Pregnancy Rates To Fixed-time AI Research Articles

Pregnancy rates to fixed-time AI in Bos indicus-influenced beef cows using PGF2α with (Bee Synch I) or without (Bee Synch II) GnRH at the onset of the 5-day CO-Synch + CIDR protocol

Objectives were to 1) characterize fixed-time AI (FTAI) pregnancy rates using the 5-Day CO-Synch + CIDR protocol in mature, suckled Bos indicus-influenced beef cows, 2) compare FTAI pregnancy rates in the latter to a modified version (5-Day Bee Synch + CIDR; Bee Synch I) that included treatment with prostaglandin F2α (PGF2α) at CIDR insertion on Day 0, and 3) test the hypothesis that elimination of both GnRH-1 at the onset of synchronization and the double dose of PGF on Day 5 (Bee Synch II) would not reduce FTAI pregnancy rates compared to Bee Synch I. For Experiment 1-trial 1, Brahman x Hereford (F-1) cows (n = 168) at least 40 d postpartum (PP; r = 40–92 d) at the time of CIDR insertion were administered the 5-Day CO-Synch + CIDR protocol with FTAI at 72 h after CIDR removal. Pregnancy rates to FTAI averaged 34.9 ± 1.9%. In Experiment 1-trial 2, fall- and spring-breeding Brahman x Hereford (F-1) beef cows (n = 269) were stratified by days PP and assigned randomly to receive either the 5-Day CO-Synch + CIDR (n = 136) or Bee Synch I (n = 133) protocol, with FTAI at 66 h after CIDR removal. Pregnancy rate to FTAI was greater (P < 0.05) in Bee Synch I (52.6 ± 0.9%) than in the 5-Day CO-Synch + CIDR procedure (40.4 ± 5.7%). For Experiment 2, 422 mature Braford, Brangus, Nelore x Brahman, and Brahman crossbred cows (Bos indicus proportion unknown) at 4 locations were treated with Bee Synch I, with FTAI at 66 h. Overall FTAI pregnancy rate averaged 51.7 ± 2.1%. Finally, from 2013 through spring 2018, we used a switchback design using fall- and spring-breeding herds to compare Bee Synch I (402 observations) to Bee Synch II (393 observations). Overall frequency of detected estrus at 66 h using ESTROTECT™ breeding indicator patches was 57.2 ± 2.4%, conception rates of those detected in estrus was 64.4 ± 3.5%, and FTAI pregnancy rates averaged 52.3 ± 2.4%, none of which differed between treatments. Moreover, pregnancy rates to FTAI in both treatments did not differ in cows synchronized between 40 and 80 d PP but increased after 80 d PP (P < 0.05). Bee Synch II, which eliminates GnRH-1 and the double dose of PGF2α on Day 5, results in FTAI pregnancy rates essentially identical to Bee Synch I but reduces synchronization costs and avoids the need for off-label (double dose PGF2α) drug use.

1055 WS Comparisons of two short duration estrous synchronization protocols on pregnancy rates to fixed-time AI

1055 WS Comparisons of two short duration estrous synchronization protocols on pregnancy rates to fixed-time AI

Comparison of melengestrol acetate and controlled internal drug-release long-term progestin-based synchronization protocols on fixed-time artificial-insemination pregnancy rate in beef heifers

ABSTRACT Nulliparous, predominately Angus beef heifers at a commercial ranch in the Nebraska Sandhills were randomly assigned to 1 of 2 progestin-based time AI protocols to compare pregnancy rates. Heifers assigned to melengestrol acetate (MGA; n = 688) received MGA (0.5 mg/d per heifer) from d 0 to 13 and were administered PGF 2α (25 mg, i.m.) on d 32; fixed-time AI (FTAI) occurred approximately 72 h after PGF 2α . Heifers assigned to 14-d controlled internal drug-release (14-d CIDR; n = 697) received a CIDR insert (1.38 g of progesterone) from d 2 to 16, followed by administration of PGF 2α on d 32; FTAI occurred approximately 66 h after PGF 2α . All heifers received GnRH (100 μg, i.m.) at FTAI on d 35. Heifers were estrus detected twice daily, d 15 to 25 following FTAI, and received AI 12 to 18 h after observed estrus. Pregnancy was determined by transrectal ultrasonography 45 d after FTAI, 50 d following second AI, and 36 d following bull removal. Heifers had similar (P = 0.49) FTAI pregnancy rates between MGA and 14-d CIDR (62 vs. 61 ± 2%, respectively). A similar (P = 0.83) proportion of MGA and 14-d CIDR heifers displayed a second estrus (26 vs. 26 ± 2%, respectively); however, heifers previously synchronized with MGA tended (P = 0.06) to have a greater second AI pregnancy rate (66 vs. 56 ± 2%, respectively). Overall pregnancy rate was similar (P = 0.27) between MGA and 14-d CIDR treatments (93 vs. 90 ± 1%, respectively). The MGA system was the more cost-effective synchronization protocol in this study.

Effect of gonadotropin-releasing hormone in long-term controlled internal drug-release protocols on pregnancy rates in beef heifers artificially inseminated after observed estrus or fixed time

<h2>ABSTRACT</h2> Beef heifers at 4 ranches were assigned to 1 of 2 estrus synchronization protocols: CIDR Select heifers received a controlled internal drug-release device (CIDR) on d 0, which was removed on d 14, gonadotropin-releasing hormone (GnRH) on d 23, and prostaglandin (PG) F_2α on d 30; and CIDR-PG heifers received CIDR on d 0, which was removed on d 14, and PG on d 30. At 3 ranches (n = 264, Exp. 1), heifers were observed for estrus and AI 12h after exhibition of estrus (EAI) or were fixed-time AI (TAI) with GnRH at 72h. Heifers at the fourth ranch (n = 320, Exp. 2) were fitted with estrus-detection patches at PG administration, which were scored 72h later at TAI. In Exp. 1, the percentage of heifers observed in estrus, the interval to observed estrus, variance for the interval to estrus, and the distribution of observed estrus did not differ (P > 0.52) between treatments. Pregnancy rate to EAI did not differ (P = 0.18) between treatments (71% for CIDR Select and 59% for CIDR-PG). There was a treatment × ranch interaction (P = 0.01) for TAI pregnancy rate. Pregnancy rate to EAI was greater (P = 0.003) than pregnancy rate to TAI (64 vs. 45%). In Exp. 2, estrus-detection patches on heifers synchronized with CIDR Select tended (P = 0.08) to have less wear than patches on heifers synchronized with CIDR-PG. Fixed-time AI pregnancy rate in Exp. 2 did not differ (P > 0.67) between treatments, averaging 50%. Timed-AI pregnancy rate was greater (P = 0.05) for heifers with estrus-detection patches that were 50 or 100% color change than for heifers with patches that had no color change. Inclusion of GnRH in long-term CIDR protocols did not improve synchrony of estrus or AI pregnancy rates.

Effect of 2, 4, and 5-hour intervals between 2 prostaglandin F2α injections administered with 5-day CO-Synch + CIDR protocol on pregnancy rate in beef cows

<h2>ABSTRACT</h2> The objective of this study was to compare fixed-time AI (TAI) pregnancy rates resulting from intervals of 2, 4, or 6 h between 2 prostaglandin (PG) F_2αinjections administered in a 5-d CO-Synch + controlled internal drug-release device (CIDR) estrus synchronization protocol. Angus and Angus-crossbred cows (n = 901) maintained on native pasture at 3 locations were randomly assigned to treatments after blocking for BCS and postpartum interval. All cows received gonadotropin-releasing hormone and a CIDR insert on d –5, PG and CIDR removal on d 0, and gonadotropin-releasing hormone with TAI at 72 h. Cows also received a second injection of PG either2, 4, or 6 h after the first injection of PG. Pregnancy rates were determined by transrectal ultrasonography 40 ± 2 d following TAI. Body condition score and postpartum interval did not differ (P > 0.72) between estrus synchronization protocols, averaging 4.3 and 81 d, respectively. Fixed-time AI pregnancy rate was least (P ≤ 0.05) in cows receiving 2 PG injections separated by 2- and 4-h intervals (average 51%) compared with cows receiving 2 PG injections separated by a 6-h interval (59.7%). Reducing the interval between PG injections from 6 to 2 h resulted in a 9-percentage-point (15%) reduction in TAI pregnancy rates for cows synchronized with a 5-d COSynch + CIDR protocol.

Fixed-time AI pregnancy rate following insemination with frozen-thawed or fresh-extended semen in progesterone supplemented CO-Synch protocol in beef cows

The objective of this study was to compare fixed-time AI pregnancy rate in Angus crossbred beef cows inseminated with frozen-thawed or fresh-extended semen. Two ejaculates from each of two Angus bulls were collected by artificial vagina and pooled for each bull. The pooled semen from each bull was divided into two aliquots; Aliquot 1 was extended using Caprogen ® (LIC, Hamilton, New Zealand) to a concentration of 3 × 10 6 sperm/straw and Aliquot 2 was extended using egg-yolk–glycerol extender to a concentration of 20 × 10 6 sperm/straw. Semen extended with Caprogen ® was maintained at ambient temperature and semen extended with egg-yolk–glycerol extender was frozen and maintained at −196 °C until insemination. In each of two breeding seasons (Fall 2007 and Spring 2008), Angus-crossbeef cows ( N = 1455) at 12 locations were randomly assigned within location to semen type [Fresh ( N = 736) vs. Frozen ( N = 719)] and sire [1 ( N = 731) vs. 2 ( N = 724)]. All cows were synchronized with 100 μg of GnRH im and a progesterone Controlled Internal Drug Release insert (CIDR) on Day 0, and on Day 7, 25 mg of PGF2 α im and CIDR removal. All cows received 100 μg of GnRH im and were inseminated at a fixed-time on Day 10, 66 h after CIDR removal. Timed-AI pregnancy rates were influenced by season ( P < 0.05), cows detected in estrus prior to and at AI ( P < 0.001), and dam age ( P < 0.01). Pregnancy rates were not affected by semen type (Fresh = 51.5% vs. Frozen = 50.4%; P = 0.66) and there were no significant interactions of semen type by estrus expression, semen type by sire, or semen type by season ( P > 0.1). In conclusion, commercial beef cows inseminated with fresh-extended semen (3 × 10 6 sperm/straw) yielded comparable pregnancy rates to conventional frozen-thawed semen in a progesterone supplemented, CO-Synch fixed-time AI synchronization protocol and may provide an alternate to frozen semen for more efficient utilization of superior genetics.

Comparison of Pregnancy Rate in Angus-cross Beef Cows following Insemination with Frozen Thawed or Fresh Extended Semen

Currently cattle producers in the United States are increasing their farm size for economic profit and using synchronization programs for a fixed time AI for better reproductive management. This requires insemination of large number of cows on a single day. With this trend, there is an opportunity to investigate the possibility of maintaining or improving the reproductive outcomes using fresh extended semen with low sperm numbers instead of frozen semen with high sperm numbers per insemination. The objective of this study was to compare fixed time AI pregnancy rate in Angus cross beef cows inseminated with frozen thawed or fresh extended semen.

Comparison of progestin-based estrus synchronization protocols before fixed-time artificial insemination on pregnancy rate in beef heifers1

The objective of the experiment was to compare pregnancy rates resulting from fixed-time AI after administration of either 1 of 2 controlled internal drug release (CIDR)-based protocols. Heifers at 3 locations (location 1, n = 78; location 2, n = 61; and location 3, n = 78) were assigned to 1 of 2 treatments within reproductive tract scores (1 = immature to 5 = cycling) by age and BW. Heifers assigned to CIDR Select received a CIDR insert (1.38 g of progesterone) from d 0 to 14 followed by GnRH (100 mug, i.m.) 9 d after CIDR removal (d 23) and PGF2alpha (PG, 25 mg, i.m.) 7 d after GnRH treatment (d 30). Heifers assigned to CO-Synch + CIDR were administered GnRH and received a CIDR insert on d 23 and PG and CIDR removal on d 30. Heifers at location 1 were fitted with a HeatWatch estrus detection system transmitter from the time of PG until 24 d after fixed-time AI to allow for continuous estrus detection. Artificial insemination was performed at predetermined fixed times for heifers in both treatments at 72 or 54 h after PG for the CIDR Select and CO-Synch + CIDR groups, respectively. All heifers were administered GnRH at the time of AI. Blood samples were collected 10 d before and immediately before treatment initiation (d 0) to determine pretreatment estrous cyclicity (progesterone > or = 0.5 ng/mL). At location 1, the estrous response during the synchronized period was greater (P = 0.06; 87 vs. 69%, respectively), and the variance for interval to estrus after PG was reduced among CIDR Select- (P < 0.01) compared with CO-Synch + CIDR-treated heifers. Fixed-time AI pregnancy rates were significantly greater (P = 0.02) after the CIDR Select protocol (62%) compared with the CO-Synch + CIDR protocol (47%). In summary, the CIDR Select protocol resulted in a greater and more synchronous estrous response and significantly greater fixed-time AI pregnancy rates compared with the CO-Synch + CIDR protocol.

Effect of timing of prostaglandin administration, controlled internal drug release removal and gonadotropin releasing hormone administration on pregnancy rate in fixed-time AI protocols in crossbred Angus cows

Two experiments were conducted to investigate the effects of timing of prostaglandin F2 α (PGF2 α) administration, controlled internal drug release device (CIDR) removal and second gonodotropin releasing hormone (GnRH) administration on the pregnancy outcome in CIDR-based synchronization protocols. In Experiment 1, suckled Angus crossbred beef cows ( n = 580) were given 100 μg of GnRH + a CIDR on Day 0. Cows in Group 1 (modified Ovsynch-P) received 25 mg of dinoprost (PGF2 α) and CIDR device removal on Day 8 (AM), 100 μg of GnRH 36 h later on Day 9 (p.m.), and fixed-time AI (FTAI) 16 h later on Day 10 (47.5 ± 1.1 h after PGF2 α). Cows in Group 2 (Ovsynch-P) received 25 mg of PGF2 α and CIDR device removal on Day 7 (p.m.), 100 μg of GnRH 48 h later on Day 9 and FTAI 16 h later on Day 10 (66.6 ± 1.2 h after PGF2 α). Pregnancy rates were 56.5% (170/301) for Group 1 and 55.6% (155/279) for Group 2, respectively ( P = 0.47). In Experiment 2, beef cows ( n = 734) were synchronized with 100 μg of GnRH + CIDR on Day 0, 25 mg of PGF2 α and CIDR device removal on Day 7 and either 100 μg of GnRH 48 h later on Day 9 (Ovsynch-P) and FTAI 16 h later on Day 10 (64.9 ± 3.3 h from PGF2 α) or 100 μg of GnRH on Day 10 (CO-Synch-P) at the time of AI (63.2 ± 4.2 h from PGF2 α). Pregnancy rates were 48.8% (180/369) for Ovsynch-P and 44.7% (163/365) for CO-synch-P groups, respectively ( P = 0.11). In both experiments, there was a location × treatment interaction ( P < 0.05); pregnancy rates between locations were different ( P < 0.05) in the Ovsynch-P group. In conclusion, in a CIDR-based Ovsynch synchronization protocol, delaying administration of prostaglandin and CIDR removal by 12 h, or timing of the second GnRH by 16 h, did not affect pregnancy rates to FTAI. Therefore, there may be an opportunity to make changes in synchronization protocols with out adversely affecting FTAI pregnancy rates.