109 Pre-synchronization and reutilization of progesterone devices during a 6-day CO-Synch protocol for fixed-time artificial insemination in beef heifers

Ovulatory response to the initial gonadotrophin-releasing hormone (GnRH) of the CO-Synch protocol is affected by circulating progesterone (P4) and follicle size. In addition, heifers that ovulate to the initial GnRH treatment have greater fertility after AI. Thus, this study determined the effect of (1) presynchronization (Presynch) before a 6-day CO-Synch protocol and (2) circulating [RCE1] (P4) on ovulatory response, oestrus expression, and pregnancies per AI (P/AI) in beef heifers. Yearling beef heifers (n=233) at three locations were randomly assigned in a 2×2 factorial design to the following treatments: (1) Presynch+6-day CO-Synch with a new P4 device; (2) Presynch+6-day CO-Synch with a once-used P4 device; (3) 6-day CO-Synch with a new P4 device; and (4) 6-day CO-Synch with a once-used P4 device. Presynch consisted of insertion of a new P4 intravaginal device (1.38g of P4) on Day −17 and removal of P4 device on Day −11 concurrently with 500µg of cloprostenol sodium (PGF). On Day −9, all heifers received either a new (New) or once-used (Used) CIDR and 100µg of gonadorelin acetate (GnRH). Six days later (Day −3), CIDRs were removed, 1000µg of PGF was administered and an oestrous detection patch applied (Estrotect). At 72h after CIDR removal, AI was performed concurrently with administration of 100µg of GnRH. Pregnancy was determined by transrectal ultrasonography 31 days after AI. A subset of heifers (n=155) was examined on Day −9 and Day −3 by ultrasonography to determine ovulation to Day −9 GnRH. Data were analysed using generalized linear mixed models (SAS 9.4; SAS Institute Inc.). Presynch heifers had larger follicle diameter on Day −9 (12.7±0.3 vs. 10.1±0.3 mm; P<0.001), greater ovulatory response to Day −9 GnRH (82.5%; 66/80 vs. 56%; 42/75; P<0.001), greater expression of oestrus (90.6%; 106/117 vs. 78.4%; 91/116; P<0.02), and earlier oestrus (49.8±1 vs. 53.1±1 h; P<0.01) compared with controls. There was a treatment×CIDR interaction on oestrous expression, such that a lesser (P<0.05) percentage of control heifers with new CIDR expressed oestrus compared with all other groups (Table 1). Heifers with a used CIDR during the 6-day CO-Synch tended (P=0.08) to have greater P/AI (52.1%; 61/117) than those with a new CIDR (40.5%; 47/116). In conclusion, presynchronization before initiation of a 6-day CO-Synch increased follicle diameter, enhanced ovulatory response and oestrous expression, but did not affect fertility. The earlier onset of oestrus in presynchronized heifers suggests that the timing of AI may need to be modified. Table 1. Oestrous expression and pregnancy per AI (P/AI) in beef heifers with or without presynchronization and treated with a new or used CIDR during a 6-day CO-Synch Treatment CIDR Oestrus (%; n/n) Time of oestrus (h) P/AI (%; n/n) Control New 67.8a (40/59) 53.7±1.5a 33.9 (20/59) Used 89.5b (51/57) 52.7±1.6a 50.9 (29/57) Presynch New 94.7b (54/57) 50.9±1.4b 47.4 (27/57) Used 86.7b (52/60) 48.7±1.3b 53.3 (32/60) P-value Treatment 0.03 0.01 0.21 CIDR 0.62 0.19 0.08 Interaction 0.003 0.75 0.38 a,bValues with different superscripts differ (P<0.05).

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115 Presynchronization and reutilization of progesterone devices during a 6-day CO-Synch protocol for fixed-time artificial insemination in beef heifers

Reproduction Fertility and Development ◽

10.1071/rdv33n2ab115 ◽

2021 ◽

Vol 33 (2) ◽

pp. 165

Author(s):

E. R. Canadas ◽

B. Duran ◽

G. Machado ◽

A. Nall ◽

S. E. Battista ◽

...

Keyword(s):

Factorial Design ◽

Artificial Insemination ◽

Fixed Time ◽

P Value ◽

Beef Heifers ◽

Follicle Diameter ◽

Follicle Size ◽

Gonadotrophin Releasing Hormone ◽

Intravaginal Device ◽

Second Use

Ovulatory response to the initial gonadotrophin-releasing hormone (GnRH) of the CO-Synch protocol is affected by circulating progesterone (P4) and follicle size. In addition, heifers that ovulate to initial GnRH treatment have greater fertility after AI. Thus, the aim of this study was to assess the effect of (1) presynchronization (Presynch) before a 6-day CO-Synch protocol and (2) P4 device reuse (new vs. second use) on ovulatory response, oestrous expression, and pregnancy per AI (P/AI) in beef heifers. Yearling beef heifers (n=233) were randomly assigned in a 2×2 factorial design to the following treatments: (1) Treatment (Presynch): (1a) Presynch+6-day CO-Synch with new P4 device; (1b) Presynch+6-days CO-Synch with a once-used P4 device; (2) Control (no Presynch): (2a) 6-day CO-Synch with new P4 device; (2b) 6-day CO-synch with once-used P4 device. Presynch consisted of insertion of a new P4 intravaginal device (CIDR, 1.38g of P4; Zoetis) on Day −17 and removal of the CIDR on Day −11 concurrently with 500µg of cloprostenol sodium. On Day −9, all heifers received either a new or once-used (used) CIDR and 100µg of gonadorelin acetate (GnRH, Parnell Inc.). Six days later (Day −3) CIDRs were removed, 1000µg of PGF was administered, and an oestrous detection patch applied (Estrotect, Rockway Inc.). At 72h after CIDR removal, 100µg of GnRH and AI using 3 different sires was performed. Pregnancy was determined by ultrasonography 31 days after AI. A subset of heifers (n=151) were examined on Day −9 and Day −3 by ultrasonography to assess ovulation to Day −9 GnRH. Data were analysed using GLIMMIX (SAS 9.4; SAS Institute Inc.). Presynch heifers had larger follicle diameter on Day −9 (12.7±0.3 vs. 10.4±0.3 mm; P<0.0001), greater ovulatory response (84.6%; 66/78 vs. 52.05%; 38/73; P<0.0001), greater oestrus expression (90.6%; 106/117 vs. 78.4%; 91/116; P=0.03), and expressed oestrus earlier (49.8±1.0 vs. 53.1±1.1 h; P=0.01) compared with controls. There was an interaction for treatment and CIDR on oestrous expression, whereas a lesser (P=0.003) percentage of control heifers with new CIDR showed oestrus compared with all other groups (Table 1). Heifers treated with a used P4 device tended (P=0.08) to have greater P/AI (52.1%; 61/117) than those with a new CIDR (40.5%; 47/116). In conclusion, presynchronization before initiation of a 6-day CO-Synch increased follicle diameter, ovulatory response, and oestrous expression, but did not affect fertility. The earlier onset of oestrus in Presynch heifers warrants further study on timing of AI. Table 1. Oestrous expression and pregnancy per AI (P/AI) in beef heifers with or without presynchronization and treated with a new or used CIDR Treatment CIDR Oestrus (%; n/n) Time of oestrus (h) P/AI (%; n/n) Control New 67.8a (40/59) 53.7±1.5a 33.9 (20/59) Used 89.5b (51/57) 52.7±1.6a 50.9 (29/57) Presynch New 94.7b (54/57) 50.9±1.4b 47.4 (27/57) Used 86.7b (52/60) 48.7±1.3b 53.3 (32/60) P-value Treatment 0.03 0.01 0.21 CIDR 0.62 0.18 0.08 Interaction 0.003 0.78 0.38 a,bValues with different superscripts differ (P < 0.05).

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Effects of presynchronization and eCG on pregnancy rates to GnRH-based, fixed-time artificial insemination in beef heifers

Canadian Journal of Animal Science ◽

10.4141/cjas09058 ◽

2010 ◽

Vol 90 (1) ◽

pp. 23-34 ◽

Cited By ~ 5

Author(s):

J A Small ◽

M G Colazo ◽

J P Kastelic ◽

N E Erickson ◽

R J Mapletoft

Keyword(s):

Chorionic Gonadotropin ◽

Artificial Insemination ◽

Follicular Development ◽

Fixed Time ◽

Pregnancy Rates ◽

Preovulatory Follicle ◽

Beef Heifers ◽

Plasma Progesterone ◽

Follicle Diameter ◽

Equine Chorionic Gonadotropin

Three experiments were conducted to determine the effects of presynchronization and treatment with equine chorionic gonadotropin (eCG) on corpus luteum (CL) and ovarian follicular development, plasma progesterone concentrations, and pregnancy rates in beef heifers subjected to a gonadotropin releasing hormone (GnRH)-based, fixed-timed AI (TAI) protocol. All heifers were given GnRH on day 0, prostaglandin F2α (PGF) on day 7, and a second GnRH on day 9 concurrent with TAI (54 h after PGF). In exp. 1 (N = 148), presynchronization with PGF (days -22 and -11) decreased the percentage of heifers with non-luteal plasma progesterone concentrations on day 0 (5.4 vs 29.7%) and day 7 (0 vs 11.6%; P < 0.05), but not on day 9 (74.3 vs. 66.2%; P > 0.20), and reduced the number of heifers in estrus and bred before TAI (P < 0.05). Although presynchronization reduced preovulatory follicle diameter (12.9 ± 0.3 vs. 14.9 ± 0.3 mm; mean ± SEM; P < 0.01), it did not affect TAI pregnancy rates (36.5 vs. 29.7%; P > 0.20). In exp. 2, heifers (N = 128) were presynchronized with melengestrol acetate (MGA) (days -27 to -12), and received a controlled internal drug release (CIDR) on day 0; on day 7, half were given 300 IU of eCG at CIDR removal. Treatment with eCG tended to increase preovulatory follicle diameter in heifers that did not ovulate to GnRH on day 0 (P = 0.06), but did not affect the percentage of heifers with non-luteal plasma progesterone concentrations on day 9 (57.8 vs. 57.8%) or TAI pregnancy rates (48.4 vs. 53.1%; P > 0.20). Experiment 3 was a 2 × 2 factorial arrangement of presynchronization (PGF concurrent with a CIDR on day -7) and eCG treatments (on day 7) applied to heifers in three herds (A, N = 150, B, N = 260 and C, N = 40). All heifers had a once-used CIDR from days 0 to 7. Presynchronization increased the percentage of heifers (Herd A) with low-luteal plasma progesterone concentrations on day 0 (70.7 vs. 22.7%) and day 7 (90.7 vs. 53.3%; P < 0.01), but did not affect the percentage of heifers with non-luteal concentrations of progesterone on day 9 (97.3 vs. 93.3%; P > 0.20). Combined for all herds, presynchronization reduced the prevalence of a CL on day 0 (23.5 vs. 73.7%; P < 0.01), and increased the prevalence of follicles ≥ 10 mm on day 7 (96.8 vs. 86.7%; P < 0.01); however, TAI pregnancy rates (195/439 = 44.4%) were not improved by either presynchronization or eCG treatment (P > 0.20).Key words: Presynchronization, equine chorionic gonadotropin, GnRH, fixed-time artificial insemination, progesterone

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118 A comparison of intravaginal progesterone devices for fixed-time artificial insemination in beef cattle

Reproduction Fertility and Development ◽

10.1071/rdv33n2ab118 ◽

2021 ◽

Vol 33 (2) ◽

pp. 167

Author(s):

E. M. Zwiefelhofer ◽

S. X. Yang ◽

M. Asai-Coakwell ◽

M. G. Colazo ◽

J. Hellquist ◽

...

Keyword(s):

Artificial Insemination ◽

Animal Health ◽

Colour Change ◽

Fixed Time ◽

Device Removal ◽

Beef Heifers ◽

Lactating Cows ◽

Pregnancy Status ◽

Gonadotrophin Releasing Hormone ◽

Follicular Dynamics

Intravaginal progesterone (P4) devices used for ovarian synchronization before fixed-time AI (FTAI) differ in drug release, which may influence fertility outcome. A 2×2 study was designed to determine the effects of different intravaginal devices (PRID Delta, 1.55g of P4 vs. CIDR, 1.38g of P4) and parity (heifers vs. cows) on follicular dynamics, expression of oestrus, and pregnancy per AI (P/AI). At random stages of the oestrous cycle, nulliparous beef heifers and lactating cows were given 100µg of gonadorelin (gonadotrophin-releasing hormone, GnRH) intramuscularly (IM) and assigned randomly to either the PRID (n=76 heifers, 76 multiparous, 27 primiparous) or CIDR (n=76 heifers, 73 multiparous, 32 primiparous) group. Devices were removed 5 days later, an oestrus-detection patch was applied just cranial to the tail head, and 500µg of cloprostenol was given IM at the time of device removal and again 24h later. At 72h after device removal, cattle were inseminated and given 100µg of GnRH IM. Transrectal ultrasonography was used to determine the diameter of the largest follicle on the day of device removal and at FTAI, ovulation time, and pregnancy status 30 days after FTAI. A colour change of ≥50% of the oestrus-detection patch at FTAI was taken as expression of oestrus. Data were compared among groups by 2-way ANOVA using MIXED and GLIMMIX procedures. There were no interactions between P4 device and parity for any endpoint. The diameter of the largest follicle (mean±s.e.m.) was not different between PRID and CIDR groups on either the day of device removal (10.6±0.1 vs. 10.9±0.1mm) or the day of FTAI (13.7±0.1 vs. 13.9±0.1mm). The proportion displaying oestrus did not differ between P4 device groups, but was greater in heifers than in cows [121/152 (79.6%) vs. 135/207 (65.2%); P<0.01], and the interval from FTAI to ovulation was shorter in heifers than in cows (27.8±1.2 vs. 32.0±1.1 h; P=0.01). The P/AI was not different between P4 device groups or parity groups (overall 67.0%, 238/355). However, among lactating cows, the P/AI tended to be greater in the PRID vs. CIDR group [75/102 (73.5%) vs. 64/105 (61.0%); P=0.10], and was greater in multiparous vs. primiparous cows [106/148 (71.6%) vs. 33/59 (55.9%); P=0.04]. Among cattle that displayed oestrus, the P/AI tended to be greater in the PRID vs. CIDR group [92/123 (74.8%) vs. 85/131 (64.9%); P=0.09]. Among lactating cows that displayed oestrus, the P/AI was greater in multiparous vs. primiparous cows [74/94 (78.2%) vs. 24/42 (57.1%); P<0.01]. In summary, follicular dynamics and expression of oestrus did not differ between PRID and CIDR groups, but the P/AI tended to be greater in PRID-treated lactating cows and in cattle that displayed oestrus. This research was supported by CEVA Animal Health, Saskatchewan ADF, Agriculture and Agri-Foods Canada, and Rockway Inc.

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163 Treatment with gonadotrophin-releasing hormone at the time of AI in beef heifers that fail to express oestrus after an estradiol-based synchronisation protocol improves pregnancies per AI

Reproduction Fertility and Development ◽

10.1071/rdv32n2ab163 ◽

2020 ◽

Vol 32 (2) ◽

pp. 208

Author(s):

A. Butler ◽

H. Butler ◽

G. Cesaroni ◽

R. Alberio ◽

S. Perez Wallace ◽

...

Keyword(s):

Pregnancy Loss ◽

Fixed Time ◽

P Value ◽

Device Removal ◽

Releasing Hormone ◽

Condition Score ◽

Gonadotrophin Releasing Hormone ◽

To Receive ◽

Angus Heifers ◽

Intravaginal Device

Oestrus expression between progesterone (P4) withdrawal and fixed-time AI (FTAI) has been shown to improve pregnancies per AI (P/AI) by 27% in beef cattle. As a result, cattle that do not express oestrus after P4 withdrawal present a challenge to the efficiency of FTAI. The present study was designed to test the hypothesis that administration of gonadotrophin-releasing hormone (GnRH) at the time of AI in heifers that do not express oestrus can improve fertility. Two-year-old Angus heifers (n=1032) with a condition score of 2.75 to 3.5 at two locations in Argentina were used. On Day 0, heifers received an intravaginal device containing 0.5g of P4 (Cronipres, Biogenesis) and 2mg of oestradiol benzoate intramuscularly (Bioestrogen, Biogenesis). On Day 8, devices were removed and heifers received 150µg of d-cloprostenol intramuscularly (Enzaprost, Biogenesis), 0.5mg of oestradiol cipionate intramuscularly (Croni-Cip, Biogenesis), and an oestrus detection patch (Estrotect, Rockway Inc.). On Day 10, AI was performed in all heifers 50 to 54h after device removal. Heifers were categorised based on oestrus expression, and those that did not express oestrus were randomised to receive 100µg of gonadorelin acetate intramuscularly (Gonasyn, Syntex; n=158) concurrent with AI or remain as untreated controls (n=151). Pregnancy was determined using ultrasonography at Days 38 and 111 after AI. Differences in fertility were evaluated using generalised linear mixed models, and the results are shown in Table 1. Oestrus expression between device removal and FTAI was 70.1% (723/1032). Pregnancies per AI at Days 38 and 111 were different between groups (P<0.01). Heifers that expressed oestrus had greater P/AI than those that did not regardless of treatment (P<0.01). However, in heifers that did not express oestrus, treatment with GnRH at the time of AI resulted in greater P/AI than in control heifers (P=0.004). Similarly, P/AI at Day 111 were greater in heifers that expressed oestrus than in those that did not regardless of treatment (P<0.01). Heifers that did not express oestrus and were treated with GnRH had greater P/AI than those that did not express oestrus and remained as controls (P=0.02). Pregnancy loss between Days 38 and 111 was not different between groups; however, there was a tendency (P=0.06) for greater pregnancy loss in heifers that did not express oestrus and were treated with GnRH compared with heifers that expressed oestrus. In summary, treatment with GnRH at the time of AI is a suitable strategy to improve P/AI in heifers that fail to exhibit oestrus after an oestradiol-based synchronisation protocol. However, this strategy appears to increase pregnancy loss, and thus further research is needed to confirm this observation and the mechanisms underlying it. Table 1.Pregnancies per AI (P/AI) and pregnancy loss (%; no. in parentheses) in Angus heifers based on oestrus expression and treatment with GnRH Group P/AI Day 38 P/AI Day 111 Pregnancy loss Oestrus 68.9 (498/723)A 65.2 (471/723)A 5.4 (27/498) No oestrus control 29.8 (45/151)B 28.5 (43/151)B 4.4 (2/45) No oestrus + GnRH 45.6 (72/158)C 40.5 (64/158)C 11.1 (8/72) P-value <0.001 <0.001 0.15 A-CValues within a column with different superscripts differ significantly (P<0.05).

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PSXII-20 Ovarian dynamics and fertility in beef cows administered a 5-day or 6-day CO-Synch protocol for timed artificial insemination

Journal of Animal Science ◽

10.1093/jas/skab235.759 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 423-423

Author(s):

Alexandria E Crist ◽

Jessica Cristina Lemos Motta ◽

Cameron Hayden ◽

Benjamin Duran ◽

Martin Mussard

Keyword(s):

Mixed Models ◽

Generalized Linear Mixed Models ◽

Prostaglandin F2α ◽

Beef Cows ◽

Preovulatory Follicle ◽

Follicle Diameter ◽

Estrus Detection ◽

Follicle Size ◽

Timed Artificial Insemination ◽

Ovarian Dynamics

Abstract The 5-day CO-Synch is an extensively used TAI protocol; however, it requires multiple administrations of prostaglandin F2α (PGF). The objective of the present study was to evaluate the effect of increasing progesterone (P4) device insertion from 5 to 6 days during a TAI protocol on ovarian dynamics and fertility in beef cows. Suckled beef cows (n = 867) at six locations were randomly assigned to either a 5-day or 6-day CO-Synch. Cows received an intravaginal P4 device (CIDR, Zoetis) and 100 µg of gonadorelin acetate (GnRH, Parnell) on d-9 (6-day) or d-8 (5-day). On d-3 CIDR’s were removed, an estrus detection patch applied (Estrotect, Rockway Inc.) and either one (6-day) or two (5-day) doses of PGF (500 µg of cloprostenol sodium, Estroplan, Parnell) was administered. On d0 (72 h after CIDR removal) all cows received 100 µg of GnRH, estrus expression was evaluated, and AI was performed. Pregnancy was determined by ultrasonography 34 days after TAI. Ovarian dynamics were evaluated in a subset of animals (n = 20) between d-3 and d7 to determine preovulatory follicle size, time of ovulation and corpus luteum (CL) size. Data were analyzed using generalized linear mixed models (SAS 9.4). Cows in the 6-day group tended (P = 0.09) to have a larger maximum follicle diameter (16.2±0.4mm) than cows in the 5-day group (15.0±0.6mm). In addition, CL volume on d7 was greater (P = 0.01) in the 6-day (4302±495mm3) than 5-day (2406±455mm3) group. There were, however, no differences (P = 0.15) in the interval between CIDR removal and ovulation. Cows assigned to the 6-day group had greater (P < 0.05) estrus expression [56.1% (215/385) vs 41.5% (161/388)] and pregnancy rate [54.6% (236/438) vs 47.4% (207/435)] than cows in the 5-day group. In conclusion, extension of the period of P4 device insertion in a prolonged proestrus protocol increases preovulatory follicle size, estrous expression, and fertility to TAI.

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Oestrus synchronisation and fixed time artificial insemination in beef heifers

Animal Production Science ◽

10.1071/an09106 ◽

2010 ◽

Vol 50 (7) ◽

pp. 670

Author(s):

Daniel Cavestany ◽

Daniela Crespi ◽

Alvaro Fernandez

Keyword(s):

Artificial Insemination ◽

Prostaglandin F2α ◽

Fixed Time ◽

Pregnancy Rates ◽

Conception Rate ◽

Control Group ◽

Beef Heifers ◽

Follicular Size ◽

Follicle Size ◽

And Control

To compare two oestrus synchronisation protocols in beef heifers presynchronised with two prostaglandin F2α (PG) treatments, 36 h after the second PG treatment one group (hCG-OB group; n = 112) received 250 IU of hCG and 0.5 mg of oestradiol benzoate (OB) followed by fixed time artificial insemination (FTAI) 30 h later. Additional oestrus detection (OD) and artificial insemination (AI) was done in this group for 3 days after FTAI; heifers rebred during this period were considered open to the FTAI. The Control group (n = 112) received only OD and AI for 6 days after the second PG treatment. Follicular size was measured at the time of AI in a subsample of heifers (59 in the hCG-OB group and 34 in the Control group). Results were evaluated separately either considering heifers pregnant at FTAI or those pregnant at FTAI + 3-day OD + AI. The FTAI conception rate was 45.5 vs 76.5% for the Control group (P < 0.0001) and pregnancy rates were 45.5 and 67.0% (P = 0.0014); FTAI + OD + AI conception rates were 63.4 and 76.2% (P = 0.0404) and pregnancy rates 63.4 and 62.8% (P = 0.5719) (hCG-OB and Control groups, respectively). There was a significant correlation (r = 0.713, P < 0.01) between follicle size at FTAI and pregnancy in the hCG-OB group, but not in the Control group (r = 0.3465, P > 0.1). In conclusion, acceptable synchronised conception rate and pregnancy rate were obtained by using this protocol, and the results were improved by complementing it with OD + AI for 3 days after FTAI.

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Effect of recombinant bovine somatotropin on pregnancy rates of Nellore cows resynchronized with the use of new DIB and third use, and inseminated at fixed-time

JOURNAL OF ADVANCES IN AGRICULTURE ◽

10.24297/jaa.v4i1.4304 ◽

2015 ◽

Vol 4 (1) ◽

pp. 356-362

Author(s):

Josemara Silva Santos ◽

Tania Cavalcante ◽

Francisca Elda Ferreira Dias ◽

Domenica Palomaris Mariano de Souza ◽

Alencariano J.S. Falcão ◽

...

Keyword(s):

Artificial Insemination ◽

Linear Models ◽

Plasma Concentrations ◽

Fixed Time ◽

Estradiol Benzoate ◽

Pregnancy Rates ◽

Recombinant Bovine Somatotropin ◽

Equine Chorionic Gonadotropin ◽

Rectal Palpation ◽

Intravaginal Device

The objective of the experiment was to evaluate the effects of recombinant bovine somatropin (rbST), and the reuse of the progesterone (P4) releasing devices in resynchronization, on the pregnancy rates of Nellore cows submitted to fixed-time artificial insemination. A group of 123 multiparae Nellore cows, was submitted to a resynchronization protocol: on day 0 a Bovine Intravaginal Device (DIB® ) with 1,0g of P4 was implanted, associated with intramuscular administration of 2,0mg of estradiol benzoate (IM); on day 8 DIB was removed; and 1,0mg of estradiol cypionate, 0,15mg of prostaglandin F2? and 300 UI of equine chorionic gonadotropin were administered; on day 10, fixed-time artificial insemination was conducted (FTAI). The cows were randomized into G1 (n=12) – without rbST / with used Bovine Intravaginal Device, G2 (n=50) – without rbST / with new DIB, G3 (n=11) - with rbST / with used DIB and G4 (n=50) – with rbST/ with new DIB. rbST was introduced on the eighth day of the protocol. Sixty days after TAI, pregnancy diagnoses were conducted, via rectal palpation. Blood samples were taken on day 0, 8 and 10 of the protocol, in order to assess P4 plasma concentrations. Pregnancy rates were statistically evaluated through Generalized Linear Models Theory and their significance was tested with Analysis of Deviance. Pregnancy rates were 58%, 40%, 81% and 48% for G1, G2, G3 and G4, respectively, with significant statistical difference for G3. Plasma concentrations of P4 were not statistically different among groups, or collections. In view of the results obtained, we concluded that the administration of rbST in association with P4 DIB, used for the third time, improves pregnancy rates. Estrus resynchronization and re-insemination positively impacted pregnancy rates.

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Effects on Synchronization and Reproductive Efficiency of Delaying the Removal of the Intravaginal Progesterone Device by 24 h in the 5d Co-synch Protocol in Heifers

Animals ◽

10.3390/ani11030849 ◽

2021 ◽

Vol 11 (3) ◽

pp. 849

Author(s):

Aitor Fernandez-Novo ◽

Sergio Santos-Lopez ◽

Jose Luis Pesantez-Pacheco ◽

Natividad Pérez-Villalobos ◽

Ana Heras-Molina ◽

...

Keyword(s):

Animal Welfare ◽

Reproductive Performance ◽

Artificial Insemination ◽

Fixed Time ◽

Reproductive Efficiency ◽

Beef Heifers ◽

Animal Management ◽

Commercial Farms ◽

Beef Herds ◽

Farm Economics

In beef herds, increasing animal welfare, improving reproductive performance and easing animal management are key goals in farm economics. We explored whether delaying the removal of the intravaginal progesterone device by 24 h in heifers synchronized with a 5d Co-synch 72-h protocol could improve reproductive efficiency of fixed-time artificial insemination (FTAI). In experiment 1, we examined the total synchronization rate (TSR) in cycling Holstein heifers. Heifers (13.4 ± 0.69 mo.) were randomly assigned to the standard 5d Co-synch 56-h protocol (5dCo56; n = 10), 5d Co-synch 72-h (5dCo72; n = 17), or the modified 5d Co-synch 72-h protocol, in which removal of the progesterone device was delayed by 24 h (6dCo48; n = 19). In experiment 2, 309 cycling beef heifers on 18 commercial farms were subjected to the 5d Co-synch 72-h or 6-d Co-synch 48-h protocol and conception rate (CR) studied. In experiment 1, the three protocols led no differences on TSRs of 80.0% (5dCo56), 88.2% (5dCo72), and 89.5% (6dCo48). In experiment 2, the CR from the beef heifers, observed during two consecutive reproductive seasons did not differ: 59.7% for 5dCo72 and 62.0% for 6dCo48 (p = 0.907). Therefore, delaying removal by 24 h provides satisfactory results without reducing reproductive efficiency of heifers.

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Response of beef heifers and non-suckling beef cows to different oestrous synchronization protocols

Animal Science ◽

10.1017/s135772980005270x ◽

2002 ◽

Vol 74 (3) ◽

pp. 547-552 ◽

Cited By ~ 3

Author(s):

D. Cavestany ◽

N. Negrin ◽

R. Negrin ◽

J. F. Groth

Keyword(s):

Beef Cattle ◽

Medroxyprogesterone Acetate ◽

Artificial Insemination ◽

Experimental Period ◽

Fixed Time ◽

Beef Cows ◽

Pregnancy Rates ◽

Gnrh Analogue ◽

Beef Heifers

AbstractThe objective was to evaluate different oestrous synchronization schemes in beef cattle under range conditions. In experiment 1, 202 heifers averaging 26 months of age were assigned randomly to three treatments: (a) GnRH-PG. (no. = 44) day 0 (D0): injection of GnRH; D7: injection of PGF2α; D0 to D25 oestrous detection (OD) and artificial insemination (AI); (b) OD-PG. (no. = 45) D0 to D4; OD + AI; D5: injection of PGF2α; D5 to D25 OD + AI; and (c)Ovsynch. (no. = 113) D0: injection of GnRH; D7: injection of PGF2α; D9: injection of GnRH and 16 h later AI at fixed time. In experiment 2, 318 non-suckling cows were assigned randomly to three treatments: (a) GnRH-PG. (no. = 106) D0: injection of GnRH; D7: injection of PGF2α; D0 to D25 OD + AI; (b) GnRH-MAP-PG. (no. = 106) D0: injection of a GnRH analogue and insertion of an intravaginal sponge impregnated with 250 mg of medroxyprogesterone acetate; D7: injection of PGF2α and sponge withdrawal; D0 to D25 OD + AI; (c) controls. (no. = 106) OD and AI. The experimental period lasted 25 days and, with exception of the Ovsynch treatment, oestrous detection was carried out twice a day (a.m./p.m.) and inseminations performed 12 h later. The pregnancy rates assessed by ultrasonography 30 days after AI were: experiment 1: (a) 30·0%; (b) 28·6% and (c) 62·3% (P < 0·05); experiment 2: (a) 60·2%; (b) 57·8% and (c) 45·5% (P < 0·05). It is concluded that in heifers and non-suckling cows, oestrous synchronization treatments result in higher pregnancy rates. In non-suckling cows, the addition of a progestagen did not improve the response.

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