Repeatability of LH responses by lambs to monthly challenge with synthetic gonadotrophin releasing hormone (GnRH)

Tyrrell, RN; Starr, B.G.; Restall, B.J.; Donnelly, John

doi:10.1016/0378-4320(80)90043-3

Cited by 8 publications

(6 citation statements)

References 14 publications

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“…The repeatability of GnRH-induced LH concentration between presynchronization and Ovsynch assessments was low (0.16) when evaluated in all cows (P = 0.02). Our finding is in agreement with previous reports in small (Tyrrell et al, 1980) and large ruminants (Fajersson et al, 1999). Tyrrell et al (1980) reported poor and nonsignificant repeatability estimates (0.10 to 0.20) for LH release when prepubertal ram and ewe lambs (n = 15 per sex) were repeatedly challenged with exogenous GnRH treatments for 7 consecutive months starting from approximately 9 wk of age.…”

Section: Discussionsupporting

confidence: 93%

“…However, the induced LH surge response after exogenous GnRH administration may be a more useful endocrine parameter for investigating variability and repeatability. Previous studies reported a poor and nonsignificant repeatability for GnRH-induced LH responses when ram and ewe lambs (Tyrrell et al, 1980; n = 15 for each sex) and beef cows (Fajersson et al, 1999;n = 18) were repeatedly challenged with exogenous GnRH treatments. However, small sample sizes and variable concentrations of P4 might have contributed to nonsignificant repeatability estimates.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the variability and repeatability of gonadotropin-releasing hormone–induced luteinizing hormone responses in dairy cows within a synchronized ovulation protocol

Gobikrushanth

Dutra

Bruinjé

et al. 2017

Journal of Dairy Science

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The primary objective was to determine the variability and repeatability of GnRH-induced LH responses. The secondary objective was to evaluate the associations among plasma LH, FSH, estradiol (E2), and progesterone (P4) concentrations. One hundred lactating Holstein cows (35 primiparous, 65 multiparous) were initially subjected to a presynchronization protocol (d 0, PGF; d 3, GnRH) followed 7 d later by Ovsynch (d 10, GnRH; d 17, PGF; 56 h later, GnRH) and timed artificial insemination 16 h after the last GnRH. Blood samples were collected immediately before the GnRH injection of presynchronization and the second GnRH of Ovsynch to determine plasma concentrations of LH, FSH, and P4. A second blood sample was collected 2 h after each of the above GnRH injections to determine GnRH-induced LH and FSH concentrations. Plasma concentrations of E2 were also determined in samples collected immediately before the second GnRH of Ovsynch. Cows that (1) had higher LH concentrations at 0 h than at 2 h after GnRH, (2) showed an ongoing spontaneous LH surge, (3) did not respond to GnRH, and (4) had P4 ≥ 0.5 ng/mL at GnRH of presynchronization and the second GnRH of Ovsynch were excluded from the analysis. The variability (coefficient of variation) and repeatability [between animal variance/(within animal variance + between animal variance)] of GnRH-induced LH response were determined from samples collected 2 h after the GnRH of presynchronization and the second GnRH of Ovsynch. The associations among plasma LH, FSH, E2, and P4 were determined at the second GnRH of Ovsynch. Mean (±SEM) LH concentrations before GnRH were 0.5 ± 0.04 and 0.6 ± 0.03 ng/mL, whereas mean LH concentrations 2 h after GnRH were 9.8 ± 1.0 and 12.1 ± 0.8 ng/mL at GnRH of presynchronization and the second GnRH of Ovsynch, respectively. The variability of GnRH-induced LH was 76.1 and 52.1% at GnRH of presynchronization and the second GnRH of Ovsynch, respectively. The repeatability estimate for GnRH-induced LH concentration between GnRH of presynchronization and Ovsynch assessments was 0.10. Plasma concentrations of LH were positively associated with FSH and E2 (r = 0.61 and 0.30, respectively) and negatively associated with P4 (r = -0.46) at the second GnRH of Ovsynch. In summary, GnRH-induced LH responses were highly variable and unrepeatable, and LH concentrations were positively associated with FSH and E2 and negatively associated with P4.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Characterization of the variability and repeatability of gonadotropin-releasing hormone–induced luteinizing hormone responses in dairy cows within a synchronized ovulation protocol

Gobikrushanth

Dutra

Bruinjé

et al. 2017

Journal of Dairy Science

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“…Even though the differences between genotypes in the LH response to GnRH, they did not suffice to induce clear differences between genotypes in the testicular response, in terms of T secretion. The effect of GnRH dose on LH secretion was significant and the response was always in a dose-dependent manner, which agrees with previous similar studies (30,31) . Testosterone response was also dose-dependent, which suggests that in developing lambs the testes are able to detect the different LH concentrations induced by GnRH, and release T accordingly.…”

Section: Conclusiones E Implicacionessupporting

confidence: 82%

“…A pesar de que existieron diferencias entre genotipos en la respuesta de LH a la GnRH, éstas no fueron suficientes para inducir claras diferencias entre genotipos en la respuesta testicular, en términos de secreción de T. El efecto de la dosis de GnRH sobre la secreción de LH fue significativo y la respuesta fue siempre de una manera dosis dependiente, lo que concuerda con estudios similares anteriores (30,31) . La respuesta de la testosterona también fue dosis dependiente, lo que sugiere que en los corderos en desarrollo, los testículos son capaces de detectar las diferentes concentraciones de LH inducidas por GnRH, y liberar T consecuentemente.…”

Section: Discussionunclassified

Development of the endocrine reproductive axis in hair breed ram lambs

Montiel-Olguín

Ávila

Amezcua

et al. 2016

Rev. Mex. Cienc. Pecu.

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RESUMENLos objetivos fueron caracterizar los perfiles de LH y testosterona (T) y la respuesta a GnRH en corderos de pelo. Estudio 1: se utilizaron corderos Blackbelly (n=4), Pelibuey (n=5), Blackbelly x Pelibuey (Cruzas; n=8). A las 2, 4, 8, 12, 16, 20 y 24 semanas de edad, se obtuvieron muestras de sangre cada 15 min durante 6 h, para caracterizar los perfiles de LH y T. No hubo diferencia entre genotipos a ninguna edad, para ninguna variable de LH y T (P>0.05); el efecto de la edad fue significativo (P<0.05): la concentración promedio de LH fue menor en la semana 2 (P<0.05), alcanzó el valor más alto en la 12, y disminuyó en la 16 (P<0.05). La concentración promedio de T aumentó constantemente entre 2 y 24 semanas (P<0.05). Estudio 2: se utilizaron corderos Blackbelly (n=4), Pelibuey (n=4), Cruzas (n=4). A las mismas edades, los corderos se desafiaron con GnRH (3, 9, 27 ng•kg -1 peso) y se obtuvieron muestras de sangre entre -15 y 180 min. En las semanas 8 y 12, la respuesta de LH fue mayor en los corderos Pelibuey, en comparación con Blackbelly. La respuesta de T tendió a ser diferente entre genotipos (P<0.10), con Blackbelly mostrando la menor respuesta. En conclusión, el desarrollo de los perfiles de LH y T no fue diferente entre genotipos, pero los corderos Pelibuey presentaron mayor capacidad de respuesta a GnRH en las semanas 8 y 12; es necesario determinar si estas diferencias tienen implicaciones sobre la capacidad reproductiva de los animales adultos.PALABRAS CLAVE: Blackbelly, Pelibuey, LH, Testosterona, Desarrollo sexual. ABSTRACTThe objectives were to characterize the profiles of LH and testosterone (T) and the response to GnRH administration in hair ram lambs. Study 1: seventeen lambs were used: Blackbelly (n=4), Pelibuey (n=5), Blackbelly x Pelibuey (Crossbred; n=8). At 2, 4, 8, 12, 16, 20 and 24 wk of age, blood samples were collected every 15 min for 6 h, to characterize LH and T profiles. There was no significant difference between genotypes at any age, for any variable of LH and T profiles (P>0.05). The effect of age was significant (P<0.05): mean LH concentration was lower on wk 2 (P<0.05), achieved the highest value on wk 12, and decreased on wk 16 (P<0.05). Mean T concentration increased steadily between wk 2 and 24 (P<0.05). Study 2: twelve lambs were used: Blackbelly (n=4), Pelibuey (n=4), Crossbred (n=4). At the same ages, lambs were challenged with GnRH (3, 9, 27 ng•kg -1 BW) and blood samples were obtained between -15 and 180 min from GnRH administration. On wk 8 and 12, LH response to GnRH was greater in Pelibuey, as compared with Blackbelly. Testosterone response tended to be different between genotypes (P<0.10), with Blackbelly showing the smallest response. In conclusion, the sexual endocrine development, as evaluated by the non-stimulated LH and T profiles, was not different among genotypes; however, Pelibuey elicited the greatest responsiveness to GnRH administration at 8 and 12 wk of age. Whether or not such differences have implications on the reproductive capacity of the adul...

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“…This inhibition was absent in adult rats. There is also some evidence that female sheep have a changing response to LHRH during early development (Tyrell, Starr, Restall & Donnelly, 1980).…”

Section: Discussionmentioning

confidence: 98%

Pituitary response to LHRH, LH pulsatility and plasma melatonin and prolactin changes in ewe lambs treated with melatonin implants to delay puberty

Kennaway¹,

Peek²,

Gilmore³

et al. 1986

Reproduction

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Prepubertal ewe lambs were treated with empty or filled melatonin implants. The implants were placed s.c. at birth and pituitary responsiveness to various doses of LHRH, LH/FSH pulsatility and prolactin and melatonin secretion were examined at 10, 19, 28, 36 and 45 weeks of age. Control animals (N = 10) showed no consistent alteration in pituitary responsiveness to LHRH during development. Ewes treated with melatonin (N = 10) had puberty onset delayed by 4 weeks (P less than 0.03) but no effect of melatonin on LH or FSH response to LHRH injection was observed at any stage of development. In the control and melatonin-treated ewe lambs the responses to LHRH injection were lower during darkness than during the day at all stages of development. No consistent differences in LH or FSH pulsatility were observed between treatment groups or during development. Prolactin concentrations, however, failed to decrease at the time of puberty (autumn) in the melatonin-treated group. Melatonin-treated ewe lambs maintained normal rhythmic melatonin production which was superimposed on a higher basal concentration and showed the same increase in melatonin output with age as the control ewes. These results indicate that the delayed puberty caused by melatonin implants is not due to decreased pituitary responsiveness to LHRH or to dramatic changes in basal LH or FSH secretion.

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Repeatability of LH responses by lambs to monthly challenge with synthetic gonadotrophin releasing hormone (GnRH)

Cited by 8 publications

References 14 publications

Characterization of the variability and repeatability of gonadotropin-releasing hormone–induced luteinizing hormone responses in dairy cows within a synchronized ovulation protocol

Characterization of the variability and repeatability of gonadotropin-releasing hormone–induced luteinizing hormone responses in dairy cows within a synchronized ovulation protocol

Development of the endocrine reproductive axis in hair breed ram lambs

Pituitary response to LHRH, LH pulsatility and plasma melatonin and prolactin changes in ewe lambs treated with melatonin implants to delay puberty

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