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This study evaluated the efficacy of the administration of different doses of equine chorionic gonadotropin (eCG; 0 IU, 200 IU, or 300 IU) at the time of the progesterone device removal in 2-year-old Nelore (Bos indicus) heifers synchronized for fixed-timed artificial insemination (FTAI). On day 0 (D0), a total of 398 heifers received 2 mg of oestradiol benzoate i.m., 0.53 mg of cloprostenol i.m., and an eight-day previously used (second use) intravaginal device containing 1 g of progesterone (P4). Eight days later (D8), simultaneous with the P4 device removal, 0.5 mg of oestradiol cypionate i.m. and 0.53 mg of cloprostenol i.m. were administered. At the same time, heifers were randomly assigned to receive one of the following treatments: G-0 IU (n = 141; no eCG treatment), G-200 IU (n = 132; treated with 200 IU of eCG), and G-300 IU (n = 125; treated with 300 IU of eCG). FTAI was performed 48 h after the P4 device removal (D10). Ultrasonographic evaluations were performed at D0, D10, and D17. Heifers were scanned to measure the size of the largest follicle (LF), the presence, number, and size of the corpus luteum (CL), and the ovulation rate. Subsequently, at D40, the heifers underwent scanning to determine the pregnancy rate and identify any twin pregnancies. Additionally, at D70, scans were performed to assess pregnancy loss (PG). Data were analysed by orthogonal contrasts [C1 (eCG effect): control x (200 IU + 300 IU) and C2 (eCG dose effect): 200 IU × 300 IU]. On D0, CL presence was similar between the groups [G-0 IU = 65.2% (92/141), G-200 IU = 55.3% (73/132), and G-300 IU = 63.2% (79/125); p = .16]. No interactions between the presence of CL on D0 and eCG treatment were found for any of the variables (p > .05). The diameter of the LF at FTAI (D10) was not influenced by eCG treatment (p = .22) or eCG dose (p = .18). However, treatment with eCG increased the diameter of the CL at D17 (G-0 IU = 15.7 ± 0.3 mmb , G-200 IU = 16.6 ± 0.2 mma , and G-300 IU = 16.6 ± 0.3 mma ; p = .001), regardless of the dose used (p = .94). The ovulation rate was higher in heifers treated with eCG [G-0 IU = 79.4%b (112/141), G-200 IU = 90.2%a (119/132), and G-300 IU = 93.6%a (117/125); p = .002], but there was no effect of eCG dose (p = .36). Pregnancy per AI (P/AI) on D40 [G-0 IU = 32.6%b (46/141), G-200 IU = 42.4%a (56/132), and G-300 IU = 42.4%a (53/125); P = 0.05] and D70 [G-0 IU = 29.1%b (41/141), G-200 IU = 40.9%a (54/132), and G-300 IU = 40.8%a (51/125); p = .02] were higher on heifers that received eCG; however, no dose effect was observed for P/AI on D40 (p = .89) nor D70 (p = .98). Pregnancy loss between D40 and D70 tended to reduce (p = .07) in eCG-treated heifers without dose effect (p = .91). Heifers with CL at D0 presented a greater follicle diameter (LF) on D10 (With CL = 11.2 ± 0.2 mm and Without CL = 10.2 ± 0.2 mm; p = .05), CL diameter on D17 (With CL = 15.8 ± 0.03 mm and Without CL = 11.8 ± 0.6 mm; p = .01), and ovulation rate [With CL = 95.5% (233/244) and Without CL = 74.7% (115/154); p = .01]. However, no difference in pregnancy rate at D40 (p = .52) and D70 (p = .84) was found. In conclusion, eCG treatment increases ovulation and pregnancy rates of heifers submitted to a FTAI protocol. Furthermore, eCG treatment increases the diameter of the CL after FTAI and reduces pregnancy losses. No dose effect was observed, suggesting Nelore (Bos indicus) heifers respond to 200 IU of eCG treatment for FTAI.

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Effects were evaluated in Bos indicus cows of eCG and FSH on follicular growth, estrous expression, and pregnancy per artificial insemination (P/AI) as a result of fixed-time artificial insemination (TAI). In Experiment 1, extent of timing-of-ovulation synchronization among cows was evaluated after imposing an estrogen/progesterone-based treatment regimen. At progesterone device removal (D8), cows were administered: eCG, or FSH or served as untreated Controls. In Experiment 2, percentage of cows P/AI was evaluated when the Experiment 1-treatment regimen was imposed. On D10, all cows were artificially inseminated. In Experiment 3, cows were assigned to two treatment groups (Control and eCG) on D8 to evaluate percentage of cows P/AI and estrous expression. In Experiment 1, follicular dynamics were similar among treatment groups. In Experiment 2, follicular growth was greater (P = 0.0001) with the eCG treatment. There was an interaction of treatment × parity (P = 0.007) on percentage of cows P/AI. There was a greater percentage of primiparous cows P/AI in the eCG-treated than Control and FSH-treated cows. There was a greater percentage of eCG-treated multiparous cows pregnant as a result of TAI than Control cows. There was an interaction of treatment × parity (P = 0.005) on P/AI in Experiment 3, in which the eCG effect was more pronounced in primiparous cows. Treatment with FSH, therefore, was not as effective as eCG in stimulation of follicular growth or enhancing percentage of cows pregnant as a result of TAI. Physiological effects of eCG, however, were also more evident in primiparous cows.

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This study aimed to minimize the number of times cattle need to be confined during protocols for TAI in beef cows treated for induction of ovulation with EB at the time of P4 device removal (P4r). In Experiment 1, cows were treated with P4 plus EB (Day 0; AM) and were allocated to one of three groups at P4r: EB8.5, EB at P4r on Day 8.5 (PM; three confinements); EB9, EB 24 h after P4r on Day 8 (AM; four confinements) and EC8, EC at P4r on Day 8 (AM; positive control; three confinements). At P4r, cows were treated with PGF2a plus eCG. Ultrasonography was performed from D8 to D12. The interval from P4r to ovulation was less in the EB8.5 compared to EB9 and EC8 group. There was no difference in the ovulation rate between groups. The variability of ovulation was greater in the EB8.5 and EC8 compared to EB9 group. In Experiment 2, cows of EC8 and EB9 groups were submitted to TAI 48 to 52 h (AM) or 54 to 58 h (PM) after P4r (D10). Cows of the EB8.5 group were submitted to TAI 38 to 42 h (AM) or 44 to 48 h (PM) after P4r (D10). There was no interaction between treatments and timing of AI and no treatment effect and timing of AI on P/AI. In conclusion, the delay compared to what typically occurs by 10 h of P4r concomitant with EB administration (Day 8.5) reduced the frequency of animal confinement for the TAI protocol without affecting the reproductive efficiency and the flexibility to perform the TAI in suckled beef cows.

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The objective was to compare the fertility of dairy cows using a presynchronization protocol by induction of a largest follicle using a progesterone intravaginal device prior to an Ovsynch protocol (P4synch) with the Double-Ovsynch in lactating dairy cows. Lactating Bos indicus x Bos taurus crossbred cows (n = 440) were randomly allocated to one of two treatments: (I) Double-Ov (n = 228), GnRH (D-17), PGF2α 7 days later (D-10) and GnRH 3 days later (D-7) followed by an Ovsynch protocol 7 days later (GnRH on D0, PGF on D7, GnRH on D9); (II) P4synch (n = 212), insertion of a sustained release progesterone intravaginal device (D-10), 10 days later (D0) an Ovsynch protocol was initiated (GnRH on D0, PGF on D7, GnRH on D9) with progesterone device withdrawal on Day 7. All cows were artificially inseminated (TAI) 16 h after the second GnRH of the Ovsynch protocol and pregnancy diagnosis was performed by transrectal ultrasonography 30 and 60 days after TAI. A subset of cows (n = 52 for Double-Ov and n = 50 for P4synch) ultrasonography was performed on days 0, 7, 9 and 24 of the experimental period. There were no differences among treatments on presynchronization rate [presence of a follicle>12 mm on D0, Double-Ov 94.2% (49/52) and P4synch 92.0% (46/50); P = 0.66], follicular diameter on the 1st GnRH (Double-Ov 17.2 ±â€¯0.7 mm e P4synch 18.6 ±â€¯0.9 mm; P = 0.28), ovulation rate to the 1st GnRH [Double-Ov 86.3% (44/51) and P4synch 81.2% (39/48); P = 0.50], synchronization rate [presence of a follicle>12 mm on D9; Double-Ov 84.6% (44/52) and P4synch 86.0% (43/50); P = 0.84], follicular diameter on the 2nd GnRH (Double-Ov 17.5 ±â€¯0.6 mm and P4synch 18.0 ±â€¯0.5 mm; P = 0.48), ovulation rate to the 2nd GnRH [Double-Ov 90.9% (40/44) and P4synch 86.0% (37/43); P = 0.48] and CL diameter on D24 (Double-Ov 27.9 ±â€¯0.7 mm and P4synch 29.4 ±â€¯0.9 mm; P = 0.19). Corpus luteum presence on D0 was different (P = 0.03) among treatments [Double-Ov 57.7% (30/52) and P4synch 36.0% (18/50)]. There was no difference (P = 0.85) among the pregnancy per AI on day 30 [Double-Ov 39.0% (89/228) and P4synch 40.1% (85/212)], on day 60 [Double-Ov 34.8% (79/227) and P4synch 38.7% (82/212); P = 0.41] and pregnancy loss [Double-Ov 10.2% (9/88) and P4synch 3.5% (3/85); P = 0.08]. The presynchronization by induction of a largest follicle using a sustained release progesterone device prior to Ovsynch yielded similar results compared with the Double Ovsynch protocol on follicular development patterns and on the fertility of lactating dairy cows.

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The growth profiles of the future dominant follicle (DF) and subordinate follicle (SF) and the gene expression of the granulosa cells during luteolysis induction in Bos indicus cows were evaluated. Forty cows were synchronized with a progesterone and estradiol based protocol. After synchronization, cows with a corpus luteum (CL) were evaluated by ultrasonography every 12 h, beginning at eight days post ovulation. Cows identified with a follicle of at least 6.0 mm in diameter in the second wave were split into two groups (BD-before follicular deviation and AD-after follicular deviation. In the BD group cows received 500 µg of cloprostenol (a synthetic analogue of prostaglandin F2α) when the DF reached a mean diameter of 7.0 mm (6.5-7.5 mm). In the AD group, cows received 500 µg of cloprostenol when the DF reached a mean diameter of 8.0 mm (7.5-8.5 mm). Cows in both groups were submitted to aspiration of the DF at 96 and 72 h after prostaglandin was given. Follicular aspirations were performed to quantify IGF1R, LHR and PAPPA transcripts in the granulosa cells. The diameter of the DF at the moment of prostaglandin administration (P = 0.001) and the growth rate of the SF (P = 0.05) were greater in the AD group. There was greater abundance of LHR transcripts in BD cows (P = 0.04). The remaining variables tested were similar between the experimental groups (P > 0.05). In conclusion, the induction of luteolysis before follicular deviation does not interfere with dominant follicle dynamics. However, it causes granulosa cell LHR down regulation.

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The aim of this study was to evaluate hCG treatment on ovarian response and on pregnancy rate using a 9-day oestrus synchronization protocol in Santa Ines ewes. On a random oestrus cycle day, ewes received an intravaginal progesterone device (Primer-PR®, Tecnopec, Brazil). Nine days later (Day 9), 30µg of d-cloprostenol (Prolise®, Syntex, Argentina) and 250IU of eCG (Folligon®, Intervet, Brazil) were administered and the progesterone device was removed. This moment, the ewes were randomly assigned on two groups: Control Group and hCG Group. In the hCG Group, the ewes received 500IU of hCG (Vetecor®, Hertape-Calier, Spain) 24h after device removal. In the Control Group, the ewes did not receive any ovulation inductor. Control and hCG Groups ewes were inseminated 60h and 48h after device removal, respectively. There was no difference between the groups regarding the first ovulatory follicle diameter and the second ovulatory follicle. hCG Group ewes had shorter interval between device removal and ovulation (Control: 79.9±15.4h and hCG: 54.7±4.9h; P=0.001) and more synchronized ovulations. However, the treatment with hCG decreased the pregnancy rate after TAI (P=0,009). In conclusion, hCG administration improves ovulatory synchronisation, but causes a decrease in the pregnancy rate.(AU)

Avaliou-se o tratamento com hCG na resposta ovariana e na taxa de prenhez utilizando protocolo de sincronização do estro de nove dias em ovelhas Santa Inês. As ovelhas receberam um dispositivo intravaginal de progesterona em fase aleatória do ciclo (dia zero= D0). No momento da remoção do dispositivo (D9), as fêmeas receberam 30µg de d-cloprostenol (Prolise®, Syntex, Argentina) e 250UI de eCG (Folligon®, Intervet, Brasil). Nesse momento, as ovelhas foram aleatoriamente distribuídas em dois grupos de tratamento: controle sem indução de ovulação e tratamento com 500UI hCG para indução de ovulação. As ovelhas dos grupos controle e hCG foram inseminadas 60h e 48h após a remoção do dispositivo, respectivamente. Não houve diferença entre os grupos para o diâmetro do primeiro e do segundo folículo pré-ovulatório. As avelhas do grupo hCG apresentaram menor intervalo entre a remoção do dispositivo e a ovulação (grupo controle: 79.9±15.4h e grupo hCG: 54.7±4.9h; P=0.001) e maior sincronização das ovulações. No entanto, o tratamento com hCG diminuiu a taxa de prenhez após a IATF (P=0,009). Conclui-se que, apesar de a administração de hCG aumentar a sincronização da ovulação, reduz a taxa de prenhez.(AU)

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The aim of this study was to evaluate hCG treatment on ovarian response and on pregnancy rate using a 9-day oestrus synchronization protocol in Santa Ines ewes. On a random oestrus cycle day, ewes received an intravaginal progesterone device (Primer-PR®, Tecnopec, Brazil). Nine days later (Day 9), 30µg of d-cloprostenol (Prolise®, Syntex, Argentina) and 250IU of eCG (Folligon®, Intervet, Brazil) were administered and the progesterone device was removed. This moment, the ewes were randomly assigned on two groups: Control Group and hCG Group. In the hCG Group, the ewes received 500IU of hCG (Vetecor®, Hertape-Calier, Spain) 24h after device removal. In the Control Group, the ewes did not receive any ovulation inductor. Control and hCG Groups ewes were inseminated 60h and 48h after device removal, respectively. There was no difference between the groups regarding the first ovulatory follicle diameter and the second ovulatory follicle. hCG Group ewes had shorter interval between device removal and ovulation (Control: 79.9±15.4h and hCG: 54.7±4.9h; P=0.001) and more synchronized ovulations. However, the treatment with hCG decreased the pregnancy rate after TAI (P=0,009). In conclusion, hCG administration improves ovulatory synchronisation, but causes a decrease in the pregnancy rate.(AU)

Avaliou-se o tratamento com hCG na resposta ovariana e na taxa de prenhez utilizando protocolo de sincronização do estro de nove dias em ovelhas Santa Inês. As ovelhas receberam um dispositivo intravaginal de progesterona em fase aleatória do ciclo (dia zero= D0). No momento da remoção do dispositivo (D9), as fêmeas receberam 30µg de d-cloprostenol (Prolise®, Syntex, Argentina) e 250UI de eCG (Folligon®, Intervet, Brasil). Nesse momento, as ovelhas foram aleatoriamente distribuídas em dois grupos de tratamento: controle sem indução de ovulação e tratamento com 500UI hCG para indução de ovulação. As ovelhas dos grupos controle e hCG foram inseminadas 60h e 48h após a remoção do dispositivo, respectivamente. Não houve diferença entre os grupos para o diâmetro do primeiro e do segundo folículo pré-ovulatório. As avelhas do grupo hCG apresentaram menor intervalo entre a remoção do dispositivo e a ovulação (grupo controle: 79.9±15.4h e grupo hCG: 54.7±4.9h; P=0.001) e maior sincronização das ovulações. No entanto, o tratamento com hCG diminuiu a taxa de prenhez após a IATF (P=0,009). Conclui-se que, apesar de a administração de hCG aumentar a sincronização da ovulação, reduz a taxa de prenhez.(AU)

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The success of IVP is ultimately dependent on the number and quality of the cumulus-oocyte complexes (COC) harvested during the OPU procedure. Several factors appear to be critical to oocyte quality including follicle size, environment factors such as heatstress, genetic background, age and lactation status of donor animals, all having a remarkable influence on the results of IVP. The aim of this review is to highlight some critical areas that can help veterinary practitioners to enhance OPU efficiency and successfully implement IVP into their routine practice. Focus will be given to recent findings in the literature and underlying physiological aspects that may be interfering with the quality of oocytes addressed to IVP in cattle at younger ages (calves and prepubertal heifers), pregnant vs nonpregnant status, and possible interactions with lactation and days postpartum during OPU.

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RESUMO

The success of IVP is ultimately dependent on the number and quality of the cumulus-oocyte complexes (COC) harvested during the OPU procedure. Several factors appear to be critical to oocyte quality including follicle size, environment factors such as heatstress, genetic background, age and lactation status of donor animals, all having a remarkable influence on the results of IVP. The aim of this review is to highlight some critical areas that can help veterinary practitioners to enhance OPU efficiency and successfully implement IVP into their routine practice. Focus will be given to recent findings in the literature and underlying physiological aspects that may be interfering with the quality of oocytes addressed to IVP in cattle at younger ages (calves and prepubertal heifers), pregnant vs nonpregnant status, and possible interactions with lactation and days postpartum during OPU.(AU)

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The objectives were to evaluate the effects of the administration of either eCG or progesterone (P4) alone or combined on endogenous P4 concentrations and pregnancy per AI in lactating dairy cows. Cows received a P4-releasing intravaginal device (PRID) and estradiol benzoate on D-8. The PRID was removed and a PGF2α injection was given on D-3. An estradiol cypionate was given on D-2 and TAI was performed on D0. On D-2, cows were randomly allocated to treatments in a 2×2 factorial design: Control-saline solution on the D-2 and D+3 (n=104), eCG - 400IU eCG on D-2 (n=93), P4 - 600mg of P4 on D+3 (n=106), and eCG+P4 - 400IU eCG on D-2 and 600mg of P4 on D+3 (n=95). Blood samples were collected on days three, four, and thirteen and pregnancy diagnoses were performed at 32 and 46 days after AI. There was no interaction between eCG and P4 injection. Cows treated with eCG and with P4 injection had higher serum P4 on Day +4. On Day +13 serum P4 was lower in eCG-untreated primiparous cows (Interaction eCG×parity). Cows with serum P4<4.57ng/mL on Day +13 had lower probability to be pregnant on day 32. P/AI on days 32 and 46 and embryonic losses were not influenced by eCG and P4 injection. In conclusion, the addition of 400IU of eCG on D-2 and/or 600mg of P4 on D+3 to the present TAI protocol did not increase P/AI.

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