Lattice QCD Equation of State at Finite Chemical Potential from an Alternative Expansion Scheme.

In this Letter, we introduce a novel scheme for extrapolating the equation of state of QCD to finite chemical potential that features considerably improved convergence properties and allows us to extend its reach to unprecedentedly high baryonic chemical potentials. We present continuum extrapolated lattice results for the new expansion coefficients and show the thermodynamic observables up to µ_{B}/T≤3.5. This novel expansion does not suffer from the shortcomings that characterize the traditional Taylor expansion method, such as difficulties inherent in performing such an expansion with a limited number of coefficients and the poor signal-to-noise ratio that affects Taylor coefficients determined from lattice calculations.

Leading hadronic contribution to the muon magnetic moment from lattice QCD.

The standard model of particle physics describes the vast majority of experiments and observations involving elementary particles. Any deviation from its predictions would be a sign of new, fundamental physics. One long-standing discrepancy concerns the anomalous magnetic moment of the muon, a measure of the magnetic field surrounding that particle. Standard-model predictions1 exhibit disagreement with measurements2 that is tightly scattered around 3.7 standard deviations. Today, theoretical and measurement errors are comparable; however, ongoing and planned experiments aim to reduce the measurement error by a factor of four. Theoretically, the dominant source of error is the leading-order hadronic vacuum polarization (LO-HVP) contribution. For the upcoming measurements, it is essential to evaluate the prediction for this contribution with independent methods and to reduce its uncertainties. The most precise, model-independent determinations so far rely on dispersive techniques, combined with measurements of the cross-section of electron-positron annihilation into hadrons3-6. To eliminate our reliance on these experiments, here we use ab initio quantum chromodynamics (QCD) and quantum electrodynamics simulations to compute the LO-HVP contribution. We reach sufficient precision to discriminate between the measurement of the anomalous magnetic moment of the muon and the predictions of dispersive methods. Our result favours the experimentally measured value over those obtained using the dispersion relation. Moreover, the methods used and developed in this work will enable further increased precision as more powerful computers become available.

Presynchronization using a modified Ovsynch protocol or a single gonadotropin-releasing hormone injection 7 d before an Ovsynch-56 protocol for submission of lactating dairy cows to first timed artificial insemination.

Presynchronization strategies, such as Presynch-Ovsynch and Double-Ovsynch, increase fertility to timed artificial insemination (TAI) compared with Ovsynch alone; however, simpler presynchronization strategies could reduce costs and simplify reproductive management. Lactating Holstein cows (n=601) were randomly assigned to 1 of 2 presynchronization treatments before beginning an Ovsynch-56 protocol (GnRH at 70 ± 3 DIM, PGF2α 7 d later, GnRH 56 h after PGF2α, and TAI 16 h later at 80 ± 3 DIM) for first TAI. Cows (n=306) in the first treatment (Double-Ovsynch; DO) were presynchronized using a modified Ovsynch protocol (GnRH at 53 ± 3 DIM, 7 d later PGF2α, and GnRH 3 d later) ending 7 d before the first GnRH injection (G1) of an Ovsynch-56 protocol. Cows (n=295) in the second treatment (GGPG) were presynchronized using a single injection of GnRH 7 d before G1 of an Ovsynch-56 protocol at 63 ± 3 DIM. Blood samples were collected at G1 and the PGF2α injections of the Ovsynch-56 protocol to determine progesterone (P4) concentrations. Pregnancy diagnosis was performed using ultrasonography 32 d after TAI, and pregnant cows were reexamined 46 and 70 d after TAI. Overall, DO cows had more pregnancies per artificial insemination (P/AI) compared with GGPG cows 32 d after TAI (53 vs. 43%). Overall, P/AI did not differ by parity (primiparous vs. multiparous), and pregnancy loss did not differ between treatments or parities. More DO cows had P4 in a medium range (>0.5 to <4 ng/mL) at G1 of the Ovsynch-56 protocol compared with GGPG cows (82 vs. 50%), and more DO cows had high P4 (>4 ng/mL) at the PGF2α injection of the Ovsynch-56 protocol compared with GGPG cows (67 vs. 36%). Thus, presynchronization with a modified Ovsynch protocol increased P/AI after TAI at first AI by increasing synchrony to the Ovsynch-56 protocol compared with presynchronization using a single injection of GnRH.

Relationships between fertility and postpartum changes in body condition and body weight in lactating dairy cows.

The relationship between energy status and fertility in dairy cattle was retrospectively analyzed by comparing fertility with body condition score (BCS) near artificial insemination (AI; experiment 1), early postpartum changes in BCS (experiment 2), and postpartum changes in body weight (BW; experiment 3). To reduce the effect of cyclicity status, all cows were synchronized with Double-Ovsynch protocol before timed AI. In experiment 1, BCS of lactating dairy cows (n = 1,103) was evaluated near AI. Most cows (93%) were cycling at initiation of the breeding Ovsynch protocol (first GnRH injection). A lower percentage pregnant to AI (P/AI) was found in cows with lower (≤ 2.50) versus higher (≥ 2.75) BCS (40.4 vs. 49.2%). In experiment 2, lactating dairy cows on 2 commercial dairies (n = 1,887) were divided by BCS change from calving until the third week postpartum. Overall, P/AI at 70-d pregnancy diagnosis differed dramatically by BCS change and was least for cows that lost BCS, intermediate for cows that maintained BCS, and greatest for cows that gained BCS [22.8% (180/789), 36.0% (243/675), and 78.3% (331/423), respectively]. Surprisingly, a difference existed between farms with BCS change dramatically affecting P/AI on one farm and no effect on the other farm. In experiment 3, lactating dairy cows (n = 71) had BW measured weekly from the first to ninth week postpartum and then had superovulation induced using a modified Double-Ovsynch protocol. Cows were divided into quartiles (Q) by percentage of BW change (Q1 = least change; Q4 = most change) from calving until the third week postpartum. No effect was detected of quartile on number of ovulations, total embryos collected, or percentage of oocytes that were fertilized; however, the percentage of fertilized oocytes that were transferable embryos was greater for cows in Q1, Q2, and Q3 than Q4 (83.8, 75.2, 82.6, and 53.2%, respectively). In addition, percentage of degenerated embryos was least for cows in Q1, Q2, and Q3 and greatest for Q4 (9.6, 14.5, 12.6, and 35.2% respectively). In conclusion, for cows synchronized with a Double-Ovsynch protocol, an effect of low BCS (≤ 2.50) near AI on fertility was detected, but change in BCS during the first 3 wk postpartum had a more profound effect on P/AI to first timed AI. This effect could be partially explained by the reduction in embryo quality and increase in degenerate embryos byd 7 after AI in cows that lost more BW from the first to third week postpartum.

Effects of acute feed restriction combined with targeted use of increasing luteinizing hormone content of follicle-stimulating hormone preparations on ovarian superstimulation, fertilization, and embryo quality in lactating dairy cows.

Multiple metabolic and hormonal factors can affect the success of protocols for ovarian superstimulation. In this study, the effect of acute feed restriction and increased LH content in the superstimulatory FSH preparation on numbers of ovulations, fertilization, and embryo quality in lactating dairy cows was evaluated. Two experiments were performed using a Latin square design with treatments arranged as a 2 × 2 factorial: feed restriction (FR; 25% reduction in dry matter intake) compared with ad libitum (AL) feeding, combined with high (H) versus low (L) LH in the last 4 injections of the superstimulatory protocol. As expected, FR decreased circulating insulin concentrations (26.7 vs. 46.0 µU/mL). Two analyses were performed: one that evaluated the complete Latin square in experiment 2 and a second that evaluated only the first periods of experiments 1 and 2. For both analyses, follicle numbers, ovulation rates, and corpora lutea on d 7 were not different. In the first period analysis of experiments 1 and 2, we observed an interaction between feed allowance and amount of LH on fertilization rates, percentage of embryos or oocytes that were quality 1 and 2 embryos, and number of embryos or oocytes that were degenerate. Fertilization rates were greater for the AL-L (89.4%) and FR-H (80.1%) treatments compared with the AL-H (47.9%) and FR-L (59.9%) treatments. Similarly, the proportion of total embryos or oocytes designated as quality 1 and 2 embryos was greater for AL-L (76.7%) and FR-H (73.4%) treatments compared with AL-H (35.6%) and FR-L (47.3%) treatments. In addition, the number of degenerate embryos was decreased for AL-L (1.3) and FR-H (0.4) treatments compared with the AL-H (2.6) and FR-L (2.3) treatments. Thus, cows with either too low (FR-L) or too high (AL-H) insulin and LH stimulation had lesser embryo production after superstimulation because of reduced fertilization rate and increased percentage of degenerate embryos. Therefore, interaction of the gonadotropin content of the superstimulatory preparation with the nutritional program of the donor cow needs to be considered to optimize success of ovarian superstimulatory protocols.

Effect of feed restriction on reproductive and metabolic hormones in dairy cows.

The objective of this trial was to evaluate the effects of feed restriction (FR) on serum glucose, nonesterified fatty acids, progesterone (P4), insulin, and milk production in dairy cows. Eight multiparous Holstein cows, 114 ± 14 d pregnant and 685 ± 39 kg of body weight, were randomly assigned to a replicated 4 × 4 Latin square design with 14-d periods. During the first 8 d of each period, cows in all treatments were fed for ad libitum feed intake. Beginning on d 9 of each period, cows received 1 of 4 treatments: ad libitum (AL), 25% feed restriction (25 FR), 50% feed restriction (50 FR), and 50% of TMR replaced with wheat straw (50 ST). Daily feed allowance was divided into 3 equal portions allocated every 8h with jugular blood samples collected immediately before each feeding through d 14. In addition, on d 12 of each period, blood samples were collected before and at 60, 120, 180, 240, 300, 360, 420, and 480 min after morning feeding. The conventional total mixed ration and total mixed ration with straw averaged 15.1 and 10.8%, 32.1 and 50.5%, and 26.8 and 17.0% for concentrations of crude protein, neutral detergent fiber, and starch, respectively. Cows that were feed and energy restricted had reduced dry matter intake, net energy for lactation intake, circulating glucose concentrations, and milk production, but greater body weight and body condition score losses than AL cows. Circulating concentrations of insulin were lower for cows fed 50 FR (8.27 µIU/mL) and 50 ST (6.24 µIU/mL) compared with cows fed AL (16.65 µIU/mL) and 25 FR (11.16 µIU/mL). Furthermore, the greatest plasma nonesterified fatty acids concentration was observed for 50 ST (647.7 µ Eq/L), followed by 50 FR (357.5 µEq/L), 25 FR (225.3 µEq/L), and AL (156.3 µEq/L). In addition, serum P4 concentration was lower for cows fed AL than cows fed 50 ST and 25 FR. Thus, FR reduced circulating glucose and insulin but increased P4 concentration, changes that may be positive in reproductive management programs.

Effects of deep-horn AI on fertilization and embryo production in superovulated cows and heifers.

The primary objective of this study was to determine the effect of site of semen deposition on fertilization rate and embryo quality in superovulated cows. The hypothesis was that deposition of semen into the uterine horns would increase the fertilization rate compared with deposition of semen into the uterine body. The secondary objective was to evaluate the effect of uterine environment on fertilization rate and embryo quality. It was hypothesized that subclinical endometritis at the onset of superstimulation would decrease the fertilization rates and embryo quality. In experiment 1, 17 superovulated heifers were randomly assigned to receive artificial insemination (AI) into the uterine body or uterine horns. The total number of fertilized structures and fertilization rate from superovulated heifers was increased (P = 0.04 and P = 0.02, respectively) when semen was deposited into the uterine horns compared with the uterine body. Other embryo characteristics did not differ based on the site of semen deposition. In experiment 2, 14 lactating dairy cows were superovulated twice and were randomly assigned to receive AI into the uterine body or deep into the uterine horns using a crossover design. Neither fertilization rate nor any other embryo characteristics were improved when semen was placed deep into the uterine horns compared with the uterine body. In experiment 3, 72 superovulated lactating dairy cows were randomly assigned to receive AI into the uterine body or uterine horns. Before initiation of superstimulatory treatments, an endometrial cytology sample was collected from each cow. Ova/embryos were collected by a nonsurgical technique at 70 ± 3 days in milk. Similar to experiment 2, neither fertilization rate nor any other embryo characteristics differed based on the site of semen deposition in experiment 3. The percentage of cows with subclinical endometritis did not differ between treatments. Interestingly, there was a tendency (P = 0.09) for a reduction in embryo recovery rate and a reduction (P = 0.01) in the fertilization rate for cows with subclinical endometritis. In conclusion, deposition of semen into the uterine horns rather than into the uterine body did not improve the fertilization rate or embryo quality in superovulated cows. Subclinical endometritis decreased the fertilization rate in superovulated cows.

Effect of timing of initiation of resynchronization and presynchronization with gonadotropin-releasing hormone on fertility of resynchronized inseminations in lactating dairy cows.

Lactating Holstein cows (n=1,456) were randomized in a 2×2 factorial design to compare the main effects of day of initiation of resynchronization after artificial insemination (AI; 32 vs. 39 d) and presynchronization with GnRH 7d before initiation of resynchronization on fertility to timed AI (TAI). This design resulted in the following 4 resynchronization treatments: (1) resynchronization (GnRH treatment, PGF2α treatment 7d later, GnRH treatment 56 h later, and TAI 16 h later), initiated 32 ± 3 d after AI; (2) presynchronization with 100 µg of GnRH 25 ± 3 d after AI and resynchronization initiated 32 ± 3 d after AI at nonpregnancy diagnosis; (3) resynchronization initiated 39 ± 3 d after AI (GPG39); and (4) presynchronization with 100 µg of GnRH 32 ± 3 d after AI at nonpregnancy diagnosis and resynchronization initiated 39 ± 3 d after AI. Overall, 344 cows were inseminated at estrus between enrollment (25 ± 3 d after AI) and TAI of the resynchronization treatments, and 1,112 cows received TAI. Progesterone (P4) was analyzed in blood samples collected from all cows at the first GnRH injection of the resynchronization protocols (G1), and ovarian structures were evaluated and blood samples were collected at G1, at the PGF2α injection, and at the TAI of the resynchronization protocols in a subgroup of cows (n=417). When analyzed as main effects, cows presynchronized with GnRH had more pregnancies per AI (P/AI) than nonpresynchronized cows (38.9 vs. 33.8%), whereas timing of initiation of resynchronization did not affect P/AI. Although cows with high P4 at G1 had greater P/AI than cows with low P4 (38.7 vs. 31.8%), presynchronization with GnRH did not increase the proportion of cows with high P4 (>1.0 ng/mL) at G1 but moved cows from a low-P4 environment to an intermediate-P4 level. Presynchronization with GnRH also decreased the percentage of cows with low P4 at the PGF2α injection, thereby increasing synchrony to the protocol. Cows with high P4 at G1 had a decreased ovulatory response to G1 compared with cows with low P4 (40.9 vs. 69.1%), and cows that ovulated to G1 had decreased luteal regression after PGF2α compared with cows that did not ovulate (78.5 vs. 87.3%). We conclude that presynchronization with GnRH 7d before initiation of resynchronization increased fertility in dairy cows, whereas timing of initiation of resynchronization did not.

Effect of treatment with human chorionic gonadotropin on day 5 after timed artificial insemination on fertility of lactating dairy cows.

Reproductive management programs that synchronize ovulation can ovulate a smaller than normal follicle, potentially resulting in inadequate progesterone (P4) concentrations after artificial insemination (AI). Ovulation of the dominant follicle of the first follicular wave with human chorionic gonadotropin (hCG) treatment can produce an accessory corpus luteum and increase circulating P4 concentrations. This manuscript reports the results of 2 separate analyses that evaluated the effect of hCG treatment post-AI on fertility in lactating dairy cows. The first study used meta-analysis to combine the results from 10 different published studies that used hCG treatment on d 4 to 9 post-AI in lactating dairy cows. Overall, pregnancies per artificial insemination (P/AI) were increased 3.0% by hCG treatment post-AI [34% (752/2,213) vs. 37% (808/2,184); Control vs. hCG-treated, respectively]. The second study was a field research trial in which lactating Holstein cows (n=2,979) from 6 commercial dairy herds were stratified by parity and breeding number and then randomly assigned to one of 2 groups: control (no further treatment, n=1,519) or hCG [Chorulon i.m.: 2,000 IU (in 3 of the herds) or 3,300 IU (in 3 herds); n=1,460] on d 5 after a timed AI (ovulation synchronized with Ovsynch, Presynch-Ovsynch, or Double-Ovsynch). In a subset of cows, the hCG profile and P4 changes were determined. Treatment with hCG increased P4 (4.3 vs. 5.3 ng/mL on d 12). Pregnancies per AI were greater in cows treated with hCG (40.8%; 596/1,460) than control (37.3%; 566/1,519) cows. Interestingly, an interaction among treatment and parity was observed; primiparous cows had greater P/AI after hCG (49.7%; 266/535) than controls (39.5%; 215/544). In contrast, older cows receiving hCG (35.7%; 330/925) had similar P/AI to controls (36.0%; 351/975).Thus, targeted use of hCG on d 5 after TAI enhances fertility about 3.0% (based on meta-analysis) to 3.5% (based on our field trial). Surprisingly, this fertility-enhancing effect of hCG was very large in first-lactation cows but not observed in older cows in the field study. Future research is needed to confirm these intriguing results and to determine why older cows did not have improved fertility after hCG treatment.

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.

Presynchronization with Double-Ovsynch improves fertility at first postpartum artificial insemination in lactating dairy cows.

The objective of this study was to compare circulating progesterone (P4) profiles and pregnancies per AI (P/AI) in lactating dairy cows bred by timed artificial insemination (TAI) following Ovsynch-56 after 2 different presynchronization protocols: Double-Ovsynch (DO) or Presynch-Ovsynch (PS). Our main hypothesis was that DO would increase fertility in primiparous cows, but not in multiparous cows. Within each herd (n=3), lactating dairy cows (n=1,687; 778 primiparous, 909 multiparous) were randomly assigned to DO [n=837; GnRH-7d-PGF(2α)-3d-GnRH-7d-Ovsynch-56 (GnRH-7d-PGF(2α)-56h-GnRH-16hTAI)] or PS (n=850; PGF(2α)-14d-PGF(2α)-12d-Ovsynch-56). In 1 herd, concentrations of P4 were determined at the first GnRH (GnRH1) of Ovsynch-56 and at d 11 after TAI (n=739). In all herds, pregnancy was diagnosed by palpation per rectum at 39 d. In 1 herd, the incidence of late embryo loss was determined at 74d, and data were available on P/AI at the subsequent second service. Presynchronization with DO reduced the percentage of animals with low P4 concentrations (<0.50 ng/mL) at GnRH1 of Ovsynch-56 (5.4 vs. 25.3%, DO vs. PS). A lesser percentage of both primiparous and multiparous cows treated with DO had low P4 concentrations at GnRH1 of Ovsynch-56 (3.3 vs. 19.7%, DO vs. PS primiparous; and 8.8 vs. 31.9%, DO vs. PS multiparous). Presynchronization with DO improved P/AI at the first postpartum service (46.3 vs. 38.2%, DO vs. PS). Statistically, a fertility improvement could be detected for primiparous cows treated with DO (52.5 vs. 42.3%, DO vs. PS, primiparous), but only a tendency could be detected in multiparous cows (40.3 vs. 34.3%, DO vs. PS, multiparous), consistent with our original hypothesis. Presynchronization treatment had no effect on the incidence of late embryo loss after first service (8.5 vs. 5.5%, DO vs. PS). A lower body condition score increased the percentage of cows with low P4 at GnRH1 of Ovsynch-56 and reduced fertility to the TAI. In addition, P4 concentration at d 11 after TAI was reduced by DO. The method of presynchronization at first service had no effect on P/AI at the subsequent second service (34.7 vs. 36.5%, DO vs. PS). Thus, presynchronization with DO induced cyclicity in most anovular cows and improved fertility compared with PS, suggesting that DO could be a useful reproductive management protocol for synchronizing first service in commercial dairy herds.

Effect of presynchronization with human chorionic gonadotropin or gonadotropin-releasing hormone 7 days before resynchronization of ovulation on fertility in lactating dairy cows.

Our objectives were to (1) compare the effect on pregnancies per artificial insemination (P/AI) of presynchronization of the estrous cycle with human chorionic gonadotropin (hCG) 7d before resynchronization of ovulation (Resynch) initiated 25 d after timed artificial insemination (TAI) and compare the presynchronization treatment with the Double-Ovsynch (DO) protocol, and (2) evaluate whether hCG for presynchronization could be replaced with GnRH. In experiment 1, lactating Holstein cows were blocked by parity and were randomly assigned to receive (1) Resynch-25 (D25), the Resynch protocol (GnRH-7 d-PGF(2 α)-56 h-GnRH-16 h-TAI) initiated 25 d after TAI (n=418); (2) HGPG, presynchronization with hCG (2,000 IU of Chorulon) 7d before D25 (n=450); and (3) DO (Pre-Resynch, GnRH-7 d-PGF(2 α)-72 h-GnRH; Breeding-Resynch, GnRH-7 d-PGF(2 α)-56 h-GnRH-16 h-TAI) initiated 22d after TAI (n=405). At 29 d after TAI, cows in the HGPG (37.3%) and DO (35.8%) groups had more P/AI than did cows in the D25 group (28.0%), and cows in the HGPG and DO groups continued to have more P/AI than did cows in the D25 group at 53 d after TAI. Presynchronization with hCG induced ovulation in 76% of the cows, which increased the percentage of HGPG cows with a corpus luteum at the initiation of Resynch compared with cows in the D25 group. In experiment 2, the D25 (n=368) and HGPG (n=338) treatments described in experiment 1 were compared in addition to a third treatment (GGPG; n=351), in which the hCG injection 18 d after TAI was replaced with a GnRH injection (200 µg of gonadorelin). At 32 d after TAI, cows in the HGPG group had more P/AI than did cows in the D25 group (33.7 vs. 25.5%), whereas cows in the GGPG group had intermediate P/AI (31.6%). At 53 d after TAI, P/AI tended to be greater for cows in the HGPG group than for those in the D25 group, whereas P/AI for cows in the GGPG group did not differ from that for cows in the D25 group. Treatment with hCG and GnRH 18d after TAI induced ovulation in 58.8 and 48.2% of cows, respectively, but did not increase the percentage of cows with a corpus luteum at the initiation of Resynch. More cows in the HGPG and GGPG groups had their estrous cycles synchronized after the resynchronization protocols compared with cows in the D25 group. We conclude that presynchronization with hCG increased fertility by increasing synchronization to the Resynch protocol, whereas presynchronization with GnRH improved synchronization to the Resynch protocol but did not improve fertility when compared with no presynchronization or presynchronization with hCG.

Effect of progesterone on magnitude of the luteinizing hormone surge induced by two different doses of gonadotropin-releasing hormone in lactating dairy cows.

Ovulation to the first GnRH injection of Ovsynch-type protocols is lower in cows with high progesterone (P4) concentrations compared with cows with low P4 concentrations, suggesting that P4 may suppress the release of LH from the anterior pituitary after GnRH treatment. The objectives of this study were to determine the effect of 1) circulating P4 concentrations at the time of GnRH treatment on GnRH-induced LH secretion in lactating dairy cows and 2) increasing the dose of GnRH from 100 to 200 µg on LH secretion in a high- and low-P4 environment. A Double-Ovsynch (Pre-Ovsynch: GnRH, PGF(2α) 7d later, GnRH 3d later, and Breeding-Ovsynch 7d later: GnRH, PGF(2α) 7d later, and GnRH 48 h later) synchronization protocol was used to create the high- and low-P4 environments. At the first GnRH injection of Breeding-Ovsynch (high P4), all cows with a corpus luteum ≥ 20 mm were randomly assigned to receive 100 or 200 µg of GnRH. At the second GnRH injection of Breeding-Ovsynch (low P4) cows were again randomized to receive 100 or 200 µg of GnRH. Blood samples were collected every 15 min from -15 to 180 min after GnRH treatment, and then hourly until 6h after GnRH treatment. As expected, mean P4 concentrations were greater for cows in the high- than the low-P4 environment. For cows receiving 100 µg of GnRH, the LH peak and area under the curve (AUC) were greater in the low- than in the high-P4 environment. Similarly, for cows receiving 200 µg of GnRH, the LH peak and AUC were greater in the low- than the high-P4 environment. Cows receiving 100 or 200 µg of GnRH had greater mean LH concentration in the low- than the high-P4 environment from 1 to 6h after GnRH treatment. On the other hand, when comparing the effect of the 2 GnRH doses in the high- and low-P4 environments, cows receiving 200 µg of GnRH had a greater LH peak and AUC than cows treated with 100 µg of GnRH both in the high- and low-P4 environments. For the high-P4 environment, mean LH was greater from 1.5 to 5h after GnRH treatment for cows receiving 200 µg of GnRH than for those receiving 100 µg of GnRH. In the low-P4 environment, mean LH was greater for cows receiving 200 µg of GnRH than for those receiving 100 µg of GnRH from 1 to 2.5h after GnRH treatment. We conclude that the P4 environment at GnRH treatment dramatically affects GnRH-induced LH secretion, and that a 200-µg dose of GnRH can increase LH secretion in either a high- or a low-P4 environment.

Increased fertility in lactating dairy cows resynchronized with Double-Ovsynch compared with Ovsynch initiated 32 d after timed artificial insemination.

The objective was to determine if using a Double-Ovsynch protocol [DO; Pre-Resynch: GnRH-7 d-PGF(2α)-3 d-GnRH, 7 d later Breeding-Resynch: GnRH-7 d-PGF(2α)-56 h-GnRH-16 h-timed artificial insemination (TAI)] to resynchronize ovulation after a previous TAI would increase synchrony and pregnancies per AI (P/AI) compared with an Ovsynch protocol initiated 32 d after TAI (D32; GnRH-7 d-PGF(2α)-56 h-GnRH-16 h-TAI). Lactating Holstein cows at various days in milk and prior AI services were blocked by parity and randomly assigned to resynchronization treatments. All DO cows received the first GnRH injection of Pre-Resynch 22 d after TAI, and cows (n=981) diagnosed not pregnant using transrectal ultrasonography 29 d after TAI continued the protocol. Pregnancy status for all D32 cows was evaluated 29 d after TAI so fertility and pregnancy loss could be compared with that of DO cows. All D32 cows received the first GnRH injection of Ovsynch 32 d after TAI, and cows (n=956) diagnosed not pregnant using transrectal palpation 39 d after TAI continued the protocol. In a subgroup of cows from each treatment, ultrasonography (n=751) and serum progesterone (P4) concentrations (n=743) were used to determine the presence of a functional corpus luteum (CL) and ovulation to the first GnRH injection of D32 and Breeding-Resynch of DO (GnRH1), luteal regression after PGF before TAI, and ovulation to the GnRH injection before TAI (GnRH2). Overall, P/AI 29 d after TAI was not affected by parity and was greater for DO compared with D32 cows (39 vs. 30%). Pregnancy loss from 29 to 74 d after TAI was not affected by parity or treatment. The percentage of cows with a functional CL (P4 ≥1.0 ng/mL) at GnRH1 was greater for DO than D32 cows (81 vs. 58%), with most DO cows having medium P4 (60%; 1.0 to 3.49 ng/ml), whereas most D32 cows had either low (42%; <1.0 ng/mL) or high (36%; ≥3.5 ng/mL) P4 at GnRH1. Ovulation to GnRH1 was similar between treatments but was affected by serum P4 at GnRH. Cows with low P4 (<1.0 ng/mL) had the greatest ovulatory response (59%), followed by cows with medium (≥1.0 to 3.49 ng/mL; 38%) and then high (≥3.50 ng/mL; 16%) P4 at GnRH1. A greater percentage of DO cows were synchronized compared with D32 cows (72 vs. 51%) primarily due to a greater percentage of D32 than DO cows without a functional CL at the PGF injection before TAI (35 vs. 17%) or without complete CL regression before GnRH2 (17 vs. 7%). We conclude that DO increased fertility of lactating dairy cows during a resynchronization program primarily by increasing synchronization of cows during the Ovsynch protocol before TAI.

Changes in serum pregnancy-associated glycoprotein, pregnancy-specific protein B, and progesterone concentrations before and after induction of pregnancy loss in lactating dairy cows.

Lactating crossbred dairy cows were synchronized to receive a timed artificial insemination (TAI), and blood samples were collected from all cows from TAI until pregnancy diagnosis 39 d after TAI (period 1), and from pregnant cows from onset of treatment until the end of the experiment (period 2). Cows diagnosed pregnant 39 d after TAI were randomly assigned to 1 of 3 treatments to receive (1) an i.m. injection of saline (CON, n=10); (2) an i.m. injection of PGF(2α) (PGF, n=10); or (3) an intrauterine infusion of 120 mL of hypertonic saline (INF, n=9). During period 1, serum pregnancy-associated glycoprotein (PAG) concentrations began to increase in pregnant cows by 25 d after TAI and differed from those in nonpregnant cows by 27 d after TAI, whereas serum pregnancy-specific protein B (PSPB) concentrations in pregnant cows differed from those in nonpregnant cows by 22 d after TAI. During period 2, time from treatment to cessation of the embryonic heartbeat was greater for PGF than for INF cows (36.0±5.7 vs. 0.2±0.1 h, respectively), and time from treatment to conceptus disappearance was greater for INF than for PGF cows (7.1±3.3 vs. 1.9±0.3 d, respectively). Overall, progesterone concentration was greater for CON and INF than for PGF cows (8.7±2.8, 8.2±3.1, and 1.0±2.3 ng/mL, respectively) due to luteal regression for PGF cows and corpus luteum maintenance for CON and INF cows. Serum PAG and PSPB concentrations differed among CON cows and PGF and INF cows beginning 1 and 2.5 d after treatment for PAG and PSPB, respectively. By 9.5 d after treatment, PAG and PSPB concentrations were similar to those of nonpregnant cows. We conclude that although timing of conceptus expulsion occurred 5.2 d later for INF than for PGF cows, serum PAG and PSPB concentrations decreased at a similar rate from the onset of treatment for both models of pregnancy loss evaluated.

Managing the dominant follicle in lactating dairy cows.

Reproductive efficiency is not optimal in high-producing dairy cows. Although many aspects of ovarian follicular growth in cows are similar to those observed in heifers, there are numerous specific differences in follicular development that may be linked with changes in reproductive physiology in high-producing lactating dairy cows. These include: 1) reduced circulating estradiol (E2) concentrations near estrus, 2) ovulation of follicles that are larger than the optimal size, 3) increased double ovulation and twinning, and 4) increased incidence of anovulation with a distinctive pattern of follicle growth in anovular dairy cows. The first three changes become more dramatic as milk production increases, although anovulation has not generally been associated with level of milk production. To overcome reproductive inefficiencies in dairy cows, reproductive management programs have been developed to synchronize ovulation and enable the use of timed AI in lactating dairy cows. Effective regulation of the CL, follicles, and hormonal environment during each part of the protocol is critical for optimizing these programs. This review discusses the distinct aspects of follicular development in lactating dairy cows and the methodologies that have been utilized in the past two decades in order to manage the dominant follicle during synchronization of ovulation and timed AI programs.

Ultrasonographic evaluation of endometrial thickness near timed AI as a predictor of fertility in high-producing dairy cows.

The objectives were to evaluate changes in endometrial thickness (ET) near the time of a synchronized ovulation and to assess the relationship of ET and fertility in lactating Holstein cows, with or without estrogen supplementation near timed ovulation. In Experiment 1, eight cows were examined with transrectal ultrasonography, once daily for 5 d, starting concurrent with PGF(2α) (PGF) treatment during an Ovsynch protocol (GnRH - 7d - PGF - 72h - GnRH). The ET increased rapidly after PGF (from ∼7 to ∼9.5 mm), remained > 9 mm for the next 2 d, then decreased to ∼8 and 7.4 mm, 1 and 2 d, respectively, after the second GnRH. In Experiment 2,642 cows (total of 758 breedings) were subjected to an Ovsynch protocol (GnRH - 7d - PGF - 56h - GnRH - 16h - timed AI); cows received either no further treatment (Ovsynch) or 1 mg of estradiol-17ß im 8 h before the second GnRH (Ovsynch + E2). For both uterine horns, ET was measured (∼2 cm from the internal uterine body bifurcation) before E2 treatment (48 h after PGF). In cows with ET ≤ 8 mm vs > 8 mm, rates of ovulation were 86.0% (n = 136) vs 98.1% (n = 472; P < 0.01), respectively, and percentage pregnant per AI (P/AI) were 26.7% (n = 146) vs 42.7% (n = 524; P < 0.01). Treatment with E2 increased P/AI in cows with lower ET (Ovsynch + E2 = 37.0% vs Ovsynch = 23.3%; P = 0.07), but did not significantly improve P/AI in cows with ET > 8 mm (Ovsynch + E2 = 43.4% vs Ovsynch = 42.1%). In conclusion, a single ultrasonographic evaluation of ET in Holstein cows 48 h after PGF treatment in an Ovsynch program was a good predictor of ovulation failure and pregnancy success. Perhaps poor fertility in cows with reduced ET was low peripheral E2 concentrations near AI, poor P4 priming, or luteolysis failure during timed AI procedures.

Managing the dominant follicle in high-producing dairy cows.

Reduced reproductive efficiency has been reported in high-producing dairy cows. Sources of reproductive inefficiency include decreased expression of estrus, increased diameter of the ovulatory follicle and reduced fertility when cows are inseminated after estrus, increased incidence of double ovulation and twinning, and increased pregnancy loss. To overcome some of these inefficiencies, reproductive management programs have been developed that synchronize ovulation and enable effective timed artificial insemination (AI) of lactating dairy cows. Effective regulation of the corpus luteum (CL), follicles, and hormonal environment are critical for optimizing these programs. Recent programs, such as the 5-day CIDR program, Double-Ovsynch, G-6-G, and estradiol benzoate-CIDR programs were designed to more effectively control one or more physiological events. These events include synchronization of a new follicular wave at the beginning of the program, optimization of the circulating progesterone (P4) concentrations and duration of follicular dominance, optimized reductions in P4 and increases in circulating estradiol (E2) concentrations during the preovulatory period, and tightly synchronized ovulation of a follicle of optimal size and fertility for implementation of timed AI. The success of these programs has been remarkable, although there is substantial variability in effectiveness due to environmental, management, nutritional, genetic, and disease factors as well as potential variability in some aspects of reproductive physiology among commercial dairy farms. Future programs will optimize the reproductive physiology while simplifying the protocol implementation and also match specific reproductive management protocols to specific farms and even specific cows (for example primiparous vs. multiparous).

Effect of dry period length on reproduction during the subsequent lactation.

Days dry may influence reproductive measures such as days to first postpartum ovulation, days open, and pregnancy per artificial insemination (AI). Holstein cows (n = 781) from an approximately 3,000-cow commercial dairy operation were randomly assigned to 1 of 2 treatments with different targeted dry period (DP) lengths. Treatments were 1) a traditional DP of 55 d (T) or 2) a shortened DP of 34 d (S). All dry cows on T were fed a low-energy diet until 35 d before expected calving, and then at 34 d before expected calving, cows on T and S were fed a moderate energy diet until parturition. After parturition, all cows consumed the same diets that included a postcalving diet followed by a lactation diet. Actual days dry for each treatment were close to expected values, 34 and 56 d for S and T, respectively. Median days until first postpartum ovulation occurred sooner for S compared with T (35 vs. 43 d). The percentage of cows that were classified anovular by 70 d in milk (DIM) was more than 2-fold greater for cows on T than S (18 vs. 8%). Cows received AI after standing estrus starting at d 45, and the percentage of cows pregnant at 70 DIM tended to be greater for S than T; younger cows were similar (20.2 vs. 18.8%), but there was a difference between S and T in older cows (20.3 vs. 10.6%). Similarly, median days open tended to be fewer for cows on S than T. At 300 DIM, 85% of cows in both treatments were pregnant. Combining data from first and second service, pregnancies per AI were greater in older cows on S than T (32 vs. 24%). Thus, shortening the DP appeared to increase reproductive efficiency in older cows by shortening time to first ovulation, reducing numbers of anovular cows, and improving fertility. Future studies at more locations with varying reproductive management strategies are needed to confirm and provide the mechanistic basis for these results.

Comparison of gonadorelin products in lactating dairy cows: efficacy based on induction of ovulation of an accessory follicle and circulating luteinizing hormone profiles.

This study evaluated whether the four gonadorelin products that are commercially available in the United States produce comparable ovulation responses in lactating cows. Dairy cows at 7 d after last gonadotropin-releasing hormone (GnRH) treatment of Ovsynch (Day 7), with a corpus luteum (CL) > or =15 mm and at least one follicle > or =10mm, were evaluated for response to GnRH treatment. Selected cows were randomized to receive (100 microg; im): (1) Cystorelin (n=146); (2) Factrel (n=132); (3) Fertagyl (n=140); or (4) Ovacyst (n=140). On Day 14, cows were examined for ovulation by detection of an accessory CL. Circulating luteinizing hormone (LH) concentrations were also evaluated in some cows after treatment with 100 microg (n=10 per group) or 50 microg (n=5 per group) GnRH. Statistical analyses were performed with the procedures MIXED and GLIMMIX of the SAS program. Percentage of cows ovulating differed (P<0.01) among groups, with that for Factrel being lower (55.3%) than that for Cystorelin (76.7%), Fertagyl (73.6%), or Ovacyst (85.0%). There was no effect of batch, parity, or follicle size on ovulation response, but increasing body condition score decreased ovulation response. There was a much greater LH release in cows treated with 100 microg than in those treated with 50 microg, but there were no detectable differences among products in time to LH peak, peak LH concentration, or area under the LH curve and no treatment effects nor treatment by time interactions on circulating LH profile. Thus, ovulation response to Factrel on Day 7 of the cycle was lower than that for other commercial GnRH products, although a definitive mechanism for this difference between products was not demonstrated.