Effects of one versus two doses of prostaglandin F2alpha on AI pregnancy rates in a 5-day, progesterone-based, CO-Synch protocol in crossbred beef heifers

Influence of early progesterone removal on follicular development, expression of estrus, and pregnancy rates in presynchronized postpartum beef cows

The objective of this study was to evaluate the impact of early progesterone removal on pregnancy rates to fixed-time artificial insemination (FTAI) in presynchronized beef cows. Postpartum beef cows (n = 882) were randomly assigned to 1 of 2 treatments: 1) 7&7 Synch: cows received a controlled internal drug release insert (CIDR) and a 25-mg injection of prostaglandin F2α on day 0, 100 μg of GnRH on day 7, a second injection of prostaglandin F2α (PG2) at CIDR removal on day 14, and a second injection of GnRH at FTAI 60-66 h after PG2 (day 17); 2) 7&6 Synch: cows received the same treatment as 7&7 Synch; however, CIDR removal occurred in conjunction with PG2 on day 13, while FTAI remained at 60-66 h after CIDR removal (day 16). Ovarian ultrasonography was performed to determine follicle diameter at PG2 and FTAI in a subset of cows (n = 40). Cows exposed to the 7&7 Synch tended to have larger follicle diameter at PG2 compared with 7&6 Synch cows (P = 0.09); however, there were no differences in follicle diameter at FTAI. No differences were determined between treatments for the expression of estrus (7&7 Synch: 61.6 ± 5.30; 7&6 Synch: 54.1 ± 5.45; P = 0.31) or pregnancy rates to FTAI (7&7 Synch: 60.8 ± 3.83; 7&6 Synch: 57.0 ± 3.84; P = 0.42). In conclusion, early removal of progesterone did not impact pregnancy rates in presynchronized beef cows.

Research on timed AI in beef cattle: Past, present and future, a 27-year perspective

This review aimed to (1) summarize the results from fixed-timed artificial insemination (TAI) fertility studies performed during the last 27 years; (2) compile and evaluate, as examples from the literature base, the direct comparisons made of specific manipulations to synchronization protocols; (3) evaluate the impact of the TAI programs on the reproductive performance during the breeding season, and (4) provide perspective on the future of TAI programs in beef cattle. A search of the literature published from 1995 to 2021 was conducted to identify experiments in which synchronization of ovulation and TAI in beef cattle was performed. The primary outcome of interest was fertility expressed as pregnancies per TAI. The literature included two search engines, the SIS Web of Science and the US National Library of Medicine Institutes of Health through PubMed. After the initial search and screening, a total of 228 manuscripts were selected containing a total of 272,668 TAI. A dramatic increase in the number of publications and TAIs occurred throughout the years. Most of them were from Brazil and United States, followed by Canada, Argentina, Uruguay, and Australia. Two main types of TAI programs were identified: GnRH-based and E2/P4-based protocols. In terms of GnRH-based programs, two variations were evaluated in the present manuscript. First, we evaluated the effect of the progesterone implant during the protocol. The progesterone implant increased pregnancy/TAI (P/TAI) from 44.3 to 54.3%. Second, the use of a second prostaglandin F2α treatment in 5-d CO-synch program increased the P/TAI from 53.2 to 60.9%. In E2/P4-based programs, use of GnRH at TAI increased P/TAI from 54.7 to 59.2% in cows. However, no increase was detected in heifers. Other research showed that use of TAI can increase the overall proportion of the cows pregnant at end of the breeding season and produce earlier calvings compared with bulls. In conclusion, there have been a large number of excellent research studies that have been performed during the last 27 years on TAI in beef cattle. This technology is being utilized successfully in the beef cattle industry. This success is largely because of the valid research that underlies the application of the technology and the economic value of the technology.

Prohibition of hormones in animal reproduction: what to expect and what to do?

As our understanding of ovarian function in cattle has improved, our ability to control it has also increased. The development of Fixed-Time Artificial Insemination (FTAI) protocols at the end of the 20th century has increased exponentially the number of animals inseminated over the last 20 years. The main reasons for this growth were the possibility of obtaining acceptable pregnancy rates without heat detection and, above all, the induction of cyclicity in suckled cows in postpartum anestrus and prepubertal heifers at the beginning of the breeding season. Most FTAI treatments in South America have been based on the use of progesterone (P4) releasing devices and estradiol to synchronize both follicular wave emergence and ovulation, with pregnancy rates ranging from 40 to 60%. These protocols are implemented on a regular basis, allowing producers access to high-quality genetics, and increasing the overall pregnancy rates during the breeding season. In addition, it provided the professionals involved in these programs with a new source of income and the diversification of their practices into activities other than their usual clinical work. Many of these practices are now apparently at risk from restrictions on the use of estradiol by the European Union (EU) and other countries. However, the development of alternative protocols based on GnRH, with P4 devices and eCG and other new products that are not in the market yet will allow us to adapt to the new times that are coming. Logically, the challenge has already been raised and we must learn to use alternative protocols to try to continue increasing the use of this technology in beef and dairy herds. The objective of the present review is to describe the main aspects of banning estradiol in livestock production, the negative impacts on reproductive efficiency, and to present some alternative FTAI protocols for dairy and beef cattle.

Review: Manipulation of follicle development to improve fertility of cattle in timed-artificial insemination programs

The development of an ovulatory follicle is a fundamental premise for any reproductive management program that aims to optimize fertility in cattle. Controlling follicular development comprises the synchronized emergence of a new follicular wave, selection and growth of the dominant follicle, and synchronized ovulation of a high-quality oocyte. All these follicular events, primarily driven by gonadotropin secretion, occur under a very dynamic hormonal environment. In this sense, controlling follicular development demands essentially a precise manipulation of the hormonal environment to modulate gonadotropin secretion. Furthermore, the effectiveness of hormonal manipulation strategies in the management of follicular development depends on specific particularities of each situation, which can vary widely according to genetic groups (Bos taurus vs Bos indicus), nutritional, metabolic, and reproductive status. In this regard, the constant search for the refined synchrony between the hormonal treatments and reproductive events, considering these distinctions and particularities, have provided valuable information that contributed to the development of efficient reproductive programs. This manuscript discusses the physiological bases behind the development of fine-tuned timed-artificial insemination protocols for beef and dairy cattle that resulted in great improvements in reproductive efficiency of beef and dairy herds.

Estrous response and pregnancy percentages following use of a progesterone-based, split-time estrous synchronization treatment regimens in beef heifers

Mean estrous response rate (%ERR) and pregnancy/AI percentages (%P/AI) were determined after imposing split-time AI (STAI) and fixed time AI (FTAI) following 14-d controlled internal drug release (CIDR)+PGF2α or 5-d Select Synch + CIDR regimens. In Experiment 1, 1152 heifers (five locations) were randomly assigned to 14- or 5-d and to 54 + 74- or 64 + 84-h STAI treatment combinations. Estrous detection patches were affixed at PGF2α administration (19 day after- and on day 5 at- CIDR removal for 14- and 5-d regimens, respectively), assessed at 54- or 64-h and again at 74- or 84-h after PGF2α. Heifers determined to be in estrus at respective times were inseminated and non-estrous heifers at 74- or 84-h were given GnRH and inseminated concomitantly. The %ERR between 54 + 74- and 64 + 84-h STAI combinations differed (73.2 % and 78.8 %, respectively; P < 0.05), but %P/AI did not. In Experiment 2, 2014 heifers (eight locations) were randomly assigned to 14- or 5-d regimens and were inseminated split-time (64+84-h combination, similar to Experiment 1) or at fixed time (72- or 56-h after PGF2α for 14- or 5-d regimens, respectively). There were differences (P < 0.01) between STAI and FTAI treatments for %ERR (81.3 % and 64.4 %) and %P/AI (61.2 % and 55.4 %). Estrous synchronization regimen by AI treatment interaction (P < 0.05) showed that the %ERR were 79.8 %, 82.6 %, 66.2 % and 62.8 % and the %P/AI were 58.9 %, 63.4 %, 56.5 % and 56.5 % (for 14-d/STAI, 5-d/STAI, 14-d/FTAI and 5-d/FTAI, respectively). In conclusion, the 5-d CIDR with 64+84-h STAI combination was the most effective because of the greater %P/AI when this regimen was imposed.

Ovarian response and conception rate following oestrus synchronization using three protocols in Egyptian buffalo heifers

Objective: The aim of this study was to monitor the ovarian response and conception rate following estrous synchronization using CIDR, Ovsynch and double prostaglandin F2α protocols in Egyptian buffalo heifers. Material and methods: A total of 80 cyclic buffalo heifers were divided into four equal groups: CIDR (intravaginal progesterone releasing device, EAZI-BREEDTM CIDR®), Ovsynch (GnRH, PGF2α, GnRH injections), PGF (double PGF2α doses) and control. Timed artificial insemination (TAI) was performed in all heifers. All animals were exa - mined using ultrasound and blood samples were collected for measurement of progesterone. Results: A new follicular wave occurred earlier in the Ovsynch and PGF groups than in the CIDR group (p < 0.05). The mean diameter of the ovulatory follicle was smaller in the CIDR group than in the Ovsynch and PGF groups (p < 0.05). The ovulation rate was 100% in the CIDR group, 75% in the Ovsynch group and 70% in the PGF group. In the control group a lower pregnancy rate (20%) was determined in than in the CIDR (35%), Ovsynch (40%) and PGF (35%) groups. Progesterone concentrations were numerically higher in pregnant heifers of the CIDR group but the difference was non-significantly compared to the Ovsynch, PGF and control groups (p > 0.05). Conclusion and clinical relevance: EAZIBREEDTM CIDR®, Ovsynch-based TAI and PGF protocols were effective in synchronizing oestrus and resulted in nearly similar pregnancy rates in Egyptian buffalo heifers.

Fertility of Holstein heifers after two doses of PGF2α in 5-day CO-Synch progesterone-based synchronization protocol

The objective of the study was to determine the effect of three different PGF2α (PGF) treatments in the 5-day CO-Synch progesterone-based synchronization protocol on artificial insemination (AI) pregnancy rate (PR) in Holstein heifers in Turkey and the United States. We hypothesized that two doses of PGF administered concurrently or 6 hours apart would result in greater AI pregnancy compared with a single dose of PGF on Day 5 at controlled internal drug release (CIDR) removal. In Turkey, Holstein heifers (n = 450) from one farm in the province of Adana and another farm in the province of Bursa were included. In the US, Holstein heifers (n = 483) from two locations in the state of Idaho were included. Heifers within locations were randomly allocated to one of three protocol groups: 1PGF-received 25 mg IM of dinoprost at CIDR removal; 2Co-PGF-received 50 mg IM of dinoprost at CIDR removal, and 2PGF-received 25 mg IM of dinoprost at CIDR removal and an additional 25 mg IM of dinoprost 6 hours later. All heifers received a CIDR (1.38 g of progesterone) and GnRH (10 μg IM of Buserelin [Turkey] or gonadorelin hydrochloride [US]) on Day 0. The CIDRs were removed on Day 5, and each heifer was given PGF according to the assigned treatments. On Day 7, each heifer was given another dose of GnRH and concurrently inseminated at 56 hours after CIDR removal. Heifers in both experiments were examined for pregnancy status between 35 and 45 days after AI. Overall, controlling for age, the heifers in the 2PGF group had greater AI-PR (61.7% [192/311]) than heifers in 2Co-PGF (48.2% [149/309]; P < 0.001) or 1PGF (53.7% [168/313]; P < 0.05) groups. No difference was observed between 2Co-PGF and 1PGF groups (P > 0.1). In Turkey, the heifers in the 2PGF group had a greater AI-PR (60% [90/150]) than 2Co-PGF (45.3% (68/150); P < 0.01] group. No difference was observed between 2PGF and 1PGF (55.3% [83/150]) groups (P > 0.1). There was a trend for AI pregnancy between 1PGF and 2Co-PGF groups (P = 0.08). In the United States, the heifers in the 2PGF group had a greater AI-PR (63.4% [102/161]) than the heifers in 2PGF (50.9 [81/159]; P < 0.05) or 1PGF (52.1% [85/163]; P < 0.05) groups. Heifers that were 15- and 16-month old achieved greater AI-PR than 17- and 18-month-old heifers (59.2 [342/578] vs. 47.0% [168/355]; P < 0.01). In conclusion, administration of 2PGF at 6 hours apart on Day 5 at CIDR removal in a 5-day CO-Synch + CIDR protocol resulted in greater AI pregnancy. A greater number of 15- and 16-month-old heifers became pregnant compared with 17- and 18-month-old heifers.

Fertility after two doses of PGF2α concurrently or at 6-hour interval on the day of CIDR removal in 5-day CO-Synch progesterone-based synchronization protocols in beef heifers

Timed artificial insemination protocols in beef cattle are designed to synchronize ovulation in a greater proportion of females while simultaneously achieving acceptable pregnancy rates and a concise calving season. Protocols achieving such goals reduce time and labor associated with estrus detection and make advanced reproductive technologies implementable for beef producers. The objective of the study was to determine the effect of three different PGF2α (PGF) dosage schemes on artificial insemination (AI) pregnancy rates in beef heifers. We hypothesized that two doses of PGF administered concurrently at the time of controlled internal drug release (CIDR) removal would attain similar pregnancy rates compared with two doses given 6-hours apart-one at CIDR removal and the next 6 hours later in the 5-day CO-Synch progesterone-based synchronization protocol. Angus heifers (n = 875) at six locations in Washington, Idaho, and Oregon states were included in this study. Heifers within locations were assigned a body condition score (BCS). All heifers received a CIDR (1.38 g of progesterone) and 100 μg IM of GnRH on Day 0. The CIDRs were removed on Day 5, heifers were randomly allocated to one of three protocol groups: 1PGF (n = 291), received 25 mg IM of dinoprost (PGF); 2CO-PGF (n = 291), received 50 mg IM of dinoprost at CIDR removal, 2PGF (n = 293), received 25 mg IM of dinoprost at CIDR removal, and an additional 25 mg IM of dinoprost 6 hours later. Each heifer was given GnRH (100 μg, IM) and artificially inseminated at 56 hours after CIDR removal. Heifers were examined for pregnancy status between 50 and 70 days after AI to determine time of conception. A mixed-model procedure (PROC GLIMMIX of SAS) was used to evaluate the effect of treatments (1PGF, 2CO-PGF, and 2PGF) on AI pregnancy rates. Models included were treatments, BCS categories (≤5 and >5), and treatment by BCS category interaction. Location (state), handling facilities, handlers, inseminators, and AI sires were included as a random effect in the model. The 2PGF group had greater AI pregnancy rate of 63.6% (185/291), compared with the 2CO-PGF group at 51.9% (151/291) and 1PGF group at 54.9% (161/293; P < 0.001). An AI pregnancy rate of 50% (104/208) was observed for heifers with BCS less than or equal to 5 versus 58.9% (393/667) for heifers with BCS greater than 5 (P < 0.05). Location did not influence the AI pregnancy rate (P > 0.1). In conclusion, beef heifers received two 25-mg doses of PGF at 6-hour interval on Day 5 at CIDR insert removal in a 5-day CO-Synch + CIDR synchronization protocols achieved greater pregnancy compared with heifers received 50 mg of PGF concurrently at CIDR removal.

The requirement of GnRH at the beginning of the five-day CO-Synch + controlled internal drug release protocol in beef heifers

The objective of this study was to determine if the omission of GnRH at controlled internal drug release device (CIDR) insertion would impact pregnancy rates to timed AI (TAI) in beef heifers enrolled in a 5-d CO-Synch + CIDR protocol that used 1 PGF2α dose given at CIDR removal. Yearling beef heifers in Ohio in 2 consecutive breeding seasons (2011, n = 151, and 2012, n = 143; Angus × Simmental), Utah (2012, n = 265; Angus × Hereford), Idaho (2012, n = 127; Charolais), and Wyoming (2012, n = 137; Angus) were enrolled in the 5-d CO-Synch + CIDR protocol. At CIDR insertion (d -5), heifers were randomly assigned either to receive 100 μg GnRH (GnRH+; n = 408) or not to receive GnRH (GnRH-; n = 415). At CIDR removal (d 0 of the experiment), 25 mg PGF2α was administered to all heifers. All heifers were inseminated by TAI and given 100 μg GnRH 72 h after PGF2α (d 3). In heifers at the Ohio locations (n = 294), presence of a corpus luteum (CL) at CIDR insertion (d -5) was determined via assessment of progesterone concentrations (2011) and ovarian ultrasonography (2012). Subsequently, in both years, ovarian ultrasound was conducted on d 0 to determine the presence of a new CL. In this same subgroup of heifers, blood samples for progesterone analysis were collected on d 3 to assess luteal regression. Pregnancy diagnosis was performed between 32 and 38 d after TAI. At CIDR withdrawal, presence of a new CL was greater (P < 0.05) in the GnRH+ (55.8%, 82/147) than GnRH- (26.5%, 39/147) treatment. Incidence of failed luteal regression did not differ between the GnRH+ (3.4%) and GnRH- (0.7%) treatments. Pregnancy rate to TAI did not differ between the GnRH+ (50.5%) and GnRH- (54.9%) treatments. In conclusion, although the incidence of a new CL at CIDR removal was increased in the GnRH+ treatment, omission of the initial GnRH treatment in the 5-d CO-Synch + CIDR protocol did not influence TAI pregnancy rate in yearling beef heifers. In addition, a single dose of PGF2α at CIDR removal was effective at inducing luteolysis in yearling beef heifers enrolled in the 5-d CO-Synch + CIDR protocol, regardless of whether or not the initial GnRH treatment was given.

Effect of the first GnRH and two doses of PGF2α in a 5-day progesterone-based CO-Synch protocol on heifer pregnancy

The objectives were (1) to determine the effects of gonadorelin hydrochloride (GnRH) injection at controlled internal drug release (CIDR) insertion on Day 0 and the number of PGF2α doses at CIDR removal on Day 5 in a 5-day CO-Synch + CIDR program on pregnancy rate (PR) to artificial insemination (AI) in heifers; (2) to examine how the effect of systemic concentration of progesterone and size of follicles influenced treatment outcome. Angus cross beef heifers (n = 1018) at eight locations and Holstein dairy heifers (n = 1137) at 15 locations were included in this study. On Day 0, heifers were body condition scored (BCS), and received a CIDR. Within farms, heifers were randomly divided into two groups: at the time of CIDR insertion, the GnRH group received 100 μg of GnRH and No-GnRH group received none. On Day 5, all heifers received 25 mg of PGF2α at the time of CIDR insert removal. The GnRH and No-GnRH groups were further divided into 1PGF and 2PGF groups. The heifers in 2PGF group received a second dose of PGF2α 6 hours after the administration of the first dose. Beef heifers underwent AI at 56 hours and dairy heifers at 72 hours after CIDR removal and received 100 μg of GnRH at the time of AI. Pregnancy was determined approximately at 35 and/or 70 days after AI. Controlling for herd effect (P < 0.06), the treatments had significant effect on AI pregnancy in beef heifers (P = 0.03). The AI-PRs were 50.3%, 50.2%, 59.7%, and 58.3% for No-GnRH + PGF + GnRH, No-GnRH + 2PGF + GnRH, GnRH + PGF + GnRH, and GnRH + 2PGF + GnRH groups, respectively. The AI-PRs were ranged from 50% to 62.4% between herds. Controlling for herd effects (P < 0.01) and for BCS (P < 0.05), the AI pregnancy was not different among the treatment groups in dairy heifers (P > 0.05). The AI-PRs were 51.2%, 51.9%, 53.9%, and 54.5% for No-GnRH + PGF + GnRH, No-GnRH + 2PGF + GnRH, GnRH + PGF + GnRH, and GnRH + 2PGF + GnRH groups, respectively. The AI-PR varied among locations from 48.3% to 75.0%. The AI-PR was 43.5%, 50.4%, and 64.2% for 2.5 or less, 2.75 to 3.5, and greater than 3.5 BCS categories. Numerically higher AI-PRs were observed in beef and dairy heifers that exhibited high progesterone concentrations at the time of CIDR insertion (>1 ng/mL, with a CL). In addition, numerically higher AI-PRs were also observed in heifers receiving CIDR + GnRH with both high and low progesterone concentration (<1 ng/mL) initially compared with heifers receiving a CIDR only with low progesterone. In dairy heifers, there were no differences in the pregnancy loss between 35 and 70 days post-AI among the treatment groups (P > 0.1). In conclusion, GnRH administration at the time of CIDR insertion is advantageous in beef heifers, but not in dairy heifers, to improve AI-PR in the 5-day CIDR + CO-Synch protocol. In addition, in this study, both dairy heifers that received either one or two PGF2α doses at CIDR removal resulted in similar AI-PR in this study regardless of whether they received GnRH at CIDR insertion.

Artificial insemination at 56 h after intravaginal progesterone device removal improved AI pregnancy rate in beef heifers synchronized with five-day CO-Synch + controlled internal drug release (CIDR) protocol

The objective was to determine whether timed artificial insemination (TAI) 56 h after removal of a Controlled Internal Drug Release (CIDR, 1.38 g of progesterone) insert would improve AI pregnancy rate in beef heifers compared to TAI 72 h after CIDR insert removal in a 5-days CO-Synch + CIDR protocol. Angus cross beef heifers (n = 1098) at nine locations [WA (5 locations; n = 634), ID (2 locations; n = 211), VA (one location; n = 193) and WY (one location; n = 60)] were included in this study. All heifers were given a body condition score (BCS; 1-emaciated; 9-obese), and received a CIDR insert and 100 μg of gonadorelin hydrochloride (GnRH) on Day 0. The CIDR insert was removed and two doses of 25 mg of dinoprost (PGF(2α)) were given, first dose at CIDR insert removal and second dose 6 h later, on Day 5. A subset of heifers (n = 629) received an estrus detector aid at CIDR removal. After CIDR removal, heifers were observed thrice daily for estrus and estrus detector aid status until they were inseminated. Within farm, heifers were randomly allocated to two groups and were inseminated either at 56 h (n = 554) or at 72 h (n = 544) after CIDR removal. All heifers were given 100 μg of GnRH at AI. Insemination 56 h after CIDR insert removal improved AI pregnancy rate compared to insemination 72 h (66.2 vs. 55.9%; P < 0.001; 1 - β = 0.94). Locations, BCS categories (≤ 6 vs. > 6) and location by treatment and BCS by treatment interactions did not influence AI pregnancy rate (P > 0.1). The AI pregnancy rates for heifers with BCS ≤ 6 and > 6 were 61.8 and 60.1%, respectively (P > 0.1). The AI pregnancy rates among locations varied from 54.9 to 69.2% (P > 0.1). The AI pregnancy rate for heifers observed in estrus at or before AI was not different compared to heifers not observed in estrus [(65.4% (302/462) vs. 52.7% (88/167); P > 0.05)]. In conclusion, heifers inseminated 56 h after CIDR insert removal in a 5-days CO-Synch + CIDR protocol had, on average, 10.3% higher AI pregnancy rate compared to heifers inseminated 72 h after CIDR insert removal.