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

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.

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

2021 ◽  
Vol 33 (2) ◽  
pp. 161
Author(s):  
E. R. Canadas ◽  
B. J. Duran ◽  
G. Machado ◽  
A. Nall ◽  
S. E. Battista ◽  
...  
Keyword(s):  
Artificial Insemination ◽  
Mixed Models ◽  
Generalized Linear Mixed Models ◽  
Fixed Time ◽  
P Value ◽  
Beef Heifers ◽  
Follicle Diameter ◽  
Follicle Size ◽  
Gonadotrophin Releasing Hormone ◽  
Intravaginal Device

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).

9 TIMED ARTIFICIAL INSEMINATION IN BLOCKS: A NEW ALTERNATIVE TO IMPROVE FERTILITY IN BEEF COWS

2015 ◽  
Vol 27 (1) ◽  
pp. 97
Author(s):  
L. F. M. Pfeifer ◽  
N. A. Castro ◽  
L. G. B. Siqueira ◽  
K. R. Lagos ◽  
A. Bagon ◽  
...  
Keyword(s):  
Artificial Insemination ◽  
Meta Analysis ◽  
Bos Indicus ◽  
Prostaglandin F2α ◽  
Beef Cows ◽  
Ovulation Rate ◽  
Control Group ◽  
Block Group ◽  
Preovulatory Follicle ◽  
Timed Artificial Insemination

The objective of this study was to evaluate whether timed artificial insemination (TAI) according to the diameter of the dominant preovulatory follicle (POF) would improve pregnancy rates in beef cows. In Experiment 1, a retrospective meta-analysis of 5 oestradiol- or gonadotropin-releasing hormone-based TAI experiments from 2011 to 2014 was performed to evaluate the interval from luteolysis to ovulation. In these experiments, crossbred cows (Gyr × Holstein; n = 60) were examined by ultrasonography at 12-h intervals from progesterone-releasing device (CIDR) removal to ovulation. A linear regression model was used to predict the effect of POF diameter on the time of ovulation. Cows with a larger POF at the time of AI ovulated earlier than cows with smaller POF (y = –8.25x + 115.22; R2 = 0.93; P < 0.0001). In Experiment 2, lactating Nelore cows (Bos indicus; n = 59) on random days of the oestrous cycle were given 2 mg of oestradiol benzoate IM and a CIDR device (Day 0) to synchronize follicular waves. The CIDR were removed, and cows were given 500 μg of d-Cloprostenol (prostaglandin F2α) IM, 1 mg of oestradiol cypionate IM, and 300 IU of eCG IM on Day 8. On the morning of Day 10 (07:00 a.m.), the diameter of the POF was assessed by ultrasonography, and cows were randomised into Control (n = 29) and Block (n = 30) groups. 1) Control-group cows were TAI 48 h after CIDR removal (08:00 a.m. on Day 10), and Block-group cows were inseminated at 4 time points according to the diameter of the POF: B0 (POF ≥15 mm, TAI at 08:00 a.m. on Day 10, n = 6), B1 (POF 13 to 14 mm, TAI at 02:00 p.m. on Day 10, n = 8), B2 (POF 11 to 12 mm, TAI at 08:00 a.m. on Day 11, n = 11), and B3 (POF ≤ 10 mm, TAI at 02:00 p.m. on Day 11, n = 5). Pregnancy status was assessed 30 days post-AI by ultrasonography. No differences were detected in the diameter of the POF 48 h after CIDR removal (P = 0.77) or ovulation rate (P = 0.65; combined ovulation rate 52/59, 88%) between Control and Block groups. Block group had a higher pregnancy rate than Control (22/30, 73% v. 13/29, 45%, respectively; P = 0.02). In conclusion, our results document that interval from luteolysis to ovulation depends on the size of preovulatory follicle, timing of AI in relation to ovulation time is critical, and AI time according to the diameter of the POF can be an effective tool to improve fertility of cows in TAI protocols.

scholarly journals PSXIII-14 The impact of estrus intensity on variables associated with fertility in Bos taurus-influenced beef cows

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 362-363
Author(s):  
Reinaldo F Cooke ◽  
Nicola Oosthuizen ◽  
Kelsey Schubach ◽  
Alice Brandão ◽  
Ramiro Oliveira Filho ◽  
...  
Keyword(s):  
Physical Activity ◽  
Bos Taurus ◽  
Fixed Time ◽  
Beef Cows ◽  
Estrus Synchronization ◽  
Estrus Detection ◽  
Follicle Size ◽  
The Impact ◽  
Ovarian Dynamics ◽  
Synchronization Protocol

Abstract To evaluate the impact of estrus expression and intensity on parameters associated with reproductive performance, 219 lactating, multiparous Bos taurus-influenced beef cows were enrolled in this study. Cows were exposed to an estrus synchronization protocol, where they received a 100-µg injection of GnRH and a CIDR insert on d -10, a 25-mg injection of PGF2a at CIDR removal on d -3, and an injection of GnRH 60–66 h following CIDR removal at fixed-time AI (TAI; d 0). Cows were fitted with a pedometer behind their right shoulder on d -10, and an estrus detection patch was applied to their tail-head on d -3. Estrus expression was defined as removal of &gt; 50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting daily activity during the non-estrus period (d -10 to -3) from activity during the expected estrus period (d -3 to 0). Cows were classified into 3 groups: cows that did not express estrus (NOESTR; n = 119), cows that expressed estrus with net physical activity greater than the median (HIESTR; n = 50), and the remaining cows (LWESTR; n = 50). Ultrasonography was performed on d -3, 0, and 7 to determine the presence and size of ovarian structures. Pregnancy diagnosis was performed 29 d after TAI. Net physical activity was greater in HIESTR compared to both LWESTR and NOESTR (P &lt; 0.01). Dominant follicle size was greater in HIESTR compared to both LWESTR and NOESTR (P &lt; 0.01). Furthermore, HIESTR had greater corpus luteum volume on d 7 than LWESTR and NOESTR (P &lt; 0.01). Pregnancy rates to AI (PR/AI) were greater in HIESTR and LWESTR compared to NOESTR (P &lt; 0.01). In conclusion, cows that expressed estrus at a greater intensity had improved ovarian dynamics. Additionally, cows that exhibited estrus had greater PR/AI compared to non-estrual cows.

scholarly journals Effect of preovulatory follicle size on cumulus cell and follicular wall transcript abundance in beef cows

2017 ◽  
Author(s):  
◽  
Jenna Marie Monnig
Keyword(s):  
Cumulus Cell ◽  
Cumulus Cells ◽  
Beef Cows ◽  
Preovulatory Follicle ◽  
Dominant Follicle ◽  
Oocyte Competence ◽  
Follicle Diameter ◽  
Follicle Size ◽  
Gonadotropin Surge ◽  
Cell Transcriptome

Gonadotropin releasing hormone (GnRH)-induced ovulation of small dominant follicles decreased pregnancy rates and increased late embryonic/fetal mortality in postpartum beef cows, which could be caused by inadequate oocyte competence and(or) maternal environment. Previous studies revealed that dominant follicle size at GnRHinduced ovulation in beef cows may affect oocyte competence, as higher fertilization rates and higher embryo quality were achieved as dominant follicle diameter at insemination increased. In addition, higher pregnancy rates and increased concentrations of circulating preovulatory estradiol and postovulatory progesterone were observed in recipient cows induced to ovulate large compared to small dominant follicles, which may affect the establishment of pregnancy. The objectives of the current study were to determine the effects of preovulatory follicle size and physiological status on the cumulus cell transcriptome (Experiment 1) and determine the effects of preovulatory follicle size and steroidogenic capacity (i.e. concentrations of circulating estradiol) on the dominant follicle wall transcriptome collected before the preovulatory gonadotropin surge (Experiment 2). In Experiment 1, ovulation was synchronized in suckled beef cows by administering an injection of GnRH on d-9, prostaglandin F2a (PG) on d-2, and a second injection of GnRH on d0. The dominant follicle was trans-vaginally aspirated on d1 and cumulus-oocyte complexes (COC) were collected. The cumulus cells were removed from the oocytes and assigned to one of the following follicle classifications based on follicle diameter and estrus expression: small (n=6; less than 11.7mm; no estrus expression), large (n=6; greater than 12.5 mm; no estrus expression), or spontaneous (n=5; 11.6-13.9 mm; estrus expression and endogenous gonadotropin surge). RNA was extracted from cumulus cells collected from pools of four oocytes and sequenced before being aligned to the Bos taurus genome (UMD3.1). When comparing the cumulus cell transcriptome of small versus large preovulatory follicles, 430 transcripts were more abundant at a false discovery rate (FDR) less than 0.10 in small follicles and 454 were more abundant in large follicles. The glycolytic pathway was enriched in the cumulus cells of large follicles compared to small follicles. In the small versus spontaneous preovulatory follicle comparison, 597 transcripts were more abundant in small follicles and 1012 transcripts were more abundant in spontaneous follicles. The steroid biosynthesis pathway (i.e. cholesterol synthesis) was enriched in the cumulus cells of spontaneous compared to small follicles. In the large versus spontaneous preovulatory follicle comparison, 541 transcripts were more abundant in cumulus cells from large follicles and 951 were more abundant in cumulus cells from spontaneous follicles. In summary, a greater abundance of transcripts encoding for members of the glycolytic pathway in large follicles and transcripts encoding for members of the steroid biosynthesis pathway in the cumulus cells of spontaneous compared to small follicles indicate that oocytes from small follicles may be less competent. Preovulatory follicle development was synchronized in Experiment 2 by administering GnRH on d-9 and PG on d-2 to non-lactating beef cows. The ovaries were harvested at slaughter 48 hr after PG (d0) and the dominant follicle collected. RNA was extracted from approximately half of the follicle wall and sequenced. Cows were divided into two classifications based on dominant follicle diameter at collection: small (n=4; less than 11.5 mm) and large (n=7; greater than 12.5 mm). Nine transcripts were more abundant in small follicles, and two transcripts were more abundant in large follicles. No significant pathways were found. The same 11 follicle walls were also divided into two classifications based on concentration of serum estradiol at 48 hr after PG: low (n=6; less than 4.0 pg/ml) and high (n=5; greater than or equal to 4.0 pg/ml). In the low estradiol classification, 281 transcripts were more abundant in the follicle wall and 40 were more abundant in the follicle wall of the high estradiol classification. No significant pathways were found. Transcripts were analyzed with PANTHER to find significant gene ontology (GO) terms. Differentially abundant transcripts in low estradiol follicles were more highly associated with mitosis, chromosome segregation, and regulation of biological processes. In summary, a small number of transcripts were differentially abundant in the follicle wall of small versus large dominant follicles prior to the preovulatory gonadotropin surge and no specific pathways were identified that might provide insight into how the physiological maturity of a dominant follicle can affect pregnancy rate. Comparisons made between follicle walls from follicles with low or high serum estradiol found a larger number of transcripts were more highly abundant in the low estradiol follicles, possibly indicating that a higher level of transcription is taking place in the low estradiol follicles, and therefore are less mature.

scholarly journals 150 Administration of prostaglandin F2α 24 h prior to CIDR removal impacts reproductive performance of suckled beef cows assigned to the 7-d CO-Synch + CIDR protocol

2019 ◽  
Vol 97 (Supplement_1) ◽  
pp. 48-49
Author(s):  
Pedro Fontes ◽  
Reinaldo F Cooke ◽  
Nicola Oosthuizen ◽  
Claire L Timlin ◽  
Nicholas Dias ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
Artificial Insemination ◽  
Prostaglandin F2α ◽  
Beef Cows ◽  
Similar Proportion ◽  
Dominant Follicle ◽  
Blood Samples ◽  
Follicle Diameter ◽  
Estrus Detection ◽  
Coating Removal

Abstract Angus-influenced cows received 100 µg of GnRH and a CIDR device containing 1.38 g of progesterone (P4) on d 0, and were randomly assigned to 25-mg injection of PGF2α on d 6 (PG6; n = 147) or d 7 (PG7; n = 162). The CIDR device was removed on d 7, and cows received 100 µg of GnRH and artificial insemination (AI) on d 10. An estrus detection patch was attached to the tailhed of each cow on d 7, and estrus expression assessed at AI (> 50% coating removal). Blood samples were collected on d 0 to determine the presence of a functional corpus luteum via plasma P4 (CL, P4 ≥ 1.0 ng/mL; NOCL P4< 1.0 ng/ mL). A subset of cows (70 cows/treatment) were assigned to ultrasonography at AI to verify dominant follicle diameter (DFD). Blood samples for plasma P4 analysis were collected (42 cows/treatment) on d 6, and on d 7 at CIDR removal and 1 h later. A similar proportion of PG6 and PG7 cows were classified as CL (P = 0.38). Plasma P4 at CIDR removal and 1 h later were less in PG6 vs. PG7 cows classified as CL (1.81 vs. 3.99 and 1.06 vs. 2.89 ng/mL), and did not differ (P ≥ 0.43) within NOCL. Estrus expression was greater in PG6 vs. PG7 cows classified as CL (72.8 vs. 48.3%), but similar (P = 0.96) within NOCL. Pregnancy rates did not differ between treatments (P = 0.53), despite a numerical difference (P = 0.15) between PG6 vs. PG7 cows classified as CL (65.5 vs. 55.0%). No other treatment effects were detected (P ≥ 0.20). Hence, PGF2α administration 24 h prior to CIDR removal appears to benefit reproductive performance of beef cows with a functional CL at the beginning of the 7-d CO-Synch + CIDR protocol

scholarly journals 299 Treatment with prostaglandin F2α and an intravaginal progesterone insert in advance of gonadotropin-releasing hormone enhances response to estrus synchronization in mature beef cows

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 138-139
Author(s):  
Rachael C Bonacker ◽  
Katy S Stoecklein ◽  
Jaclyn N Ketchum ◽  
Emma R Knickmeyer ◽  
James William C Locke ◽  
...  
Keyword(s):  
Ovarian Follicle ◽  
Prostaglandin F2α ◽  
Beef Cows ◽  
Gonadotropin Releasing Hormone ◽  
Control Treatment ◽  
Estrus Synchronization ◽  
Releasing Hormone ◽  
Representative Subset ◽  
Estrus Detection ◽  
Follicle Size

Abstract An experiment was designed to evaluate the effect of treatments in advance of gonadotropin-releasing hormone (GnRH; 100μg gonadorelin) administered at the start of estrus synchronization. We hypothesized that administration of prostaglandin F2α (PG; 500μg cloprostenol) followed by treatment with an intravaginal progesterone-releasing insert (CIDR; 1.38g progesterone) would result in increased follicle size at GnRH, thereby enhancing response to GnRH and overall response to estrus synchronization. Postpartum suckled beef cows (n = 183) in two locations were assigned to one of five treatments based on age, days postpartum, and body condition score. Treatments (Figure 1) were designed as a two-by-two factorial with a control (Treatment 1). Treatments 2–5 received a CIDR insert from Day -17 to Day -10, with (Treatments 2 and 3) or without (Treatments 4 and 5) administration of PG coincident with CIDR insertion on Day -17. Coincident with GnRH administration on Day -10, CIDR inserts were either removed (Treatments 2 and 4) or remained in place until Day -3 (Treatments 3 and 5). On Day -3, estrus detection aids were applied and a representative subset of cows in each treatment were fitted with estrus detection transmitters. Blood samples were collected on Days -27, -17, -10, -3, and 0 for determination of serum estradiol and/or progesterone concentrations via radioimmunoassay. For a representative subset of cows (n = 111), transrectal ovarian ultrasound was performed to assess ovarian follicle size and presence of corpora lutea on Days -17, -10, -3, and 0. Treatment with PG and CIDR in advance of GnRH resulted in improvements (P &lt; 0.05) in several response variables, including follicle size on Day -17 and estrous response prior to AI. Results support the hypothesis that administration of PG and treatment with a CIDR for 7 d prior to GnRH improves likelihood of GnRH response and enhances response of mature cows to estrus synchronization.

scholarly journals The Effect of A PRID®Delta-Based Estrus Synchronization Protocol On Pregnancy Rates In Cows With No Estrus Symptoms

2022 ◽  
Author(s):  
Murat Can Demir ◽  
Cihan Kaçar ◽  
Umut Çağın Arı ◽  
Semra Kaya ◽  
Oğuz Merhan ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Prostaglandin F2α ◽  
Pregnancy Rates ◽  
Dominant Follicle ◽  
Serum Progesterone ◽  
Blood Samples ◽  
Follicle Diameter ◽  
Follicle Size ◽  
Equine Chorionic Gonadotropin

Abstract The present study aimed to determine the effects of progesterone-based gonadotropin-releasing hormone (GnRH), prostaglandin F2α (PGF2α), and equine chorionic gonadotropin (eCG) injections on progesterone profiles and pregnancy rates in cows with no estrus symptoms within 60 days after parturition. A total of 80 cows were included in the study. All animals had the progesterone-releasing device PRID®Delta placed intravaginally for nine days with an injection of GnRH. On the eighth day, PGF2α was injected, and PRID®Delta was removed from the vagina on day nine. Artificial insemination was carried out 60 hours after PRID®Delta removal. In half of the animals (n = 40), 600 IU of eCG was injected when PRID®Delta was removed on the ninth day before artificial insemination 60 hours later. Blood samples were taken from the tail vein on days 0 and 8 to determine progesterone levels. The pregnancy rate in the group that received eCG was 37.5%, while it was 27.5% in those that did not (P = 0.4). While the dominant follicle diameter was 15.5 mm in cows injected with eCG during timed artificial insemination, the follicle diameter was 12.4 mm in cows with no eCG injection (P <0.001). There were no differences in serum progesterone values in blood samples taken until the time of artificial insemination. However, progesterone values in the blood taken during artificial insemination were 0.94 ng/ml in the eCG- group and 0.72 ng/ml in the eCG+ group (P <0.05). As a result, it was determined that eCG injections, in addition to progesterone-based GnRH and PGF2α applications, increased the pregnancy rates in cows without symptoms of estrus. The dominant follicle diameter was larger in cows treated with eCG during artificial insemination; however, follicle size did not increase the pregnancy rate.

scholarly journals PSXIII-11 Altering length of the presynchronization period in a long-term progestin-based estrus synchronization protocol for timed artificial insemination of beef heifers

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 375-376
Author(s):  
Emma R Knickmeyer ◽  
Jordan M Thomas ◽  
James William C Locke ◽  
Rachael C Bonacker ◽  
Lauren Ciernia ◽  
...  
Keyword(s):  
Artificial Insemination ◽  
Reproductive Tract ◽  
Prostaglandin F2α ◽  
Estrus Synchronization ◽  
Dominant Follicle ◽  
Estrus Detection ◽  
Timed Artificial Insemination ◽  
Split Time ◽  
Synchronization Protocol

Abstract An experiment was designed to evaluate the effect of extending the presynchronization period in a progestin-based estrus synchronization protocol. Heifers were assigned to an 18 d or 14 d CIDR® treatment (1.38 g progesterone), with prostaglandin F2α (PG; 250 mg im) administered 16 d after CIDR® removal (Day 34). Heifers at two locations (location one, n = 193; location two, n = 649) were assigned to treatment based on reproductive tract score (RTS; Scale 1–5) and weight. Estrus detection aids (Estrotect®) were applied at PG and split-time artificial insemination (STAI) was performed based on estrus expression at 66 h. Heifers that expressed estrus at 66 h were inseminated and heifers that did not express estrus were inseminated at 90 h. Only heifers that failed to express estrus by 90 h received gonadotropin-releasing hormone (GnRH; 100 µg im) at AI. At location one, blood samples were collected at PG and AI (66 h or 90 h) from all heifers to determine E2 concentrations, and transrectal ovarian ultrasound was performed to detail ovarian structures on a subset of heifers (n = 73) at both time points. The proportion of heifers expressing estrus by 66 h (60%) or in total by 90 h (84%) after PG did not differ between treatments. Pregnancy rate to STAI did not differ between treatments (P = 0.3; 52%, 14 d CIDR®-PG; 50%, 18 d CIDR®-PG), or at the end of the 60 d breeding season (P = 0.2). There were no differences between treatments in mean diameter of the dominant follicle at PG (P = 0.6) or STAI (P = 0.3), nor were any differences observed between treatments in E2 concentrations at PG (P = 0.8) or STAI (P = 0.6). These data suggest that CIDR® treatment can be extended from 14 to 18 d, providing flexibility in scheduling without compromising reproductive outcomes.

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