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

Fertility programs for lactating dairy cows: A novel presynch + timed artificial insemination program (Double E-Synch) produces similar ovarian dynamics, synchronization, and fertility as Double-Ovsynch

Fertility programs were implemented for the first postpartum timed artificial insemination (TAI) in 800 (primiparous and multiparous) lactating dairy cows, evaluating 2 presynchronization (presynch) strategies and 2 TAI protocols, in a 2 × 2 factorial arrangement. Weekly, cows were enrolled into 1 of 4 groups (Ovs+Ovs [Double-Ovsynch], Ovs+OvsP4/E2, PreP4/E2+Ovs, and PreP4/E2+OvsP4/E2 [Double E-Synch]). On d -17 (34 ± 3 DIM), the Ovsynch [Ovs] presynch was initiated with 10 µg of buserelin acetate (GnRH), and cows received 0.5 mg of cloprostenol sodium PGF2α analog (PGF) on d -10, and 10 µg of GnRH on d -7. The PreP4/E2 presynch was initiated on d -17 with a used 2-g progesterone (P4) insert, which was removed on d -10, together with 0.5 mg of PGF and 1 mg of estradiol (E2) cypionate (EC). For TAI protocols, Ovs group received the following: on d 0, 20 µg of GnRH (double dose); on d 7, PGF; on d 8, PGF; on d 9.5, 10 µg of GnRH; and on d 10, TAI (16 h after GnRH). Cows submitted to OvsP4/E2 received the following: on d 0, 20 µg of GnRH (double dose) and a new 2-g P4 insert; on d 7, PGF; on d 8, P4 insert removal, PGF, and EC; and on d 10, TAI (48 h after P4 insert removal). The GLIMMIX procedure of SAS 9.4 was used for statistical analyses (P ≤ 0.05). The presence of corpus luteum (CL) on d -17 (average = 68.8% [550/800]) was similar among treatments. The presence of CL on d 0 of TAI protocols was high, and Ovs as a presynch increased percentage of cows with CL (95.5% [382/400] vs. 90.8% [363/400]). However, at the first PGF of the breeding (TAI) protocols (d 7), there was no effect of presynchronization program and 98.5% (788/800) of the cows had at least 1 CL. Ovulation after d 0 was greater in cows submitted to PreP4/E2 than Ovs (72.0% [288/400] vs. 64.3% [257/400]), and those ovulating had greater pregnancies per artificial insemination (P/AI; 51.0% [278/545] vs. 41.6% [106/255]). Overall, multiple ovulations after TAI were low and similar between TAI protocols and presynch strategies (7.2% [54/753]). Expression of estrus in OvsP4/E2 protocols was greater than Ovs (69.4% [274/395] vs. 41.5% [168/405]), and an interaction was detected, in which cows not expressing estrus ovulated more after TAI in Ovs compared with OvsP4/E2 protocol (93.3 [221/237] vs. 77.7% [94/121]). Cows expressing estrus had greater P/AI in both Ovs (58.3 [98/168] vs. 42.2% [100/237]) and OvsP4/E2 (57.3 [157/274] vs. 24.0% [29/121]). There was no interaction between presynch and TAI protocol on P/AI on d 32 of cows that ovulated after TAI (48.4%, 49.7%, 53.3%, and 52.5% for Ovs+Ovs, Ovs+OvsP4/E2, PreP4/E2+Ovs, and PreP4/E2+OvsP4/E2, respectively), and no differences in pregnancy loss between d 32 and 90 (average = 24.0% [92/384]). In conclusion, the study validated 2 presynchronization strategies and 2 TAI protocols, establishing 4 possible fertility programs, all of them producing well-controlled ovarian dynamics, excellent synchronization, and high fertility. Moreover, Double-Ovsynch and Double E-Synch both produced similar results, despite differences in pharmacological bases.

Estrogen to progesterone ratio is associated with conceptus attachment in dairy cows receiving artificial insemination after Double-Ovsynch but not estrus†

Prediction of pregnancy survival in lactating dairy cows can be determined by the conceptus attachment timeframe via daily pregnancy-specific protein B (PSPB) monitoring. All factors contributing to reduced fertility in dairy cows receiving AI following estrus detection remain unclear. This study aimed to determine differences in time to conceptus attachment in lactating cows treated with the fertility program Double-Ovsynch compared to cows that were detected in estrus. Additionally, we investigated various pre- and post-conception factors potentially influencing fertility outcomes. We hypothesized that AI following a natural estrus detected with automated activity monitors would lead to an extended time to conceptus attachment and lower PSPB concentrations post-attachment compared to Double-Ovsynch. There were no differences in the average time to conceptus attachments between treatments. However, cows inseminated post-estrus that experienced pregnancy loss between conceptus attachment and 60-66 days post-AI exhibited diminished PSPB concentrations on Days 2 and 3 following conceptus attachment. Steroid hormone interactions were assessed with radioimmunoassay to determine the ratios of estrogen to progesterone concentrations on the day of the luteinizing hormone (LH) surge. Notably, estrogen to progesterone ratio proved to predict conceptus attachment in cows subjected to Double-Ovsynch but not in those inseminated post-estrus detection surge. In conclusion, the estrogen to progesterone ratio measured around the time of the pre-ovulatory LH surge emerges as a potentially effective tool for estimating the fertility potential of lactating dairy cows undergoing timed AI, particularly in the context of the Double-Ovsynch program.

Combining reproductive outcomes predictors and automated estrus alerts recorded during the voluntary waiting period identified subgroups of cows with different reproductive performance potential

The objective was to compare differences in reproductive performance for dairy cows grouped based on the combination of data for predictors available during the prepartum period and before the end of the voluntary waiting period (VWP), automated estrus alerts (AEA) during the VWP, and the combination of both factors. In a cohort study, data for AEA and potential predictors of the percentage of cows that receive AI at detected estrus (AIE), pregnancies per AI (P/AI) for first service, and the percentage of cows pregnant by 150 DIM (P150) were collected from -21 to 49 DIM for lactating Holstein cows (n = 886). The association between each reproductive outcome with calving season (cool, warm), calving-related events (yes, no), genomic daughter pregnancy rate (gDPR; high, medium, low), days in the close-up pen (ideal, not ideal), health disorder events (yes, no), rumination time (high or low CV prepartum and high or low increase rate postpartum), and milk yield (MY) by 49 DIM (high, medium, low) were evaluated in univariable and multivariable logistic regression models. Individual predictors (health disorders, gDPR, and MY) associated with the 3 reproductive outcomes in all models were used to group cows based on risk factors (RF; yes, n = 535 or no, n = 351) for poor reproductive performance. Specifically, cows were included in the RF group if any of the following conditions were met: the cow was in the high MY group, had low gDPR, or had at least 1 health disorder recorded. Cows were grouped into estrus groups during the VWP based on records of AEA (estrus VWP [E-VWP], n = 476 or no estrus VWP [NE-VWP], n = 410). Finally, based on the combination of levels of AEA and RF, cows were grouped into an estrus and no RF (E-NoRF, n = 217), no estrus and RF (NE-RF, n = 276), no estrus and no RF (NE-NoRF, n = 134), and estrus and RF (E-RF, n = 259) groups. Cows received AIE up to 31 d after the end of the VWP, and if they did not receive AIE, they received timed AI after an Ovsynch plus progesterone protocol. Logistic and Cox proportional hazard regression compared differences in reproductive outcomes for different grouping strategies. The NoRF (AIE: 76.9%; P/AI: 53.1%; P150: 84.5%) and E-VWP (AIE: 86.8%; P/AI: 44.8%; P150: 82.3%) groups had more cows AIE and higher P/AI and P150 than the RF (AIE: 64.5%; P/AI: 34.9%; P150: 72.9%) and NE-VWP (AIE: 50.0%; P/AI: 38.9%; P150: 72.1%) groups, respectively. When both factors were combined, the largest and most consistent differences were between the E-NoRF (AIE: 91.3%; P/AI: 58.7%; P150: 88.5%) and NE-RF groups (AIE: 47.3%; P/AI: 35.8%; P150: 69.5%). Compared with the whole population of cows or cows grouped based on a single factor, the E-NoRF and NE-RF groups had the largest and most consistent differences with the whole cow cohort. The E-NoRF and NE-RF groups also had statistically significant differences of a large magnitude when compared with the remaining cow cohort after removal of the respective group. We conclude that combining data for AEA during the VWP with other predictors of reproductive performance could be used to identify groups of cows with larger differences in expected reproductive performance than if AEA and the predictors are used alone.

Reproduction in the era of genomics and automation

Much progress has been made in the reproductive efficiency of lactating dairy cows across the USA in the past 20years. The standardisation of evaluation of reproductive efficiency, particularly with greater focus on metrics with lesser momentum and less lag-time such as 21-day pregnancy rates (21-day PR), and the recognition that subpar reproductive efficiency negatively impacted profitability were major drivers for the changes that resulted in such progress. Once it became evident that the genetic selection of cattle for milk yield regardless of fertility traits was associated with reduced fertility, geneticists raced to identify fertility traits that could be incorporated in genetic selection programs with the hopes of improving fertility of lactating cows. Concurrently, reproductive physiologists developed ovulation synchronisation protocols such that after sequential treatment with exogenous hormones, cows could be inseminated at fixed time and without detection of oestrus and still achieve acceptable pregnancy per service. These genetic and reproductive management innovations, concurrently with improved husbandry and nutrition of periparturient cows, quickly started to move reproductive efficiency of lactating dairy cows to an upward trend that continues today. Automation has been adopted in Israel and European countries for decades, but only recently have these automated systems been more widely adopted in the USA. The selection of dairy cattle based on genetic indexes that result in positive fertility traits (e.g. daughter pregnancy rate) is positively associated with follicular growth, resumption of ovarian cycles postpartum, body condition score and insulin-like growth factor 1 concentration postpartum, and intensity of oestrus. Collectively, these positive physiological characteristics result in improved reproductive performance. Through the use of automated monitoring devices (AMD), it is possible to identify cows that resume cyclicity sooner after calving and have more intense oestrus postpartum, which are generally cows that have a more successful periparturient period. Recent experiments have demonstrated that it may be possible to adopt targeted reproductive management, utilising ovulation synchronisation protocols for cows that do not have intense oestrus postpartum and relying more heavily on insemination at AMD-detected oestrus for cows that display an intense oestrus postpartum. This strategy is likely to result in tailored hormonal therapy that will be better accepted by the public, will increase the reliance on oestrus for insemination, will improve comfort and reduce labour by reducing the number of injections cows receive in a lactation, and will allow for faster decisions about cows that should not be eligible for insemination.