RESUMO

We performed two experiments in high milk-producing Holstein cows. First, we evaluated the repeatability of the antral follicle count (AFC) - where all follicles were ≥2 mm in diameter - during the days of the ovulation synchronization protocol for timed artificial insemination (TAI) in dairy cows (n = 20). In the second study we investigated the follicular dynamics and Doppler ultrasonography in cows with low (≤15 follicles, n = 9) and high (≥25 follicles, n = 9) AFC, and measured progesterone (P4) concentrations during CL evaluation. In addition, the diameter of the preovulatory follicle, area of blood flow of the preovulatory follicle, CL area, and CL blood flow were compared between groups with high and low AFC. Ultrasound examinations were performed during the days of the protocol and 10 days after ovulation to assess the CL. The constancy of the AFC was analyzed by calculating the repeatability. Parametric variables were analyzed using the t-test, and nonparametric variables were analyzed using the Mann-Whitney test (P ≤ 0.05). The repeatability of the AFC on different days of the protocol was 0.98. Cows with low AFC showed a greater diameter of the preovulatory follicle (16 ± 0.3 vs. 15 ± 0.4 mm), blood flow area of the preovulatory follicle (17.3 ± 2.3 vs. 8.1 ± 3.2 mm2), CL area (579.1 ± 16.9 vs. 405.8 ± 21.2 mm2), area of CL perfusion (97.1 ± 9.4 vs. 68.3 ± 5.2 mm2), as well as higher P4 levels (3.1 ± 0.2 vs. 2.2 ± 0.2 ng/mL). In high milk-producing Holstein cows, the AFC has high repeatability on different days of the TAI protocol, and cows with a low AFC show larger preovulatory follicles and CLs with greater perfusion, in addition to greater P4 concentrations in comparison to those cows with a high AFC.

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The aim of this study was to verify the efficiency and ovulation time after the administration of different inducers for synchronization of ovulation in beef cows. One hundred and eight non-lactating cows were distributed into the control group (CG; untreated; n=28), estradiol benzoate (EB) group (EBG; n=28); 17 beta-estradiol (17ßE) group (17ßEG; n=28), and deslorelin (DES) group (DESG; n=24). On day minus 11 (D-11) of the protocol, the CG underwent application of cloprostenol and ultrasound examination (US); on D0, progesterone (P4) was inserted plus EB; on D7, cloprostenol was applied; on D9, P4 was removed and cloprostenol plus 400 IU of equine chorionic gonadotropin (eCG) was injected. The EBG was subjected to treatment identical to that of the CG, except on D10, when the cows received EB. The 17ßE was subjected to the same protocol used in the CG except for the administration of 17ßE on D10. And, the DESG was subjected to the same treatment as the CG, except on D10, when the group received DES acetate. Twelve hours after the administration of EB, 17ßE and DES, ovarian US were performed every 6 hours. The preovulatory follicle (POF) diameters measured before ovulation were 19.5; 14.7; 18.7 and 19.8 mm respectively for CG, EBG, 17ßEG and DESG; and the time intervals between inducer application and ovulation were 20.2; 18.9; 21.0 and 22.5 hours respectively. In conclusion, all ovulation inducers were efficient in promoting ovulation; the inducers caused ovulation between 18.9 and 22.5 hours; EB promoted ovulation in a shorter time (P<0.05); 17ßE and DES showed greater variation in application/ovulation time between groups.

O objetivo do estudo foi verificar a eficiência e a ovulação após a administração de diferentes indutores para a sincronização da ovulação em vacas de corte. Cento e oito vacas não-lactantes foram distribuídas em grupo controle (GC; não tratadas; n=28); grupo benzoato de estradiol (BE) (GBE; n=28); grupo 17 beta-estradiol (17ßE) (G17ßE; n=28) e grupo deslorelina (DES) (GDES; n=24). No dia menos 11 (D-11) do protocolo, o GC recebeu cloprostenol e exame ultrassonográfico (US); ao D0, dispositivo de progesterona (P4) foi inserido mais BE; ao D7, cloprostenol foi aplicado; ao D9, a P4 foi removida e cloprostenol mais 400 UI de gonadotrofina coriônica equina (eCG) foi injetada. O GBE foi submetido a tratamento idêntico ao do GC, exceto ao D10, quando as vacas receberam BE. o G17ßE foi submetido ao mesmo protocolo usado no CG exceto pela administração de 17ßE ao D10. E, o GDES foi submetido ao mesmo tratamento que o CG, exceto ao D10, quando o grupo recebeu o acetato de DES. Doze horas após a administração de BE, 17ßE e DES, US ovarianos foram realizados a cada 6 horas. O diâmetro do folículo pré-ovulatório (FPO) medido antes da ovulação foi de 19,5; 14,7; 18,7 e 19,8 mm respectivamente para GC, GBE, G17ßE e GDES; e o intervalo de tempo entre a aplicação do indutor e ovulação foi 20,2; 18,9; 21;0 e 22,5 horas respectivamente. Em conclusão, todos os indutores da ovulação foram eficientes em promover a ovulação; os indutores acarretaram ovulação entre 18,9 e 22,5 horas; o BE promoveu a ovulação em menor espaço de tempo (P<0,05); 17ßE e DES demonstraram maior variação em aplicação/tempo de ovulação entre os grupos.

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Effects were evaluated in Bos indicus cows of eCG and FSH on follicular growth, estrous expression, and pregnancy per artificial insemination (P/AI) as a result of fixed-time artificial insemination (TAI). In Experiment 1, extent of timing-of-ovulation synchronization among cows was evaluated after imposing an estrogen/progesterone-based treatment regimen. At progesterone device removal (D8), cows were administered: eCG, or FSH or served as untreated Controls. In Experiment 2, percentage of cows P/AI was evaluated when the Experiment 1-treatment regimen was imposed. On D10, all cows were artificially inseminated. In Experiment 3, cows were assigned to two treatment groups (Control and eCG) on D8 to evaluate percentage of cows P/AI and estrous expression. In Experiment 1, follicular dynamics were similar among treatment groups. In Experiment 2, follicular growth was greater (P = 0.0001) with the eCG treatment. There was an interaction of treatment × parity (P = 0.007) on percentage of cows P/AI. There was a greater percentage of primiparous cows P/AI in the eCG-treated than Control and FSH-treated cows. There was a greater percentage of eCG-treated multiparous cows pregnant as a result of TAI than Control cows. There was an interaction of treatment × parity (P = 0.005) on P/AI in Experiment 3, in which the eCG effect was more pronounced in primiparous cows. Treatment with FSH, therefore, was not as effective as eCG in stimulation of follicular growth or enhancing percentage of cows pregnant as a result of TAI. Physiological effects of eCG, however, were also more evident in primiparous cows.

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Timed artificial insemination (TAI) has boosted the use of conventional artificial insemination (CAI) by employing hormonal protocols to synchronize oestrus and ovulation. This study aimed to evaluate the efficiency of a hormonal protocol for TAI in mares, based on a combination of progesterone releasing intravaginal device (PRID), prostaglandin (PGF2α ) and human chorionic gonadotropin (hCG); and compare financial costs between CAI and TAI. Twenty-one mares were divided into two groups: CAI group (CAIG; n = 6 mares; 17 oestrous cycles) and TAI group (TAIG; n = 15 mares; 15 oestrous cycles). The CAIG was subjected to CAI, involving follicular dynamics and uterine oedema monitoring with ultrasound examinations (US), and administration of hCG (1,600 IU) when the dominant follicle (DF) diameter's ≥35 mm + uterine oedema + cervix opening. The AI was performed with fresh semen (500 × 106 cells), and embryo was recovered on day 8 (D8) after ovulation. In TAI, mares received 1.9 g PRID on D0. On D10, PRID was removed and 6.71 mg dinoprost tromethamine was administered. Ovulation was induced on D14 (1,600 IU of hCG) regardless of the DF diameter's, and AI was performed with fresh semen (500 × 106 cells). On D30 after AI, pregnancy was confirmed by US. The pregnancy rate was 80.0% in TAIG and 82.3% in CAIG (p > .05). The TAI protocol resulted in 65% reduction in professional transport costs, and 40% reduction in material costs. The TAI was as efficient as CAI, provided reduction in costs and handlings, and is recommended in mares.

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Avaliaram-se diferentes momentos de aplicação da gonadotrofina coriônica equina (eCG) em protocolos de inseminação artificial em tempo fixo (IATF) para vacas de leite. Foram utilizadas 76 fêmeas, as quais receberam, no dia zero (D0) do protocolo, dispositivos intravaginais de progesterona, sendo esses retirados no D9, e os animais foram, então, distribuídos aleatoriamente em três tratamentos: T1 - aplicação de eCG no momento da retirada dos dispositivos; T2 e T3 - aplicação de eCG 48h e 24h antes da retirada dos dispositivos, respectivamente. No D10 os animais receberam 1mg de GnRH, e a IATF foi realizada 52 horas após a retirada do implante. Não houve diferença (P>0,05) para intervalo entre a retirada do implante à ovulação (72,56±3,92h), o diâmetro do maior folículo no D9 (10,88±1,49mm), o diâmetro do folículo ovulatório (15,15±1,16mm) e do segundo maior folículo (7,49±0,52mm), a taxa de crescimento folicular (1,38±0,04mm/dia), a taxa de ovulação (96,67%), o intervalo entre diâmetro final e inicial do folículo dominante (73,49±3,84h), a área de corpo lúteo (2,27±0,43cm²), a porcentagem de CL no ovário direito (53,00%) e no esquerdo (26,33%) e a taxa de gestação (33,33%). O momento da aplicação da eCG não influenciou na eficiência do protocolo. Recomenda-se a utilização da eCG no momento da retirada do implante por otimização do manejo.(AU)

Different times of application of equine chorionic gonadotropin (eCG) in Fixed-Time Artificial Insemination (FTAI) protocols for dairy cows were evaluated. A total of 76 females were used, which received intravaginal progesterone devices on day zero (D0) of the protocol, which were withdrawn on D9, and the animals were then randomly distributed in three treatments: T1- application of eCG at the time of device withdrawal; T2 and T3 - application of eCG 48h and 24h before withdrawal of the devices, respectively. On D10 the animals received 1mg of GnRH and the FTAI was carried out 52 hours after the removal of the implant. There was no difference (P>0.05) for interval from implant removal to ovulation (72.56±3.92h), diameter of the largest follicle of D9 (10.88±1.49mm), diameters of ovulatory follicle (15.15±1.16mm) and of the second largest follicle (7.49±0.52mm), follicle growth rate (1.38±0.04mm/day), ovulation rate (96.67%), interval between final diameter and initial diameter of dominant follicle (73.49±3.84h), corpus luteum area (2.27±0.43cm²), percentage of CL in right ovary (53.00%) and in left ovary (26.33%) and pregnancy rate (33.33%). The time of the application of eCG did not influence the efficiency of the protocol. We recommend the use of eCG at the time of the removal of the implant for management optimization.(AU)

Assuntos

RESUMO

Avaliaram-se diferentes momentos de aplicação da gonadotrofina coriônica equina (eCG) em protocolos de inseminação artificial em tempo fixo (IATF) para vacas de leite. Foram utilizadas 76 fêmeas, as quais receberam, no dia zero (D0) do protocolo, dispositivos intravaginais de progesterona, sendo esses retirados no D9, e os animais foram, então, distribuídos aleatoriamente em três tratamentos: T1 - aplicação de eCG no momento da retirada dos dispositivos; T2 e T3 - aplicação de eCG 48h e 24h antes da retirada dos dispositivos, respectivamente. No D10 os animais receberam 1mg de GnRH, e a IATF foi realizada 52 horas após a retirada do implante. Não houve diferença (P>0,05) para intervalo entre a retirada do implante à ovulação (72,56±3,92h), o diâmetro do maior folículo no D9 (10,88±1,49mm), o diâmetro do folículo ovulatório (15,15±1,16mm) e do segundo maior folículo (7,49±0,52mm), a taxa de crescimento folicular (1,38±0,04mm/dia), a taxa de ovulação (96,67%), o intervalo entre diâmetro final e inicial do folículo dominante (73,49±3,84h), a área de corpo lúteo (2,27±0,43cm²), a porcentagem de CL no ovário direito (53,00%) e no esquerdo (26,33%) e a taxa de gestação (33,33%). O momento da aplicação da eCG não influenciou na eficiência do protocolo. Recomenda-se a utilização da eCG no momento da retirada do implante por otimização do manejo.(AU)

Different times of application of equine chorionic gonadotropin (eCG) in Fixed-Time Artificial Insemination (FTAI) protocols for dairy cows were evaluated. A total of 76 females were used, which received intravaginal progesterone devices on day zero (D0) of the protocol, which were withdrawn on D9, and the animals were then randomly distributed in three treatments: T1- application of eCG at the time of device withdrawal; T2 and T3 - application of eCG 48h and 24h before withdrawal of the devices, respectively. On D10 the animals received 1mg of GnRH and the FTAI was carried out 52 hours after the removal of the implant. There was no difference (P>0.05) for interval from implant removal to ovulation (72.56±3.92h), diameter of the largest follicle of D9 (10.88±1.49mm), diameters of ovulatory follicle (15.15±1.16mm) and of the second largest follicle (7.49±0.52mm), follicle growth rate (1.38±0.04mm/day), ovulation rate (96.67%), interval between final diameter and initial diameter of dominant follicle (73.49±3.84h), corpus luteum area (2.27±0.43cm²), percentage of CL in right ovary (53.00%) and in left ovary (26.33%) and pregnancy rate (33.33%). The time of the application of eCG did not influence the efficiency of the protocol. We recommend the use of eCG at the time of the removal of the implant for management optimization.(AU)

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This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 µg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

RESUMO

This study aimed to evaluate the effect of recombinant bovine somatotropin (bST) in combination with progesterone (P4) and estradiol benzoate (EB) on ovarian follicular dynamics using a protocol for estrus and ovulation synchronization in crossbred Bos taurus taurus cows. Twenty-four non-lactating multiparous cows were randomly assigned to two groups: the recombinant bovine somatotropin group (GbST; n = 11) received an intravaginal P4 device (1.5 g), estradiol benzoate (EB = 1.0 mg IM), bST (500 mg SC), and an ovarian ultrasonography (US) on day zero (d0 = beginning of the study); d-cloprostenol (150 µg, IM), US, and P4 removal on d8; 1.0 mg of EB (IM) on d9; and US on d10 and d15. On the other hand, to the control group (GC; n = 13), the same protocol as the GbST was applied, except for the non-receipt of bST on d0. The follicles were measured and evaluated on d0, d8, and d10, as were the corpora lutea (CL) on d15 (using ultrasonography). The effect of the two treatments (GbST vs. GC) on the follicle size, CL (F-test), and ovulation rate (logistic regression) were evaluated. The GbST showed a greater follicle diameter on d10 (14.5 mm) than the GC (12.1 mm; P < 0.03), as well as a greater diameter of CL on d15 (19.7 vs. 16.9 mm, P < 0.01). In addition, in the former, the ovulation rate (90.9 vs. 69.2%, P = 0.09) was observed to be greater. It was concluded that the combination of bST, P4, and EB in synchronization for estrus and ovulation protocols significantly increased the diameter of the preovulatory follicle, produced a higher follicular growth rate, and a greater diameter of the corpus luteum. Additionally, there was a higher percentage of cows with ovulation compared to the group that did not receive bST.

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RESUMO

Diversos hormônios podem ser utilizados em protocolos que visam otimizar biotécnicas reprodutivas como a inseminação artificial (IA) e inseminação artificial em tempo fixo (IATF), que exigem controle preciso do ciclo estral e da ovulação. Alguns hormônios possuem ação central no eixo hipotalâmico-hipofisário, como o hormônio liberador de gonadotrofinas (GnRH) e os ésteres de estradiolcomo o benzoato (BE) e o cipionato de estradiol (CE), enquanto outros como a gonadotrofina coriônica humana (hCG) e o hormônio luteinizante (LH) apresentam ação local, a nível ovariano. Atualmente os protocolos mais utilizados para indução da ovulação utilizam GnRH e estrógenos. Recentemente, foi demonstrado que as prostaglandinas possuem efeitos positivos na indução do processo ovulatório, mas seu mecanismo de ação não está totalmente esclarecido. A presente revisão tem por objetivo abordar os principais indutores da ovulação utilizados em protocolos para controle do ciclo estral em bovinos, relatando o período de ocorrência das ovulações após a sua aplicação.(AU)

Several hormones may be used in protocols aimed to optimize reproductive biotechniques such as artificial insemination (AI) and fixed-timed artificial insemination (FTAI) which require precise control of the estrous cycle and the ovulation. Some hormones act on the hypothalamic-pituitary axis, such as the gonadotrophin releasing hormone (GnRH) and estradiol esters such as estradiol benzoate (EB) and cypionate (EC), whereas others act directly on the ovaries, such as human chorionic gonadotrophin (hCG) and luteinizing hormone (LH). Currently, the most commonly used protocols for ovulation induction use GnRH or estrogen. Prostaglandins have recently been shown to have positive effects on induction of the ovulatory process, but their mechanism of action is not fully understood. The present review aims to address the main ovulation inducers used in protocols to control the estrous cycle in cattle, emphasizing the period between their administration and the occurrence of ovulation.(AU)

Assuntos

RESUMO

Diversos hormônios podem ser utilizados em protocolos que visam otimizar biotécnicas reprodutivas como a inseminação artificial (IA) e inseminação artificial em tempo fixo (IATF), que exigem controle preciso do ciclo estral e da ovulação. Alguns hormônios possuem ação central no eixo hipotalâmico-hipofisário, como o hormônio liberador de gonadotrofinas (GnRH) e os ésteres de estradiolcomo o benzoato (BE) e o cipionato de estradiol (CE), enquanto outros como a gonadotrofina coriônica humana (hCG) e o hormônio luteinizante (LH) apresentam ação local, a nível ovariano. Atualmente os protocolos mais utilizados para indução da ovulação utilizam GnRH e estrógenos. Recentemente, foi demonstrado que as prostaglandinas possuem efeitos positivos na indução do processo ovulatório, mas seu mecanismo de ação não está totalmente esclarecido. A presente revisão tem por objetivo abordar os principais indutores da ovulação utilizados em protocolos para controle do ciclo estral em bovinos, relatando o período de ocorrência das ovulações após a sua aplicação.

Several hormones may be used in protocols aimed to optimize reproductive biotechniques such as artificial insemination (AI) and fixed-timed artificial insemination (FTAI) which require precise control of the estrous cycle and the ovulation. Some hormones act on the hypothalamic-pituitary axis, such as the gonadotrophin releasing hormone (GnRH) and estradiol esters such as estradiol benzoate (EB) and cypionate (EC), whereas others act directly on the ovaries, such as human chorionic gonadotrophin (hCG) and luteinizing hormone (LH). Currently, the most commonly used protocols for ovulation induction use GnRH or estrogen. Prostaglandins have recently been shown to have positive effects on induction of the ovulatory process, but their mechanism of action is not fully understood. The present review aims to address the main ovulation inducers used in protocols to control the estrous cycle in cattle, emphasizing the period between their administration and the occurrence of ovulation.

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Three experiments were conducted to evaluate the effect of estradiol cypionate (ECP) and amount of progesterone in the intravaginal device (PID) on synchronization of estrus and ovulation, follicular dynamics, luteal dynamics and function and on pregnancy rate in beef cows treated with fixed-time artificial insemination (FTAI) based protocols. In Experiment 1, we evaluated the synchronization of ovulation using 1mg of ECP at PID removal (day 8 after PID insertion) or 1mg of estradiol benzoate (EB) 24h later, in cows treated with 0.558 or 1g of progesterone (P4). The final subgroups were: 0.558g+ECP: n=10; 0.558g+EB: n=11; 1g+ECP: n=10; 1g+EB: n=10. Ovarian ultrasonic examinations were performed to detect the dominant follicle and ovulation. There was no effect of treatments on the diameter of dominant follicle at any time, and on the mean interval to estrus and to ovulation (P>0.05); however, ECP treated cows had scattered distribution of estrus (P<0.03) and ovulation (P<0.03). In Experiment 2, cows received the following treatments: 0.558gP4+ECP: n=52; 0.558gP4+EB: n=52; 1gP4+ECP: n=50; 1gP4+EB: n=52; and FTAI. Pregnancy rate did not differ (P>0.05) between progesterone content (0.558g: 52.9%, 55/104; 1g: 56.9%, 58/102) but differed between estradiol esters (P<0.05; ECP: 48.9%, 49/102; EB: 61.5%, 64/104). In Experiment 3, cows received: 0.558gP4+ECP: n=55; 0.558gP4+EB: n=53; 1gP4+ECP: n=54; 1gP4+EB: n=53; and FTAI. Pregnancy rate did not differ (P>0.05) between progesterone content (0.558g: 48.1%, 52/108; 1g: 53.3%, 57/107) and estradiol esters (ECP: 47.7%, 52/109; EB: 53.8%, 57/106). In conclusion, ECP administration at device removal and progesterone content of PID has no influence on the synchronization of estrus, follicular dynamics, luteal dynamics and function. However, ECP administration affected the synchronization of ovulation and pregnancy rate in non-suckling beef cows, but did not affected pregnancy rate in suckling beef cows. Future studies should evaluate the distribution of ovulations in suckling Bos taurus beef cows.

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The objective of the present study was to assess the effect of administration of Melengestrol Acetate (MGA® Premix) after FTAI, on the conception rate in lactating Nelore breed cows. Experiment I, assessed the effect of administration of 2.28 g MGA/cow/day, from day 13 (D13) until day 18 (D18) after FTAI. The cow were divided into two groups, Group I (n=83, control) that cows were submitted just to FTAI and Group II (n=104, treated) that cows received MGA after FTAI. Experiment II, assessed the effect of administration of 2.28g MGA/cow/day, from day 5 (D5) until day 10 (D10) after FTAI. The cow were divided into two groups, Group I (n=94, control) that cows were submitted just to FTAI and Group II (n=100, treated) that cows received MGA after FTAI. Gestation was diagnosed in both experiments 45 days after FTAI. The conception rates were analyzed by Qui-Square test. In experiment I, The conception rates were 42,16% for control group and 50,0% for treated group (p>0,05). In Experiment II, the conception rate of control group (47,87%) was higher than treated group (28,0%). It was conclude that administration of MGA®Premix from D13 until D18 after FTAI didnt affect the conception rate. However, when administered from D5 until D10, reduced the conception rate in lactating Nelore breed cows.(AU)

Objetivou-se com este estudo avaliar o efeito do fornecimento de Acetato de Melengestrol (MGA®Premix) após IATF (inseminação artificial em tempo fixo), sobre a taxa de concepção em vacas paridas da raça Nelore. Experimento I, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia 13 (D13) ao dia 18 (D18) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=83, controle) que foi realizado apenas IATF e Grupo II (n=104, tratado) que foi fornecido o MGA após a IATF. Experimento II, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia cinco (D5) ao dia 10 (D10) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=94, controle) que foi realizado apenas IATF e Grupo II (n=100, tratado) que foi fornecido o MGA após a IATF. O diagnóstico de gestação foi realizado 45 dias após a IATF em ambos os experimentos. As taxas de concepção foram comparadas pelo teste de Qui-quadrado. No Experimento I, as taxas de concepção foram de 42,16% para o grupo controle e 50,0% para o grupo tratado. No Experimento II, a taxa de concepção do grupo controle (47,87%) foi significativamente maior do que o grupo tratado (28,0%). Conclui-se que o fornecimento de MGA®Premix, administrado do D13 ao D18 após a IATF não afetou a taxa concepção. Entretanto, quando fornecido do D5 ao D10, reduziu a taxa de concepção em vacas Nelore paridas.(AU)

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RESUMO

The objective of the present study was to assess the effect of administration of Melengestrol Acetate (MGA® Premix) after FTAI, on the conception rate in lactating Nelore breed cows. Experiment I, assessed the effect of administration of 2.28 g MGA/cow/day, from day 13 (D13) until day 18 (D18) after FTAI. The cow were divided into two groups, Group I (n=83, control) that cows were submitted just to FTAI and Group II (n=104, treated) that cows received MGA after FTAI. Experiment II, assessed the effect of administration of 2.28g MGA/cow/day, from day 5 (D5) until day 10 (D10) after FTAI. The cow were divided into two groups, Group I (n=94, control) that cows were submitted just to FTAI and Group II (n=100, treated) that cows received MGA after FTAI. Gestation was diagnosed in both experiments 45 days after FTAI. The conception rates were analyzed by Qui-Square test. In experiment I, The conception rates were 42,16% for control group and 50,0% for treated group (p>0,05). In Experiment II, the conception rate of control group (47,87%) was higher than treated group (28,0%). It was conclude that administration of MGA®Premix from D13 until D18 after FTAI didn't affect the conception rate. However, when administered from D5 until D10, reduced the conception rate in lactating Nelore breed cows.

Objetivou-se com este estudo avaliar o efeito do fornecimento de Acetato de Melengestrol (MGA®Premix) após IATF (inseminação artificial em tempo fixo), sobre a taxa de concepção em vacas paridas da raça Nelore. Experimento I, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia 13 (D13) ao dia 18 (D18) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=83, controle) que foi realizado apenas IATF e Grupo II (n=104, tratado) que foi fornecido o MGA após a IATF. Experimento II, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia cinco (D5) ao dia 10 (D10) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=94, controle) que foi realizado apenas IATF e Grupo II (n=100, tratado) que foi fornecido o MGA após a IATF. O diagnóstico de gestação foi realizado 45 dias após a IATF em ambos os experimentos. As taxas de concepção foram comparadas pelo teste de Qui-quadrado. No Experimento I, as taxas de concepção foram de 42,16% para o grupo controle e 50,0% para o grupo tratado. No Experimento II, a taxa de concepção do grupo controle (47,87%) foi significativamente maior do que o grupo tratado (28,0%). Conclui-se que o fornecimento de MGA®Premix, administrado do D13 ao D18 após a IATF não afetou a taxa concepção. Entretanto, quando fornecido do D5 ao D10, reduziu a taxa de concepção em vacas Nelore paridas.

RESUMO

The objective of the present study was to assess the effect of administration of Melengestrol Acetate (MGA® Premix) after FTAI, on the conception rate in lactating Nelore breed cows. Experiment I, assessed the effect of administration of 2.28 g MGA/cow/day, from day 13 (D13) until day 18 (D18) after FTAI. The cow were divided into two groups, Group I (n=83, control) that cows were submitted just to FTAI and Group II (n=104, treated) that cows received MGA after FTAI. Experiment II, assessed the effect of administration of 2.28g MGA/cow/day, from day 5 (D5) until day 10 (D10) after FTAI. The cow were divided into two groups, Group I (n=94, control) that cows were submitted just to FTAI and Group II (n=100, treated) that cows received MGA after FTAI. Gestation was diagnosed in both experiments 45 days after FTAI. The conception rates were analyzed by Qui-Square test. In experiment I, The conception rates were 42,16% for control group and 50,0% for treated group (p>0,05). In Experiment II, the conception rate of control group (47,87%) was higher than treated group (28,0%). It was conclude that administration of MGA®Premix from D13 until D18 after FTAI didnt affect the conception rate. However, when administered from D5 until D10, reduced the conception rate in lactating Nelore breed cows.

Objetivou-se com este estudo avaliar o efeito do fornecimento de Acetato de Melengestrol (MGA®Premix) após IATF (inseminação artificial em tempo fixo), sobre a taxa de concepção em vacas paridas da raça Nelore. Experimento I, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia 13 (D13) ao dia 18 (D18) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=83, controle) que foi realizado apenas IATF e Grupo II (n=104, tratado) que foi fornecido o MGA após a IATF. Experimento II, avaliou-se o efeito do fornecimento de 2,28g de MGA/ vaca/ dia, do dia cinco (D5) ao dia 10 (D10) após a IATF. As vacas foram divididas em dois grupos, sendo o Grupo I (n=94, controle) que foi realizado apenas IATF e Grupo II (n=100, tratado) que foi fornecido o MGA após a IATF. O diagnóstico de gestação foi realizado 45 dias após a IATF em ambos os experimentos. As taxas de concepção foram comparadas pelo teste de Qui-quadrado. No Experimento I, as taxas de concepção foram de 42,16% para o grupo controle e 50,0% para o grupo tratado. No Experimento II, a taxa de concepção do grupo controle (47,87%) foi significativamente maior do que o grupo tratado (28,0%). Conclui-se que o fornecimento de MGA®Premix, administrado do D13 ao D18 após a IATF não afetou a taxa concepção. Entretanto, quando fornecido do D5 ao D10, reduziu a taxa de concepção em vacas Nelore paridas.

Assuntos

RESUMO

The aim of the present study was to study the effect of parity on the efficacy of an Ovsynch protocol in buffalo. B uffalo heifers (HE ; n = 8 ) and cow s (BC ; n = 9 ) were used to monitor ovarian follicular dynamics and evaluate serum progesterone profile s during this protocol . A t otal of 385 control buffalo heifers (CHE ; n = 219 ) and cows (CBC ; n = 1 66 ) were used to compare conception rates follo wing the application of this protocol . The heifers and cows were cycling . All treated animals were injected with GnRH on day 0, PGF2 α on day 7 , GnRH on day 9 and artificially inseminated 1 6 h later. Ovarian changes were monitored daily using ultrasound and serum progesterone (P4) evaluated in the investigated animals . All heifers and 5 cows had follicles >8 mm at the first G n RH injection. The first GnRH injection resulted in ovulation in 7 /8 HE ( 8 7 . 5 %) and 5 /9 BC ( 55.5 %) . Following the second GnRH injection , ovulation occurred in 100 % of HE and 88.8 % of BC. Ovulation occurred earlier in BC (10.4 ± 7 .6 h) following the second GnRH injection than in HE ( 22.6 ± 5.4 h). A verage P4 concentrations of HE were higher than those of BC on day 7 (P < 0.04) . Conception r ates were 62.5% ( 429 / 686 ) in HE , 59.8 % ( 131/219 ) in CHE, 22.7 % ( 62/273 ) in BC and 59.6 % ( 99/166 ) in CBC. The present findings suggested that low conception rate s in buffalo cows , compared to heifers , may be attribut ed to earl ier ovulation and a less functi onal CL.(AU)

Assuntos

RESUMO

The aim of the present study was to study the effect of parity on the efficacy of an Ovsynch protocol in buffalo. B uffalo heifers (HE ; n = 8 ) and cow s (BC ; n = 9 ) were used to monitor ovarian follicular dynamics and evaluate serum progesterone profile s during this protocol . A t otal of 385 control buffalo heifers (CHE ; n = 219 ) and cows (CBC ; n = 1 66 ) were used to compare conception rates follo wing the application of this protocol . The heifers and cows were cycling . All treated animals were injected with GnRH on day 0, PGF2 α on day 7 , GnRH on day 9 and artificially inseminated 1 6 h later. Ovarian changes were monitored daily using ultrasound and serum progesterone (P4) evaluated in the investigated animals . All heifers and 5 cows had follicles >8 mm at the first G n RH injection. The first GnRH injection resulted in ovulation in 7 /8 HE ( 8 7 . 5 %) and 5 /9 BC ( 55.5 %) . Following the second GnRH injection , ovulation occurred in 100 % of HE and 88.8 % of BC. Ovulation occurred earlier in BC (10.4 ± 7 .6 h) following the second GnRH injection than in HE ( 22.6 ± 5.4 h). A verage P4 concentrations of HE were higher than those of BC on day 7 (P < 0.04) . Conception r ates were 62.5% ( 429 / 686 ) in HE , 59.8 % ( 131/219 ) in CHE, 22.7 % ( 62/273 ) in BC and 59.6 % ( 99/166 ) in CBC. The present findings suggested that low conception rate s in buffalo cows , compared to heifers , may be attribut ed to earl ier ovulation and a less functi onal CL.

Assuntos

RESUMO

O uso da Inseminação Artificial (IA) em búfalos pode ser limitado por fatores relacionados à dificuldade de identificação do estro e à determinação do melhor momento para a realização desta biotecnologia. Neste contexto, estudos foram conduzidos para a elaboração de protocolos que permitam o uso da IA sem a necessidade de detecção do estro, ou seja, em tempo fixo (IATF). O conhecimento da dinâmica folicular nessa espécie possibilitou o desenvolvimento de protocolos para controlar as fases folicular e luteínica do ciclo estral e, por fim, a ovulação. Foi verificado que a emergência da onda de crescimento folicular pode ser sincronizada pelos tratamentos com GnRH ou com progesterona/progestágeno (P4) associados ao estradiol (E2). O tratamento com dispositivos/implantes de P4 e com PGF2α controlam a fase luteínica. Ao final do protocolo, sob baixos níveis de progesterona, realiza-se a indução da ovulação com GnRH, ou hCG, ou LH ou E2. Em búfalas inseminadas em tempo fixo o protocolo GnRH/PGF2α/GnRH (conhecido como Ovsynch) tem apresentado resultados satisfatórios (~50% de taxa de prenhez) em animais ciclando durante a estação reprodutiva (outono e inverno). A utilização de P4 associado ao E2, PGF2α, eCG e GnRH possibilita a realização da IATF com aceitáveis taxas de concepção (~50% de taxa de prenhez) em búfalas em anestro sincronizadas fora da estação reprodutiva (primavera e verão). A combinação destes tratamentos de sincronização da ovulação permite o uso da inseminação artificial durante todo o ano, possibilitando o melhoramento genético e a distribuição da concepção e dos partos conforme a demanda do mercado. (AU)

Assuntos

RESUMO

O uso da Inseminação Artificial (IA) em búfalos pode ser limitado por fatores relacionados à dificuldade de identificação do estro e à determinação do melhor momento para a realização desta biotecnologia. Neste contexto, estudos foram conduzidos para a elaboração de protocolos que permitam o uso da IA sem a necessidade de detecção do estro, ou seja, em tempo fixo (IATF). O conhecimento da dinâmica folicular nessa espécie possibilitou o desenvolvimento de protocolos para controlar as fases folicular e luteínica do ciclo estral e, por fim, a ovulação. Foi verificado que a emergência da onda de crescimento folicular pode ser sincronizada pelos tratamentos com GnRH ou com progesterona/progestágeno (P4) associados ao estradiol (E2). O tratamento com dispositivos/implantes de P4 e com PGF2α controlam a fase luteínica. Ao final do protocolo, sob baixos níveis de progesterona, realiza-se a indução da ovulação com GnRH, ou hCG, ou LH ou E2. Em búfalas inseminadas em tempo fixo o protocolo GnRH/PGF2α/GnRH (conhecido como Ovsynch) tem apresentado resultados satisfatórios (~50% de taxa de prenhez) em animais ciclando durante a estação reprodutiva (outono e inverno). A utilização de P4 associado ao E2, PGF2α, eCG e GnRH possibilita a realização da IATF com aceitáveis taxas de concepção (~50% de taxa de prenhez) em búfalas em anestro sincronizadas fora da estação reprodutiva (primavera e verão). A combinação destes tratamentos de sincronização da ovulação permite o uso da inseminação artificial durante todo o ano, possibilitando o melhoramento genético e a distribuição da concepção e dos partos conforme a demanda do mercado.

Assuntos