Endophyte-infected Tall Fescue Pastures Research Articles

Time budgets differ in horses during continuous and space-restricted rotational grazing

Horses can become obese and develop related health issues such as laminitis from excessive grazing on high-quality pasture grass; limiting pasture intake can allow weight loss to occur. The objective of this study was to determine the effect of space-restricted rotational grazing on body weight (BW) and time budgets in horses. Eight mature geldings and mares with maintenance-only requirements were randomly assigned to either a space-restricted rotational grazing group (SRG; BW 512 ± 6 kg; n = 4) or a continuous grazing group (CG; BW 517 ± 49 kg; n = 4) for 42 d SRG horses grazed an area with dimensions to provide 80–90 % of mean digestible energy requirement for the 4 horses over a 7-d grazing period; whereas, the CG horses continuously grazed similar non-toxic endophyte-infected tall fescue pasture providing greater than maintenance requirements for the 42 d Horses in the SRG group were moved to a new area every 7 d for 6 weeks. On d 7 at 1600 h of each week, horses were brought inside, and feed was withheld overnight. At 0700 h the next day, BWs were recorded prior to turnout. Observers recorded behaviors simultaneously on SRG and CG horses every six minutes throughout the day three days per week according to an ethogram. This included 30 s scans of all horses. Proportion of grazing and standing had an inverse relationship. Proportion of grazing was affected by the treatment by time interaction, which grazing was displayed more in SRG than CG during weeks 2 and 3, and then reversed weeks 4, 5 and 6.

PSI-7 Evaluating the Relationship of Puberty Status at 10 Months of Age with Heifer Characteristics

Abstract The objective was to evaluate the relationship of heifer puberty status at 10 months of age with body weight (BW), hair shedding score (HSS), and dam age. Puberty status was assessed at 10 months of age on 177 fall-born, Simmental × Angus heifers (birth date 9/26/2020 ± 18.7 d) using fabric heat patches (Estrotect; Hermitage, Tennessee) for 22 d. Patches were scored as 0, 50, or 100% activated with heifers scored 50 or 100% considered pubertal. Heifers with missing patches (n = 10) were excluded from the analysis. Heifers grazed endophyte-infected tall fescue pastures from 6 to 12 months of age. Heifers were assigned HSS at 10, 11, and 12 months of age. A HSS of 1 indicates a slick summer coat and a 5 is a full winter coat. The MIXED procedure of SAS 9.4 was used to analyze data. Heifers classified as pubertal at 10 months of age had greater (P = 0.01) birth BW than prepubertal heifers (33.1 kg vs. 30.8 kg, respectively). Heifers that were pubertal at 10 months of age also had greater (P ≤ 0.05) BW at 6, 8, 10, and 12 months of age than prepubertal heifers. Additionally, pubertal heifers had greater (P = 0.01) ADG from 6 to 12 months of age while grazing. Pubertal heifers tended (P = 0.10) to have a lesser, more desirable HSS at 10 months of age and had a lesser (P < 0.01) HSS at 11 and 12 months of age compared with prepubertal heifers. Dam age was not different (P = 0.60) between heifer puberty status at 10 months of age. In conclusion, pubertal heifers were heavier at birth, heavier from 6 to 12 months, and had more desirable HSS compared with prepubertal heifers at 10 months of age.

Effects of overseeding red clover in endophyte-infected tall fescue pastures on steer physiology and performance

The objective of this research was to determine the effects of overseeding red clover on cattle grazing endophyte-infected tall fescue (E+ TF) pastures. A grazing study was conducted in the springs of 2016 (75 d) and 2017 (61 d). Before the start of the study, four 3-ha pastures with cool-season grass (predominately E+ TF) were blocked and randomly assigned to a control treatment (TF CON) or a broadcasted red clover treatment (TF+RC). Steers (n = 6 tester steers per pasture) were allocated to each pasture by BW. Pastures were divided into two 1.5-ha paddocks to allow for 14-d rotational put-and-take stocking. Serum prolactin was assayed on the last day of grazing, and selected tester steers from each pasture (n = 3) were moved to pens for Doppler ultrasound measurements, 7 d after grazing. Data were analyzed by repeated measures using the mixed procedure of SAS. Red clover was successfully established in TF+RC pastures (2016: 36% and 2017: 57%, pasture ground cover). The TF+RC pastures had less ADF and NDF and more true in vitro digestible DM than TF CON pastures after grazing ( P < 0.01, in all cases). However, there was no effect of TF+RC on forage mass ( P = 0.08) or pasture carrying capacity ( P = 0.19). Steers grazing TF+RC pastures had 53% and 58% greater ADG ( P = 0.03) and BW gain per hectare ( P = 0.01) than TF CON steers, respectively. Serum prolactin at the termination of grazing was almost 3 times greater in TF+RC steers than in TF CON steers ( P = 0.01). Additionally, 7 d after grazing, TF+RC steers had 44% larger caudal artery luminal areas than TF CON steers ( P < 0.01). Overseeding red clover in E+ TF pastures is an effective strategy for reversing the adverse effects of fescue toxicosis and improving cattle performance.

272 Effect of Frame Size and Supplementation on Performance and Carcass Characteristics of Beef Cattle Finished on Novel Endophyte-infected Tall Fescue Pastures

Abstract Objectives were to investigate the effects of frame score (FS) and supplementation on performance and carcass characteristics of cattle finished on novel endophyte-infected fescue pastures. This 2-yr experiment used 80 Angus-sired, crossbred steers and heifers bred for divergent FS. Cattle were allotted to 5 treatments: 1) non-supplemented small frame (S-NON; FS = 3.0 ± 0.9), 2) supplemented small frame (S-SUPP), 3) non-supplemented large frame (L-NON; FS = 4.7 ± 0.6), 4) supplemented large frame (L-SUPP), and 5) grain-based control feedlot ration (CON; FS = 4.2 ± 0.6; target ADG = 1.36 kg/day). Daily rations were delivered individually using Calan gates. Pasture supplement contained corn gluten feed, a commercially available rumen-protected prilled vegetable fat, and dried molasses fed at 0.5% of BW. Treatments started on 7/8/2019 and 5/21/2020, and ended in November of each yr when cattle were slaughtered at a commercial abattoir. Results were analyzed using PROC MIXED of SAS with main effects of treatment, sire, sex, yr, and yr x treatment, with contrast statements comparing large vs. small frame, pasture supplemented vs. non-supplemented, and control vs. pasture groups. As expected, CON had greater (P &amp;lt; 0.001) growth performance (final BW and ADG) and carcass characteristics (HCW, subcutaneous fat, marbling, dressing percentage (DRESS%) than pasture groups, and tended to have greater (P=0.053) REA. Relative to pasture groups, CON had greater (P &amp;lt; 0.001) Minolta L* and a* lean tissue values, and decreased (P &amp;lt; 0.001) b* values for fat tissue. While non-supplemented cattle had decreased (P = 0.016) yield grades (YG), supplemented cattle had greater (P &amp;lt; 0.050) final BW, ADG, subcutaneous fat, HCW, marbling, and DRESS% compared to non-supplemented cattle. Small framed cattle tender to have decreased (P = 0.056) YG; but, large framed cattle had greater (P = 0.006) HCW, and tended (P = 0.060) to have greater ultrasound subcutaneous fat. Results support low-level supplementation in pasture-finishing systems to improve carcass value.

PSIV-8 Effects of Late Gestation Calcium Salts of Fatty Acids Supplementation to Beef Cows on Offspring Finishing Phase Performance and Carcass Characteristics

Abstract The objective was to investigate the effects of late-gestation supplementation of Ca salts of fatty acids to beef cows on the finishing phase growth performance and carcass characteristics of the steer progeny. Ninety-six multiparous, fall-calving, Angus × Simmental cows (BW = 601 ± 76 kg) were stratified by BW, BCS, and age and randomly allotted into 8 endophyte-infected tall fescue pastures with 12 cows/pasture. Cows were supplemented with soybean hulls mixed with either 155 g/cow/d of EnerGII (SFA/MUFA; enriched with palmitic and oleic acids) or 80 g/cow/d of Prequel + 80 g/cow/d of Strata (PUFA; enriched with linoleic acid, EPA, and DHA) for the last 77 ± 6 d of gestation. Steer progeny (n = 70) were weaned at 186 ± 6 d of age and transported to feedlot. Steers were fed receiving diets for 3 weeks and transitioned to finishing diets and adapted to GrowSafe feed bunks for individual daily feed intake measurement. Steers were weighed every 28 d during the finishing phase. Steers were slaughtered at commercial abattoir at 432 ± 6 d of age, and carcass data were obtained from USDA camera grading system. Data were analyzed using the MIXED procedure of SAS, and repeated measure was used for BW. There were no differences (P ≥ 0.13) for BW, ADG, DMI, or feed conversion during the finishing phase. There was no differences (P ≥ 0.22) observed in hot carcass weight, dressing percentage, 12th rib fat thickness, yield grade, ribeye area, marbling score, or KPH fat. In conclusion, maternal supplementation of Ca salts of fatty acids during late gestation did not affect steer progeny growth performance during the finishing phase or carcass characteristics.

PSIX-7 Grazing toxic endophyte-infected tall fescue does not influence pancreatic or small intestinal digestive enzyme activities in beef steers

Abstract The objective of this experiment was to determine the influence of toxic endophyte-infected tall fescue exposure on pancreatic and small intestinal digestive enzyme activities in steers. Twelve fescue-naive beef steers [693 ± 42.7 kg of body weight (BW)] were stratified by BW and randomly assigned within BW ranks to graze non-toxic endophyte-infected tall fescue (NTE, n = 6; 0.01 ± 0.009 mg ergovaline + ergovalinine/kg) or toxic endophyte-infected tall fescue (TE, n = 6; 0.50 ± 0.048 mg ergovaline + ergovalinine/kg) pastures for 84 d. After the grazing period, steers were weighed and then slaughtered in three groups for tissue collection. A 1-m segment of the small intestine was collected 5-m distal to the pyloric sphincter. Subsamples of the small intestinal mucosa and pancreas were collected, homogenized in saline, and assayed for protein concentration. Pancreatic and small intestinal digestive enzyme activities were assayed. Data were analyzed using the GLM procedure of SAS as a randomized complete block design for effects of treatment and slaughter group (blocking factor). Steers grazing NTE pastures had a greater (P &amp;lt; 0.001) average daily gain (0.282 vs -0.631 kg/d) and final BW at slaughter (739 vs 620 kg) than steers grazing TE pastures. Small intestinal segment mass and mucosal density (P ≥ 0.16) were not influenced by treatment. Grazing TE pasture did not influence (P ≥ 0.21) pancreatic or small intestinal protein concentrations. Pancreatic α-amylase and trypsin activity per gram pancreas (P ≥ 0.21) or per gram pancreatic protein (P ≥ 0.30) were not influenced by fescue treatment. Small intestinal glucoamylase, isomaltase, and maltase activities did not differ between steers grazing NTE or TE pastures when expressed per gram of intestinal tissue (P ≥ 0.47) or per gram of intestinal protein (P ≥ 0.60). These data indicate that decreased gains observed in cattle consuming TE are not a result of decreased pancreatic or small intestinal digestive enzyme activities.

PSIV-26 Effects of extended-release eprinomectin on heifer growth and reproductive performance while grazed on endophyte-infected tall fescue or housed in drylot

Abstract The objective was to assess the effects of an extended-release eprinomectin (LongRange) on beef heifer reproductive performance when grazed on endophyte-infected tall fescue or housed on drylot. In a split-plot design, fall-born, Angus × Simmental heifers (n = 153) were stratified by BW and divided into 6 groups. Groups were randomly assigned environmental treatments: grazed endophyte-infected tall fescue (pasture) or maintained in drylot and fed alfalfa hay. Within a group, heifers were randomly assigned to LongRange (LR) or saline (control). Heifers were dewormed with oral fenbendazole (SafeGuard) to minimize parasite load before trial initiation. On d 140 and final pregnancy check, body weight (BW) and body condition score (BCS) were collected; BW was also collected at time of artificial insemination (AI). Hair coat score (HCS), fecal egg count (FEC), packed cell volume (PCV), and respiration rates (RR) were collected on d 140. Data were analyzed using the MIXED procedure of SAS. Environment × treatment effects for BW were detected (P ≤ 0.01) at d 140 and at overall pregnancy confirmation; LR increased BW to a greater magnitude in pasture than in drylot heifers. At breeding, LR increased (P = 0.01) heifer BW compared to control. On d 140, LR increased (P = 0.01) heifer BCS compared to control. On d 140, pasture heifers tended (P = 0.08) to have greater RR than drylot heifers. Heifer AI pregnancy rates were not affected (P ≥ 0.21) by treatments. Environment × treatment effects for overall pregnancy were detected (P = 0.03); LR increased overall pregnancy rate in pasture compared to drylot heifers and LR tended to increase overall pregnancy rate compared with control in pasture heifers. In conclusion, LongRange increased BW to a greater extent in pasture than in drylot and tended to increase heifer final pregnancy rate compared to control on pasture.

PSI-2 Effects of extended release eprinomectin on heifer performance while grazed on endophyte-infected tall fescue or housed in drylot

Abstract Objectives were to evaluate the effects of LongRange, an extended-release eprinomectin, on beef heifer performance while grazed on endophyte-infected tall fescue or housed in drylot. Fall-born, Angus × Simmental heifers (n = 153) were utilized in a split-plot design. Heifers were stratified by BW and assigned to 6 groups. Groups were randomly assigned to 1 of 2 environmental treatments: grazed endophyte-infected tall fescue (Pasture) or housed in drylot and fed alfalfa hay. Within environmental treatment groups, heifers were randomly assigned to LongRange (LR) or control (Saline). Prior to experiment initiation, heifers were treated with oral fenbendazole (SafeGuard) to minimize parasite load. Data were analyzed using the MIXED procedure of SAS. At d 0, 56, and 112, heifer BW, ADG, BCS, hair coat score (HCS), and fecal egg counts (FEC) were collected. Treatments did not affect (P ≥ 0.17) BW on d 0 and 56. On d 112, drylot heifers tended (P = 0.08) to be heavier than pasture heifers and LR increased (P = 0.01) BW. There was an interaction (P = 0.02) for ADG; LR increased ADG to a greater magnitude in pasture than drylot heifers. On d 0, 56, and 112, there was no interaction or LongRange effect (P ≥ 0.11) on BCS; however, pasture heifers had greater (P = 0.05) d 112 BCS than drylot heifers. On d 56, there was an interaction (P = 0.01) on HCS; LR decreased HCS in pasture heifers, but did not affect HCS in drylot heifers. Although treatment did not effect (P ≤ 0.33) FEC at d 0, there was an interaction (P = 0.01) observed on d 56. LongRange decreased FEC in pasture heifers but not in drylot. In conclusion, LongRange increased heifer growth performance with a greater difference for heifers grazing tall fescue, compared with heifers in drylot.

261 Prescribed burning of endophyte-infected tall fescue pastures: Effects on forage production, ergot alkaloid concentrations, and stand composition

Abstract Prescribed fire may be a non-chemical alternative for seedhead suppression in endophyte-infected tall fescue forage systems. A study was conducted to observe the effects of a single prescribed burn on seed head production, ergot alkaloid concentration, forage production, forage quality, and stand composition in K31 tall fescue plots (endophyte infection=96%). Treatments of an undisturbed control (CON), March mow (MOW), March burn (EARLY), and April burn (LATE) were randomly applied to 56 square meter plots with ten replicates per treatment. Plots were sampled for forage quality and ergot alkaloid concentrations monthly from May to October. Forage production and species composition was recorded in June and October. Fescue seedhead count was conducted in May. After June sampling, plots were clipped to a height of 10 cm and litter was removed to simulate spring grazing. CON had greater (P &amp;lt; 0.01) total forage production in June than other treatments. MOW had greater (P &amp;lt; 0.01) forage production (≤107 kg/ha) than EARLY and LATE in June. There was no effect (P = 0.30) of treatments on forage production in October. LATE burn reduced (month × trt; P = 0.02) ergovaline concentration in June but all treatments were above the established threshold (150 ppb) for fescue toxicosis. Fescue seed head frequency was decreased (P &amp;lt; 0.01) by 50% in LATE plots. There was no treatment effect (P ≥ 0.22) on forb and non-fescue grass frequency in May, but warm season grass frequency was greater (P &amp;lt; 0.01) in LATE plots in October. Crude protein in LATE was greater than other treatments in May and both LATE and CON were greater than other treatments in June (P &amp;lt; 0.01). Neutral detergent fiber for LATE was less than other treatments in May and June (P &amp;lt; 0.01). Under conditions of this experiment, prescribed fire decreased seed head count and ergot alkaloid concentration, with a modest reduction in forage production.

Feeding strategies and shade type for growing cattle grazing endophyte-infected tall fescue

Two experiments were conducted to determine animal performance of alternative feeding strategies to heifers grazing endophyte-infected tall fescue during summer months. In Experiment 1, 40 Limousin heifers (261 (40) kg initial BW) were stratified by weight and assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments. Diet factors were either a spring harvested tall fescue silage diet fed ad libitum in grass traps (Silage) or grazing endophyte-infected tall fescue pasture with grain supplement (Grain; 2.1 kg DM hd−1 d−1), and shade factors were either natural (NAT; trees) or artificial (ART; 13.38 m2/pasture of 80% shade cloth) shade for 80 days. In Experiment 2, 40 Limousin heifers (277 (44) kg initial BW) were stratified by weight and assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments. Diet factors were either a traditional grain supplement (Control) or feather-meal supplement (FM) while grazing endophyte-infected tall fescue pasture, and shade factors were either NAT or ART shade for 98 days. Control and FM supplements provided an estimated 56 and 175 mg metabolizable arginine/kg BW, respectively. Heifers were weighed on two consecutive days at the start and end of each experiment. In Experiment 1, weight gain of heifers was greater (P < 0.05) in Grain than Silage treatments (0.55 vs. 0.13 kg/d) and was greater (P < 0.05) for NAT than ART shade (0.39 vs. 0.29 kg/d). Cost of gain was greater (P < 0.05) for heifers fed Silage than Grain (7.26 vs. 1.56 $/kg of gain). In Experiment 2, there was no difference (P > 0.10) in weight gain or cost of gain between Control and FM supplements. Heifers with NAT shade had a greater (P < 0.05) weight gain (0.74 vs. 0.65 kg/d) and lower (P < 0.05) cost of gain (2.01 vs. 2.27 $/kg of gain) than ART shade. In conclusion, feeding early-spring harvested tall fescue silage or a supplement with high metabolizable arginine did not improve performance, and current recommendations for design of artificial shade structures may not be adequate for cattle grazing endophyte-infected tall fescue during summer.

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.

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.

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.

Pre- and postweaning performance by cows and calves that grazed toxic or nontoxic endophyte-infected tall fescue pastures

Negative effects on cattle grazing tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] infected with the wild-type endophyte Neotyphodium coenophialum (E+) are well documented, but information about the carryover effects on weaned calves is limited. Our objective was to compare pre- and postweaning performance by spring-calving cows and calves grazing E+ with that by cows grazing a nontoxic endophyte–tall fescue association (NE+). Pregnant Gelbvieh × Angus crossbred cows (n = 136; 492 ± 19.2 kg of initial BW) were stratified by BW and age and allocated randomly to one of four 10-ha pastures in yr 1 (October 15) and one of eight 10-ha pastures in yr 2 (November 30). Pastures were allocated randomly before establishment to E+ or NE+. Cows remained on their assigned pastures until weaning in yr 2 but were removed from NE+ in the summer of yr 1 because of low forage mass. After weaning, calves grazed bermudagrass [Cynodon dactylon (L.) Pers.] followed by cool-season annual grasses. Cow BW and pregnancy rate, and calf weaning weight and preweaning gain were greater (P < 0.05) from NE+ versus E+. Weaning weight differentials were maintained throughout postweaning production phases, resulting in heavier HCW (P < 0.05) by steers and a tendency for greater (P < 0.10) subsequent calving rates by heifers. Therefore, replacing E+ with NE+ may improve preweaning cow and calf performance and heifer reproductive rates, but postweaning gains may not be affected by previous exposure to E+.

The Effects of Steroid Implant and Dietary Soybean Hulls on Estrogenic Activity of Sera of Steers Grazing Toxic Endophyte-Infected Tall Fescue Pasture.

Soybean hulls (SBHs) have been fed to cattle pasturing on endophyte-infected tall fescue in attempts to increase rate of gain. Literature reports indicated some symptoms associated with fescue toxicosis were ameliorated by the use of steroidal implants containing estradiol (E2) and progesterone [implantation (IMP)], feeding SBHs, or the combination of the two. While the mechanism for amelioration was unclear, the SBHs were postulated as acting as a diluent of the toxic factors of the fescue. Alternatively, estradiol and phytoestrogens of SBHs might be acting through relaxation of the persistent vasoconstriction found in animals ingesting ergot alkaloids of endophyte-infected fescue. If so, estrogenic activity of serum of steers receiving SBHs, IMP, or a combination of the two should be elevated. Using the cellular proliferation assay of estrogenicity (E-Screen), estradiol equivalents (E2Eqs) were determined on both SBHs and the serum of steers from a previously reported study. Range of SBHs was 5.0–8.5 ng Eqs g−1 DM (mean 6.5, n = 4 from different commercial sources of SBHs). At the rate fed, theoretically calculated blood E2Eq could be physiologically relevant (~80 pg mL−1, based on 2.3 kg SBHs d−1, 300 kg steer, 5.7% blood volume, and 10% absorption). Serum E2Eqs did increase in steers (P ≤ 0.05) with steroidal implants or fed SBHs by 56 and 151% over control, respectively, and treatments were additive (211% increase). Serum prolactin was also greatest for the SBH + IMP group (188 ng mL−1, P < 0.05), concentrations comparable to values reported for steers grazing endophyte-free fescue. Prolactin in the SBH group was higher than IMP or control groups (146 versus 76 and 60 ng mL−1, respectively). Still unknown is if additional E2Eqs from dietary phytoestrogens or exogenous sources of estradiol can further reduce symptoms of fescue toxicosis. The E-Screen assay was an effective tool in monitoring serum for estrogenic effects of dietary supplementation with SBHs or estrogenic implants.

Vasoconstrictive responses of the testicular and caudal arteries in bulls exposed to ergot alkaloids from tall fescue

ABSTRACT Color Doppler ultrasonography was used to evaluate vasoconstrictive responses of the testicular artery in yearling bulls to ergot alkaloids (Neotyphodium coenophialum) produced by a fungal endophyte that infects tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]. Alkaloid-induced constriction of the testicular artery could disrupt thermoregulation. Luminal areas of the testicular artery were monitored and analyzed for 2 experiments that were designed to evaluate fertility responses of bulls to toxic endophyte-infected tall fescue. Experiment 1 (pen experiment) compared diets containing toxic endophyte-infected or endophyte-free tall fescue seed, and Exp. 2 (grazing experiment) compared grazing diets consisting of toxic endophyte-infected and nontoxic endophyte-infected tall-fescue pasture. In Exp. 1 ultrasound images were acquired on 3 dates during the 126-d of feeding and in Exp. 2 on 4 dates during the 155-d of grazing. Luminal area of the caudal artery also was monitored as an indicator of alkaloid-induced vasoconstriction. Caudal and testicular arteries for the toxic treatment responded similarly between experiments. Across imaging dates for Exp. 1, caudal artery lumens for the toxic diet averaged 42% less (P

Intake estimation of horses grazing tall fescue (Lolium arundinaceum) or fed tall fescue hay

Six mature geldings of light horse breeds (557 ± 37 kg) were randomly assigned to a nontoxic endophyte-infected tall fescue hay (n = 3) or pasture treatment (n = 3) in a crossover design with 14-d periods to estimate DMI with alkane markers and to compare DMI of hay and pasture. When fed pasture, horses were housed in stalls from 0700 to 1300 h daily with access to water and then grazed pasture as a group in a single 0.4 ha pasture from 1300 to 0700 h. When fed hay, horses were maintained individually in stalls and given access to hay ad libitum from 1300 to 0700 h. All horses were individually fed 225 g oats twice daily treated with hexatriacontane (C36; external marker) and fecal samples were collected at 0700 and 1900 h on d 10 to 14. Fecal samples were mixed, dried, subsampled, and analyzed for tritriacontane (C33) and hentriacontane (C31) as internal markers and C36 as the external marker using gas chromatography. Estimated hay DMI using either C33 (1.75 kg/100 kg BW) or C31 (1.74 kg/100 kg BW) as internal alkane marker did not differ (P = 0.55) from measured hay DMI (1.70 kg/100 kg BW). Pasture DMI and DM digestibility (DMD) estimated with C31 (2.24 kg/100 kg BW and 53.1 g/100 g DMI) or with C33 (2.34 kg/100 kg BW and 56.2 g/100 g DMI) was greater (P = 0.05) than hay DMI and DMD (1.74 kg/100 kg BW and 44.5 g/100 g DMI). Intake estimated with C33 or C31 did not differ (P = 0.35) during hay or pasture. In conclusion, alkanes can be used to estimate pasture or hay DMI and DMD, and pasture intake exceeded hay intake when offered ad libitum.

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 fescue12

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.

Integrating bermudagrass into tall fescue-based pasture systems for stocker cattle1

The daily BW gain of stocker steers grazing tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor.