Control of Ovulation in Cattle With Melengestrol Acetate

Zimbelman, R. G.; Smith, L. W.

doi:10.1530/jrf.0.0110185

Cited by 71 publications

(28 citation statements)

References 4 publications

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“…In view of the findings of Zimbelman and Smith (1966), the failure of MGA in the feed to suppress heat in the first experiment was unexpected. However, a major contributing factor to this would seem to be the large particle size of the MGA used which could have resulted not only in uneven distribution of the MGA in the feed, but also in variable intake of the MGA among animals.…”

Section: Discussionmentioning

confidence: 93%

The long-term suppression of heat in cattle with implants of melengestrol acetate

Roche

Crowley

1973

Anim. Sci.

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The effectiveness of silastic rubber implants impregnated with melengestrol acetate (MGA) to suppress heat in heifers being finished for beef was tested. Nine uniparous females received MGA implants, nine received 0-5 mg MGA orally and eight similar non-treated animals served as controls for a 110-day experimental period. Based on occurrence of heat and ovarian examination during treatment and at slaughter, the silastic implants were effective in suppressing heat throughout the experimental period. The animals with implants also had a significantly higher rate of daily gain than the controls (P

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Section: Discussionmentioning

confidence: 93%

The long-term suppression of heat in cattle with implants of melengestrol acetate

Roche

Crowley

1973

Anim. Sci.

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“…Some progestational compounds include: 6-chloro-6-dehydro-17-acetoxyprogesterone (CAP) progestational properties of MGA were demonstrated by Zimbleman and Smith (1963) who maintained pregnancy in ovariectomized dairy heifers by feeding MGA. Three years later, their laboratory reported 100% suppression of estrus and ovulation in heifers fed MGA for a 16 d duration at a rate of 0.5 mg *head -1 *day -1 (Zimbleman and Smith, 1966). Feeding a progestin can be difficult, especially controlling the amount of feed intake if animal are not used to being fed from a feed bunk.…”

Section: Progestinsmentioning

confidence: 99%

The effects of varying the interval from follicular wave emergence to progestin withdrawal on follicular dynamics and the synchrony of estrus in beef cattle

Utt

Jousan

Beal

2003

Journal of Animal Science

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The objective of this experiment was to examine the effects of varying the interval from follicular wave emergence to progestin removal on follicular dynamics and the synchrony of estrus. The experimental design was a 2x2x2 factorial with GnRH or estradiol-17 beta (E 2 ) + progesterone (P 4 ), controlled internal drug-releasing device (CIDR) treatment duration, and PG or saline treatment as main effects. Cycling, Angus cows (n=49), on d 6 to 8 of the estrous cycle, were randomly assigned to receive a CIDR treatment for 7 or 9 d. Approximately half of the cows from each CIDR group received either GnRH (100 mcg) or E 2 +P 4 (1 mg E 2 + 100 mg P 4 ) at CIDR insertion. Cows in GnRH or E 2 +P 4 groups were further divided into those that received PG (37.5 mg) or saline at CIDR insertion. All cows received PG (25 mg) 1 d prior to CIDR removal. The interval from follicular wave emergence to CIDR removal was longer for cows treated with GnRH (6.6 d) or a CIDR for 9 d (6.5 d) compared to those treated with E 2 +P 4 (4.7 d) or a 7-d CIDR (4.8 d) (P < 0.05). Cows treated with PG or GnRH at CIDR insertion or a 9-d CIDR had a larger dominant follicle (DF) at CIDR removal than those treated with saline, E 2 +P 4 , or a 7-d CIDR. (P < 0.07). Altering the interval from wave emergence to progestin removal created differences in size of the DF at CIDR removal but did not affect the synchrony of estrus.

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“…No início de sua utilização, aplicavam-se injeções diárias de 100 mg de progestágeno por 14 dias, sendo que após o término desta sequência de injeções, ocorria a sincronização do estro e da ovulação em uma grande proporção de animais tratados 3 . Algum tempo após a introdução da utilização de progestágenos veio ao mercado o acetato de melengesterol (MGA), um tipo farmacológico administrado por via oral que substituía o corpo lúteo 4 . Segundo Odde 5 , a progesterona, assim como os progestágenos, atua suprimindo o estro e a ovulação, mas induz cio de baixa fertilidade quando em tratamentos longos, acima de 14 dias, devendo-se assim associar ao protocolo um agente luteolítico para possibilitar o encurtamento do período de tratamento.…”

Section: Introductionunclassified

Avaliação da reutilização de implantes contendo progestágenos na taxa de prenhez em vacas de corte

Maluf

Pires

Susin

et al. 2010

Braz. J. Vet. Res. Anim. Sci.

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Duzentos e vinte e uma vacas (78 paridas com bezerros entre 40 e 90 dias de idade e as demais secas vazias) Nelore (Bos taurus indicus) e mestiças Charolês (Bos taurus taurus) foram utilizadas para avaliar a reutilização de implantes auriculares de silicone impregnados com progestágenos para controle farmacológico do ciclo estral e ovulação sobre a taxa de prenhez. Os tratamentos experimentais consistiram de três protocolos para sincronização do cio e inseminação artificial em tempo fixo (IATF). No tratamento 1 (T1; n = 73) as vacas receberam um implante auricular de Crestar® (3 mg de norgestomet); no tratamento 2 (T2; n = 75) as vacas receberam um implante auricular de Crestar® já utilizado previamente; e no tratamento 3 (T3; n = 73) as vacas receberam dois implantes auriculares de Crestar® também utilizados previamente. Além dos implantes, as vacas receberam aplicação intramuscular (i.m) 2 mL de progesterona (25 mg/mL) + 2 mL de benzoato de estradiol i.m (1 mg/mL) no momento da colocação dos implantes. Os implantes foram removidos após oito dias junto a uma aplicação de 2,0 mL de Preloban® i.m (150 µg de D-cloprostenol). Após 24 h da remoção do implante, aplicou-se 1 mL de Estrogin® i.m (1 mg de benzoato de estradiol). A IATF foi realizada 54-56 h após a retirada dos implantes. Não houve diferença na taxa de prenhez das vacas, sendo 39,72%, 34,21% e 36,98% para os tratamentos T1, T2 e T3, respectivamente. A reutilização de implantes com progestágeno (Crestar®) não alterou a taxa de prenhez de vacas aptas à reprodução.

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Control of Ovulation in Cattle With Melengestrol Acetate

Cited by 71 publications

References 4 publications

The long-term suppression of heat in cattle with implants of melengestrol acetate

The long-term suppression of heat in cattle with implants of melengestrol acetate

The effects of varying the interval from follicular wave emergence to progestin withdrawal on follicular dynamics and the synchrony of estrus in beef cattle

Avaliação da reutilização de implantes contendo progestágenos na taxa de prenhez em vacas de corte

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