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.

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)

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.