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

Advances in Timed Artificial Insemination: Integrating Omics Technologies for Enhanced Reproductive Efficiency in Dairy Cattle

Reproductive efficiency is crucial for dairy farm productivity, but achieving consistent fertility remains challenging. TAI improves pregnancy rates by synchronizing ovulation and enabling precision breeding. Despite the advancements in hormone synchronization protocols, outcomes vary due to genetic, physiological, and metabolic differences among cows. This review examines current TAI protocols, including gonadotropin-releasing hormone (GnRH)-based and estradiol/progesterone (P4)-based synchronization methods, emphasizing their effectiveness and practical limitations. We also examined how to integrate emerging omics technologies, such as genomics, transcriptomics, proteomics, and metabolomics, into TAI protocols, marking a significant shift in reproductive management. These tools unveil molecular biomarkers that enable the precise tailoring of TAI protocols to the genetic, metabolic, and physiological profiles of individual animals, addressing challenges in variable fertility responses. Key factors influencing TAI success, such as animal health, environment, and insemination timing, are explored. This review identifies gaps in the existing literature, such as the integrated omics methodologies and data integration across platforms, and proposes a framework for future research to refine TAI protocols to address genetic variability and apply omics technologies to identify validated biomarkers for early pregnancy detection, which will significantly enhance the practical impact of TAI. Future directions highlight the need for interdisciplinary approaches combining molecular insights with robust on-farm applications to improve fertility outcomes and reduce reliance on blanket synchronization methods. By combining traditional synchronization methods with cutting-edge molecular tools, TAI offers promising opportunities for improving reproductive efficiency and sustainability in dairy farming.

Targeted reproductive management for lactating Holstein cows: Reproductive and economic outcomes of Double-Ovsynch compared with a targeted approach based on resumption of estrus

Accessibility to automated monitoring devices (AMD) has led to exploration of alternative reproductive management to ovulation synchronization protocols (OvSP) for first postpartum AI according to the cow's early postpartum estrus characteristics (EPEC). We hypothesized that pregnancy and economic outcomes of cows subjected to a targeted reproductive management (TRM) are not inferior to those of cows subjected to an OvSP for the first AI. This was a noninferiority, randomized clinical trial. Cows (n = 2,635) from one dairy were fitted with AMD and classified according to EPEC at 45 ± 3 DIM as estrual (high intensity AMD-detected estrus [primiparous: heat index ≥90, multiparous: heat index ≥70; 0 = minimum, 100 = maximum]) and anestrus (no estrus or low intensity estrus). Cows in the control treatment were enrolled in the Double-Ovsynch (GnRH on d -27, PGF2α on d -20, GnRH on d -17 and -10, PGF2α on d -3 and -2, GnRH on d -1, and timed AI [TAI] on d 0 at 73 ± 3 DIM). Anestrus cows enrolled in the TRM treatment were assigned to the hCG-Ovsynch (TRM1; hCG on d -17, GnRH on d -10, PGF2α on d -3 and -2, GnRH on d -1, and TAI on d 0 at 73 ± 3 DIM). Estrual cows received PGF2α at 60 to 73 DIM, when they were 6 to 22 d after a previous estrus, and if not inseminated in estrus within 7 d, were enrolled in the hCG-Ovsynch at 70 to 77 DIM (TRM2). Estrual cows in the TRM treatment that were ≥23 d from a previous estrus at 63 ± 3 DIM were enrolled in the hCG-Ovsynch at 63 ± 3 DIM and received TAI at 80 ± 3 DIM (TRM3). Pregnancy was diagnosed 32 ± 3 and 67 ± 3 d after AI. Cows were re-inseminated at AMD-detected estrus or at fixed time within 10 d after nonpregnancy diagnosis. The lactation gross profit was calculated as follows: (milk income + sale value + subsequent lactation calf value) - (rearing cost + feed cost + replacement cost + fixed cost + depreciation + reproductive management cost). Cows in the control treatment were more likely to be diagnosed pregnant 67 d after AI (control = 53.9% [95% CI = 51.1%, 56.6%]; TRM = 50.1% [95% CI = 47.2%, 53.0%]), independent of EPEC. The interaction between treatment and EPEC tended to affect the hazard of pregnancy throughout the lactation (control = referent; anestrus-TRM: adjusted hazard ratio = 1.01, 95% CI = 0.91, 1.13; estrual-TRM: adjusted hazard ratio = 0.83, 95% CI = 0.74, 0.94). Treatment did not affect gross profit, independent of EPEC (control = US$2,196.9 ± 25.6; TRM = US$2,221.9 ± 26.5). Alternative strategies for first postpartum AI according to a cow's EPEC may be possible with AMD, without affecting gross profit. The use of a single hCG treatment to presynchronize the estrous cycle of anestrus cows may be an alternative to the presynchronization with the Ovsynch protocol because despite slightly decreasing P/AI, it did not affect gross profit.

Ovarian function and endocrine phenotypes of lactating dairy cows during the estrous cycle are associated with genomic-enhanced predictions of fertility potential

The objectives of this prospective cohort study were to characterize associations among genomic merit for fertility with ovarian and endocrine function and the estrous behavior of dairy cows during an entire nonhormonally manipulated estrous cycle. Lactating Holstein cows entering their first (n = 82) or second (n = 37) lactation had ear-notch tissue samples collected for genotyping using a commercial genomic test. Based on genomic predicted transmitting ability values for daughter pregnancy rate (gDPR), cows were classified into high (Hi-Fert; gDPR > 0.6, n = 36), medium (Med-Fert; gDPR -1.3 to 0.6, n = 45), and low fertility (Lo-Fert; gDPR < -1.3, n = 38) groups. At 33 to 39 DIM, cohorts of cows were enrolled in the Presynch-Ovsynch protocol for synchronization of ovulation and initiation of a new estrous cycle. Thereafter, the ovarian function and endocrine dynamics were monitored daily until the next ovulation by transrectal ultrasonography and concentrations of progesterone (P4), estradiol, and FSH. Estrous behavior was monitored with an ear-attached automated estrus detection system that recorded physical activity and rumination time. Overall, we observed an association between fertility group and the ovarian and hormonal phenotype of dairy cows during the estrous cycle. Cows in the Hi-Fert group had greater circulating concentrations of P4 than cows in the Lo-Fert group from d 4 to 13 after induction of ovulation and from day -3 to -1 before the onset of luteolysis. The frequency of atypical estrous cycles was 3-fold greater for cows in the Lo-Fert than the Hi-Fert group. We also observed other modest associations between genomic merit for fertility with the follicular dynamics and estrous behavior. We found several associations between milk yield and parity with ovarian, endocrine, and estrous behavior phenotypes as cows with greater milk yield and in the second lactation were more likely to have unfavorable phenotypes. These results demonstrate that differences in reproductive performance between cows of different genomic merit for fertility classified based on gDPR may be partially associated with circulating concentrations of P4, the incidence of atypical phenotypes during the estrous cycles, and, to a lesser extent, the follicular wave dynamics. The observed physiological and endocrine phenotypes might help explain part of the differences in reproductive performance between cows of superior and inferior genomic merit for fertility.

Reproductive physiological outcomes of dairy cows with different genomic merit for fertility: biomarkers, uterine health, endocrine status, estrus features, and response to ovarian synchronization

Our overarching objective was to characterize associations between genomic merit for fertility and the reproductive function of lactating dairy cows in a prospective cohort study. In this manuscript, we present results of the association between genomic merit for fertility and indicators of metabolic status and inflammation, uterine health, endocrine status, response to synchronization, and estrous behavior in dairy cows. Lactating Holstein cows entering their first (n = 82) or second (n = 37) lactation were enrolled at parturition and fitted with an ear-attached sensor for automated detection of estrus. Ear-notch tissue samples were collected from all cows and submitted for genotyping using a commercial genomic test. Based on genomic predicted transmitting ability values for daughter pregnancy rate (gDPR) cows were classified into a high (Hi-Fert; gDPR > 0.6; n = 36), medium (Med-Fert; gDPR -1.3 to 0.6; n = 45), and low (Lo-Fert; gDPR < -1.3; n = 38) group. At 33 to 39 d in milk (DIM), cohorts of cows were enrolled in the Presynch-Ovsynch protocol for synchronization of estrus and ovulation. Body weights, body condition scores (BCS), and uterine health measurements (i.e., vaginal discharge, uterine cytology) were collected from parturition to 60 DIM and milk yield was collected through 90 DIM. Blood samples were collected weekly through 3 wk of lactation for analysis of β-hydroxybutyrate, nonesterified fatty acids, and haptoglobin plasma concentrations. Body weight, BCS, NEFA, BHB, and Haptoglobin were not associated with fertility groups from 1 to 9 wk after parturition. The proportion of cows classified as having endometritis at 33 to 36 DIM tended to be greater for the Lo-Fert than the Hi-Fert group. The proportion of cows that resumed cyclicity did not differ at any time point evaluated and there were no significant associations between probability or duration and intensity of estrus with fertility group. Cows of superior genetic merit for fertility were more likely to ovulate, have a functional CL, have greater circulating P4, and have larger ovulatory size than cows of inferior fertility potential at key time points during synchronization of estrus and ovulation. Despite observing numerical differences with potential performance consequences for the proportion of cows that responded to synchronization of ovulation and were both cyclic and responded to the Ovsynch portion of the synchronization protocol, we did not observe significant differences between fertility groups. Although not consistent and modest in magnitude, the collective physiological and endocrine differences observed suggested that cows of superior genetic fertility potential might have improved reproductive performance, at least in part, because of modestly improved endocrine status, uterine health, and ability to ovulate.

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.