Hepatic transcript profiling in beef cattle: Effects of feeding endophyte-infected tall fescue seeds

The objective of our study was to evaluate the effect of endophyte-infected tall fescue (E+) seeds intake on liver tissue transcriptome in growing Angus × Simmental steers and heifers through RNA-seq analysis. Normal weaned calves (~8 months old) received either endophyte-free tall fescue (E-; n = 3) or infected tall fescue (E+; n = 6) seeds for a 30-d period. The diet offered was ad libitum bermudagrass (Cynodon dactylon) hay combined with a nutritional supplement of 1.61 kg (DM basis) of E+ or E- tall fescue seeds, and 1.61 kg (DM basis) of energy/protein supplement pellets for a 30-d period. Dietary E+ tall fescue seeds were included in a rate of 20 μg of ergovaline/kg BW/day. Liver tissue was individually obtained through biopsy at d 30. After preparation and processing of the liver samples for RNA sequencing, we detected that several metabolic pathways were activated (i.e., upregulated) by the consumption of E+ tall fescue. Among them, oxidative phosphorylation, ribosome biogenesis, protein processing in endoplasmic reticulum and apoptosis, suggesting an active mechanism to cope against impairment in normal liver function. Interestingly, hepatic protein synthesis might increase due to E+ consumption. In addition, there was upregulation of "thermogenesis" KEGG pathway, showing a possible increase in energy expenditure in liver tissue due to consumption of E+ diet. Therefore, results from our study expand the current knowledge related to liver metabolism of growing beef cattle under tall fescue toxicosis.

Risks for animal health related to the presence of ergot alkaloids in feed

The European Commission requested EFSA to provide an update of the 2012 Scientific Opinion of the Panel on Contaminants in the Food Chain (CONTAM) on the risks for animal health related to the presence of ergot alkaloids (EAs) in feed. EAs are produced by several fungi of the Claviceps and Epichloë genera. This Opinion focussed on the 14 EAs produced by C. purpurea (ergocristine, ergotamine, ergocornine, α- and β-ergocryptine, ergometrine, ergosine and their corresponding 'inine' epimers). Effects observed with EAs from C. africana (mainly dihydroergosine) and Epichloë (ergovaline/-inine) were also evaluated. There is limited information on toxicokinetics in food and non-food producing animals. However, transfer from feed to food of animal origin is negligible. The major effects of EAs are related to vasoconstriction and are exaggerated during extreme temperatures. In addition, EAs cause a decrease in prolactin, resulting in a reduced milk production. Based on the sum of the EAs, the Panel considered the following as Reference Points (RPs) in complete feed for adverse animal health effects: for pigs and piglets 0.6 mg/kg, for chickens for fattening and hens 2.1 and 3.7 mg/kg, respectively, for ducks 0.2 mg/kg, bovines 0.1 mg/kg and sheep 0.3 mg/kg. A total of 19,023 analytical results on EAs (only from C. purpurea) in feed materials and compound feeds were available for the exposure assessment (1580 samples). Dietary exposure was assessed using two feeding scenarios (model diets and compound feeds). Risk characterisation was done for the animals for which an RP could be identified. The CONTAM Panel considers that, based on exposure from model diets, the presence of EAs in feed raises a health concern in piglets, pigs for fattening, sows and bovines, while for chickens for fattening, laying hens, ducks, ovines and caprines, the health concern related to EAs in feed is low.

Cardioprotective properties of quercetin in fescue toxicosis-induced cardiotoxicity via heart-gut axis in lambs (Ovis Aries)

The present study investigated whether quercetin mitigated fescue toxicosis-induced cardiovascular injury via the heart-gut axis. Twenty-four commercial Dorper lambs were stratified by body weight and assigned randomly to diets in one of four groups: endophyte-free without quercetin (E-,Q-), endophyte-positive without quercetin (E+,Q-), endophyte-positive plus 4 g/kg quercetin (E+,Q+) or endophyte-free plus 4 g/kg quercetin (E-,Q+) for 42 days. Body weight and average daily feed intake (ADFI) of lambs fed the endophyte-positive diets showed significant decreases. However, in the groups treated with quercetin, there were significant alterations of cardiac enzymes. Furthermore, reduced fescue toxicosis-induced histopathological lesions of heart and aorta were demonstrated in the E+,Q+ lambs. Results also suggested quercetin eased cardiovascular oxidative injury by inhibiting the increase of oxidative metabolites, and enhancing the levels of antioxidases. Quercetin reduced the inflammation response through suppressing NF-κB signaling pathway activation. Additionally, quercetin ameliorated fescue toxicosis-induced mitochondria dysfunction and improved mitochondrial quality control through enhancing PGC-1α-mediated mitochondrial biogenesis, maintaining the mitochondrial dynamics, and relieving aberrant Parkin/PINK-mediated mitophagy. Quercetin enhanced gastrointestinal microbial alpha and beta diversity, alleviated gut microbiota and microbiome derived metabolites-SCFAs dysbiosis by fescue toxicosis. These findings signified that quercetin may play a cardio-protective role via regulating the heart-gut microbiome axis.

Pituitary and liver selenoprotein transcriptome profiles of grazing steers and their sensitivity to the form of selenium in vitamin-mineral mixes

Many supplemental Se-dependent metabolic effects are mediated through the function of selenoproteins. The full complement and relative abundance of selenoproteins expressed by highly metabolic cattle tissues have not been characterized in cattle. The complement and number of selenoprotein mRNA transcripts expressed by the pituitary and liver of healthy growing beef steers (n = 7 to 8) was characterized using NanoString methodology (Study 1). Of the 25 known bovine selenoproteins, 24 (all but SELENOH) were expressed by the pituitary and 23 (all but SELENOH and SELENOV) by the liver. Transcript abundance ranged (P ≤ 0.05) over 5 orders of magnitude in the pituitary (> 10,000 for GPX3, < 10 for DIO1 and GPX2) and liver (> 35,000 for SELENOP, < 10 for DIO2). Also unknown is the sensitivity of the selenoprotein transcriptome to the form of supplemental Se. The effect of form of supplemental Se on the relative content of selenoprotein mRNA species in the pituitary and liver of steers grazing a Se-deficient (0.07 ppm Se) tall fescue pasture and consuming 85 g/d of a basal vitamin-mineral mix that contained 35 ppm Se as either ISe (n = 6), organically-bound Se (SELPLEX; OSe, n = 7 to 8), or a 1:1 blend of ISe and OSe (MIX, n = 7 to 8) was determined by RT-PCR after sequence-validating the 25 bovine selenoprotein cDNA products (Study 2). In the pituitary, Se form affected (P < 0.05) the relative content of 9 selenoprotein mRNAs and 2 selenoprotein P receptor mRNAs in a manner consistent with a greater capacity to manage against oxidative damage, maintain cellular redox balance, and have a better control of protein-folding in the pituitaries of OSe and MIX versus ISe steers. In the liver, expression of 5 selenoprotein mRNA was affected (P ≤ 0.05) in a manner consistent with MIX steers having greater redox signaling capacity and capacity to manage oxidative damage than ISe steers. We conclude that inclusion of 3 mg Se/d as OSe or MIX versus ISe, forms of supplemental Se in vitamin-mineral mixes alters the selenoprotein transcriptome in a beneficial manner in both the pituitary and liver of growing steers consuming toxic endophyte-infected tall fescue.

Grass-fed vs. grain-fed beef systems: performance, economic, and environmental trade-offs

Between increasing public concerns over climate change and heightened interest of niche market beef on social media, the demand for grass-fed beef has increased considerably. However, the demand increase for grass-fed beef has raised many producers' and consumers' concerns regarding product quality, economic viability, and environmental impacts that have thus far gone unanswered. Therefore, using a holistic approach, we investigated the performance, carcass quality, financial outcomes, and environmental impacts of four grass-fed and grain-fed beef systems currently being performed by ranchers in California. The treatments included 1) steers stocked on pasture and feedyard finished for 128 d (CON); 2) steers grass-fed for 20 mo (GF20); 3) steers grass-fed for 20 mo with a 45-d grain finish (GR45); and 4) steers grass-fed for 25 mo (GF25). The data were analyzed using a mixed model procedure in R with differences between treatments determined by Tukey HSD. Using carcass and performance data from these systems, a weaning-to-harvest life cycle assessment was developed in the Scalable, Process-based, Agronomically Responsive Cropping Systems model framework, to determine global warming potential (GWP), consumable water use, energy, smog, and land occupation footprints. Final body weight varied significantly between treatments (P < 0.001) with the CON cattle finishing at 632 kg, followed by GF25 at 570 kg, GR45 at 551 kg, and GF20 478 kg. Dressing percentage differed significantly between all treatments (P < 0.001). The DP was 61.8% for CON followed by GR45 at 57.5%, GF25 at 53.4%, and GF20 had the lowest DP of 50.3%. Marbling scores were significantly greater for CON compared to all other treatments (P < 0.001) with CON marbling score averaging 421 (low-choice ≥ 400). Breakeven costs with harvesting and marketing for the CON, GF20, GR45, and GF25 were $6.01, $8.98, $8.02, and $8.33 per kg hot carcass weight (HCW), respectively. The GWP for the CON, GF20, GR45, and GF25 were 4.79, 6.74, 6.65, and 8.31 CO2e/kg HCW, respectively. Water consumptive use for CON, GF20, GR45, and GF25 were 933, 465, 678, and 1,250 L/kg HCW, respectively. Energy use for CON, GF20, GR45, and GF25 were 18.7, 7.65, 13.8, and 8.85 MJ/kg HCW, respectively. Our results indicated that grass-fed beef systems differ in both animal performance and carcass quality resulting in environmental and economic sustainability trade-offs with no system having absolute superiority.

Response of Beef Cattle Fecal Microbiota to Grazing on Toxic Tall Fescue

Tall fescue, the predominant southeastern United States cool-season forage grass, frequently becomes infected with an ergot alkaloid-producing toxic endophyte, Epichloë coenophialum Consumption of endophyte-infected fescue results in fescue toxicosis (FT), a condition that lowers beef cow productivity. Limited data on the influence of ergot alkaloids on rumen fermentation profiles or ruminal bacteria that could degrade the ergot alkaloids are available, but how FT influences the grazing bovine fecal microbiota or what role fecal microbiota might play in FT etiology and associated production losses has yet to be investigated. Here, we used 16S rRNA gene sequencing of fecal samples from weaned Angus steers grazing toxic endophyte-infected (E+; n = 6) or nontoxic (Max-Q; n = 6) tall fescue before and 1, 2, 14, and 28 days after pasture assignment. Bacteria in the Firmicutes and Bacteroidetes phyla comprised 90% of the Max-Q and E+ steer fecal microbiota throughout the trial. Early decreases in the Erysipelotrichaceae family and delayed increases of the Ruminococcaceae and Lachnospiraceae families were among the major effects of E+ grazing. E+ also increased abundances within the Planctomycetes, Chloroflexi, and Proteobacteria phyla and the Clostridiaceae family. Multiple operational taxonomic units classified as Ruminococcaceae and Lachnospiraceae were correlated negatively with weight gains (lower in E+) and positively with respiration rates (increased by E+). These data provide insights into how E+ grazing alters the Angus steer microbiota and the relationship of fecal microbiota dynamics with FT.IMPORTANCE Consumption of E+ tall fescue has an estimated annual $1 billion negative impact on the U.S. beef industry, with one driver of these costs being lowered weight gains. As global agricultural demand continues to grow, mitigating production losses resulting from grazing the predominant southeastern United States forage grass is of great value. Our investigation of the effects of E+ grazing on the fecal microbiota furthers our understanding of bovine fescue toxicosis in a real-world grazing production setting and provides a starting point for identifying easy-to-access fecal bacteria that could serve as potential biomarkers of animal productivity and/or FT severity for tall fescue-grazing livestock.

Forms of selenium in vitamin-mineral mixes differentially affect serum alkaline phosphatase activity, and serum albumin and blood urea nitrogen concentrations, of steers grazing endophyte-infected tall fescue

The goal of this study was to test the hypothesis that sodium selenite (ISe), SEL-PLEX (OSe), vs. a 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral mix would differentially affect serological and hepatic parameters of growing steers grazing toxic endophyte-infected tall fescue-mixed forage pasture. Predominately Angus steers (BW = 183 ± 34 kg) were randomly selected from herds of fall-calving cows grazing endophyte-infected tall fescue-mixed pasture and consuming vitamin-mineral mixes that contained 35 ppm Se as ISe, OSe, and MIX forms. Steers were weaned, depleted of Se for 98 d, and subjected to summer-long common grazing of an endophyte-infected tall fescue-mixed pasture (0.51 ppm total ergovaline + ergovalinine; 10.1 ha). Steers were assigned (n = 8 per treatment) to the same Se form treatments upon which they were raised. Se treatments were administered by daily top-dressing 85 g of vitamin-mineral mix onto 0.23 kg soyhulls, using in-pasture Calan gates. The PROC MIXED procedure of SAS was used to assess the effect of Se form treatments on serum parameters at day 0, 22, 43, 64, and 86. After slaughter, the effect of Se treatment on hepatic alkaline phosphatase (tissue nonspecific isoform, TNALP) mRNA, protein, and albumin protein content was assessed using the PROC GLM procedure of SAS. Fisher's protected LSD procedure was used to separate treatment means. Partial correlation analysis was used to evaluate the relationship among whole blood Se concentration and serum parameters, accounting for the effect of time. Across periods, MIX steers had more (P ≤ 0.04) serum albumin than OSe and ISe steers, respectively. However, the relative hepatic bovine serum albumin protein content was not affected (P = 0.28) by Se treatments. Serum alkaline phosphatase activity was greater (P ≤ 0.01) in MIX and OSe steers. Similarly, hepatic TNALP protein content in MIX steers was greater (P = 0.01) than ISe steers. Partial correlation analysis revealed that serum albumin, blood urea nitrogen, and alkaline phosphatase activity were correlated (r ≥ 0.23, P ≤ 0.02) with whole blood Se concentration. In summary, consumption of 3 mg Se/d as OSe or MIX forms of Se in vitamin-mineral mixes increased serum albumin concentration and alkaline phosphatase activity, the reduction of which is associated with fescue toxicosis. We conclude that the organic forms of Se ameliorated the depression of 2 of known serological biomarkers of fescue toxicosis.

Forms of selenium in vitamin-mineral mixes differentially affect the expression of genes responsible for prolactin, ACTH, and α-MSH synthesis and mitochondrial dysfunction in pituitaries of steers grazing endophyte-infected tall fescue

The goal of this study was to test the hypothesis that sodium selenite (inorganic Se, ISe), SEL-PLEX (organic forms of Se, OSe), vs. a 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral (VM) mix would differentially alter pituitary transcriptome profiles in growing beef steers grazing an endophyte-infected tall fescue (E+) pasture. Predominately Angus steers (BW = 183 ± 34 kg) were randomly selected from fall-calving cows grazing E+ pasture and consuming VM mixes that contained 35 ppm Se as ISe, OSe, or MIX forms. Steers were weaned, depleted of Se for 98 d, and subjected to summer-long common grazing of a 10.1 ha E+ pasture containing 0.51 ppm ergot alkaloids. Steers were assigned (n = 8 per treatment) to the same Se-form treatments on which they were raised. Selenium treatments were administered by daily top-dressing 85 g of VM mix onto 0.23 kg soyhulls, using in-pasture Calan gates. As previously reported, serum prolactin was greater for MIX (52%) and OSe (59%) steers vs. ISe. Pituitaries were collected at slaughter and changes in global and selected mRNA expression patterns determined by microarray and real-time reverse transcription PCR analyses, respectively. The effects of Se treatment on relative gene expression were subjected to one-way ANOVA. The form of Se affected the expression of 542 annotated genes (P < 0.005). Integrated pathway analysis found a canonical pathway network between prolactin and pro-opiomelanocortin (POMC)/ACTH/α-melanocyte-stimulating hormone (α-MSH) synthesis-related proteins and that mitochondrial dysfunction was a top-affected canonical pathway. Targeted reverse transcription-PCR analysis found that the relative abundance of mRNA encoding prolactin and POMC/ACTH/α-MSH synthesis-related proteins was affected (P < 0.05) by the form of Se, as were (P ≤ 0.05) mitochondrial dysfunction-related proteins (CYB5A, FURIN, GPX4, and PSENEN). OSe steers appeared to have a greater prolactin synthesis capacity (more PRL mRNA) vs. ISe steers through decreased dopamine type two receptor signaling (more DRD2 mRNA), whereas MIX steers had a greater prolactin synthesis capacity (more PRL mRNA) and release potential by increasing thyrotropin-releasing hormone concentrations (less TRH receptor mRNA) than ISe steers. OSe steers also had a greater ACTH and α-MSH synthesis potential (more POMC, PCSK2, CPE, and PAM mRNA) than ISe steers. We conclude that form of Se in VM mixes altered expression of genes responsible for prolactin and POMC/ACTH/α-MSH synthesis, and mitochondrial function, in pituitaries of growing beef steers subjected to summer-long grazing an E+ pasture.

Glutathione content and expression of proteins involved with glutathione metabolism differs in longissimus dorsi, subcutaneous adipose, and liver tissues of finished vs. growing beef steers

Increased tissue redox state may result in sub-optimal growth. Our goal was to determine if glutathione (GSH) content and expression of proteins involved with GSH metabolism change in longissimus dorsi (LD), subcutaneous adipose (SA), and liver tissues of growing vs. finishing steer phenotypes. Tissues were taken from 16 Angus steers (BW = 209 ± 29.4 kg) randomly assigned (n = 8) to develop through Growing (final BW = 301 ± 7.06 kg) vs. Finished (final BW = 576 ± 36.9 kg) growth phases, and at slaughter had achieved different rib-eye area (REA) (53.2, 76.8 cm2), marbling scores (296, 668), and 12th rib adipose thickness (0.54, 1.73 cm), respectively (Amino Acids, doi:10.1007/s00726-018-2540-8). GSH content (mg/g wet tissue) was determined by a commercial assay and the relative content of target protein and mRNA in tissue homogenates was determined by Western blot and reverse-transcribed PCR analyses, respectively. The effect of growth phase (Finished vs. Growing) was assessed by ANOVA using the GLM procedure of SAS. The LD of Finished steers had more (P < 0.04) GSH (42%) and GSH synthesizing (GCLC, 61%; GCLM, 21%) and metabolizing (GPX1, 42%; GPX3, 73%; GGT1, 56%) enzymes, and less (P < 0.02) GPX2 (46%), EAAC1 (30%) and glutamine synthetase (GS) (28%), whereas GTRAP3-18 and ARL6IP1 did not differ (P > 0.57). Principal component analysis found that GSH content of LD was associated with REA and marbling score. The SA of Finished steers had less (P < 0.04) GSH (38%), GSH metabolizing (GPX4, 52%; GGT1, 71%) enzyme mRNA, and GTRAP3-18 (123%) and ARL6IP1 (43%), whereas the mRNA content of GSH-synthesizing enzymes and content of EAAC1 and GS did not differ (P > 0.32). The liver of Finished steers had less (P < 0.02) mRNA content of GSH synthesizing (GCLC, 39%; GSS 29%) and metabolizing (GPX1, 30%) enzymes, and more (P < 0.01) GSTM1 metabolizing enzyme (114%). The change in GSH content as steers fattened indicate an increased antioxidant capacity in the LD of Finished steers, and a decreased antioxidant capacity in SA, consistent with changes in enzyme and transporter expression. Changes in liver enzyme and transporter expression were consistent with no change in GSH content. The relationship of EAAC1 regulatory proteins (GTRAP3-18, ARL6IP1) to GSH, EAAC1, and GS content differs and changes as Growing steers develop into Finished phenotypes. These findings provide mechanistic insight into how antioxidant capacity occurs in tissues of economic and metabolic importance as cattle fatten.

Hepatic glutamate transport and glutamine synthesis capacities are decreased in finished vs. growing beef steers, concomitant with increased GTRAP3-18 content

Hepatic glutamate uptake and conversion to glutamine is critical for whole-body N metabolism, but how this process is regulated during growth is poorly described. The hepatic glutamate uptake activities, protein content of system [Formula: see text] transporters (EAAC1, GLT-1) and regulatory proteins (GTRAP3-18, ARL6IP1), glutamine synthetase (GS) activity and content, and glutathione (GSH) content, were compared in liver tissue of weaned Angus steers randomly assigned (n = 8) to predominantly lean (growing) or predominantly lipid (finished) growth regimens. Steers were fed a cotton seed hull-based diet to achieve final body weights of 301 or 576 kg, respectively, at a constant rate of growth. Liver tissue was collected at slaughter and hepatic membranes fractionated. Total (75%), Na+-dependent (90%), system [Formula: see text]-dependent (abolished) glutamate uptake activity, and EAAC1 content (36%) in canalicular membrane-enriched vesicles decreased as steers developed from growing (n = 6) to finished (n = 4) stages, whereas Na+-independent uptake did not change. In basolateral membrane-enriched vesicles, total (60%), Na+-dependent (60%), and Na+-independent (56%) activities decreased, whereas neither system [Formula: see text]-dependent uptake nor protein content changed. EAAC1 protein content in liver homogenates (n = 8) decreased in finished vs. growing steers, whereas GTRAP3-18 and ARL6IP1 content increased and GLT-1 content did not change. Concomitantly, hepatic GS activity decreased (32%) as steers fattened, whereas GS and GSH contents did not differ. We conclude that hepatic glutamate uptake and GS synthesis capacities are reduced in livers of finished versus growing beef steers, and that hepatic system [Formula: see text] transporter activity/EAAC1 content is inversely proportional to GTRAP3-18 content.

Forms of selenium in vitamin-mineral mixes differentially affect serum prolactin concentration and hepatic glutamine synthetase activity of steers grazing endophyte-infected tall fescue

The goal of this study was to test the hypothesis that sodium selenite (ISe), SEL-PLEX (OSe), vs. an 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral (VM) mix would differentially affect metabolic parameters and performance of growing steers grazing toxic endophyte-infected tall fescue mixed forage (E+) pasture. Predominately-Angus steers (BW = 183 ± 34 kg) were randomly selected from herds of fall-calving cows grazing E+ pasture and consuming VM mixes that contained 35 ppm Se as ISe, OSe, and MIX forms. Steers were weaned, depleted of Se for 98 d, and subjected to summer-long common grazing of an E+ pasture (0.51 ppm total ergovaline per ergovalinine; 10.1 ha). Steers were assigned (n = 8 per treatment) to the same Se-form treatments upon which they were raised. Selenium treatments were administered by daily top-dressing 85 g of VM mix onto 0.23 kg soyhulls, using in-pasture Calan gates. The PROC MIXED procedure of SAS was used to assess effect of Se-form treatments on whole blood Se (ng/mL) and serum prolactin (ng/mL) at day 0, 22, 43, 64, and 86, and caudal arterial area (mm2) at day -7, 43, and 86. The effect of Se treatment on ADG (day 86), and liver glutamine synthetase (GS) mRNA, protein, and activity (nmol/mg wet tissue/min) were assessed using the PROC GLM procedure of SAS. Fisher's protected LSD procedure was used to separate treatment means. Whole blood Se increased (P < 0.01) for all treatments from day 0 to 22 and then did not change (P ≥ 0.17), and was greater (P ≤ 0.04) for MIX and OSe steers. Serum prolactin decreased (P < 0.01) over time and was greater (P < 0.05) for MIX and OSe steers. Liver GS mRNA content was 66% and 59% greater (P < 0.05) in MIX and OSe steers, respectively, than ISe steers. Liver GS protein content in MIX steers was 94% more (P < 0.01) than ISe steers. Moreover, MIX and OSe steers had 99% and 55% more (P ≤ 0.01) liver GS activity, respectively, than ISe steers. ADG was not affected (P = 0.36) by Se treatments. We conclude that consumption of 3 mg Se/d as OSe or MIX forms of Se in VM mixes increased 1) whole blood Se content, an indicator of greater whole-body Se assimilation; 2) serum prolactin, the reduction of which is a hallmark of fescue toxicosis; and 3) hepatic GS activity, indicating greater hepatic assimilation of acinar ammonia. However, 4) these positive effects on metabolic parameters were not accompanied by increased growth performance.

Pituitary genomic expression profiles of steers are altered by grazing of high vs. low endophyte-infected tall fescue forages

Consumption of ergot alkaloid-containing tall fescue grass impairs several metabolic, vascular, growth, and reproductive processes in cattle, collectively producing a clinical condition known as "fescue toxicosis." Despite the apparent association between pituitary function and these physiological parameters, including depressed serum prolactin; no reports describe the effect of fescue toxicosis on pituitary genomic expression profiles. To identify candidate regulatory mechanisms, we compared the global and selected targeted mRNA expression patterns of pituitaries collected from beef steers that had been randomly assigned to undergo summer-long grazing (89 to 105 d) of a high-toxic endophyte-infected tall fescue pasture (HE; 0.746 μg/g ergot alkaloids; 5.7 ha; n = 10; BW = 267 ± 14.5 kg) or a low-toxic endophyte tall fescue-mixed pasture (LE; 0.023 μg/g ergot alkaloids; 5.7 ha; n = 9; BW = 266 ± 10.9 kg). As previously reported, in the HE steers, serum prolactin and body weights decreased and a potential for hepatic gluconeogenesis from amino acid-derived carbons increased. In this manuscript, we report that the pituitaries of HE steers had 542 differentially expressed genes (P < 0.001, false discovery rate ≤ 4.8%), and the pattern of altered gene expression was dependent (P < 0.001) on treatment. Integrated Pathway Analysis revealed that canonical pathways central to prolactin production, secretion, or signaling were affected, in addition to those related to corticotropin-releasing hormone signaling, melanocyte development, and pigmentation signaling. Targeted RT-PCR analysis corroborated these findings, including decreased (P < 0.05) expression of DRD2, PRL, POU1F1, GAL, and VIP and that of POMC and PCSK1, respectively. Canonical pathway analysis identified HE-dependent alteration in signaling of additional pituitary-derived hormones, including growth hormone and GnRH. We conclude that consumption of endophyte-infected tall fescue alters the pituitary transcriptome profiles of steers in a manner consistent with their negatively affected physiological parameters.

Vasoactivity and Vasoconstriction Changes in Cattle Related to Time off Toxic Endophyte-Infected Tall Fescue

Previous research has indicated that serotonergic and α-adrenergic receptors in peripheral vasculature are affected by exposure of cattle grazing toxic endophyte-infected (E+; Epichlöe coenophialia) tall fescue (Lolium arundinaceum). The objective of this experiment was to determine the period of time necessary for the vascular effects of ergot alkaloids to subside. Two experiments were conducted to investigate changes in vascular contractile response and vasoconstriction over time relative to removal from an ergot alkaloid-containing E+ tall fescue pasture. In Experiment 1, lateral saphenous vein biopsies were conducted on 21 predominantly Angus steers (357 ± 3 kg body weight) at 0 (n = 6), 7 (n = 6), 14 (n = 5), or 28 days (n = 4) after removal from grazing pasture (3.0 ha; endpoint ergovaline + ergovalinine = 1.35 mg/kg DM) for 126 days. In Experiment 2, lateral saphenous veins were biopsied from 24 Angus-cross steers (361 ± 4 kg body weight) at 0, 21, 42, and 63 days (n = 6 per time point) following removal from grazing tall fescue pastures (3.0 ha; first 88 days endpoint ergovaline + ergovalinine = 0.15 mg/kg DM; last 18 days endpoint ergovaline + ergovalinine = 0.57 mg/kg DM) for 106 total days. Six steers (370 ± 18 kg body weight) off of bermudagrass pasture for the same time interval were also biopsied on Day 0 and Day 63 (n = 3 per time point). Additionally, in Experiment 2, cross-sectional ultrasound scans of caudal artery at the fourth coccygeal vertebra were taken on Days 0, 8, 15, 21, 29, 36, 42, and 45 to determine mean artery luminal area to evaluate vasoconstriction. In both experiments, steers were removed from pasture and housed in a dry lot and fed a corn silage diet for the duration of biopsies and ultrasound scans. Biopsied vessels used to evaluate vasoactivity were cleaned, incubated in a multimyograph, and exposed to increasing concentrations of 4-Bromo-3,6-dimethoxybenzocyclobuten-1-yl) methylamine hydrobromide (TCB2; 5HT_2A agonist), guanfacine (GF; α_2A-adrenergic agonist), and (R)-(+)-m-nitrobiphenyline oxalate (NBP; α_2C-adrenergic agonist) in both experiments and ergovaline (ERV) and ergotamine (ERT) in Experiments 1 and 2, respectively. In Experiment 1, days off pasture × agonist concentration was not significant (p > 0.1) for all four compounds tested. In Experiment 2, GF, NBP, TCB2 and ERT were significant for days off pasture × agonist concentration interaction (p < 0.02) and vasoactivity increased over time. Vasoactivity to agonists was reduced (p < 0.05) when steers were initially removed from E+ tall fescue pasture compared to bermudagrass, but did not differ by Day 63 for any variable. Luminal areas of caudal arteries in steers grazed on E+ tall fescue relaxed and were similar to steers that had grazed bermudagrass for 36 days on non-toxic diet (p = 0.15). These data demonstrate changes in peripheral vasoactivity and recovery from vasoconstriction occur beyond five weeks off toxic pasture and 5HT_2A receptors appear to be more dramatically affected in the lateral saphenous vein by grazing E+ tall fescue pasture than adrenergic receptors.

The physiological consequences of ingesting a toxic plant (Diplotaxis tenuifolia) influence subsequent foraging decisions by sheep (Ovis aries)

Toxins and nutrients interact and define herbivores' experiences with toxic plants. However, there are still open questions about the mechanisms by which nutrient-toxin interactions affect experience and as a consequence foraging decisions by consumers. This study provides a deeper insight into such mechanisms by using supplemental nutrients, a toxic plant typically avoided by herbivores (wild rocket; Diplotaxis tenuifolia), and a small ruminant (sheep; Ovis aries) as models. Thirty-six sheep were randomly assigned to four treatments (n=9) where animals consumed: wild rocket ("DT"), wild rocket followed by a protein supplement ("DT+P"), wild rocket followed by a protein supplement+a mineral supplement containing iodine and copper ("DT+P+M"), or alfalfa pellets in amounts that paired the ingestion of wild rocket by DT ("CTRL"). Towards the end of the phase of exposure (day 35), DT showed the lowest intake of wild rocket, as well as reduced levels of plasma thyroid hormones (T3 and T4), alanine aminotransferase, and a trend towards reduced hemoglobin relative to DT+P and DT+P+M. Total concentration of serum proteins and albumins were greater in sheep fed the protein supplements, which have probably elicited a protective effect on toxin ingestion. Foraging behavior was then evaluated in an experimental arena where animals could select among randomly distributed buckets containing a fixed amount of wild rocket or variable amounts of barley grain (a preferred food). Regardless of barley grain availability, DT showed lower intake and lower times spent eating wild rocket than DT+P and DT+P+M. Unexpectedly, CTRL (without previous experience with wild rocket) ingested amounts of wild rocket comparable to those observed by DT+P and DT+P+M. A negative feeding experience with wild rocket is needed for animals to display the typical pattern of aversion commonly observed in grazing conditions.

Gene expression profiling indicates an increased capacity for proline, serine, and ATP synthesis and mitochondrial mass by the liver of steers grazing high vs. low endophyte-infected tall fescue

Grazing -infected forages results in a variety of reduced animal performance parameters, collectively known as "fescue toxicosis." The initial, limited evaluations of hepatic mechanisms affected by fescue toxicosis have used transcriptomic expression profiling of experimental phenotypes developed by short-term feeding of concentrated ergot alkaloids or fescue seeds to rodents and steers. To assess the effects of fescue toxicosis in growing cattle using a commercially relevant phenotype, we induced fescue toxicosis in beef steers by summer-long grazing (89 to 105 d) of a single high toxic endophyte-infected tall fescue pasture (HE; 0.746 μg/g ergot alkaloids; 5.7 ha; = 10; BW = 267 ± 14.5 kg) vs. a low toxic endophyte tall fescue-mixed pasture (LE; 0.023 μg/g ergot alkaloids; 5.7 ha; = 9; BW = 266 ± 10.9 kg). High toxic endophyte tall fescue-mixed pasture steers had decreased BW (313 vs. 338 kg) and an increased potential for hepatic gluconeogenesis from AA-derived carbons. To gain a greater perspective into fescue toxicosis-induced hepatic metabolism and identify candidate regulatory mechanisms, the goal of the current research was to examine liver samples for changes in gene (mRNA) expression profiles using a Bovine Affymetrix microarray and selected reverse-transcription PCR and immunoblot analyses. The expression (false discovery rate < 10%; < 0.01) of 147 genes was increased (7 to 268%) and that of 227 was decreased (4 to 87%) in livers of HE vs. LE steers. The top (1) functional gene category was cell-mediated immune response (33 genes; ≤ 0.012), (2) canonical cell signaling pathway was primary immunodeficiency signaling (8 genes; ≤ 0.0003), and (3) canonical metabolic pathways were oxidative phosphorylation (5 genes; ≤ 0.016) and purine metabolism (8 genes; ≤ 0.029). High toxic endophyte tall fescue-mixed pasture steers had increased ( ≤ 0.022) expression of genes critical for increased (1) Pro () and Ser () synthesis, (2) shunting of AA carbons into pyruvate () and ATP synthesis (, , , COX4, , and ), and (3) mitochondrial mass (COX4). Targeted reverse-transcribed PCR or immunoblot assays corroborated ( ≤ 0.035) these latter microarray findings for , , , , and COX4. Moreover, network analysis identified glucocorticoid receptor-mediated signaling as the most probable mechanism to coordinate the above findings. These results greatly extend our knowledge of the consequences of summer-long grazing of endophyte-infected tall fescue to the hepatic metabolism of growing steers.

Glutamine synthetase and alanine transaminase expression are decreased in livers of aged vs. young beef cows and GS can be upregulated by 17β-estradiol implants

Aged beef cows (≥ 8 yr of age) produce calves with lower birth and weaning weights. In mammals, aging is associated with reduced hepatic expression of glutamine synthetase (GS) and alanine transaminase (ALT), thus impaired hepatic Gln-Glu cycle function. To determine if the relative protein content of GS, ALT, aspartate transaminase (AST), glutamate transporters (EAAC1, GLT-1), and their regulating protein (GTRAP3-18) differed in biopsied liver tissue of (a) aged vs. young (3 to 4 yr old) nonlactating, nongestating Angus cows (Exp. 1 and 2) and (b) aged mixed-breed cows with and without COMPUDOSE (17β-estradiol) ear implants (Exp. 3), Western blot analyses were performed. In Exp. 1, 12 young (3.62 ± 0.01 yr) and 13 aged (10.08 ± 0.42 yr) cows grazed the same mixed forage for 42 d (August-October). In Exp. 2, 12 young (3.36 ± 0.01 yr) and 12 aged (10.38 ± 0.47 yr) cows were individually fed (1.03% of BW) a corn-silage-based diet to maintain BW for 20 d. For both Exp. 1 and 2, the effect of cow age was assessed by ANOVA using the MIXED procedure of SAS. Cow BW did not change ( ≥ 0.17). Hepatic ALT (78% and 61%) and GS (52% and 71%) protein content (Exp. 1 and 2, respectively) was decreased ( ≤ 0.01), whereas GTRAP3-18 (an inhibitor of EAAC1 activity) increased ( ≤ 0.01; 170% and 136%) and AST, GLT-1, and EAAC1 contents did not differ ( ≥ 0.17) in aged vs. young cows. In Exp. 2, free concentrations (nmol/g) of Glu, Ala, Gln, Arg, and Orn in liver homogenates were determined. Aged cows tended to have less ( = 0.10) free Gln (15.0%) than young cows, whereas other AA concentrations did not differ ( 0.26). In Exp. 3, 14 aged (> 10 yr) cows were randomly allotted ( = 7) to sham or COMPUDOSE (25.7 mg of 17β-estradiol) implant treatment (TRT), and had ad libitum access to alfalfa hay for 28 d. Blood and liver biopsies were collected 14 and 28 d after implant treatment. Treatment, time after implant (DAY), and TRT × DAY effects were assessed by ANOVA using the MIXED procedure of SAS. Cow BW was not affected ( ≥ 0.96). Implant increased ( ≤ 0.02) total plasma estradiol by 220% (5.07 vs. 1.58 pg/mL) and GS protein by 300%, whereas the relative content of other proteins was not altered ( ≥ 0.16). We conclude that hepatic expression of ALT and GS are reduced in aged vs. young cows, and administration of 17β-estradiol to aged cows increases plasma estradiol and hepatic GS, but not that of other proteins that support hepatic Glu metabolism.

Summer-Long Grazing of High vs. Low Endophyte (Neotyphodium coenophialum)-Infected Tall Fescue by Growing Beef Steers Results in Distinct Temporal Blood Analyte Response Patterns, with Poor Correlation to Serum Prolactin Levels

Previously, we reported the effects of fescue toxicosis on developing Angus-cross steer growth, carcass, hepatic mRNA, and protein expression profiles of selected serum proteins, and blood clinical and chemical profiles, after summer-long grazing (85 days) of high endophyte (HE)- vs. low endophyte (LE)-infected fescue pastures. We now report the temporal development of acute, intermediate, and chronic responses of biochemical and clinical blood analytes determined at specified time intervals (period 1, day 0–36; period 2, day 37–58; and period 3, day 59–85). Throughout the trial, the alkaloid concentrations of the HE forage was consistently 19–25 times greater (P ≤ 0.002) than the concentration in the LE forage, and HE vs. LE steers had continuously lower (P ≤ 0.049) serum prolactin (85%), cholesterol (27%), and albumin (5%), but greater red blood cells (7%). The HE steers had decreased (P = 0.003) ADG only during period 1 (−0.05 vs. 0.4 kg/day). For period 1, HE steers had reduced (P ≤ 0.090) numbers of eosinophils (55%) and lymphocytes (18%), serum triglyceride (27%), and an albumin/globulin ratio (9%), but an increased bilirubin concentration (20%). During period 2, serum LDH activities were 18% lower (P = 0.022) for HE vs. LE steers. During period 3, serum levels of ALP (32%), ALT (16%), AST (15%), creatine kinase (35%), glucose (10%), and LDH (23%) were lower (P ≤ 0.040) for HE steers. Correlation analysis of serum prolactin and other blood analytes revealed that triglycerides (P = 0.042) and creatinine (P = 0.021) were moderately correlated (r ≤ 0.433) with HE serum prolactin. In conclusion, three HE-induced blood analyte response patterns were identified: continually altered, initially altered, and subsequently “recovered,” or altered only after long-term exposure. Blood analytes affected by length of grazing HE vs. LE forages were either not or poorly correlated with serum prolactin. These data reveal important, temporal, data about how young cattle respond to the challenge of consuming HE pasture.

Endophyte infection of tall fescue and the impact of climatic factors on ergovaline concentrations in field crops cultivated in southern France

Tall fescue (Lolium arundinaceum) infected by Epichloe coenophiala contains ergot alkaloids responsible for fescue toxicosis in Australia, New Zealand, and the United States, with only a few cases occurring in Europe. The detection of Epichloe in 166 L. arundinaceum collected in southern France revealed that 60% were infected, 51% being high ergovaline producers. The ergovaline level in endophyte-infected tall fescue Kentucky 31 was monitored during 3 years in various parts of the plant. Maturation of plants, recorded according to the BBCH scale, appeared to be the main factor for estimating the risk of toxicity. Ergovaline levels of ≥300 μg/kg dry matter were obtained at the end of spring, the beginning of autumn, and mid-winter. Positive correlation between ergovaline level and cumulative degree-d was observed, whereas rainfall had no effect. These results suggest that the lack of fescue toxicosis observed in France cannot be explained by the lack of ergovaline in tall fescue.

Ergovaline in tall fescue and its effect on health, milk quality, biochemical parameters, oxidative status, and drug metabolizing enzymes of lactating ewes

Ergovaline (EV) produced by symbiotic association of Epichloë coenophiala with tall fescue (Lolium arundinaceum) causes toxicoses in livestock. In this study, 16 lactating ewes (BW 76.0 ± 0.6 kg) were used to determine the effects of feeding endophyte-infected (FE+) or endophyte free (FE-) tall fescue hay on animal health and performances and to investigate the putative mechanisms of action of EV. The mean EV concentrations in FE+ and FE- diets were 497 ± 52 and <5 µg/kg DM, respectively. Decreased hay consumption and BW were observed in the FE+ group. Prolactin (PRL) concentrations decreased (P < 0.02) in the FE+ group from d 3 to 28 of the study compared to the FE- group, but no consequences were observed on milk quantity or quality. Skin temperature and the thermocirculation index were lower (P < 0.05) in the FE+ than in the FE- group from d 3 to 7, but this effect disappeared from d 14 to 28. Hematocrit, mineral and biochemical, and enzymatic analyses of plasma revealed no differences between the 2 groups. Measurement of oxidative damage and antioxidant enzyme activities revealed a decrease in the activities of plasma catalase (P < 0.05), kidney glutathione reductase and peroxidase and in kidney total glutathione and malondialdehyde contents (P < 0.02) in ewes fed FE+. Hepatic flavin monooxygenase enzyme activities decreased (P < 0.01) in ewes fed FE+, except for a marked increase in the demethylation of erythromycin. This activity is linked to cytochrome P4503A content and is known to be involved in ergot alkaloid metabolism. Glutathione S-transferase activity in the kidneys decreased (P < 0.02) in the FE+ group, whereas no difference was observed in uridine diphosphate-glucuronosyltransferase activity in the liver or kidneys. The reversibility of the effect of FE+ hay on skin temperature and the increase in erythromycin N-demethylase activity may contribute to the relative resistance of ewes to EV toxicity.

Alteration of fasting heat production during fescue toxicosis in Holstein steers

This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW = 348 ± 13 kg) were BW-matched into pairs and used in a 2 period crossover design experiment. Each period consisted of 2 temperature segments, one each at 22 and 30°C. During each period, 1 steer per pair was ruminally dosed twice daily with 0.5 kg of ground endophyte-infected fescue seed (E+) and the other with ground endophyte-free fescue seed (E-) for 7 d. Steers on E- treatment were pair-fed to E+ steers offered alfalfa cubes at 1.5 × NEm. On d 8 of each segment, steers were moved to individual metabolism stalls fitted with indirect calorimetry head boxes. Ruminal contents were removed, weighed, and subsampled for DM determinations. The reticulorumen was washed and filled with a buffer (NaCl = 96; NaHCO3 = 24; KHCO3 = 30; K2HPO4 = 2; CaCl2 = 1.5; MgCl2 = 1.5 mmol·kg buffer(-1)) that was gassed with a 75% N2 and 25% CO2 mixture before rumen incubation. During buffer incubation, an E+ or E- fescue seed extract was added at 12 h intervals to maintain treatment presentation to the animal. After a 12-h wait, heart rate, O2 consumption, CO2 production, and urinary output were recorded for 16 h. There was no difference (P = 0.931) in DMI/kg(0.75) between endophyte treatments by design; however, intake decreased (P = 0.004) at 30°C. Increased temperature had no effect (P > 0.10) on other measurements and there were no significant interactions (P > 0.11) of temperature and endophyte treatment. Heart rate was unaffected by fescue treatment or environmental temperature. Percent DM of ruminal contents as well as total rumen DM/kg(0.75) was increased (P < 0.0001) in E+ steers. Respiratory quotient was elevated (P = 0.02) in E+ steers. Oxygen consumption decreased (P = 0.04) and CO2 production tended to be reduced (P = 0.07) during E+ treatment. Calculated FHP (kcal/kg BW(0.75)) was also less (P = 0.006) in steers receiving E+ treatment. These data suggest that consumption of endophyte-infected tall fescue by cattle results in a reduction in basal metabolic rate.

Effects of supplementing endophyte-infected tall fescue with sainfoin and polyethylene glycol on the physiology and ingestive behavior of sheep

Tannins in sainfoin (Onobrychis viciifolia) may bind to alkaloids in endophyte-infected tall fescue [E+; Lolium arundinaceum (Schreb.) Darbysh.] and attenuate toxicosis. If so, supplementing E+ with sainfoin will increase use of E+ by sheep, and polyethylene glycol (PEG)-a polymer that selectively binds to tannins-will reduce such response. To test these predictions, thirty-six 2-mo-old lambs were randomly assigned to 3 treatments (12 lambs/treatment). During exposure, all lambs were individually penned and fed E+ supplemented with beet pulp (CTRL), fresh-cut sainfoin and beet pulp (SAIN), or fresh-cut sainfoin plus PEG mixed in beet pulp (SAIN+PEG). Feed intake was measured daily. Rectal temperatures and jugular blood samples were taken at the beginning and end of exposure. After exposure, all lambs were offered choices between endophyte-free tall fescue (E-) and orchardgrass, and preference for E- was assessed. Then, all lambs were allowed to graze a choice of E+ and sainfoin or a monoculture of E+. The foraging behavior of lambs was recorded. When sainfoin was in mid-vegetative stage, lambs in SAIN ingested more E+ than lambs in CTRL (P = 0.05), but no differences were detected between lambs in SAIN+PEG and CTRL (P = 0.12). Sainfoin supplementation improved some physiological parameters indicative of fescue toxicosis. Lambs in SAIN had lower rectal temperatures (P = 0.02), greater numbers of leukocytes (P < 0.001) and lymphocytes (P = 0.03), and greater plasmatic concentrations of globulin (P = 0.009) and prolactin (P = 0.019) than lambs in CTRL. Some of these differences were offset by the SAIN+PEG treatment. When lambs were offered choices between E- and orchardgrass, only lambs in SAIN had greater intake of E- than lambs in CTRL (P < 0.001). When lambs were allowed to graze a choice of E+ and sainfoin, all treatments used E+ to the same extent (P > 0.05). On the other hand, when they grazed on a monoculture of E+, lambs in SAIN+PEG showed greater acceptance of E+ than lambs in SAIN or in CTRL (P < 0.05). In summary, sainfoin supplementation alleviated several of the classic signs of fescue toxicosis and increased intake of endophyte-infected tall fescue. Tannins in sainfoin partially accounted for this benefit since feeding a polymer that selectively binds to tannins (PEG) attenuated some these responses. However, sainfoin supplementation during initial exposure to E+ did not lead to an increased preference for E+ during grazing.

NutriPhysioGenomics applications to identify adaptations of cattle to consumption of ergot alkaloids and inorganic versus organic forms of selenium: altered nutritional, physiological and health states?

NutriPhysioGenomics (NPG) seeks to measure nutrition-responsive genome expression during specific physiological states, thus defining how a given challenge alters the ‘basal’ transcriptome. Application of NGS regimens (transcriptome and bioinformatics analyses) in combination with targeted-gene approaches has revealed cellular mechanisms putatively responsible for complex, whole-animal, metabolic syndromes such as heat stress and subacute ruminal acidosis. Using similar approaches, our laboratory sought to understand how the basal physiology of developing cattle adapted to two prevalent health challenges of forage-based beef cattle production in south-eastern USA: fescue toxicosis and selenium (Se) deficiency. In Model 1, pituitary and hepatic genomic expression profiles of growing beef steers grazing high (E+, n = 9) versus low (E–, n = 10) endophyte-infected tall fescue pastures for 85 days, and consuming sodium selenite (ISe) as a free-choice Se supplement, were compared by a combination of microarray, bioinformatic, and targeted-gene/protein (real-time reverse transcription–PCR, Nanostring, immunoblot) analyses. In Model 2, hepatic genomic expression profiles of growing beef heifers (0.5 kg gain/day) fed a cotton seed hull-based diet and different sources (n = 9) of dietary Se (3 mg/day) supplements (no supplement, Control; inorganic Se, sodium selenite, ISe; organic Se, Sel-Plex; OSe), or a 1.5 mg : 1.5 mg blend of ISe and OSe, MIX) were compared after 168 days of supplementation, as described for Model 1. The results for Model 1 showed, that in the pituitary of E+ steers, expression of genes for prolactin signalling; redox capacity; regulation of lactotroph, gonadotroph, and thyrotroph proliferation; gonadotropin-releasing hormone-mediated signalling; and Se-based metabolism was impaired. Concomitantly, the livers of E+ steers had an increased level of expression of genes encoding proteins responsible for shunting of amino acid carbons into pyruvate and ATP synthesis capacity (oxidative phosphorylation pathway, mitochondrial mass), increased serine and proline biosynthesis, and reduced selenoprotein-mediated metabolism. Result for Model 2 showed that, overall, there were clear differences in the profiles of differentially expressed genes (DEG) among the four Se treatment groups, with the form of Se administered being more reflective of DEG profiles than the total amount of Se assimilated. Moreover, hepatic transcriptomes profiles of MIX heifers revealed an increased potential for selenoprotein synthesis and selenoprotein-mediated metabolism. In addition, several genes involved with increased redox capacity were upregulated in MIX versus ISe heifers. Taken together, our NGS approach characterised adaptation to physiological challenges and, serendipitously, identified suppression of several metabolic pathways by consumption of ergot alkaloid consumption that have the potential to be increased with supplementation of the MIX form of Se.

Alterations in serotonin receptor-induced contractility of bovine lateral saphenous vein in cattle grazing endophyte-infected tall fescue

As part of a 2-yr study documenting the physiologic impact of grazing endophyte-infected tall fescue on growing cattle, 2 experiments were conducted to characterize and evaluate effects of grazing 2 levels of toxic endophyte-infected tall fescue pastures on vascular contractility and serotonin receptors. Experiment 1 examined vasoconstrictive activities of 5-hydroxytryptamine (5HT), α-methylserotonin (ME5HT; a 5HT(2) receptor agonist), d-lysergic acid (LSA), and ergovaline (ERV) on lateral saphenous veins collected from steers immediately removed from a high-endophyte-infected tall fescue pasture (HE) or a low-endophyte-infected mixed-grass (LE) pasture. Using the same pastures, Exp. 2 evaluated effects of grazing 2 levels of toxic endophyte-infected tall fescue on vasoconstrictive activities of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), BW 723C86 (BW7), CGS-12066A (CGS), and 5-carboxamidotryptamine hemiethanolate maleate (5CT), agonists for 5HT(2A),( 2B), 5HT(1B), and 5HT(7) receptors, respectively. One-half of the steers in Exp. 2 were slaughtered immediately after removal from pasture, and the other one-half were fed finishing diets for >91 d before slaughter. For Exp. 1, maximal contractile intensities were greater (P < 0.05) for steers grazing LE pastures than HE pastures for 5HT (73.3 vs. 48.9 ± 2.1%), ME5HT (52.7 vs. 24.9 ± 1.5%), and ERV (65.7 vs. 49.1 ± 2.6%). Onset of contractile response did not differ for 5HT (P = 0.26) and ERV (P = 0.93), but onset of ME5HT contraction was not initiated (P < 0.05) in HE steers until 10(-4) compared with 10(-5) M in LE-grazing steers. For Exp. 2, maximal contractile intensities achieved with DOI were 35% less (P < 0.05), whereas those achieved with 5CT were 37% greater (P < 0.05), in steers grazing HE pastures. Contractile response to CGS did not differ between pasture groups, and there was an absence of contractile response to BW7 in both groups. There were no differences between endophyte content in contractile responses after animals were finished for >91 d. Experiment 1 demonstrated that grazing of HE pastures for 89 to 105 d induces functional alterations in blood vessels, as evidenced by reduced contractile capacity and altered serotonergic receptor activity. Experiment 2 demonstrated that grazing HE pastures alters vascular responses, which may be mediated through altered serotonin receptor activities, and these alterations may be ameliorated by the removal of ergot alkaloid exposure as demonstrated by the absence of differences in finished steers.

Selenium content in blood fractions and liver of beef heifers is greater with a mix of inorganic/organic or organic versus inorganic supplemental selenium but the time required for maximal assimilation is tissue-specific

Selenium (Se) content of feedstuffs is dependent on the Se level of the soil. Even though Se in grass and forage crops is primarily present in organic forms, Se is commonly supplemented in cattle diets in an inorganic (sodium selenite) form in geographic regions where Se soil concentrations are low. The purpose of this study was to answer two important questions about inorganic (ISe) vs organic (OSe) forms of dietary supplementation of Se (3 mg/day) to growing beef heifers (0.5 kg/day): (1) what would the effect of supplementing Se with an equal blend of ISe:OSe (Mix) have on Se tissue concentrations and (2) how long does it take for the greater assimilation with OSE to occur and stabilize? A long-term (224 day) Se dietary supplementation trial was conducted with serial sampling performed (days 28, 56, 112, and 224) to determine the length of time required to achieve Se supplement (OSE, Mix, and ISe)-dependent changes in Se assimilation in blood fractions and liver tissue. Forty maturing Angus heifers were fed a corn silage-based diet for 98 days with no Se supplementation, and then a cracked corn/cottonseed hull-based diet (basal diet) without Se supplementation for 74 days. Liver biopsies were taken for Se analysis, and heifers were fed the same diet for another 14 days. Heifers were assigned (n = 10) to one of four Se treatment groups such that basal liver Se contents were stratified among groups, and then fed enough of the basal diet (0.08 mg Se per day) and a mineral-vitamin mix that provided 0.16 (control) or 3.0 mg Se per day in ISe (sodium selenite), OSe (Sel-Plex(®)), or Mix (1:1 ISe:OSe) form to support 0.5 kg/day growth for 224 days. More Se was found in whole blood, red blood cells, serum, and liver of Mix and OSe heifers than ISe heifers, and all were greater than control. Se content either increased until day 56 then was stable (liver and plasma), or was stable until day 56 (whole blood) or day 112 (red blood cells) and then increased steadily through day 224, for all supplemental Se treatments. These data indicate that a 1:1 mix (1.5 mg Se:1.5 mg Se) of supplemental ISe and OSe is equal to 3 mg/day OSe supplementation and greater than 3 mg/day ISe supplementation. The data also indicate that Se levels stabilized in liver and plasma by 56 to 112 days whereas whole blood and red blood cell concentrations were still increasing through 224 days of supplementation, regardless of the form of supplemental Se.

Bovine neuronal vesicular glutamate transporter activity is inhibited by ergovaline and other ergopeptines

l-Glutamate (Glu) is a major excitatory neurotransmitter responsible for neurotransmission in the vertebrate central nervous system. Vesicular Glu transporters VGLUT1 and VGLUT2 concentrate (50mM) Glu [Michaelis constant (measuring affinity), or K(m),=1 to 4mM] into synaptic vesicles (SV) for subsequent release into the synaptic cleft of glutamatergic neurons. Vesicular Glu transporter activity is dependent on vacuolar H(+)-ATPase function. Previous research has shown that ergopeptines contained in endophyte-infected tall fescue interact with dopaminergic and serotoninergic receptors, thereby affecting physiology regulated by these neuron types. To test the hypothesis that ergopeptine alkaloids inhibit VGLUT activity of bovine cerebral SV, SV were isolated from cerebral tissue of Angus-cross steers that were naive to ergot alkaloids. Immunoblot analysis validated the enrichment of VGLUT1, VGLUT2, synaptophysin 1, and vacuolar H(+)-ATPase in purified SV. Glutamate uptake assays demonstrated the dependence of SV VGLUT-like activity on the presence of ATP, H(+)-gradients, and H(+)-ATPase function. The effect of ergopeptines on VGLUT activity was evaluated by ANOVA. Inhibitory competition (IC(50)) experiments revealed that VGLUT-mediated Glu uptake (n=9) was inhibited by ergopeptine alkaloids: bromocriptine (2.83±0.59μM)<ergotamine (20.5±2.77μM)<ergocornine (114±23.1μM)<ergovaline (137±6.55μM). Subsequent ergovaline kinetic inhibition analysis (n=9; Glu=0.05, 0.10, 0.50, 1, 2, 4, 5mM) demonstrated no change in apparent K(m). However, the maximum reaction rate (V(max)) of Glu uptake was decreased when evaluated in the presence of 50, 100, and 200μM ergovaline, suggesting that ergovaline inhibited SV VGLUT activity through a noncompetitive mechanism. The findings of this study suggest cattle with fescue toxicosis may have a decreased glutamatergic neurotransmission capacity due to consumption of ergopeptine alkaloids.

Ergopeptines bromocriptine and ergovaline and the dopamine type-2 receptor inhibitor domperidone inhibit bovine equilibrative nucleoside transporter 1-like activity

Neotyphodium coenophialum-infected tall fescue contains ergopeptines. Except for interactions with biogenic amine receptors (e.g., dopamine type-2 receptor, D2R), little is known about how ergopeptines affect animal metabolism. The effect of ergopeptines on bovine nucleoside transporters (NT) was evaluated using Madin-Darby bovine kidney (MDBK) cells. Equilibrative NT1 (ENT1)-like activity accounted for 94% of total NT activity. Inhibitory competition (IC(50)) experiments found that this activity was inhibited by both bromocriptine (a synthetic model ergopeptine and D2R agonist) and ergovaline (a predominant ergopeptine of tall fescue). Kinetic inhibition analysis indicated that bromocriptine inhibited ENT1-like activity through a competitive and noncompetitive mechanism. Domperidone (a D2R antagonist) inhibited ENT1 activity more in the presence than in the absence of bromocriptine and displayed an IC(50) value lower than that of bromocriptine or ergovaline, suggesting that inhibition was not through D2R-mediated events. These novel mechanistic findings imply that cattle consuming endophyte-infected tall fescue have reduced ENT1 activity and, thus, impaired nucleoside metabolism.