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The aim of this study was to evaluate follicular dynamics and ovum pick-up (OPU) efficacy in untreated mares or mares treated with an intravaginal progesterone (P4) device during seasonal anestrus (acyclic) and during the breeding season (cyclic). Six mares (mean age = 5 years), were recruited into an ovum pick-up scheme that was performed every 14 days with and without the P4 device, during the acyclic and cyclic phases. Aspirations amounted to seven procedures with or without the P4 device during each phase. Five ultrasound assessments were performed at each interval between the OPUs. Data on follicular number and diameter as well as the numbers of recovered and the percentage of recovered oocytes were also collected. The number of follicles from mares in the acyclic phase was higher (P < .005) regardless of the treatment. However, the follicular diameter was smaller for the P4 group (P < .005) from the 2nd to the 5th evaluation post-OPU procedure. The percentage of oocytes recovered during the acyclic phase was higher for mares treated with the P4 device (P < .005). The P4 device resulted in follicles with smaller diameters and facilitated OPU efficacy.

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This study compared the reproductive performance of embryo recipients treated with a timed embryo transfer (TET) protocol using human chorionic gonadotropin (hCG) or equine chorionic gonadotropin (eCG). On a random day of the estrous cycle (Day -10) indicus-taurus recipients (n = 341; 194 nulliparous and 147 multiparous cows) with a body condition score between 3.0 and 4.0, were submitted to the TET protocol consisting of an intramuscular (i.m.) injection of 2.0 mg estradiol benzoate (EB) and the insertion of intravaginal progesterone (P4) device that remained until Day -2.5. On the same day (-2.5), the recipients received i.m. 150 mg D-cloprostenol and 1 mg estradiol cypionate and were randomly divided into two groups: the eCG group (n = 179), in which females received i.m. 300 IU eCG and the hCG group (n = 162), in which females received 150 IU hCG. Then, estrus intensity and the diameter of the dominant follicle (DF) were monitored on D0 and the quality of the corpus luteum (CL) (B mode and color Doppler) was assessed on D7 to select recipients eligible for receiving the transfer of an embryo produced in vitro. Pregnancy diagnosis was assessed 23 days after the transfer. Continuous data were analyzed by ANOVA using a mixed-effects model and Tukey's test. The rates were analyzed using a logistic regression model. The diameter of the DF on day 0 of the TET protocol was influenced by the interaction between gonadotropic treatment and category (P = 0.01), and nulliparous recipients treated with hCG had the smallest diameter. Treatment with hCG and eCG resulted in a high rate of estrus expression; however, the proportion of females with a high-intensity of estrus was higher in the hCG group (79.84 vs. 68.61%, respectively; P = 0.03). The utilization rate (recipients with CL) showed a tendency (P = 0.06) to be influenced by the interaction between gonadotropic treatment and category, wherein nulliparous recipients treated with hCG exhibited a lower utilization rate than the other groups. The diameter, perimeter, and area of the CL were similar (P > 0.1) in all groups. However, the hCG group resulted in CL with a better Doppler evaluation score (P = 0.04), central blood flow (P = 0.03), and tendency towards greater peripheral blood flow (P = 0.08). The rates of conception (32.00% hCG vs. 35.10% eCG; P = 0.46) and pregnancy (24.69% hCG vs. 29.61% eCG; P = 0.20) were similar between the hCG and eCG groups. However, an interaction between the gonadotropic treatment and category revealed lower conception (P = 0.01) and pregnancy rates (P = 0.001) in nulliparous recipients treated with hCG. Treatment with hCG resulted in a greater intensity of estrus expression and CL with a higher Doppler score, which determined rates of utilization, conception, and pregnancy similar to conventional protocols using eCG. However, nulliparous recipients treated with hCG exhibited a lower overall reproductive rate.

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Reproductive biotechnologies are emerging as an important element for livestock; however, some strategies must be modified to adapt to different breeding systems, such as the use of follicular synchronization protocols. This study aimed to evaluate follicular synchronization using estradiol benzoate (EB), in the presence of the corpus luteum (CL) from Wagyu oocyte donors in in vitro embryo production (IVEP). Rounds of IVEP were performed in heifers and cows (n=19) that were classified into three groups: G1/CL - animals with CL, G2/WCL - animals without CL, and G3/CL + EB - animals with CL that were subjected to follicular synchronization with EB at D0. The groups G1/CL and G2/WCL were considered the control and undertook the natural process of follicular dynamics. The results showed that the synchronization of the follicular wave with the application of EB in the presence of CL, presented a smaller number of small (6.05 ± 0.55) and large follicles (0.45 ± 0.15), but increased (P < 0.05) the number of medium-sized follicles (16.20 ± 0.90). However, the results of ovum pick up showed that regardless of whether or not EB was applied, and regardless of the presence or absence of CL in the Wagyu donor, there was no difference among the groups (P > 0.05) concerning the number of viable oocytes and the viability rate. It was concluded that follicular synchronization using EB in Wagyu oocyte donors that presented a CL, increased the number of medium-sized follicles. However, there was no improvement in the efficiency of ovum pick up, in vitro embryo production, and pregnancy rate.(AU)

As biotecnologias reprodutivas estão emergindo como um elemento importante para a pecuária, entretanto, algumas estratégias devem ser modificadas para se adaptar a diferentes sistemas de criação, como o uso de protocolos de sincronização folicular. Este estudo teve como objetivo avaliar a sincronização folicular utilizando benzoato de estradiol (BE), na presença do corpo lúteo (CL) de doadoras de oócitos Wagyu na produção in vitro de embriões (PIVE). Sessões de PIVE foram realizadas em novilhas e vacas (n=19) que foram classificadas em três grupos: G1/CL - animais com CL, G2/SCL - animais sem CL e G3/CL+BE - animais com CL que foram submetidos para sincronização folicular com BE em D0. Os grupos G1/CL e G2/ SCL foram considerados o controle e realizaram o processo natural da dinâmica folicular. Os resultados mostraram que a sincronização da onda folicular com a aplicação de BE na presença de CL, apresentou um menor número de folículos pequenos (6,05 ± 0,55) e grandes (0,45 ± 0,15), mas aumentou (P < 0,05) o número de folículos de tamanho médio (16,20 ± 0,90). No entanto, os resultados da ovum pick up mostraram que independente da aplicação ou não de BE, e independente da presença ou ausência de CL na doadora Wagyu, não houve diferença entre os grupos (P > 0,05) quanto ao número de oócitos viáveis e a taxa de viabilidade. Concluiu-se que a sincronização folicular por meio de BE em doadoras de oócitos Wagyu que apresentaram CL, aumentou o número de folículos de tamanho médio. No entanto, não houve melhora na eficiência da ovum pick up, na produção in vitro de embriões e na taxa de prenhez.(AU)

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BACKGROUND: Age and antral follicle count (AFC) are related to fertility in cattle, but this information remains limited in mares. METHODS: To verify the influence of age and AFC on the reproductive characteristics of mares, 15 Quarter Horse donors, with 5-15 antral follicles, ranging from three to 17 years old, healthy and in good nutritional status, were divided into groups with low AFC (≤9 follicles) or high AFC (≥10 follicles) and mares considered young (≤9 years) or old (≥10 years). Mares were submitted to ultrasonography to determine the dominant follicle diameter, follicular growth rate, degree of uterine oedema and embryonic recovery for a minimum of three oestrous cycles. RESULTS: AFC was higher (P=0.001) in young mares compared with old mares. An interaction (P=0.001) between AFC and age was observed with regard to follicular growth rate, being that mares with low AFC and are old showed the lowest follicular growth compared with those of low AFC and young, high AFC and old, and high AFC and young. Younger mares and those with high AFC exhibited higher degree of uterine oedema (P<0.05) on the third day of oestrus compared with older mares and with low AFC (3 and 2, respectively). However, in both groups, the degree of oedema reduced by the time of ovulation. CONCLUSION: Follicular growth rate, degree of uterine oedema and the number of antral follicles are higher in young mares with high AFC. However, the rate of embryonic recovery is not influenced by donors' age or AFC.

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