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Silva LOE, Motta JCL, Oliva AL, Madureira G, Alves RLOR, Folchini NP, da Silva MA, da Silva TJB, Consentini CEC, Wiltbank MC, Sartori R. Influence of GnRH analog and dose on LH release and ovulatory response in Bos indicus heifers and cows on day seven of the estrous cycle. Theriogenology 2024; 214:215-223. [PMID: 37924738 DOI: 10.1016/j.theriogenology.2023.10.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 09/08/2023] [Accepted: 10/13/2023] [Indexed: 11/06/2023]
Abstract
This study evaluated the influence of GnRH analogs (gonadorelin vs. buserelin) and doses (single vs. double) on LH release and ovulatory response in Bos indicus (Nelore) females on Day 7 of the estrous cycle. Cycling heifers and non-lactating cows were pre-synchronized: Day -10: progesterone (P4) implant insertion plus 2 mg of estradiol benzoate; Day -2: implant removal and 0.53 mg of cloprostenol sodium (PGF); Day 0: 25 μg of lecirelin (GnRH). Over four replicates, heifers (n = 57) and cows (n = 53) that ovulated to the GnRH treatment on Day 0, having a visible corpus luteum (CL) and a dominant follicle (DF) ≥ 8.5 mm, were allocated to receive the following GnRH treatments on Day 7: G-Single (100 μg of gonadorelin); G-Double (200 μg of gonadorelin); B-Single (10 μg of buserelin); and B-Double (20 μg of buserelin). At GnRH treatment, a P4 implant was inserted in heifers (0.5 g) and cows (1 g). Ultrasound examinations were done on Days -10, -2, 0, 2, 7, 9, 12, and 14 to evaluate DF diameter, ovulation and presence of CL. Blood samples were collected on Day 7 at 0, 2, and 4 h from GnRH treatment, to evaluate circulating P4 and LH concentrations. On Day 12, the P4 implant was removed, females received two PGF treatments (24 h apart), and 2 d later, 25 μg of GnRH was given to start the next replicate. In both heifers and cows, P4 concentrations were elevated on Day 7, and similar among groups (3.9 and 4.2 ng/mL, respectively). In heifers, buserelin induced greater LH peak (9.5 vs. 2.6 ng/mL; P < 0.01) and greater ovulation (88.9 [24/27] vs. 16.7% [5/30]; P < 0.01) than gonadorelin treatments, regardless of the dose. Similarly, in cows, buserelin induced greater LH peak than gonadorelin (9.9 vs. 4.9 ng/mL; P < 0.01). However, ovulation was only increased in cows from the B-Double group (90.9% [10/11]), whereas in the other groups the ovulatory response was similar (35.7% [15/42]). Regardless of treatment, heifers had similar P4 concentrations (P = 0.22), but smaller DF (P < 0.01) than cows on Day 7. Only in G-Double group the LH peak was lower (P = 0.05) in heifers than in cows, with no difference within other groups. In heifers, but not in cows, the single dose of buserelin resulted in high ovulatory response, equivalent to that produced by the double dose. In conclusion, in Bos indicus heifers and cows on Day 7 of the cycle, with elevated P4 concentrations, buserelin induced greater LH release and ovulatory response than gonadorelin treatments. Double doses increased the LH release, however, only resulted in greater ovulation in females treated with buserelin. Finally, although circulating P4 concentrations did not differ between parities, heifers were more likely to ovulate in response to a GnRH-induced LH peak than cows.
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Affiliation(s)
- Lucas O E Silva
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Jessica C L Motta
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Abraham L Oliva
- Faculty of Higher Studies Cuautitlán, National Autonomous University of Mexico, Cuautitlán Izcalli, 54714, Mexico
| | - Guilherme Madureira
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Rodrigo L O R Alves
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Natália P Folchini
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Mateus A da Silva
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Taynara J B da Silva
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Carlos E C Consentini
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil
| | - Milo C Wiltbank
- Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Roberto Sartori
- Department of Animal Science, Luiz de Queiroz College of Agriculture of University of São Paulo (ESALQ/USP), Piracicaba, SP, 13418-900, Brazil.
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Reineri PS, Bernhard SDR, Principi SA, Gerlero GD, Aller JF. Effects of two protocols of ovulation synchronization on corpus luteum size and blood flow, progesterone concentration, and pregnancy rate in beef heifers. Anim Reprod Sci 2023; 251:107223. [PMID: 36965397 DOI: 10.1016/j.anireprosci.2023.107223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 03/06/2023] [Accepted: 03/19/2023] [Indexed: 03/27/2023]
Abstract
The objective of this study was to evaluate the effect of 7-day estradiol-progesterone-based [Treat(C)] and 5-day Co-Synch plus progesterone [Treat(Co-Sy)] protocols on ovulation time, pre-ovulatory follicle diameter, corpus luteum (CL) size and blood flow, progesterone (P4) concentration and pregnancy rate (PR) in beef heifers. In Experiment 1, a crossover design was applied (n = 9). For Treat(C), a progesterone intravaginal (PI) device was inserted, plus 2 mg of estradiol benzoate (day 0). On day 7, 500 µg of cloprostenol plus 0.5 mg of estradiol cypionate were administered, and PI was removed. For Treat(Co-Sy), on day 0, a PI was inserted plus 100 µg gonadotropin-releasing hormone (GnRH). On day 5, PI was removed, plus 500 µg of cloprostenol and 100 µg of GnRH were administered at 69-70 h later. From day one to ovulation day, dominant follicle was evaluated by ultrasonography. On days 4 and 8 post-ovulation, CL was evaluated by color Doppler, and P4 concentration was determined by chemiluminescence. In Experiment 2, a split-plot experimental design was used. Protocols followed were the same as in Experiment 1 [Treat(C); n = 310 and Treat(Co-Sy); n = 314]. Heifers were fixed-time artificially inseminated. Pregnancy was determined on day 41. In Experiment 1, the interval between PI removal and ovulation time was different between protocols (P < 0.01). In addition, P4 concentration was related to the CL size (P < 0.001), CL blood flow (P < 0.01) and protocols (P < 0.03). In Experiment 2, PR did not differ between protocols.
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Affiliation(s)
- Pablo Sebastián Reineri
- National Institute of Agricultural Technology (INTA), EEA Santiago del Estero, La Abrita, Santiago del Estero G4206XBK, Argentina; Faculty of Agronomy and Agribusiness (FAyA), National University of Santiago del Estero (UNSE), Santiago del Estero G4206XCP, Argentina.
| | - Sergio Daniel Roldán Bernhard
- National Institute of Agricultural Technology (INTA), EEA Santiago del Estero, La Abrita, Santiago del Estero G4206XBK, Argentina
| | | | - Gustavo Daniel Gerlero
- National Institute of Agricultural Technology (INTA), EEA Santiago del Estero, La Abrita, Santiago del Estero G4206XBK, Argentina
| | - Juan Florencio Aller
- National Institute of Agricultural Technology (INTA), EEA Balcarce, 7620 Balcarce, Buenos Aires, Argentina
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Sanz A, Gobikrushanth M, Colazo MG. Type of CIDR but not eCG administration affected pregnancy per AI in Holstein heifers subjected to a 5-day estrus synchronization protocol. JOURNAL OF APPLIED ANIMAL RESEARCH 2022. [DOI: 10.1080/09712119.2022.2106989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Affiliation(s)
- Albina Sanz
- Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA) - IA2 (CITA-Universidad de Zaragoza), Zaragoza, Spain
| | - Mohanathas Gobikrushanth
- Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Marcos G. Colazo
- Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton, Canada
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Tschopp JC, Macagno AJ, Mapletoft RJ, Menchaca A, Bó GA. Effect of the addition of GnRH and a second prostaglandin F2α treatment on pregnancy per artificial insemination in lactating dairy cows submitted to an estradiol/progesterone-based timed-AI protocol. Theriogenology 2022; 188:63-70. [DOI: 10.1016/j.theriogenology.2022.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 10/18/2022]
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Zi XD, Xiong Y, Wu JB, Gige MT, Zhao SB, Yu ZH, Lu Y, Qiao YS. Dynamic changes in gene expression during follicle development and the efficacy of four timed AI protocols in non-suckling female yaks ( Bos grunniens). Anim Biotechnol 2022:1-7. [PMID: 35133936 DOI: 10.1080/10495398.2022.2030346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
The objectives of the study were to investigate changes in the mRNA expression levels of five genes during antral follicle development and to assess the efficacy of four timed-artificial insemination (TAI) protocols in female yaks (Bos grunniens). RT-qPCR analysis revealed that expression levels were greater for follicle-stimulating hormone receptor and bone morphogenic protein 15 in the small follicle, luteinizing hormone receptor, and kit ligand in the large follicle, and growth differentiation factor 9 in the medium follicle (p < 0.05). Non-suckling yaks were treated as a 7-d CIDR, and PGF2α + eCG at CIDR withdrawal and TAI with frozen yak semen at 56-58 h after PGF2α (PPe-7d); either a 7-d CIDR (PPG-7d) or a 5-d CIDR (PPG-5d), and PGF2α at CIDR withdrawal and TAI + GnRH at 70-72 h after PGF2α; and GnRH treatment on Day 0, followed by PGF2α on Day 7 and TAI + GnRH on Day 9 (GPG-7d). The results showed that the pregnancy rate (P/AI) was greater in PPG-5d than in GPG-7d (p < 0.05), but the P/AI was not different among the other TAI protocols. In conclusion, the expression levels of these genes in follicles are dynamically changed during antral follicle development in yaks. The PPG-5d protocol achieved a greater P/AI.
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Affiliation(s)
- Xiang-Dong Zi
- The Key Laboratory of Animal Science of State Ethnic Affairs Commission, Southwest Minzu University, Chengdu, China
| | - Yan Xiong
- The Key Laboratory of Animal Science of State Ethnic Affairs Commission, Southwest Minzu University, Chengdu, China
| | - Jin-Bo Wu
- Institute of Animal Science and Veterinary Medicine of Aba Prefecture, Sichuan, China
| | - Mo-Ti Gige
- The Key Laboratory of Animal Science of State Ethnic Affairs Commission, Southwest Minzu University, Chengdu, China
| | - Shou-Bao Zhao
- Datong Yak Breeding Farm of Qinghai Province, Xining, China
| | - Zhong-Hua Yu
- Institute of Animal Science and Veterinary Medicine of Aba Prefecture, Sichuan, China
| | - Yong Lu
- Institute of Animal Science and Veterinary Medicine of Aba Prefecture, Sichuan, China
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Comparison of two intravaginal progesterone-releasing devices in shortened-timed artificial insemination protocols in beef cattle. Theriogenology 2021; 168:75-82. [PMID: 33862427 DOI: 10.1016/j.theriogenology.2021.03.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 02/23/2021] [Accepted: 03/27/2021] [Indexed: 11/23/2022]
Abstract
Commercially available intravaginal progesterone (P4) devices differ in shape, surface area and P4 load, which may affect the resulting pregnancy per AI (P/AI) following timed-AI (TAI). The objective of this study was to compare two intravaginal P4 devices on estrus rate, follicular dynamics and P/AI in beef cattle subjected to shortened-TAI protocols. In Expt. 1, nulliparous heifers were randomly assigned to a P4-releasing intravaginal device (PRID-Delta, 1.55 g P4) or a controlled internal drug release (CIDR, 1.38 g P4) at the initiation of a J-synch protocol. Heifers that displayed estrus 72 h following device removal were TAI, or if not in estrus given GnRH at 72 h and TAI at 90 h. In Expt. 2, nulliparous heifers and non-suckling cows were randomly assigned to either PRID or CIDR groups and either 1 or 2 mg of estradiol benzoate (EB) at initiation of a J-synch protocol. All cattle were TAI concurrent with GnRH 72 h after device removal. In Expt. 3, nulliparous heifers and suckling cows were randomly assigned to either PRID or CIDR groups and initiated a 5-d Cosynch protocol, with TAI concurrent with GnRH 72 h following device removal. In each experiment, cattle received estrus detection patches at device removal, which were then scored from 0 to 3 based on color change between initial application and TAI; 0 = unchanged, 1 = ≤50% change, 2 = >50% change, 3 = missing. Estrus was defined to have occurred when the patch was scored 2 or 3. Transrectal ultrasonography was used to determine cyclicity, diagnose pregnancy in all experiments, and the size of the ovulatory follicle in Expt. 3. In Expt. 1, the estrus rate was greater (72.0% vs. 61.0%; P = 0.04) in the PRID compared to the CIDR group. In Expt. 2, a parity by EB dose interaction (P = 0.02) was attributed to an increased estrus rate (52.8% vs. 41.4%; P = 0.05) in heifers given 1 vs. 2 mg EB. In Expt. 3, there was no difference in the ovulatory follicle diameter at device removal (P = 0.22) or TAI (P = 0.28) between P4 groups. Treatment with a PRID tended (P = 0.10) to increase the P/AI in cows compared to a CIDR (73.5% vs. 61.0%). In all experiments combined, the overall P/AI tended to increase (55.2% vs. 51.0%; P = 0.08) and P/AI in cattle exhibiting estrus increased (64.4% vs. 59.7%; P = 0.02) in cattle given a PRID compared to those given a CIDR, respectively. In summary, the type of intravaginal P4 device affected estrus response and P/AI following TAI in beef cows.
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The effect of altering the timing of GnRH administration and artificial insemination in a modified 5-d CO-Synch protocol using sex-sorted semen in dairy heifers. Theriogenology 2020; 159:53-59. [PMID: 33113444 DOI: 10.1016/j.theriogenology.2020.10.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/23/2020] [Accepted: 10/10/2020] [Indexed: 11/21/2022]
Abstract
The objective was to optimize fertility in a modified 5-d CO-Synch protocol by altering the timing of GnRH administration and AI. Holstein heifers (14-16 mo) received a controlled internal drug releasing device (CIDR) on d 0 and on d 5, CIDR were removed, prostaglandin F2α was administered and estrus detection patches were applied. Estrus was detected at 36, 48, 56 and 72 h after CIDR removal. In Experiment 1, control heifers (n = 195) received GnRH concurrent with timed-AI (TAI) 72 h after CIDR removal, regardless of expression of estrus. Treatment heifers expressing estrus at 36 or 48 h were AI at 56 h (n = 101) and the remaining heifers were randomly assigned to one of two groups: GnRH administration at 56 h and TAI at 72 h (GnRH56, n = 147) or GnRH administered concurrently with TAI at 72 h (GnRH72, n = 148). In Experiment 2, heifers expressing estrus at 36 or 48 h following CIDR removal were AI at 56 h (n = 118) and the remaining heifers were either TAI at 72 h (TAI72, n = 102) or 80 h (TAI80, n = 102), with only heifers not displaying estrus by TAI given GnRH concurrent with AI. All heifers were inseminated with sex-sorted semen and pregnancy diagnosis was performed at 28 d following TAI. In Experiment 1, estrus rate (P = 0.81) and pregnancy per AI (P/AI; P = 0.34) did not differ among control, GnRH56 and GnRH72 groups, so GnRH56 and GnRH72 groups were combined into one split-TAI (STAI) group. The P/AI was greater in heifers displaying estrus by 48 h compared to those not displaying estrus and receiving GnRH in both groups (69.5 vs. 31.3%; P < 0.01) and there was a tendency for P/AI to increase in STAI heifers displaying estrus compared to control heifers displaying estrus (73.3 vs. 62.1%; P = 0.10). In Experiment 2, the estrus rate was increased in TAI80 compared to TAI72 heifers (81.4 vs. 62.7%, P < 0.01); however, there was no difference in P/AI (P = 0.74). Heifers displaying estrus in the TAI72 group had a greater P/AI than heifers not displaying estrus in either group (P < 0.01) and tended to have a greater P/AI than heifers in estrus in the TAI80 group (87.5 vs. 69.9%, P = 0.07). Across both experiments, P/AI was increased in heifers that displayed estrus before AI compared with heifers that did not and performing a STAI tended to increase P/AI in heifers that displayed estrus before AI. Other attempts made to optimize P/AI in the modified 5-d CO-Synch protocol by altering the timing of GnRH administration and/or AI were unsuccessful.
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Effect of estrus expression or treatment with GnRH on pregnancies per embryo transfer and pregnancy losses in beef recipients synchronized with estradiol/progesterone-based protocols. Theriogenology 2020; 157:378-387. [PMID: 32866844 DOI: 10.1016/j.theriogenology.2020.08.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/18/2020] [Accepted: 08/20/2020] [Indexed: 11/23/2022]
Abstract
Two experiments were designed to determine the effect of expression of estrus or GnRH treatment on pregnancies per embryo transfer (P/ET) and pregnancy losses in beef recipients that were synchronized with estradiol/progesterone based protocols for fixed-time embryo transfer (FTET). Experiment 1 evaluated the effect of expression of estrus and GnRH treatment in the absence of estrus on P/ET. Beef cows (n = 729) were treated with 2 mg estradiol benzoate (EB) and an intravaginal device containing 0.5 g of progesterone. Devices were removed 8 d later and all cows received prostaglandin F2α (PGF2α), 400 IU eCG, and 0.5 mg estradiol cypionate (ECP) at that time. Expression of estrus was determined at 48 and 56 h after device removal using tail-paint and cows that did not show positive signs of estrus by 48 h received GnRH or no treatment at random. The overall estrus rate was 76.0% (554/729); 68.0% had positive signs of estrus by 48 h after progesterone device removal and 28.0% of those not in estrus by 48 h showed estrus by 56 h. The proportion of recipients receiving in vivo-derived (IVD) or in vitro-produced (IVP) embryos and P/ET were greater in recipients that showed estrus by 48 and 56 h (94.0% and 48.4%, respectively) than in those that did not show estrus 41.0% and 29.0%, respectively; P < 0.01). However, GnRH treatment of recipients not showing estrus by 48 h did not improve P/ET. Experiment 2 evaluated the effect of expression of estrus on P/ET and pregnancy loses up to parturition in recipients synchronized with two estradiol-based protocols. Beef cows (n = 403) were divided at random to receive the same synchronization protocol as in Experiment 1 (ECP) or a J-Synch protocol (device removal on day 6 and without using estradiol cypionate to induce ovulation). In this experiment, pregnancy was determined at 30 and 60 d by ultrasonography, and all pregnant recipients were followed until parturition to determine pregnancy losses during gestation. Although the number of recipients receiving IVP embryos was greater in the ECP group (90.5% vs. 83.5%; P = 0.03), P/ET did not differ (ECP: 37.0% and J-Synch: 39.0%; P = 0.43). Overall, 88.0% (357/407) of the recipients synchronized showed estrus and a greater P/ET (P = 0.05) was found in the recipients that showed estrus (39.0%) vs. those that did not show estrus (26.0%), regardless of treatment group. Pregnancy losses were lower (P = 0.004) and the calving rate was higher (P = 0.01) in recipients that showed estrus (25.0% and 29.3%, respectively) than in those that did not (88.8% and 2.9%, respectively). In summary, expression of estrus was associated with a greater P/ET in recipients treated with two different estradiol/P4-based synchronization protocols. The expression of estrus was associated with a greater proportion of recipients receiving embryos, P/ET and calving rate. Treatment with GnRH did not improve P/ET in the recipients that did not show estrus, questioning the its use in recipients synchronized with estradiol/progesterone based FTET protocols.
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Pérez-Mora A, Segura-Correa JC, Peralta-Torres JA. Factors associated with pregnancy rate in fixed-time embryo transfer in cattle under humid-tropical conditions of México. Anim Reprod 2020; 17:e20200007. [PMID: 32714459 PMCID: PMC7375863 DOI: 10.1590/1984-3143-ar2020-0007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 05/26/2020] [Indexed: 11/22/2022] Open
Abstract
The objective was to determine the effect of some factors on pregnancy rate of fixed-time embryo transfer (FTET), in cows and heifers kept under Mexican tropical conditions. Recipients females (n=405) grazing in pastures were selected according to breed group (Zebu and crosses), parity (nulliparous and multiparous), body condition score (BCS) and the presence of a corpus luteum (CL). The females were synchronized on day 0 using a progesterone vaginal device and 2 mg estradiol benzoate (EB), two groups were established. Group 1 (conventional protocol) were animals in which the progesterone device was removed on day 7. At this time, also received an injection of 50 mg cloprostenol sodium and 1 mg estradiol cypionate. Animals also received 300 IU (heifers) or 360 IU (cows) of eCG. Group 2 (J-Synch protocol) were animals in which the progesterone device was removed on day 6. Cloprotenol and eCG injections were applied as in Group 1. Additionally, on day 9, animals of group 2 received 0.01 mg buserelin acetate. Embryo transfer of in vivo or in vitro was done on day 16 and pregnancy diagnosis was realized by ultrasonography on days 23 and 53 after FTET. Statistical analyses were carried out using Chi-square tests and logistic regression. Pregnancy rate varied between farms (P<0.05). The highest pregnancy rate was for multiparous cows (66%). The recipient utilization rate was better in the J-Synch protocol (85%), and in vivo embryos (75%) had higher pregnancy rate. The diameter of the follicle and the CL had no effect on pregnancy rate (P>0.05). However, the logistic regression determined that the only significant factor on pregnancy rate was the type of embryo. In conclusion, pregnancy rate in FTET females was higher for in vivo embryos than for in vitro embryos in cows evaluated under humid tropical conditions in Mexico.
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Affiliation(s)
| | | | - Jorge Alonso Peralta-Torres
- División Académica de Ciencias Agropecuarias, Universidad Juárez Autónoma de Tabasco, Villahermosa, Tabasco, México
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