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This experiment investigated the effects of diet composition on rumen, vaginal, and uterine microbiota of beef heifers. Fifteen rumen-cannulated, pubertal Angus-influenced heifers were used in a replicated 3 × 3 Latin square design (28-d periods and 21-d washout intervals). Dietary treatments included diets based on (as-fed) 100% grass hay (HF), 60% grass hay + 40% corn-based concentrate (INT), or 25% grass hay + 75% corn-based concentrate (HG). Treatments were offered individually to heifers once daily at 2% body weight. Rumen, vaginal, and uterine samples were collected on days 0 and 28 of each period. Data were analyzed using orthogonal contrasts (linear and quadratic), using results from day 0 as independent covariates and heifer as the experimental unit. Ruminal pH on day 28 decreased linearly (P0.01) as concentrate inclusion increased. Uterine and vaginal pH on day 28 were not affected by treatments (P ≥ 0.35). Within the rumen samples, Bacteriodetes was the most abundant phylum and its relative abundance linearly decreased (P ≤ 0.01) with the inclusion of concentrate. Prevotella was the most abundant genus within the rumen but was not affected by treatments (P ≥ 0.44). Genera with relative abundance ≥1% (average across treatments) in the rumen that were impacted by treatments (P ≤ 0.01) included Bacteroides, Pedobacter, Dysgonomonas, Caloramator, and Ruminococcus. Firmicutes was the most abundant phylum in the vagina and uterus, but it was unaffected by treatments (P ≥ 0.16). Prevotella was the most abundant genus in the vagina, and its relative abundance increased (P0.01) with the inclusion of concentrate. Other genera with relative abundance ≥1% that were significantly affected (P ≤ 0.05) by treatments were Clostridium, Pedobacter, Roseburia, Oscillospira, Faecalibacterium, Caloramator, Paludibacter, Rhodothermus, and Porphyromonas. In uterine samples, Prevotella was the most abundant genus but was unaffected by treatments (P ≥ 0.29). Genera with relative abundance ≥1% in the uterus that were significantly affected (P0.01) by treatments were Caloramator, Paludibacter, and Thalassospira. Collectively, inclusion of concentrate in the diet altered the bacterial composition within the rumen as well as shifting bacterial populations within the vagina and uterus. Research is warranted to further understand the impacts of these diet-induced microbiota changes on reproductive function and performance of beef heifers.According to the United Nations, worldwide beef production must increase by 120% by 2050 to feed an additional 2.3-billion people. With a growing population and a reduction in available resources, the overall efficiency of beef production needs to advance to meet the increasing demand. Cow–calf operations serve as the foundation of the beef industry and supply all calves for beef production; however, poor reproductive performance limits the productivity in this system. Hence, management strategies to promote reproductive success are warranted for optimal reproductive and overall efficiency in cow–calf operations. Bacterial communities in the reproductive system of cattle have been shown to contribute to fertility and can be affected by several factors such as dietary changes. The objective of this experiment was to evaluate the impact of different diets on the reproductive bacterial communities. Overall, it was concluded that the reproductive tract can shift the abundance of bacteria due to changes in the diet, and more research is needed to better understand the impact of these changes and their consequences to beef production systems.

The objective of this study was to evaluate transcriptomic differences in reproductive tissues of beef heifers with high vs. low PAG concentrations carrying viable pregnancies during the attachment and early placentation periods. Bos indicus beef heifers (n=25) were subjected to embryo transfer on day 7 with IVP embryos, and pregnancies were confirmed at slaughter. Heifers were harvested on days 25 (n=8) and 36 (n=8), and samples from endometrium (END) and trophectoderm (TE) were collected for RNA isolation using a commercial extraction kit (QIAGEN; Hilden, Germany). Plasma concentrations of PAGs were determined via validated ELISA and the females were classified in groups of high and low PAG (6.8±0.7 (n=4) vs. 0.8±0.7 (n=4) ng/mL on D25 and 15±2.1 (n=5) vs. 4±1.2 (n=3) ng/mL on D36; P< 0.05). An Illumina platform was utilized for RNA sequencing. Differentially expressed genes between groups and by tissue were determined using edge-R package from R. Gene ontology analyses revealed a down regulation of processes associated with embryonic and placenta development on D36 in both TE and END for the low PAG group. On D25 and D36, markers of attachment, ECM remodeling and invasion were significantly upregulated in the TE, but not in the END of the low PAG pregnancies. PAG genes were not differentially expressed between groups. In conclusion, heifers with low PAG in peripheral circulation have significantly different gene expression profiles in the developing conceptus and endometrium. The results suggested abnormal maternal-conceptus interactions initiated on D25, which may have resulted in poor embryonic and placenta development on D36. Disturbances at the maternal-conceptus interface could be impairing PAGs from reaching the maternal peripheral circulation, since no differences in PAG genes were found between PAG groups. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2017-67015-26457 from the USDA National Institute of Food and Agriculture.

Shifts in commensal bacteria (i.e., Firmicutes) in the human microbiome are associated with compromised fertility. The objectives of this study were to characterize 1) the reproductive microbiome and 2) the cytokine concentrations prior to artificial insemination (AI) in vaginal and uterine flushes from postpartum beef cows. Twenty Bos indicus-influenced beef cows (~60 days postpartum and free of health issues) were weighed, body condition scored (BCS) then subjected to the Bee Synch II synchronization protocol on d-8 and timed AI on d0. Blood samples were collected on d-3, -1, 0, and 28. Vaginal and uterine flushes were collected on d-3 and d-1. On d28, pregnancy was determined by transrectal ultrasonography (Open, n=13 and Pregnant, n=7). Bacterial community analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. Cytokine analyses were conducted using the RayBiotech Quantibody® Bovine Cytokine Array Q1 kit per manufacturer's instructions. Weight, BCS, and vaginal bacterial communities by phyla were not different (P >0.05). In open cows, the uterine relative abundance of Firmicutes decreased between d-3 and -1 (60.4% ± 0.9% vs. 48.5% ± 3.2%, respectively; P< 0.05). In pregnant cows, the uterine relative abundance of Tenericutes significantly increased between d-3 and -1 (1.0% ± 0.1% vs. 7.6% ± 4.1%, respectively; P< 0.05). Additionally, the genus Ureaplasma tended to increase in relative abundance from d-3 to -1 (0.1% ± 0.1% vs. 7.3% ± 4.9%, respectively; P=0.06). Uterine concentrations of Interferon (IFN)-γ, Interleukin (IL)-1α and IL-21 were greater in open females compared to pregnant. Vaginal concentrations for IFN-α and chemokine ligand (CXCL)-10 were greater in open females compared to pregnant. Regardless of treatment, IL-13 increased from d-3 to d-1. These results suggest a distinct difference in the uterine microbiome and cytokine profiles prior to AI for resulting pregnant and open cows.

Cytokines have a vital role in reproductive immune environment during the postpartum period. Previous data evaluated uterine and vaginal cytokine concentrations prior to insemination; however, was unable to correlate these data with plasma cytokine concentrations. The objective of this study was to determine relationships between uterine, vaginal, and plasma pro- and anti-inflammatory cytokine concentrations in postpartum beef cows prior to timed artificial insemination (TAI). Bos indicus-influenced beef cows (n=20) free of any physical, health or reproductive-related issues were subjected to the Bee Synch II protocol 8 days prior (d-8) to TAI (d0). Uterine and vaginal flushes and blood were collected on d-3 and d-1. Pregnancy was determined by transrectal ultrasonography on d28 (Pregnant, n=7; Open, n=13). Using the RayBiotech Quantibody Bovine Cytokine Array 1 the following cytokines concentrations were determined: interferon (IFN)-α, IFN-γ, interleukin (IL)-13, IL-1α, IL-1-F5, IL-21, tumor necrosis factor (TNF)-α, chemokine ligand (CXCL)-9, CXCL-10, and chemokine ligand 4 (CCL4). Concentration data were analyzed using PROC GLM and correlations using Pearson correlation in SAS. For plasma samples, 8 pro-inflammatory cytokines (IFN-α, IFN-γ, IL-13, IL-1α, IL-1-F5, IL-21, CXCL-9, and TNF-α) had greater (P< 0.05) concentrations in open cows compared with pregnant cows. For uterine flushes, 3 pro-inflammatory cytokines (IFN-γ, IL-1α, and IL-21) had greater (P< 0.05) concentrations in open cows compared with pregnant cows. For vaginal flushes, IFN-α concentrations were greater (P< 0.05) in open cows, while CXCL-10 concentrations were greater in pregnant cows. There were no significant correlations between plasma and uterine or vaginal samples (P>0.05). Interestingly, for open cows there were correlations for IFN-α (r=0.46; P=0.02), IFN-γ (r=0.58; P=0.002), and IL-21 (r=0.54; P=0.004) between uterine and vaginal samples; however, no correlations were observed for pregnant cows. These results suggest a greater abundance of pro-inflammatory cytokines within the uterus, vagina, and in peripheral circulation for resulting open cows prior to TAI.

The objective of this study was to evaluate the use of luteal color doppler (CD) ultrasonography and plasma concentrations of pregnancy-associated glycoproteins (PAG) for early pregnancy diagnosis in Bos taurus beef cows. Additionally, CD and PAG were evaluated as potential predictors of late embryonic/early fetal mortality (LEM). Postpartum beef cows (n = 212) were exposed to estrus synchronization followed by fixed-time artificial insemination (day 0). On days 20 and 22, B-mode and CD ultrasonography were performed to evaluate corpus luteum (CL) morphometries and blood perfusion. Moreover, blood samples were collected on days 25 and 29 to quantify circulating concentrations of PAG. Conventional ultrasonography on days 29 and 100 was utilized as the gold-standard method for pregnancy diagnosis. Cows that experienced pregnancy loss between days 29 and 100 were classified as LEM. Pregnant cows had larger and more vascularized CL compared with nonpregnant cows on days 20 and 22 (P0.001 for all response variables). Accuracy for CD on days 20 and 22 were 87% and 92%, respectively. Accuracy for PAG on days 25 and 29 were 84% and 99%, respectively. No false negative (FN) results were observed for CD on both days 20 and 22; however, there were 7.1% FN results for PAG on day 25. Cows that experienced LEM had decreased (P = 0.04) circulating PAG on day 29 of gestation compared with cows that maintained pregnancy; however, there were no differences in luteal blood perfusion on days 20 and 22 (P ≥ 0.53) or circulating PAG on day 25 (P = 0.46) between LEM cows and cows that maintained pregnancy. Sensitivity and specificity of PAG on day 29 as predictors of LEM were 83% and 77%, respectively. In conclusion, CD resulted in accurate pregnancy diagnosis in B. taurus beef cows on both days 20 and 22 of gestation, while having no FN results. Circulating concentrations of PAG were decreased in cows that experienced LEM; however, further research is required to utilize PAG as a predictor of LEM commercially.Early pregnancy detection allows cattle producers to increase reproductive efficiency. Pregnancy failures associated with embryonic mortality represents an economic burden to the beef production industry. The present study evaluated the use of color doppler (CD) ultrasonography of specific ovarian structures and pregnancy-associated glycoproteins (PAG) in plasma as potential alternatives to diagnose pregnancy earlier than industry-standard methods in beef cows with Bos taurus genetics. Additionally, the present study evaluated the use of these methods to predict embryonic mortality during early gestation. The results of the present study indicate that: 1) CD can accurately recognize most nonpregnant cows with B. taurus genetics as early as 20 days after breeding. 2) Plasma concentrations of PAG resulted in suboptimal accuracy on day 25 of gestation. 3) Cows that undergo pregnancy loss between 29 and 100 d after breeding have decreased concentrations of PAG in their circulation on day 29, even though they were identify as pregnant with ultrasonography on the same day. 4) Both blood concentrations of PAG and luteal blood perfusion estimated by CD failed to accurately predict pregnancy loss.

We aimed to compare the abundance of interferon-tau stimulated genes (ISG) transcripts in peripheral blood leukocytes of artificially inseminated beef cows using real-time quantitative PCR (RT-qPCR) versus Droplet Digital PCR (ddPCR). Multiparous Bos taurus beef cows (n = 7) were subjected to timed artificial insemination (TAI) on day 0. Pregnancy was determined by transrectal ultrasonography on days 26 and 30 post-TAI, and cows were classified as: pregnant (n=4; embryo detected on days 26 and 30) or non-pregnant (n = 3; no embryo detected). Coccygeal vein blood samples were collected on days 0, 15, 17, 19, 20 and 24 post-TAI. Leukocyte RNA was extracted from the buffy coat fraction using Trizol associated with the DirectZol-RNA kit and transcribed to cDNA. The abundance of ISG (ISG15 and MX2) was assessed by relative quantification to a reference gene (RPS9) using RT-qPCR and by absolute quantification using the QX100TM Droplet DigitalTM PCR System (Bio-rad Laboratories) according to manufacturer’s recommendations. Data were analyzed using PROC MIXED on SAS 9.4. For the RT-qPCR, pregnant cows had greater (P < 0.05) ISG15 and MX2 abundance compared to non-pregnant cows on days 20 (ISG15:0.11±0.1 vs. 0.01±0.001 and MX2:0.73±0.4 vs. 0.06±0.06) and 24 (ISG15:0.34±0.2 vs. 0.01±0.001 and MX2:0.77±0.2 vs. 0.13±0.04). For ddPCR, a greater ISG15 and MX2 copy numbers in pregnant cows was observed on days 15 (ISG15:129 vs. 44 copies/µl and MX2:33 vs. 10 copies/µl) and 20 (ISG15: 216 vs. 30 copies/µl and MX2: 44 vs. 7 copies/µl), and also on day 24 for ISG15 (32 vs. 7 copies/µl) compared to non-pregnant cows. In conclusion, ddPCR was able to detect an earlier expression of ISG in pregnant cows. Future studies are needed to enroll more animals and establish a suitable cutoff value using ddPCR, which could be less subjective for diagnosis as it does not require the use of a reference gene.

The aim of this study was to investigate the ovarian response of Brahman cows submitted to two different estrus synchronization protocols and to determine the estrus response and ovulation time. A total of 153 Brahman cows were randomly assigned to receive one of the following estrus synchronization protocols: 1) CIDR insert and an injection of prostaglandin F2α (25 mg, PGF) on Day -5 and CIDR removal with PGF on Day 0 (CIDR5; n = 77); 2) CIDR insert on Day -12 and an injection of PGF on Day -12, Day -5 and Day 0 upon CIDR removal (CIDR12; n = 76). Estrotect breeding indicator patches were placed on Day 0 and cows were artificially inseminated (AI) 12h after estrus detection; cows not detected in estrus after 96h received TAI coupled with 100 µg of GnRH. Ovarian dynamics were observed during the protocol and follicular diameter were measured every 12h after AI until ovulation. Cows synchronized with CIDR12 had increased follicular diameter (CIDR5, 10.19 ± 0.51 vs. CIDR12, 13.12 ± 0.52 mm; P = 0.01) and decreased serum concentrations of progesterone (CIDR5, 1.68 ± 0.12 vs. CIDR12, 0.81 ± 0.12 ng/ml; P < 0.01) at CIDR removal. The percentage of cows exhibiting estrus did not differ between treatments (CIDR5, 66.2 vs. CIDR12, 64.5%; P = 0.25). No difference was observed in ovulation rate (CIDR5, 94.1 vs. CIDR12, 94.1%; P = 0.6). Time of estrus expression and ovulation time after CIDR removal did not differ (CIDR5, 59.9 ± 2.3 vs. CIDR12, 61.5 ± 2.3h; P = 0.71 and CIDR5, 88.1 ± 2.6 vs. CIDR12, 90.9 ± 2.6h; P = 0.75; respectively). In conclusion, extended length of CIDR with additional PGF increased follicular diameter and decreased concentrations of progesterone but did not influence estrus response and ovulation time in Brahman cows.

Using over 56,000 pregnancy diagnostic records in beef cattle, a meta-analysis was conducted to objectively determine that 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. Furthermore, by day 30 of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant and pregnancy loss between days 32 and 100 was 5.8%. Reproductive success, however, is highly variable and influenced by maternal and paternal factors. Maternal characteristics, including subspecies, parity and reproductive tract size, intersect with breeding management decisions regarding estrus expression and detection to influence conception and pregnancy rates. The maternal endocrine environment, from estradiol associated with estrus around fertilization to elevated prostaglandins during the embryonic to fetal transition period, play critical roles in pregnancy success. Despite the numerous maternal factors involved with pregnancy establishment, sire contribution to reproductive failure should not be overlooked. Sires are reported to influence pregnancy loss during the second month of gestation in both beef and dairy herds. These differences in sire field fertility could not be explained by differences in semen characteristics nor differences in sire conception rate (SCR) score. To understand parental contribution to pregnancy development during the second month of gestation we developed parthenogenetic (PA) embryos (embryos lacking paternal genome). We observed that PA conceptus had well developed trophectoderm tissue at day 31 of gestation but no site of embryo attachment to the endometrium. Moreover, conceptus secretion such as pregnancy-associated glycoproteins and interferon-stimulated genes were not found in maternal circulation. These results suggest that paternal genetics is required for post-elongated embryo attachment to endometrium. Further exploring the maternal vs paternal contribution to pregnancy development can help elucidate the mechanism that drives reproductive failure in cattle.

The objective of this study was to evaluate the use of corpus luteum (CL) color doppler ultrasonography (CD) for early pregnancy diagnosis in Bos taurus beef cows and evaluate differences in CL blood perfusion among cows that experience late embryonic/early fetal mortality (LEM). Postpartum Bos taurus beef cows (n = 214) from three locations were exposed to a 7-d CO-Synch + CIDR protocol followed by fixed-time artificial insemination (day 0). On days 20 and 22, B-mode and CD ultrasonography were performed to evaluate CL morphometries and blood perfusion, respectively. Cows were considered non-pregnant when CL area was < 20 mm2 or estimated blood perfusion was ≤ 25%. Conventional ultrasonography on day 29 was utilized as the gold standard method. Pregnant cows had greater CL diameter, CL area, and CL volume when compared to non-pregnant cows on day 20 and 22 (P < 0.001; Table 1). Additionally, percentage of central, peripheral, and total luteal blood perfusion, as well as the respective blood perfusion scores were greater (P < 0.001) in pregnant compared with non-pregnant cows on both day 20 and 22. Sensitivity, specificity, positive predicted value (PPV), negative predicted value (NPV), and accuracy for the CD on day 20 were 100, 74, 81, 100, and 88%, respectively. Sensitivity, specificity, PPV, NPV, and accuracy for CD on day 22 were 100, 86, 89, 100, and 93%, respectively. Pairwise comparison of receiver operating characteristics curve analysis indicated no differences between CD on days 20 and 22 (P = 0.12). No differences in luteal blood perfusion were observed on day 20 or 22 among cows that maintained pregnancies compared with LEM cows (P ≥ 0.27). In conclusion, CD successfully detected most non-pregnant cows (81 and 89% on day 20 and 22, respectively) and false negative results were absent (NPV = 100%).

The objective of this study was to evaluate the use of plasma concentrations of pregnancy associated glycoproteins (PAG) for pregnancy diagnosis in beef cows on day 25 of gestation. Additionally, differences in circulating concentrations of PAG among cows that experienced late embryonic/early fetal mortality (LEM) were evaluated. Beef cows (n = 214) were exposed to the 7-d CO-Synch + CIDR protocol followed by fixed-time artificial insemination (day 0). Blood samples were collected on days 25 and 29 to determine circulating concentrations of PAG and ultrasonography on day 29 was used as the gold-standard method for pregnancy diagnosis. On days 25 and 29, PAG concentrations were greater (P < 0.001) in pregnant compared with non-pregnant cows. Sensitivity, specificity, positive predicted value (PPV), negative predicted value (NPV), and accuracy on day 25 were 87, 80, 83, 84, and 83%, respectively. Sensitivity, specificity, PPV, NPV, and accuracy for PAG on day 29 were 99, 94, 96, 97, and 99%, respectively. Pairwise comparison of receiver operating characteristics curve analysis indicated greater area under the curve for PAG on day 29 compared with day 25 (P < 0.001). There were no differences in plasma concentrations of PAG on day 25 among cows that experienced LEM compared to cows that maintained pregnancy (P = 0.46). Concentrations of PAG on day 29 were reduced (P = 0.03) in cows that experienced LEM compared with cows that maintained pregnancy, and were not different between LEM and non-pregnant cows (P = 0.12). In summary, cows that experienced LEM had decreased plasma concentrations of PAG compared with cows that maintained pregnancy. The PAG assay utilized in this study yielded accurate pregnancy diagnosis results on day 29 of gestation: however, the presence of false negative results (NPV = 84%) limits its use on day 25 of gestation.

This experiment examined the effects of diet composition on rumen, vaginal, and uterine environments in beef heifers. Fifteen rumen-cannulated, pubertal Angus-influenced heifers were used in a replicated 3 x 3 Latin square design (28-d periods and 21-d washout intervals). Dietary treatments included (as-fed) diets based on 100% grass hay (HF), 61% grass hay + 39% corn-based concentrate (INT), or 25% grass hay + 75% corn-based concentrate (HG). Treatments were offered individually to heifers once daily at 2% of their body weight. Heifers also received 280 g/d of a mineral mix containing melengestrol acetate. Rumen, vaginal, and uterine fluid samples were collected on d 0 and 28 of each period for pH measurement. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) using results from d 0 as independent covariates, and heifer as the experimental unit. Rumen pH on d 0 did not differ (P = 0.97) among treatments (7.197, 7.194, and 7.188 for HF, INT, and HG, respectively; SEM = 0.038). Ruminal pH on d 28 was greater (P ≤ 0.01) in HF compared with INT and HG (6.805, 6.628, and 6.380, respectively; SEM = 0.049), and greater (P < 0.01) in INT compared with HG. Vaginal and uterine pH on d 0 did not differ (P ≥ 0.24) among HF, INT, and HG (6.914, 6.965, 6.780 of vaginal pH, respectively, SEM = 0.082; 6.644, 6.760, 6,592 of uterine pH, respectively, SEM = 0.079). Uterine and vaginal pH on d 28 also did not differ (P ≥ 0.64) among HF, INT, and HG heifers (6.926, 6.937, 6.918 of vaginal pH, respectively, SEM = 0.051; 6.567, 6.507, and 6.457 of uterine pH, respectively, SEM = 0.084). Therefore, dietary composition impacted rumen pH of beef heifers as expected, but without consequences to their vaginal and uterine pH.

To determine the effects of delaying the injection of prostaglandin F2α (PGF) and fixed-time artificial insemination (TAI) in the 14-d CIDR-PG & TAI protocol, 911 Angus heifers at 5 locations were enrolled in a completely randomized design. Within location heifers were randomly assigned to 1 of 2 treatment groups: 1) PG16 (n = 452), heifers received a CIDR insert on d 0 for 14 d, a 25-mg injection of PGF 16 d after CIDR removal [d 30], and a 100-µg injection of gonadotropin-releasing hormone concurrently with TAI 66 ± 2 h later; or 2) PG17 (n = 459), heifers were treated the same as PG16, however, PGF was administered 17 d after CIDR removal [d 31], and heifers were TAI 66 ± 2 h later. Estrus detection patches were applied to heifers at the time of PGF administration and were examined for activation at TAI. Dominant follicle diameter was determined via transrectal ultrasonography at PGF administration and TAI in a subset of heifers (n = 171). Furthermore, transrectal ultrasonography was performed to determine pregnancy rates to TAI (PR/AI) between 30 and 45 d after TAI. Estrus expression prior to TAI was similar (P = 0.50) between treatments (48.9 vs. 52.0%, respectively). Moreover, dominant follicle diameter at PGF and TAI was similar (P ≥ 0.43) between PG16 and PG17 heifers. Pregnancy rates to TAI did not differ (P = 0.48) between treatment groups (46.4 vs. 48.9%, respectively). The results of this experiment indicate that delaying the injection of PGF from d 30 to d 31 along with TAI in the 14-day CIDR-PG & TAI protocol had no effects on fertility parameters in beef heifers. In conclusion, the PGF injection and TAI in the 14-d CIDR-PG & TAI protocol may be delayed, providing more flexibility in scheduling without negatively affecting fertility.

The objective of this experiment was to compare the expression of Interferon-tau Stimulated Genes (ISGs) in peripheral blood mono and polymorphonuclear cells (PBMCs and PMNs) in heifers following insemination. Twenty-nine Nelore heifers had estrous cycle synchronized, and FTAI occurred on D0. Pregnancy diagnosis was performed by ultrasonography on D28 post FTAI. On D0, 10, 14, 16, 18 and 20, blood (25mL) from the jugular vein was collected in heparinized tubes for isolation of PMNs and PBMCs. The isolation was performed using Ficoll®Paque Plus (GE Healthcare). PMNs and PBMCs samples from 8 pregnant and 9 non-pregnant heifers were subjected to RNA extraction using the DirectZol-RNA kit (Zymo-Research) and Trizol (Invitrogen), respectively. The expression of the target genes (ISG15, OAS-1, MX1 and MX2) was normalized in relation to the two reference genes (GAPDH/ACTB for PMNs and GAPDH/PPIA for PBMCs). The abundance of transcripts was evaluated by analysis of variance considering fixed effects of group, day and group by day interaction using the PROC MIXED procedure in SAS. PMNs and PBMCs had a similar expression profile of ISG15 and OAS-1, showing a relative increase (P < 0.05) from D18, and a significant increase in (P < 0.05) expression in pregnant compared to non-pregnant females on D18 and D20. These results were also observed for MX1 in PBMCs. In PMNs, no significant effects for MX1 were found. For MX2, in both cells types, only a group effect (P < 0.05) was observed, indicating a higher expression in pregnant heifers (0.57±0.11 vs. 0.21±0.03) on the days evaluated. When comparing the relative expression of the target genes to D0, no significant (P > 0.1) differences were found between PMNs and PBMCs. In summary, ISG expression is similar in PMNs and PBMCs, specifically for ISG15 and OAS-1, which both seem to be suitable biomarkers for potential early pregnancy determination in heifers.

In the coming decades, tropical and subtropical regions of the world, including southern United States, southeast Asia, India, parts of Africa and Central and South America, will experience both the greatest increases in population and demands for beef. Potential for expansion of beef production in these areas is considerable due to abundance and low cost of forages that are a non-competitive food source for humans; however, research efforts must emphasize cattle efficiency to maximize sustainability of the cattle industry. Raising tropically adapted cattle in these regions present unique opportunities and challenges that differ from strategies used in production of the predominant B. taurus cattle common in temperate regions of the globe. Despite the physiological differences between B. taurus and B. indicus cattle including reproductive physiology, nutritional requirements, social behavior, digestive system, and body composition, strategies developed in B. taurus cattle are commonly used for B. indicus production. Hence, a fundamental step to meet the increasing global demand for protein while addressing environmental stewardship is to identify these physiological, social and nutrient requirement differences to develop, and disseminate management practices tailored to optimizing production efficiency of B. indicus-influenced cattle reared in subtropical/tropical regions of the planet. From a reproductive management perspective, tropically adapted cattle present several challenges including increased age at puberty, increased postpartum anestrous period and managed in an extensive system. Additionally, reproductive failures post pregnancy establishment are known to be greater in B. indicus cattle in tropical/subtropical regions, although the exact reasons for this outcome have not been identified and addressed. This talk will focus on recent research and strategies aimed at mitigating the impacts of reproductive inefficiency in tropically adapted cattle.