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We evaluated the effects of nulliparous, primiparous, and multiparous conditions on the estrus and pregnancy rates in females that did not show estrus but were treated with gonadotropin-releasing hormone (GnRH) at the time of timed artificial insemination (TAI). Nelore females (n = 531) were allocated according to the following categories: nulliparous (n = 144), primiparous (n = 132), and multiparous (n = 255). The animals received a conventional TAI protocol, and estrus expression was identified by the absence of paint in the sacrococcygeal region on the day of TAI. Females that did not show estrus were treated with 10 µg of GnRH together with insemination. The rates of estrus and pregnancy were analyzed using a logistic regression model (P < 0.05). The estrus expression was lower (P = 0.006) in the primiparous (61.36%) group than in the nulliparous (76.39%) and multiparous (75.69%) groups. Similar pregnancy rates were observed in females that showed estrus (nulliparous 84.54%, primiparous 86.42%, and multiparous 80.31%; P = 0.39) and in females that did not show estrus and received GnRH (nulliparous 41.18%, primiparous 56.86%, and multiparous 58.06%; P = 0.24). The total pregnancy rates were also similar (P = 0.98) among the categories (nulliparous 74.3%, primiparous 75.0%, and multiparous 74.9%). The primiparous females had a lower rate of estrus, and the pregnancy rates were similar among the categories that received GnRH. O objetivo do trabalho foi avaliar o efeito das categorias nulíparas, primíparas e multíparas sobre a taxa de manifestação de estro e a taxa de prenhez de fêmeas que não manifestaram estro, mas foram tratadas com GnRH no momento da inseminação artificial em tempo-fixo (IATF). Foram utilizadas 531 matrizes, todas da raça Nelore, alocadas de acordo com a categoria: nulíparas (n = 144), primíparas (n = 132) e multíparas (n = 255). As matrizes foram submetidas a um protocolo reprodutivo para inseminação artificial em tempo-fixo (IATF) e tiveram a expressão do estro identificada pela ausência de tinta na região sacrococcígea no dia da inseminação. As fêmeas que não apresentaram estro receberam 10 µg de GnRH no momento que foram inseminadas. As taxas de estro e prenhez foram analisadas por meio de um modelo de regressão logística (P < 0,05). A expressão do estro foi menor (P = 0,006) no grupo de primíparas (61,36%) do que nos grupos de nulíparas (76,39%) e multíparas (75,69%). Taxas de prenhez semelhantes foram observadas em fêmeas que apresentaram estro (nulíparas 84,54%, primíparas 86,42% e multíparas 80,31%; P = 0,39) e em fêmeas que não apresentaram estro e receberam GnRH (nulíparas 41,18%, primíparas 56,86% e multíparas 58,06%; P = 0,24). As taxas de prenhez total também foram semelhantes (P = 0,98) entre as categorias (nulíparas 74,3%, primíparas 75,0% e multíparas 74,9%). As fêmeas primíparas apresentaram menor taxa de estro e as taxas de prenhez foram semelhantes entre as categorias que receberam GnRH.

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.

The objective of this study was to evaluate the efficiency and cost of two distinct hormonal protocols for induction of puberty in Bos indicus heifers in the western Amazon region. Nelore prepubertal heifers (n = 127) aged 20 to 24 months (21 ± 0.3 months) and weighing 300 to 340 kg (318 ± 7 kg) were submitted to two distinct protocols for induction of cyclicity. Females were previously submitted to two ovarian ultrasound examinations (12-day interval) to verify the absence of the corpus luteum (CL). Then, the heifers were divided into two experimental groups: G-CIDR/EC (n = 54) and G-P4/EC (n = 73). The G-CIDR/EC group utilized a CIDR® for 12 days and on the day of its withdrawal, 0.6 mg of estradiol cypionate (IM) was administered. The G-P4/EC group received 150 mg of injectable progesterone (IM) and one injection of 0.6 mg EC 12 days after the progesterone injection. Twelve days after the end of the hormonal protocols, the heifers were submitted to another ultrasound evaluation for identification of cyclicity (ovulatory follicle or CL). These females were then submitted to a conventional protocol of synchronization of ovulation for timed artificial insemination (TAI). Only heifers responsive to puberty induction (G-CIDR/EC (n=30) and G-P4/EC (n=51)) were included in the TAI protocol. After seven days of insemination, both groups were exposed to natural breeding. In addition, an economic analysis was performed to evaluate cyclicity induction, the TAI protocol, and pregnancy in both groups. The G-CIDR/EC group showed 81.48% (44/54) of females responsive to induction of cyclicity (presence of CL) while the G-P4/EC group obtained 86.3% (63/73; p=0.463). Regarding the conception rate to TAI and to bull (natural breeding), the G-CIDR/EC group displayed 43.33% (13/30) and 33.33% (10/30), respectively, and the G-P4/EC group exhibited 54.9% (28/51) and 39.22% (20/51), respectively. The overall pregnancy rate (TAI+Bull) was 76.67% (23/30) in the G-CIDR/EC group compared to 94.12% (48/51; P=0.023) in the G-P4/EC group. The cost of the hormonal protocol to cyclicity induction resulted in an economy of 42.8% for injectable P4 compared to the intravaginal P4 group. In addition, the final cost of cyclic induction associated with TAI was 34% lower in the G-P4/EC group compared to the G-CIDR/EC group. We concluded that both cycling induction protocols were efficient in Bos indicus heifers from the western Amazon. However, injectable P4 provided a higher conception rate and lower pregnancy cost at the end of the reproductive season.

An experiment was performed to evaluate the association between the antral follicle count (AFC) plus body condition score (BCS) and the pregnancy rate in Bos indicus undergoing timed artificial insemination (TAI). A total of 736 Nelore cows with BCSs ranging from 2 to 4 received a conventional protocol for TAI. On a random day of the estrous cycle (Day 0), all cows received an intravaginal P4 device and an intramuscular (i.m.) injection of 2.0 mg estradiol benzoate. On Day 8, the P4 device was removed, and 150 μg sodium D-cloprostenol, 300 IU equine chorionic gonadotrophin and 1.0 mg estradiol cypionate were administered by i.m. injection. TAI was performed 48 h after P4 device removal, and pregnancy diagnosis was performed by ultrasonography after 30 days. On Day 0, all cows were examined by ultrasonography to determine the AFC by counting the number of follicles >3 mm in diameter that were present in both ovaries and to evaluate the BCS (scale of 1–5). The cows were then classified based on their AFCs as those with low (≤10 follicles), intermediate (11–29 follicles) and high AFC (≥30 follicles). Furthermore, cows were classified as having low (≥2.0 to ≤ 2.9) and high (≥3.0 to ≤ 4.0) BCSs. The AFCs and BCSs were analyzed using the generalized linear model, and the pregnancy rate was assessed with the binary logistic regression model (P ≤ 0.05). The pregnancy rate was influenced (P 30 and a BCS between 3 and 4. In conclusion, AFC and BCS classifications influence the pregnancy rate of Bos indicus beef cattle subjected to TAI. In addition, an important interaction between these factors was observed, namely, the lowest pregnancy rates were found in cows with high BCSs and high AFCs.

The livestock sector has achieved many technological advances, which have resulted in continued improvements in animal production systems and in the reproductive efficiency of herds. The associated use of reproductive biotechnology and genetic improvements combined with adequate sanitary and nutritional management are essential conditions for sustainable intensified animal production and financial autonomy within farms. Timed artificial insemination (TAI) represents one of the strategies with the greatest impact of expansion in providing genetic improvements and increased reproductive efficiency at a decreased cost. Despite the high proportion of cows receiving TAI, this market still exhibits considerable potential for expansion. After a TAI procedure, approximately 40 to 60% of females become pregnant. This result can vary depending on such factors as the hormonal protocol employed, female category, body condition score, ovarian status, farm management and aspects related to bulls and semen. The fertility and genetic quality of the bull plays an important role in the herd because a single bull can influence the entire production system. Another important strategy is the use of sex-sorted semen associated with TAI, primarily when associated with management practices to improve the pregnancy rate. This paper presents a review of the intensification of TAI, supplying practical information regarding the implementation of TAI commercial programs.

This research aimed to evaluate the relationship of membrane integrity analysis, mitochondrial cytochemical analysis, and sperm kinetics of bovine semen after thawing and the pregnancy rate in Nelore females submitted to fixed-time artificial insemination (FTAI). Thirty-seven conventional semen straws, from 16 Nelore bulls and 3 Aberdeen Angus bulls were used. The semen samples were evaluated in conventional microscopy for sperm motility, vigor, and morphology, through flow cytometry for membrane integrity and mitochondrial function, and the CASA system for evaluation of sperm kinetics. All females were subjected to the same FTAI protocol and were inseminated by the same technical team. The correlation between all variables was performed by Pearson's correlation. Cluster analysis was used to analyze the relationship between pregnancy rate and combinations of laboratory tests (P ≤ 0.05). Semen samples from Angus bulls (89.2 ± 5.5) presented superior VSL (P=0.004) to Nelore semen (78.6 ± 8.6), but this did not affect the pregnancy rate (Nelore: 51.0% versus Angus: 50.5%, P > 0.05). By flow cytometry, 44.3% membrane integrity and 47.3% mitochondrial integrity were identified. Five clusters were selected, one of which presented the best pregnancy rate, containing the most balanced rates between progressive velocity and mitochondrial activity (VSL 71.16 μm/s, MITO 49.69%, TxP 62.4%). Samples of thawed bovine semen with progressive velocity and balanced mitochondrial activity demonstrated better fertility to TAI program. El objetivo fue evaluar la relación entre el análisis de la integridad de la membrana, la actividad mitocondrial y la cinética de los espermatozoides bovinos, con taxones de preñez en hembras Nellore sometidas a inseminación artificial por tiempo fijo (IATF). Muestras de semen fueron validadas por microscopía óptica para la motilidad, vigor y morfología de los espermatozoides; la citometría de flujo evaluó la integridad de la membrana y la función mitocondrial; y el sistema CASA analizó la cinética de los espermatozoides. Las vacas fueron sometidas al mismo protocolo IATF e inseminadas con el mismo equipo técnico. Una relación entre los diversos se encuentra a través de la correlación de Pearson. Un análisis de conglomerados evaluó la relación entre las tasas de preñez y combinaciones de pruebas in vitro (P ≤ 0,05). Las señales de semen de toros Angus (89,2 ± 5,5) presentarán un VSL más alto (P = 0,004) que el semen de Nelore (78,6 ± 8,6), pero esto no afectó la tasa de preñez (Nelore: 51, 0% frente a Angus: 50,5%, P> 0,05). La citometría de flujo identificó 44,3% de integridad de membrana y 47,3% de integridad mitocondrial. Se seleccionaron cinco grupos, y el grupo que contiene valores más equilibrados entre la velocidad progresiva y la actividad mitocondrial (VSL 71,16 μm / s, MITO 49,69%, TxP 62,4%) demostrarán tasas de preñez más altas. Muestras de semen bovino con taxones progresivos y actividad mitocondrial equilibrada muestran una mejora de la fertilidad para el programa IATF. Objetivou-se avaliar a relação entre a análise de integridade de membrana, atividade mitocondrial e cinética de espermatozoides bovinos pós-descongelação, com a taxa de prenhez em fêmeas Nelore submetidas à inseminação artificial em tempo fixo (IATF). Foram utilizadas 37 doses de sêmen convencional, de 16 touros Nelore e 3 touros Aberdeen Angus. As amostras de sêmen foram avaliadas sob microscopia óptica para motilidade, vigor e morfologia espermática; a citometria de fluxo avaliou integridade de membrana e função mitocondrial; e o sistema CASA analisou a cinética espermática. As vacas foram submetidas ao mesmo protocolo da IATF e inseminadas pela mesma equipe técnica. A relação entre todas as variáveis ​​foi feita por meio da correlação de Pearson. A análise de agrupamento foi usada para avaliar a relação entre a taxa de prenhez e as combinações de teste in vitro (P ≤ 0,05). Amostras de sêmen de touros Angus (89,2 ± 5,5) apresentaram maior VSL (P = 0,004) do que sêmen de Nelore (78,6 ± 8,6), mas isso não afetou a taxa de prenhez (Nelore: 51,0% vs Angus: 50,5%, P > 0,05). Na citometria de fluxo identificou-se 44,3% de integridade de membrana e 47,3% de integridade mitocondrial. Cinco grupos foram selecionados, sendo que o cluster contendo valores mais equilibradas entre velocidade progressiva e atividade mitocondrial (VSL 71,16 μm / s, MITO 49,69%, TxP 62,4%) demonstraram maior taxa de prenhez. Amostras de sêmen bovino descongelado com taxa progressiva e atividade mitocondrial balanceada demonstraram fertilidade melhorada para o programa IATF.

Artificial insemination is a key technique to increase reproductive efficiency and the genetic improvement in cattle. The first report of artificial insemination has been dated to more than 220 years ago; after that, many studies have been published, and this biotechnology is widely used in domestic animals. Despite the advances of embryo transfer programs in vivo and in vitro in cattle, artificial insemination still represents the main form of assisted reproduction in many herds, being one of the lowest cost strategies to improve genetic merit in the farms. Artificial insemination has many advantages compared to natural breeding, such as health benefits, e.g. control of infectious diseases; genetic improvement, e.g. use of genetically improved bulls; reproductive management improvements; and more stringent control of the zootechnical and economic features of the herd, e.g. standardized management and animals.

Made available in DSpace on 2021-06-25T11:02:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In the present study, there was an evaluation of in vitro embryo production (IVEP) in Bos indicus donor cows with small or large antral follicle counts (AFCs) when there was synchronization of follicular dynamics among cows before ovum pick-up (OPU). Donor cows classified as having small or large AFC were submitted to OPU/IVEP program (Experiment-I) or had follicular-stage synchronization imposed before OPU/IVEP (Experiment-II). In Experiment-I, the cows with a large AFC had a greater (P < 0.01) mean of embryos developing to the blastocyst stage compared to those with a small AFC. In Experiment-II, percentage of viable oocytes/OPU were not affected (P = 0.33) by synchronization of follicular dynamics, but the AFC had an effect (P < 0.0001). There was an interaction (P = 0.01) indicating the larger AFC, with or without imposing of a synchronization treatment regimen, resulted in the most desirable outcome. The number of embryos was affected (P < 0.001) by follicular-stage synchronization and AFC, with there being an interaction (P = 0.002) with the most desirable results for the large AFC-synchronized group. Number of pregnancies was greater (P ≤ 0.02) for recipient females with embryos from synchronized donors and with a large AFC. There was an interaction (P = 0.03) with there being a greater pregnancy percentage for cows with synchronized follicular stages and the large AFC. Bos indicus donor with a large AFC when associated with the synchronization of stage of follicular dynamics pre-OPU results in improvement of the efficacy of IVEP. Universidade do Oeste Paulista (UNOESTE) Presidente Prudente National Institute of Science and Technology for Dairy Production Chain (INCT–LEITE) Universidade Estadual de Londrina Rodovia Celso Garcia Cid-Campus Universitário, PO Box 10011 Laboratório de Reprodução Animal DCV-CCA-UEL Laboratório de Reprodução Animal Unicesumar ICETI Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Dracena PROGEST Biotecnologia em Reprodução Animal, Botucatu Qualis In Vitro Presidente Prudente Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Dracena CNPq: 403862/2016-7

This study evaluated the effects of the synchronization of ovarian follicular wave emergence on the efficiency of in vitro embryo production. Bos indicus cows (n = 20) were divided into two groups (control vs. synchronization) and subjected to repeated ovum pick-up (OPU) sessions (8 replicates each, with an interval of 21 days in a 2 × 2 crossover design) and subsequent in vitro embryo production. Cows in the control group (n = 10) were submitted to OPU procedures without any stimulation every 21 days. Animals in the synchronization group received a protocol-based progesterone implant, estradiol benzoate and prostaglandin on a random day of the estrus cycle (Day 0) and the OPU was performed on Day 5. After in vitro production, embryos were transferred to recipients synchronized at a fixed time and the diagnosis was performed 60 days later. An evaluation of the parameters for each OPU session revealed that donors that received the synchronization protocol pre-OPU showed a greater number of embryos (5.9 ± 0.5 vs. 4.5 ± 0.4; P = 0.037), higher rate of embryo production (45.8% vs. 38.5%; P = 0.001) and higher mean number of conceptions per group (2.2 ± 0.2 vs. 1.6 ± 0.2; P = 0.07) in relation to the group that did not receive hormonal treatment. We concluded that synchronization of the follicular wave prior to OPU showed positive effects on in vitro embryo production as well as on pregnancy rates.

The aims of this study were I) to compare the follicular diameter, corpus luteum diameter and serum progesterone (P4) concentrations in cows treated with conventional protocol vs. injectable P4 protocol; II) to determine the serum P4 profile in ovariectomized heifers; and III) to compare pregnancy rate between protocols. In experiment I, multiparous cows received a protocol for ovulation synchronization with an intravaginal P4 device (n = 38; device + EB day 0; device removal + PGF2α + eCG + EC day 8) or injectable P4 (n = 38; injection + EB day 0; PGF2α + eCG + EC day 8). In experiment II, ovariectomized heifers (n = 8) were treated with injectable P4 and blood samples were collected to determine the serum P4 profile. In experiment III, multiparous cows were timed AI with two different P4 approaches, intravaginal P4 device (n = 48) or injectable P4 (n = 47). In the first experiment, cows treated with P4 device had higher (P < 0.05) diameter of dominant follicle after ovulation induction (11.6 ± 1.8 vs.10.3 ± 1.8 mm) and ovulation rate (97%, 37/38 vs. 47.3%, 18/38) than cows treated with injectable P4. But, the follicular growth daily was higher (P < 0.05) in cows treated with injectable P4 than intravaginal device (1.3 ± 0.4 vs. 1.0 ± 0.3 mm/day, respectively). In experiment II, the P4 concentration peak occurred within 48 hours (6.54 ng/mL) and decreased after 96 hours (P < 0.05) after P4 injection. In experiment III, cows with P4 device had higher (P < 0.05) pregnancy rate than the injectable P4 group (60.4 vs. 34.0%, respectively). These results demonstrate that although the intravaginal P4 devices showed a higher pregnancy rate, a protocol with injectable P4 represents an easier method and a promising alternative for TAI in cattle.

This study evaluated the pregnancy rate in Nelore cows (Bos indicus) that were subjected to fixed-time artificial insemination (FTAI) using different protocols consisting of injectable progesterone (P4) or an intravaginal device (impregnated with P4). Multiparous cows 72-84 months in age, 30-45 days postpartum, were selected on the basis of the absence of a corpus luteum (CL) and follicles < 8 mm after transrectal palpation and ultrasound examinations. On a random day of the estrus cycle (D0), the selected animals (n = 135) were randomly assigned to one of three experimental groups (n = 45 each). Group I (injectable P4/FTAI 36 hours) received 250 mg of injectable P4 and 2 mg EB on D0; on D7, they received 500 µg of cloprostenol; on D8, 300 IU of eCG and 1 mg of EB were administered; and finally, FTAI was performed 36 hours after the application of EB. Group II (injectable P4/FTAI 48 hours) received the same protocol as Group I, except that the FTAI was performed 48 hours after ovulation induction. The animals of Group III (Control/CIDR) received a conventional protocol for FTAI using an intravaginal device (D0: P4 and 2 mg EB; D8: device removal, 500 µg cloprostenol, 300 IU eCG, 1 mg EB; and FTAI performed 48 hours after removal of the device). The results showed that cows synchronized with the conventional protocol for FTAI (Control/CIDR) had a higher pregnancy rate (60 %, 27/45) than those synchronized with an injectable P4/FTAI 36 hours (33.33 %; 15/45, P = 0.010). However, the group receiving injectable P4 group/FTAI 48 hours had a similar pregnancy rate (48.9 %; 22/45; P = 0.290) when compared to both the group receiving the conventional protocol and that receiving injectable P4/FTAI 36 hours (P = 0.134). Although the injectable P4 may affect pregnancy rate with the FTAI performed in 36 hours, we found similar pregnancy rates from cows inseminated 48 hours after induction ovulation, considering injectable or intravaginal P4. Therefore, we suggest that injectable P4 represents an alternative source of progesterone for synchronization of cattle for FTAI. Este estudo avaliou a taxa de prenhez de vacas Nelore (Bos indicus) submetidas a diferentes protocolos de IATF a base de progesterona (P4) injetável ou dispositivo intravaginal impregnado com P4. Vacas multíparas entre 72 e 84 meses de idade, com 30 a 45 dias pós-parto foram previamente selecionadas com base na ausência de corpo lúteo (CL) e folículos < 8 mm após palpação e exame ultrassonográfico transretal. Em um dia aleatório do ciclo estral (D0) os animais selecionados (N = 135) foram aleatoriamente distribuídos em um dos três grupos experimentais (N = 45 / grupo). O grupo I (P4 injetável/IATF 36 horas) recebeu 250 mg de P4 injetável e 2 mg BE no D0. No D7 aplicou-se 500 µg de Cloprostenol. No D8 300 UI de eCG e 1 mg de BE foram administrados, sendo que a IATF foi realizada 36 horas após a aplicação do BE. O grupo II (P4 injetável/IATF 48 horas) recebeu o mesmo protocolo de sincronização da ovulação, exceto pela IATF que foi realizada 48 horas após indução da ovulação. Os animais do grupo III (Controle/CIDR) receberam um protocolo convencional de IATF com dispositivo intravaginal (D0 - P4 e 2 mg BE, D8 - remoção do dispositivo, 500 µg Cloprostenol, 300 UI eCG, 1 mg BE e IATF realizada 48 horas após a remoção dos dispositivos). Os resultados foram analisados pelo teste do Qui-Quadrado (p ? 0,05). No estudo, as vacas sincronizadas com protocolo convencional de IATF (Controle/CIDR) apresentaram maior taxa de prenhez (60%; 27/45) do que aquelas submetidas à sincronização da ovulação com P4 injetável/IATF 36 horas (33,33%; 15/45; p = 0,01). Porém, o grupo P4 injetável/IATF 48 horas demonstrou uma taxa de prenhez semelhante (48,9%; 22/45; p = 0,290) ao grupo com protocolo convencional e ao grupo de P4 Injetável/IATF 36 horas (p = 0,134). Embora a P4 injetável demonstrou afetar a taxa de prenhez, as vacas inseminadas 48 horas após a indução da ovulação apresentaram taxas semelhante às vacas que receberam dispositivo intravaginal. Portanto, sugerimos que a P4 injetável representa mais uma fonte progesterônica para sincronização da ovulação em vacas.

Two experiments in Nelore cows subjected to timed artificial insemination (TAI) were designed to compare the influence of the antral follicle count (AFC/AFCs) on (1) ovarian follicular dynamics and (2) conception rates. First, multiparous cows with high (≥45 follicles; n=43) or low (≤15 follicles; n=32) AFCs were selected to undergo a TAI protocol to monitor ovarian follicular dynamics. Second, the AFCs of 962 cows also subjected to TAI were determined and classified as groups of high (G-high; ≥45 follicles; n=194), intermediate (G-intermediate; ≥20≤40 follicles, n=397) or low (G-low; ≤15 follicles; n=243) AFCs. In study I, the ovarian measurements (diameter, perimeter and area) were greater (P≤0.05) and there was a greater consistency in number of antral follicles during the period of synchronization for TAI in the high than low group. Effects of the AFC and ultrasonic evaluation interval on the follicular diameter were observed (P≤0.05); however, there was no interaction (P>0.05). Dominant follicles had greater diameters (P≤0.05) in the G-low than in the G-high at D4 (7.3±2.2 vs. 6.2±1.4mm, respectively, P=0.06), D8 (11.2±1.8 vs. 9.5±1.8mm, respectively), D9 (12.3±1.7 vs. 10.6±1.7mm, respectively), and D10 (13.4±1.3 vs. 12.2±1.8mm, respectively), as well as greater estimated diameters of ovulatory follicles (14.4±1.5 vs. 13.4±2.1mm, respectively, P=0.08). In study II, the cows with fewer AFCs had greater (P≤0.05) conception rates (61.7%) than the cows with the intermediate (52.9%) and greater (49.5%) AFCs. Nelore cows with fewer AFCs subjected to synchronization of time of ovulation had a larger follicular diameter and a greater conception rate than the groups with intermediate and a greater AFCs.

The antral follicle count (AFC) has been pointed out as one of the main factors that influence the efficiency of reproductive biotechniques. Thus, AFC is considered a fertility marker, which has high repeatability in the same animal. The objective of this study was to evaluate AFC in cows at AI (nonpregnant) and at two moments of gestation (30 and 60 days). For this, 35 pregnant cows, aged 23 to 99 months, confined in a freestall system, kept in the same environmental conditions (24°46'28”S, 49°56'42”W) and under the same feeding conditions, were selected for this study. The same technician performed the AI of the females, after detection of natural or induced oestrus, with 25 mg of Dinoprost (Lutalyse) intramuscularly (IM). We established AFC (antral follicles ≥3 mm diameter) using a convex intravaginal transducer at the time of AI and at 30 and 60 days of pregnancy. Females were distributed in groups of low (≤18 follicles, n = 11), intermediate (≥24 and ≤28 follicles, n = 11), or high AFC (≥30 follicles, n = 13). Data were analysed using a generalized linear mixed model (Minitab version 18.1), with significance declared at P ≤ 0.05. In the low AFC group, there was an increase in the mean number of antral follicles in relation to gestation, presenting 14.82 ± 1.36 at the time of AI and 23.45 ± 2.31 and 35.18 ± 3.17 at 30 and 60 days of pregnancy, respectively (P

The objective of this study was to evaluate the reuse of an intravaginal progesterone (P4) device during diestrus of Nelore cow embryo recipients in order to improve conception rate, accelerate estrus cycle re-synchronization of non-pregnant animals, and reduce the amount of waste generated by animal breeding biotechnologies. Two experiments were performed using 268 multiparous Nelore cows. In experiment 1, all animals were subjected to a timed embryo transfer (TET) procedure, but at the time of embryo transfer, two treatment groups were established: T1 - the control treatment (N = 132) and T2 - animals receiving a second-use CIDR® device for 12 days (N = 136). Experiment 2 was performed on cows that had not remained pregnant after experiment 1 using two groups: G1 - a control group (N = 69) and G2 -re-synchronized cows that received a P4 device for 12 days for the first TET (N = 74). In experiment 1, no significant effect of the P4 treatment was observed on conception rate (T1 = 37.9%, T2 = 39.7%; P = 0.50) and corpus luteum (CL) diameter (T1 = 17.5 ± 3.4 mm, T2 = 18.1 ± 3.4 mm; P = 0.61). In experiment 2, no significant effect of the treatment was observed on conception rate (G1 = 22.2%, G2 = 35.7%; P = 0.24), recipients utilization rate (G1 = 75.4%, G2 = 70.3%; P = 0.86), and CL diameter (G1 = 17.4 ± 3 mm, G2 = 18.1 ± 3.2 mm; P = 0.27). However, the P4 treatment (for re-synchronization) significantly increased the conception rate (G1 = 22.2%, G2 = 35.7%; P = 0.04), which was similar to that in a conventional TET protocol performed with a new device (38.8%). We conclude that reusable intravaginal P4 devices can help accelerate TET protocols, suggesting an alternative application method; furthermore, this protocol may help reduce waste production in assisted animal breeding.

The aim of this study was to compare four methods of estrus resynchronization performed 23 days after timed artificial insemination (TAI) plus estrus observation in Bos indicus cows. Eight hundred fourteen lactating Nelore cows were submitted to TAI and then randomly assigned to one of the five following treatments: R23 (resynchronization without eCG), R23/200 (resynchronization with 200 IU of eCG), R23/300 (resynchronization with 300 IU of eCG), R23/TCR (resynchronization with temporary calf removal [TCR]), and a control group, with estrus observation followed by AI (with no resynchronization). Treatment consisted of a progesterone device plus administration of estradiol benzoate on Day 0; on Day 8, the device was removed and cloprostenol was applied, together with estradiol cypionate. Also on Day 8, either eCG was administered or TCR was performed in the resynchronized groups, except for R23. The females were inseminated 48 hours after device removal or TCR (33 days after the first TAI). The control group was kept under estrus observation from 18 to 23 days after the first TAI and was inseminated 12 hours after detection of estrus. The first pregnancy evaluation was performed using ultrasound examination 31 days after the first TAI. After 30 days of the resynchronization, a second pregnancy evaluation was performed and the animals in the R23/300 and R23/TCR groups achieved the highest conception rates, 76.6% and 74.0%, respectively (P0.05). There were no differences between the conception rates of the animals in the R23/200 (63.3%), R23 (61.3%), and control (54.3%) groups (P0.05). These results suggest that estrus resynchronization at 23 days after TAI can effectively improve the conception rate of lactating Bos indicus cows in a short time period. Furthermore, resynchronization with 300 IU of eCG or with TCR provided the best results.

To evaluate the feasibility of long distance transport of ovine oocytes and in vitro produced embryos. Santa Ines pluriparous sheep (n = 5) were synchronized with intravaginal devices containing 0.3 mg progesterone (CIDR®, Pfizer, Netherlands) for 10 days. Thirty-six hours prior to progesterone device removal and follicular aspiration, 0.04 mg d -cloprostenol sodium (Ciosin®, Coopers, Brasil), 200 IU FSH (Folltropin®, Bioniche, Canada) and 300 IU eCG (Novormon®, Syntex, Argentina) were administered intramuscularly. Oocyte retrieval was performed via mid-ventral laparotomy, under general anesthesia. The oocytes were evaluated and classified under a stereomicroscope and placed in cryovials with TCM 199, aerated with 5% CO2, covered with mineral oil, sealed, wrapped with parafilm and stored in a transport incubator at 38.5 °C. Oocytes were then transported via the road for 14 h to the laboratory, where the oocytes then completed more than 10 h of IVM. In vitro fertilization (IVF) was performed with frozen sperm from a single ram. On Day 3 the embryos were placed in cryovials containing SOFovine (In Vitro Brasil, Sao Paulo, Brazil), aerated with 5% CO2, covered with mineral oil, sealed, wrapped with parafilm and placed into the same portable incubator. The embryos were returned to the farm under the same transport conditions (km and h). Upon arrival at the farm, all embryos were evaluated and transferred into recipient ewes 4 days after the initial oocyte retrieval. Embryos were transferred in sets of 3 to 4, into the apex of the uterine horn, ipsilateral to the corpus luteum, by means of mid-ventral laparotomy, under general anesthesia. Pregnancy was diagnosed using transrectal ultrasonography 30 days after embryo transfer. On average 9.8 ± 5.7 oocytes (49 oocytes/5 donors) were obtained per donor, and 25 grade I morulae were transferred into 7 recipients. One pregnancy (14.3%) was confirmed resulting in a healthy lamb. These results indicate the feasibility of in vitro embryo production in sheep after maturation and embryonic development following transport over long distances.

Several studies have indicated the population of antral follicles or count of antral follicles (AFC) as one of the main factors that influence the efficiency of reproductive biotechniques and its use as a marker of fertility. In this context, knowing the factors that interfere with or are influenced by this parameter is of crucial importance. Thus, the present study aimed (1) to determine the influence, in high-producing Holstein cows, of low, intermediate, and high AFC on the conception rate to AI, and (2) to evaluate if AFC shows variation at AI moment and in relation to 2 different moments of the gestation (30 and 60 days). In the first (n=95) and second (n=54) experiment, high-producing Holstein cows with a body condition score 2.5-4.5, aged 23-99 months, and maintained in a freestall system were inseminated. Using frozen semen from a single bull and performed by a single technician, the insemination was performed after detection of spontaneous estrus or induction with 25mg of dinoprost tromethamine IM. To determine AFC (follicles ≥2mm), the ovaries of each animal were examined by ultrasound at the time of AI at 30 and 60 days of pregnancy. The pregnancy diagnosis was performed by ultrasound 30 days after AI. In the second experiment, 54 females considered pregnant on the 30-day examination had the AFC reassessed 30 days later (60 days of gestation) to determine the variation in the number of follicles. In the first study, cows were divided into low (≤35 follicles, n=30), intermediate (≥40 and ≤55 follicles, n=30), and high (≥60 follicles, n=30 cows) according to the AFC quartiles (Q1, Q2, and Q3). The AFC was analysed by ANOVA followed by the Tukey's test and the conception rate by the Chi-squared test. In the second study, the AFC was compared between day of AI (considered nonpregnant), 30 and 60 days of pregnancy by repeated-measures using the generalized linear model (P ≤ 0.05). In the first study, the number of antral follicles was different (P

The aim was to examine the effect of embryo–uterine synchrony on conceptus elongation and pregnancy rate in cattle. In Study 1, crossbred beef heifers each received 10 Day-7 in vitro-produced blastocysts on either Day 5, 7 or 9 after oestrus. A proportion of Day 5 recipients were supplemented with progesterone, via a progesterone-releasing intravaginal device from Days 3–5 plus either 750 IU equine chorionic gonadotrophin or 3000 IU human chorionic gonadotrophin on Day 3. At embryo age Day 14, all heifers were slaughtered and the uterus was flushed. Fewer recipients yielded conceptuses (P

This study was conducted to evaluate the influence of category (heifers, primiparous or multiparous cows) on pregnancy rates in a large scale resynchronization ovulation program. Nelore heifers (n = 903), primiparous lactating cows (n = 338) and multiparous lactating cows (n = 1,223) were synchronized using a conventional protocol of estradiol/P4-based fixed-time artificial insemination (FTAI). Thirty days after ultrasonography, females who failed the first FTAI were resynchronized with the same hormonal protocol prior to a second FTAI. The pregnancy status of each cohort was evaluated by ultrasonography 30 days after each FTAI. The average conception rate after the first FTAI and resynchronization was 80.5%. Heifers had a higher conception rate (85%) than primiparous (76%) or multiparous cows (78%; p = 0.0001). The conception rate after the first FTAI was similar among heifers (57%), primiparous cows (51%) and multiparous cows (56%; p = 0.193). After the second FTAI, heifers exhibited a higher conception rate (66%) than primiparous or multiparous cows (51%; p = 0.0001). These results demonstrate the feasibility of resynchronization in large beef herds for providing consistent pregnancy rates in a short period of time. We also demonstrated that ovulation resynchronization 30 days after FTAI is particularly effective for heifers, providing a conception rate of up to 66%.

The productivity in the herds is directly associated with reproduction. Thus, in order to achieve a better efficiency, the most varied reproductive biotechniques have been applied to the plants. Several factors have a direct influence on reproductive performance, including genetics, nutrition, zootechnical management, and sanitation. However, the sanity of the herd through the use of prophylactic measures against infectious agents is often neglected. In this context, particular attention should be paid to health programs, since 37-50% of gestational losses in the herd are consequences of infectious diseases of the reproductive tract caused by viral, bacterial or protozoan agents. Thus, this review will discuss the main advantages obtained with the use of reproductive biotechniques to increase fertility and the epidemiological aspects related to the diseases that cause reproductive failures in cows. Finally, we will also explain the importance of implementing sanitary programs with adequate management and vaccination of animals, to minimize economic losses related to reproductive diseases and, consequently, obtain higher pregnancy rates in the use of reproduction biotechnologies.

Obtaining sexed sperm from previously frozen doses (reverse-sorted semen [RSS]) provides an important advantage because of the possibility of using the semen of bulls with desired genetic attributes that have died or have become infertile but from whom frozen semen is available. We report the efficiency of RSS on the pregnancy rate and birth rate of calves in a large-scale program using ovum pick-up and in vitro embryo production (IVEP) from Bos indicus, Bos indicus-taurus, and Bos taurus cattle. From 645 ovum pick-up procedures (Holstein, Gir, and Nelore), 9438 viable oocytes were recovered. A dose of frozen semen (Holstein, Nelore, Brahman, Gir, and Braford) was thawed, and the sperm were sex-sorted and cooled for use in IVF. Additionally, IVF with sperm from three Holstein bulls with freeze-thawed, sex-sorted (RSS) or sex-sorted, freeze-thawed (control) was tested. A total of 2729 embryos were produced, exhibiting a mean blastocyst rate of 29%. Heifers and cows selected for adequate body condition, estrus, and health received 2404 embryos, and 60 days later, a 41% average pregnancy rate was observed. A total of 966 calves were born, and 910 were of a predetermined sex, with an average of 94% accuracy in determining the sex. Despite the lower blastocyst rate with freeze-thawed, sex-sorted semen compared with sex-sorted semen, (P < 0.05), the pregnancy rate (bull I, 45% vs. 40%; II, 35% vs. 50%; and III, 47% vs. 48% for RSS and control, respectively; P > 0.05) and sex-sorted efficiency (bull I, 93% vs. 98%; II, 96% vs. 94%; and III, 96% vs. 97% for RSS and control, respectively; P > 0.05) were similar for each of the three bulls regardless of the sperm type used in the IVF. The sexing of previously frozen semen, associated with IVEP, produces viable embryos with a pregnancy rate of up to 40%, and calves of the desired sex are born even if the paternal bull has acquired some infertility, died, or is located a long distance from the sexing laboratory. Furthermore, these data show the feasibility of the process even when used in a large-scale IVEP program.