Double-Ovsynch Protocol Research Articles

Delaying induction of ovulation and timed AI in a Double-Ovsynch protocol increased expression of estrus and altered first service reproductive outcomes of lactating dairy cows

The objective of this randomized controlled experiment was to evaluate the effect of delaying induction of ovulation and timed artificial insemination (TAI) on expression of estrus before AI and first service reproductive outcomes. A secondary objective was to evaluate the effects of delaying induction of ovulation in a Double-Ovsynch protocol on ovarian function. Lactating Holstein cows (n = 4,672) from 2 commercial dairy farms fitted with sensors for automated detection of estrus were synchronized with a Double-Ovsynch protocol up to the first PGF2α (PGF-L) of the Breeding-Ovsynch portion of the protocol (Pre-Ovsynch: GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later Breeding-Ovsynch: GnRH, 7 d later PGF2α, 1 d later PGF2α). At PGF-L, cows blocked by parity (primiparous vs. multiparous) and semen used for first service (sex-sorted dairy vs. conventional beef) were randomly assigned to the G56 (n = 2,338) or G80 (n = 2,334) treatments. Cows in G56 had 56 h whereas cows in G80 had 80 h from PGF-L to induction of ovulation with the last GnRH (GnRH2) before AI. For both treatments, TAI occurred ∼16 h after GnRH2. All cows with automated estrus alerts between PGF-L and TAI were inseminated at detected estrus (AIE) without GnRH. Ovarian function and responses to synchronization were monitored based on circulating concentrations of progesterone and examination of the ovaries by ultrasonography. Data for binary outcomes were analyzed by logistic and continuous outcomes with lineal regression. More cows in G80 received AIE and had estrus before AI. Overall, pregnancies per AI (P/AI) did not differ for the G80 and G56 treatments. Cows in G80 that received TAI and had no estrus had fewer P/AI than cows with estrus that received AIE or TAI in G80, and fewer P/AI than cows AIE and cows that received TAI and had or did not have estrus in the G56 treatment. No differences were observed between treatments or for cows with and without estrus for pregnancy loss. Unlike some minor differences between treatments for concentrations of progesterone at GnRH2, the most notable differences in ovarian function were for cows in both treatments with or without estrus that received TAI. Cows with estrus, were more likely to have follicles > 16 mm, had larger follicles before ovulation, and had a greater ovulation risk after AI. Likewise, within the G80 treatment only, cows with estrus that received AIE or TAI had larger follicles, were more likely to have complete luteal regression, had greater ovulation risk, were more likely to have a functional corpus luteum, and had more circulating progesterone after AI. We concluded that delaying induction of ovulation and TAI was effective for allowing more cows to express estrus before AI which had different ovarian function outcomes and greater P/AI than cows that did not express estrus. However, the greater P/AI of cows that expressed estrus was insufficient to compensate for the reduced P/AI of cows that did not express estrus, and thus increase overall P/AI compared with the treatment without delayed induction of ovulation. Detection of estrus before AI in cows undergoing synchronization of ovulation could help identify cows with different likelihoods of pregnancy after insemination.

348 Repeat breeding syndrome: Dexamethasone decreases the prevalence of anti-sperm antibodies in dairy cows

Abstract Cows that require greater than two inseminations to conceive are diagnosed with repeat breeding syndrome (RBS). Anti-sperm antibodies (ASA) in serum are in greater abundance among individuals exhibiting fertility challenges. In humans, treatment with glucocorticoids has been shown to decrease the prevalence of ASA and improve fertility. Therefore, the purpose of this study was to determine the impact of dexamethasone on ASA and pregnancy outcomes in RBS cattle. Holstein multiparous cows (n = 18) diagnosed as having RBS were randomly allotted to one of three treatment groups: Control (C; n = 6), low dexamethasone (LD; n = 6) and high dexamethasone (HD; n = 6). Intramuscular injections of saline (C), 0.05 mg/kg of BW of dexamethasone (LD), or 0.10 mg/kg of BW of dexamethasone (HD) were administered daily starting 4 d prior to insemination (d 0) through insemination (d 4). All treatment volumes were standardized with saline to achieve the same treatment level. Blood was collected on d 0, 4, 8 and 18, with serum extracted on d 0 through 8. Additionally, milk weights were recorded until d 34. For breeding, cows were synchronized using the Double Ovsynch protocol and only one insemination was conducted at the time of breeding. The MIXED procedure in SAS was used to determine the relationship of treatment with the repeated measures of ASA abundance and milk yield. Additionally, a non-parametric chi-square analysis was conducted in SAS using PROC GENMOD to determine the relationship of treatment with immune cell count and pregnancy outcomes. Day, Treatment and Treatment × Day were designated as fixed effects, and a protected post hoc analysis was conducted to account for multiple comparisons. Anti-sperm antibodies tended to decrease (P ≤ 0.082) as dexamethasone increased compared with C, however, there was no Treatment × Day interaction. Daily milk yields for both LD and HD decreased (P < 0.002) compared with C cows, but there was no interaction with day. Though there was an effect for Treatment × Day (P ≤ 0.002) for white blood cell count, percentage lymphocytes, eosinophils, and neutrophils, there was no effect of treatment (P ≥ 0.181). Therefore, interaction differences were largely driven by day (P < 0.001). Surprisingly, there was a trend (P = 0.069) for an increase in pregnancy rates for C cows compared with LD and HD cows. In fact, one-half of the C cows achieved pregnancy compared with just one cow for LD and HD treatments. Overall, dosage of dexamethasone did not differ for ASA or pregnancy outcomes. However, dexamethasone did decrease ASA but did not increase pregnancy rates. Based on these results, we suggest that alternative treatment measures should be explored to improve pregnancy rates in RBS cows.

391 The impact of trace mineral source on systemic immunological status associated with early embryonic loss in lactating dairy cattle

Abstract Milk production has doubled from 1970 to 2009 but has been associated with a decline in fertility. Around 25% of failed pregnancies in dairy cattle are due to embryonic loss. Mineral bioavailability may affect embryonic retention, so we hypothesized that Zn, Cu, and Mn sources will influence systemic immunological status, which affects early embryonic retention. Holstein cows (n = 58) were randomly assigned to one of two daily oral drench trace mineral (Zn, Cu, and Mn) treatments 30 d before breeding (d -30): 1) Inorganic (ITM) or 2) Metal Methionine Hydroxy Analog Chelate (MMHAC). Before treatments began, cows were assigned to a semen type, beef vs. Holstein, equally, across treatments. All cows underwent a double Ovsynch protocol and were artificially inseminated on d 0. Humoral immunological status was assessed in serum samples taken on d 0 and d 7. Immune activity was quantified via a D2Dx systemic immunity score, which assesses samples for the presence of IgG, IgM, cytokines, and complement proteins. Ultrasonography was utilized for pregnancy confirmation on d 35, classifying cows as pregnant (P) or open. Progesterone analysis from d 21 plasma was used to categorize open cows as either non-pregnant (NP) or early embryonic loss (EEL). Statistical analyses in R Studio were completed, in two models based on pregnancy (P vs EEL and NP vs EEL), to determine the effects of mineral treatment, pregnancy status, semen type, and all interactions on humoral immune status. In the P vs EEL model, there were no effects (P > 0.30) of semen type, mineral treatment, pregnancy status, or any interactions on systemic immunity score on the day of breeding (d 0) or d 7. On d 0, cows provided MMHAC had a systemic immunity score of 0.073 ± 0.008 but were not different (P > 0.34) from ITM cows (0.063 ± 0.006). This trend continued on d 7 with systemic immunity scores of MMHAC cows not differing (P > 0.32) from ITM cows (0.055 ± 0.004 and 0.061 ± 0.003; respectively). There was a tendency (P = 0.10) for the three-way interaction of semen type x pregnancy x treatment to influence the immunity score change from d 0 to d 7. Pregnant cows on ITM treatment bred with beef semen had a positive change in immunity score (0.020 ± 0.0085). Whereas ITM cows bred with Holstein semen that underwent EEL had a negative change (-0.015 ± 0.0085); all other means were intermediate. In the NP vs EEL model, there were no effects (P > 0.14) of semen type, treatment, pregnancy status, or any interactions on systemic immunity score on d 0, d 7, or the change between d 0 and d 7. In summary, trace mineral bioavailability tended to affect systemic immunological status in P vs EEL cows but not in NP vs EEL cows, which may allow for the elucidation of immunological status differences during pregnancy establishment.

The economic effect of cow-based reproductive management programs with a systematic use of reproductive hormones

Hormone-based reproductive management programs can be beneficial to improve dairy cow's reproductive performance. This study aimed to compare the economic impact of reproductive management programs using systematic hormonal treatments to individual cows with a specific DIM range with a reproductive management program using cow-specific hormonal treatment based on a veterinary diagnosis of ovarian dysfunction during a fertility check. An existing individual cow-based, dynamic, and stochastic bio-economic simulation model, mimicking the production dynamics of a 200 cow-herd in daily time steps, was extended with ovarian dysfunction and fertility inputs. Four hormone-based reproductive management programs were modeled. In the default reproductive management program, reflecting the current reproductive management of Dutch herds, lactating dairy cows are inseminated based on detection of estrus and non-cyclic dairy cows are treated with hormones based on a veterinary diagnosis of ovarian dysfunction during a fertility check. Hormone treatments prescribed by the veterinarian for anestrus, cystic, and sub-estrus cows were an 8-d progesterone-releasing intravaginal device (PRID)-Synch protocol (PRIDsynch), an Ovsynch protocol, and a PGF2⍺ treatment, respectively. The 3 other reproductive management programs reflected systematic hormonal treatments to cows at specific DIM and included a 1) Double-Ovsynch protocol for TAI with nonpregnant cows submitted to a resynchronization protocol (FTAI), 2) Double-Ovsynch protocol for TAI with nonpregnant cows detected in estrus or submitted to a resynchronization protocol (FTAI+ED), and 3) detection of estrus with cows not detected submitted to a PRIDsynch protocol (ED+TAI). All nonpregnant cows were submitted to a resynchronization protocol based on the absence (PRIDsynch) or presence (Ovsynch protocol) of a corpus luteum (CL). The annual mean net economic return (NER) was calculated for all reproductive management programs. Compared with the default reproductive management program, the highest NER was observed for the FTAI+ED reproductive management program with €23,764 higher net revenues, followed by the FTAI and the ED+TAI reproductive management programs with €19,550 and €14,314 higher net revenues, respectively. Overall, systematic hormone-based reproductive management programs gave higher costs due to more hormones administered and higher calving and feed costs due to more pregnant cows. Nevertheless, the additional revenues of milk and calves in the systematic hormone-based reproductive management programs outweighed the total cost. For instance, the FTAI+ED reproductive management program gave €8,953 higher total cost per year compared with the default but with €32,654 higher revenues. In summary, reproductive management programs where hormones were systematically used gave economic advantages over the current default reproductive management program in which hormones are administered to individual cows based on a veterinary diagnosis of ovarian dysfunction during a fertility check.

Evaluation of treatment with human chorionic gonadotropin at transfer of in vitro–produced beef embryos on reproductive outcomes in lactating multiparous Jersey cows after a synchronized ovulation

Our objective was to evaluate the effect of treatment with human chorionic gonadotropin (hCG) at the time of transfer of in vitro-produced (IVP) beef embryos on pregnancy outcomes in lactating multiparous Jersey cows. Grade 1, stage 7 (expanded blastocyst), IVP beef embryos were produced from black Angus-based dams using 3 proven high-fertility Angus sires and were frozen for direct transfer. In a preliminary experiment, lactating multiparous Jersey cows were randomized to a 2 × 2 factorial arrangement of treatments to test the main effect of recipient synchronization protocol (Double-Ovsynch; DO; n = 169 vs. a synchronized estrus; ED; n = 180) and were randomly assigned within recipient protocol to serve as untreated controls (DO-CON, n = 78; ED-CON, n = 44) or to receive i.m. treatment with 2,500 IU of hCG (DO-hCG, n = 79; ED-hCG, n = 46) at the time of embryo transfer (ET). The recipient utilization rate was greater for DO (93%) than for ED (50%) cows, and an interaction was present between recipient synchronization protocol and hCG treatment in which DO-hCG cows had more pregnancies per ET (P/ET) at 26, 33, and 61 d than DO-CON, ED-hCG, and ED-CON cows. Based on a partial budget analysis, the cost per pregnancy for DO cows was $135.35 less than for ED cows. In experiment 2, lactating multiparous Jersey cows were submitted to a Double-Ovsynch protocol (DO, n = 386) and were randomly assigned to serve as untreated controls (CON, n = 192) or were treated with 2,500 IU hCG (hCG, n = 194) at ET. Progesterone concentrations and total luteal volume 7 d after ET were greater for hCG than for CON cows. In contrast to the preliminary experiment, treatment with hCG did not affect P/ET at 26, 33, or 61 d, and treatment with hCG did not affect pregnancy loss from 26 to 61 d. In conclusion, treatment with 2,500 IU of hCG at ET increased P4 concentrations and total luteal volume 7 d after ET but did not increase pregnancy outcomes or decrease pregnancy loss in lactating multiparous Jersey cows receiving frozen/thawed IVP beef embryos.

Effect of a targeted reproductive management program based on automated detection of estrus during the voluntary waiting period on reproductive performance of lactating dairy cows

The objective of this experiment was to evaluate the effect on reproductive performance of a targeted reproductive management (TRM) program for first postpartum insemination (AI) that prioritized AI at detected estrus (AIE) by providing different intervals for estrus detection based on records of automated estrus alerts (AEA) during the voluntary waiting period (VWP). A secondary objective was to evaluate the association between occurrence of AEA during the VWP and reproductive performance. Lactating Holstein cows (n = 1,260) fitted with neck behavior monitoring sensors for detection of estrus were randomly assigned to a program that used all-timed AI (TAI) for first service (ALL-TAI; n = 632) or a TRM program that prioritized AIE and used TAI only for cows not detected in estrus (TP-AIE; n = 628). Cows in the ALL-TAI treatment received TAI at 76 ± 3 days in milk (DIM) after a Double-Ovsynch protocol. Cows in the TP-AIE treatment were eligible for AIE for 30 ± 3 or 16 ± 3 d after a 49 d VWP if at least one (n = 346) or no (n = 233) AEA were recorded from 15 to 49 DIM. Cows not AIE received TAI after an Ovsynch protocol with progesterone supplementation at 90 ± 3 or 76 ± 3 DIM if the cow had or did not have AEA during the VWP, respectively. Data were analyzed by logistic and Cox's proportional hazard regression. In the TP-AIE treatment, 69.3 % of cows received AIE and more cows with (83.3 %) than without (45.0 %) AEA during the VWP received AIE. Cows in the TP-AIE (69.0 ± 0.7 d) treatment had fewer days from calving to first AI than cows in the ALL-TAI (75.7 ± 0.8 d) treatment. The proportion of cows pregnant by 150 DIM (ALL-TAI = 59.1 % and TP-AIE = 56.0 %) and the hazard ratio (HR) for time to pregnancy (1.0 [95 % confidence interval: 0.9, 1.2]) did not differ between treatments and median days to pregnancy were 102 and 107 for the ALL-TAI and TP-AIE treatments, respectively. Overall, the ALL-TAI (42.3 %) treatment had more first service pregnancies per AI (P/AI) than the TP-AIE (29.0 %) treatment. Cows with AEA during the VWP had greater P/AI (42.5 % vs. 28.9 %), proportion of cows pregnant by 150 DIM (67.4 % vs. 47.0 %), and HR for time to pregnancy (1.6 [1.4, 1.9]) than cows without AEA during the VWP. We conclude that a TRM program that prioritized AIE based on AEA during the VWP led to a similar pregnancy rate and proportion of cows pregnant by mid-lactation than a program that used all-TAI with extended VWP despite fewer P/AI to first service. Also, expression of estrus during the VWP was associated with improved reproductive performance. Thus, AEA during the VWP could be used as a predictor of reproductive potential for TRM of lactating dairy cows.

Effect of Double-Ovsynch and Presynch-Ovsynch on postpartum ovarian cysts and inactive ovary in high-yielding dairy cows.

Optimizing the management of dairy cattle reproduction can reduce postpartum ovarian disease in high-yielding dairy cows and thus enhance ranch economic benefit. The hypothesis of this study was that the Double-Ovsynch (DO) protocol in high-producing dairy cows would result in a lower incidence of follicular cysts but a higher incidence of luteal cysts compared to those undergoing the Presynch-Ovsynch (PS) protocol. In this experiment, 384 cows (204 primiparous and 180 multiparous) were allocated to the DO group, which followed the protocol: GnRH-7d-PGF2α-3d-GnRH-7d-Ovsynch-56 h (GnRH-7d-PGF2α-56 h-GnRH-16hTAI), starting on 39 ± 3 days in milk (DIM). Additionally, 359 cows (176 primiparous and 183 multiparous) were assigned to the PS group, which followed the protocol: PGF2α-14d-PGF2α-12d-Ovsynch-56 h, starting on 31 ± 3 DIM. In DO, B-mode ultrasound examinations were conducted 1 day after the GnRH-7d-PGF2α-3d-GnRH protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days of suspected cases. In PS, B-mode ultrasound examinations were conducted 1 day after the PGF2α-14d-PGF2α protocol to diagnose the presence of ovarian diseases followed by reexamination after 7 days. For all cows confirmed to having ovarian diseases, a second B-mode ultrasound examination was conducted at the time of the second GnRH and timed artificial insemination (TAI). If the ovary showed a normal developing follicle in combination with normal ovulation, the ovarian disease was considered to be cured. The current study revealed no significant difference in the overall incidence and cure rate of postpartum ovarian diseases between DO and PS (incidence rate: 3.9% vs. 6.7%, cure rate: 50% vs. 41.7%, DO vs. PS). Also, there was no significant difference in the incidence and cure rate of luteal cysts between DO and PS (incidence rate: 2.9% vs. 2.2%, cure rate: 50.0% vs. 50.0%). The incidence of follicular cysts was significantly lower in the DO group than in the PS group (0.8% vs. 2.8%, DO vs. PS, p = 0.037), but there was no significant difference in the cure rates (66.7% vs. 50%). The occurrence of inactive ovary was lower in DO compared to PS (0.2% vs. 1.7%, p = 0.047). There was no significant difference in the pregnancy rate between the DO and PS groups (48.2% vs. 41.8%), although the DO group had a higher rate. What is different from our assumption is that PS did not effectively reduce the incidence of postpartum luteal cysts.

Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation

Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM). Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd versus even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol (DO; n = 707) or a protocol to synchronize estrus (ED; n = 565). All ED cows detected in estrus were inseminated (EDAI; n = 424), with undetected cows receiving TAI after an Ovsynch protocol (EDTAI; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5% ± 0.04% vs. 77.1% ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2% ± 0.03% vs. 43.6% ± 0.03%; beef, 64.2% ± 0.04% vs. 56.3% ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1% ± 0.03% vs. 40.6% ± 0.03%; beef, 65.5% ± 0.04% vs. 56.2% ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0% and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1% ± 0.01% vs. 79.2% ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0% ± 0.02% vs. 49.2% ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8% ± 0.04% vs. 51.0% ± 0.05%, respectively) or maintained or gained (55.6% ± 0.04% vs. 50.8% ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1% ± 0.04% vs. 36.1% ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.

Association of transition cow health with pregnancy per artificial insemination and pregnancy loss in Holstein cows submitted to a Double-Ovsynch protocol for first service

This observational study was conducted to evaluate the effect of transition cow health on pregnancy per artificial insemination (P/AI) and pregnancy loss (PL) in cows submitted to a Double-Ovsynch protocol (DO) for first service. Lactating Holstein cows (n = 15,041) from one commercial dairy farm in northern Germany between January 2015 to December 2021 were enrolled into a modified Double-Ovsynch protocol (GnRH, 7 d later PGF2α, 3 d later GnRH, 7 d later GnRH, 7 d later PGF2α, 24 h later PGF2α, 32 h later GnRH, and 16 to 18 h later timed artificial insemination) for first service at 72 ± 3 d in milk. Pregnancy was diagnosed at 32 and 60 d post-AI via transrectal ultrasonography. Pregnancy loss was defined as the proportion of cows diagnosed pregnant 32 d post-artificial insemination that were diagnosed nonpregnant 60 d post-artificial insemination. Health-related events (i.e., milk fever [MF], hyperketonemia [KET], retained fetal membranes [RFM], metritis, mastitis, left displaced abomasum [LDA]) were assessed by farm personnel using standard operating procedures. Multivariable logistic regression was used for testing potential associations between transition cow health event occurrence and outcome variables, including P/AI and PL. Three separate models were built for cows in first lactation, second lactation, and ≥third lactation. Overall, 20.0% (885/4,430), 34.9% (1,391/3,989), and 53.9% (3,570/6,622) of cows had at least one transition cow health event for first, second, and ≥third lactations, respectively. The most prevalent transition cow health event for first-lactation cows was metritis (10.7%; [473/4,430]), whereas second-lactation cows suffered mostly from mastitis (16.6%; [664/3,989] and KET (16.6%; [661/3,989]), and cows with ≥third lactations were mostly affected by KET (33.2%; [2,198/6,622]). We observed a negative association between inflammatory disorders (i.e., RFM, metritis, mastitis) and P/AI in all cows irrespective of parity. Metabolic disorders (i.e., MF, KET, LDA) were negatively associated with P/AI only in multiparous cows. Irrespective of parity, only uterine diseases (i.e., RFM, metritis) were significantly associated with PL. These results show that enrolling cows into a fertility protocol, such as DO, cannot overcome the carryover effects of inflammatory and metabolic disorders on P/AI and PL and highlight the importance of optimizing transition cow health as a prerequisite for achieving high fertility in a DO protocol.

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.

Effect of reproductive management programs that prioritized artificial insemination at detected estrus or timed artificial insemination on the reproductive performance of primiparous Holstein cows of different genetic merit for fertility

Our objective was to compare reproductive outcomes of primiparous lactating Holstein cows of different genetic merit for fertility submitted for insemination with management programs that prioritized artificial insemination (AI) at detected estrus (AIE) or timed AI (TAI). Moreover, we aimed to determine whether subgroups of cows with different fertility potential would present a distinct response to the reproductive management strategies compared. Lactating primiparous Holstein cows (n = 6 commercial farms) were stratified into high (Hi-Fert), medium (Med-Fert), and low (Lo-Fert) genetic fertility groups (FG) based on a Reproduction Index value calculated from multiple genomic-enhanced predicted transmitting abilities. Within herd and FG, cows were randomly assigned either to a program that prioritized TAI and had an extended voluntary waiting period (P-TAI; n = 1,338) or another that prioritized AIE (P-AIE; n = 1,416) and used TAI for cows, not AIE. Cows in P-TAI received first service by TAI at 84 ± 3 d in milk (DIM) after a Double-Ovsynch protocol, were AIE if detected in estrus after a previous AI, and received TAI after an Ovsynch-56 protocol at 35 ± 3 d after a previous AI if a corpus luteum (CL) was visualized at nonpregnancy diagnosis (NPD) 32 ± 3 d after AI. Cows with no CL visualized at NPD received TAI at 42 ± 3 d after AI after an Ovsynch-56 protocol with progesterone supplementation (P4-Ovsynch). Cows in P-AIE were eligible for AIE after a PGF2α treatment at 53 ± 3 DIM and after a previous AI. Cows not AIE by 74 ± 3 DIM or by NPD 32 ± 3 d after AI received P4-Ovsynch for TAI at 74 ± 3 DIM or 42 ± 3 d after AI. Binary data were analyzed with logistic regression, count data with Poisson regression, continuous data by ANOVA, and time to event data by Cox's proportional hazard regression. Pregnancy per AI (P/AI) to first service was greater for cows in the Hi-Fert (59.8%) than the Med-Fert (53.6%) and Lo-Fert (47.7%) groups, and for the P-TAI (58.7%) than the P-AIE (48.7%) treatment. Overall, P/AI for all second and subsequent AI combined did not differ by treatment (P-TAI = 45.2%; P-AIE = 44.5%) or FG (Hi-Fert = 46.1%; Med-Fert = 46.0%; Lo-Fert = 42.4%). The hazard of pregnancy after calving was greater for the P-AIE than the P-TAI treatment [hazard ratio (HR) = 1.27, 95% CI: 1.17 to 1.37)], and for the Hi-Fert than the Med-Fert (HR = 1.16, 95% CI: 1.05 to 1.28) and Lo-Fert (HR = 1.34, 95% CI: 1.20 to 1.49) groups. More cows in the Hi-Fert (91.2%) than the Med-Fert (88.4%) and Lo-Fert (85.8%) groups were pregnant at 200 DIM. Within FG, the hazard of pregnancy was greater for the P-AIE than the P-TAI treatment for the Hi-Fert (HR = 1.41, 95% CI: 1.22 to 1.64) and Med-Fert (HR = 1.28, 95% CI: 1.12 to 1.46) groups but not for the Lo-Fert group (HR = 1.13, 95% CI: 0.98 to 1.31). We conclude that primiparous Holstein cows of superior genetic merit for fertility had better reproductive performance than cows of inferior genetic merit for fertility, regardless of the type of reproductive management used. In addition, the effect of programs that prioritized AIE or TAI on reproductive performance for cows of superior or inferior genetic merit for fertility depended on the outcomes evaluated. Thus, programs that prioritize AIE or TAI could be used to affect certain outcomes of reproductive performance or management.

Effect of increasing GnRH dose during Double- Ovsynch on fertility of lactating dairy cows

The rate of ovulation to the first GnRH treatment of Ovsynch-type protocols is key to achieve excellent fertility. In cows syn­chronized with the Double-Ovsynch protocol (DO), only around half of the cows ovulate to the third GnRH injection (first GnRH of the Breeding-Ovsynch portion of Double-Ovsynch). Increas­ing the dose of GnRH at this time has been proven to improve ovulatory response, reaching up to 67% of ovulation rate. Our objective was to determine whether increasing the dose of the third GnRH of DO could improve the reproductive outcomes at first service.

Targeted reproductive management for lactating Holstein cows: Reducing the reliance on exogenous reproductive hormones

Adoption of automated monitoring devices (AMD) affords the opportunity to tailor reproductive management according to the cow's needs. We hypothesized that a targeted reproductive management (TRM) would reduce the use of reproductive hormones while increasing the percentage of cows pregnant 305 d in milk (DIM). Holstein cows from 2 herds (n = 1,930) were fitted with an AMD at 251.0 ± 0.4 d of gestation. Early-postpartum estrus characteristics (EPEC; intense estrus = heat index ≥70; 0 = minimum, 100 = maximum) of multiparous cows were evaluated at 40 (herd 1) or 41 (herd 2) DIM and EPEC of primiparous cows were evaluated at 54 (herd 1) or 55 (herd 2) DIM. Control cows received the first artificial insemination at fixed time (TAI; primiparous, herd 1 = 82 and herd 2 = 83 DIM; multiparous, herd 1 = 68 and herd 2 = 69 DIM) following the Double-Ovsynch (DOV) protocol. Cows enrolled in the TRM treatment were managed as follows: (1) cows with at least one intense estrus were inseminated upon AMD detected estrus for 42 d and, if not inseminated, were enrolled in the DOV protocol; and (2) cows without an intense estrus were enrolled in the DOV protocol at the same time as cows in the control treatment. Control cows were re-inseminated based on visual or patch aided detection of estrus, whereas TRM cows were re-inseminated as described for control cows with the aid of the AMD. Cows received a GnRH injection 27 ± 3 d after insemination and, if diagnosed as nonpregnant, completed the 5-d Cosynch protocol and received TAI 35 ± 3 d after insemination. Among cows in the TRM treatment, 55.8 and 42.9% of primiparous and multiparous cows, respectively, received the first insemination in spontaneous estrus. The interaction between treatment and parity affected pregnancy 67 d after the first AI (primiparous: control = 37.6%, TRM = 27.4%; multiparous: control = 41.0%, TRM = 44.7%). The TRM treatment increased re-insemination in estrus (control = 48.3%, TRM = 70.5%). Pregnancy 67 d after re-inseminations tended to be affected by the interaction between treatment and EPEC (no intense estrus: control = 25.3%, TRM = 32.0%; intense estrus: control = 32.9%, TRM = 32.2%). The interaction between treatment and EPEC affected pregnancy by 305 DIM (no intense estrus: control = 80.8%, TRM = 88.2%; intense estrus: control = 87.1%, TRM = 86.1%). Treatment did not affect the number of reproductive hormone treatments among cows that had not had an intense estrus (control = 10.5 ± 0.3, TRM = 9.1 ± 0.2 treatments/cow), but cows in the TRM treatment that had an intense estrus received fewer reproductive hormone treatments than cows in the control treatment (2.0 ± 0.1 vs. 9.6 ± 0.2 treatments/cow). Selecting multiparous cows for first AI in estrus based on EPEC reduced the use of reproductive hormones without impairing the likelihood of pregnancy to first AI. The use of AMD for re-insemination expedited the establishment of pregnancy among cows that did not display an intense estrus early postpartum.

099 Effect of synchrony and expression of oestrus on fertility of lactating Jersey cows submitted to a Double-Ovsynch protocol for timed artificial insemination or artificial insemination after a synchronized oestrus

099 Effect of synchrony and expression of oestrus on fertility of lactating Jersey cows submitted to a Double-Ovsynch protocol for timed artificial insemination or artificial insemination after a synchronized oestrus

Replacement of the first GnRH by estradiol in the breeding Ovsynch of Double Ovsynch protocol could improve fertility in Holstein dairy cows

Unlike GnRH, estradiol could induce emergence of a new follicular wave regardless of the size of follicle. Therefore, the present study was conducted to understand whether replacement of the first GnRH by estradiol in the breeding protocol of Double Ovsynch program could enhance fertility. Cows were randomly assigned to two groups, including Double Ovsynch protocol (Control; n = 120) and Ovsynch-estradiol-PGF2α-GnRH (EPG) protocol (Treatment; n = 120). Cows in both groups were subjected to presynchronization Ovsynch. Seven days later, cows in the control group received GnRH, which was followed by PGF2α and GnRH 7 days and 9 days plus 8 h later, respectively. Cows in treatment group received estradiol 7 days after the second GnRH of presynchronization Ovsynch, which was followed by PGF2α and GnRH 7 days and 10 days plus 8 h later, respectively. Cows were subjected to timed AI (TAI) 16 h after final GnRH in both groups. Pregnancy per AI (P/AI) was greater in cows in treatment than control group (64.17 % vs. 44.17 %, respectively; P = 0.02). Cows with a follicle with diameter ≥ 10 mm (F10) at the beginning of EPG in treatment group had greater P/AI than cows without a F10 at the beginning of breeding Ovsynch in control group (P ≤ 0.05). Pregnancy per AI was greater in cows with a CL at the beginning of EPG in treatment group than cows without a CL at the same timepoint in treatment group, and cows with or without a CL at the beginning of breeding Ovsynch in control group (P ≤ 0.05). In conclusion, inclusion of estradiol in Double Ovsynch protocol as a replacement for the first GnRH of breeding Ovsynch could improve fertility, particularly in cows with a CL at the initiation of EPG.

Synchronization of Ovulation and Timed Insemination in Lactating Dairy Cattle

Abstract Successful reproduction of lactating dairy cattle, or in other words its reproductive performance is a limiting factor in the profit ratio of cattle breeding regarding market production. The aim of this research was to evaluate the success rate of synchronization protocols Ovsynch, Presynch/Ovsynch, and Double Ovsynch within the period of 24 months. The success rate of the 1st insemination, 2nd insemination, and after more than 2 inseminations was evaluated. The cattle were of Holstein Friesian breed with a milk yield of 10 200 kg. The animals were sorted into two categories – heifers (protocol Ovsynch) and primiparous, multiparous cows (protocols Presynch/Double Ovsynch). The research proved a 54 % success rate in the category of heifers after the 1st insemination. In the category of primiparous and multiparous cows was the success rate of 41 % after the 1st insemination, 39 % after the 2nd insemination, and 52 % after more than 2 inseminations for the Presynch/Ovsynch protocol. The success rate for Double Ovsynch protocol was 45 % after the 1st insemination, 42 % after the 2nd insemination and 51 % after more than 2 inseminations. The results for the given geographic region of Slovakia exceeded the average.

Efficacy of a modified Double-Ovsynch protocol for the enhancement of reproductive performance in Hanwoo cattle.

We aimed to evaluate the efficacy of a modified Double-Ovsynch protocol vs artificial insemination following estrus detection (AIED) for the enhancement of reproductive performance in Hanwoo cattle. Four hundred twelve Hanwoo cows were allocated to two treatment groups. The first group of cows were administered gonadotropin releasing hormone (GnRH) on Day 36 (±0.6), prostaglandin F2α (PGF2α) on Day 46 (8 to 12 days later), and GnRH on Day 49, which was followed by Ovsynch, consisting of an injection of GnRH on Day 56, PGF2α on Day 63, and GnRH 56 h and timed AI (TAI) 16 h later (modified Double-Ovsynch group, n = 203). The second group of cows underwent AIED (AIED group, n = 209) and were designated as controls. The pregnancy per AI 60 days after the first AI was higher in the modified Double- Ovsynch (68.5%) than in the AIED (56.5%) group, resulting in a higher probability of pregnancy per AI (odds ratio: 1.68, p<0.05). Moreover, cows in the modified Double- Ovsynch group were more likely (hazard ratio: 1.28, p<0.05) to be pregnant by 150 days after calving than cows in the AIED group, and this difference was associated with a lower mean number of AIs per conception (1.27 vs 1.39, p<0.05) and a shorter median interval between calving and pregnancy (72 vs 78 days, p<0.1). The modified Double-Ovsynch protocol, adjusted according to the herd visit schedule, can be readily used to increase the pregnancy per AI following the first AI and to shorten the interval between calving and pregnancy in beef herds.

Effect of a targeted reproductive management program designed to prioritize insemination at detected estrus and optimize time to insemination on the reproductive performance of lactating dairy cows

The primary objective of this randomized controlled experiment was to evaluate the insemination dynamic and reproductive performance of cows managed with a targeted reproductive management (TRM) program designed to prioritize artificial insemination (AI) at detected estrus (AIE) and optimize timing of AI by grouping cows based on detection of estrus during the voluntary waiting period (VWP). Our secondary objective was to evaluate reproductive outcomes for cows with or without estrus during the VWP. Lactating Holstein cows fitted with an ear-attached sensor for detection of estrus were randomly assigned to a TRM treatment that prioritized AIE based on detection of estrus during the VWP (TP-AIE; n = 488), a non-TRM treatment that prioritized AIE (P-AIE; n = 489), or an all timed AI (TAI) treatment with extended VWP (ALL-TAI; n = 491). In TP-AIE, cows with or without automated estrus alerts (AEA) recorded during the VWP received AIE if detected in estrus for at least 31 ± 3 or 17 ± 3 d after a 49 d VWP, respectively. Cows not AIE with or without AEA during the VWP received TAI after Ovsynch with progesterone supplementation and 2 PGF2α treatments (P4-Ov) at 90 ± 3 or 74 ± 3 d in milk (DIM), respectively. In P-AIE, cows received AIE if detected in estrus for 24 ± 3 d after a 49 d VWP, and if not AIE received TAI at 83 ± 3 DIM after P4-Ov. In ALL-TAI, cows received TAI at 83 ± 3 DIM after a Double-Ovsynch protocol. Data were analyzed by logistic and Cox's proportional hazard regression. The proportion of cows AIE did not differ for TP-AIE (71.0%) and P-AIE (74.6%). Overall P/AI at 39 d after first service was greater for the ALL-TAI (47.6%) than for the P-AIE (40.2%) and TP-AIE (39.5%) treatments. The hazard of pregnancy up to 150 DIM was greater for cows in TP-AIE (hazard ratio = 1.2; 95% confidence interval: 1.1-1.4) and P-AIE (hazard ratio = 1.2; 95% confidence interval: 1.1-1.4) than for cows in the ALL-TAI treatment which resulted in median time to pregnancy of 89, 89, and 107 d. Conversely, the proportion of cows pregnant at 150 DIM did not differ (ALL-TAI 78.5%, P-AIE 76.3%, TP-AIE 76.0%). Except for a few outcomes for which no difference was observed, cows detected in estrus during the VWP had better performance than cows not detected in estrus. Cows with AEA during the VWP were more likely to receive AIE, had greater P/AI, and greater pregnancy rate up to 150 DIM regardless of first service management. We conclude that a TRM program designed to prioritize AIE by grouping cows based on detection of estrus during the VWP was an effective strategy to submit cows for first service resulting in similar or improved performance than a non-TRM program that prioritized AIE or an all-TAI program with extended VWP. Also, AEA recorded during the VWP might be used as a strategy for identifying subgroups of cows with different reproductive performance.

Association between body condition score fluctuations and pregnancy loss in Holstein cows.

The objective of this study was to characterize the associations between body condition score (BCS) and BCS change (∆BCS), determined by an automated camera system during early lactation and close to artificial insemination (AI), and the subsequent pregnancy loss (PL) in Holstein cows. A secondary objective was to determine the impact of disease on PL, considering multiple time periods relative to AI. Data from 9,430 lactations in 6,884 Holstein cows in a commercial dairy operation located in Colorado, USA were included in this retrospective observational study. Cows were subject to first AI at about 80 DIM (primiparous) and 60 DIM (multiparous), following a double OvSynch protocol. Pregnancy diagnosis was performed via transrectal ultrasonography on day 32 ± 3 after AI and reconfirmed on day 80 ± 3 after AI. Cameras mounted on the sorting gate at each exit (n = 2) of the milking parlor generated BCS on a five-point scale with 0.1 increments. The BCS at calving (BCS1), 21 DIM (BCS21), 56 DIM (BCS56), AI resulting in pregnancy (BCSAI), and 90 d post AI (BCSAI90) were selected for the analyses and subsequently categorized as low (≤ lower quartile), moderate (interquartile range), and high (≥ upper quartile). Changes in BCS were calculated by periods of interest as change from calving to 21 DIM; change from calving to 56 DIM; change from 56 DIM to AI; and change from AI to 90 d post AI and assigned into categories to facilitate the analysis. Data were examined using logistic regression, considering parity category, season at calving and AI, DIM at AI, milk yield up to 60 DIM, and occurrence of disease as covariables. The logistic regression analyses indicated that the odds of PL were greater in cows in the low BCS category relative to cows in the high BCS category at 56 DIM (OR 95% CI = 1.41 [1.12-1.79]), AI (1.31 [1.05-1.65]), and 90 d post AI (1.38 [1.10-1.74]). Likewise, cows with large loss in BCS between calving and 21 DIM (1.46 [1.10-1.94]) and loss in BCS between AI and 90 d post AI (1.44 [1.15-1.81]) had greater odds of PL compared with cows with no loss of BCS within the same period. Occurrence of disease at all the time periods considered in the analysis had a consistent detrimental impact on maintenance of the pregnancy, supporting the concept that pre and postconceptional disease affects embryonic survival. Overall, low BCS, more pronounced reductions in BCS occurring closer to AI, and occurrence of disease resulted in greater PL in this Holstein population.

Heat synchronization and the effectiveness of insemination of cows of Holstein breed under the conditions of the dairy complex

The food security of country is largely determined by the development of animal husbandry branches. Dairy cattle breeding is of particular importance, which has been actively developing in recent years due to the modernization of farms and complexes, the introduction of innovative technologies and the formation of a highly productive breeding herd. The most important link in the development of dairy cattle breeding is the reproduction of the herd. Modern technologies make it possible to use hormonal drugs in order to optimize the reproductive traits of animals. The results of clinical and experimental studies have shown the important role of hormones in the regulation of physiological functions, as well as the possibility of their use for directed changes in metabolism, productivity and fertility of animals. The purpose of the research was to assess the influence of methods of synchronization of heat of cows on the pregnancy rate under the conditions of the dairy complex. The research data on the effectiveness of insemination when identifying animals in visually heat and using Heatime neck strips, as well as when using heat synchronization programs such as Presynch and Double Ovsynch have been presented in the article. The research has been carried out under the conditions of a modern dairy complex on a highly productive herd of cows of Holstein breed. Differences in the effectiveness of insemination by using the studied methods were revealed from 49,1 to 72,5 %. The highest conception rate has been observed in first-calf heifers (83,0 %) and cows (62,5 %) inseminated using the Double Ovsynch protocol. The dependence of the level of conception rate on the presence of diseases suffered by cows during the newcalving period and until the moment of insemination has been noted. In sick animals, the conception rate for groups of first-calf heifers and cows was significantly lower than in healthy animals. Thus, according to the Double Ovsynch insemination protocol, the conception rate in healthy animals was 83,7 %, and in those who were ill – 65,2 %. The research results confi rmed the validity of stopping the use of the Presynch protocol and completely transferring the dairy herd of cows to synchronization and insemination using the Double Ovsynch protocol.