Genome-wide association study of Nelore and Angus heifers with low and high ovarian follicle counts.

The number of antral follicles is considered an important fertility trait because animals with a high follicle count (HFC) produce more oocytes and embryos per cycle. Identification of these animals by genetic markers such as single nucleotide polymorphisms (SNPs) can accelerate selection of future generations. The aim of this study was to perform a genome wide association study (GWAS) on Nelore and Angus heifers with HFC and low (LFC) antral follicle counts. The groups HFC and LFC for genotyping were formed based on the average of total follicles (≥ 3 mm) counted in each breed consistently ± standard deviation. A total of 72 Nelore heifers (32 HFC and 40 LFC) and 48 Angus heifers (21 HFC and 27 LFC) were selected and the DNA was extracted from blood and hair bulb. Genotyping was done using the Illumina Bovine HD 770K BeadChip. The GWAS analysis showed 181 and 201 SNPs with genotype/phenotype association (P ≤ 0.01) in Nelore and Angus heifers, respectively. Functional enrichment analysis was performed on candidate genes that were associated with SNPs. A total of 97 genes were associated to the 181 SNPs in the Nelore heifers and the functional analysis identified genes (ROBO1 and SLIT3) in the ROBO-SLIT pathway that can be involved in the control of germ cell migration in the ovary as it is involved in lutheal cell migration and fetal ovary development. In the Angus heifers, 57 genes were associated with the 201 SNPs, highlighting Fribilin 1 (FBN1) gene, involved in regulation of growth factors directly involved in follicle activation and development. In summary, GWAS for Nelore and Angus heifers showed SNPs associated with higher follicle count phenotype. Furthermore, these findings offer valuable insights for the further investigation of potential mechanism involved in follicle formation and development, important for breeding programs for both breeds.

Equine chorionic gonadotropin drives the transcriptional profile of immature cumulus-oocyte complexes and in vitro-produced blastocysts of superstimulated Nelore cows.

Studies have shown that the use of equine chorionic gonadotropin (eCG), which binds both follicle stimulating hormone (FSH) and luteinizing hormone (LH) receptors, could modify the female reproductive tract. We, thus, aimed to quantify the messenger RNA (mRNA) abundance of genes related to cumulus-oocyte complexes (COCs) and embryo quality in Nelore cows (Bos taurus indicus) submitted to ovarian superstimulation using only FSH (FSH group; n = 10) or replacement of the last two doses of FSH by eCG (FSH/eCG group; n = 10). All animals were slaughtered and the ovarian antral follicles from both groups (10-14 mm in diameter) were aspirated for cumulus, oocyte and in vitro embryo production gene expression analysis. The relative mRNA abundance of 96 genes related to COCs development and embryo quality was measured by RT-qPCR. We found that oocytes are more affected by eCG use and that 35 genes involved in lipid metabolism, oxidative stress, transcriptional control, and cellular development were upregulated in the FSH/eCG group. In blastocysts, lipid metabolism seems to be the main pathway regulated by eCG use. We suggest that these multiple effects could be due to the ability of eCG to bind LHR and FSHR, which could activate multiple signal transduction pathways in the superstimulated ovary, further impacting the transcriptional profile of COCs and blastocysts.

Can the antral follicular count modulate the gene expression of bovine oviducts in Aberdeen Angus and Nelore heifers?

The number of visible ovarian antral follicles (antral follicle count-AFC) is repeatable in bovine individuals, but highly variable between animals, and with differences between Bos taurus and Bos indicus breeds. Several studies have tried to determine the correlation between AFC and increased fertility in cattle. While the impacts of AFC on embryo production, hormonal levels, and pregnancy rates have been described, the molecular effects of AFC on bovine oviducts have not yet been investigated. Here, the aim was to investigate the impact of breeds, such as Aberdeen Angus and Nelore heifer with high or low AFC, on abundance of transcripts and protein related to oviductal transport, sperm reservoir formation, monospermy control, and gamete interaction in the oviducts. In summary, the ovulation side was the major factor that affected transcript abundance on bovine oviducts. However, a discreet effect among AFC and cattle breeds was also observed. Based on this, we concluded and reinforced here that differential microenvironments between ipsilateral and contralateral oviducts have a major effect on modulating the transcripts related to oviductal transport, sperm reservoir formation, monospermy control, and gamete interaction. However, we cannot exclude that there is minimal effect of AFC or breed on regulation of some genes (such as AGTR1, ACE1, FUCA1, and VEGFA) in bovine oviducts.

Uso de LH ou eCG no último dia do protocolo superovulatório em bovinos / Use of LH or eCG in the last day of superovulatolatory protocol in cattle

In the last decades several hormonal treatments to induce multiple ovulation and embryo transfer (MOET) have been developed. Tight control of the time of ovulation allowed the use of fixed-time artificial insemination (FTAI) in bovine embryos donors, facilitating animal management. Although, protocols that allow FTAI have evolved and yield as much embryo as conventional protocols that requires estrus detection, substantial increase in viable embryo production has not been observed in superestimulated bovine cattle. The present review put emphasis on superestimulatory protocols in wich the last two doses of pFSH are replaced by eCG or LH. Recent results indicate that an extra LH stimulus (using eCG or LH), on the last day of P-36 superestimulatory treatment, seems to improve transferable embryo yield in both Bos taurus and Bos indicus cattle.

Na última década, inúmeros tratamentos para induzir ovulação múltipla e transferência de embriões foram desenvolvidos. A sincronização precisa da ovulação permitiu a utilização da inseminação artificial em tempo fixo (IATF) em doadoras de embriões, facilitando o manejo destes animais. Embora os protocolos que permitem a IATF tenham evoluído e produzam tantos embriões viáveis quanto os protocolos convencionais que necessitam da observação do estro, não se observou aumento significativo na produção de embriões oriundos de fêmeas bovinas superestimuladas. Nesta mini-revisão será dada ênfase aos protocolos superestimulatórios nos quais as últimas duas doses de pFSH são substituídas por eCG or LH.Estudos recentes indicam que um estímulo extra de LH (por meio da aplicação de eCG ou LH), no último dia do tratamento superestimulatório, parece aumentar o número de embriões viáveis de raças zebuínas e taurinas.

Uso de LH ou eCG no último dia do protocolo superovulatório em bovinos / Use of LH or eCG in the last day of superovulatolatory protocol in cattle

In the last decades several hormonal treatments to induce multiple ovulation and embryo transfer (MOET) have been developed. Tight control of the time of ovulation allowed the use of fixed-time artificial insemination (FTAI) in bovine embryos donors, facilitating animal management. Although, protocols that allow FTAI have evolved and yield as much embryo as conventional protocols that requires estrus detection, substantial increase in viable embryo production has not been observed in superestimulated bovine cattle. The present review put emphasis on superestimulatory protocols in wich the last two doses of pFSH are replaced by eCG or LH. Recent results indicate that an extra LH stimulus (using eCG or LH), on the last day of P-36 superestimulatory treatment, seems to improve transferable embryo yield in both Bos taurus and Bos indicus cattle.(AU)

Na última década, inúmeros tratamentos para induzir ovulação múltipla e transferência de embriões foram desenvolvidos. A sincronização precisa da ovulação permitiu a utilização da inseminação artificial em tempo fixo (IATF) em doadoras de embriões, facilitando o manejo destes animais. Embora os protocolos que permitem a IATF tenham evoluído e produzam tantos embriões viáveis quanto os protocolos convencionais que necessitam da observação do estro, não se observou aumento significativo na produção de embriões oriundos de fêmeas bovinas superestimuladas. Nesta mini-revisão será dada ênfase aos protocolos superestimulatórios nos quais as últimas duas doses de pFSH são substituídas por eCG or LH.Estudos recentes indicam que um estímulo extra de LH (por meio da aplicação de eCG ou LH), no último dia do tratamento superestimulatório, parece aumentar o número de embriões viáveis de raças zebuínas e taurinas.(AU)

Influência da raça do touro (Bos indicus x Bos taurus) na tolerância ao estresse térmico calórico de embriões bovinos produzidos in vitro / Influence of sire breed (Bos indicus vs Bos taurus) on heat stress tolerance of in vitro-produced bovine embryos

Para melhor compreender as diferenças entre zebuínos e taurinos em relação à resistência ao ETC, objetivou-se verificar se a resistência ao ETC é resultado da contribuição genética do oócito, do espermatozoide ou de ambos. Oócitos de vacas das raças Nelore e mestiças com fenótipo predominante da raça Holandesa preto e branco (mHPB) foram coletados, maturados e fertilizados com espermatozoide de touros das raças Nelore (N), Angus (An), Brahman (Bra) e Gir (Gir). Noventa e seis horas pós-inseminação (hpi), embriões > 16 células foram separados ao acaso em dois grupos: controle e ETC. Embriões do grupo controle foram cultivados a 39 ºC continuamente e do grupo ETC expostos a 41 ºC por 12 horas, retornando a seguir para 39 ºC. Não foi observado efeito do ETC nas raças estudadas, sem redução nas taxas de blastocisto e blastocisto eclodido. As taxas de clivagem e mórula dos embriões mHPB x Gir foram inferiores (p < 0,05) às das demais raças. As raças mHPB x N apresentaram taxas de blastocisto superiores as raças mHPB x An e mHPB x Gir (p < 0,05). Concluiu-se que a contribuição genética do oócito é mais importante do que a do espermatozoide, uma vez que a raça do touro não influenciou a resistência embrionária ao ETC.

To better understand the differences related to HS resistance between Bos indicus and Bos taurus, we aim to verify if the HS tolerance is due mostly to the genetic contribution from the oocyte, spermatozoa or both. Oocytes from Nelore and crossbreed Holstein cows (cHST) were collected, matured and fertilized with semen from Nelore (N), Angus (An), Brahman (Bra) and Gir (Gir) bulls. Nine six hours post insemination (hpi), > 16 cells embryos were separated in two groups: control and HS. In control group, embryos were cultured at 39 ºC, whereas in the HS group, embryos were subjected to 41 ºC for 12 h, and then returned to 39 ºC. There was no effect of HS on blastocyst and hatched blastocyst rates in all breeds analyzed. The percentage of oocytes that cleaved and reached morula stage was significantly lower (p < 0.05) in cHST x Gir as compared to the other breeds. Additionally, blastocyst rates was higher in cHST x N than in cHST x An and cHST x Gir (p < 0.05). It was concluded that the oocyte is more important than the spermatozoa for the development of thermotolerance, since the breed of the bull did not influence embryo development after HS.

Influência da raça do touro (Bos indicus x Bos taurus) na tolerância ao estresse térmico calórico de embriões bovinos produzidos in vitro / Influence of sire breed (Bos indicus vs Bos taurus) on heat stress tolerance of in vitro-produced bovine embryos

Para melhor compreender as diferenças entre zebuínos e taurinos em relação à resistência ao ETC, objetivou-se verificar se a resistência ao ETC é resultado da contribuição genética do oócito, do espermatozoide ou de ambos. Oócitos de vacas das raças Nelore e mestiças com fenótipo predominante da raça Holandesa preto e branco (mHPB) foram coletados, maturados e fertilizados com espermatozoide de touros das raças Nelore (N), Angus (An), Brahman (Bra) e Gir (Gir). Noventa e seis horas pós-inseminação (hpi), embriões > 16 células foram separados ao acaso em dois grupos: controle e ETC. Embriões do grupo controle foram cultivados a 39 ºC continuamente e do grupo ETC expostos a 41 ºC por 12 horas, retornando a seguir para 39 ºC. Não foi observado efeito do ETC nas raças estudadas, sem redução nas taxas de blastocisto e blastocisto eclodido. As taxas de clivagem e mórula dos embriões mHPB x Gir foram inferiores (p < 0,05) às das demais raças. As raças mHPB x N apresentaram taxas de blastocisto superiores as raças mHPB x An e mHPB x Gir (p < 0,05). Concluiu-se que a contribuição genética do oócito é mais importante do que a do espermatozoide, uma vez que a raça do touro não influenciou a resistência embrionária ao ETC.

To better understand the differences related to HS resistance between Bos indicus and Bos taurus, we aim to verify if the HS tolerance is due mostly to the genetic contribution from the oocyte, spermatozoa or both. Oocytes from Nelore and crossbreed Holstein cows (cHST) were collected, matured and fertilized with semen from Nelore (N), Angus (An), Brahman (Bra) and Gir (Gir) bulls. Nine six hours post insemination (hpi), > 16 cells embryos were separated in two groups: control and HS. In control group, embryos were cultured at 39 ºC, whereas in the HS group, embryos were subjected to 41 ºC for 12 h, and then returned to 39 ºC. There was no effect of HS on blastocyst and hatched blastocyst rates in all breeds analyzed. The percentage of oocytes that cleaved and reached morula stage was significantly lower (p < 0.05) in cHST x Gir as compared to the other breeds. Additionally, blastocyst rates was higher in cHST x N than in cHST x An and cHST x Gir (p < 0.05). It was concluded that the oocyte is more important than the spermatozoa for the development of thermotolerance, since the breed of the bull did not influence embryo development after HS.

Influência da raça do touro (Bos indicus x Bos taurus) na tolerância ao estresse térmico calórico de embriões bovinos produzidos in vitro / Influence of sire breed (Bos indicus vs Bos taurus) on heat stress tolerance of in vitro-produced bovine embryos

Para melhor compreender as diferenças entre zebuínos e taurinos em relação à resistência ao ETC, objetivou-se verificar se a resistência ao ETC é resultado da contribuição genética do oócito, do espermatozoide ou de ambos. Oócitos de vacas das raças Nelore e mestiças com fenótipo predominante da raça Holandesa preto e branco (mHPB) foram coletados, maturados e fertilizados com espermatozoide de touros das raças Nelore (N), Angus (An), Brahman (Bra) e Gir (Gir). Noventa e seis horas pós-inseminação (hpi), embriões > 16 células foram separados ao acaso em dois grupos: controle e ETC. Embriões do grupo controle foram cultivados a 39 ºC continuamente e do grupo ETC expostos a 41 ºC por 12 horas, retornando a seguir para 39 ºC. Não foi observado efeito do ETC nas raças estudadas, sem redução nas taxas de blastocisto e blastocisto eclodido. As taxas de clivagem e mórula dos embriões mHPB x Gir foram inferiores (p < 0,05) às das demais raças. As raças mHPB x N apresentaram taxas de blastocisto superiores as raças mHPB x An e mHPB x Gir (p < 0,05). Concluiu-se que a contribuição genética do oócito é mais importante do que a do espermatozoide, uma vez que a raça do touro não influenciou a resistência embrionária ao ETC.(AU)

To better understand the differences related to HS resistance between Bos indicus and Bos taurus, we aim to verify if the HS tolerance is due mostly to the genetic contribution from the oocyte, spermatozoa or both. Oocytes from Nelore and crossbreed Holstein cows (cHST) were collected, matured and fertilized with semen from Nelore (N), Angus (An), Brahman (Bra) and Gir (Gir) bulls. Nine six hours post insemination (hpi), > 16 cells embryos were separated in two groups: control and HS. In control group, embryos were cultured at 39 ºC, whereas in the HS group, embryos were subjected to 41 ºC for 12 h, and then returned to 39 ºC. There was no effect of HS on blastocyst and hatched blastocyst rates in all breeds analyzed. The percentage of oocytes that cleaved and reached morula stage was significantly lower (p < 0.05) in cHST x Gir as compared to the other breeds. Additionally, blastocyst rates was higher in cHST x N than in cHST x An and cHST x Gir (p < 0.05). It was concluded that the oocyte is more important than the spermatozoa for the development of thermotolerance, since the breed of the bull did not influence embryo development after HS.(AU)

LH surge in Nelore cows (Bos indicus), after induced estrus or after ovarian superestimulation.

Considering that there is limited information about the preovulatory LH surge in Zebu cattle (Bos indicus), the purpose of the present work was to assess the LH surge in Nelore cows during the estrous cycle and after ovarian superestimulation of ovarian follicular development with FSH. This information is particularly important to improve superovulatory protocols associated with fixed-time artificial insemination. Nelore cows (n=12) had their estrus synchronized with an intravaginal device containing progesterone (CIDR-B) associated with estradiol benzoate administration (EB, 2.5 mg, i.m., Day 0). Eight days later all animals were treated with PGF2alpha (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38h after the first PGF2alpha injection, blood sampling and ovarian ultrasonography took place every 4h, during 37 consecutive hours. Frequent handling may have resulted in a stress-induced suppression of LH secretion resulting in only 3 of 12 cows having ovulations at 46.7+/-4.9 and 72.3+/-3.8 h, respectively, after removal of CIDR-B. Thirty days later, the same animals received the described hormonal treatment associated with FSH (Folltropin), total dose=200 mg) administered twice a day, during 4 consecutive days, starting on Day 5. Thirty-six hours after the first injection of PGF2alpha, to minimize stress, only seven blood samples were collected at 4h interval each, and ultrasonography was performed every 12 h until ovulation. In 11 of 12 cows (92%) the LH surge and ovulation were observed 34.6+/-1.6 and 59.5+/-1.9 h, respectively, after removal of progesterone source. The maximum values for LH in those animals were 19.0+/-2.6 ng/ml (mean+/-S.E.M.). It is concluded that, in Nelore cows submitted to a ovarian superstimulation protocol, the LH surge occurs approximately 35 h after removal of intravaginal device containing progesterone, and approximately 12h before the LH surge observed after an induced estrus without ovarian superstimulation.

Avaliação da liberação de LH e da concentração de progesterona em protocolos Ovsynch e Heatsynch em bubalinos (Bubalus bubalis) / Evaluation of lh surge and progesterone concentration in ovsynch and heatsynch protocols in buffalo (Bubalus bubalis)

O objetivo desse estudo foi avaliar a liberação de LH durante os protocolos de sincronização da ovulação em bubalinos. Para tanto, quinze búfalas multíparas receberam 25 mg de Lecirelina no Dia 0, e150 mg de D-Cloprostenol no Dia 7. No Dia 8, foi aplicado benzoato de estradiol nas búfalas do Grupo 1 (0,5 mg, n = 5) e do Grupo 2 (1,0mg, n = 5). No Dia 9, os animais receberam 25mg de Lecirelina (Controle, n = 5). Para mensuração das concentrações plasmáticas de LH foram colhidas amostras de sangue da veia jugular no Dia 7, e em seguida em intervalos de 3 horas até completar 72 horas após a aplicação de PGF2a. Para avaliação da liberação de LH foram comparados os momentos de ocorrência do pico LH em relação à PGF2a, as durações, as amplitudes e a área sob o pico de pré-ovulatório de LH. As búfalas dos Grupos Controle, 1 e 2 apresentaram picos pré-ovulatórios de LH em 51 + 0,0 horas, 47,3 + 2,7 horas e 47,0 + 3,8 horas após a aplicação da PGF2a, respectivamente (P>0,05). A duração do pico de LH foi menor no Controle (7,8 + 1,5 horas) do que nos Grupos 1 e 2 (10,5 + 1,5 horas vs. 10,8 + 2,4 horas, respectivamente; P < 0,05). A amplitude média dos picos pré-ovulatórios de LH foram de 4,5 + 0,4ng/mL, 4,0 + 0,4 ng/mL e 4,3 + 0,8 ng/mL para os Grupos Controle, 1 e 2, respectivamente (P > 0,05). A área sob o pico de LH no Controle (4,8 ± 0,7) foi menor do que as áreas dos Grupos 1 e 2 (8,8 ± 2,5 vs.8,7 ± 2,2, respectivamente; P < 0,05). Em resumo, a aplicação de benzoato de estradiol proporcionou maior duração e área do pico pré-ovulatório de LH do que a administração de GnRH em protocolos Ovsynch em bubalinos.(AU)

The objective of this study was to evaluate the LH surge after last hormonal injection of synchronization of ovulation protocols in buffalo. Fifteen multiparous buffaloes received 25 mg of Lecirelin in Day 0, and 150 mg of D-Cloprostenol on Day 7. On Day 8, estradiol benzoate was injected in Group 1 (0.5 mg, n = 5) and Group 2 (1.0mg, n = 5). On Day 9, five buffaloes received 25 mg of Lecirelin (Control). Blood samples were collected for measure the LH concentrations on Day 7 and then every 3 hours until 72 hours after the PGF2a injection. For evaluation of LH surge were compared the interval between PGF2a injection to LH surge, duration, amplitude and area under the LH peak. The LH surge occurred 51.0 + 0.0 hours, 47.3 + 2.7 hours and 47.0 + 3.8 hours after PGF2a injection for Control, Group 1 and Group 2, respectively (P > 0.05). The duration of LH peak in Control (7.8 + 1.5 hours) was shorter than Groups 1 and 2 (10.5 + 1.5 hours vs. 10.8 + 2.4 hours, respectively; P < 0.05). The amplitudes of LH peak were 4.5 + 0.4 ng/mL, 4.0 + 0.4 ng/mL and 4.3 + 0.8 ng/mL for Control, Group 1 and Group 2, respectively (P> 0.05). The area under LH peak for Control (4.8 ± 0.7) was smaller than the areas of the Groups 1 and 2 (8.8 ± 2.5 vs. 8.7 2.2, respectively; P < 0.05). In summary, the estradiol benzoate injection provided higher duration and area of LH peak than GnRH injection in Ovsynch protocol in buffalo.(AU)

Avaliação da liberação de lh e da concentração de progesterona em protocolos ovsynch e heatsynch em bubalinos (Bubalus bubalis) / Evaluation of lh surge and progesterone concentration in ovsynch and heatsynch protocols in buffalo (Bubalus bubalis)

O objetivo desse estudo foi avaliar a liberação de LH durante osprotocolos de sincronização da ovulação em bubalinos. Para tanto, quinze búfalas multíparas receberam 25 mg de Lecirelina no Dia 0, e150 mg de D-Cloprostenol no Dia 7. No Dia 8, foi aplicado benzoato de estradiol nas búfalas do Grupo 1 (0,5 mg, n = 5) e do Grupo 2 (1,0mg, n = 5). No Dia 9, os animais receberam 25mg de Lecirelina(Controle, n = 5). Para mensuração das concentrações plasmáticas de LH foram colhidas amostras de sangue da veia jugular no Dia 7, e em seguida em intervalos de 3 horas até completar 72 horas após a aplicação de PGF2a. Para avaliação da liberação de LH foram comparados os momentos de ocorrência do pico LH em relação à PGF2a, as durações, as amplitudes e a área sob o pico de pré-ovulatório de LH. As búfalasdos Grupos Controle, 1 e 2 apresentaram picos pré-ovulatórios deLH em 51 + 0,0 horas, 47,3 + 2,7 horas e 47,0 + 3,8 horas após a aplicação da PGF2a, respectivamente (P>0,05). A duração do pico deLH foi menor no Controle (7,8 + 1,5 horas) do que nos Grupos 1 e2 (10,5 + 1,5 horas vs. 10,8 + 2,4 horas, respectivamente; P < 0,05). Aamplitude média dos picos pré-ovulatórios de LH foram de 4,5 + 0,4ng/mL, 4,0 + 0,4 ng/mL e 4,3 + 0,8 ng/mL para os Grupos Controle,1 e 2, respectivamente (P > 0,05). A área sob o pico de LH no Controle(4,8 ± 0,7) foi menor do que as áreas dos Grupos 1 e 2 (8,8 ± 2,5 vs.8,7 ± 2,2, respectivamente; P < 0,05). Em resumo, a aplicação debenzoato de estradiol proporcionou maior duração e área do picopré-ovulatório de LH do que a administração de GnRH em protocolos Ovsynch em bubalinos.

The objective of this study was to evaluate the LH surge after lasthormonal injection of synchronization of ovulation protocols inbuffalo. Fifteen multiparous buffaloes received 25 mg of Lecirelin inDay 0, and 150 mg of D-Cloprostenol on Day 7. On Day 8, estradiolbenzoate was injected in Group 1 (0.5 mg, n = 5) and Group 2 (1.0mg, n = 5). On Day 9, five buffaloes received 25 mg of Lecirelin(Control). Blood samples were collected for measure the LHconcentrations on Day 7 and then every 3 hours until 72 hours afterthe PGF2a injection. For evaluation of LH surge were compared theinterval between PGF2a injection to LH surge, duration, amplitudeand area under the LH peak. The LH surge occurred 51.0 + 0.0 hours,47.3 + 2.7 hours and 47.0 + 3.8 hours after PGF2a injection for Control,Group 1 and Group 2, respectively (P > 0.05). The duration of LHpeak in Control (7.8 + 1.5 hours) was shorter than Groups 1 and 2(10.5 + 1.5 hours vs. 10.8 + 2.4 hours, respectively; P < 0.05). Theamplitudes of LH peak were 4.5 + 0.4 ng/mL, 4.0 + 0.4 ng/mL and4.3 + 0.8 ng/mL for Control, Group 1 and Group 2, respectively (P> 0.05). The area under LH peak for Control (4.8 ± 0.7) was smallerthan the areas of the Groups 1 and 2 (8.8 ± 2.5 vs. 8.7 2.2, respectively;P < 0.05). In summary, the estradiol benzoate injection providedhigher duration and area of LH peak than GnRH injection in Ovsynchprotocol in buffalo.

Do high progesterone concentrations decrease pregnancy rates in embryo recipients synchronized with PGF2alpha and eCG?

The objective of this study was to evaluate the effects of equine chorionic gonadotropin (eCG) treatment on the number of induced accessory corpora lutea (CL), plasma progesterone concentrations and pregnancy rate in cross-bred heifers after transfer of frozen-thawed (1.5M ethylene glycol) embryos. All recipients received 500 microg PGF2alpha (dl-cloprostenol, i.m.) at random stages of the estrous cycle (Day 0) and were observed for estrus for 7 days. On Day 14, heifers detected in estrus between 2 and 7 days after PGF2alpha treatment were randomly allocated to four groups ( n=83 per group) and given 0 (control), 200, 400, or 600 IU of eCG. Two days later (Day 16), these recipients were given PGF2alpha and observed for estrus. Six to eight days after detection of estrus, plasma samples were collected to determine progesterone concentration and ultrasonography was performed to observe ovarian structures. Heifers with multiple CL or a single CL >15 mm in diameter received an embryo by direct transfer. Embryos of excellent and good quality were thawed and transferred to the recipients by the same veterinarian. Pregnancy was diagnosed by ultrasonography and confirmed by transrectal palpation 21 and 83 days after embryo transfer (ET), respectively. Plasma progesterone concentrations on the day of transfer (Day 7 of the estrous cycle) were 3.9+/-0.7, 4.2+/-0.4,6.0+/-0.4 and 7.8+/-0.6 ng/ml for groups Control, 200, 400, and 600, respectively (Control versus treated groups P=0.009; 200 versus 400 and 600 groups P=0.0001; and 400 versus 600 P=0.012 ). Conception rates 83 days after ET were 41.9, 50.0, 25.0, and 20.9% for groups Control, 200, 400, and 600, respectively (200 versus 400 and 600 groups P=0.0036 ). In conclusion, an increase in progesterone concentration, induced by eCG treatment, did not improve pregnancy rates in ET recipients. Conversely, there was a decline in conception rates in the animals with the highest plasma progesterone concentrations.

Embryo recovery and pregnancy rates after the delay of ovulation and fixed time insemination in superstimulated beef cows.

The aim of this study was to evaluate the effect of delaying ovulation subsequent to superstimulation of follicular growth in beef cows (Bos indicus) on embryo recovery rates and the capacity of embryos to establish pregnancies. Ovulation was delayed by three treatments using either progesterone (CIDR-B) or a GnRH agonist (deslorelin). Multiparous Nelore cows (n = 24) received three of four superstimulation treatments in an incomplete block design (n = 18 per group). Cows in Groups CTRL, P48 and P60 were treated with a CIDR-B device plus estradiol benzoate (EB, 4 mg, i.m.) on Day-5, while cows in Group D60 were implanted with deslorelin on Day-7. Cows were superstimulated with FSH (Folltropin-V, 200 mg), from Day 0 to 3, using twice daily injections in decreasing amounts. All cows were treated with a luteolytic dose of prostaglandin on Day 2 (08:00 h). CIDR-B devices were removed as follows: Group CTRL, Day 2 (20:00 h); Group P48, Day 4 (08:00 h); Group P60, Day 4 (20:00 h). Cows in Group CTRL were inseminated at 10, 20 and 30 h after first detected estrus. Ovulation was induced for cows in Group P48 (Day 4, 08:00 h) and Groups P60 and D60 (Day 4, 20:00 h) by injection of LH (Lutropin, 25 mg, i.m.), and these cows were inseminated 10 and 20 h after treatment with LH. Embryos were recovered on Days 11 or 12, graded and transferred to synchronized recipients. Pregnancies were determined by ultrasonography around Day 100. Data were analyzed by mixed procedure, Kruskal-Wallis and Chi-square tests. The number of ova/embryos, transferable embryos (mean +/- SEM) and pregnancy rates (%) were as follows, respectively: Group CTRL (10.8+/-1.8, 6.1+/-1.3, 51.5), P48 (12.6+/-1.9, 7.1+/-1.0, 52.3), P60 (10.5+/-1.6, 5.7+/-1.3, 40.0) and D60 (10.3+/-1.7, 5.0+/-1.2, 50.0). There were no significant differences among the groups (P > 0.05). It was concluded that fixed time AI in association with induced ovulation did not influence embryo recovery. Furthermore, pregnancy rates in embryos recovered from cows with delayed ovulation were similar to those in embryos obtained from cows treated with a conventional superstimulation protocol.