Effect of human chorionic gonadotropin on preovulatory luteinizing hormone surge and ovarian hormone secretion in gilts

The influence of varying doses of human chorionic gonadotropin (hCG) on the preovulatory luteinizing hormone (LH) surge, estradiol-17 beta (E2) and progesterone (P4) was studied in synchronized gilts. Altrenogest (AT) was fed (15 mg X head-1 X d-1) to 24 cyclic gilts for 14 d. Pregnant mares serum gonadotropin (PMSG; 750 IU) was given im on the last day of AT feeding. The gilts were then assigned to one of four groups (n = 6): saline (I), 500 IU hCG (II), 1,000 IU hCG (III) and 1,500 IU hCG (IV). Human chorionic gonadotropin or saline was injected im 72 h after PMSG. No differences in ovulation rate or time from last feeding of AT to occurrence of estrus were observed. All gilts in Groups I and II expressed a preovulatory LH surge compared with only four of six and three of six in Groups III and IV, respectively. All groups treated with hCG showed a rapid drop (P less than .01) in plasma levels of E2 11, 17, 23 h after hCG injection when compared with the control group (35 h). The hCG-treated gilts exhibited elevated P4 concentrations 12 h earlier than the control group (3.1 +/- .5, 3.4 +/- .72, 3.1 +/- .10 ng/ml in groups II, III and IV at 60 h post-hCG vs .9 +/- .08 ng/ml in group I; P less than .05). These studies demonstrate that injections of ovulatory doses of hCG (500 to 1,500 IU) had three distinct effects on events concomitant with occurrence of estrus in gilts: decreased secretion of E2 immediately after hCG administration, failure to observe a preovulatory LH surge in some treated animals and earlier production of P4 by newly developed corpora lutea.     

Active immunization of heifers against luteinizing hormone-releasing hormone, human chorionic gonadotropin and bovine luteinizing hormone

Seventy crossbred heifers were allotted randomly to 10 treatment groups. Treatments consisted of active immunization against ovalbumin (OV) conjugates of luteinizing hormone-releasing hormone (LHRH), human chorionic gonadotropin (hCG) and bovine luteinizing hormone (bLH) with each of three adjuvants. The adjuvants were complete Freund's adjuvant (CFA), M103(6) and 6VR6. Control animals were immunized against OV alone using CFA. Bulls were placed with the heifers following immunization to allow comparison of pregnancy rates between groups. Blood samples were collected weekly for 14 wk to determine antibody concentrations. Significant levels of circulating LH or LHRH antibodies were detected in heifers immunized with each of the hormone conjugates. Complete Freund's adjuvant was the most effective for stimulating antibody response to these antigens; however, M103 was equally effective when used with bLH or hCG conjugates. None of the heifers in the bLH-OV-CFA, bLH-OV-M103 or LHRH-OV-CFA immunization groups was pregnant at slaughter, whereas 71% of the OV-CFA control heifers were pregnant. Fertility suppression may be achieved in the bovine by active immunization against any of these three hormone conjugates. However, the duration of this study (8 wk after immunization) does not allow evaluation of the duration of effectiveness of each of the treatments.     

Administration of porcine somatotropin by sustained-release implant: growth and endocrine responses in genetically lean and obese barrows and gilts.

Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in follicular fluid steroids, insulin-like growth factors (IGF) and IGF-binding protein concentration, and proteolytic activity during equine follicular development

The objective of the present study was to evaluate changes in equine follicular fluid insulin-like growth factor binding protein (IGFBP) proteolytic activity as well as steroid, IGF, and IGFBP concentrations during follicular development in the mare. Mares (n = 14) were classified as either in the follicular phase (n = 8) or luteal phase (n = 6). Follicles (n = 92) were categorized as small (6 to 15 mm; n = 54), medium (16 to 25 mm; n = 23), or large (> 25 mm; n = 15), and follicular fluid was collected. Estradiol and androstenedione levels in follicular fluid were greater (P < 0.05), and IGFBP-3 concentrations tended to be greater (P < 0.10) in large than in small or medium follicles, whereas IGFBP-2, -4, and -5 levels were less (P < 0.05) in large than in small or medium follicles. Estradiol and androstenedione concentrations were negatively correlated (P < 0.01) with IGFBP-2, -4, and -5 but not IGFBP-3 concentrations. To evaluate proteolysis of IGFBP, follicular fluid was incubated with human 125I-labeled IGFBP-2, -3, and -5 and protein separated by 12% SDS-PAGE. Follicular fluid caused little or no proteolysis of 125I-lableled IGFBP-2 or -3, and the small amount of proteolysis of IGFBP-2 and -3 did not differ (P > 0.10) among follicle classes. However, more 125I-labeled IGFBP-5 was cleaved (P < 0.05) by follicular fluid from large follicles collected during the follicular phase than large follicles during the luteal phase, and small or medium follicles from follicular and luteal phase mares indicating that a protease to IGFBP-5 exists in estrogen-dominant equine follicles. This IGFBP-5 protease was inhibited by kallikrein/serine protease and metalloprotease inhibitors. We conclude that the tendency of estrogen-dominant follicles of mares to have greater levels of IGFBP-3 and lesser levels of IGFBP-2 does not appear to be due to differences in proteolysis, whereas changes in IGFBP-5 levels are likely due to changes in activity of a serine protease or metalloprotease. Changes in IGFBP may alter levels of bioavailable IGF that stimulate steroidogenesis and mitogenesis in developing mare follicles.     

Effect of charcoal-extracted porcine follicular fluid and 17 beta-estradiol on follicular growth and plasma gonadotropins in gilts fed a progesterone agonist, altrenogest

Thirty-four gilts in two experiments were fed altrenogest for 18 d to block spontaneous growth of ovulatory follicles after luteolysis. They were injected with estradiol or charcoal-extracted porcine follicular fluid (pFF) to determine 1) whether gonadotropin secretion could be depressed and 2) whether exposure to reduced levels of gonadotropins would result in decreased numbers of medium follicles (3 to 6 mm in diameter). Gilts in Exp. 1 received treatments in a 2 X 2 X 2 factorial arrangement starting 48 h before the last feeding of altrenogest. Corn oil or estradiol (2 micrograms/kg body weight), 5 ml of charcoal-extracted porcine serum (pS) or pFF were injected im four times at 8-h intervals and gilts were sacrificed 24 or 96 h after last feeding of altrenogest. In Exp. 2, gilts received one of four treatments consisting of 1) pS, injected iv nine times at 8-h intervals starting 48 h before the last feeding of altrenogest; 2) pFF, with injection protocol the same as for pS; 3) estradiol injected im three times and 4) four times at 8-h intervals starting 0 and 24 h, respectively, before the last feeding of altrenogest. Compared with pS or corn oil, estradiol increased (P less than .001) plasma estrogen and decreased (P less than .05) plasma luteinizing hormone (LH) without a significant effect on plasma follicle stimulating hormone (FSH). Estradiol, compared with corn oil, decreased (P less than .01) the number of medium follicles from 24.8 to 0/gilt and decreased (P less than .05) the weight of ovarian follicular fluid from 4.2 to 2.1 g/gilt at 72 h after the first injection. Five milliliters of pFF had no significant effect on plasma gonadotropins or number of medium follicles. However, 20 ml of pFF, compared with pS, decreased (P less than .05) plasma FSH from 45 ng/ml to 9 ng/ml 32 h after the first injection, had no effect on plasma LH, decreased (P less than .01) the number of medium follicles from 29.2 to 2.2/gilt and decreased (P less than .01) follicular fluid weight from 3.9 to 1.6 g/gilt by 72 h after the first injection. These results indicate that estradiol or a non-steroidal component of follicular origin can decrease secretion of gonadotropins and suppress recruitment of medium follicles in the pig.     

Effect of short-term feed restriction and refeeding on serum concentrations of leptin, luteinizing hormone and insulin in ovariectomized gilts

Ovariectomized gilts were either placed on full feed (FF) or restricted to one-third of the full feed amount (RST) for 7 days. Blood samples were taken through jugular catheters every 15 min for 4 h at the end of the 7-day period. Then dietary treatments were reversed and 7 days later samples were taken as before. Serum concentrations of leptin, insulin and luteinizing hormone (LH) were determined by radioimmunoassay. LH pulse frequency and mean serum leptin and insulin concentrations were lower (P < 0.01) in RST than FF gilts. Reversal of treatment reversed the patterns of hormone secretion. These results confirm previous observations that feed restriction can inhibit pulsatile LH secretion and also decrease leptin and insulin secretion.     

Effects of zeranol on reproduction in beef bulls: luteinizing hormone, follicle-stimulating hormone, and testosterone secretion in response to gonadotropin-releasing hormone and human chorionic gonadotropin

Effects of zeranol on the maturation of the adenohypophyseal-gonadal axis were studied in beef bulls. Calves were implanted with 36 mg of zeranol at 3-month intervals from birth through 6 months of age (group 2, n = 10) or were not treated (control group 1, n = 10). After 9 months, group-2 calves were given implants of 36 mg of zeranol at 3-month intervals through 18 months of age (group 2B, n = 5) or were not reimplanted (group 2A, n = 5). Areas under the curves outlined by concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone for 6 hours after the administration of 100 micrograms of gonadotropin-releasing hormone (GnRH) were calculated. Gonadotropin-releasing hormone was administered at 3-month intervals from 1.5 through 19.5 months of age. Areas under the curves for concentrations of testosterone for 4 hours after the administration of 10,000 IU of human chorionic gonadotropin (HCG) at 4.5, 7.5, and 10.5 months or 1,000 IU at 13.5 and 16.5 months of age also were calculated. The amount of FSH released was greater (P less than 0.05) for group-2 than for group-1 calves at 4.5 and 7.5 months of age. The amount of FSH released in groups 2A and 2B tended (P less than 0.10) to be greater than that for group 1. Significant differences between groups 2A and 2B were not observed. The amount of LH released at 7.5 months of age was less for groups 1 and 2 than that at earlier ages, and the decrease was greater (P less than 0.05) for group 2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of follicular and oocyte development and reproductive hormone secretion during the ovulatory period in Hungarian native breed, Mangalica, and Landrace gilts

Only a very small amount of physiological data is available about the low fertility (mean litter size is 5.7+/-0.8) of Hungarian native breed, Mangalica (M), sows. The aim of the present paper is to reveal the differences in preovulatory follicle development and intrafollicular oocyte maturation between M and Landrace (L) gilts, with special reference to the peri- and postovulatory secretion and peripheral concentrations of estradiol-17beta (E2), progesterone (P4), and luteinizing hormone (LH). The number of preovulatory follicles was 6.8+/-1.4 and 19.6+/-6.6 in M and L gilts, respectively. A lower degree of cumulus expansion and a lower percentage of mature oocytes (TI/M II) was noted in M. Higher LH and E2 peak levels, a longer E2 to LH peak interval, and lower embryo survival was confirmed. Interestingly, despite the lower number of corpora lutea, a higher peripheral blood level of P4 was shown in M than in L gilts. Both diminished follicular development and protracted oocyte maturation may be involved in low fecundity in M, and the present findings may explain these reproductive phenomena.     

Effect of active immunization against growth hormone releasing factor on concentrations of somatotropin and insulin-like growth factor I in lactating beef cows.

Two experiments were conducted to determine the effects of immunoneutralization of growth hormone-releasing factor [GRF(1-29)-NH2] on concentrations of somatotropin (ST) and insulin-like growth factor I (IGF-I) in lactating beef cows. In Experiment 1, multiparous Hereford cows were immunized against 2 mg GRF(1-29)-(Gly)4-Cys-NH2 conjugated to human serum albumin (GRFi, n = 3) or 2 mg human serum albumin (HSAi, n = 3) at 52 +/- 1 d prior to parturition. Boosters (1 mg) were administered on days 12, 40 and 114 postpartum (pp). Serum samples were collected at 15-min intervals for 5 hr on days 18, 46 and 120 pp, followed by administration (IV) of an opioid agonist (FK33-824; 10 micrograms/kg) and an antagonist (naloxone; .5 mg/kg) at hours 5 and 7, respectively. A GRF-analog ([desamino-Tyr1, D-Ala2, Ala15] GRF (1-29)-NH2; 3.5 micrograms/kg) and arginine (.5 g/kg) were administered at hour 10 on days 47 and 121, respectively. Percentage binding of [125I]GRF (1:100 dilution of serum) 28 d after primary immunization was greater in GRFi (14.3 +/- 4.9) than in HSAi (.7 +/- .3) cows. Binding increased to 29.3 +/- 6.5% after first booster in GRFi cows. Episodic release of ST was abolished by immunization against GRF; concentration and frequency of release of ST were lower (P less than .05) in GRFi than in HSAi cows on all days pp. Concentrations of IGF-I were lower in GRFi than in HSAi cows throughout lactation. Serum ST failed to increase following FK33-824 or arginine in GRFi; however, ST increased after both compounds in HSAi cows. Concentrations of ST following GRF-analog were greater (P less than .05) in HSAi than in GRFi cows. Experiment 2 was conducted to determine if a lower dose of antigen and a single booster would be sufficient to lower ST and IGF-I in lactating cows. Multiparous Hereford and Angus cows were assigned to GRFi (n = 6) or HSAi (n = 6). Primary (1.2 mg) and booster (.5 mg) immunizations were administered -14 and 8 d from calving, respectively. Cows were restricted to 60% of recommended intake of energy during lactation in order to elevate concentrations of ST. Serum samples were collected at 15-min intervals for 6 hr on days 26, 50, 73, 90 and 109 pp. Two of six GRFi cows had binding less than 10% (1:1,000 dilution of serum) and were omitted from further analyses.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of charcoal-extracted, bovine follicular fluid on gonadotropin concentrations, the onset of estrus and luteal function in heifers

A study was conducted to determine the effect of charcoal-extracted, bovine follicular fluid (CFF) on plasma follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations, the interval from luteolysis to estrus, and subsequent luteal function in heifers. Fifteen Angus, Simmental and Hereford heifers were allotted by age, weight and breed to a control (C, n = 8) or a CFF (n = 7) group. Heifers received injections of saline or CFF (iv, 8 ml/injection) every 12 h from d 1 (d 0 estrus) through d 5 of the estrous cycle. On d 6, each heifer was injected (im) with 25 mg of prostaglandin F2 alpha (PGF2 alpha). Blood samples were collected every 12 h by venipuncture starting just before the first saline or CFF injection and continuing until estrus. Thereafter, blood samples were collected every other day during the subsequent estrous cycle and assayed for FSH, LH, estradiol-17 beta and progesterone by radioimmunoassay. Injections of CFF had no effect (P greater than .05) on circulating FSH or LH concentrations from d 1 to 5 relative to the C group; however, there was a transient rise (P less than .05) in FSH concentrations 24 h following cessation of CFF injections. This transient rise in FSH was not immediately followed by an increase in plasma estradiol-17 beta concentrations. Although CFF injections did not interfere with PGF2 alpha-induced luteolysis, the interval from PGF2 alpha injection to estrus was delayed (P less than .05) by 5 d in the CFF group compared with the C group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Concentrations of insulin-like growth factor I and steroids in follicular fluid of preovulatory bovine ovarian follicles: effect of daily injections of a growth hormone-releasing factor analog and(or) thyrotropin-releasing hormone

To determine whether long-term administration of growth hormone (GH)-releasing factor (GRF) and(or) thyrotropin-releasing hormone (TRH) alters ovarian follicular fluid (FFL) concentrations of insulin-like growth factor-I (IGF-I), progesterone, and estradiol (E2), and follicular growth, Friesian x Hereford heifers (n = 47; 346 +/- 3 kg) were divided into the following four groups: control (vehicle; n = 11); 1 micrograms GRF (human [Des NH2 Tyr1, D-Ala2, Ala15] GRF [1-29]-NH2).kg-1 BW.d-1 (n = 12); 1 microgram TRH.kg-1 BW.d-1 (n = 12); or GRF + TRH (n = 12). Daily injections (s.c.) continued for 86 d. On d 89, heifers that had been synchronized were slaughtered and ovaries were removed. Follicles were grouped by magnitude of diameter into the three following sizes: 1 to 3.9 mm (small, n = 55), 4.0 to 7.9 mm (medium, n = 63), and greater than or equal to 8 mm (large, n = 71). Growth hormone-releasing factor and(or) TRH did not affect (P greater than .10) IGF-I concentrations in FFL of any follicle size group. Growth hormone-releasing factor increased (P less than .06) size (means +/- pooled SE) of large follicles (14.7 vs 13.0 +/- .6 mm). Growth hormone-releasing factor also increased (P less than .05) progesterone concentrations 4.4-fold above controls in FFL of medium-sized follicles but had no effect on progesterone in FFL of the small or large follicles. Thyrotropin-releasing hormone did not alter FFL progesterone or E2 concentrations in any follicle size group. We conclude that the GRF and(or) TRH treatments we employed did not affect intra-ovarian IGF-I concentrations, but GRF may alter steroidogenesis of medium-sized follicles and growth of large follicles.     

Effects of frequency of recombinant porcine somatotropin administration on growth performance, tissue accretion rates, and hormone and metabolite concentrations in pigs.

Thirty-two crossbred barrows were used to determine the effects of frequency of administration of equivalent total dosages of recombinant porcine somatotropin (rpST) on growth performance, tissue accretion rates, and hormone and metabolite status of pigs. Treatments were control (buffer-injected daily), 60 micrograms/kg BW daily (4 injections/4 d), 120 micrograms/kg BW injected every other day (2 injections/4 d), or 240 micrograms/kg BW given every 4th d (1 injection/4 d). Treatments were initiated at 35 BW and continued until each pig had consumed a total of 440 Mcal of DE intake. Pigs were fed a diet that contained 16% CP, 1.2% lysine, and 3.5 Mcal of DE/kg at 85% of calculated ad libitum intake. Feed intake and rpST dose were adjusted at 8-d intervals. The 240 micrograms/kg BW treatment did not decrease appetite beyond the 15% restriction already imposed in the experimental design. Treatment groups responded to rpST in a frequency-dependent manner. Average daily gain was improved by 10, 23, and 36%, respectively, as injection frequency was increased from 1/4 to 2/4 to 4/4 d. Muscle weights were increased uniformly (15% on average) on a BW basis by all rpST treatments. Carcass (21, 42, and 63%), visceral (43, 65, and 112%), and empty body (22, 43, and 65%) protein accretion rates were increased by rpST treatment in a frequency-dependent fashion, respectively. Lipid accretion also was reduced in carcass and empty body (31% on average) by all rpST injection schemes relative to controls; however, visceral lipid accretion was increased by 59% by rpST. Protein utilization efficiency increased linearly by 24, 45, and 65% as the frequency of injection of rpST was increased from 1/4 to 2/4 to 4/4 d. Hormones and metabolites exhibited frequency-related profiles as well. These results suggest that frequency of administration greatly influences the magnitude of responsiveness to rpST and that optimal benefit would be realized by a delivery system that mimicked a daily surge, at minimum, of rpST.     

Changes in plasma estrogen, luteinizing hormone, follicle-stimulating hormone and 13,14-dihydro-15-keto-prostaglandin F2 alpha during blockade of luteolysis in pigs after human chorionic gonadotropin treatment

An injection of human chorionic gonadotropin (HCG) or estrogen on d 12 of the estrous cycle delays luteolysis in the pig. In an experiment to determine if HCG stimulated estrogen secretion, 21 cyclic pigs received one of five different amounts of HCG-(A) 0, (B) 125, (C) 250, (D) 500 or (E) 1,000 IU-as a single, im injection in 2 ml of distilled water on d 12 of the estrous cycle. Blood was collected from the jugular vein immediately before HCG injection and once daily thereafter until d 20 of the estrous cycle. Plasma progesterone, estrogen (unconjugated) and 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were quantified for pigs in all groups; luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were quantified for pigs in groups A and E. The HCG injection exerted a dose-related increase on the mean interestrus interval (groups A, B, C, D and E were 20.5, 20.2, 22.5, 31.0 and 61.4 d, respectively) and on the delay of luteolysis as measured by mean plasma progesterone on d 16 (A, B and C vs D and E, respectively, 1.9, 1.2 and 10.4 vs 34.1 and 47.1 ng/ml; P less than .05). The HCG injection caused a transitory increase in plasma estrogen from d 12 (5 to 10 pg/ml before treatment) to d 15 (35.5 pg/ml, group D) and to d 16 (90.2 pg/ml, group E) before it decreased to preinjection levels on d 17 (group D) and 18 (group E).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary intake on concentrations of insulin-like growth factor-I in plasma and follicular fluid, and ovarian function in heifers.

The objective of this study was to determine if alterations in dietary intake of heifers can influence IGF-I concentrations in plasma and(or) follicular fluid (FFL), size of follicles, and steroid concentrations in FFL (as an indicator of steroidogenic capacity). Cyclic heifers [n = 23; mean +/- SE body weight (BW) = 373 +/- 7 kg] were individually fed for 10 weeks either: a) 1.8% of BW in dry matter (DM) per d (GAIN; n = 7), b) 1.1% of BW in DM per d (MAINT; n = 8) or c) 0.7% of BW in DM per d (LOSE; n = 8). After 10 wk of treatment, heifers were ovariectomized 36-40 hr after the second injection of prostaglandin F2 alpha analog (2 injections 11 d apart), and plasma and ovaries were collected. Heifers weighed 444 +/- 13,387 +/- 8 and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at time of ovariectomy. Mean diameter of follicles greater than or equal to 10 mm was greater (P less than .05) for GAIN (15.6 mm) than for MAINT (11.0 mm) or LOSE (12.5 mm) heifers. Numbers of follicles and concentrations of IGF-I in plasma and FFL did not differ (P greater than .20) between LOSE, MAINT and GAIN heifers. Progesterone concentrations were greater (P less than .05) in small and medium follicles of GAIN than MAINT or LOSE heifers, but were unaffected by diet in large follicles. Estradiol concentrations in FFL in small, medium and large follicles were unaffected (P greater than .20) by dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in the peripheral concentrations of inhibin, follicle-stimulating hormone, luteinizing hormone, progesterone and estradiol-17beta during turnover of cystic follicles in dairy cows with spontaneous follicular cysts

Several studies have clarified that the follicular cysts degenerate and are replaced by newly growing follicles that develop into new follicular cysts without ovulation, i.e., turnover of ovarian follicular cysts in cows. However, the relativity of endocrinological changes, including the inhibin profile during turnover of spontaneous follicular cysts in dairy cows, is still unclear. In the present study, the relationship between turnover of follicular cysts and changes in the peripheral blood concentrations of progesterone (P), estradiol-17beta (E(2)), luteinizing hormone (LH), follicle stimulating hormone (FSH) and inhibin were examined in lactating dairy cows. Five cows diagnosed with follicular cysts (follicles of more than 25 mm in diameter in the absence of a corpus luteum) were investigated. Their ovarian dynamics were monitored using ultrasonography, and blood samples were collected at 2- or 3- day intervals throughout the experiment. The day when a follicle fated to become a follicular cyst reached more than 8 mm in diameter was defined as the start of a cystic follicular wave. Four of the 5 cows exhibited a similar patterns of cystic follicular changes and hormone profiles. The data from the 4 cows was used for analysis of the relationships between turnover of cystic follicles and the hormone profiles. Two or three new cystic follicular waves occurred in each cow during the experimental period. The mean diameter of the cystic follicles was more than 25 mm 13 to 15 days after the start of the cystic follicular wave, and it began to decrease 1 to 6 days before the start of the subsequent cystic follicular wave. The levels of E(2) and inhibin tended to decrease for 7 to 9 days before the start of a new cystic follicular wave and to increase concomitantly with new follicular cyst growth. The levels of FSH rose for 1 to 3 days before the start of a new cystic follicular wave. The present study clarified the relationship between FSH and inhibin during turnover of spontaneous follicular cysts in dairy cows and found that it was very similar to previous results for cows. The present results suggest that an increase in FSH secretion following a reduction in inhibin secretion triggers turnover of cystic follicles in cows with spontaneous follicular cysts.     

LH responses to chicken luteinizing hormone-releasing hormone I and II in laying,incubating, and out of lay turkey hens

An experiment was conducted to assess the relative in vivo and in vitro activities of chicken LH-RH-I and -II in laying, incubating and out-of-lay turkey hens. The highest plasma concentrations of LH were measured in laying turkey hens, whereas hypophyseal concentrations were highest in incubating hens (I) and lowest in the laying hens at the end of the laying period (EL). Hypophyseal and plasma concentrations of LH decreased with aging in laying hens (L) and the greater decrease occurred in the hypophyses. An in vitro hypophyseal acute challenge with 2-min pulses of cLHRH I or II (10⁻⁷ M) using a perifusion technique resulted in an increase in the release of LH in out-of-lay (OL) and incubating (I) hens, but not in laying (L) hens. Although both peptides elicited comparable responses in I hens, cLHRH II was more effective in OL hens. This difference was attributable to a greater amplitude of the response, whose duration was unchanged. Hypophyseal desensitization to a subsequent stimulation was observed in OL hens when the interval between stimulations was 30 min, but this did not occur at 60- or 120-min intervals. In vivo, the injection of cLHRH I or II, at doses of 10⁻⁸ and 10⁻¹⁰M/kg B.W. stimulated increases in the plasma concentrations of LH, which were initiated within 1 min of injection in OL and I hens but from 5 to 20 min postinjection in L hens. The responses were dose-related and greater immediate responses were measured with cLHRH I than with cLHRH II. Also, after the injection of cLHRH II at the 10⁻⁸ M/kg B.W. dose, the shape of the LH response consisted of an initial increase, followed by a more sustained phase during which LH concentrations were either stable (I hens) or continued to increase (L and OL hens) from 20 to 60 min after injection. In contrast, the injection of cLHRH I at doses of 10⁻⁸ or 10⁻¹⁰ M/kg or cLHRH II at a dose of 10⁻¹⁰ M/kg in I and OL hens, produced a peak of LH concentrations in plasma within 5 min and thereafter declined gradually. The difference in the in vivo responses to LHRH I and II could not be attributed to a greater potency of cLHRH II, but to a more prolonged action. In summary, the responses to both forms of chicken LH-RH varies markedly with the stage of the reproductive cycle (L, I, and OL) and differs between the in vivo and in vitro situations. Although cLHRH II may be more active than cLHRH I, controversy still surrounds its precise physiological role.     

Effect of ammonia‐generating diet on ovine serum and follicular fluid ammonia and urea levels,serum oestrogen and progesterone concentrations and granulosa cell functions

This study was undertaken to elucidate the effect of ammonia‐generating diet on serum and follicular fluid ammonia and urea levels, serum oestrogen and progesterone concentrations and granulosa cell growth and secretion parameters in ewes (Ovis aries). Ewes were fed with 14% CP diet (control) or ammonia‐generating diet or ammonia‐generating diet plus soluble sugar. The serum and follicular fluid ammonia and urea level, serum oestrogen and progesterone levels and granulosa cell (obtained from ovaries of slaughtered ewes) growth parameters and secretory activities were estimated. Ammonia‐generating diet (high‐protein diet) increased the serum ammonia and urea concentration. Supplementation of soluble sugar significantly reduced the ammonia concentration in serum with comparable levels as in control group; however, the urea level in the same group was higher than that observed in control group. Supplementation of soluble sugar significantly reduced the follicular fluid ammonia concentration; however, the level was significantly higher compared to control group. Supplementation of soluble sugar brought down the follicular fluid urea level comparable to that observed in control group. Oestrogen and progesterone levels remained unchanged in ewes fed with different types of diet. Oestrogen and progesterone secretion were significantly lowered from granulosa cells recovered from ewes fed with high ammonia‐generating diet. Low metabolic activity and high incidence of apoptosis were observed in granulosa cells obtained from ovaries of ewes fed with ammonia‐generating diet.     

Effects of exogenous estradiol-17 beta on luteinizing hormone, progesterone, and estradiol-17 beta concentrations before and after prostaglandin F2 alpha-induced termination of pregnancy and pseudopregnancy in gilts.

This study evaluated the influence of exogenous estradiol-17 beta (E2) administration on LH concentrations and the number of animals returning to estrus after the termination of pregnancy or pseudopregnancy in gilts. Gilts were mated (pregnant; n = 11) on the 1st d of estrus or received 5 mg of estradiol valerate i.m. at d 11 to 15 after the onset of estrus (pseudopregnant; n = 9). Gilts were treated with prostaglandin F2 alpha (PGF2 alpha, 15 and 10 mg) at 12-h intervals on d 44 of pregnancy or pseudopregnancy. The day of abortion or luteolysis (progesterone less than .2 ng/mL) was considered d 0. Six pregnant and four pseudopregnant gilts received s.c. an E2 capsule (24 mg of E2) on d -20 and additional E2 capsules on d -13 and -6. The E2 capsules were removed on the day after PGF2 alpha administration. Blood samples were collected at 12-h intervals from d -21 to -3, at 6-h intervals from d -2 to 21 or the onset of estrus, and at 15-min intervals for 8 h on d -2, 1, 4, 7, 10, 14, and 18. After each 8-h sampling period, gilts were treated i.v. with GnRH at .5 micrograms/kg of BW and blood samples collected at 10-min intervals for 3 h. A greater (P less than .05) proportion of sham-treated gilts than of E2-treated gilts exhibited a preovulatory-like LH surge after abortion/luteolysis. It was evident that E2 supplementation before luteolysis reduced the ability of pregnant and pseudopregnant gilts to return to estrus.