Luteogenesis and Embryo Implantation Are Enhanced by Exogenous hCG in Goats Subjected to an Out-of-Season Fixed-Time Artificial Insemination Protocol

The aim of this study was to evaluate the possible effect of two doses of hCG (100 and 300 IU) applied at two different times (7 and 14 d) after a fixed-time artificial insemination protocol (FTAI) upon some variables involved in the embryonic implantation rate in goats during the natural deep anestrous season (April, 25° north). The experimental units considered crossbred, multiparous, anovulatory goats (n = 69, Alpine, Saanen, Nubian x Criollo), with average body weight (43.6 ± 5.7 kg) and body condition score (1.86 ± 0.28 units) located in northern–semiarid Mexico (25° N, 103° W). Once the goat’s anestrus status was confirmed, goats were subjected to an estrus induction protocol. Upon estrus induction confirmation, goats (n = 61) were subjected to a FTAI procedure. Immediately after the FTAI, the goats were randomly distributed to five experimental groups: (1). G100-7 (n = 13) 100 IU, hCG 7 d post-FTAI, (2). G100-14 (n = 12) 100 IU hCG, 14 d post-FTAI, (3). G300-7 (n = 12) 300 IU, hCG, 7 d post-FTAI, (4). G300-14 (n = 12) 300 IU hCG 14 d post-FTAI, and (5). Control group, CONT (n = 12) 0.5 mL saline, 7 and 14 d post-FTAI. The response variables conception rate (39.36 ± 0.23), fertility rate (27.96%), prolificacy rate (1.1 ± 0.29 kids), ovulation rate (0.74 ± 0.20 corpus luteum) corpus luteum diameter (10.15 ± 0.59 mm), embryo number (1.58 ± 0.20), and embryo implantation rate (48.96%), did not differ between treatments. However, while the variables fecundity rate (67%), embryo efficiency index-1 (33.99 ± 0.20%), and embryo efficiency index-2 (27.94 ± 0.30%) were favored by the G300-14 treatment, the corpus luteum area was favored (p < 0.05) by both G300-7 (113.30 ± 0.19 mm2) and G300-14 (103.04 ± 0.17 mm2). Such reproductive strategy emerges as an interesting approach, not only to enhance the out-of-season reproductive outcomes, but also to boost one of the main rulers defining the global reproductive efficiency of a heard, namely, the embryo implantation efficiency.

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Factors which interfere in the results of the Fixed-Time Artificial Insemination in beef cattle

Revista Agraria Academica ◽

10.32406/v4n4/2021/5-14/agrariacad ◽

2021 ◽

Vol 4 (4) ◽

pp. 5-14

Author(s):

Alex Adriano Cavalcante Ferreira ◽

◽

Avelino Velloso Ferreira Murta ◽

Artur Azevedo Menezes ◽

Tiago Oliveira Brandão ◽

...

Keyword(s):

Beef Cattle ◽

Corpus Luteum ◽

Body Condition ◽

Artificial Insemination ◽

Body Condition Score ◽

Fixed Time ◽

The Body ◽

Fertility Rates ◽

Condition Score ◽

Animal Category

The objective of this study was to evaluate the effect of the animal category, the cyclicity, the CIDR reuse, the body condition score (BCS), the inseminator and the bull on the fertility rates of bovine submitted to a FTAI protocol. It was observed that pluriparous demonstrated a higher fertility. The group With Corpus Luteum obtained a higher conception rate. The CIDR of 4th use reduced (P <0.05) the chance of conception. The chances of conception in cows of the Low BCS group were lower (P <0.05), than the cows with intermediate and high BCS. The inseminator and the bull exerted influence on the fertility. Therefore, all factors are important in FTAI programs.

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Morphologic aspects of the genital tract from Nellore cows undergoing gynecological screening to insertion in the fixed-time artificial insemination (TAI) program

Journal of Morphological Sciences ◽

10.4322/jms.068114 ◽

2014 ◽

Vol 31 (02) ◽

pp. 118-122

Author(s):

R. Mello ◽

M. Mello ◽

M. Abidu-Figueiredo ◽

P. Scherer ◽

H. Palhano

Keyword(s):

Artificial Insemination ◽

Genital Tract ◽

Body Condition Score ◽

Fixed Time ◽

The Body ◽

Morphological Aspects ◽

Functional Aspects ◽

Condition Score ◽

The Right ◽

Rectal Palpation

Abstract Introduction: This study aimed to evaluate the morphology of the genital tract from 98 Nellore cows by rectal palpation and combine them with the functional aspects for inclusion in a fixed-time artificial insemination (TAI) program. Methods: Were evaluated the ovaries, cervix and vulva, as well as the body condition score (BCS scale 1-5). Results: In relation to the ovaries, there were palpable structures found in 51 (17 CL and 34 FL) in the rights ovarian and 37 palpable structures (06 CL and 31 FL) in the left ovary. Asymmetry was found in 17.3% and uterine cervicitis in 20.4% of examined females. Changes were noted in vulva in 51.0% (40 to 10 papules and hyperemia) and the average of BCS was 3.15. On the basis of morphological aspects founded, 29 females with an average of BCS 2.7 and 01 with metritis were excluded and 07 (BCS-3, 5) inseminated immediately after the exam, with 61 included in the TAI program. These data support the conclusion that of all ovulations occurred, characterized by the presence of CL, most occurred in the right ovary (73.9%). The prevalence rate (51%) of vulvar aspects found, indicate a need for research of reproductive diseases in their flock. Conclusion: The BCS may impacts on the cyclicity and in the pregnancy rate of females included in the program.

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172 Effect of period of insertion of a progesterone-releasing device and pro-oestrus length on follicular and luteal characteristics and pregnancy rates to fixed-time AI in Bos indicus heifers

Reproduction Fertility and Development ◽

10.1071/rdv32n2ab172 ◽

2020 ◽

Vol 32 (2) ◽

pp. 213

Author(s):

G. A. Bo ◽

A. Cedeño ◽

R. Maingón ◽

J. P. Cedeño ◽

H. Gamboa ◽

...

Keyword(s):

Corpus Luteum ◽

Binary Data ◽

Body Condition Score ◽

Bos Indicus ◽

Fixed Time ◽

Pregnancy Rates ◽

Conventional Group ◽

Preovulatory Follicle ◽

Device Removal ◽

Condition Score

An experiment was designed to evaluate the effect of the length of insertion of a progesterone (P4)-releasing device and the length of pro-oestrus on follicular and luteal characteristics and pregnancy rates to AI (P/AI) in Bos indicus heifers treated with oestradiol/P4-based treatments. Bos indicus beef heifers (n=374), 22-26 months of age, with a corpus luteum (CL) or at least one follicle ≥8mm in diameter and with a body condition score between 2.5 and 3.5 (1-to-5 scale) were synchronised using three treatments for fixed-time AI (FTAI). On Day 0, all heifers received 2mg of oestradiol benzoate (Sincrodiol, Ourofino) and an intravaginal device with 1g of P4 (Sincrogest, Ourofino). The P4 device was removed on Day 6 in heifers in the J-Synch 6 group (n=120) and on Day 7 in heifers in the J-Synch 7 group (n=105) and conventional group (n=165). All heifers received 500μg of cloprostenol (Sincrocio, Ourofino) and 300IU of equine chorionic gonadotrophin (SincroeCG 6000UI, Ourofino) at the time of P4 device removal. Furthermore, heifers in the conventional treatment group received 0.5mg of oestradiol cypionate (SincroCP, Ourofino) at the same time. In addition, all heifers were tail-painted for oestrus detection (CeloTest, Biotay). Heifers that had lost ≥50% of the tail paint by 70-74h (J-Synch groups) or 48-52h (conventional group) after device removal were FTAI at that time. Heifers not showing oestrus by 70-74h (J-Synch groups) or 48-52h (conventional group) received 10μg of gonadotrophin-releasing hormone (Sincroforte, Ourofino) at the same time and were FTAI 8h later. All heifers were also examined using ultrasonography (Mindray DP50 Vet) every 12h from the time of device removal to determine the time of ovulation, 6 days after ovulation to determine the diameter of the CL, and 28 days after FTAI for P/AI determination. Data were analysed using the MLGM procedure (InfoStat) for normal data families (follicular dynamics) and binary data family (P/AI). The results are shown in Table 1. The diameter of the dominant preovulatory follicle and the CL did not differ among groups (P>0.12). However, the interval from device removal to ovulation was longer in heifers in the J-Synch groups than in heifers in the conventional group (P<0.05). Furthermore, P/AI was not different among groups. In conclusion, although the J-Synch protocols delayed the interval from P4 device removal to ovulation, the three protocols evaluated in the present study were equally effective in Bos indicus heifers. Table 1.Mean (±s.e.m.) diameter of the preovulatory follicle (P/Foll) and corpus luteum (CL), interval from progesterone (P4) device removal to ovulation, and pregnancy rates to AI (P/AI) in Bos indicus heifers Treatment P/Foll, mm Interval to ovulation, h CL diameter, mm P/AI,% (n) J-Synch 6 10.5±0.7 101.4±2.3a 18.6±1.0 52.0 (62/120) J-Synch 7 10.6±0.7 96.0±2.2a 16.5±0.9 39.0 (41/105) Conventional 9.4±0.7 73.0±1.9b 16.8±0.9 45.0 (74/165) a,bDifferent superscripts denote differences between groups in the interval from P4 device removal to ovulation.

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Fertility in Gyr Cows (Bos indicus) with Fixed Time Artificial Insemination and Visual Estrus Detection Using a Classification Table

Journal of Veterinary Medicine ◽

10.1155/2014/404363 ◽

2014 ◽

Vol 2014 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Lilido Nelson Ramírez-Iglesia ◽

Rafael María Roman Bravo ◽

Adelina Díaz de Ramirez ◽

Leandro J. Torres

Keyword(s):

Milk Yield ◽

Artificial Insemination ◽

Body Condition Score ◽

Bos Indicus ◽

Fixed Time ◽

Visual Observation ◽

Chi Square ◽

Condition Score ◽

Daily Milk Yield ◽

Daily Milk

The aim of this research was to compare two artificial insemination protocols (AIP): hormonal synchronization with fixed time artificial insemination (SC-FTAI) and the use of a table based on visual observation of estrus signs (VO) in order to identify cows in natural or spontaneous estrus being assigned to AI (NSE-IA). Two groups were formed: in the first group 109 cows were assigned to SC-FTAI, in which a commercial protocol is used; the second one included 108 randomly chosen cows, which were assigned to NSE-AI and in this group a modified table was used. Response variable was first service fertility rate (FSF), which was coded 1 for pregnant and 0 for empty. Predictor variables were AIP, postpartum anestrus, daily milk yield, body condition score at AI and calving number. Statistical analyses included association chi-square tests and logistic regression. Results showed an overall 41.94% FSF and a significant association was detected (P<0.05) between FSF and daily milk yield; pregnancy rates were 42.20% and 41.67% for the SC-FTAI and NSE-IA groups, respectively (P>0.05). The odds ratio for the effect of AIP was only 1.050, suggesting no differences in FSF between groups. The NSE-AI protocol can enhance both the technique of VO and reproductive efficiency. Further validation of the table is required.

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The use of insulin to improve fertility of timed-inseminated postpartum suckled beef cows

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2010001000023 ◽

2010 ◽

Vol 45 (10) ◽

pp. 1219-1221 ◽

Cited By ~ 2

Author(s):

Augusto Schneider ◽

Luiz Francisco Machado Pfeifer ◽

Eduardo Schmitt ◽

Ivan Bianchi ◽

Marcelo Brandi Vieira ◽

...

Keyword(s):

Pregnancy Rate ◽

Body Condition ◽

Chorionic Gonadotropin ◽

Artificial Insemination ◽

Body Condition Score ◽

Insulin Injection ◽

Fixed Time ◽

Beef Cows ◽

Condition Score ◽

Equine Chorionic Gonadotropin

The objective of this work was to evaluate the effect of insulin alone or in association with equine chorionic gonadotropin (eCG) on the fertility of postpartum beef cows subjected to synchronization. A total of 340 cows was subjected to fixed time artificial insemination. In the trial 1, the cows were subjected to temporary weaning (TW), while in the trial 2 the same protocol was tested without TW. The addition of an insulin injection to a progesterone/eCG-based protocol without TW increased the pregnancy rate of beef cows with body condition score (BCS) equal to or lower than 2.5. Insulin had no effect on cows submitted to TW or with BCS equal to or higher than 3.0.

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Effects of Injecting GnRH 48 Hours after PGF2α on the Dynamic Follicular and Luteal Endocrine Cells in Post - Pubertal Holstein Heifers

Open Access Journal of Veterinary Science & Research ◽

10.23880/oajvsr-16000186 ◽

2019 ◽

Vol 4 (3) ◽

pp. 1-5

Author(s):

Cuadra EJ

Keyword(s):

Corpus Luteum ◽

Endocrine Cells ◽

Cell Function ◽

Body Condition Score ◽

Significant Decline ◽

Luteal Cell ◽

Control Group ◽

Plasma Samples ◽

Blood Samples ◽

Condition Score

Eighteen cycling Holstein heifers were allotted at random by weight and body condition score to one of two treatments to evaluate the effects of GnRH on luteal response when injected 48 hours (h) after the first injection in a 10 day interval between two i njections of PGF2α . Heifers in the control group (n=9) received an injection of saline 48 h after the first injection of PGF2α; however, heifers in the μg) 48treatmenthafter group n=9) received an injection of GnRH (100 the first injection of PGF2α. Heife rs were checked for estrus 3 times daily for 60 minutes each time. Blood samples were collected for analysis of progesterone on d ays 0 (first injection of PGF2α), 2 (48 h after the fi rst injection), 10 ( at the second injection of PGF2) and at day 17 (7 days a fte r the second injection of PGF2α ). Plasma samples were analyzed fo r concentration of progesterone via radioimmunoassay to evaluate luteal cell function. Concentrations of progesterone did not differ between the control heifers and treatment animals at any day of the study. However, heifers treated with GnRH showed a significant decline in concentration of progesterone from day 0 to day 2 in a luteal response to the injection; nevertheless, concentrations of progesterone increased significantly from day 2 t o day 10. Thus, this data demonstrated that injecting GnRH 48 h after PGF2α either speeds up formation of new corpus luteum or prevents full regression of the corpus luteum present prior to the first injection of PGF2α.

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10 EFFECT OF ESTRADIOL BENZOATE OR hCG ON DAY 22 AFTER TIMED ARTIFICIAL INSEMINATION ON THE CORPUS LUTEUM SIZE, PROGESTERONE CONCENTRATION, AND PREGNANCY RATE IN RESYNCHRONIZED BEEF HEIFERS

Reproduction Fertility and Development ◽

10.1071/rdv28n2ab10 ◽

2016 ◽

Vol 28 (2) ◽

pp. 134

Author(s):

J. B. S. Borges ◽

H. L. D. Neri ◽

M. R. Almeida ◽

E. P. Silva ◽

A. Bilha

Keyword(s):

Corpus Luteum ◽

Pregnancy Rate ◽

Body Condition ◽

Body Condition Score ◽

Pregnancy Rates ◽

Control Group ◽

Beef Heifers ◽

Pregnancy Diagnosis ◽

Condition Score ◽

And Control

This study aimed to compare the effects of 2 inducers of new follicular wave [oestradiol benzoate (EB) or hCG] administrated at onset of resynchronization protocols initiated 22 days after the first timed AI (TAI) of beef heifers. We evaluated the effect of treatments on corpus luteum (CL) development, serum progesterone (P4) concentrations, and pregnancy rates. A total of 467 grazing Brangus heifers, with 24- to 26-months, 320 ± 10 kg of body weight, and 3.2 ± 0.5 body condition score, were utilised. The resynchronization protocol began 22 days after the first TAI (Day 22). Heifers were randomly allocated into 1 of 3 groups: EB (n = 199), hCG (n = 101), or control untreated (n = 167). The EB- and hCG-treated heifers received an intravaginal P4 device (Procliclar, 0.75 g of P4; Hertape, Brazil) and an IM treatment with 1 mg of EB (Benzoato HC, Hertape) or 1000 IU of hCG (Vetecor 5000, Hertape), respectively. On Day 30, P4 device was removed, and the pregnancy diagnosis was performed. At this time heifers had the CL area (cm2) determined by ultrasound and seric P4 concentration evaluated by chemiluminescence assay. The assay sensitivity was 0.1 ng mL–1, and the intra- and interassay coefficients of variation were 7.9 and 10.6%, respectively. Nonpregnant heifers after the first TAI (EB = 97, hCG = 36) received intramuscularly 150 μg of sodium cloprostenol (Veteglan Luteolítico, Hertape) and 1 mg of oestradiol cypionate (Cipionato HC, Hertape). The second TAI was performed 48 to 52 h after the P4 device removal. On Day 62, heifers were submitted to a second pregnancy diagnosis. No effect of the body condition score (P = 0.28) was observed on the first and second pregnancy per AI. Pregnancy rates after the first TAI were higher (P = 0.03) on hCG-treated heifers (64.4%) than EB (51.3%) or the control group (58.7%). The EB group determined greater (P = 0.04) pregnancy rate after the second TAI (49.5%) than the hCG group (22.2%). The cumulative pregnancy rates were similar (P = 0.46) between groups [EB (72.4%) and hCG (68.3%)]; however, both were greater (P < 0.05) than the control group (58.6%). Heifers treated with hCG (3.42 ± 0.76) presented greater CL area at Day 30 (P < 0.05) than the EB (2.44 ± 0.57) and control (2.61 ± 0.61) groups. The treatment with hCG 22 days after TAI determined greater (12.43 ± 3.48; P < 0.05) serum P4 concentrations on Day 30 than the EB (6.92 ± 3.04) and control (7.29 ± 2.45) groups. Therefore, the use of hCG at the beginning of resynchronization protocol 22 days after the TAI increased pregnancy rate following the first TAI. However, the use of 1 mg of EB determined greater pregnancy rate after the second TAI, and no detrimental effects on CL development, P4 concentration, and on first TAI pre-established pregnancy.

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9THE USE OF ECG TO INCREASE PREGNANCY RATES IN POSTPARTUM BEEF COWS FOLLOWING TREATMENT WITH PROGESTERONE VAGINAL DEVICES AND ESTRADIOL BENZOATE AND FIXED-TIME AI

Reproduction Fertility and Development ◽

10.1071/rdv16n1ab9 ◽

2004 ◽

Vol 16 (2) ◽

pp. 127 ◽

Cited By ~ 7

Author(s):

G.A Bo ◽

L. Cutaia ◽

P. Chesta ◽

D. Moreno

Keyword(s):

Body Condition Score ◽

Fixed Time ◽

Beef Cows ◽

Estradiol Benzoate ◽

Pregnancy Rates ◽

Control Group ◽

Treatment Groups ◽

Condition Score ◽

N 93 ◽

Rectal Palpation

Treatments with progesterone (P4) releasing devices and estradiol benzoate (EB) have been extensively used in fixed-time AI (FTAI) programs in beef cattle. However, pregnancy rates in postpartum cows kept on pasture often have been lower than expected because of poor body condition score (BCS) and a high incidence of anestrous. A recent study (Cutaia L et al., 2003 Theriogenology 59, 216) suggested that the addition of eCG to a P4/EB FTAI program may improve pregnancy rates in cows with fair to poor BCS, but results were not conclusive. Therefore, this experiment was designed to further investigate the effect of eCG treatment on pregnancy rates in postpartum beef cows in those conditions. The experiment was performed at 2 locations with lactating Angus cows (n=93), 60 to 90d postpartum with a BCS 1.9 (1 to 5 scale; Location 1), and crossbred Zebu cows (n=290), 60 to 90d postpartum with a BCS 2.0 (Location 2). In each Location, cows were randomly allocated to 1 of the following treatment groups: Control, eCG Day6, or eCG Day8. All cows received a P4 intravaginal device (DIB, Syntex, Argentina) and 2mg EB i.m. (Syntex) on Day0, 500mg cloprostenol (Estroplan, Syntex) at the time of DIB removal (Day8), 1mg EB i.m. on Day9 and FTAI 52 to 56h after DIB removal. Cows in the Control group received no further treatment, whereas cows in the eCG-treated groups received 400 IU eCG (Novormon 5000, Syntex) on Day6 or Day8. Cows were examined on Day0 by rectal palpation (Location 1) or by ultrasonography (US; Location 2) and were classified as those with a CL or without a CL, with either large (>8mm) or small (<8mm)small follicles. Pregnancy was determined by US 45d after FTAI. Data were analyzed by logistic regression and the effects of location, treatment, ovarian status, AI technician and semen were considered in the model. There was no effect of location (P=0.3), AI technician (P=0.2) or semen (P=0.8) on pregnancy rates. However, there was an effect of treatment (P=0.02), attributed to higher pregnancy rates in the eCG Groups than in the Control Group (Table). Furthermore, cows with a CL or without a CL but with large follicles on Day 0 had higher pregnancy rates than those with small follicles (P=0.04). It was concluded that the use of eCG in a P4/EB FTAI program improved pregnancy rates in postpartum beef cows that were in fair topoor BCS.

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PSXII-36 Use of FSH or hCG to enhance follicular growth and pregnancy per artificial insemination during a split-AI program in crossbreed beef heifers

Journal of Animal Science ◽

10.1093/jas/skaa278.442 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 243-243

Author(s):

Daniella C Heredia Castaneda ◽

Oscar Alejandro Ojeda-Rojas ◽

Darrel White ◽

Maria C Londono ◽

Sergio D Lasso ◽

...

Keyword(s):

Artificial Insemination ◽

Low Dose ◽

Reproductive Tract ◽

Body Condition Score ◽

Growth Control ◽

Control Group ◽

Preovulatory Follicle ◽

Follicular Growth ◽

Significant Difference ◽

Condition Score

Abstract The objective of the study was to compare follicle growth and pregnancy per artificial insemination (P/AI) in crossbreed heifers receiving either a low dose of hCG (150 IU) or a low dose of FSH (20 mg) vs. a control group during the final stage of a split-AI protocol. A total of 387 heifers were enrolled in the trial and were randomly assigned in three treatments (Control n = 134, FSH n = 125, and hCG n =128) within reproductive tract score (RTS; 1 to 5 scale), body condition score (BCS; 1 to 9 scale) and pubertal status. All groups were synchronized with a 7-day CO-Synch + CIDR protocol, at CIDR removal the two treatments were injected, an Estrotect patch was placed, and the diameter of the dominant follicle was assessed through transrectal ultrasonography, at day 9 heifers that presented estrus (> 50% of the Estrotect patch rubbed off) were AI, and those that did not were TAI at day 10. An ultrasound was carried out along with the AI to measure the diameter of the preovulatory follicle and 30 days after for pregnancy check. The data was analyzed using the GLIMMIX procedure (SAS). The diameter of the preovulatory follicle was different among treatments (Control: 11.48 ± 0.21; FSH: 11.48 ± 0.25; hCG; 10.73 ± 0.28; P = 0.01). However, the rate of follicular growth (Control: 4.96 ± 0.37; FSH: 4.59 ± 0.39; hCG: 5.12 ± 0.38; P = 0.64) and P/AI (control: 41.35%; FSH: 35.77%; and hCG: 34.38%; P = 0.47) were not different among groups. There was a significant difference (P < .0001) in P/AI when comparing animals that presented estrous (48.99%) or not (29.27%). In conclusion, the use of low dosed of hCG or FSH at the time of device removal did not increase the proportion of pregnant heifers.

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171 Follicular and luteal characteristics and pregnancy rates in Bos indicus suckled cows treated with two oestradiol/progesterone-based protocols with a prolonged pro-oestrus

Reproduction Fertility and Development ◽

10.1071/rdv32n2ab171 ◽

2020 ◽

Vol 32 (2) ◽

pp. 212

Author(s):

A. Cedeño ◽

R. Maingón ◽

J. P. Cedeño ◽

C. Guadalupe ◽

L. Morales ◽

...

Keyword(s):

Corpus Luteum ◽

Body Condition Score ◽

Bos Indicus ◽

Fixed Time ◽

Beef Cows ◽

Pregnancy Rates ◽

Conventional Group ◽

Preovulatory Follicle ◽

Device Removal ◽

Condition Score

An experiment was designed to evaluate the effect of the length of insertion of a progesterone (P4)-releasing device on follicular and luteal characteristics and pregnancy rates to fixed-time AI (P/FTAI) in Bos indicus cows treated with oestradiol/P4-based treatments with a prolonged pro-oestrus. Multiparous Bos indicus suckled beef cows (n=659), 60-90 days postpartum, with a corpus luteum (CL) or at least one follicle ≥8mm in diameter and with a body condition score between 2 and 3.5 (1-to-5 scale) were synchronised using three treatments. On Day 0, all cows received 2mg of oestradiol benzoate (Sincrodiol, Ourofino) and an intravaginal device with 1g of P4 (Sincrogest, Ourofino). The P4 device was removed on Day 6 in cows in the J-Synch 6 group (n=195) and on Day 7 in cows in the J-Synch 7 group (n=262) and conventional group (n=202). All cows received 500μg of cloprostenol (Sincrocio, Ourofino) and 400IU of equine chorionic gonadotrophin (SincroeCG 6000UI, Ourofino) at the time of P4 device removal. Cows in the conventional treatment group also received 0.5mg of oestradiol cypionate (SincroCP, Ourofino) at the same time. In addition, all cows were tail-painted for oestrous detection (CeloTest, Biotay). Cows that had lost ≥50% of the tail paint 62-66h (J-Synch groups) or 48-52h (conventional group) after device removal were FTAI at that time. Cows not showing oestrus by 62-66h (J-Synch groups) or 48-52h (conventional group) received 10μg of GnRH (Sincroforte, Ourofino) at the same time and were FTAI 8h later. A subset of 20 cows per group was also examined using ultrasonography (Mindray DP50 Vet) every 12h from the time of device removal to determine the time of ovulation, 6 days after ovulation to determine CL diameter, and 30 days after FTAI to determine P/AI. Data were analysed using the GLM Mixed procedure (InfoStat). The results are shown in Table 1. The diameter of the dominant preovulatory follicle was larger and the interval from device removal to ovulation was longer in cows in the J-Synch groups compared with those in the conventional group (P<0.05). Furthermore, the diameter of the CL was larger and P/FTAI was higher in cows in the J-Synch 7 group compared with those in the J-Synch 6 and conventional groups. In conclusion, delaying the removal of the P4 device by 1 day (i.e. Day 7 vs. Day 6) in the J-Synch groups and prolonging the pro-oestrus period by not giving oestradiol cypionate at P4 device removal (i.e. J-Synch 7 vs. conventional) resulted in a larger preovulatory follicle and CL and higher P/FTAI in Bos indicus suckled cows. Table 1.Mean (±s.e.m.) diameter of the preovulatory follicle (P/Foll) and corpus luteum (CL), interval from progesterone (P4) device removal to ovulation, and pregnancy rates to fixed-time AI (P/FTAI) in Bos indicus suckled cows Treatment P/Foll diameter, mm CL diameter, mm Interval to ovulation, h P/FTAI,% (n) J-Synch 6 15.5±0.3a 18.7±0.8a 83.0±4.0b 41.0 (80/195)a J-Synch 7 16.4±0.2b 21.9±0.8b 86.0±3.0b 52.0 (136/262)b Conventional 13.8±0.2a 16.8±0.9a 64.0±3.0a 37.1 (75/202)a a,bDifferent superscripts denote differences between means or P/FTAI.

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