Influence of differing levels of concentrate on circulating cytokine concentrations in beef heifers.

Components of the immune system (e.g., cytokines and chemokines) can influence reproductive efficiency. Characterizing the influence nutrition has on shifts in circulating cytokine concentrations will allow for a better understanding of reproductive efficiency in beef cattle. This study aimed to determine the effect of diet composition on circulating cytokine concentrations of beef heifers. Using a 3 × 3 Latin square design, pubertal Bos taurus-influenced rumen-cannulated heifers (n = 15) were fed a diet based on different concentrate percentages. The treatment period consisted of 28-d feeding periods with a washout interval of 21 d. Treatment groups were fed 100% grass hay (high forage; HF), 60% grass hay with 40% corn-based concentrate (intermediate; INT), and 25% grass hay with 75% corn-based concentrate (high grain; HG). Heifers were offered 2% of their body weight in feed daily. Blood was collected on days 0 and 28 of the treatment period for cytokine analysis. Plasma cytokine concentrations were quantified using RayBiotech Quantibody Bovine Cytokine Array Q1 kit according to manufacturer instructions. Concentrations of interferon gamma-induced protein 10 (IP10) linearly decreased with an increased concentrate diet (P = 0.037). Concentrations of IP10 differed for heifers consuming HF diet vs. HG diet (3,069.52 vs. 1,001.84 ±â€…669.01 pg/mL, respectively) and heifers consuming INT diet vs. HG diet (2,886.77 vs. 1,001.84 ±â€…669.01 pg/mL, respectively); however, there were no significant differences in IP10 concentrations between HF and INT heifers. There was a tendency for interleukin-1 family member 5 (IL1F5) concentrations to be lower for heifers consuming the HG diet compared to INT diet (P = 0.08). Results suggest that heifers consuming a high-concentrate diet have lower concentrations of IP10 and IL1F5. Additional research is necessary to better understand the dietary influence on the immune system in developing heifers.

Maternal versus environmental contributions to the piglet pioneer microbiome.

The pioneer microbiome is the initial colonization and establishment of microorganisms within the neonate. The objective of this project was to quantify maternal and environmental contributions to the piglet's pioneer microbiome. Sterile swabs were used to collect samples from the gilt's rectum, the farrowing crate before and after gilts were moved in, the gilt's birth canal during farrowing, and the piglet's rectum on days 0 (prior to suckling), 3, and 10 post-farrowing and at weaning (21.6 ± 1.0 days post-farrowing). During farrowing, colostrum was collected from each gilt from a representative sample of teats into a single sterile collection cup. Bacterial DNA extraction and sequencing targeted the V4 hypervariable region of the 16S rRNA gene. The relative abundance of Lactobacillus in the piglet microbiome was lower on day 3 compared to day 0, 10, and at weaning (P < 0.05). For alpha diversity, piglet samples exhibited distinct clustering for bacterial richness by day (P < 0.01). Multiple regression analyses indicated that the birth canal explained 51.6% of the variation observed in the piglet day 0 microbiome (P < 0.0001) and 6.5% of the variation in the piglet day 10 microbiome (P = 0.013). The day 10 microbiome explained 58.6% of the variation observed in the piglet microbiome at weaning (P < 0.0001). Bacterial communities of the farrowing crate and colostrum did not impact the piglet microbiome for any day (P > 0.10). Results indicate that the piglet pioneer microbiome is largely influenced by the microbiome of the birth canal.

Characterization of boar semen microbiome and association with sperm quality parameters.

Elevated levels of bacteria within fresh extended boar semen are associated with decreased sperm longevity, therefore reducing the fertility of a semen dose. The objective of this study was to characterize the bacterial communities using 16S rRNA sequencing in freshly extended boar semen samples and relate the prevalence and diversity of the microbial population to sperm quality parameters 1) between studs, 2) between pooled and single-sire doses, and 3) over a 5-day period. Eight single-sire (n = 4 per stud) and eight pooled (n = 4 per stud) non-frozen extended semen doses were obtained from two boar studs (A and B). Pooled doses were the composite of the boar's ejaculates used in single-sire doses. Doses were subsampled for 5 d post-collection. Ten negative controls of each pooled dose (n = 2) and single-sire dose (n = 8) remained sealed until the last day. Microbiome analysis was achieved by examining the V4 hypervariable region of the 16S rRNA gene of flash-frozen samples. Two evaluators determined the average sperm motility and agglutination (0: no adhesion to 3: >50% adhesion) by averaging their estimates together at 10 random locations per slide. Stud A had greater sperm agglutination (1.6 vs. 1.0 ± 0.1; P < 0.01) than stud B. Sperm motility decreased over the 5-day period (P < 0.01) and tended (P = 0.09) to be greater in stud B than A (67.4% vs. 61.5% ± 0.02%). Compared with stud A, stud B had a greater relative abundance of Proteobacteria (60.0% vs. 47.2% ± 1.5%; P < 0.01) and a lower relative abundance of Firmicutes (22.5% vs. 31.9% ± 1.4%; P < 0.01). Moreover, stud A had a greater relative abundance of Bacteroidetes (6.3% vs. 5.3% ± 0.4%; P < 0.01) and Actinobacteria (11.5% vs. 10.1% ± 0.5%; P = 0.05) than stud B. Differences were found in alpha diversity for both Chao1 (P < 0.01) and Shannon (P < 0.01) diversity indexes among days 2, 3, 4, and 5 post-collection to day 1. For beta diversity, unweighted UniFrac metric on days 2, 3, 4, and 5 post-collection differed from those on day 1 (P < 0.01). There were significant correlations between sperm motility and relative abundance of Prevotella (r = -0.29), Ruminococcus (r = -0.24), and Bacteroides (r = -0.32). Additionally, there were significant correlations between sperm motility and Chao1 (r = -0.50) and Shannon's index (r = -0.36). These results demonstrate that differences in bacterial communities over time and between boar studs can be associated with variation in sperm quality.

The ability to improve production output remains essential to meet the growing global demand for pork. However, the presence of pathogenic bacteria such as Escherichia coli and Clostridium perfringens can hinder production goals by reducing semen quality through increased clumping events and decreased sperm motility. In addition, reduced conception rates and decreased litter size can occur when bacterial-contaminated semen doses are used for artificial insemination. The purpose of this study was to determine the bacterial communities within freshly extended boar semen and associate specific bacterial communities with sperm quality measurements. Current findings suggest that certain bacteria can accumulate within a group of animals or over a short period of time which can impact sperm cell characteristics. Having less diverse bacterial communities also appears to be associated with favorable semen quality. Future research is needed to determine the interactions different bacterial communities have with sperm cells to characterize their nature as pathogenic or commensal.

Reproductive microbiome and cytokine profiles associated with fertility outcomes of postpartum beef cows.

Shifts from commensal bacteria (for example, Lactobacillus in the phylum Firmicutes) within the reproductive tract have been associated with changes in local reproductive immune responses and decreased fertility in humans. The objective of this study was to characterize the microbiome and cytokine concentrations before artificial insemination (AI) in vaginal and uterine flushes from postpartum beef cows. Twenty Bos indicus-influenced beef cows (approximately 60 d postpartum and free of reproductive, health, or physical issues) were enrolled. The B. indicus prostaglandin (PG) 5-d + controlled intervaginal drug-releasing estrus synchronization protocol was initiated on day -8 of the study with timed AI on d0. Blood samples were collected on days -3, -1, and 28 via coccygeal venipuncture. Vaginal and uterine flushes were collected on days -3 and -1. Based on days 28 pregnancy status determined by transrectal ultrasonography, cows were identified as either Open (n = 13) or Pregnant (n = 7). Bacterial community analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. Cytokine analyses were performed using the RayBiotech Quantibody Bovine Cytokine Array Q1 and MyBioSource ELISA kits per the manufacturer's instructions. Statistical analyses for bacteria relative abundance were conducted using PROC NPAR1WAY and for cytokine concentrations using PROC GLM in SAS 9.4. Uterine concentrations of interferon γ, interleukin (IL)1α, and IL21 were greater in Open than in Pregnant cows (P < 0.05). Regardless of pregnancy status, uterine IL13 increased from days -3 to -1 (9.76 vs. 39.48 ± 9.28 pg/mL, respectively; P < 0.05). Uterine relative abundance of the phylum Firmicutes decreased from days -3 to -1 in Open cows (60.4% ± 0.9% vs. 48.5% ± 3.2%; P = 0.004). In Open cows, the genus Blautia decreased in relative abundance within the uterus from days -3 to -1 (2.1% ± 0.2% vs. 0.9% ± 0.1%; P = 0.002). Uterine relative abundance of the phylum Tenericutes increased from days -3 to -1 in Pregnant cows (1.0% ± 0.1% vs. 7.6% ± 4.1%; P = 0.002). In Pregnant cows, the genus Ureaplasma tended to increase within the uterus from days -3 to -1 (0.08% ± 0.06% vs. 7.3% ± 4.1%; P = 0.054). These findings suggest a distinct difference in the reproductive microbiome and cytokine profiles before AI for resulting Open vs. Pregnant cows.

Efficiently producing cattle to feed a growing population can come with many challenges. A few challenges occur soon after a cow has given birth, and subsequent reproductive performance can be impacted. Bacteria within the reproductive tract can trigger an immune response and together play a role in affecting fertility in cows. The objectives of this experiment were to distinguish the commensal vs. harmful bacteria that reside in the reproductive tract and to characterize the immune response in beef cattle via uterine and vaginal flushes. The results demonstrated that bacteria within the reproductive tract of beef cattle changes before breeding. The current study also suggests that changes in immune response before breeding can be associated with fertility outcomes. Additional research may be worthwhile to evaluate management tactics to positively shift bacteria within the reproductive tract and reduce inflammatory immune responses to improve fertility and increase reproductive efficiency. Future research is necessary to identify the causes of bacterial shifts and how it relates to pregnancy establishment.

Reproductive Microbiomes in Domestic Livestock: Insights Utilizing 16S rRNA Gene Amplicon Community Sequencing.

Advancements in 16S rRNA gene amplicon community sequencing have vastly expanded our understanding of the reproductive microbiome and its role in fertility. In humans, Lactobacillus is the overwhelmingly dominant bacteria within reproductive tissues and is known to be commensal and an indicator of fertility in women and men. It is also known that Lactobacillus is not as largely abundant in the reproductive tissues of domestic livestock species. Thus, the objective of this review is to summarize the research to date on both female and male reproductive microbiomes in domestic livestock species (i.e., dairy cattle, beef cattle, swine, small ruminants, and horses). Having a comprehensive understanding of reproductive microbiota and its role in modulating physiological functions will aid in the development of management and therapeutic strategies to improve reproductive efficiency.

Shifts in bacterial communities in the rumen, vagina, and uterus of beef heifers receiving different levels of concentrate.

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 (P < 0.01) 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 (P < 0.01) 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 (P < 0.01) 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. Cow­calf 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 cow­calf 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.

Evaluation of Resistance to Fescue Toxicosis in Purebred Angus Cattle Utilizing Animal Performance and Cytokine Response.

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue; however, varying symptomatic responses potentially imply genetic tolerance to the syndrome. It was hypothesized that a subpopulation of animals within a herd would develop tolerance to ergot alkaloid toxicity. Therefore, the goals of this study were to develop selection criteria to identify tolerant and susceptible animals within a herd based on animal performance, and then examine responsive phenotypic and cytokine profiles to fescue toxicosis. Angus cows grazed endophyte-infected tall fescue at two locations for 13 weeks starting in mid-April 2016. Forage measurements were collected to evaluate ergot alkaloid exposure during the study. A post hoc analysis of animal performance was utilized to designate cattle into either tolerant or susceptible groups, and weekly physiological measurements and blood samples were collected to evaluate responses to chronic exposure to endophyte-infected tall fescue. Findings from this study support the proposed fescue toxicosis selection method formulated herein, could accurately distinguish between tolerant and susceptible animals based on the performance parameters in cattle chronically exposed to ergot alkaloids, and provides evidence to warrant additional analysis to examine the impact of ergot alkaloids on immune responsiveness in cattle experiencing fescue toxicosis.

Effects of endophyte-infected tall fescue seed and protein supplementation on stocker steers: I. Growth performance and hemodynamic responses.

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue and is detrimental to growth and performance. Recent research has shown that supplementing protein has the potential to enhance growth performance in weaned steers. Therefore, the objective of this study was to evaluate the effect of supplemental CP on physiological parameters in stocker steers experiencing fescue toxicosis. Thirty-six weaned Angus steers (6 mo of age) stratified by weight (196.1 ± 3.6 kg) were assigned to a 2 × 2 factorial arrangement for 56 d: endophyte-free (EF) seed and 14% CP (EF-14; n = 9), EF seed and 18% CP (EF-18; n = 9), endophyte-infected (EI) seed and 14% CP (EI-14; n = 9), and EI seed and 18% CP (EI-18; n = 9). Steer growth and hemodynamic responses were collected weekly during ergot alkaloid exposure. On day 14 of the trial, iButton temperature data loggers were subcutaneously inserted in the lateral neck region to record hourly body temperature for 42 d. Data were analyzed using PROC MIXED of SAS with repeated measures. No differences were observed in DMI, BW, ADG, F:G, or BCS during the treatment period (P > 0.05). Hair shedding scores, rectal temperatures, surface temperatures, and respiration rates were greater in EI steers compared to EF steers regardless of supplemental CP (P < 0.05). However, subcutaneous body temperature was greater in EI-14 steers (37.94 °C) compared to other steer groups (37.60, 37.68, 37.72 ± 0.04 °C for EF-14, EF-18, and EI-18, respectively; P < 0.05). Prolactin concentrations tended to be greater in EF steers when compared to EI steers (P = 0.07). Heart rate and hematocrit were reduced for EI-18 steers compared to other steer groups (P < 0.05). Caudal artery diameter was reduced in EI-18 steers compared to EI-14 steers (2.60 vs. 2.75 ± 0.05 mm, respectively; P < 0.05) and caudal vein diameter was reduced in EI-18 steers (3.20 mm) compared to all other steer groups (3.36, 3.39, 3.50 mm for EF-14, EF-18, and EI-14, respectively; P < 0.05). However, there was no difference observed in systolic or diastolic blood pressure during the treatment period (P > 0.05). Based on the data, exposure to low to moderate levels of ergot alkaloids during the stocker phase had a negative impact on hemodynamic responses and supplemental CP had minimal impact to alleviate symptoms. Therefore, feeding additional protein above established requirements is not expected to help alleviate fescue toxicosis.

Effects of endophyte-infected tall fescue seed and protein supplementation on stocker steers: II. Adaptive and innate immune function.

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue that affects performance; however, little information is available pertaining to its effects on immunity. Recently, it has been shown that supplemental CP can improve performance in weaned steers postvaccination. Thus, the objective of this study was to evaluate the effect of supplemental CP on innate and adaptive immune responses in stocker steers chronically exposed to ergovaline. Angus steers (n = 12 pens; 3 steers/pen) were stratified by weight and assigned to a 2 × 2 factorial arrangement to examine crude protein levels of supplement (14% or 18%) and ergovaline exposure (0 or 185 µg ergovaline/kg BW/d via ground endophyte-free (EF) or endophyte-infected (EI) tall fescue seed, respectively) on immune response. Consumption of low to moderate concentration of ergovaline from EI tall fescue seed was sufficient to induce mild symptoms associated with fescue toxicosis. Blood samples were collected at day 0, 42, and 56 to evaluate infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea virus (BVDV) type 1b titers following vaccine challenge. Additionally, serum cytokine concentrations were evaluated using Quantibody Bovine Cytokine Arrays on day 0, 28, and 42. Data were analyzed using PROC MIXED of SAS with repeated measures. Regardless of treatment, no differences were observed in IBR and BVDV-1b seroconversion following vaccine challenge (P > 0.05). Regardless of crude protein concentration, EI steers had greater concentrations of proinflammatory cytokines (TNF-α, IFN-γ, IL-1α), chemokines (CCL2, CCL4, MIG), anti-inflammatory cytokines (IL-2, -13, -15, -21), and various growth factors (FGF-1, IGF-1, VEGF-A) when compared to EF steers (P < 0.05). Furthermore, VEGF-A and IGF-1 concentrations were greater in EI-14 steers on day 28 compared to EI-18, EF-14, and EF-18 steers (P < 0.05), however, this difference was not observed on day 0 or 42 (P > 0.05). Based on these data, steers exposed to ergovaline have an increase in pro- and anti-inflammatory cytokines and supplemental CP had minimal impact to mitigate this response. However, in the current study, exposure to ergovaline had little to no effect on adaptive immunity and response to vaccination. Together, chronic exposure to ergovaline results in a hyperactive innate immune response, which may lead to an immuno-compromised animal.

Impact of Ergot Alkaloids on Female Reproduction in Domestic Livestock Species.

Fescue toxicosis is a multifaceted syndrome that elicits many negative effects on livestock consuming ergot alkaloids produced by endophyte-infected tall fescue. The economic losses associated with fescue toxicosis are primarily due to reproductive failure including altered cyclicity, suppressed hormone secretion, reduced pregnancy rates, agalactia, and reduced offspring birth weights. For decades, a multitude of research has investigated the physiological and cellular mechanisms of these reproductive failures associated with fescue toxicosis. This review will summarize the various effects of ergot alkaloids on female reproduction in grazing livestock species.

Impact of slick hair trait on physiological and reproductive performance in beef heifers consuming ergot alkaloids from endophyte-infected tall fescue1.

Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue. The objective of this study was to evaluate the impact of the slick hair trait on physiological and reproductive parameters in heifers experiencing fescue toxicosis. Angus × Senepol heifers (n = 31) were blocked by weight (393.5 ± 17.3 kg) and phenotype relative to hair coat at birth, and randomly fed novel endophyte fescue (EN) or endophyte-infected fescue (EI) haylage in a total mixed ration for 91 d. Weekly measurements were collected to monitor heifer growth and response during ergot alkaloids exposure. Following 28 d of treatment, estrus was synchronized and heifers were inseminated. Ovary mapping and AI pregnancy rate were examined via transrectal ultrasonography. Blood samples were taken for genotyping: slick (S) or wildtype (W). Data were analyzed using repeated measures in PROC MIXED of SAS including fescue treatment (EN vs. EI), genotype (S vs. W), and sample collection time as main effects. Body condition scores were decreased for W heifers compared with S heifers (5.48 vs. 5.66, respectively; P < 0.0001). Surface temperature was greater for EI-W heifers (37.2 °C) compared with other groups (36.4, 36.6, 36.7 °C for EN-S, EN-W, EI-S, respectively; P < 0.05). Serum PRL concentrations were reduced for EI heifers compared with EN heifers (133.5 vs. 163.1 ng/mL, respectively; P < 0.05). The average number of 2 to 4 mm follicles were greater in EI-W heifers (13.8 follicles) compared with other groups (12.2, 10.6, and 11.1 for EN-S, EN-W, and EI-S, respectively; P < 0.0001). However, the average number of preovulatory follicles (≥9 mm) were reduced in EI-W heifers (0.52 follicles) compared with other heifer groups (0.94, 0.88, and 0.85 ± 0.04 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Ovulatory follicle size was smaller in EI-W heifers compared with EN-W heifers (9.14 vs. 11.57 mm, respectively; P = 0.05). Corpus luteum area was reduced in EI-W heifers (235.1 mm2) compared with other heifer groups (297.2, 272.7, and 276.8 mm2 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Concentrations of P4 were greater for EN heifers compared with EI heifers (2.7 vs. 1.8 ng/mL, respectively; P < 0.05). Pregnancy was not established in EI-W heifers (0%) compared with other heifer groups (37.5%, 57.1%, and 62.5% for EN-S, EN-W, and EI-S, respectively; P < 0.05). Overall, the slick hair mutation appears to aid in offsetting the physiological symptoms associated with fescue toxicosis and helps to improve reproductive performance.

A two-injection prostaglandin F2α presynchronization treatment decreases pregnancy rates of cycling replacement beef heifers.

Improving artificial insemination (AI) pregnancy rates in replacement heifers improves the genetic advancement within a herd. Heifers that have completed at least three estrous cycles prior to breeding have greater pregnancy rates compared to acyclic females. Therefore, it was hypothesized that a presynchronization treatment program consisting of two injections of prostaglandin F2α (PGF2α) prior to the start of the CO-Synch + 5 d CIDR protocol would initiate earlier attainment of puberty and more estrous cycles prior to AI, thus increasing AI pregnancy rates. All heifers were managed the same at two locations over the course of 2 yr. Heifers were randomly assigned to receive either the two-injection PGF2α presynchronization treatment (PreSynch; n = 105) or no presynchronization (Control; n = 106) prior to the start of estrous synchronization. On the first day of the trial, reproductive tract scores (RTSs), pelvic areas, body condition scores, and weights were collected on all heifers. All heifers were synchronized with the CO-Synch + 5 d CIDR protocol and fixed-time artificially inseminated with semen from a bull of known fertility. Blood samples were collected three consecutive times at 7 d intervals starting 45 d prior to estrous synchronization to determine the onset of puberty via analyzing progesterone concentrations. Pregnancy status to AI was assessed using ultrasonography diagnosis at approximately 30 and 60 d post insemination. Data were analyzed using PROC MIXED of SAS and reported as least square mean. The PreSynch treatment decreased AI pregnancy rates (52.2% vs. 38.1 ± 6.3% for Control vs. PreSynch, respectively; P = 0.06) and did not result in earlier attainment of puberty in beef heifers (P > 0.05). The PreSynch treatment did not impact pregnancy rates in heifers with an RTS of 3 or 4 (P > 0.05). However, PreSynch heifers with an RTS of 5 had decreased pregnancy rates (68.3% vs. 46.9 ± 10.1% for Control vs. PreSynch, respectively; P < 0.05). Finally, PreSynch heifers with increased body condition of 6 had decreased pregnancy rates when compared to Control heifers (37.5% vs. 62.5 ± 11.6%, respectively; P < 0.05). On the basis of these data, implementation of heifer breeding soundness examination at least 3 wk prior to the start of the breeding season may be beneficial for selecting replacement females; however, presynchronization with prostaglandins immediately prior to estrous synchronization will negatively affect AI pregnancy rates in cycling pubertal heifers.

Ergot alkaloids induce vasoconstriction of bovine uterine and ovarian blood vessels.

Fescue toxicosis is a syndrome that impairs growth and reproduction in cattle grazing endophyte-infected tall fescue [Lolium arundinaceum [(Schreb.].) Darbysh)] in the United States, resulting in approximately $1 billion in annual economic loss in species that utilize this forage resource. Approximately 90% of tall fescue contains an endophytic fungus (Epichloë coenophiala) that produces ergot alkaloids. Ergot alkaloids cause vasoconstriction and reduced blood flow to the extremities; however, it remains unknown how blood flow to the reproductive organs is affected in cattle. Therefore, the objective of this study was to determine if ergot alkaloids from endophyte-infected tall fescue reduce blood flow to the reproductive organs, thus hindering reproductive function. Angus heifers (n = 36) naïve to ergot alkaloids were placed in Calan gates and randomly assigned to receive either endophyte-infected fescue seed (E+) or noninfected fescue seed (E-; control) in a total mixed ration for 63 d. Weekly measurements were taken to monitor heifer growth and response to ergot alkaloid exposure. Reproductive measurements, including ovarian structures, uterine and ovarian vessel diameter, and hormone concentrations were determined after heifers were synchronized using the standard CO-Synch + 7 d CIDR protocol to ensure all measurements were collected at the same stages of the estrous cycle (0, 4, 10, and 17 d). Data were analyzed using repeated measures in PROC MIXED of SAS. Average daily gain was decreased for the E+ group (0.8 kg/d) compared to control heifers (1.0 kg/d). Body condition scores tended to be greater in control heifers compared to the E+ group (P = 0.053). Additionally, hair coat and hair shedding scores were greater in E+ heifers compared to controls (P < 0.05). Heart rate, rectal temperature, respiration rate, and blood pressure did not differ between treatments (P > 0.05). Vasoconstriction was observed in the caudal artery, but not the caudal vein, in heifers consuming the E+ fescue seed (P < 0.05). No differences were observed in antral follicle counts, corpus luteum area or circulating progesterone concentrations in E+ heifers compared to controls (P > 0.05). There was a significant decrease in the diameter of arteries and veins servicing the ovary and uterus on day 10 and 17 of the estrous cycle. Reduction in blood flow to the reproductive organs during critical times in the estrous cycle may contribute to the reduced ovarian function and pregnancy rates associated with fescue toxicosis.

Maternal obesity alters the expression of embryonic regulatory transcripts in the preimplantation ovine conceptus.

The influence of exposure to overfeeding-induced maternal obesity around the time of conception on early embryogenesis was examined in the day 14 ovine conceptus. The relative abundance of FGFR2 and DNMT1 was influenced by maternal obesity status and conceptus sex, and the abundance of PPARG and PTGS2 transcripts was greater in male conceptuses regardless of the obesity status of the ewe. These observations demonstrated that short-term exposure to maternal obesity impacts early conceptus transcript patterning.