Effects of an agonist of gonadotrophin releasing hormone in cattle. I. Hormone concentrations and oestrous cycle length

Kl, Macmillan; Day, A.M.; Taufa, V.K.; Gibb, M.; Pearce, M.G.

doi:10.1016/0378-4320(85)90025-9

Cited by 58 publications

(22 citation statements)

References 18 publications

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“…On the contrary, there are reports that GnRH References treatment increased P4 concentrations [27,28]. Macmilan et al [29] found that the effect of GnRH on P 4 production varied with the stages of the estrous cycle in cows. Although a clear reason for the low lambing rate in parous ewes treated with GnRH is unknown in the present study, GnRH treatment also induces a high level of plasma estradiol-17β (E 2 ) in cows [24] and the following luteolysis induced by the high E 2 levels may be one reason for the decrease of P4 levels and the low fertility in GnRH-treated ewes.…”

Section: Discussionmentioning

confidence: 93%

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Ishida

Okada

Sebata

et al. 1999

Journal of Reproduction and Development

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Abstract.Two experiments were conducted to enhance the corpus luteum (CL) function for increasing lambing rate of ewes treated with GnRH or hCG after artificial insemination (AI) during the non-breeding season. Ewes (Experiment 1: n=102, Experiment 2: n=37) were pretreated with a controlled internal drug release dispenser (CIDR) for 12 days and 500 IU equine chorionic gonadotropin (eCG) 1 day before CIDR removal. In Experiment 1, the ewes were treated on Day 12 (Day 0=CIDR removal): 1) Group I; GnRH (100 µg), 2) Group II; hCG (500 IU), 3) Group III; 0.6% saline (2 ml) for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups. But, there was significant (P<0.01) difference in the lambing rate between parous (27%) and non-parous (72%) in Group I. On Day 17, plasma progesterone (P4) levels of Group I were significantly (P<0.01) lower than those of Group III, but on the contrary, the plasma P4 levels of Group II were significantly (P<0.01) higher than those of Group III. In Experiment 2, the ewes were treated: 1) Group I; hCG (500 IU) on Day 6, 2) Group II; hCG (500 IU) on Day 9, 3) Group III; no treatment for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups, but on Days 12 and 15, the plasma P4 levels of Groups I and II were significantly (P<0.01) higher than those of Group III. The present results indicate that a single hCG treatment on Days 6, 9 and 12 after CIDR removal stimulates CL and increased P4 concentration, but the increased P4 levels did not reflect on the fertility of treated ewes.

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Section: Discussionmentioning

confidence: 93%

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Ishida

Okada

Sebata

et al. 1999

Journal of Reproduction and Development

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“…Essa inibição se deve à alteração no desenvolvimento folicular, induzindo luteinização e, ou, atresia após sua aplicação (GUIBAULT et al, 1990;MACMILLAN et al, 1985).…”

Section: Resultsunclassified

“…A administração de buserelina, um agonista do GnRH com, aproximadamente, 40 vezes sua potência (ORY et al, 1983), resulta em concentração sérica máxima de LH duas horas após sua aplicação, quantidade suficiente para estimular a ovulação dos folículos grandes (MACMILLAN et al, 1985;McDOUGALL et al, 1995). Mensurações macroscópicas indicam que a administração de buserelina causa alteração da distribuição folicular nos ovários, diminuindo o número de folículos grandes pela indução da luteinização e, ou, 1227 COSTA et al atresia (McNATTY et al, 1981;GUIBAULT et al, 1990).…”

Section: Introductionunclassified

“…A administração de buserelina prolonga a vida útil do corpo lúteo, protegendo-o parcialmente da luteólise espontânea e prolongando o ciclo estral (HENDERSON e McNATTY, 1975;MACMILLAN et al, 1985).A buserelina, indiretamente, aumenta o número de células luteais grandes e, conseqüentemen-te, o tamanho do corpo lúteo, resultando no aumento da concentração de progesterona (TWAGIRAMUNGO et al, 1994). Parece que o aumento do número de células luteais grandes nesses animais não é devido ao efeito direto sobre o corpo lúteo, visto que não se encontraram receptores específicos para GnRH nas células luteais de bovinos (BROW e REEVES, 1983;IRELAND et al, 1990).…”

Section: Introductionunclassified

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Sincronização da onda folicular com buserelina prévia à indução da luteólise com cloprostenol em bovinos

Torres¹,

Fernandes

Junqueira³

et al. 1999

R. Bras. Zootec.

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RESUMO -Este experimento foi realizado para verificar o efeito da aplicação de diferentes doses de um análogo de GnRH (buserelina) sobre a emergência de nova onda de crescimento folicular e o número de folículos recrutados dessa onda, a formação de corpo lúteo acessório, o diâmetro do folículo dominante e do corpo lúteo espontâneo no dia da aplicação do luteolítico e subseqüente taxa de sincronização e o intervalo da aplicação de PGF 2 α à manifestação do estro. Vinte fêmeas bovinas em diestro, mestiças Holandês x Zebu e Simental x Zebu foram, distribuídas em quatro tratamentos contendo cinco animais cada. No tratamento 1, os animais receberam 4 mg IM de buserelina no dia z 0 (dia em que se iniciou o tratamento) e 150 mg de D(+) cloprostenol no dia 6. Nos tratamentos 2, 3 e 4, receberam, respectivamente, 6, 8 e 10 mg de buserelina, pela mesma via de aplicação, e 150mg de D(+) cloprostenol no dia 6. A atividade ovariana foi monitorada diariamente, com auxílio do aparelho de ultra-sonografia, do dia 0 ao estro, ou até o dia 11 pós-tratamento, naqueles animais que não responderam à prostaglandina. A aplicação de 8 ou 10 mg de buserelina em fase indeterminada do diestro, nas fêmeas bovinas mestiças, promoveu emergência de nova onda de crescimento folicular mais rápida que aplicações de 4 ou 6 mg do mesmo hormônio; enquanto os outros parâmetros avaliados não diferiram entre os animais dos tratamentos.Palavras-chave: dinâmica folicular, buserelina, cloprostenol, sincronização do estro, bovinos Follicular Wave Synchronization with Buserelin before the Luteolisis Induction with Cloprostenol in CattleABSTRACT -This experiment was carried out to verify the effect of the administration of different doses of GnRH (buserelin) analogue on the emergence of a new follicular growth wave and the number of recruited follicles from this wave, accessory corpus luteum formation, the dominant follicle diameter and the spontaneous corpus luteum on the luteolitic administration day and subsequent synchronization rate and the interval between the PGF 2 α application and the estrus manifestation. Twenty crossbreed female cattle in diestrus, crossbred Holstein x Zebu and Simental x Zebu were allotted to four treatment groups, each containing five animals. In the treatment 1 the animals received 4 mg IM. of buserelin at day 0 (day in which the treatment began) and 150 mg of D (+) Cloprostenol at day 6. In treatments 2, 3 and 4, the animals received 6, 8 and 10 mg of buserelin, respectively, by the same application way, and 150 mg of D (+) Cloprostenol at day 6. The ovarian activity was daily monitored, with the help of an ultra-sound machine, from day 0 to estrus or until day 11 on those animals, which did not answer to prostaglandin. The application of 8 or 10 mg of buserelin at an unknown phase of diestrus, in female crossbred cattle, promoted an emergence of a new follicular growth wave faster than the applications of 4 or 6 mg of the same hormones, while the other evaluated parameters did not differ among treatments.

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“…Indeed, it has been suggested that exogenous GnRH may be effecting an enhanced development and functioning of the corpora lutea (Macmillan et al 1985). Sup-port for this suggestion is provided by the association between GnRH injection al Can.…”

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confidence: 99%

The Influence of Gonadotrophin-Releasing Hormone at Estrus on Ovulation Rate and the Development of Corpora Lutea in Ewes

Kirkwood¹,

Thacker²,

Rutter³

et al. 1990

Can. J. Anim. Sci.

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EWESTwenty-two ewes received either 30 pg GnRH or saline at the onset of estrus. Blood samples were obtained on days | 7 Gay 0 : estrus) and corpora lutea recov^ered sufgicaily at day 7. There *u, no effect of GnRH on the number or weight of corpora iutea nor on the concentrations of plogestelone in either corpola lutea or plasma. GnRH rreatment caused an increase tpiO.OZl in luteal hCG binding capacity (0'66 + 0.12 vs. 0.34 + 0.12 nmol mg 'Protein).

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Effects of an agonist of gonadotrophin releasing hormone in cattle. I. Hormone concentrations and oestrous cycle length

Cited by 58 publications

References 18 publications

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Effects of GnRH and hCG Treatments for Enhancing Corpus Luteum Function to Increase Lambing Rate of Ewes Artificially Inseminated During the Non-Breeding Season.

Sincronização da onda folicular com buserelina prévia à indução da luteólise com cloprostenol em bovinos

The Influence of Gonadotrophin-Releasing Hormone at Estrus on Ovulation Rate and the Development of Corpora Lutea in Ewes

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