In vitro sperm characteristics and in vivo fertility of sex-sorted and conventional semen in suckled Nelore cows at a traditional schedule for timed-AI with estrus detection / Características espermáticas in vitro e fertilidade in vivo de sêmen convencional e sexado em vacas Nelore pósparto submetidas à IATF tradicional com detecção de estro

The aim of this study was to assess in vitro sperm characteristics and pregnancies/AI (P/AI) of conventional and sex-sorted semen at timed-AI of suckled, multiparous Nelore cows. All cows (n=348) were submitted to a traditional estradiol/progesterone (P4)-based protocol. At 48h after P4-device removal, the estrous behavior was recorded, and AI was performed with conventional or sex-sorted semen from two bulls. The following sperm assessments were performed: CASA, Hyposmotic Test, sperm morphometry and chromatin structure by TB staining. P/AI were reduced (P<0.001) for sex-sorted compared to conventional semen in cows expressing estrus (27vs47%) or not (11vs.37%). Membrane integrity (Bull1: 30.3±9.6 vs. 52.3±12.4%, P=0.01; Bull2: 24.5±3.0 vs. 48.7±1.6%, P=0.006) and sperm concentration (Bulll: 23.2±0.6 vs. 43.0±0.8x10 sperm/mL, P<0.001; Bull2: 25.1+2.8 VS. 42.1±0.7x10 sperm/mL; P<0.001) were reduced in sex-sorted compared to conventional semen, for both bulls. Total and progressive motility were reduced in sex-sorted semen for Bull1 (TM: 49.7±15.9 vs. 94.9±1.9%, P=0.007; PM: 16.7±3.4 vs. 44.1±13.2%, P=0.009) and no differences were detected for Bull2 (TM: 45.0±17.5 vs. 68.2±19.1%, P=0.098; PM: 12.8±4.7 vs. 30.0±13.0%, P=0.065). Sperm ellipticity from sex-sorted was lower than conventional semen for Bull2 (0.306±0.01 vs. 0.342±0.02, P=0.02) and no difference was detected for Bull1 (0.332±0.01 vs. 0.330±0.01, P=0.55). Reduced in vivo fertility was observed for sex-sorted semen, regardless of estrous behavior. In vitro sperm quality of sex-sorted semen was compromised for both bulls, but differently affected for each sire.

O estudo teve como objetivo avaliar características espermáticas in vitro e a taxa de concepção (TC) de sêmen convencional e sexado em um programa de IATF tradicional de vacas Nelore pós-parto. Todas as vacas (n=348) foram submetidas ao mesmo protocolo de IATF à base de estradiol e de progesterona. Após 48 horas da retirada do implante, foi determinada a expressão de estro dos animais e a IA foi realizada com sêmen convencional e sexado de dois touros Angus. As seguintes características espermáticas foram avaliadas: análise computadorizada do sêmen, teste hiposmótico, morfometria espermática e estrutura cromatinica por meio da coloração com azul de toluidina. A TC foi menor (P<0,001) para sêmen sexado comparado ao convencional, em vacas que expressaram estro (27 vs. 47%) e que não apresentaram estro (11 vs. 37%). A integridade da membrana plasmática (Touro 1: 30,319,6 vs. 52,3+12,4%, P=0,010; Touro 2: 24,5+3,0 vs. 48,7±1,6%, P=0,006) e a concentração espermática (Touro 1: 23,2±0,6 vs. 43,0±0,8x10 sperm/mL, P<0,001; Touro 2: 25,1+2,8 vs. 42,1 +0,7x10'sperm/mL, P<0,001) foram menores no sêmen sexado comparado ao convencional, para ambos os touros. Motilidades total e progressiva foram menores no sêmen sexado comparado ao convencional para o Touro 1 (MT: 49,7±15,9 vs. 94,9±1,9%, P=0,007; MP: 16,7+3,4 vs. 44,1+13,2%, P=0,009), enquanto diferenças não foram detectadas no Touro 2 (MT: 45,0±17,5 vs. 68,2±19,1%, P=0,098; MP: 12,8±4,7 vs. 30,0±13,0%, P=0,065). Elipticidade espermática do sêmen sexado foi menor do que do sêmen convencional no Touro 2 (0,306±0,01 vs. 0,342±0,02, P=0,020), mas não houve diferença no Touro 1 (0,332±0,01 vs. 0,330±0,01, P=0,552). Reduzida fertilidade in vivo foi observada para o sêmen sexado em relação ao convencional, independentemente da expressão de cio das vacas. A qualidade seminal in vitro do sêmen sexado foi comprometida para ambos os touros, mas diferentemente afetada para cada reprodutor.

Assessment of different in vitro sperm challenges and in vivo fertility of bovine semen batches / Avaliação de diferentes desafios espermáticos in vitro e da fertilidade in vivo de partidas de sêmen bovino

The aim of this work was to submit sperm cells to different laboratory challenges and to compare in vitro results with in vivo semen fertility. Four different batches from the same Brangus bull were used in a timed-AI program of 332 Brangus cows. Each batch (B) was submitted to the following procedure: semen sample was thawed at 36°C for 30 seconds (control). Sperm motility parameters, plasma membrane integrity, sperm morphology, and concentration were assessed. Then, an aliquot of thawed sample was incubated in a water bath at 45°C for 40 min (thermal challenge group; TCG) and another aliquot was centrifuged at 500 xg (Percoll gradient 45%/90%) for 15 min (centrifugation challenge group; CCG). Centrifuged semen was also submitted to another thermal challenge, being incubated (water bath) at 45°C for 40 min (centrifugation + thermal challenge group; CTCG). At the end of each challenge (CCG, TCG, and CTCG), the same laboratory tests used for control group were repeated. The following conception rates (CR) were observed for each batch: B1 = 48.9% (44/90); B2 = 44.2% (23/52); B3 = 55.5% (40/72); B4 = 43.2% (51/118); (p < 0.10). In the lab, B3 presented higher (p ≤ 0.05) progressive motility (PM) than B4 after thawing (control group) and after all sperm challenges (TCG, CCG, and CTCG). However, despite B3 and B4 having demonstrated a similar percentage of plasma membrane integrity (PMI) to the control group (B3 = 66.7 ± 1.3 and B4 = 65.2 ± 3.3), B3 demonstrated higher (P ≤ 0.05) percentage of PMI (37.2 ± 2.5) than B4 (26.7 ± 3.3) after passing through the most stressing in vitro challenge (CTCG). The semen batch presenting the highest resistance to in vitro challenges was the one that presented a trend for higher in vivo fertility, suggesting that submitting semen samples to laboratory challenges may be an interesting alternative for selecting batches with greater field fertility.(AU)

O objetivo deste estudo foi estressar células espermáticas em diferentes desafios laboratoriais e comparar os resultados in vitro com a fertilidade in vivo do sêmen. Quatro partidas de um mesmo touro Brangus foram utilizadas em um programa de IATF de 332 vacas Brangus. Cada partida foi submetida ao seguinte procedimento: a amostra de sêmen foi descongelada a 36°C por 30 segundos (grupo controle). Foram avaliados parâmetros de motilidade espermática (CASA), integridade da membrana plasmática (PMI), morfologia e concentração espermática. Em seguida, uma alíquota da amostra descongelada foi incubada em banho-maria a 45°C durante 40 minutos (grupo de desafio térmico, TCG) e outra alíquota foi centrifugada a 500 xg (gradiente de Percoll 45%/90%) durante 15 min (grupo desafio de centrifugação, CCG). Uma aliquota do sêmen centrifugado foi ainda submetida ao desafio térmico, sendo incubado a 45°C durante 40 min (grupo de desafio térmico + centrifugação, CTCG). No final de cada desafio (CCG, TCG e CTCG), os mesmos testes laboratoriais utilizados para o grupo de controle foram realizados. A seguinte taxa de concepção (CR) foi observada para cada partida (B): B1 = 48,9% (44/90), B2 = 44,2% (23/52), B3 = 55,5% (40/72) e B4 = 43,2% (51/118); (P < 0,10). No laboratório, B3 apresentou maior (P ≤ 0,05) motilidade progressiva (PM) do que B4 logo após o descongelamento (grupo controle) e após todos os desafios laboratoriais (TCG, CCG e CTCG). Porém, apesar de B3 e B4 demonstrarem similar porcentagem de PMI no grupo controle (B3 = 66,7 ± 1,3 e B4 = 65,2 ± 3,3), B3 apresentou maior (P ≤ 0,05) PMI (37,2 ± 2,5%) do que B4 (26,7 ± 3,3%) após passar pelo maior desafio laboratorial (CTCG). A partida seminal que in vitro apresentou maior resistência aos desafios laboratoriais foi a mesma que apresentou tendência para maior fertilidade in vivo. Assim, sugere-se que submeter amostras seminais a desafios laboratoriais pode ser uma alternativa interessante para selecionar partidas com maior fertilidade a campo.(AU)

Assessment of different in vitro sperm challenges and in vivo fertility of bovine semen batches / Avaliação de diferentes desafios espermáticos in vitro e da fertilidade in vivo de partidas de sêmen bovino

The aim of this work was to submit sperm cells to different laboratory challenges and to compare in vitro results with in vivo semen fertility. Four different batches from the same Brangus bull were used in a timed-AI program of 332 Brangus cows. Each batch (B) was submitted to the following procedure: semen sample was thawed at 36°C for 30 seconds (control). Sperm motility parameters, plasma membrane integrity, sperm morphology, and concentration were assessed. Then, an aliquot of thawed sample was incubated in a water bath at 45°C for 40 min (thermal challenge group; TCG) and another aliquot was centrifuged at 500 xg (Percoll gradient 45%/90%) for 15 min (centrifugation challenge group; CCG). Centrifuged semen was also submitted to another thermal challenge, being incubated (water bath) at 45°C for 40 min (centrifugation + thermal challenge group; CTCG). At the end of each challenge (CCG, TCG, and CTCG), the same laboratory tests used for control group were repeated. The following conception rates (CR) were observed for each batch: B1 = 48.9% (44/90); B2 = 44.2% (23/52); B3 = 55.5% (40/72); B4 = 43.2% (51/118); (p < 0.10). In the lab, B3 presented higher (p ≤ 0.05) progressive motility (PM) than B4 after thawing (control group) and after all sperm challenges (TCG, CCG, and CTCG). However, despite B3 and B4 having demonstrated a similar percentage of plasma membrane integrity (PMI) to the control group (B3 = 66.7 ± 1.3 and B4 = 65.2 ± 3.3), B3 demonstrated higher (P ≤ 0.05) percentage of PMI (37.2 ± 2.5) than B4 (26.7 ± 3.3) after passing through the most stressing in vitro challenge (CTCG). The semen batch presenting the highest resistance to in vitro challenges was the one that presented a trend for higher in vivo fertility, suggesting that submitting semen samples to laboratory challenges may be an interesting alternative for selecting batches with greater field fertility.(AU)

O objetivo deste estudo foi estressar células espermáticas em diferentes desafios laboratoriais e comparar os resultados in vitro com a fertilidade in vivo do sêmen. Quatro partidas de um mesmo touro Brangus foram utilizadas em um programa de IATF de 332 vacas Brangus. Cada partida foi submetida ao seguinte procedimento: a amostra de sêmen foi descongelada a 36°C por 30 segundos (grupo controle). Foram avaliados parâmetros de motilidade espermática (CASA), integridade da membrana plasmática (PMI), morfologia e concentração espermática. Em seguida, uma alíquota da amostra descongelada foi incubada em banho-maria a 45°C durante 40 minutos (grupo de desafio térmico, TCG) e outra alíquota foi centrifugada a 500 xg (gradiente de Percoll 45%/90%) durante 15 min (grupo desafio de centrifugação, CCG). Uma aliquota do sêmen centrifugado foi ainda submetida ao desafio térmico, sendo incubado a 45°C durante 40 min (grupo de desafio térmico + centrifugação, CTCG). No final de cada desafio (CCG, TCG e CTCG), os mesmos testes laboratoriais utilizados para o grupo de controle foram realizados. A seguinte taxa de concepção (CR) foi observada para cada partida (B): B1 = 48,9% (44/90), B2 = 44,2% (23/52), B3 = 55,5% (40/72) e B4 = 43,2% (51/118); (P < 0,10). No laboratório, B3 apresentou maior (P ≤ 0,05) motilidade progressiva (PM) do que B4 logo após o descongelamento (grupo controle) e após todos os desafios laboratoriais (TCG, CCG e CTCG). Porém, apesar de B3 e B4 demonstrarem similar porcentagem de PMI no grupo controle (B3 = 66,7 ± 1,3 e B4 = 65,2 ± 3,3), B3 apresentou maior (P ≤ 0,05) PMI (37,2 ± 2,5%) do que B4 (26,7 ± 3,3%) após passar pelo maior desafio laboratorial (CTCG). A partida seminal que in vitro apresentou maior resistência aos desafios laboratoriais foi a mesma que apresentou tendência para maior fertilidade in vivo. Assim, sugere-se que submeter amostras seminais a desafios laboratoriais pode ser uma alternativa interessante para selecionar partidas com maior fertilidade a campo.(AU)

Effect of GnRH or estradiol benzoate on reproductive traits during a Heatsynch protocol in dairy cows

Background: Milk production of cows is closely correlated with its reproductive efficiency. One of the several factors influencing the dairy efficiency is the decline in fertility of the cows/heifers. Use of hormonal protocol are often used to improve the fertility of the recipients. Several programs are available to inseminate dairy cows, with variation in the use of different types of hormones, time of use and range of duration period, as well as the time of AI. The objective of this study was to evaluate the efficiency of follicular wave emergence induction of estradiol benzoate in comparison to GnRH in a Heatsynch protocol and its influence on reproductive parameters. Materials, Methods & Results: In this study were used primiparous and multiparous Holstein cows (n = 325). Animals were divided randomly into two different treatments according with the hormone used to induce follicular wave emergence (D0). The GnRH group (n = 167), was given 25 mg, while in the EB group (n = 158) was used 2 mg. At same day, were inserted, a controlled internal drug-releasing containing 1.9 g of progesterone CIDR®. On day 7, CIDR was removed and cows were given 25 mg luteinizing hormone followed by an injection of 1 mg Inducer Ovulation at day 8. Cows were then observed for signs of estrus for at least two hours (twice daily at 7 am and 6 pm) for three days following CIDR® removal. Cows [...](AU)

Effect of GnRH or estradiol benzoate on reproductive traits during a Heatsynch protocol in dairy cows

Background: Milk production of cows is closely correlated with its reproductive efficiency. One of the several factors influencing the dairy efficiency is the decline in fertility of the cows/heifers. Use of hormonal protocol are often used to improve the fertility of the recipients. Several programs are available to inseminate dairy cows, with variation in the use of different types of hormones, time of use and range of duration period, as well as the time of AI. The objective of this study was to evaluate the efficiency of follicular wave emergence induction of estradiol benzoate in comparison to GnRH in a Heatsynch protocol and its influence on reproductive parameters. Materials, Methods & Results: In this study were used primiparous and multiparous Holstein cows (n = 325). Animals were divided randomly into two different treatments according with the hormone used to induce follicular wave emergence (D0). The GnRH group (n = 167), was given 25 mg, while in the EB group (n = 158) was used 2 mg. At same day, were inserted, a controlled internal drug-releasing containing 1.9 g of progesterone CIDR®. On day 7, CIDR was removed and cows were given 25 mg luteinizing hormone followed by an injection of 1 mg Inducer Ovulation at day 8. Cows were then observed for signs of estrus for at least two hours (twice daily at 7 am and 6 pm) for three days following CIDR® removal. Cows [...]

Gonadorelin at the outset and/or end of an ovulation synchronization progesterone estradiol benzoate-based protocol in Nellore females / Gonadorelina no início e/ou no final do protocolo de sincronização da ovulação a base de progesterona e benzoato de estradiol em fêmeas Nelore

This study aimed to evaluate the effects of gonadorelin (GnRH), used both at the outset of a timed artificial insemination (TAI) protocol to synchronize follicular wave recruitment and at the end to synchronize ovulation, on the conception rate (CR) in Nellore cows. The experiment was conducted on two beef cattle farms in the Vale do Araguaia, MT. The body condition score (BCS) evaluation and ultrasound examination to determine ovarian status [follicle diameter < 10 mm, ≥ 10 mm or presence of corpus luteum (CL)] were performed at the beginning (Day 0) of the TAI protocol. Multiparous cows (n = 494) were subjected to the following protocol: Day 0 insertion of intravaginal progesterone device (P4 DIB®, MSD) previously used for 8 or 16 days and IM administration of 2.0 mg of estradiol benzoate (EB, Gonadiol®, MSD); Day 8 P4 device withdrawal, IM injection of 300 IU of equine chorionic gonadotropin (eCG, Folligon®, MSD), 1.0 mg of estradiol cypionate (ECP®, Zoetis) and 0.265 mg of Sodium cloprostenol (PGF2α, Ciosin®, MSD); Day 10 TAI, performed by a single inseminator. Animals were randomly assigned to one of four groups: control (n = 126), GnRH D0 (n = 123), GnRH D10 (n = 123) and GnRH D0 + D10 (n = 122). Animals treated with GnRH received 50 mcg of gonadorelin (GnRH, Cystorelin®, Merial). Pregnancy was diagnosed by ultrasound 39 ± 10 days after TAI. Data were analyzed using the GLIMMIX procedure of SAS program (P < 0.05). The overall CR was 42.71%. Effect of treatment was not detected (P = 0.2482) on CR, which was 36.89% ± 0.19 (47/126) for the control group, 46.08% ± 0.19 (56/123) for GnRH D0, 48.30% ± 0.18 (61/123) for GnRH D10 and 38.48% ± 0.19 (47/122) for GnRH D0 + D10. An effect of farm was detected; the CR was 47.32% ± 0.13 at Farm A and was 38.24% ± 0.13 at Farm B (P = 0.0249). No effects of the interaction between farm and treatment were observed (P = 0.7662), nor of those among ovarian condition and treatment (P = 0.1225) on CR.[...](AU)

Objetivou-se avaliar os efeitos da gonadorelina (GnRH) utilizada para sincronização da emergência da onda de crescimento folicular e para indução da ovulação sincronizada ou em ambos sobre a taxa de concepção (TC) de vacas da raça Nelore. O experimento foi realizado em duas fazendas no Vale do Araguaia, MT. A avaliação do escore de condição corporal (ECC) e a ultrassonografia para determinação da condição dos ovários [folículo com diâmetro < 10 mm, ≥ 10 mm ou presença de corpo lúteo (CL)] foram realizadas no início (Dia 0) do protocolo de inseminação artificial em tempo fixo (IATF). Vacas multíparas (n = 494) foram submetidas ao protocolo: Dia 0 inserção do dispositivo intravaginal de progesterona (P4, DIB®, MSD) utilizado previamente por oito ou 16 dias e aplicação IM de 2,0 mg de Benzoato de Estradiol (BE, Gonadiol®, MSD); Dia 8 remoção do dispositivo, aplicação IM de 300 UI de Gonadotrofina Coriônica Equina (eCG, Folligon®, MSD), de 1,0 mg de Cipionato de Estradiol (ECP®, Zoetis) e de 0,265 mg de Cloprostenol Sódico (PGF2α, Ciosin®, MSD); Dia 10 IATF, realizada por um único inseminador. Os animais foram distribuídos aleatoriamente em quatro grupos: controle (n = 126), GnRH D0 (n = 123), GnRH D10 (n = 123) e GnRH D0 + D10 (n = 122), sendo que os animais tratados com GnRH receberam 50 mcg de gonadorelina (GnRH, Cystorelin®, Merial). O diagnóstico de gestação foi realizado por ultrassonografia 39 ± 10 dias após a IATF. As variáveis foram analisadas pelo procedimento GLIMMIX do programa SAS (P < 0,05). Verificou-se uma TC geral de 42,71%. Não foi detectado efeito dos tratamentos sobre a TC (P = 0,2482), que foi de 36,89% ± 0,19 (47/126) para o grupo controle, 46,08% ± 0,19 (56/123) para GnRH D0, 48,30% ± 0,18 (61/123) para GnRH D10 e de 38,48% ± 0,19 (47/122) para GnRH D0 + D10. Observou-se efeito da variável fazenda, sendo que na Fazenda A a TC foi de 47,32% ± 0,13 e na Fazenda B de 38,24% ± 0,13 (P = 0,0249).[...](AU)

Controle farmacológico do ciclo estral / Pharmacologicol control of oestrus cicle

O emprego de hormônios na fêmea suína objetiva a sincronização do estro à puberdade em marrãs e a sincronização do estro para o emprego da técnica da inseminação artificial em tempo fixo. Na sincronização do estro à puberdade, atenção especial deve estar voltada ao manejo da marrã, pois, além de representar de 30 a 40% do plantel de matrizes, vários fatores envolvidos no manejo afetam a vida útil reprodutiva, influenciando,assim, o rebanho como um todo. O presente trabalho vem abordar alguns aspectos relacionados aos hormônios no ciclo estral, com atenção voltada à importância da sincronização do estro, visando, no complexo interativo do manejo reprodutivo, a uma vida útil reprodutiva ideal, fruto do melhor aproveitamento da matriz no plantel e consequente homogeneização da produção.p(AU)

The use of hormones in the swine female, aims the estrus synchronization at puberty in gilts and the estrus synchronization to the technique of artificial insemination at fixed time. Special attention must be given to the puberty estrus synchronization on the gilts management, because, besides representing 30 to 40% of the breeding herd, there are many factors involved that may affect their reproductive lifetime. The presenting article describes some aspects in relation to the hormones in estrous cycle, mainly estrus synchronization that influenced reproductive lifetime, to the better usage of the female management in the breeding herd and finally in direction to the production homogeneity(AU)

Controle farmacológico do ciclo estral / Pharmacologicol control of oestrus cicle

O emprego de hormônios na fêmea suína objetiva a sincronização do estro à puberdade em marrãs e a sincronização do estro para o emprego da técnica da inseminação artificial em tempo fixo. Na sincronização do estro à puberdade, atenção especial deve estar voltada ao manejo da marrã, pois, além de representar de 30 a 40% do plantel de matrizes, vários fatores envolvidos no manejo afetam a vida útil reprodutiva, influenciando,assim, o rebanho como um todo. O presente trabalho vem abordar alguns aspectos relacionados aos hormônios no ciclo estral, com atenção voltada à importância da sincronização do estro, visando, no complexo interativo do manejo reprodutivo, a uma vida útil reprodutiva ideal, fruto do melhor aproveitamento da matriz no plantel e consequente homogeneização da produção.p

The use of hormones in the swine female, aims the estrus synchronization at puberty in gilts and the estrus synchronization to the technique of artificial insemination at fixed time. Special attention must be given to the puberty estrus synchronization on the gilts management, because, besides representing 30 to 40% of the breeding herd, there are many factors involved that may affect their reproductive lifetime. The presenting article describes some aspects in relation to the hormones in estrous cycle, mainly estrus synchronization that influenced reproductive lifetime, to the better usage of the female management in the breeding herd and finally in direction to the production homogeneity

Positive and negative effects of proges terone during timed AI protocols in lactating dairy cattle

Circulating concentration of progesterone (P4) is determined by a balance between P4 production, primarily by corpus luteum (CL), and P4 metabolism, primarily by liver. The volume of large luteal cells in the CL is a primary factor regulating P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. During timed AI protocols, elevations in P4 are achieved by increasing number of CL by ovulation of accessory CL or by supplementation with exogenous P4. Dietary manipulations, such as fat supplementation, can also be used to alter circulating P4. Elevating P4 prior to the timed AI generally decreases double ovulation an d can increase fertility to the timed AI. This appears to be an effect of P4 during the follicular wave that produces the future ovulatory follicle, possibly by altering the oocyte and subsequent embryo. Near the time of AI, slight elevations in circulating P4 can dramatically reduce fertility. The etiology of slight elevations in P4 near AI is inadequate luteolysis to the prostaglandin F2 α (PGF) treatment prior to timed AI. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Combining results of these studies indicated only marginal fertility benefits of <5%. In conclusion, previous research has provided substantial insight into the effects of supplemental P4 on fertility and there is increasing insight into the mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future re search on P4 manipulation to improve timed AI protocols.

Positive and negative effects of proges terone during timed AI protocols in lactating dairy cattle

Circulating concentration of progesterone (P4) is determined by a balance between P4 production, primarily by corpus luteum (CL), and P4 metabolism, primarily by liver. The volume of large luteal cells in the CL is a primary factor regulating P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. During timed AI protocols, elevations in P4 are achieved by increasing number of CL by ovulation of accessory CL or by supplementation with exogenous P4. Dietary manipulations, such as fat supplementation, can also be used to alter circulating P4. Elevating P4 prior to the timed AI generally decreases double ovulation an d can increase fertility to the timed AI. This appears to be an effect of P4 during the follicular wave that produces the future ovulatory follicle, possibly by altering the oocyte and subsequent embryo. Near the time of AI, slight elevations in circulating P4 can dramatically reduce fertility. The etiology of slight elevations in P4 near AI is inadequate luteolysis to the prostaglandin F2 α (PGF) treatment prior to timed AI. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Combining results of these studies indicated only marginal fertility benefits of <5%. In conclusion, previous research has provided substantial insight into the effects of supplemental P4 on fertility and there is increasing insight into the mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future re search on P4 manipulation to improve timed AI protocols.(AU)

Gonadorelin at the outset and/or end of an ovulation synchronization progesterone estradiol benzoate-based protocol in Nellore females / Gonadorelina no início e/ou no final do protocolo de sincronização da ovulação a base de progesterona e benzoato de estradiol em fêmeas Nelore

This study aimed to evaluate the effects of gonadorelin (GnRH), used both at the outset of a timed artificial insemination (TAI) protocol to synchronize follicular wave recruitment and at the end to synchronize ovulation, on the conception rate (CR) in Nellore cows. The experiment was conducted on two beef cattle farms in the Vale do Araguaia, MT. The body condition score (BCS) evaluation and ultrasound examination to determine ovarian status [follicle diameter < 10 mm, ≥ 10 mm or presence of corpus luteum (CL)] were performed at the beginning (Day 0) of the TAI protocol. Multiparous cows (n = 494) were subjected to the following protocol: Day 0 insertion of intravaginal progesterone device (P4 DIB®, MSD) previously used for 8 or 16 days and IM administration of 2.0 mg of estradiol benzoate (EB, Gonadiol®, MSD); Day 8 P4 device withdrawal, IM injection of 300 IU of equine chorionic gonadotropin (eCG, Folligon®, MSD), 1.0 mg of estradiol cypionate (ECP®, Zoetis) and 0.265 mg of Sodium cloprostenol (PGF2α, Ciosin®, MSD); Day 10 TAI, performed by a single inseminator. Animals were randomly assigned to one of four groups: control (n = 126), GnRH D0 (n = 123), GnRH D10 (n = 123) and GnRH D0 + D10 (n = 122). Animals treated with GnRH received 50 mcg of gonadorelin (GnRH, Cystorelin®, Merial). Pregnancy was diagnosed by ultrasound 39 ± 10 days after TAI. Data were analyzed using the GLIMMIX procedure of SAS program (P < 0.05). The overall CR was 42.71%. Effect of treatment was not detected (P = 0.2482) on CR, which was 36.89% ± 0.19 (47/126) for the control group, 46.08% ± 0.19 (56/123) for GnRH D0, 48.30% ± 0.18 (61/123) for GnRH D10 and 38.48% ± 0.19 (47/122) for GnRH D0 + D10. An effect of farm was detected; the CR was 47.32% ± 0.13 at Farm A and was 38.24% ± 0.13 at Farm B (P = 0.0249). No effects of the interaction between farm and treatment were observed (P = 0.7662), nor of those among ovarian condition and treatment (P = 0.1225) on CR.[...]

Objetivou-se avaliar os efeitos da gonadorelina (GnRH) utilizada para sincronização da emergência da onda de crescimento folicular e para indução da ovulação sincronizada ou em ambos sobre a taxa de concepção (TC) de vacas da raça Nelore. O experimento foi realizado em duas fazendas no Vale do Araguaia, MT. A avaliação do escore de condição corporal (ECC) e a ultrassonografia para determinação da condição dos ovários [folículo com diâmetro < 10 mm, ≥ 10 mm ou presença de corpo lúteo (CL)] foram realizadas no início (Dia 0) do protocolo de inseminação artificial em tempo fixo (IATF). Vacas multíparas (n = 494) foram submetidas ao protocolo: Dia 0 inserção do dispositivo intravaginal de progesterona (P4, DIB®, MSD) utilizado previamente por oito ou 16 dias e aplicação IM de 2,0 mg de Benzoato de Estradiol (BE, Gonadiol®, MSD); Dia 8 remoção do dispositivo, aplicação IM de 300 UI de Gonadotrofina Coriônica Equina (eCG, Folligon®, MSD), de 1,0 mg de Cipionato de Estradiol (ECP®, Zoetis) e de 0,265 mg de Cloprostenol Sódico (PGF2α, Ciosin®, MSD); Dia 10 IATF, realizada por um único inseminador. Os animais foram distribuídos aleatoriamente em quatro grupos: controle (n = 126), GnRH D0 (n = 123), GnRH D10 (n = 123) e GnRH D0 + D10 (n = 122), sendo que os animais tratados com GnRH receberam 50 mcg de gonadorelina (GnRH, Cystorelin®, Merial). O diagnóstico de gestação foi realizado por ultrassonografia 39 ± 10 dias após a IATF. As variáveis foram analisadas pelo procedimento GLIMMIX do programa SAS (P < 0,05). Verificou-se uma TC geral de 42,71%. Não foi detectado efeito dos tratamentos sobre a TC (P = 0,2482), que foi de 36,89% ± 0,19 (47/126) para o grupo controle, 46,08% ± 0,19 (56/123) para GnRH D0, 48,30% ± 0,18 (61/123) para GnRH D10 e de 38,48% ± 0,19 (47/122) para GnRH D0 + D10. Observou-se efeito da variável fazenda, sendo que na Fazenda A a TC foi de 47,32% ± 0,13 e na Fazenda B de 38,24% ± 0,13 (P = 0,0249).[...]