing hormone secretion as influenced by age and estradiol in the prepubertal gilt

The aim of this study was to determine if there is an age related reduction in the sensitivity of the negative feedback action of 17β-estradiol (estradiol) on luteinizing hormone (LH) secretion in the prepubertal gilt. Ovariectomized gilts at 90 (n=12), 150 (n=11) or 210 (n=12) days of age received estradiol benzoate (EB) osmotic pump implants 6/group and the remaining animals received vehicle control (C) implants except for 150-day C (n=5) on Day 0. On Day 10 blood samples were collected every 15 min for 8h and serum LH and estradiol concentrations were measured. Serum estradiol concentrations averaged 5 ± 1, 5 ± 1 and 7 ± 2 pg/ml for the 90-, 150- and 210-day-old gilts implanted with estradiol, respectively, whereas, serum estradiol concentrations was undetectable in C gilts. Mean serum LH concentrations, basal LH concentrations and serum LH pulse amplitude were less in EB-treated gilts at all ages compared to control animals. In contrast, LH pulse frequency initially was less in EB-treated gilts but subsequently increased (P<0.04) with age (from 0.8 ± 0.2 at 90 days to 5.2 ± 0.2/8h at 210 days), and at 210 days of age the pulse frequency was similar to C gilts. These results demonstrate an age related reduction in the sensitivity to the negative feedback action of estradiol on LH secretion and support the idea that the gilt conforms to the gonadostat hypothesis.     

Haptoglobin concentrations in free-range and temporarily captive juvenile steller sea lions

Haptoglobin (Hp) is an acute-phase protein synthesized in the liver that circulates at elevated concentrations in response to tissue damage caused by inflammation, infection, and trauma. As part of a larger study, sera Hp concentrations were measured in temporarily captive (n = 21) and free-range (n = 38) western stock juvenile Steller sea lions (Eumetopias jubatus) sampled from 2003 to 2006. Baseline Hp concentration at time of capture was 133.3 +/- 17.4 mg/dl. Temporarily captive animals exhibited a 3.2-fold increase in Hp concentrations during the first 4 wk of captivity, followed by a return to entry levels by week 5. Haptoglobin levels were not influenced by age, season, or parasite load. There was a significant positive correlation between Hp concentrations and white blood cell count (P < 0.001) and globulin levels (P < 0.001) and a negative correlation to red blood cell count and hematocrit (P < 0.001 for both). There was no correlation between Hp levels and platelet count (P = 0.095) or hemoglobin (P = 0.457). Routine blubber biopsies collected under gas anesthesia did not produce a measurable Hp response. One animal with a large abscess had an Hp spike of 1,006.0 mg/dl that returned to entry levels after treatment. In conclusion, serum Hp levels correlate to the stable clinical health status observed during captivity, with moderate Hp response during capture and initial acclimation to captivity and acute response to inflammation and infection.     

Effect of vascular cannulation on serum concentrations of LH, FSH, prolactin and cortisol in prepubertal gilts

Two experiments were conducted to determine whether cannulation of the jugular vein in gilts alters serum concentrations of LH, FSH, prolactin (PRL) or cortisol (C). In Experiment 1, 12 crossbred prepubertal gilts weighing 95 +/- 1.3 kg were immobilized by snaring, and tygon tubing was threaded into the anterior vena cava through a 12-gauge needle inserted into the jugular vein. Five hours later, blood samples were drawn at 20-min intervals for 4 h (Day 0). Samples were also drawn at 20-min intervals for 4-h periods 24 h (Day 1) and 48 h (Day 2) after cannulation. Serum concentrations of LH were similar (P=0.26) among Day 0 (0.40 ng/ml), Day 1 (0.39 ng/ml) and Day 2 (0.34 ng/ml). Serum PRL was similar (P=0.07) among Day 0 (4.10 ng/ml), Day 1 (3.87 ng/ml) and Day 2 (3.43 ng/ml). Serum concentrations of C were greater (P < 0.001) on Day 0 (8.32 ng/ml) than Day 1 (4.48 ng/ml) or Day 2 (3.54 ng/ml). In Experiment 2, cannulas were placed in 29 prepubertal gilts. Two days after initial cannulation, six blood samples were drawn at 20-min intervals. Gilts were then immobilized by snaring, and a second cannulae was inserted into the contralateral vein. Five blood samples were taken at 2-min intervals during the second cannulation and then six samples were drawn at 20-min intervals. Serum LH and FSH were not altered by cannulation or elevated during the subsequent 2-h sampling period (P>0.05). In contrast, serum concentrations of PRL rose slowly (P<0.05) during cannulation and remained elevated for 60 min before returning to baseline. Serum concentrations of C rose within 6 min of cannulation, remained elevated for 30 min, and then declined over the next 90 min. From these two experiments, it appears that secretory patterns of LH and FSH can be accurately assessed immediately after cannulation in prepubertal gilts. Measurements of serum PRL and C that reflect nonstressed conditions, however, cannot be obtained until at least 2 h or 1 d after cannulation, respectively.     

Acute phase protein response in the capybara (Hydrochoerus hydrochaeris)

We evaluated the acute phase protein response in capybaras (Hydrochoerus hydrochaeris). Three animal groups were used: 1) healthy animals (n=30), 2) a group in which experimental inflammation with turpentine was induced (n=6), and 3) a group affected with sarcoptic scabies (n=14) in which 10 animals were treated with ivermectin. Haptoglobin (Hp), acid-soluble glycoprotein (ASG) and albumin were analyzed in all animals. In those treated with turpentine, Hp reached its maximum value at 2 wk with a 2.7-fold increase, whereas ASG increased 1.75-fold and albumin decreased 0.87-fold 1 wk after the induction of inflammation. Capybaras affected with sarcoptic scabies presented increases in Hp and ASG of 4.98- and 3.18-fold, respectively, and a 0.87-fold decrease in albumin, compared with healthy animals. Haptoglobin and ASG can be considered as moderate, positive acute phase proteins in capybaras because they showed less than 10-fold increases after an inflammatory process and reached their peak concentrations 1 wk after the induction of inflammation. Conversely, albumin can be considered a negative acute phase protein in capybaras because it showed a reduction in concentration after inflammatory stimulus.     

Social regulation of plasma estradiol concentration in a female anuran

The behavior of an individual within a social aggregation profoundly influences behavior and physiology of other animals within the aggregation in such a way that these social interactions can enhance reproductive success, survival and fitness. This phenomenon is particularly important during the breeding season when males and female must synchronize their reproductive efforts. We examined whether exposure to conspecific social cues can elevate sex steroid levels, specifically estradiol and androgens, in female túngara frogs (Physalaemus pustulosus). We compared plasma estradiol and androgen concentrations in wild-caught females before and after exposure to either natural mate choruses or random tones. After exposure to mate choruses for 10 consecutive nights, estradiol concentrations were significantly elevated whereas there was no significant elevation in estradiol concentrations in the group of females exposed to random tones for 10 nights. Plasma androgen concentrations were not significantly changed after exposure to either natural mate choruses or random tones for 10 consecutive nights. Social modulation of estradiol concentrations may be important in maintaining a female's reproductive state while males are chorusing. To our knowledge, this is the first study to demonstrate social regulation of estradiol concentration in female anurans.     

IgG,IgA, and lysozyme in Martina Franca donkey jennies and their foals

Because immune transfer from jenny to donkey foal is mostly unknown, the aim of the present study was to evaluate, from 5 days before to 10 days after foaling, immunoglobulin (Ig)G, IgA, and lysozyme peripartal concentrations in serum and mammary secretions of 10 healthy, spontaneously foaling Martina Franca jennies and in serum of their mature, viable, healthy foals, in the first 10 days after birth. The results showed that, in jennies, mammary secretion of IgG levels (ranging between 16 and 75 mg/mL) and IgA (0.9–2 mg/mL), and IgG (6.8–13.5 mg/mL) and IgA (0.5–2.4 mg/mL) serum concentrations were not different along the time of study. Also, IgG concentrations in serum of foals did not show significant differences although a high level was observed at 12 hours after birth (8 mg/mL), and IgA concentrations in serum of foals did not show any significant difference, although a high level was observed at 12 hours after birth (1.2 mg/mL). Lysozyme increased significantly at Day 2 after parturition in mammary secretions of jennies (551.9 μg/mL) and at 12 hours in serum of foals (25.9 μg/mL). The study demonstrated that the pattern of passive immune transfer in donkey foals seems to be similar to that reported for the horse foal, with IgG predominating IgA in serum and mammary secretions of the jenny and also in serum of foals. The most significant early increase in foals' serum concerns lysozyme, which probably plays an important role in the innate immunity of the donkey foal in the first challenging hours after birth.     

Reproductive seasonality of the jenney

Reproductive seasonality was studied in 12 jennies in southern Wisconsin for 12 mo. The proportion of jennies ovulating differed (P < 0.05) among months due primarily to a lower proportion ovulating during December (64%) than during the other months (82 to 100%). Of 114 interovulatory intervals, eight were considered prolonged (>35 d) due to persistent corpus luteum (two intervals) and a follicular-related anovulatory period (six intervals). Four of the six follicular-related anovulatory periods were attributed to seasonal effects. The anovulatory season in these four jennies occurred in winter, was relatively short (39 to 72 d), and was terminated by a long period (17 to 41 d) of estrous behavior in the continued presence of large follicles (>20 mm). The prolonged estrus accounted for the lower incidence of ovulations during December and seemed similar to the transition between anovulatory and ovulatory seasons in mares. There was a significant effect of month on length of the interovulatory interval, even after removal of the eight prolonged intervals, due primarily to shorter intervals during May to September (means, 23.0 to 24.3 d) than during October to April (25.0 to 27.3 d). Length of estrus differed significantly among months due primarily to shorter periods during May to October (means, 5.7 to 6.9 d) than during November to April (7.4 to 15.2 d). These results indicated that this species is subjected to seasonal effects on reproductive function. However, contrary to the literature, the dramatic partitioning of the year into ovulatory and anovulatory seasons, as occurs in mares, was absent (eight jennies) or limited (four jennies).     

Acute suppression of FSH secretion by oestradiol in the ovariectomized rhesus monkey

Using long-term ovariectomized rhesus monkeys, we examined the ability of oestradiol to decrease circulating FSH concentrations in the absence of other ovarian factors. Daily blood samples were obtained from untreated monkeys for 8 days, followed by insertion of oestradiol capsules after the Day-8 sample was taken. Samples were then taken on Days 9-15, the capsules were removed after the Day-15 sample, and samples were obtained on Days 16-19. Serum was assayed for concentration of oestradiol, FSH and LH by RIA. The concentration of FSH (ng/ml) in serum did not change during the first 8 days before oestradiol treatment (overall mean = 356 +/- 55) but decreased from the Day-8 value of 320 +/- 8 to 190 +/- 42 on Day 9 and by Day 15, after 7 days of oestradiol treatment, had reached a nadir of 20 +/- 5. By Day 17, i.e. 2 days after removal of the oestradiol capsules, serum FSH had increased (P less than 0.05) to 92 +/- 23 with a further increase (P less than 0.05) on Day 19 (171 +/- 16). This study demonstrates that, unlike in rats, mice, and sheep, administration of oestradiol alone to ovariectomized rhesus monkeys reduces immunoreactive serum FSH to concentrations measured in intact animals.     

Plasma urea nitrogen in relation to pregnancy rate in dairy sheep

The aim of this field study was to investigate the relationship of plasma urea nitrogen (PUN) with the pregnancy rate in lactating Awassi × Merino ewes. One hundred and eighty-five Awassi × Merino ewes were used in the present study. Ewes were fed a diet containing 17.4% crude protein and were milked twice a day by the milking machine. The ewes were synchronized for estrus by insertion of intravaginal sponges containing 30 mg flurogestone acetate for 14 days. At the time of sponge removal each ewe was administered eCG (600 IU). All ewes were inseminated twice with fresh semen into the external os of the cervix at 48 and 56 h after sponge removal. The day of insemination was considered as Day 0 for calculating the gestational period. Blood samples were collected from each ewe at Days 0, 18 for measurement of PUN concentrations and at Day 22 after AI for measurement of pregnancy-associated glycoprotein (PAG) by radioimmunoassay (RIA). Thirty-eight ewes (20.5%) were confirmed pregnant by PAG-RIA test at Day 22 and by ultrasonography at Day 80. The mean (±S.D.) concentration of PUN in all ewes at Day 0 was 12.7±4.6 mmol/L. There were non-significant differences in the level of PUN between pregnant and non-pregnant ewes at Days 0 (12.2±4.2 mmol/L vs. 12.8±4.7 mmol/L, respectively) and 18 (9.6±2.9 mmol/L vs. 10.4±4.0 mmol/L, respectively) after AI. Mean PUN concentrations decreased significantly from Day 0 to Day 18 after AI in both pregnant and non-pregnant ewes. By using logistic regression analysis, there was no effect of PUN concentrations on the probability of pregnancy occurrence in the studied ewes (odds ratio: 0.97; 95% confidence interval: 0.9-1.05; P=0.45). In conclusion, there was no evidence of a relationship between PUN concentration and pregnancy rate for lactating Awassi × Merino ewes in the present study because of low pregnancy rate observed.     

Mammary gland differentiation in hypophysectomized, pregnant mice treated with corticosterone and thyroxine.

Swiss Webster mice were hypophysectomized or sham-operated on Day 11 of pregnancy. The animals were fitted s.c. with osmotic minipumps containing either corticosterone (B) dissolved in Molecusol (Pharmatec, Alachua, FL) or the vehicle alone immediately after they were hypophysectomized. Animals in some of the experimental groups also received thyroxine (T4) in their drinking water. The mice were killed on Day 18 of gestation, and mammary tissue was homogenized and extracted for assessment of DNA, RNA, alpha-lactalbumin, and alpha-casein. Serum was assayed for placental lactogen-I (PL-I), and placental lactogen-II (PL-II), B, and T4. The concentration of PL-II in serum was elevated in the hypophysectomized mice, whereas the PL-I concentration did not differ among experimental groups. Hypophysectomy decreased both T4 and B concentrations in serum, and administration of these hormones restored their serum concentrations to normal or, in some cases, somewhat higher than normal levels. Hypophysectomy reduced the total RNA content and RNA/DNA ratio of the mammary gland, but treatment with B alone or with B and T4 restored RNA levels to those of sham-operated animals. T4 alone was ineffective in restoring RNA levels. Sham-operated animals that received hormonal treatment (B and T4) had the highest levels of RNA in the mammary tissue. Hypophysectomized animals had reduced content and concentration of alpha-lactalbumin in the mammary gland as compared to all other experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma hormone profliles and fertility in ewe lambs given progestagen supplementation after mating

Clun Forest ewe lambs (n = 124) were used to investigate the effects of post-mating progestagen supplementation on fertility. The animals were assigned to 1 of 3 three treatments: Group A (n = 41) served as the controls, Group B (n = 42) received 3 weekly injections of 6 mg of medroxyprogesterone acetate (MAP), while Group C (n = 41) was treated with intravaginal sponge containing 60 mg of MAP; all treatments were administered from Day 5 to Day 26 post mating. Supplementation did not increase the percentage of animals pregnant or those lambing: Group A, 72.2 and 66.6%; Group B, 57.5 and 50.0%; and Group C, 67.5 and 60.0%, respectively. Furthermore, there was no effect of supplementation on plasma progesterone, prolactin, cortisol, growth hormone, insulin, or glucose concentrations (P>0.05). However, pre- and post- mating hormone profiles differed significantly between the animals that lambed or aborted and the animals which were found to be barren at lambing. In the barren animals, progesterone concentrations were lower 4 days before and 9 to 33 days after mating (P<0.01), while overall prolactin concentrations were higher throughout the trial (P<0.01). But there was no difference between barren and fertile lambs in cortisol, growth hormone, insulin or glucose concentrations (P>0.05). These results indicate that progestagen supplementation does not increase the reproductive performance of ewe lambs. However, infertility is associated with reduced luteal function and increased prolactin concentration before and after mating.     

Luteinizing hormone (LH) release after single injections of a synthetic LH-releasing hormone (LH-RH) in the ewe at three different reproductive stages and comparison with natural LH release at oestrus

The possibility was investigated of using single i.v. injections of a synthetic luteinizing hormone-releasing hormone (LH-RH) to manipulate the reproductive pattern of the ewe.Single i.v. injections of 150 μg synthetic LH-RH were given on Day 12 of the oestrous cycle, during seasonal anoestrus and on Day 16 $\text{post}$-$\text{partum}$ in ewes which lambed during the breeding season. Blood samples were obtained at 5-, 10- or 15-minute intervals for 1 hour before and for 3 hours after treatment. Plasma LH concentrations were measured using a specific double antibody radioimmunoassay, the development of which is described. Laparotomy was performed on each animal 2–3 days after treatment.The treatment induced LH peaks in all animals and ovulation in the majority. There was no significant difference between the groups in the LH response. The LH release was, however, much less than that found in untreated ewes sampled every 15 minutes for 18 hours during oestrus.     

Changes in serum immunoreactive inhibin and follicle-stimulating hormone during gonadal development in male and female rats.

We have measured serum and ovarian immunoreactive inhibin alpha (irI alpha) and serum FSH in fetal and neonatal rats from 20 days of gestation until 40 days of age. For animals aged 10 days or older, serum measurements were made on intact and gonadectomized animals. Serum irI alpha was detectable in intact male and female rats at all ages studied. In females, irI alpha levels were low until Day 5 and then increased steadily to peak at Day 25. Thereafter they declined until Day 35 to reach levels typical of adult females. There was a significant decrease in irI alpha levels 24 h after ovariectomy at all ages. Serum FSH levels in females were low until Day 7, then increased rapidly to plateau from Days 10-15. The levels then declined until Day 25 and were generally unchanged after that time. There was a significant increase in FSH 24 h after ovariectomy in rats aged 20 days and older, and in younger rats by 48 h after ovariectomy. In male rats, serum irI alpha levels were significantly higher than females until Day 7. The levels increased at Day 7 and then remained relatively constant until Day 20, after which they declined to reach typical adult male levels. Serum irI alpha levels were significantly lower in males than females from Days 25-40. There was a significant decrease in serum irI alpha 24 h after castration at all ages studied. Serum FSH levels in males were low until Day 20, increased at Day 25, and thereafter remained relatively unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)