Perfil de FSH e LH na divergência folicular em novilhas Nelore (Bos indicus)

Present study aimed to evaluate gonadotropins profiles in 12 Nelore heifers, in order to test the hypothesis that FSH concentrations decrease and LH presents a transient increase during follicle selection. Blood samples from jugular vein were harvested twice daily starting at the time of ovulation (D0) until D5. Plasma samples were assayed for FSH and LH by double antibody radioimmunoassay method. LH and FSH assay sensitivity was 0,02ng/ml and 0,005ng/ml, respectively. The intraassay coefficient of variation was 13,6% and 18,8%, respectively. Data (mean±SEM) were normalized to follicle deviation and analyzed by ANOVA and by linear, cubic, and quadratic regressions. Comparisons between higher and lower FSH values were also performed by T-test. There was no effect of time in plasmatic FSH and LH circulating levels when variance analysis or regression analysis were performed. However, by T-test, FSH concentrations reached the lowest plasmatic levels 36 (0,40±0,05ng/ml) and 60 hours (0,42±0,04ng/ml) after follicular deviation, comparatively to 36 hours before deviation, when the concentrations were maximal (0,63±0,08ng/ml). In conclusion, there is a FSH decrease, although a transient LH elevation has not been confirmed encompassing follicle deviation in Nelore females.O presente estudo teve como objetivo traçar o perfil de gonadotrofinas em 12 novilhas Nelore, a fim de testar a hipótese de que há declínio nas concentrações de FSH e elevação transitória nos níveis de LH durante a seleção folicular. A partir da ovulação (D0) foram colhidas amostras de sangue da veia jugular a cada 12 horas até o D5, para a dosagem de FSH e LH plasmáticos. Empregou-se o método de radioimunoensaio de duplo anticorpo. A sensibilidade do ensaio de LH foi de 0,02ng/ml e a de FSH de 0,005ng/ml. Os coeficientes de variação intra-ensaio foram 13,6% e 18,8%, respectivamente. Os dados (média±EPM) foram normalizados para o momento da divergência folicular e, posteriormente, analisados por ANOVA e por regressão linear, cúbica e quadrática. Também foi empregado o Teste t para comparação entre o ponto mais alto e o mais baixo da curva. Não se verificou efeito de tempo sobre as concentrações plasmáticas de FSH e de LH quando se utilizou análise de variância e de regressão. Entretanto, através do Teste t pontual, o FSH atingiu as menores concentrações plasmáticas 36 (0,40±0,05ng/ml) e 60 horas (0,42±0,04ng/ml) após a divergência, comparativamente às 36 horas anteriores ao desvio, quando as concentrações foram máximas (0,63±0,08ng/ml). Conclui-se, portanto, que há declínio nas concentrações plasmáticas de FSH, contudo, não foi comprovada elevação transitória nas concentrações de LH próximo ao momento do desvio folicular em fêmeas Nelore

In vitro oocyte transport through the oviduct of buffalo and crossbred beef cows

The present study was conducted to verify if the elevation of plasma concentrations of estradiol during superovulatory treatments affects the oocyte transport in buffalo females, as well as if the inferior quality of buffalo oocytes and/or some functional difference on the oviduct of these animals is responsible for the low embryo recovery rate in superovulated uffaloes when compared to cows subjected to the same treatment. Oviducts of 10 buffaloes and 15 of cows, treated to induce a single ovulation were used. The oviducts were placed on Petri dishes and received the following treatments: 5 buffalo oocytes with no E2 (G-BufBuf and G-BovBuf), 5 bovine oocytes with no E2 (G-BufBov and G-BovBov), 5 buffalo oocytes with E2 (G-BufE2Buf and G-BovE2Buf) and 5 bovine oocytes with E2 (G-BufE2Bov and G-BovE2Bov; factorial 2x2x2). Oocytes were incubated for 24h. Subsequently, oviducts were washed and oocytes were recovered and counted. Since no interactions were found between E2 treatment, oviducts and oocytes species, main effects were analyzed separately. Recovery rate and number of oocytes was higher on cattle compared to buffaloes (35.0+8.6% and 1.4+0.3 vs. 10.0±4.6% and 0.5±0.2, respectively; p<0.05); no effect of E2 treatment was observed on recovery rate and number of oocytes (29.8±9.0% and 1.3±0.4 vs. 16.9±6.1% and 0.7±0.2, respectively; p>0.05); the number of buffaloes and bovine oocytes recovered were similar (1.4±0.4 and 0.6±0.2, respectively; p>0.05). Oocytes recovery rate showed a trend (P=0.07) to be higher when buffalo oocytes were implanted when compared to bovine oocytes (35.2±9.2% vs. 12.9±5.4%). Present results suggest that oocyte transport by the oviduct of buffaloes and bovine was not dependent on oocytes species or E2 supplementation to the culture medium.O presente estudo foi realizado para verificar se a elevação das concentrações plasmáticas de estradiol durante os tratamentos  superovulatórios afeta o transporte dos oócitos em fêmeas bubalinas, bem como se a qualidade inferior dos oócitos de búfalos e/ou alguma diferença funcional no oviduto destes animais é responsável pela baixa taxa de recuperação de embriões em búfalas superovuladas quando comparadas a vacas submetidas ao mesmo tratamento. Foram utilizados 10 ovidutos de búfalas e 15 de vacas, tratadas para a indução de ovulação única. Os ovidutos foram colocados em placas de Petri e receberam os seguintes tratamentos: sem E2 e inseridos com 5 oócitos de búfalas (G-BufBuf e G-BovBuf); sem E2 e com 5 oócitos de vacas (G-BufBov e G-BovBov); com E2 e com 5 oócitos de búfalas (G-BufE2Buf e G-BovE2Buf); e com E2 e com 5 oócitos de vacas (G-BufE2Bov e G-BovE2Bov; fatorial 2x2x2). Posteriormente, foram incubados por 24h e, após esse período, foram lavados para a recuperação e contagem dos oócitos. Como não foi verificado efeito de interação, foram analisados os efeitos principais. O número e a taxa de recuperação de oócitos foi maior em ovidutos de vacas que de búfalas (1,4±0,3/35,0±8,6% vs. 0,5±0,2/10,0±4,6%; P<0,05). Foi verificado que o tratamento com ou sem E2 não interferiu no número e na taxa de recuperação de oócitos (1,3±0,4/29,8±9,0% vs. 0,7±0,2/16,9±6,1%; P>0,05). Não foi verificada diferença no número de oócitos de búfalas ou de vacas recuperados (1,4±0,4 e 0,6±0,2; P>0,05). Observou-se também que houve tendência (P=0,07) de maior taxa de recuperação de oócitos de búfalas que de vacas (35,2±9,2% vs. 12,9±5,4%). Os dados são indicativos de que o transporte de oócitos pelo oviduto de búfalas e de vacas independe da espécie do oócito e não é influenciado pelo E2

Manipulation of follicle development to ensure optimal oocyte quality and conception rates in cattle

Over the last several decades, a number of therapies have been developed that manipulate ovarian follicle growth to improve oocyte quality and conception rates in cattle. Various strategies have been proposed to improve the responses to reproductive biotechnologies following timed artificial insemination (TAI), superovulation (SOV) or ovum pickup (OPU) programmes. During TAI protocols, final follicular growth and size of the ovulatory follicle are key factors that may significantly influence oocyte quality, ovulation, the uterine environment and consequently pregnancy outcomes. Progesterone concentrations during SOV protocols influence follicular growth, oocyte quality and embryo quality; therefore, several adjustments to SOV protocols have been proposed depending on the animal category and breed. In addition, the success of in vitro embryo production is directly related to the number and quality of cumulus oocyte complexes harvested by OPU. Control of follicle development has a significant impact on the OPU outcome. This article discusses a number of key points related to the manipulation of ovarian follicular growth to maximize oocyte quality and improve conception rates following TAI and embryo transfer of in vivo-and in vitro-derived embryos in cattle.FAPESPCNPqCAPE

Can in vitro embryo production be estimated from semen variables in Senepol breed by using artificial intelligence?

Thoroughly analyzing the sperm and exploring the information obtained using artificial intelligence (AI) could be the key to improving fertility estimation. Artificial neural networks have already been applied to calculate zootechnical indices in animals and predict fertility in humans. This method of estimating the results of reproductive biotechnologies, such as in vitro embryo production (IVEP) in cattle, could be valuable for livestock production. This study was developed to model IVEP estimates in Senepol animals based on various sperm attributes, through retrospective data from 290 IVEP routines performed using 38 commercial doses of semen from Senepol bulls. All sperm samples that had undergone the same procedure during sperm selection for in vitro fertilization were evaluated using a computer-assisted sperm analysis (CASA) system to define sperm subpopulations. Sperm morphology was also analyzed in a wet preparation, and the integrity of the plasma and acrosomal membranes, mitochondrial potential, oxidative status, and chromatin resistance were evaluated using flow cytometry. A previous study identified three sperm subpopulations in such samples and the information used in tandem with other sperm quality variables to perform an AI analysis. AI analysis generated models that estimated IVEP based on the season, donor, percentage of viable oocytes, and 18 other sperm predictor variables. The accuracy of the results obtained for the three best AI models for predicting the IVEP was 90.7, 75.3, and 79.6%, respectively. Therefore, applying this AI technique would enable the estimation of high or low embryo production for individual bulls based on the sperm analysis information

Reference gene selection for gene expression analysis of oocytes collected from dairy cattle and buffaloes during winter and summer

Oocytes from dairy cattle and buffaloes have severely compromised developmental competence during summer. While analysis of gene expression is a powerful technique for understanding the factors affecting developmental hindrance in oocytes, analysis by real-time reverse transcription PCR (RT-PCR) relies on the correct normalization by reference genes showing stable expression. Furthermore, several studies have found that genes commonly used as reference standards do not behave as expected depending on cell type and experimental design. Hence, it is recommended to evaluate expression stability of candidate reference genes for a specific experimental condition before employing them as internal controls. In acknowledgment of the importance of seasonal effects on oocyte gene expression, the aim of this study was to evaluate the stability of expression levels of ten well-known reference genes (ACTB, GAPDH, GUSB, HIST1H2AG, HPRT1, PPIA, RPL15, SDHA, TBP and YWHAZ) using oocytes collected from different categories of dairy cattle and buffaloes during winter and summer. A normalization factor was provided for cattle (RPL15, PPIA and GUSB) and buffaloes (YWHAZ, GUSB and GAPDH) based on the expression of the three most stable reference genes in each species. Normalization of non-reference target genes by these reference genes was shown to be considerably different from normalization by less stable reference genes, further highlighting the need for careful selection of internal controls. Therefore, due to the high variability of reference genes among experimental groups, we conclude that data normalized by internal controls can be misleading and should be compared to not normalized data or to data normalized by an external control in order to better interpret the biological relevance of gene expression analysis.The research was granted by São Paulo Research Foundation (FAPESP; grant numbers 2009/00938-3, 2010/13384-3, 2010/09561-7, 2011/14207-0 and 2012/07510-1), National Counsel of Technological and Scientific Development (CNPq; grant number 476229/2011-1) and Coordination for the Improvement of Higher Level Personnel (CAPES). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

In vivo recovery rate and in vitro competence of Bubalus bubalis, Bos indicus and Bos taurus oocytes obtained at different phases of follicular wave

O objetivo do presente estudo foi o de determinar em qual fase da onda de crescimento folicular são obtidas maiores taxas de recuperação e competência de oócitos obtidos por aspiração folicular (OPU) em novilhas cruzadas (Bos indicus x Bos taurus; Capítulo 1) ou em novilhas bubalinas (Bubalus bubalis), zebuínas (Nelore; Bos indicus) e taurinas (Holandês; Bos taurus; Capítulo 2). No Capítulo 1, 30 novilhas cruzadas foram submetidas à OPU aos 2 (D2), 4 (D4) e 6 (D6) dias após a emergência da onda de crescimento folicular (n=10/ grupo), em delineamento "cross-over" realizado em 3 réplicas. Os oócitos recuperados foram selecionados e os viáveis submetidos aos procedimentos de produção in vitro. Os dados foram analisados por ANOVA, utilizando o PROC MIXED, considerando os efeitos fixos de momento de OPU, de réplica e da interação entre eles, e o efeito aleatório de doadora. Foram produzidos maior taxa de blastocistos aos 6 dias pós-FIV, bem como maior número de blastocistos aos 9 dias pós-FIV e maior número de núcleos dos embriões eclodidos quando procedeu-se com aspiração no D2. Contudo, a OPU realizada no D6 também influenciou positivamente a taxa de blastocistos 6 dias pós FIV e não diferiu dos outros momentos com relação ao número de núcleos dos embriões eclodidos. No Capítulo 2, foram realizados 2 experimentos (1 e 2). No Experimento 1, foi avaliado o efeito de 50 mg de progesterona injetável na sincronização de emergência folicular em novilhas Nelore, Holandesas e bubalinas submetidas a protocolo de sincronização à base de progestágeno associado a 2 mg de benzoato de estradiol (n=10/ grupo). Os dados foram analisados por regressão logística, utilizando o PROC GLIMMIX. O momento da emergência folicular não foi afetado pela administração de progesterona injetável, ocorrendo entre 4,2 a 4,5 dias após o início do protocolo de sincronização para os três grupos genéticos. No Experimento 2, foram avaliados os efeitos de momento de sincronização da emergência folicular para a aspiração folicular (1, 3 ou 5 dias após a emergência) e de grupo genético (Nelore, Holandês e búfalo) na produção de embriões in vitro. Um total de 27 novilhas (9 de cada grupo genético, subdivididas nos 3 momentos de aspiração folicular) foram submetidas a 6 sessões de OPU, em delineamento "cross-over". Os oócitos recuperados foram selecionados e os viáveis submetidos aos procedimentos de produção in vitro. Os dados foram analisados por ANOVA, utilizando o PROC MIXED, considerando os efeitos fixos de momento de OPU, de grupo genético, de réplica e da interação entre eles, e o efeito aleatório de doadora. Os resultados demonstraram que novilhas Nelore apresentaram melhor eficiência para a produção de embriões in vitro do que as novilhas Holandesas ou bubalinas, e que a aspiração folicular realizada em diferentes momentos da onda folicular sincronizada não influenciou a produção in vitro.The objective of the present study was to determine in which phase of follicular wave higher recovery rates and better oocyte competence can be obtained by ovum pickup (OPU) in crossbred (Bos indicus x Bos taurus; Chapter 1) or buffalo (Bubalus bubalis), Nelore (Bos indicus) and Holstein heifers (Bos taurus; Chapter 2). In Chapter 1, 30 crossbred heifers were submitted to OPU on days 2 (D2), 4 (D4) or 6 (D6) after follicular wave emergence (n=10/ group), in a cross-over design performed in 3 replicates. Oocytes recovered were selected and those viable were submitted to in vitro embryo procedures. Data were analyzed by ANOVA, using PROC MIXED, in which time of OPU, replicate and interaction between these factors were considered as fixed effects, and donor was considered as a random effect. Higher blastocyst rate (6 days after IVF), number of blastocysts (9 days after IVF), and number of nuclei of hatched embryos were produced when OPU was done on D2. However, OPU on D6 also produced a higher blastocyst rate (6 days after IVF), and did not differ from other times of OPU concerning number of nuclei of hatched embryos. In Chapter 2, two experiments were performed. In Experiment 1, the effect of 50 mg of injectable progesterone was evaluated in the synchronization of follicular wave emergence of Nelore, Holstein, and buffalo heifers submitted to a progestin plus 2 mg of estradiol benzoate protocol (n=10/ group). Data were analyzed by logistic regression, by PROC GLIMMIX. The time of follicular wave emergence was not affected by administration of injectable progesterone. Besides, follicular wave emergence occurred between 4.2 and 4.5 days after the beginning of synchronization protocol for all genetic groups. In Experiment 2, the effects of time of OPU relative to follicular wave emergence (1, 3 or 5 days) and of genetic group (Nelore, Holstein, and buffalo) on in vitro embryo production were evaluated. A total of 27 heifers (9 of each genetic group, assigned in the 3 times of OPU) were submitted to 6 OPU sessions, in a cross-over design. Oocytes recovered were selected and those viable were submitted to in vitro embryo procedures. Data were analyzed by ANOVA, using PROC MIXED, in which time of OPU, genetic group, replicate and interaction between these factors were considered as fixed effects, and donor was considered as a random effect. Results demonstrated that Nelore heifers showed a better efficiency for in vitro embryo production than Holstein or buffalo heifers. Additionally, OPU performed at different times of synchronized follicular wave did not influence in vitro embryo production

Study of follicle deviation and ovulatory capacity in buffaloes (Bubalus bubalis) and zebu cattle (Bos indicus)

O presente estudo está apresentado em Capítulo 1 (Divergência folicular; DF) e 2 (Capacidade ovulatória), e em cada estão incluídos dois experimentos [1 - em bubalinos (Bubalus bubalis); 2 - em zebuínos (Bos indicus)]. Os objetivos do Capítulo 1 foram determinar o momento e diâmetro na DF e avaliar o perfil das concentrações plasmáticas de FSH e LH próximo à seleção folicular. No Experimento 1, a ovulação foi considerada o dia zero (D0), a partir do qual 10 novilhas Murrah foram examinadas por ultra-sonografia (US) a cada oito horas (h) até o D4 e, posteriormente, a cada 24h até o D6. A avaliação da DF foi realizada por análise visual do gráfico de cada novilha (Ginther et al., 1996) e regressão linear segmentada (Bergfelt et al. 2003). As amostras de sangue, para dosagem de FSH e LH, foram colhidas com intervalos de 8h nas primeiras 24h pós-ovulação. A partir deste momento foram feitas colheitas a cada 4h até o D4 e após, a cada 12h até o D6. No método visual, o intervalo ovulação-DF, e o diâmetro dos folículos dominante (FD) e subordinado (FS) foram de, respectivamente, 63,2±5,7h; 7,2±0,3mm e 6,4±0,3mm (média±EPM). No método matemático estes mesmos parâmetros foram de, respectivamente, 61,9±4,9h; 7,3±0,3mm e 6,3±0,3mm. Não houve diferença entre os dois métodos de avaliação da DF (P>0,05). As concentrações plasmáticas de FSH e LH não variaram ao longo do tempo (P>0,05). No Experimento 2, 12 novilhas Nelore foram submetidas à US a cada 12h até o D5 e estes mesmos intervalos foram adotados para as colheitas de sangue (dosagem de FSH e LH). No método visual, o intervalo ovulação-DF, e os diâmetros do FD e FS foram de, respectivamente, 61,0±5,8h; 6,2±0,2mm e 5,8±0,2mm. No método matemático estes mesmos parâmetros foram de, respectivamente, 57,2±6,0h; 6,2±0,3mm e 5,9±0,3mm. Não houve diferença entre os métodos (P>0,05). As concentrações plasmáticas de FSH e LH não variaram ao longo do tempo (P>0,05). No Capítulo 2, o objetivo foi avaliar o diâmetro no qual o FD adquire capacidade ovulatória após administração de 25mg de LH. Os grupos foram formados de acordo com o diâmetro do FD no momento do tratamento com LH (7,0-8,4mm; 8,5-10,0mm e >10,0mm, em ambos os experimentos). No Experimento 1, foram utilizadas 29 novilhas bubalinas Murrah x Mediterrâneo. A partir do D3 (pós-ovulação), os exames US foram realizados a cada 12h até 48h do tratamento com LH. Nos grupos 7,0-8,4; 8,5-10,0 e >10,0mm, os diâmetros foliculares no momento da aplicação do LH foram de 7,8c±0,1; 9,3b±0,2 e 11,0a±0,3mm e as taxas de ovulação de 0,0%b (0/10); 50,0%a (5/10) e 55,6%a (5/9), respectivamente. No Experimento 2, 29 novilhas Bos indicus foram monitoradas por US a cada 24h a partir da ovulação até o tratamento com LH, e então a cada 12h durante 48h. Nos grupos 7,0-8,4; 8,5-10,0 e >10,0mm, os diâmetros foliculares no momento da aplicação do LH foram de 7,6c±0,1; 9,6b±0,1 e 10,9a±0,2mm e as taxas de ovulação de 33,3%b (3/9); 80,0%a (8/10) e 90,0%a (9/10), respectivamente.Present study is presented in Chapter 1 (Follicle deviation; FD) and 2 (Ovulatory capacity). Each chapter includes two experiments [1 - in buffaloes (Bubalus bubalis); 2 - in zebu cattle (Bos indicus)]. In Chapter 1, aims were to determine moment and diameter deviation and to evaluate FSH and LH plasmatic profiles encompassing follicle selection. In Experiment 1, ovulation was considered day 0 (D0). From D0, 10 Murrah heifers were examined by ultrasound (US) each eight hours (h) until D4 and then, every 24h until D6. FD evaluation was performed by visual analysis (Ginther et al., 1996) and by segmented linear regression (Bergfelt et al., 2003). Blood samples were harvested each 8h in the first 24h post ovulation. From this moment blood collections were performed every 4h until D4 and after that, each 12h until D6. Interval ovulation-FD, dominant (DF) and subordinate follicle (SF) diameters, by visual method, were, respectively, 63.2±5.7h; 7.2±0.3mm and 6.4±0.3mm (mean±SEM). These same end points, by mathematical method, were, respectively, 61.9±4.9h; 7.3±0.3mm and 6.3±0.3mm. No differences between both methods of FD evaluation (P>0.05) were found. No changes in plasmatic FSH and LH levels along the time (P>0.05) were found. In Experiment 2, 12 Nelore heifers were submmited to US each 12h until D5, and these same intervals were used to blood harvests (FSH and LH profiles). Interval ovulation-FD, dominant (DF) and subordinate follicle (SF) diameters, by visual method, were, respectively, 61.0±5.8h; 6.2±0.2mm and 5.8±0.2mm. These same end points, by mathematical method, were, respectively, 57.2±6.0h; 6.2±0.3mm and 5.9±0.3mm. No differences between both methods of FD evaluation (P>0.05) were found. No changes in plasmatic FSH and LH levels along the time (P>0.05) were found. In Chapter 2, aim was to evaluate diameter in which DF acquires ovulatory capacity after administration of 25mg of LH. The animals were assigned in groups according to DF diameter at LH treatment (7.0-8.4mm; 8.5-10.0mm and >10.0mm, in both experiments). In Experiment 1, 29 Murrah x Mediterrâneo heifers were used. From D3 (post ovulation), US examinations were performed each 12h until 48h after LH treatment. Follicle diameters at LH chalenge in groups 7.0-8.4mm, 8.5-10.0mm and >10.0mm, were 7.8c±0.1, 9.3b±0.2 and 11.0a±0.3mm, and ovulation rates were 0.0%b (0/10), 50.0%SUP>a (5/10) and 55.6%a (5/9), respectively. In Experiment 2, 29 Bos indicus heifers were monitored by US every 24h from ovulation until LH chalenge, and then each 12h during 48h. Follicle diameters at LH treatment in groups 7.0-8.4mm, 8.5-10.0mm and >10.0mm, were 7.6c±0.1, 9.6b±0.1 and 10.9a±0.2mm, and ovulation rates were 33.3%b (3/9), 80.0%a (8/10) and 90.0%a (9/10), respectivel

OVARIAN FOLLICULAR DYNAMIC DURING EARLY PREGNANCY IN BUFFALO Bubalus bubalis HEIFERS DINÂMICA FOLICULAR DURANTE A GESTAÇÃO INICIAL EM NOVILHAS BÚFALAS Bubalus bubalis

The aim of the present study was to characterize the follicular dynamics during early pregnancy in Murrah heifers. Ten heifers were submitted to daily transrectal ultrasonographic examination, from the 18th to 60th day of pregnancy. Three animals presented follicular waves of 9.67?0.58 days in duration and the dominant and largest subordinate follicles measured, respectively, 11.9?1.3 mm and 7.0?1.0 mm. The growth plateau was 6.00?1.00 days in duration. The remaining seven heifers presented an irregular follicular development with three different patterns as follow: the first irregular observed pattern, characterized by waves of 7.91±1.68 days in duration, with the dominant follicle and the largest subordinated follicle reaching maximum diameter of 11.4±1.1 and 7.0±1.6 mm, respectively. The deviation on this pattern happened on day 3.57±0.53 and the plateau had an average duration of 4.67±1.37 days. The second irregular observed pattern presented waves lasting 6.44±1.81 days, with the dominant follicle and the largest subordinated follicle reaching maximum diameter of 9.0±0.6 and 6.8±0.4 mm, respectively. The deviation happened on day 4.00±1.41 after the wave detection. The third irregular pattern observed was characterized by periods of subsequent follicular growth without defined phases as described for the first and second patterns. In conclusion, from the 18th to 60th day of pregnancy, the follicular development is characterized by waves of different patterns in buffalo. Keywords Buffalo, Pregnancy, Ultrasound, Follicular Dynamic. O objetivo do presente estudo foi caracterizar a dinâmica folicular durante a gestação inicial em novilhas Murrah. Dez novilhas foram submetidas ao exame ultra-sonográfico transretal diário do 18º ao 60º dia de gestação. Três animais apresentaram ondas foliculares de 9,67?0,58 dias de duração, folículo dominante e maior subordinado com diâmetro de 11,9?1,3 mm e 7,0?1,0 mm, respectivamente, e platô com 6,00?1,00 dias de duração. As sete novilhas restantes apresentaram três padrões de crescimento folicular irregulares: o primeiro padrão irregular observado foi caracterizado por ondas de 7,91±1,68 dias de duração, folículo dominante e maior subordinado alcançando diâmetro máximo de 11,4±1,1 e 7,0±1,6 mm, respectivamente, desvio observado no dia 3,57±0,53 e fase de platô tendo uma duração média de 4,67±1,37 dias. No segundo padrão irregular observado as ondas foliculares apresentavam duração de 6,44±1,81 dias, com o folículo dominante e maior subordinado alcançando diâmetro de 9,0±0,6 e 6,8±0,4 mm, respectivamente, e com o desvio observado 4,00±1,41 dias após a detecção da onda. O terceiro padrão irregular observado foi caracterizado por períodos repetitivos de crescimento folicular sem a caracterização de fases definidas como descrito para o primeiro e segundo padrões. Em conclusão, do 18º ao 60º dia de gestação, o desenvolvimento folicular é caracterizado por ondas de diferentes padrões no búfalo. Palavras chave Búfalo, Prenhez, Ultrasom, Dinâmica folicular