Pregnancy loss in beef cattle: A meta-analysis

Pregnancy loss in beef cattle causes both management and economic challenges to a producer. A meta-analysis was conducted to quantify reproductive failures that occur during fertilization, early embryonic development, and late embryonic/early fetal development periods of gestation in beef cattle. The meta-analysis included more than 56,000 diagnostic records in 159 studies from 48 papers with 12 studies included in fertilization and pre- blastocyst loss analysis (FERT; days 1-7 of gestation), 107 in early embryo (EEM; days 7-32), and 40 in late embryo/early fetal period (LEF; days 32-100) analysis. Although fertilization rates are reportedly high in beef cattle, significant developmental failure occurs within the first 7 days of gestation. Approximately 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. By the conclusion of the first month of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant. Overall, LEF between days 32-60 and 100 was 5.8 %. Bos indicus animals had greater (P =  0.001) EEM compared to Bos taurus, but there was no difference (P =  0.39) for the LEF period between subspecies. Primiparous cows had greater EEM (P =  0.002) compared to nulliparous heifers and multiparous cows; and nulliparous heifers had a greater LEF compared to primiparous and multiparous cows (P =  0.048). Collectively, these cumulative findings provide a baseline assessment of pregnancy loss specific to beef cattle.

Estrous expression during a fixed-time artificial insemination protocol enhances development and interferon-tau messenger RNA expression in conceptuses from Bos indicus beef cows

Expression of estrus (EST) near the time of fixed-time artificial insemination (FTAI) increases pregnancy success in beef females. This outcome has been associated with improved pregnancy establishment and maintenance, although research is still warranted to validate this theory. Hence, this experiment compared ovarian, uterine and conceptus factors associated with pregnancy establishment in Bos indicus beef cows according to estrous expression during a FTAI protocol. One hundred lactating multiparous Nelore cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device on day -11, a 12.5 mg injection of prostaglandin F2α on day -4, P4 device removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of equine chorionic gonadotropin on day -2, and FTAI on day 0. An estrous detection patch was attached to the tailhead of each cow on day -2, and estrous expression was defined as removal of >50% of the rub-off coating from the patch at FTAI. Overall, 39 cows expressed EST, 55 did not express EST (NOEST), and six cows lost their patch and were discarded from the experiment. Ovarian ultrasonography was performed at FTAI, and on days 7 and 15 of the experiment. Blood samples were also collected on days 7 and 15. Only cows without a corpus luteum (CL) on day 0, and with a CL on days 7 and 15 remained in the experiment (EST, n=36; NOEST, n=48). On day 15, cows were randomly selected within each group (EST, n=29; NOEST, n=30) for conceptus collection via transcervical flushing, followed by endometrial biopsy in the uterine horn ipsilateral to the CL. Within cows not assigned to conceptus collection, blood samples were collected for whole blood RNA extraction (day 20) and pregnancy status was verified by transrectal ultrasonography (day 30). Diameter of dominant follicle on day 0 and plasma P4 concentrations on day 7 were greater (P⩽0.02) in EST v. NOEST cows. Conceptus length and messenger RNA (mRNA) expression of prostaglandin E synthase and interferon-tau were greater (P⩽0.04) in EST v. NOEST cows. Moreover, EST cows diagnosed as pregnant on day 30 had greater (P<0.01) blood mRNA expression of myxovirus resistance 2 on day 20 compared with NOEST. In summary, estrous expression near the time of FTAI enhanced pregnancy establishment factors in B. indicus cows, including conceptus development and mRNA expression of interferon-tau.

Association of concentrations of beta-carotene in plasma on pregnancy per artificial insemination and pregnancy loss in lactating Holstein cows

The objective of this study was to determine the association of beta-carotene concentration in plasma at the moment of artificial insemination (AI) on pregnancy/AI in lactating Holstein cows. A total of 399 events from 364 lactating Holstein cows were enrolled in the trial (143 primiparous and 221 multiparous). All cows were assigned to a timed AI protocol based on estradiol and progesterone. Blood samples were collected at the moment of AI and at 24 and 31d post-AI (samples on 31 d post-AI were collected only from cows that were diagnosed pregnant). The BCS were recorded at the time of AI. Plasma beta-carotene was quantified from blood samples taken at the time of AI using a single step denaturation and extraction into a solvent, followed by measurement using a portable spectrophotometer. Pregnancy-associated glycoproteins (PAG) were analyzed in blood samples taken at 24 and 31 d post-AI of pregnant cows. Milk production was collected for the entire experimental period. Pregnancy diagnosis was performed by ultrasound 31 and 60 d post-AI. Data was analyzed using the MIXED and GLIMMIX procedures of SAS. Cows classified as thin (<2.75) tended to have lower concentration of beta-carotene at AI when compared with those classified as Moderate (≥3.00; 3.8 ± 0.1 vs. 4.3 ± 0.1 μg/mL; P = 0.09). Concentration of beta-carotene were greater in multiparous compared with primiparous (P < 0.01). There was no correlation between concentration of beta-carotene and milk production (r = 0.04; P = 0.10). When plasma beta-carotene was categorized in quartiles, cows in the 1st quartile had lower pregnancy/AI and higher pregnancy losses when compared with cows that were in the 2nd, 3rd and 4th quartile (pregnancy/AI = 19.2 ± 4.5, 33.7 ± 4.7, 36.9 ± 5.0 and 39.8 ± 5.4%, respectively; P = 0.05; pregnancy losses = 41.9 ± 4.8, 20.4 ± 3.7, 22.1 ± 4.1, and 15.7 ± 4.2%, respectively; P < 0.05). There was no association between concentrations of beta-carotene at AI and PAG at 24 d post-AI (P = 0.60). Cows with greater concentrations of beta-carotene at AI were more likely to have greater concentrations of PAG at 31 d post-AI (P < 0.01). In conclusion, the concentration of beta-carotene at AI was affected by BCS and parity. Cows with higher concentrations of plasma beta-carotene at AI had greater pregnancy/AI, lower pregnancy losses and greater concentrations of PAG at d 31 post-AI, suggesting it may be associated with placental function in lactating dairy cows.

Using pregnancy associated glycoproteins (PAG) for pregnancy detection at day 24 of gestation in beef cattle

The objective of this experiment was to determine if circulating concentrations of pregnancy associated glycoproteins (PAG) on day 24 of gestation can be utilized to diagnose pregnancy and embryo viability in beef cattle. Postpartum beef cows (n = 677) and heifers (n = 127) were exposed to a 7-day CO-Synch + CIDR estrus synchronization protocol followed by fixed-time AI (FTAI) on day 0. Blood samples were collected at day 24 after TAI to assess circulating concentrations of PAG utilizing an in-house ELISA. Pregnancy diagnosis was performed 30 and 100 days after FTAI via transrectal ultrasonography. Mean circulating PAG concentration at day 24 differed (P < 0.001) between animals diagnosed pregnant and non-pregnant at day 30 (1.69 ± 0.10 ng/mL vs 0.30 ng/mL ± 0.07 ng/mL; mean ± SEM; respectively). Pregnant heifers had increased PAG concentration at day 24 compared with pregnant cows (P < 0.01; 3.29 ± 0.36 ng/mL vs 1.39 ± 0.10 ng/mL, respectively). Based on receiver operating characteristic (ROC) curve analysis, serum concentration of PAG at day 24 ≥ 0.33 ng/mL in cows and ≥0.54 ng/mL in heifers was 95% accurate at determining pregnancy status at day 30. Heifers that experienced late embryonic mortality between day 30 and 100 of gestation had decreased circulating concentrations of PAG on day 24 (2.02 ng/mL ± 0.73) compared with heifers that maintained an embryo until day 100 (3.69 ng/mL ± 0.39; P = 0.02). However, there was no difference in day 24 PAG concentration (P = 0.39) between cows that maintained or lost a pregnancy (1.31 ng/mL ± 0.25 vs 0.92 ng/ml ± 0.50). In summary, circulating PAG concentration on day 24 of gestation may be a useful marker for early pregnancy detection in beef cattle, and might be a potential marker for predicting embryonic loss.

Pregnancy associated glycoproteins (PAGs) and pregnancy loss in high vs sub fertility heifers

Reproductive inefficiency and infertility are major financial burdens to domestic livestock. Variables associated with these reproductive losses during early gestation include contributions from the oocyte, uterus, sperm, embryo and placenta. Bovine pregnancy associated glycoproteins (PAG) are produced by the binucleate cells of the ruminant placenta and can be used to diagnose pregnancy. Increased circulating concentrations of PAG early in gestation have been correlated with pregnancy success and decreased concentrations are predictive of impending embryonic mortality in both beef and dairy cattle. The objectives of the current study were to determine whether: 1) heifer fertility status is associated with circulating concentrations of PAG and pregnancy loss; and 2) PAG concentrations within the same animal are repeatable across multiple pregnancies. We hypothesized maternal PAG concentrations would be increased in high fertility compared to subfertile heifers but not repeatable across subsequent pregnancies in the same heifer. Serial embryo transfer (ET; n = 4 rounds) was used to classify predominately Angus heifers (n = 92) as highly fertile (HF = 30; 100% pregnancy success) or subfertile (SF = 62; average = 33%; range = 25-75% pregnancy success) based on day 28 ultrasound diagnosis. Blood samples were collected at both day 28 and 44 for quantification of circulating PAG concentrations by an in house PAG ELISA with antibodies raised against early secreted PAGs. Pregnancy was terminated at day 44 of gestation and heifers were allowed 30 days recovery before synchronization for the next ET. Only heifers that were diagnosed pregnant by ultrasound were used in this study (HF: n = 30, SF: n = 62). Serum concentrations of PAGs were not different between HF (5.90 ± 0.27 ng/mL) and SF (5.56 ± 0.31 ng/mL; P = 0.16) heifers at day 28 of gestation nor was there a difference at day 44 of gestation (P = 0.32). Subfertile heifers had increased pregnancy loss between days 28 and 44 of gestation. Based on odds ratio analysis, SF heifers had a 2.41 times chance to undergo pregnancy loss between day 28-44 compared to HF heifers (P < 0.05). There was no correlation (P > 0.05) in maternal circulating concentrations of PAG between pregnancies on day 28 or 44 of gestation in samples obtained from HF heifers. In summary, circulating concentrations of PAG are not different between HF and SF heifers; however, HF classified heifers have decreased pregnancy loss between days 28 and 44 of gestation.

Acute and subacute effects of a synthetic kisspeptin analog, C6, on serum concentrations of luteinizing hormone, follicle stimulating hormone, and testosterone in prepubertal bull calves

Kisspeptin (KP) is a neuropeptide integral in regulating puberty and gonadotropin releasing hormone. Compound 6 (C6), a KP analog, is more potent in vitro, has a longer half-life, and may have greater therapeutic applications than KP. To determine the acute and subacute effects of KP and C6 on serum concentrations of luteinizing hormone (LH), follicle stimulating hormones (FSH), and testosterone (T), prepubertal bull calves [12.1 ± 1.1 (SD) weeks of age; 91.2 ± 10.8 kg BW] were assigned to one of three treatment groups [Saline (n = 4), KP (n = 4; 20 nmoles), or C6 (n = 4; 20 nmoles). Treatments were administered intramuscularly once daily for four consecutive days. Blood samples were collected every 15 min for 6 h immediately following treatment administration on Day 1 (acute) and Day 4 (subacute). Serum concentrations of LH, FSH, and T were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment × time interaction during Day 1 (P < 0.0001) and Day 4 (P = 0.02) such that LH concentrations were greatest following administration of C6 (albeit diminished during Day 4). Number of LH pulses were least (P = 0.02) and LH nadirs were highest (P = 0.04) following administration of C6 (P = 0.02). There was no effect of treatment (P = 0.95) or treatment × time interaction (P = 0.10) on serum FSH concentrations during Day 1. During Day 4 FSH concentrations (P = 0.02) and number of FSH pulses (P = 0.02) were least following administration of C6. There was no effect of treatment (P = 0.33), time (P = 0.19) or treatment × time interaction (P = 0.44) on T concentrations. In conclusion, acute and subacute C6 increased LH concentrations and subacute C6 decreased FSH concentrations and pulse parameters. Despite suppression of FSH with subacute daily administration of C6, altered frequency and timing of treatment with KP analogs may have application to affect the onset of puberty in livestock.

Intensity of estrus following an estradiol-progesterone-based ovulation synchronization protocol influences fertility outcomes

The objective of this study was to examine the association between increased physical activity at the moment of timed artificial insemination (AI), detected by an automated activity monitor (AAM), and fertility outcomes. This paper also investigated factors affecting estrous expression in general. A total of 1,411 AI events from 1,040 lactating Holstein cows were recorded, averaging 1.3 ± 0.6 (±standard deviation) events per cow. Activity (measured as steps/h) was monitored continuously by a leg-mounted AAM located on the rear leg of the cow. Ovulation was synchronized by a timed AI protocol based on estradiol and progesterone. Ovarian ultrasonography was performed in all cows on d -11 (AI = d 0) and in a subset of cows on d 0 (n = 588) and d 7 (n = 819) to determine the presence of a corpus luteum and follicles. The body condition score (1 to 5 scale) was assessed on d 0 and a blood sample was collected for progesterone measurement on d 7. Using the AAM, an estrus event was determined when the relative increase (RI) in physical activity of the cow exceeded 100% of the baseline activity. The physical activity was classified as strong RI (≥300% RI), moderate RI (100-300% RI), or no estrus (<100% RI). Milk production was measured daily and averaged between d -11 and 0. Pregnancy was diagnosed at 32 and 60 d post-AI and pregnancy losses were calculated. The mean RI at estrus was 328.3 ± 132.1%. Cows with strong RI had greater pregnancy per AI than those with moderate RI and those that did not express estrus (35.1 vs. 27.3 vs. 6.2%). When including only cows that successfully ovulated after timed AI, those that displayed strong intensity RI still had greater pregnancy per AI than those with moderate intensity RI or those that did not express estrus (45.1 vs. 34.8 vs. 6.2%). Cows expressing strong RI at timed AI had greater ovulation rates compared with moderate RI and cows that did not express estrus (94.9 vs. 88.2 vs. 49.5%). Furthermore, pregnancy losses were reduced in cows with strong RI compared with cows expressing moderate RI (13.9 vs. 21.7%). Cows with a strong RI at estrus were more likely to have a corpus luteum at the beginning of the protocol and had greater concentration of progesterone 7 d post-AI. Multiparous cows expressed lower RI compared with primiparous cows. Cows with lower body condition score tended to have decreased RI at estrus. No correlation between estrous expression and pre-ovulatory follicle diameter was observed. Also, no correlation was observed between milk production at AI and RI. In conclusion, strong intensity RI of estrus events at timed AI was associated with improved ovulation rates and pregnancy per AI, and reduced pregnancy losses. These results provide further evidence that measurements of estrous expression can be used to predict fertility at the time of AI and possibly be used as a tool to assist decision making strategies of reproduction programs.

Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows

This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.

125 Effect of Complexed Trace Minerals on Oocyte and Embryo Production

The objective of this experiment was to evaluate the impact of trace mineral supplementation on reproductive performance in lactating beef cows. Thirty days before AI (Day –30), 68 postpartum cows were stratified by weight, body condition score, and parity before being equally and randomly assigned to either a treatment or a control group. Each group received a weekly mineral supplement allotment of 1.2 kg/week per cow-calf pair for 15 weeks. Cows in the treatment group received a mineral supplement that contained zinc, copper, and manganese amino acid complexes as well as cobalt glucoheptonate (Availa® Plus; Zinpro Corp., Eden Prairie, MN, USA), whereas cows assigned to the control group received a mineral supplement that contained the same concentrations of these trace minerals from inorganic sources. All cows were submitted to a 7-day CO-Synch + CIDR protocol on Day –10 and bred using fixed time AI on Day 0. Pregnancy diagnosis was performed via transrectal ultrasound on Day 28. Cows diagnosed as nonpregnant were then removed from the experiment. Pregnant cows were divided into 10 groups of 3 or 4 cows per group: 5 treatment groups (20 total cows) and 5 control groups (18 total cows). On Day 52 and 67, all pregnant cows were subjected to an ovum pick-up (OPU). Collected oocytes were evaluated before performing in vitro fertilization. Number of oocytes cleaving (dividing into more than one cell) and developing to blastocyst stage was recorded. Analysis of variance was conducted using PROC GLIMMIX (SAS 9.4; SAS Institute Inc., Cary, NC, USA) to determine differences between treatment and control, and group was the experimental unit. Mineral consumption did not differ (P = 0.48) between treatments (average of 1.16 ± 0.065 v. 1.09 ± 0.065 kg/week per cow-calf pair, for treatment and control, respectively). Pregnancy per AI was numerically higher in mineral-supplemented cows versus controls (64.7% v. 52.9%, respectively; P = 0.33). Consumption of the complexed trace mineral supplement increased (P = 0.06) total oocyte yield (22.6 ± 1.44 mean ± SEM v. 16.4 ± 2.04 oocytes/group for treatment and control, respectively). Moreover, groups receiving the complexed trace minerals had more (P = 0.05) culturable oocytes (grades A through C) compared with control groups (15.9 ± 1.6 mean ± SEM v. 11.8 ± 1.01 oocytes/group, respectively). In addition, production of transferable embryos (grades 1 through 3) was greater (P = 0.04) for groups receiving complexed trace minerals than inorganic trace minerals (4.2 ± 0.64 mean ± SEM v. 2.6 ± 0.65 embryos/group, respectively). In summary, supplementing with zinc, manganese, and copper amino acid complexes plus cobalt glucoheptonate improved oocyte production and embryo development in pregnant beef cows when compared with cows supplemented with inorganic forms of these trace minerals.

Lowering rumen-degradable and rumen-undegradable protein improved amino acid metabolism and energy utilization in lactating dairy cows exposed to heat stress

The objective of this study was to evaluate the effects of reducing dietary rumen-degradable protein (RDP) and rumen-undegradable protein (RUP) on protein and energy metabolism in heat-stressed dairy cows. Eighteen primiparous and 30 multiparous mid-lactation Holstein cows were used in a completely randomized design arranged in a 2 × 2 factorial (n = 12/treatment). Cows were randomly assigned to 1 of 4 dietary treatments that included 2 levels of RDP (10 and 8%; D) and 2 levels of RUP (8 and 6%; U) of dry matter for 21 d as (1) 10D:8U, (2) 8D:8U, (3) 10D:6U, and (4) 8D:6U. Diets were isoenergetic and contained 50% forage and 50% concentrate (dry matter basis). Cows were housed in a freestall barn. Three weeks before start of treatments, all animals were fed the 10D:8U diet and received supplemental cooling to prevent heat stress. During the treatment period, cows experienced a daily increment in temperature-humidity index from 74 to 82 for 1000 to 2000 h. Blood samples were collected on d -1 and 21 of the treatment period to determine plasma concentrations of AA, glucose, insulin, fatty acids, and β-hydroxybutyrate. For primiparous cows, reducing from 10 to 8% RDP decreased insulin concentrations. For multiparous cows, we found significant RDP by RUP interactions for insulin, β-hydroxybutyrate, fatty acids, total essential AA, and 3-methylhistidine concentrations. Reducing from 10 to 8% RDP decreased insulin concentrations at 6% RUP, but concentrations did not change when reducing RDP at 8% RUP. Reducing from 10 to 8% RDP decreased β-hydroxybutyrate concentrations at 8% RUP, but concentrations did not change when reducing RDP at 6% RUP. Reducing from 10 to 8% RDP increased nonesterified fatty acid and total essential AA concentrations at 8% RUP, but concentrations did not change when reducing RDP at 6% RUP. Reducing from 8 to 6% RUP decreased 3-methylhistidine concentration at 8% RDP, but not at 10% RDP. Reducing from 8 to 6% RUP increased milk protein yield efficiency in primiparous and multiparous cows. These results indicate that reducing RDP and RUP lowers circulating insulin, which was associated with mobilization and utilization of fatty acids. Reduced RDP and RUP increases the use of AA to maintain milk protein synthesis and limit AA catabolism in cows exposed to warm climates.

Pregnancy diagnosis in cattle using pregnancy associated glycoprotein concentration in circulation at day 24 of gestation

Cattle producers are limited to day 28-30 of gestation as the earliest time point for accurate pregnancy diagnosis due to the effectiveness of ultrasound and chemical based methods, including commercially available pregnancy associated glycoproteins (PAG) tests. The objective of the current studies were to determine if early gestation circulating PAG concentrations at day 24 could be used to diagnose pregnancy in dairy cattle undergoing embryo transfer. In vitro produced embryos were transferred into Holstein x Gir cows and heifers on day 7 following ovulation. Study 1 utilized only cows (n = 101) determined to be pregnant on day 24 of gestation by progesterone concentration, as well as CL and PAG presence. In study 2, animals were not predetermined to be pregnant and both heifers (n = 111) and cows (n = 242) were used. In both studies, blood was collected at day 24 for PAG analysis as well as day 31. Final pregnancy confirmation occurred on day 60 via transrectal ultrasonography. Serum PAG concentrations were quantified using an in house PAG ELISA. Following timed embryo transfer (TET) in study 1, of the 101 cows diagnosed as pregnant on day 24, 80 cows were identified as still pregnant on day 31 of gestation (77%). Study 2 had a pregnancy rate at day 31 of 33.7% of total embryos transferred. Mean circulating PAG concentration at day 24 differed (P < 0.001) between animals diagnosed pregnant and non-pregnant at day 31 in both studies (study 1, 2.964 ± 0.262 ng/mL vs 0.946 ± 0.168 ng/mL and study 2, 1.962 ± 0.261 ng/mL vs 0.731 ± 0.109 ng/mL). Concentration of PAG between pregnant and non-pregnant cows in study 1 and 2 was significant, however, pregnant heifers in study 2 (1.562 ± 0.266 ng/mL) had concentration of PAGs that only had a tendency to differ compared to non-pregnant heifers (non-pregnant, 0.799 ± 0.290 ng/mL; P = 0.0669). Only animals that were pregnant at day 31 were analyzed in late embryo mortality analysis (heifers, n = 54; cows, n = 159), defined as pregnancy loss between day 31 and 60. Between day 31 and 60, 39 (12 in study 1 and 28 in study 2) animals experienced late embryo mortality. Circulating concentrations of PAG were not significantly different (P > 0.05), in either study, at day 24 of gestation in animals that maintained pregnancy until day 60 compared to animals that lost pregnancy between day 31 and 60 (late embryo mortality, LEM). In summary, early gestation circulating PAG concentration may have application in diagnosing pregnancy at day 24 of gestation and more work is needed to determine the potential of early gestation PAGs in predicting embryo loss in dairy.