Serum Gonadotropins After Gonadotropin-Releasing Hormone Injection in Bulls Subjected to Spacial Restriction (original) (raw)
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Annales de Biologie Animale Biochimie Biophysique, 1979
The LH and testosterone release after a single injection (0.25 mg) of Gonadoliberin (LRH) were studied in a total of 23 bulls before and about puberty. Both LH and testosterone were measured by radioimmunoassay of jugular vein blood samples taken at frequent intervals. LRH caused release of LH at all ages but the magnitude of the LH increase in response to LRH was significantly higher at 3 and 5 months (mean total response 4.3 f J-g/ml x 150 min) than at older ages (3.1 pg/ml x 150 min.). By contrast the mean total response of testosterone to LRH increases from very low levels (0.07 fJ-g/ml x 150 min) at 3 months of age to about 0.65 !,g/ml x 150 min. between the ages of 7 and 13 months. The mean LH responses vary significantly among individuals and the intra-class correlation coefficient r is 0.3 (p < 0.02). These results provide evidence of two distinct periods prior to puberty with regard to LH and testosterone release in response to LRH : one before 7 months of age during which LH release is very sensitive to LRH and the testosterone low, and the other from 7 months until after puberty, when no more changes in the magnitude of the responses can be seen. However, the individual magnitude of the response during the second period does not seem to be independent of that seen in the former period. Introduction. A further understanding of pituitarytestes relationships in the young bull might be achieved by critical determination of pituitary gonadotropic and gonadal hormone concentrations at various ages prior to or around the time of puberty. Puberty, defined as the release of the first spermatozoa, occurs in this species at about the eigth or ninth month after birth (Ortavant et al., 1977). The reprints should be requested to : Laboratoire d'Hormonologie, UNCEIA, 13, rue Jouet, 94700 Maisons-Alfort, France.
Reproduction, 2003
Administration of GnRH agonist for an extended period inhibits pulsatile LH release but enhances testicular function of bulls. The mechanism whereby long-term administration of GnRH agonist enhances testosterone concentration in the blood of bulls has not been determined. The aim of this study was to determine whether chronic treatment with the GnRH agonist, azagly-nafarelin, increases blood concentrations of LH and FSH in prepubertal bulls. Two different doses of the GnRH agonist were administered via Alzet mini-osmotic pumps for 28 days. Blood samples were collected at 20 min intervals for 24 h at days 2, 13 and 25 of treatment. Agonist-treated groups had reduced testosterone pulse frequency (P < 0.05) and increased mean and basal concentrations of testosterone (P < 0.05) compared with untreated control bulls. Basal LH concentrations were higher in agonist-treated bulls during all three periods (P < 0.05) and overall (1 ng ml −1 higher, compared with control bulls; P < 0.001). Frequency of LH pulses in the agonist-treated groups was reduced to less than one pulse in 24 h. Agonist-treated bulls tended to have (P < 0.10) or had (P < 0.05) a slight but significant increase in blood FSH concentration. In conclusion, the higher blood testosterone concentration in bulls after prolonged treatment with GnRH agonist may result, at least in part, from changes in the testes induced by enhanced basal concentration of LH.
Animal Production, 1992
Forty-six Simmental × British Friesian bull calves were allocated to six treatment groups. In four groups (each of eight animals) half the animals were given a prime injection of gonadotropin-hormone-releasing-hormone (GnRH) either as the decapeptide or as an octapeptide (residues 3 to 10) conjugated to egg albumen. Prime injection times were at 3, 4, 5 or 6 months of age. All animals were boosted with a GnRH conjugate, similar to that used for the prime injection, at 8 months. At 8 months, six other animals were surgically castrated while the remaining eight were left as untreated bull controls. Weight gain and consumption of a barley-based diet offeredad libitumwere recorded for individual animals. Blood samples were taken at a minimum of fortnightly intervals and the serum analysed for antibody titre against GnRH, testosterone and insulin-like growth factor 1 (IGF-1). Animals were slaughtered at 12 months and chemical analyses performed on the dissectible material of the 10th rib...
Journal of Animal Science, 2005
The objective was to compare testis characteristics of Zebu bulls treated with the GnRH agonist, deslorelin, at different times and for different durations during their development. An additional objective was to determine the usefulness of a stain for the transcription factor GATA-binding protein 4 (GATA-4) as a specific marker for Sertoli cell nuclei in cattle. Bulls (54) were allocated to nine groups (n = 6) and received s.c. deslorelin implants as follows: G1 = from birth to 3 mo of age; G2 = from 3 to 6 mo; G3 = from 6 to 9 mo; G4 = from 9 to 12 mo; G5 = from birth to 15 mo; G6 = from 3 to 15 mo; G7 = from 6 to 15 mo; G8 = from 12 to 15 mo; and G9 (control) = no implant. Bulls were castrated at 19 mo of age. Paraffin sections (10 m) were subjected to quantitative morphometry and GATA-4 immunohistochemistry. At castration, all bulls in the control group (6/6) had attained puberty (scrotal circumference ≥ 28 cm), whereas a smaller proportion (P < 0.05) had reached puberty in G2 (2/5) and G6 (1/ 6). Bulls in G2 and G6 also had a lesser (P < 0.05) testis
Theriogenology, 2009
We hypothesized that: (i) repeated GnRH treatments would increase the magnitude and duration of the LH surge and would increase progesterone (P4) concentrations after ovulation; and (ii) the release of pituitary LH would be greater in response to larger doses of GnRH. In Experiment 1, ovary-intact cows were given an intravaginal P4 (1.9 g) insert (CIDR) for 10 d and 500 mg cloprostenol (PGF) at CIDR removal to synchronize estrus. On Days 7 or 8 after estrus, cows received two PGF treatments (12 h apart) and 100 mg GnRH at 36 (Control), 36 and 38 (GnRH38), or 36 and 40 h (GnRH40) after the first PGF. Mean plasma LH concentration (ng/mL) was greater (P < 0.05) in GnRH38 (8.8 AE 1.1) than in Control (5.1 AE 1.3), with that in GnRH40 (5.8 AE 1.3) being intermediate. Although the duration (h) of the LH surge was longer in GnRH40 (8.0 AE 0.4) than in either GnRH38 (P < 0.05; 7.0 AE 0.3) or Control (P < 0.09; 7.1 AE 0.4), mean postovulatory P4 (ng/mL) was greater (P < 0.01) in Control (4.2 AE 0.7) than in GnRH38 (2.9 AE 0.6) or GnRH40 (3.0 AE 0.7) cows. In Experiment 2, ovariectomized cows were given a CIDR for 10 d and 2 mg of estradiol cypionate im at CIDR insertion. Thirty-six hours after CIDR removal, cows received, 50, 100, or 250 mg of GnRH. Cows given 250 mg GnRH released more LH (9.4 AE 1.4 ng/mL) than those given 50 or 100 mg (6.1 AE 1.3 and 5.4 AE 1.4 ng/mL, respectively), and had an LH surge of longer duration than those given 50 mg (6.8 AE 0.4 vs. 5.1 AE 0.3 h). In summary, ovary-intact cows in the GnRH38 group had greater mean and peak LH concentrations, but subsequent plasma P4 concentrations were lower than in Control cows. Ovariectomized cows given 250 mg GnRH had a greater pituitary release of LH. #
Annales de recherches vétérinaires. Annals of veterinary research, 1982
Two experiments were conducted with multiparous cycling dairy cows in the post-partum period. They were assigned randomly to GnRH treatment or to saline injection (control groups) during the mid-luteal phase. In experiment 1, seven cows were treated with five consecutive injections of GnRH (100 micrograms i.m.) at hourly intervals and four controls were similarly treated with saline. In experiment 2, (seven treated and three control cows) treatment consisted of 10 i.m. injections of 500 micrograms GnRH or saline twice a day (8 h and 18 h) over a period of 120 h (five days). In both experiments injections started on day 12 of the oestrous cycle. LH immediately following treatment and subsequent progesterone concentrations for the next 35 days were assayed in peripheral blood samples. Most of the cows were inseminated at the oestrus following the treatment period. Profiles of progesterone after GnRH-treatment varied slightly but transiently between days two and four post-treatment in ...
Aggressive behavior is reduced in bulls actively immunized against gonadotropin-releasing hormone
Journal of animal science, 2003
The purpose of this research was to compare the frequency of aggressive behavior's in beef bulls actively immunized against gonadotropin-releasing hormone relative to contemporary nonimmunized control bulls and surgically castrated steers. Eight males were assigned to each ofthese treatments in each of 4 yr. Immunized males were treated with a GnRH-keyhole-limpet hemocyanin (KLH) conjugate at approximately 4 mo of age. A secondary (booster) immunization was administered at 12 mo. Steers were castrated at 4 mo of age. Animals in each treatment in each year were housed as a single group prior to testing. At approximately 16 mo of age, each group of eight animals was placed in a 10- x 16-m enclosure for 20 min on five occasions at 2 to 3 d intervals. An observer recorded butts initiated by each animal as well as participation in bouts of sparring. Relative to control bulls, immunocastration reduced the frequency of butts initiated (P < 0.05) and participation in sparring bouts (...
Journal of Animal Science, 1983
Two homologous radioimmunoassays for bovine follicle stimulating hormone (bFSH) were utilized in comparing the differential regulation of FSH and luteinizing hormone (LH) in response to ovariectomy or administration of gonadal steroids in cattle. There appeared to be significant LH cross-reactivity in one of the bFSH systems (bFSH-HS-2-17), but not in the other (bFSH-BP3). Concentrations of FSH in plasma measured by these two systems suggested both qualitative and quantitative differences. Following ovariectomy in heifers, LH concentrations in plasma were increased by 7.5 h, while FSH (measured in the bFSH-BP3 system) was not significantly elevated until 18 h. Administration of 200/~g of estradiol-17~ to ovariectomized heifers inhibited levels of FSH in plasma but large doses of testosterone (100 mg), androstenedione (400 mg) and dihydrotestosterone (800 mg) had no effect. Similarly, LH was not affected by the androgens, while estradiol induced LH surges, leading to increased mean LH concentrations. In contrast to the results in heifers, LH concentrations in plasma from steers were inhibited by administration of androgens as well as by estradiol. In steers, FSH
Biology of Reproduction, 2003
Our hypothesis was that luteal function, as determined by plasma progesterone concentrations, and corpus luteum (CL) size is enhanced in cattle administered an agonist of GnRH when the CL is developing as compared with administration of an agonist when the CL is fully functional. Cattle were chronically administered a GnRH agonist, azagly-nafarelin, from Day 3 to Day 21 (D3) or Day 12 to Day 21 (D12) or served as untreated control females (Day 0 ؍ behavioral estrus). Blood samples were serially collected on Days 7 and 14 to evaluate LH secretory patterns and twice daily to measure plasma progesterone. Ultrasonographic examinations were conducted daily to record the area of the CL. CL size and plasma progesterone concentrations were both enhanced in the D3 group as compared with the control group. Progesterone was increased in the D12 group on Days 16 and 17 as compared with the control females. Treatment with GnRH agonist increased basal and mean LH concentrations in both D3 and D12 groups as compared with the controls. We rejected our hypothesis because chronic administration of a GnRH agonist increased plasma progesterone when administered both when the CL was developing and when it was fully functional. The enhanced luteal function was likely due to increased basal LH.