A shortened resynchronization treatment for dairy cows after a nonpregnancy diagnosis

Effect of 200 µg of gonadorelin at the first gonadotropin-releasing hormone of the Resynch-25 on ovarian dynamics and fertility in lactating Holstein cows

Our objective was to determine the effect of a 200-µg dose of GnRH 25 d after previous artificial insemination (AI) in a Resynch-25 resynchronization program on ovulatory response, circulating progesterone (P4) concentrations before and after treatment, and pregnancy per AI (P/AI) compared with a 100-µg dose in lactating Holstein cows. Experimental d 0 was considered the day of the previous AI. Lactating dairy cows (n = 3,240) with an average of 126 d in milk (DIM) and between 1 and 6 services were randomly assigned to receive 100 µg or 200 µg of GnRH on d 25 (GnRH25). On d 32 after AI, cows diagnosed nonpregnant with the presence of a corpus luteum (CL) detected by ultrasound (n = 1,249) received PGF2α treatments on d 32 and 33, followed by a GnRH 32 h later and AI 16 h after this last GnRH. Blood samples were collected on d 25, 32, and 34 to evaluate serum P4 concentrations. Transrectal ultrasonographic examination was performed on d 25 and 27 to assess ovulatory response to GnRH25. Cows were checked for pregnancy on d 32, 46, and 88 after AI. The larger dose of GnRH increased the overall proportion of cows that ovulated to the GnRH25 (25.0% for the 100-µg dose vs. 32.5% for the 200-µg dose). However, when cows were evaluated separately according to the pregnancy status on d 32 after AI, we found no treatment effect within cows pregnant and nonpregnant. Even though treatment increased the proportion of cows with serum P4 ≤0.42 ng/mL at the last GnRH treatment (G2; 86.2% for the 100-µg dose vs. 93.0% for the 200-µg dose), it did not affect P/AI on d 32, 46, and 88. Furthermore, a greater proportion of cows without a functional CL at GnRH25 had circulating P4 concentrations ≥1.00 ng/mL on d 32 and lower than 0.42 ng/mL on G2. These cows also had a greater P/AI on d 32, 46, and 88. In summary, the larger dose of GnRH on d 25 after AI did not increase the ovulatory response in nonpregnant cows and P/AI on d 32, 46, and 88 after AI after the Resynch-25 program. Additionally, nonpregnant cows without a functional CL at GnRH25 were better synchronized after the Resynch-25 protocol and had greater P/AI on d 32, 46, and 88 after timed-AI.

Comparison of the Evaluation of Combination of Ultrasonography of the Reproductive Tract With Hormone Administration on Dairy Cow Fertility

Further optimization of reproduction management programs in dairy cows is a contemporary research topic. In this context, our study aimed to compare a hormone program, named “uterus-ovary monitoring and classified use of hormone program” (M+C), with the Pre-OvSynch program. The M+C was based on regular application of B-mode ultrasonography during a voluntary waiting period to monitor the uterus and ovaries, while using various treatments under different conditions. Results of the 30–33-day and 60-day pregnancy/artificial insemination after the first AI of M+C were significantly better than the Pre-OvSynch (p < 0.05). The pregnancy rates within 180 days in milk after M+C was significantly higher than that after Pre-OvSynch (p < 0.05). The total number of inseminations used for M+C was significantly lower than that for Pre-OvSynch (p < 0.01). The number of open days was fewer after M+C than after the Pre–OvSynch throughout the experimental period with highly significant differences (p < 0.01). In summary, the use of M+C enhances reproductive benefits and reduces the need for hormone drugs among cows.

Selective use of a modified pre-synchronization-Ovsynch and resynchronization reproductive strategy in dairy herds: A field application study

We aimed to evaluate whether a modified pre-synchronization-Ovsynch (MPO) and resynchronization method, adjusted for the timing of biweekly reproductive consulting visits, could be implemented successfully under field conditions in dairy herds. Forty-five days after calving (calving: Day 0), 1,182 cows were assigned randomly to Ovsynch, MPO or control groups. (1) Cows were administered GnRH on Day 65, PGF_2α on Day 72 and GnRH 56 hr later, followed by timed artificial insemination (TAI) 16 hr later (Ovsynch, n = 380). (2) Cows with a CL were administered PGF_2α (n = 204) and cows without were administered GnRH (n = 199) on Day 45. Then, each cow was administered PGF_2α on Day 55 (9 to 12 days later), GnRH on Day 58 and underwent Ovsynch 7 days later (selective MPO [sMPO] n = 403). (3) The remaining cows underwent AI when oestrus was detected (EDAI, n = 399). The probabilities of pregnancy per AI 30 and 45 days after the first AI were higher in the sMPO group (odds ratios 1.99 and 1.92, p < .0001) than in the EDAI group. In addition, the probability of pregnancy by 105 days postpartum tended to be higher (p < .1) in the sMPO group than in the EDAI and Ovsynch groups, which shortened the mean interval from calving to pregnancy in the sMPO group (3.4 and 4.2 days, respectively) than in the EDAI and Ovsynch groups. In the sMPO group, the interval between the first and second treatments during pre-synchronization did not affect the probability of pregnancy per AI after the first AI. The probability of pregnancy per AI after the second AI did not differ between the Ovsynch, sMPO and EDAI groups. In conclusion, the sMPO programme, adjusted for the timing of biweekly reproductive consulting visits, followed by resynchronization, could be successfully adopted in field conditions, and is associated with good reproductive performance in dairy herds.

Resynchronizing the first eligible estrus in dairy cattle after a prior insemination and fertility of the prior insemination after gonadotropin-releasing hormone and progesterone treatments

The hypothesis of this study tested whether application of designed treatments to synchronize estrus in nonpregnant previously inseminated lactating dairy cows increased the proportion of nonpregnant cows in estrus before early pregnancy diagnosis on Day 32 after the previous insemination (Day 0) and increase fertility of the pretreatment insemination. A progesterone insert (CIDR) and GnRH were applied to cows after insemination to resynchronize the returning estrus of cows that failed to conceive on Day 0. The combination of GnRH (Day 14) and a CIDR insert (d 17 through 24) in experiment 1 (n = 347 cows) did not increase (P = 0.13) the proportion of nonpregnant cows returning to estrus before pregnancy diagnosis, but increased (P < 0.01) the synchrony of their return by 24.4% points, and delayed (P < 0.01) that return by 2.3 ± 0.3 d compared with controls. Ovulation risk after GnRH treatment on Day 14 was only 10%. For cows that failed to return to estrus before Day 32, progesterone concentration on Days 14 and 17 were less than that in cows that returned to estrus by Day 32 and in pregnant cows. Cows that returned to estrus had larger follicles and fewer numbers of CL on Day 21 than pregnant cows and cows that failed to return to estrus, but concentrations of pregnancy-associated glycoproteins on Day 28 indicated that cows failing to return to estrus were likely pregnant but suffered embryo death. In experiment 2 (n = 881), use of GnRH alone (Day 7), a CIDR insert alone (Days 14 through 21), or in combination, failed to increase the proportion of nonpregnant cows in estrus before pregnancy diagnosis on Day 32 compared with controls. Cows receiving the CIDR insert had increased (P < 0.01) synchrony of estrus by 24-34% points compared with cows that did not receive a CIDR insert. More cows receiving GnRH had 2 or more CL on Days 14 and 21 compared with controls. Ovulation risk after GnRH on Day 7 was greater than 66%. In both experiments combined, treatments with GnRH or GnRH + CIDR insert increased (P = 0.015) pretreatment pregnancy per AI by 7.1% points, but did not affect pregnancy loss. Although administering GnRH with or without a CIDR insert synchronized returns to estrus, treatments failed to increase the proportion of nonpregnant cows reinseminated before pregnancy diagnosis, but increased pretreatment pregnancy risk.

Factors That Optimize Reproductive Efficiency in Dairy Herds with an Emphasis on Timed Artificial Insemination Programs

Simple Summary

Reproductive efficiency is critical for profitability of dairy operations. The first part of this manuscript discusses the key physiology of dairy cows and how to practically manipulate this reproductive physiology to produce timed artificial insemination (TAI) programs with enhanced fertility. In addition, there are other critical factors that also influence reproductive efficiency of dairy herds such as genetics, management of the transition period, and body condition score changes and improve management and facilities to increase cow comfort and reduce health problems. Using optimized TAI protocols combined with enhancing cow/management factors that impact reproductive efficiency generates dairy herd programs with high reproductive efficiency, while improving health and productivity of the herds.

Abstract

Reproductive efficiency is closely tied to the profitability of dairy herds, and therefore successful dairy operations seek to achieve high 21-day pregnancy rates in order to reduce the calving interval and days in milk of the herd. There are various factors that impact reproductive performance, including the specific reproductive management program, body condition score loss and nutritional management, genetics of the cows, and the cow comfort provided by the facilities and management programs. To achieve high 21-day pregnancy rates, the service rate and pregnancy per artificial insemination (P/AI) should be increased. Currently, there are adjustments in timed artificial insemination (TAI) protocols and use of presynchronization programs that can increase P/AI, even to the point that fertility is higher with some TAI programs as compared with AI after standing estrus. Implementation of a systematic reproductive management program that utilizes efficient TAI programs with optimized management strategies can produce high reproductive indexes combined with healthy cows having high milk production termed “the high fertility cycle”. The scientific results that underlie these concepts are presented in this manuscript along with how these ideas can be practically implemented to improve reproductive efficiency on commercial dairy operations.

Effect of dose and timing of prostaglandin F2α treatments during a 7-d Ovsynch protocol on progesterone concentration at the end of the protocol and pregnancy outcomes in lactating Holstein cows

The objective of this study was to evaluate the effect of two prostaglandin F_2α (PGF) treatments 24 h apart (500 μg of cloprostenol) and treatment with a double PGF dose on d 7 (1000 μg of cloprostenol) during a 7-d Ovsynch protocol on progesterone (P4) concentration and pregnancy per artificial insemination (P/AI) in lactating Holstein cows. We hypothesized that treatment leads to a decreased P4 concentration at the second GnRH treatment (G2) and an increase in P/AI compared to the traditional 7-d Ovsynch protocol. A secondary hypothesis was that the treatment effect is influenced by the presence of a corpus luteum (CL) at the first GnRH treatment (G1). Two experiments were conducted on 8 commercial dairy farms in Germany. Once a week, cows from both experiments were assigned in a consecutive manner to receive: (1) Ovsynch (control: GnRH; 7 d, PGF; 9 d, GnRH), (2) Ovsynch with a double PGF dose (GDPG: GnRH; 7 d, 2xPGF; 9 d, GnRH), or (3) Ovsynch with a second PGF treatment 24 h later (GPPG: GnRH; 7 d, PGF; 8 d, PGF; 32 h, GnRH). All cows received timed AI (TAI) approximately 16 h after G2. Pregnancy diagnosis was performed by transrectal palpation (38 ± 3 d after TAI, experiment 1) or transrectal ultrasonography (35 ± 7 d after TAI, experiment 2). Whereas farms from experiment 1 used a Presynch-Ovsynch protocol (PGF, 14 d later PGF, 12 d later GnRH, 7 d later PGF, 2 d later GnRH, and 16-18 h later TAI) to facilitate first postpartum TAI, no presynchronization protocol was used on farms from experiment 2. In experiment 1, we enrolled 1581 lactating dairy cows (60 experimental units) from 2 dairy farms. At G2, blood samples were collected from a subsample of cows (n = 491; 16 experimental units) to determine P4 concentration at G2. In experiment 2, we enrolled 1979 lactating dairy cows (252 experimental units) from 6 dairy farms. Transrectal ultrasonography was performed to determine the presence or absence of a CL at G1. In experiment 1, treatment affected P/AI (P = 0.01) and P/AI was greater for GDPG (38.2%) and GPPG (38.9%) than for control cows (29.8%). Both, GDPG and GPPG cows had decreased P4 concentration at G2 compared with control cows (P < 0.01). Whereas both treatments increased the percentage of cows with very low P4 concentration (0.00-0.09 ng/mL) at G2, only the GPPG treatment decreased the percentage of cows with high P4 concentration (≥0.6 ng/mL) at G2 compared to the control group. In experiment 2, P/AI was greater for GPPG (37.4%) than for control cows (31.0%; P = 0.03) and tended to be greater than for GDPG cows (31.8%; P = 0.05). Cows from the GDPG group had similar (P = 0.77) P/AI compared to the control group. Pregnancy per AI did not differ between cows with a CL at G1 and cows without a CL at G1 (34.1% vs. 32.6%; P = 0.50). There was no interaction between treatment and presence of a CL at G1 on P/AI (P = 0.61). Combining data from the 2 experiments but excluding cows from experiment 1 receiving presynchronization before first TAI (n = 2573; 312 experimental units), P/AI was greater for GPPG (40.3%; P < 0.01) than for control (31.8%) and GDPG cows (33.4%). Between GDPG and control cows, P/AI did not differ (P = 0.46). We conclude that overall the addition of a second PGF treatment on d 8 during a 7-d Ovsynch protocol increased P/AI compared to the traditional 7-d Ovsynch including a single PGF dose on d 7 and to a double PGF dose on d 7. Doubling the PGF dose on d 7 in a 7-d Ovsynch protocol did not affect P/AI. Use of a presynchronization protocol, however, seems to influence the effect of a dose frequency modification of PGF treatment in an Ovsynch protocol. Presynchronized cows receiving first postpartum TAI had similarly increased P/AI treated with a double PGF dose compared with treatment with a second PGF dose. Future studies need to elucidate whether the treatment effect is modified by presynchronization of the first postpartum TAI.

A lateral flow-based portable platform for determination of reproductive status of cattle

Our objective was to develop and validate a tool integrating a disposable fluorescence-based lateral flow immunoassay (LFIA) coupled with a portable imaging device for estimating circulating plasma concentrations of progesterone (P4). First, we developed and optimized a competitive LFIA test strip to measure P4 in bovine plasma. The LFIA design included a sample pad, a conjugate pad that stores R-phycoerythrin-anti-P4 conjugates, a glass-fiber spacer pad, a nitrocellulose membrane with printed test and control lines, and a cellulose-fiber absorbent pad. To perform a test, 20 µL of plasma and 50 µL of running buffer were added on the sample pad. After 3 min, 45 µL of running buffer was added to initiate sample flow. After allowing 15 min to stabilize the colorimetric signal, strips were introduced in an LFIA portable reader wirelessly linked to a laptop to determine P4 concentration based on test-to-control-line signal (T/C ratio). In a series of experiments (n = 6), the ability of the LFIA to differentiate plasma samples with ≥1 or <1 ng/mL of P4 was evaluated. For each experiment, a calibration curve was constructed using plasma with known concentrations of P4 (0.1 to 3.7 ng/mL; n = 5). The resulting linear equation was then used to determine a T/C ratio cutoff to differentiate samples with ≥1 or <1 ng/mL of P4. In addition, to evaluate the ability of the platform to assign samples to P4 concentration groups without a calibration curve for individual batches, we performed a receiver operating characteristic analysis to identify a single cutoff value for T/C ratio that could potentially be used for all batches. Overall, calibration curves showed a linear relationship between T/C ratio and P4 levels (mean coefficient of determination = 0.74; range 0.42 to 0.99). Next, plasma samples from lactating dairy cows (n = 58) were tested in triplicate to determine the ability of the LFIA system to differentiate plasma samples with ≥1 or <1 ng/mL of P4 using a RIA for P4 as reference test. Overall, the LFIA assay correctly classified 90% of the samples, with 97% sensitivity, 83% specificity, 85% positive predictive value, and 96% negative predictive value. Agreement between the tests was substantial (kappa = 0.79; 95% confidence interval 0.64 to 0.95). When using a single cutoff value for T/C ratio selected by receiver operating characteristic analysis, sensitivity and specificity to determine CL presence were 97 (95% confidence interval 82 to 99) and 79% (95% confidence interval 60 to 92), respectively. These data suggest that the developed portable LFIA system can accurately differentiate plasma samples with ≥1 or <1 ng/mL of P4.