Effects of Pre-Synchronization With Prostaglandin F2α and a Progestin, and Delayed Insemination on Pregnancy Rates With Sexed Semen in Replacement Beef Heifers

To determine the effects of pre-synchronization and delayed fixed-time artificial insemination (TAI) on pregnancy rates (PR/AI) with sexed semen, 1,844 beef heifers were enrolled in a completely randomized design at 12 locations. Within a location, the heifers were randomly assigned to one of the five treatments: (1 and 2), heifers were administered prostaglandin F2α (PGF) on Day -7, gonadotropin-releasing hormone (GnRH), and a controlled internal drug releasing (CIDR) insert on Day 0, PGF at CIDR removal on Day 7, and a second injection of GnRH at TAI 72 h later with either conventional (CTRL72-CNV) or sexed semen (CTRL72-SEX); (3 and 4), treated the same as CTRL72 but received a CIDR insert on Day -7 at PGF administration and TAI at 60 h with either conventional (CIDR60-CNV) or sexed semen (CIDR60-SEX); (5), treated the same as CIDR60 but had TAI delayed to 72 h with sexed semen (CIDR72-SEX). Estrus detection patches were applied to all heifers on Day 7 and were evaluated for activation at TAI. Estrus expression did not differ (p = 0.92) between CIDR60 and CIDR72 heifers, but was greater (p < 0.001) in CIDR60 and CIDR72 heifers compared with CTRL72 heifers. Among treatments, PR/AI differed (p < 0.001) and were greater (p ≤ 0.003) in CTRL72-CNV and CIDR60-CNV heifers than CIDR60-SEX and CIDR72-SEX heifers (51.6 and 48.1 vs. 37.5 and 25.3%, respectively). In addition, PR/AI were greater (p < 0.001) in CTRL72-SEX and CIDR60-SEX heifers when compared with CIDR72-SEX (42.0 and 37.5 vs. 25.3%, respectively) heifers but only tended (p = 0.09) to differ between CTRL72-SEX and CIDR60-CNV heifers. No differences (p = 0.33) were determined between CTRL72-CNV and CIDR60-CNV or between CTRL72-SEX and CIDR60-SEX heifers (p = 0.22). In conclusion, no differences were determined between heifers pre-synchronized with only PGF and those pre-synchronized with PGF and a CIDR insert when inseminated with either conventional or sexed semen. Therefore, the use of a CIDR insert for an additional 7 days was not beneficial to PR/AI when heifers were TAI at 60 h with either conventional or sexed semen. Furthermore, delaying TAI to 72 h with sexed semen after pre-synchronization with both PGF and a CIDR insert had a negative impact on PR/AI.

Timed artificial insemination strategies with or without short-term natural service and pregnancy success in beef heifers

Objective was to compare estrous response, and first service and breeding season pregnancy rates in Angus cross beef heifers that received four progesterone (CIDR, vaginal insert) -based estrous-synchronization treatment regimens for timed artificial insemination (TAI) with or without short-term natural service (NS). Heifers (n = 1744; 4 locations) were assigned a reproductive tract score (RTS: 1 = immature, acyclic to 5 = mature, cyclic), body condition score (BCS: 1 = emaciated to 9 = obese) and temperament score (0 = calm to 1 = excitable). Within location, heifers were assigned to either of four treatment regimens. Heifers in Select-Synch + CIDR (C) + short-term NS (SSC + NS) treatment (n = 438) received 100 μg GnRH im + CIDR on Day -7 and CIDR removal + 25 mg PGF2α (im) + estrus-detection patches in the morning of Day 0 and were subjected to NS (bull to heifer ratio, 1:25) from the morning of Day 2 (48 h from CIDR removal) to evening of Day 8. Heifers in CO-Synch + C (COSC) +TAI + NS treatment (n = 433) received 100 μg GnRH + CIDR on Day -7 and CIDR removal + 25 mg PGF2α im + estrus-detection patches in the morning of Day 0 + 100 μg GnRH im + TAI on Day 2, 60 h from CIDR removal, and were subjected to natural service (bull: heifer, 1:25) from the evening of Day 2 immediately after AI through Day 8. Heifers in COSC + TAI treatment (n = 443) received 100 μg GnRH + CIDR on Day -7 and CIDR removal + 25 mg PGF2α im + estrus-detection patches in the morning of Day 0 + 100 μg GnRH im + TAI on Day 2, 60 h from CIDR removal. Heifers in SSC + split time AI (STAI) treatment (n = 430) received 100 μg GnRH + CIDR on Day -7 and CIDR removal + 25 mg PGF2α im + estrus-detection patches in the morning of Day 0. Heifers determined to be in estrus were inseminated at 64 h after PGF2α (25 mg, im) administration and non-estrous heifers determined to be in estrus 20 h later (at 84 h) were inseminated at that time, whereas remaining non-estrous heifers at 84 h received GnRH (100 μg) and were inseminated concomitantly. In SSC + NS and COSC + TAI + NS treatments, natural service bulls were removed and reintroduced (@ bull: heifer, 1:40) on Day 22 and kept until Day 63. In COSC + TAI and SSC + STAI bulls (bull: heifer, 1:40) were introduced on Day 14 and retained until Day 63. All heifers, irrespective of treatment regimens, were observed for estrus three times a day from Day 2 through Day 8. Pregnancy diagnosis was performed on Day 93, 30 days from end of breeding season. Accounting for temperament (P < 0.0001), BCS (P < 0.0001) and RTS (P < 0.0001), the breeding program influenced the estrous response (P < 0.0001). Heifers in COSC + TAI + NS (86.8%), SSC + STAI (84.9%), and SSC + NS (86.5%) treatments had greater estrous response compared with heifers in COSC + TAI (75.8%) treatment. Accounting for temperament (P < 0.01), BCS (P < 0.05) and RTS (P < 0.01), the treatment regimens influenced first service pregnancy rate (P < 0.05). Heifers in COSC + TAI + NS treatment had greater first service pregnancy rate (60.3%) compared with COSC + TAI (54.2%) (P < 0.05). First service pregnancy rate for heifers in SSC + STAI (59.3%) and SSC + NS (57.3%) treatments did not differ from COSC + TAI + NS and COSC + TAI treatments. Accounting for temperament (P < 0.001), BCS (P < 0.0001) and RTS (P < 0.0001), the treatment regimens influenced breeding season pregnancy rate (P < 0.05). Breeding season pregnancy rate for heifers in COSC + TAI + NS (95.4%) and COSC + STAI (94.5%) treatments were greater than that of heifers in COSC + TAI (90.8%) treatment (P < 0.05), and heifers in SSC + NS (94.1%%) treatment did not differ from heifers in other treatments. In conclusion, progesterone-based CO-Synch timed artificial insemination with short-term natural service treatment regimen resulted in proportionately more pregnancies than without short-term natural service treatment regimen. In addition, 64/84 h split-time AI or natural service following Select-Synch treatment regimen could be implemented as an alternative as these treatment regimens resulted in similar pregnancy rate as progesterone based CO-Synch timed artificial insemination with short-term natural service treatment regimen.

Pre-synchronization of ovulation timing and delayed fixed-time artificial insemination increases pregnancy rates when sex-sorted semen is used for insemination of heifers

This study was conducted to determine effects of pre-synchronization of ovulation timing among heifers and delayed fixed-time artificial insemination (TAI) with sex-sorted semen on proportion of heifers pregnant after TAI (PR/AI). Heifers were assigned to one of eight treatments: 1 and 2), 7-d CO-Synch + CIDR treatment regimen with administration of gonadotropin-releasing hormone and a CIDR insert on Day 0, prostaglandin F_2α (PGF) at CIDR removal on Day 7, and TAI occurring 54 h later with conventionally processed (CTRL54-CNV) or sex-sorted semen (CTRL54-SEX); 3 and 4), same as CTRL54 but TAI delayed to 72 h with conventionally processed (CTRL72-CNV) or sex-sorted semen (CTRL72-SEX); 5 and 6), same as CTRL54 but additional administration of PGF on Day -7 and TAI with conventionally processed (PRE54-CNV) or sex-sorted semen (PRE54-SEX); 7 and 8), same as PRE54 treatments but TAI delayed to 72 h with conventionally processed (PRE72-CNV) or sex-sorted semen (PRE72-SEX). Proportion of heifers pregnant after TAI was greater (P ≤  0.02) with conventionally processed semen compared with sex-sorted semen, yet PR/AI did not differ (P =  0.14) between heifers in PRE72-CNV and PRE72-SEX groups. There were greater PR/AI in the PRE72-SEX (P =  0.03) than CTRL54-SEX group (46.1 % and 36.9 %) and there was no difference (P =  0.31) in PR/AI between CTRL54-CNV and PRE72-SEX groups (50.4 % and 46.1 %). In conclusion, pre-synchronization of ovulation timing among heifers combined with delayed TAI resulted in increased PR/AI with sex-sorted semen compared with the 7-d CO-Synch+CIDR treatment regimen.

Presynchronization with prostaglandin F2α and prolonged exposure to exogenous progesterone impacts estrus expression and fertility in beef heifers

To determine the effects of two presynchronization strategies in conjunction with delayed fixed-time artificial insemination (TAI) on pregnancy rates to TAI (PR/AI), 1700 Angus beef heifers at three locations in South Dakota were enrolled in a completely randomized design with a 2 by 2 factorial arrangement of treatments. Within location, all heifers were randomly assigned to one of four treatments: 1) PG54 (n = 434), heifers were administered prostaglandin F_2α (PGF; 25 mg im) 7 d prior [Day -14] to the initiation of the 7-d CO-Synch + controlled internal drug releasing (CIDR) protocol wherein they received gonadotropin-releasing hormone (GnRH; 100 μg im) and a CIDR insert on Day -7, PGF at CIDR removal on Day 0, and a second injection of GnRH concurrently with TAI 54 ± 2 h later; 2) PG72 (n = 426), heifers were exposed to the same treatment as PG54, however, TAI was performed 72 ± 2 h after CIDR removal; 3) PG-CIDR54 (n = 422), same as PG54 but heifers received a CIDR insert on Day -14 rather than Day -7, in addition to PGF administration; 4) PG-CIDR72 (n = 418), same as PG-CIDR54, however, TAI was performed 72 ± 2 h after CIDR removal. Estrus detection patches were applied to all heifers on Day 0 and were evaluated for activation at TAI. Pregnancy was diagnosed via transrectal ultrasonography between 30 and 47 d after TAI. The percentage of heifers exhibiting estrus between Day 0 and TAI was greater (P < 0.01) in the PG72, PG-CIDR54, and PG-CIDR72 treatments compared to the PG54 treatment (78.11, 86.59, and 91.09 vs. 31.05%, respectively). Furthermore, estrus response was greater (P < 0.01) in PG-CIDR72 heifers when compared to PG72. Pregnancy rates to TAI differed among treatments and were greater (P < 0.05) in the PG72 and PG-CIDR54 treatments when compared to PG-CIDR72 (48.8 and 50.4 vs. 38.4%, respectively), and were greater (P = 0.03) in PG-CIDR54 vs. PG54 (43.1%). Moreover, a tendency (P = 0.10) was determined on PR/AI between PG54 and PG72. In conclusion, presynchronization strategies and prolonged exposure to exogenous progesterone have the potential to alter estrus expression and improve fertility in replacement beef heifers.

Pregnancy loss in beef cattle: A meta-analysis

Pregnancy loss in beef cattle causes both management and economic challenges to a producer. A meta-analysis was conducted to quantify reproductive failures that occur during fertilization, early embryonic development, and late embryonic/early fetal development periods of gestation in beef cattle. The meta-analysis included more than 56,000 diagnostic records in 159 studies from 48 papers with 12 studies included in fertilization and pre- blastocyst loss analysis (FERT; days 1-7 of gestation), 107 in early embryo (EEM; days 7-32), and 40 in late embryo/early fetal period (LEF; days 32-100) analysis. Although fertilization rates are reportedly high in beef cattle, significant developmental failure occurs within the first 7 days of gestation. Approximately 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. By the conclusion of the first month of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant. Overall, LEF between days 32-60 and 100 was 5.8 %. Bos indicus animals had greater (P =  0.001) EEM compared to Bos taurus, but there was no difference (P =  0.39) for the LEF period between subspecies. Primiparous cows had greater EEM (P =  0.002) compared to nulliparous heifers and multiparous cows; and nulliparous heifers had a greater LEF compared to primiparous and multiparous cows (P =  0.048). Collectively, these cumulative findings provide a baseline assessment of pregnancy loss specific to beef cattle.

Ovarian follicular changes and hemodynamics in Egyptian buffaloes under CIDR-PGF2α and Ovsynch-CIDR estrus synchronization treatments

This study aimed at investigating the efficacy of two protocols of estrous synchronization on follicular changes and hemodynamics. Pluriparous Egyptian buffaloes (n = 36) were synchronized either with controlled internal drug release (CIDR)-PGF2α (7-days CIDR insert with PGF2α injected on the 6^th day; n = 18) or Ovsynch-CIDR (Ovsynch protocol concurrent with 7-days CIDR insert; n = 18). Blood sampling and ovarian ultrasound examinations (Grayscale, color and power Doppler modes) were conducted on the Day of CIDR removal, estrus, and luteal phase. Mean follicle diameter (MFD), first (1^st-LF) and second (2^nd-LF) largest follicle diameters, and E2 levels significantly increased in the CIDR-PGF2α group at CIDR withdrawal. Ovsynch-CIDR markedly fortified higher follicle population, MFD, and 1^st-LF diameter at estrus and corpus luteum (CL) volume at the luteal phase in concomitant with increases (P < 0.05) in E2 (at estrus) and P4 (at luteal phase). At CIDR removal, the blue pixels in the dominant follicle (DF) were higher (1.5 times; P = 0.054) in the Ovsynch-CIDR than in the CIDR-PGF2α. At estrus, total blood flow (TBF) and power Doppler pixels (PDP) to DF(s) were noticeably higher (seven and 1.6 times; respectively) in the Ovsynch-CIDR than in CIDR-PGF2α (5906 ± 237 vs. 830 ± 60 pixels, P < 0.01 and 5479 ± 322 vs. 3377 ± 19 pixels, P < 0.05; respectively). At the luteal phase, TBF and PDP to the CL increased in the Ovsynch-CIDR group than in the CIDR-PGF2α group (11060 ± 965 vs. 7963 ± 480 pixels, 1.4 times, P = 0.05 and 18900 ± 1350 vs. 13220 ± 568 pixels, 1.1 times, P = 0.005; respectively). In conclusion, based on the improvement in synchronized follicular activity and hemodynamics, the Ovsynch-CIDR regimen is persuaded in Egyptian buffaloes.

Pregnancy associated glycoproteins (PAGs) and pregnancy loss in high vs sub fertility heifers

Reproductive inefficiency and infertility are major financial burdens to domestic livestock. Variables associated with these reproductive losses during early gestation include contributions from the oocyte, uterus, sperm, embryo and placenta. Bovine pregnancy associated glycoproteins (PAG) are produced by the binucleate cells of the ruminant placenta and can be used to diagnose pregnancy. Increased circulating concentrations of PAG early in gestation have been correlated with pregnancy success and decreased concentrations are predictive of impending embryonic mortality in both beef and dairy cattle. The objectives of the current study were to determine whether: 1) heifer fertility status is associated with circulating concentrations of PAG and pregnancy loss; and 2) PAG concentrations within the same animal are repeatable across multiple pregnancies. We hypothesized maternal PAG concentrations would be increased in high fertility compared to subfertile heifers but not repeatable across subsequent pregnancies in the same heifer. Serial embryo transfer (ET; n = 4 rounds) was used to classify predominately Angus heifers (n = 92) as highly fertile (HF = 30; 100% pregnancy success) or subfertile (SF = 62; average = 33%; range = 25-75% pregnancy success) based on day 28 ultrasound diagnosis. Blood samples were collected at both day 28 and 44 for quantification of circulating PAG concentrations by an in house PAG ELISA with antibodies raised against early secreted PAGs. Pregnancy was terminated at day 44 of gestation and heifers were allowed 30 days recovery before synchronization for the next ET. Only heifers that were diagnosed pregnant by ultrasound were used in this study (HF: n = 30, SF: n = 62). Serum concentrations of PAGs were not different between HF (5.90 ± 0.27 ng/mL) and SF (5.56 ± 0.31 ng/mL; P = 0.16) heifers at day 28 of gestation nor was there a difference at day 44 of gestation (P = 0.32). Subfertile heifers had increased pregnancy loss between days 28 and 44 of gestation. Based on odds ratio analysis, SF heifers had a 2.41 times chance to undergo pregnancy loss between day 28-44 compared to HF heifers (P < 0.05). There was no correlation (P > 0.05) in maternal circulating concentrations of PAG between pregnancies on day 28 or 44 of gestation in samples obtained from HF heifers. In summary, circulating concentrations of PAG are not different between HF and SF heifers; however, HF classified heifers have decreased pregnancy loss between days 28 and 44 of gestation.

Prostaglandin F2α 7 d prior to initiation of the 7-d CO-synch + CIDR protocol failed to enhance estrus response and pregnancy rates in beef heifers

To determine the effects of administration of 25 mg of PGF2α 7 d prior to the initiation of the 7-d CO-Synch + controlled internal drug release (CIDR) fixed-time AI (TAI) protocol, 985 Bos taurus beef heifers were enrolled in a completely randomized design at 9 locations from April to July of 2016. Within location, all heifers were randomly assigned to 1 of 2 treatments: 1) CONTROL (n = 496); 100 µg injection of GnRH and a CIDR insert for 7 d [day 7], administration of 25 mg of PGF2α at CIDR removal [day 0], followed by a second injection of GnRH and TAI 54 ± 2 h later; or 2) PRESYNCH (n = 489); same as CONTROL but heifers received an additional injection of 25 mg of PGF2α 7 d prior [day 14] to CIDR insertion. Estrous detection patches were applied to all heifers on day 14 and were evaluated for estrual activity on day 7. Similarly, estrus alert patches were placed on all heifers on day 0 and evaluated for estrual activity at the time of TAI. Pregnancy was diagnosed via transrectal ultrasonography between 35 and 55 d after TAI. The percentage of heifers exhibiting estrus between days 14 and 7 was greater (P < 0.001) for the PRESYNCH (70.1 ± 2.4%) than the CONTROL (41.1 ± 2.3%) treatment, whereas the percentage of heifers exhibiting estrus between day 0 and TAI was greater (P < 0.001) for the CONTROL (55.6 ± 2.4%) than the PRESYNCH (39.7 ± 2.5%) treatment. Estrus response rates differed (P < 0.001) among locations. Pregnancy rates to TAI differed (P = 0.023) among locations; however, they did not differ (P = 0.739) between CONTROL and PRESYNCH treatments (45.4 ± 2.5 vs. 43.2 ± 2.5%, respectively). Final breeding season pregnancy rates did not differ (P = 0.811) between treatments. Therefore, an injection of PGF2α 7 d prior to initiation of the 7-d CO-Synch + CIDR protocol failed to improve pregnancy rates to TAI in replacement beef heifers.

Site of PGF2α injection does not alter effectiveness of the Select Synch + controlled internal drug release and timed artificial insemination protocol

Beef Quality Assurance programs have contributed to significant improvements in the wholesomeness of beef available for consumption. Injection site blemishes in the round have declined since the promotion of administering intramuscular injections in the neck. Unfortunately, many producers continue to administer estrus synchronization (ES) drugs in the rump. The objective of this study was to compare the effectiveness of injection site of PGF_2α, in ES protocols, on steroid hormone concentrations and pregnancy rates. A Select Synch + 7-day controlled internal drug release ES protocol was conducted with the site of PGF_2α injection alternated between neck and rump in beef cattle (n = 312) at the Ohio State University Agricultural Technical Institute and North Carolina State University. Blood samples (n = 75) were collected at controlled internal drug release insertion and at the time of artificial insemination (AI) to determine if progesterone (P4) and estrogen (E2) concentrations varied due to PGF_2α injection site. All cattle were confirmed pregnant by ultrasonography at approximately 30 and 90 days after insemination in North Carolina and approximately 70 days after insemination in Ohio. Data were analyzed as randomized complete block designs in PROC GLIMMIX with animal as the experimental unit. Differences were declared significant at P < 0.05. Site of PGF_2α injection, in either the neck or rump, did not affect (P > 0.05) overall conception rates in response to AI (58.4% and 55.6%, respectively). Altering PGF_2α injection site did not impact P4, E2 concentrations, or the P4:E2 ratio at AI (P > 0.05). However, cattle inseminated after displaying estrus had greater (P < 0.05) pregnancy rates than timed AI (67.8 vs. 47.5%, respectively). First service conception rates and pregnancy rates were consistent with previous reports. Overall, altering the location of the PGF_2α injection during ES did not change circulating hormone concentrations at AI or pregnancy rates; therefore, cattle producers should follow Beef Quality Assurance guidelines when administering ES protocols.