Effect of increasing amounts of supplemental progesterone in a timed artificial insemination protocol on fertility of lactating dairy cows

Comparison of three reproductive management strategies for lactating dairy cows using combination of estrus detection or ovulation synchronization and Fixed-Timed Artificial Insemination

The objective of this study was to compare the reproductive performance of lactating dairy cows submitted to first AI after combination of estrus detection and fixed timed AI (FTAI) and FTAI only. Cows were randomly assigned to receive AI at detected estrus between 50 and 70 d in milk (DIM), if not detected in estrus, were enrolled in either Ovsynch (ED-Ov, n = 485) or PRIDsynch (ED-PR, n = 505) protocols; or received FTAI at 80 DIM after Double-Ovsynch protocol (DO, n = 501). Cows were body condition scored (BCS) at calving and at 43 DIM; and evaluated for postpartum disorders within 7 d postpartum; clinical mastitis, lameness and bovine respiratory disease were recorded until first AI. Ovarian cyclicity was monitored at 43 and 50 DIM, and at 70 and 77 DIM. Pregnancy diagnoses (PD) were performed at 32 and 63 d after AI. Overall prevalence of postpartum anovulation was 7.8%. Pregnancy per AI (P/AI) did not differ between reproductive strategies at 32 d PD (ED-Ov = 43.2%; ED-PR = 41.7%; DO= 45.3%). Primiparous cows had greater P/AI than multiparous cows (53.7% vs 36.8%). Cows on farm 1 had lower P/AI compared with their counterparts on farm 2 (42.1% vs 45.4%). Cows with BCS > 2.5 at 43 DIM had greater P/AI compared with cows with BCS ≤ 2.5 (44.5% vs 34.7%). Similar P/AI for cow's receiving AI at detected estrus and FTAI, low prevalence of disease anovulation may have contributed to the similar performance of ED-Ov, ED-PR and DO.

Presynchronization with prostaglandin F2α and gonadotropin-releasing hormone simultaneously improved first service pregnancy per artificial insemination in lactating Holstein cows compared with Presynch-14 when combined with detection of estrus

This study aimed to determine the effect of 2 simple breeding strategies combining artificial insemination (AI) after detection of estrus (AIED) and timed AI (TAI) on first-service fertility in lactating Holstein cows. Weekly, lactating Holstein cows (n = l,049) between 40 and 46 d in milk (DIM) were randomly assigned to initiate 1 of 2 breeding strategies for first service: Presynch-14 and PG+G. Presynch-14 is a presynchronization strategy with 2 PGF_2α treatments 14 d apart with the last PGF_2α 14 d before the initiation of the Ovsynch protocol. Cows treated with PG+G receive a simpler presynchronization program that uses PGF_2α and GnRH simultaneously 7 d before Ovsynch. In both treatments, cows detected in standing estrus by tail chalk at any time ≥55 DIM were inseminated, and treatment was discontinued (n = 525). Cows completing treatment received TAI from 78 to 84 DIM (n = 526). In a subgroup of cows that received TAI, blood was collected (n = 163) to assess circulating concentrations of progesterone, and ultrasonographic evaluations of ovaries were performed on the day of first GnRH of Ovsynch (n = 162) and PGF_2α of Ovsynch (n = 122). The proportion of cows that received TAI was greater for PG+G compared with Presynch-14 (63.5 vs. 31.9%), which increased DIM at first service for cows treated with PG+G compared with Presynch-14 (75.5 ± 0.4 vs. 68.7 ± 0.4). For cows receiving TAI, the ovulatory response to first GnRH of Ovsynch (73.8 vs. 48.8%) and the proportion of cows with functional corpora lutea (92.6 vs. 73.1%) were greater for PG+G than Presynch-14. Cows treated with PG+G had greater overall pregnancy per AI (P/AI) 42 ± 7 d after AI (40.2 vs. 33.6%) and calving per AI (32.1 vs. 25.2%) than Presynch-14. For cows receiving AIED, treatment did not affect P/AI 42 ± 7 d after AI. However, for cows receiving TAI, PG+G increased P/AI compared with Presynch-14 (44.6 vs. 35.2%). Overall, cows receiving TAI had greater P/AI 42 ± 7 d after AI (42.5 vs. 31.5%) and calving per AI (34.1 vs. 23.7%) and decreased pregnancy loss (16.8 vs. 25.2%) than cows receiving AIED. In summary, PG+G increased the proportion of cows receiving TAI and the DIM at first service, P/AI, and calving per AI compared with Presynch-14 when both TAI programs were combined with AIED.

Plasma concentrations of progesterone in the preceding estrous cycle are associated with the intensity of estrus and fertility of Holstein cows

The aim of this study was to determine the association between concentrations of progesterone (P4) during previous the estrous cycle with the intensity of spontaneous or estrogen-induced estrous expression and pregnancy per artificial insemination (P/AI). A total of 1,953 AI events from lactating Holstein cows were used, consisting of 1,289 timed AI events from experiment 1 (Exp. 1) and 664 AI events from experiment 2 (Exp. 2). In Exp. 1, cows were bred after a timed AI protocol based on estradiol and P4. In Exp. 2 animals were bred upon spontaneous estrus detection. In both experiments cows were continuously monitored by an automated activity monitor (AAM), in Exp.1 a relative increase of activity was calculated (i.e., percentage of increase activity at estrus compared to cow's baseline activity) and in Exp.2, activity data from each cow were computed into an index value that ranged from 0 to 100. In Exp.2 duration (hours) of estrus were calculated and defined as the total time above the threshold (35 index). The intensity of estrous expression was determined for each event and classified as either high or low intensity using the median of each experiment. Blood samples were collected for P4 analysis in Exp. 1 at -4 d, 0 d, and 7 d relative to timed AI, and in Exp. 2 immediately following estrus (0 d), 7 d, 14 d, and 21 d post-AI. Concentration of P4 was classified as greater or lower according to the median value in each experiment. Cows with lower concentrations of P4 at AI had greater estrous expression in Exp. 1 (363.6 ± 5.2 vs. 275.9 ± 8.0% relative increase) and Exp. 2 (76.7 ± 1.9 vs. 67.4 ± 4.7 index; and 12.5 ± 0.5 vs. 9.3 ± 1.8 hours). Cows with a greater intensity of estrous expression at timed AI had greater concentrations of P4 at -4 d than cows with lower intensity estrus or no estrous expression (4.6 ± 0.2 vs. 3.6 ± 0.2 vs. 3.7 ± 0.2 ng/mL). Cows with greater concentrations of P4 at -4 d had greater P/AI (32.8 ± 4.4 vs. 22.4 ± 4.5%), whereas cows with lesser concentrations of P4 at d0 for either timed AI (35.2 ± 3.4 vs. 19.6 ± 4.6%) or spontaneous estrus (31.8 ± 2.8 vs. 23.4 ± 3.2%) had greater P/AI. Cows with greater concentrations of P4 7 d post-timed AI had greater P/AI compared with cows that had lower concentration of P4 (39.1 ± 2.9 vs. 24.7 ± 2.6%). Similarly, cows that had lower concentrations of P4 at 7 d, 14 d and 21 d post-spontaneous estrus tended to have lower P/AI when compared with cows with greater concentrations of P4. Overall, concentrations of P4 prior to and at AI were associated with greater estrous intensity and P/AI at both spontaneous and timed AI events.

Luteal Presence and Ovarian Response at the Beginning of a Timed Artificial Insemination Protocol for Lactating Dairy Cows Affect Fertility: A Meta-Analysis

Progesterone (P4) concentration during follicular growth has a major impact on fertility response in timed artificial insemination (TAI) protocols. Luteal presence at the beginning of a TAI protocol and ovarian response after the first gonadotropin-releasing hormone (GnRH) injection (G1) affect P4 concentration and subsequently pregnancy per artificial insemination (P/AI). A systematic review of the literature and meta-analytical assessment was performed with the objective of evaluating the magnitude of the effect of luteal presence and ovarian response at the beginning of a TAI protocol on P/AI in lactating dairy cows. We considered only studies using synchronisation protocols consisting of GnRH and prostaglandin F _2α. The time interval between G1 and prostaglandin F _2α (PGF _2α) had to range from 5 to 7 d. The time interval between the PGF _2α injection and G2 had to range from 48 to 72 h. We used 28 controlled experiments from 27 published manuscripts including 16,489 cows with the objective of evaluating the effect size of having a functional corpus luteum (CL) at G1 on P/AI. Information regarding ovulatory response after G1 was available for 5676 cows. In a subset of cows (n = 4291), information was available for luteal presence and ovulatory response at the initiation of the TAI protocol. A functional CL at G1 increased (p < 0.001) the relative risk of conceiving (RR (relative risk) = 1.32; 95% CI = 1.21-1.45) in lactating dairy cows. Ovulation after G1 increased (p < 0.001) the relative risk of conceiving (RR = 1.29; 95% CI = 1.20-1.38) in lactating dairy cows. The effect of ovulatory response on P/AI after G1 was affected by luteal presence at G1. In summary, there was a clear benefit on P/AI for cows starting a TAI protocol with a functional CL (+10.5 percentage units) and cows ovulating at the beginning of a TAI protocol (+11.0 percentage units).

Efficacy of ovulation synchronization with timed artificial insemination in treatment of follicular cysts in dairy cows

The efficacy of five ovulation-synchronization protocols with FTAI in treatment of cows diagnosed with follicular cysts was investigated in a nonrandomized study in a single herd. Cows identified with follicular structures >25 mm on two subsequent ultrasonographic (USG) examinations 7-10 days apart (n = 552) were assigned to one of the five treatment regimens on the day of the second USG examination. Treatment regimens were Ovsynch (GnRH-7d-PGF2α-56 h-GnRH-16 h-FTAI), New-CIDR (as Ovsynch with a new CIDR insert being fitted between days 0 and 7), Reused-CIDR (as New-CIDR but the CIDR insert was previously used for 7 days in another cow), G-New CIDR (Pre-GnRH on day 0 with the New-CIDR regimen being initiated 7 days later), and RG-Ovsynch (Pre-GnRH on day 0 and then every 7 days until detection of a luteal structure upon USG examination; at that point the Ovsynch was initiated). A subset of cows was subjected to ovarian USG examination at the time of PGF_2α administration, at insemination, and 8-10 days post-insemination. Progesterone-releasing ability of new and reused CIDR inserts were evaluated in cows diagnosed with severe ovarian inactivity (n = 16). The data were analyzed using logistic regression with pregnancy per AI on days 30 (P/Al 30) and 70 (P/AI 70) post-insemination were included as outcome measures. Compared with Ovsynch, RG-Ovsynch improved the P/AI 30 (OR = 2.6, P = 0.03) and the P/AI 70 (OR = 2.5, P = 0.05). New-CIDR and G-New CIDR were associated with non-significant increase in P/AI 30 (OR = 2.1, P = 0.09 and OR = 2.3, P = 0.07, respectively) and P/AI 70 (OR = 2.01, P = 0.09 and OR = 2.2, P = 0.09, respectively). Reused-CIDR was not associated with improvement in P/AI (P = 0.93 and 0.79 for P/AI 30 and P/AI 70, respectively). RG-Ovsynch had a longer diagnosis-to-FTAI interval (median 24, IQR 17,31). The dominant ovarian structures and the presence of a cyst or a luteal structure at PGF_2α administration or at insemination were not associated with P/AI. The new and re-used CIDR inserts produced comparable concentrations of serum progesterone 3 h, 3 days and 7 days post CIDR insertion. In conclusion, the RG-Ovsynch improved the P/AI whereas the New-CIDR and the G-New CIDR regimens tended to increase the P/AI compared with Ovsynch. Marginal differences in P/AI between RG-Ovsynch, New-CIDR, and G-New-CIDR together with prolonged diagnosis-to-FTAI in RG-Ovsynch should be considered if to evaluate the economic value of these regimens.

Fertility response of lactating dairy cows subjected to three different breeding programs under subtropical conditions

Background

It is comprehensively recognized that reduced reproductive efficiency represents a great economic loss to dairy producers. Ovarian cysts and anestrus syndromes are considered the greatest significant causes of low reproductive efficiency in dairy herds worldwide as they detrimentally affect the longevity and profitability of dairy herd. Pregnancy rate is the best available single deciding parameter used for assessment of the reproductive efficiency at the herd level which measures the probability that open cows become pregnant per unit of time. So, the current study was planned to evaluate the suitability of using Ovsynch plus CIDR and G6G resynchronization protocols as an efficient treatment regimen for cystic ovarian diseased cows and anestrus cows, respectively, through comparing pregnancy rates of cystic ovarian diseased cows that subjected to Ovsynch supplemented with controlled internal drug release device with the pregnancy rate of healthy cows that subjected to a Presynch-Ovsynch synchronization protocol, as well as through comparing pregnancy rates of anestrus cows that subjected to G6G treatment protocol with the pregnancy rate of healthy cows. Moreover, possible factors such as breed, parity, and season which may affect the treatment success were also evaluated.

Results

The results of the current study revealed an overall mean pregnancy rate of 36.64%. Moreover, Simmental cows recorded a greater (p < 0.01) pregnancy rate (45.16%) than that recorded for Holstein cows (34.98%). A highly significant seasonal effect was observed, as a higher (p < 0.01) pregnancy rate was recorded for cows inseminated during cold months (39.54%) compared with that recorded for cows inseminated during hot months (29.18%).

Conclusions

No significant differences were detected in the pregnancy rates among the three breeding programs; thence, the application of the G6G synchronization protocol for anestrus cows and Ovsynch-CIDR synchronization protocol for cows with ovarian cysts could be used as effective treatment regimens as they resulted in nearly the same pregnancy rates that recorded for healthy cows. In addition, the treatment response was highly influenced by cow’s breed, parity, and season of breeding.

A shortened resynchronization treatment for dairy cows after a nonpregnancy diagnosis

We hypothesized that a shortened version of a modified Ovsynch program (OVS: GnRH-1 - 7 d - PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI) that excluded GnRH-1 to resynchronize ovulation in cows bearing a corpus luteum (CL) after a non-pregnancy diagnosis (NPD) or including progesterone supplementation with the OVS treatment for cows without a CL would produce shorter inter-insemination intervals and pregnancy per AI (P/AI) not different from that of cows treated with the OVS treatment. Of the 1697 lactating Holstein cows enrolled in this experiment, complete data were available for only 1584 cows because the remainder was not treated, inseminated per treatment design, left the herd before pregnancy diagnosis, or some other outcome was missing. Cows were enrolled in the study and assigned to either of three treatments at NPD (32 ± 3 d after AI [Day 0]). Cows with a detected CL were assigned randomly to: (1) a modified Ovsynch (OVS; GnRH-1 - 7 d - PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI) or (2) Short Synch (SS; PGF_2α-1 - 24 h - PGF_2α-2 - 32 h - GnRH-2 - 16 h - AI). Cows with no CL were assigned to OVS plus a progesterone insert (CIDR). Blood was collected at NPD to measure progesterone concentration and determine accuracy of treatment assignment (progesterone ≥ 1 ng/mL for a functional CL). Overall progesterone concentration at NPD was less in OVS + CIDR cows (1.5 ± 0.3 ng/mL) than in OVS (5.2 ± 0.2 ng/mL) or SS cows (3.7 ± 0.3 ng/mL). No differences in luteolytic risk (progesterone < 0.5 ng/mL at 72 h after PGF_2α-1) were detected after PGF_2α (>96.7%) and ovulation risk after GnRH-2 was 93.8, 91.7, and 86.2% for SS, OVS, and OVS + CIDR, respectively. Mean and median inter-insemination interval were less in SS (mean = 34.3 ± 0.05 d [median = 35 d] than OVS cows (40.2 ± 0.05 d [42 d]), but that in OVS cows did not differ from OVS + CIDR cows (41.4 ± 0.05 d [42 d]). Technicians were more accurate in visually detecting a functional CL than a non-functional CL (81.2 vs. 61.1%). Sensitivity of detecting a functional CL by technicians averaged 91.2%, but specificity was 39.8%. Pregnancy per AI at 32 ± 3 d after AI was less for SS (16.5% [n = 115]) than OVS (29.3% [n = 133] when a functional CL was inaccurately detected, but did not differ when a functional CL was detected accurately (27.6% [n = 561] vs 30.3% [508]). Pregnancy per AI did not differ between OVS and OVS + CIDR cows regardless of CL status. Short synch is an alternative to the entire modified Ovsynch program to produce similar P/AI when the CL status was detected accurately, and regardless of functional CL status, SS reduced inter-insemination intervals by 7 d.

Circulating progesterone concentrations in nonlactating Holstein cows during reuse of intravaginal progesterone implants sanitized by autoclave or chemical disinfection

The aim of this study was to compare plasma progesterone (P4) concentrations in nonlactating, multiparous Holstein cows (n = 24) treated with 2 types of intravaginal implants containing either 1.0 or 1.9 g of P4 either at the first use or during reuse of the implants after sanitizing the implant by autoclave or chemical disinfection. In a completely randomized design with a 2 × 3 factorial arrangement and 2 replicates, every cow underwent 2 of 6 treatments. Two sources of P4 [controlled internal drug release (1.9 g of P4) from Zoetis (São Paulo, Brazil), and Sincrogest (1.0 g of P4) from Ourofino (Cravinhos, Brazil)] and 3 types of processing, new (N), reused after autoclave (RA), and reused after chemical disinfection (RC), were used. After inducing luteolysis to avoid endogenous circulating P4, the cows were randomized in 1 of 6 treatments (1.9 g of N, 1.9 g of RA, 1.9 g of RC, 1.0 g of N, 1.0 g of RA, and 1.0 g RC). Cows were treated with the implants for 8 d and during this period blood samples were collected at 0, 2, 12, 24, 48, 72, 96, 120, 144, 168, and 192 h. Statistical analyses were performed using Proc-Mixed and the mean ± standard error of the mean P4 concentrations were calculated using the Proc-Means procedures of SAS 9.4 (SAS Institute Inc., Cary, NC). No interaction between treatments was observed. Comparing types of implant, average P4 concentrations during treatments were greater for 1.9 g than 1.0 g (1.46 vs. 1.14 ± 0.04 ng/mL). When types of processing were compared, average P4 concentrations did not differ between autoclaved and new inserts (1.46 vs. 1.37 ± 0.05 ng/mL; respectively), but both were greater than chemically disinfected implants (1.09 ± 0.04 ng/mL). Within 1.9-g P4 inserts, P4 concentrations from autoclaved implants were greater than new, which were greater than chemically disinfected (1.67 ± 0.06 vs. 1.49 ± 0.07 vs. 1.21 ± 0.05 ng/mL; respectively). For 1.0-g P4 implants, P4 concentrations from autoclaved did not differ from new, but both were greater than chemically disinfected (1.20 ± 0.08 vs. 1.24 ± 0.06 vs. 0.97 ± 0.05 ng/mL; respectively). In conclusion, the mean plasma P4 concentration in nonlactating Holstein cows was greater for 1.9 than 1.0 g of P4 and regardless of the type of implant, the autoclaving process provided greater circulating P4 in relation to chemical disinfection, and similar or greater P4 concentrations compared with a new implant.

Presynchronization of lactating dairy cows with PGF2α and GnRH simultaneously, 7 days before Ovsynch have similar outcomes compared to G6G

The overarching objective of this study was to develop an alternative strategy for first and greater services that will improve fertility in lactating dairy cows for dairy operations limited by labor or other logistical constraints that make it difficult to use Presynch-11, G6G, or Double-Ovsynch. Our overall hypothesis was that simplification of a Presynch program through the combination of PGF2α and GnRH on the same day (PG + G), 7 days before the first GnRH of Ovsynch, would allow for similar ovulation and luteolysis rate and pregnancies per AI (P/AI) compared with G6G. Lactating dairy cows 58 to 64 days in milk (first service; n = 114), and cows diagnosed not pregnant 39 days after previous AI (second + service; n = 122) were blocked by parity and service and randomly assigned to control or PG + G. Control cows received G6G (n = 116) that consisted of PGF2α, 2-day GnRH, 6-day GnRH, 7-day PGF2α, 56-hour GnRH, and 16-hour AI. Treated cows (PG + G; n = 121) received PGF2α and GnRH, 7-day GnRH, 7-day PGF2α, 56-hour GnRH, and 16-hour AI. All cows received a second PGF2α 24 hours after the PGF2α of Ovsynch. First service cows received AI between 76 and 82 days in milk and second + service received AI 57 days after previous AI. Pregnancies/AI (n = 230) were similar in controls compared with treated cows on Day 35 (57 vs. 50%; P = 0.27) and Day 49 (54 vs. 47%; P = 0.33), respectively. Percent of cows ovulating after GnRH of the presynchronization was greater (P = 0.002) for controls vs. treated (80 vs. 58%); however, ovulation after first GnRH of Ovsynch was similar (67 vs. 68%; P = 0.86). Serum concentrations of progesterone were similar (P = 0.78) at the time of first GnRH of Ovsynch for control and treated cows (2.22 vs. 2.14 ng/mL). However, serum progesterone at the time of PGF2α of Ovsynch was greater (P = 0.002) for control cows compared with treated cows (5.75 vs. 4.64 ng/mL). In summary, administering both PGF2α and GnRH on the same day, 7 days before the start of Ovsynch, appears to be a simple alternative that results in acceptable P/AI but potentially less progesterone during the growth of the ovulatory follicle.

Pregnancy rate in dairy cows treated with progesterone for six days during estrus synchronization with PGF2α

The present study evaluated the effect of progesterone supplementation during a double PGF2α injection synchronization protocol on pregnancy per artificial insemination (P/AI) and on the incidence of twin births. Seven hundred and eighty three dairy cows were synchronized with two injections of PGF2α 14 days apart, starting on day 35 postpartum for their first postpartum insemination. Six days before the second PGF2α injection, cows were treated either with a progesterone-releasing intravaginal device (PRID-Delta) and an intramuscular injection of 500mg of progesterone (n=387) or served as control (n=396) and did not receive progesterone treatment. Cows were inseminated 12h after being detected in estrus. Pregnancy was diagnosed 40-45 days later by transrectal palpation. Progesterone administration improved (P<0.05) the percentage of cows detected in estrus in multiparous [(192/255) 75% vs (161/267) 60%], but not in primiparous cows [93/132 (70%) vs 90/129 (70%)]. Progesterone treatment increased P/AI in multiparous [53/192 (28%) vs 27/161 (17%)] but not in primiparous cows [25/93 (27%) vs 29/90 (32%)]. The incidence of twin births tended to be lower (P=0.09) in cows treated with progesterone [1/74 (1%)] than in the control group [4/53 (7%)]. It is concluded that progesterone administration during estrus synchronization with two PGF2α injections in dairy cows improves estral response and increases P/AI in multiparous, but not in primiparous cows, and tended to decrease the incidence of twin births.

Effect of extending the interval from Presynch to initiation of Ovsynch in a Presynch-Ovsynch protocol on fertility of timed artificial insemination services in lactating dairy cows

The specific objective of this study was to determine if increasing the interval between the Presynch and Ovsynch portion of the Presynch-Ovsynch protocol (Presynch: PGF2α-14 d-PGF2α and Ovsynch: GnRH-7 d-PGF2α-56 h-GnRH-16-20 h-timed artificial insemination) from 12 to 14 d would reduce the fertility of lactating dairy cows not detected in estrus after Presynch that receive timed artificial insemination (TAI). Cows from 4 commercial dairy farms (n=3,165) were blocked by parity (primiparous vs. multiparous) and randomly assigned to a 12 (PSOv14-12; n=1,566) or 14 d (PSOv14-14; n=1,599) interval between the second PGF2α (PGF) injection of Presynch (P2) and the beginning of Ovsynch. Cows detected in estrus any time between P2 and the day of the TAI were inseminated (AIED group). From a subgroup of cows (177 and 150 in PSOv14-12 and PSOv14-14, respectively), ovarian parameters and ovulation were evaluated through determination of concentrations of progesterone (P4) in blood and transrectal ultrasonography at the time of the first GnRH (GnRH1) and the PGF injection of Ovsynch. Overall, 52.8% (n=1,671) of the cows were AIED, whereas 47.2% (n=1,494) received TAI. For cows that received TAI, pregnancies per artificial insemination 39 d after artificial insemination were similar for PSOv14-12 (36.3%) and PSOv14-14 (36.0%) but were greater for primiparous (41.5%) than multiparous cows (33.6%). Pregnancy loss from 39 to 105 d after artificial insemination was similar for PSOv14-12 (4.8%) and PSOv14-14 (8.6%), for primiparous (6.4%) and multiparous cows (7.0%), but a tendency for a treatment by parity interaction was observed. Both treatments had a similar proportion of cows with a follicle ≥ 10 mm and similar follicle size at GnRH1; however, the ovulatory response to GnRH was greater for PSOv14-12 (62.2%) than PSOv14-14 (46.4%). A greater proportion of cows with a functional corpus luteum (75.3 vs. 65.6%) and greater concentrations of P4 (3.9 vs. 3.3 ng/mL) at GnRH1 in PSOv14-14 than PSOv14-12 may have compensated for the reduction in fertility expected due to reduced ovulatory response to GnRH1. We concluded that extending the interval from Presynch to Ovsynch from 12 to 14 reduced ovulatory response to GnRH1 but did not reduce the fertility of cows that received TAI when cows were inseminated in estrus after presynchronization. Thus, farms that combine AIED and TAI during the Presynch-Ovsynch protocol may use a 14-d interval between Presynch and Ovsynch to simplify their management without reducing fertility of cows receiving TAI.

Effect of time of progesterone supplementation on serum progesterone and the conception rate of cooled Holstein heifers during the summer

To investigate the effects of progesterone supplementation at two different times on serum progesterone (P4 ) concentration, conception rate and resynchronization of cooled Holstein heifers in summer, 90 heifers were randomly assigned to two groups: (i) heifers subjected to TAI (timed artificial insemination) and progesterone supplementation from days 4 to 14 after TAI (S1; n = 45); and (ii) heifers under the same TAI protocol as S1 and progesterone supplementation from days 17 to 22 after TAI (S2 ; n = 45). The groups S1 and S2 were cooled 10 days before and 21 days after TAI. Respiratory rate, body surface temperature, vaginal temperature and rectal temperature recorded during the experiment were not different (P > 0.05) between S1 and S2 groups. Progesterone concentration was not different (P > 0.05) in S1 compared to S2 . The conception rates on days 30 and 55 were similar between groups (P > 0.05). Progesterone supplementation did not increase either conception rate or concentrations of P4 in heifers during the summer. Heifers not pregnant to first service in the group S2 were resynchronized (77.7%) for a second breeding.

Short communication: Insertion of an intravaginal progesterone device at the time of gonadotropin-releasing hormone (GnRH) injection affects neither GnRH-induced release of luteinizing hormone nor development of dominant follicle in early diestrus of lactating dairy cows

Our objectives were to evaluate the acute effects of a controlled internal drug release (CIDR) insert containing 1.38 g of progesterone (P4) on the release of LH, follicular growth, and circulating concentrations of P4 in cows treated with GnRH at the time of CIDR insertion. Nonpregnant, lactating dairy cows (n=27) were blocked by parity, predicted 305-d mature-equivalent milk production, and body condition score and randomly assigned to 1 of 3 treatments: (1) CIDR insertion concurrent with an injection of 200 µg of GnRH (n=10; 2GP4); (2) CIDR insertion concurrent with an injection of 100 µg of GnRH (n=10; 1GP4); and (3) injection of 100 µg of GnRH (n=7; CON). Prior to onset of treatments, cows were submitted to a presynchronization protocol that consisted of a CIDR insert containing 1.38 g of P4 from d -7 to -2, 25mg of PGF2α on d -2 and -1, and 100 µg of GnRH on d 0. Experimental treatments were applied on d 6, the early luteal phase of the estrous cycle. Concentrations of P4 in plasma were determined on d -2 and 0 and at 0, 15, 30, 60, 120, 240, 345, 600, and 1,200 min relative to treatment on d 6. Concentrations of LH were determined in plasma samples obtained at 0, 15, 30, 60, 120, 240, and 345 min relative to treatment on d 6. Ultrasonography examinations of ovarian structures were performed on d -2, 0, 2, and at 0, 600, and 1,200 min relative to treatment on d 6. Mean concentrations of P4 in the CON group (1.91±0.28 ng/mL) were lower than in 2GP4 (3.40±0.26 ng/mL) and 1GP4 (3.31±0.24 ng/mL) groups, but concentrations in 2GP4 and 1GP4 were similar. Mean concentration of LH in response to the GnRH injection on d 6 was greatest in 2GP4 cows (3.08±0.21 ng/mL) and did not differ between 1GP4 (2.23±0.21 ng/mL) and CON (2.14±0.25 ng/mL) cows. The diameter of the dominant follicle on d 6 was similar among treatments (2GP4=15.34±0.50; 1GP4=15.31±0.50; CON=14.77±0.62 mm). In conclusion, CIDR insertion concurrent with a 100- or 200-µg dose of GnRH neither altered GnRH-induced LH release nor had an acute effect on dominant follicle growth.

Effect of progesterone supplementation on fertility responses of lactating dairy cows with corpus luteum at the initiation of the Ovsynch protocol

The objectives of this study were to determine the effects of supplemental progesterone on fertility responses of lactating dairy cows with a CL at the initiation of the timed artificial insemination (AI) program. Holstein cows were subjected to the Ovsynch protocol (Day -10 GnRH, Day -3 PGF2α, Day -0.7 GnRH, and Day 0 timed AI). Ovaries were scanned by ultrasonography on Day -10 and cows with CL were blocked by pen and assigned randomly to receive no supplemental progesterone (control, n = 863) or to receive a controlled internal drug-release (CIDR) insert containing progesterone from Days -10 to -3 (1CIDR, n = 862). Cows were observed for signs of estrus beginning on Day -9 based on removal of tail chalk and those in estrus received AI on the same day. Blood sampled from a subset of cows was analyzed for progesterone concentrations on Days -10, -9, -7, -5, -3, 0, 6, 13, and 19. Pregnancy was diagnosed on Days 32 and 60 after AI. Supplementation increased (P < 0.01) progesterone concentrations between Day -9 and -3 compared with control (7.5 vs. 6.2 ng/mL). Treatment had no effect on the ovulatory response to the first and final GnRH injections of the Ovsynch protocol, the proportion of cows that maintained their CL until the day of PGF2α injection, or the diameter of the ovulatory follicle before AI. Although the overall proportion of cows in estrus at AI did not differ between treatments, progesterone supplementation prevented (P < 0.01) cows from coming into estrus from Days -9 to -3 (0.0% vs. 4.7%), whereas it increased (P = 0.02) the proportion of cows inseminated in estrus from Days -2 to -1 (7.1% vs. 4.5%). Pregnancy per AI (P/AI) tended to be reduced (P = 0.06) by supplemental progesterone on Day 32 (40.5% vs. 45.0%), but not on Day 60 after AI (36.6% vs. 39.7%). A tendency for an interaction (P = 0.09) between treatment and the presence of CL at the PGF2α injection was observed for P/AI on Day 32 in cows that received timed AI because progesterone supplementation reduced P/AI in cows that maintained their CL until Day -3 (40.3% vs. 46.7%); however, it increased P/AI in those that did not have a CL at PGF2α (38.1% vs. 27.7%). Treatment did not affect pregnancy loss between Days 32 and 60 of gestation. In conclusion, incorporating a single intravaginal insert to the timed AI program increased progesterone concentrations in plasma by 1.3 ng/mL, but did not benefit fertility in dairy cows that have CL at the initiation of the synchronization protocol.

Economics of fertility in high-yielding dairy cows on confined TMR systems

The objective of this review paper was to summarise the latest findings in dairy cattle reproductive economics with an emphasis on high yielding, confined total mixed ration systems. The economic gain increases as the reproductive efficiency improves. These increments follow the law of diminishing returns, but are still positive even at high reproductive performance. Reproductive improvement results in higher milk productivity and, therefore, higher milk income over feed cost, more calf sales and lower culling and breeding expenses. Most high-yielding herds in the United States use a combination of timed artificial insemination (TAI) and oestrous detection (OD) reproductive programme. The ratio of achievable pregnancies between OD and TAI determines the economic value difference between both and their combinations. Nonetheless, complex interactions between reproductive programme, herd relative milk yield, and type of reproductive programme are reported. For example, higher herd relative milk yield would favour programme relying more on TAI. In addition, improved reproductive efficiency produces extra replacements. The availability of additional replacements could allow more aggressive culling policies (e.g. less services for non-pregnant cows) to balance on-farm supply and demand of replacements. Balancing heifer replacement availability in an efficient reproductive programme brings additional economic benefits. New technologies such as the use of earlier chemical tests for pregnancy diagnosis could be economically effective depending on the goals and characteristics of the farm. Opportunities for individual cow reproductive management within defined reproductive programme exist. These decisions would be based on economic metrics derived from the value of a cow such as the value of a new pregnancy, the cost of a pregnancy loss, or the cost of an extra day open.

Targeted progesterone supplementation improves fertility in lactating dairy cows without a corpus luteum at the initiation of the timed artificial insemination protocol

The objectives of this study were to determine the effect of supplemental progesterone on fertility in lactating dairy cows lacking a corpus luteum (CL) at the initiation of the timed artificial insemination (AI) program. Holstein cows were subjected to the 5-d timed AI program (d -8 GnRH, d -3 and -2 PGF2α, d 0 GnRH and AI). Cows had their ovaries scanned by ultrasonography on d -8 and those bearing a CL were considered to be in diestrus (DI; n=946). Cows that lacked a CL on d -8 were assigned to remain as untreated control (CON; n=234) or receive 2 controlled internal drug release (CIDR) inserts containing progesterone (2CIDR; n=218) from d -8 to -3, as a single insert has been proven insufficient to modulate fertility in cows without CL. Blood was analyzed for progesterone and estradiol concentrations. Pregnancy was diagnosed on d 34 and 62 after AI. Progesterone concentrations during the timed AI program were lowest for CON, intermediate for 2CIDR, and highest for DI. Supplementation increased progesterone concentrations between d -7 and -3 compared with CON (2.65 vs. 0.51 ng/mL). Ovulation to the first GnRH was not affected by treatment. However, a greater proportion of CON and 2CIDR cows had a new CL on d -3 compared with DI cows (66.7 vs. 61.9 vs. 52.0%). In cows with a new CL, the diameter of the ovulatory follicle was larger for CON than 2CIDR, and intermediate for DI (18.7 vs. 16.5 vs. 17.7 mm). Concentrations of estradiol on d -3 did not differ among treatments; however, DI cows had greater estradiol concentrations at AI compared with CON or 2CIDR cows. Pregnancy per AI was less for CON compared with 2CIDR or DI on d 32 (30.8 vs. 46.8 vs. 49.9%) and 64 (28.6 vs. 43.7 vs. 47.3%), indicating that supplementation with progesterone reestablished fertility in cows lacking a CL on d -8. A greater proportion of nonpregnant CON cows had a short reinsemination interval compared with 2CIDR or DI (11.1 vs. 3.5 vs. 5.7%). Treatment did not affect pregnancy loss between d 34 and 62 of gestation. A single ultrasound exam was effective in identifying a low-fertility cohort of cows based on the absence of CL at the first GnRH injection of the timed AI protocol. Progesterone supplementation with 2 CIDR inserts increased progesterone in plasma to 2.65 ng/mL and restored fertility in lactating dairy cows lacking a CL at the initiation of the timed AI program similar to that of cows in diestrus.

Effects of treatment with human chorionic gonadotrophin or intravaginal progesterone-releasing device after AI on circulating progesterone concentrations in lactating dairy cows

Adequate circulating progesterone (P4) is important for pregnancy. Lactating dairy cattle have lower circulating P4, particularly when smaller follicles are ovulated during timed AI protocols. The aim of the present study was to determine the supplementation strategy that resulted in P4 concentrations in lactating dairy cattle similar to those in heifers. Lactating Holstein cows (n = 61) were synchronised using the Double-Ovsynch method and, on Day 5, were randomly assigned to receive no treatment (control), controlled internal drug release (CIDR), human chorionic gonadotrophin (hCG; 3300 IU) or CIDR+hCG. Heifers after normal oestrus were followed as controls (n = 10). Profiles of circulating P4 concentrations were compared using repeated-measures ANOVA. Heifers had greater P4 concentrations than control cows at all times after Day 5 (P < 0.0001). Cows receiving CIDR had lower P4 concentrations than heifers (P = 0.0037) on Days 8–16. Treatment with hCG generally caused ovulation and resulted in circulating P4 concentrations greater than those in control lactating cows by 3 days after treatment (Day 8 after AI), but the treatment × time interaction (P = 0.01) showed that cows treated with hCG generally had lower P4 concentrations than heifers. Supplementation with CIDR+hCG resulted in P4 concentration profiles similar to those in heifers. Thus, the use of CIDR and the production of an accessory corpus luteum with hCG elevates P4 concentrations in lactating cows to those seen in heifers. This information may be useful for designing future trials into P4 supplementation and fertility.

The use of endocrine treatments to improve pregnancy rates in cattle

Reproduction is critical for the success of both dairy and beef cattle production. Inadequate reproduction impairs profitability by compromising production, delaying genetic progress and increasing expenses. A major impediment to the use of artificial insemination (AI) is the ability to detect oestrus for optimum timing of breeding. However, increased understanding of the bovine oestrous cycle has led to the development of reproductive programmes that allow precise synchrony of follicle development, luteal regression and ovulation. The advent of timed-AI protocols revolutionised reproductive management in dairy and beef herds. It allows for AI at a more desired time post partum despite oestrous cyclicity. It also allows for pre-determined re-insemination of cows diagnosed as not pregnant. In subfertile cows, such as the post partum, anoestrous beef cow and the high-producing dairy cow, strategic hormone supplementation has been used to overcome hormone deficiencies and improve pregnancy rates. Several physiological windows have been identified to optimise fertility in synchronisation programmes and they include, but are not limited to, follicle turnover, synchrony of follicular development, length of dominance, progesterone concentrations during development of the ovulatory follicle, luteal regression, peri-ovulatory steroid concentrations, length of pro-oestrus, synchrony of ovulation and AI, and progesterone rise after ovulation.

Reduced progesterone concentration during growth of the first follicular wave affects embryo quality but has no effect on embryo survival post transfer in lactating dairy cows

Fertility of lactating dairy cows is associated with reduced progesterone (P4) concentration compared with nonlactating animals. The objective of the current study was to determine whether P4 during growth of the first follicular wave (FFW) affects embryo quality. Lactating Holstein cows at 33±3 days post partum were allocated to one of three treatments. Cows in the FFW and FFW with P4 (FFWP) treatments started the superstimulation protocol on day 1 of the estrous cycle and second follicular wave (SFW) cows started the superstimulation protocol on estrous cycle day 7. Cows were superstimulated with 400 mg of NIH-FSH-P1 (FSH) given twice daily for 5 days, two prostaglandin F2α (PGF2α) injections given with the ninth and tenth injections of FSH, GNRH given 48 h after the first PGF2α injection, and timed insemination 12 and 24 h after the GNRH injection. Cows in the FFWP treatment received two intravaginal P4 inserts during the superstimulation. Embryos were recovered 6.5 days after artificial insemination and excellent/good and fair embryos were frozen and transferred. Blood was sampled daily from estrous cycle day 0 until insemination from donor cows. During the superstimulation protocol, P4 was (P<0.01) greatest for SFW cows followed by FFWP and FFW cows respectively. The percentage of embryos–oocytes from SFW and FFWP cows classified as excellent/good and fair embryos was (P=0.02) greater than those of FFW cows. Pregnancy per embryo transfer was not (P≥0.73) affected by embryo donor treatment. Reduced embryo quality of cows induced to ovulate the follicles from the first follicular wave is a consequence of reduced P4 during follicle growth.

Effect of interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to a 5-d timed AI program

Objectives were to investigate 2 intervals from induction of ovulation to artificial insemination (AI) and the effect of supplemental progesterone for resynchronization on fertility of lactating dairy cows subjected to a 5-d timed AI program. In experiment 1, 1,227 Holstein cows had their estrous cycles presynchronized with 2 injections of PGF(2α) at 46 and 60 d in milk (DIM). The timed AI protocols were initiated with GnRH at 72 DIM, followed by 2 injections of PGF(2α) at 77 and 78 DIM and a second injection of GnRH at either 56 (OVS56) or 72h (COS72) after the first PGF(2α) of the timed AI protocols. All cows were time-inseminated at 72h after the first PGF(2α) injection. Pregnancy was diagnosed on d 32 and 60 after AI. In experiment 2, 675 nonpregnant Holstein cows had their estrous cycles resynchronized starting at 34 d after the first AI. Cows received the OVS56 with (RCIDR) or without (RCON) supplemental progesterone, as an intravaginal insert, from the first GnRH to the first PGF(2α). Pregnancy diagnoses were performed on d 32 and 60 after AI. During experiment 2, subsets of cows had their ovaries scanned by ultrasonography at the first GnRH, the first PGF(2α), and second GnRH injections of the protocol. Blood was sampled on the day of AI and 7 d later, and concentrations of progesterone were determined in plasma. Cows were considered to have a synchronized ovulation if they had progesterone <1 and >2.26 ng/mL on the day of AI and 7 d later, respectively, and if no ovulation was detected between the first PGF(2α) and second GnRH injections during resynchronization. In experiment 1, the proportion of cows detected in estrus at AI was greater for COS72 than OVS56 (40.6 vs. 32.4%). Pregnancy per AI (P/AI) did not differ between OVS56 (46.4%) and COS72 (45.5%). In experiment 2, cows supplemented with progesterone had greater P/AI compared with unsupplemented cows (51.3 vs. 43.1%). Premature ovulation tended to be greater for RCON than RCIDR cows (7.5 vs. 3.6%), although synchronization of the estrous cycle after timed AI was similar between treatments. Timing of induction of ovulation with GnRH relative to insemination did not affect P/AI of dairy cows enrolled in a 5-d timed AI program. Furthermore, during resynchronization starting on d 34 after the first AI, supplementation with progesterone improved P/AI in cows subjected to the 5-d timed AI protocol.

Resynchronization strategies to improve fertility in lactating dairy cows utilizing a presynchronization injection of GnRH or supplemental progesterone: I. Pregnancy rates and ovarian responses

Objectives were to evaluate 3 resynchronization protocols for lactating dairy cows. At 32+/-3 d after pre-enrollment artificial insemination (AI; study d -7), 1 wk before pregnancy diagnosis, cows from 2 farms were enrolled and randomly assigned to 1 of 3 resynchronization protocols after balancing for parity, days in milk, and number of previous AI. All cows were examined for pregnancy at 39+/-3 d after pre-enrollment AI (study d 0). Cows enrolled as controls (n=386) diagnosed not pregnant were submitted to a resynchronization protocol (d 0-GnRH, d 7-PGF2alpha, and d 10-GnRH and AI) on the same day. Cows enrolled in the GGPG (GnRH-GnRH-PGF2alpha-GnRH) treatment (n=357) received a GnRH injection at enrollment (d -7) and if diagnosed not pregnant were submitted to the resynchronization protocol for control cows on d 0. Cows enrolled in CIDR treatment (n=316) diagnosed not pregnant received the resynchronization protocol described for control cows with addition of a controlled internal drug release (CIDR) insert containing progesterone (P4) from d 0 to 7. In a subgroup of cows, ovaries were scanned and blood was sampled for P4 concentration on d 0 and 7. After resynchronized AI, cows were diagnosed for pregnancy at 39+/-3 and 67+/-3 d (California herds) or 120+/-3 d (Arizona herds). Cows in the GGPG treatment had more corpora lutea than CIDR and control cows on d 0 (1.30+/-0.11, 1.05+/-0.11, and 1.05+/-0.11, respectively) and d 7 (1.41+/-0.14, 0.97+/-0.13, and 1.03+/-0.14, respectively). A greater percentage of GGPG cows ovulated to GnRH given on d 0 compared with CIDR and control cows (48.4, 29.6, and 36.6%, respectively), but CIDR and control did not differ. At 39+/-3 d after resynchronized AI, pregnancy per AI (P/AI) was increased in GGPG (33.6%) and CIDR (31.3%) cows compared with control (24.6%) cows. At 67 or 120+/-3 d after resynchronized AI, P/AI of GGPG and CIDR cows was increased compared with control cows (31.2, 29.5, and 22.1%, respectively). Presynchronizing the estrous cycle of lactating dairy cows with a GnRH 7 d before the start of the resynchronization protocol or use of a CIDR insert within the resynchronization protocol resulted in greater P/AI after resynchronized AI compared with control cows.