Effects of grazing endophyte-infected tall fescue on eCG and progestogen concentrations from gestation days 21 to 300 in the mare

The influence of grazing endophyte-infected tall fescue on endometrial cup formation and function, progestogen production, and embryonic and fetal development were examined in pregnant mares between Day 21 and Day 300 of gestation. Total immunoreactive progestogens and equine chorionic gonadotropin (eCG) concentrations were compared between untreated controls (endophyte-free, n = 12) and treated mares (endophyte-infected, n = 12). There were no differences in endometrial cup formation or function, as determined by eCG concentrations at Days 45, 60, 75, 90 and 120 (P > 0.05) between mares grazing endophyte-infected and endophyte-free tall fescue. Mares grazing the endophyte-infected tall fescue had lower total progestogen concentrations (P < 0.01) from Days 90 to 120 than the mares grazing endophyte-free tall fescue. Embryonic development based on mean vesicle height was not affected by endophyte exposure. No pregnancies were lost by mares in either treatment group during the trial period. The results of this study indicate that grazing endophyte-infected tall fescue between Day 21 and Day 300 does not alter endometrial cup formation and function, or result in increased pregnancy losses during this period. Lower progestogen concentrations between Days 90 and 120 with exposure to endophyte-infected tall fescue could reflect decreased luteal progesterone production.     

Growth and ovarian function of weanling and yearling beef heifers grazing endophyte-infected tall fescue pastures

Growth and ovarian function of crossbred beef heifers grazing low and high endophyte-infected tall fescue pastures were studied for 2 successive years. In April of each year, 20 weanling and 20 yearling heifers were included in the study. All heifers were weighed at 28-d intervals for 112 d. Blood samples were collected from each heifer on Day 0 and +7 of each of five 28-d periods and analyzed for progesterone concentration. Heifers with progesterone concentrations >/= 1.5 ng/ml on either or both Day 0 and +7 were classified as having normal cyclic ovaries. High endophyte-infected fescue pastures adversely altered the ovarian activity (P < 0.05) of weanling heifers in both years. In each trial, average weight gains were lower (P < 0.05) in yearling and weanling heifers grazing the high endophyte-infected pastures than in heifers grazing low endophyte-infected pastures. In 1992, heifers were synchronized with PGF(2alpha) administered on Days 101 and 112. Blood samples were collected on 0, 4, 8 and 12 d after the second PGF(2alpha) injection for progesterone analysis. Heifers grazing high and low endophyte-infected pastures were pastured separately with 4 bulls each and were given heatmount detectors. At 96 h, less estrus activity was observed (P < 0.10; power=0.63) in weanling heifers grazing the high vs. low endophyte pastures although pregnancy rates were similar for all groups. Progesterone concentrations suggested that weanling heifers on the high endophyte pastures had a higher incidence of luteal dysfunction after PGF(2alpha) synchronization. In summary, high endophyte-infected pastures decreased growth in both weanling and yearling heifers, ovarian activity and luteal function were adversely altered in weanling heifers with subsequent decreased estrus response to estrus synchronization.     

A preliminary study of growth, serum prolactin and reproductive performance of beef heifers grazing Acremonium coenophialum -infected tall fescue

In an experiment with a 2x2 factorial arrangement of treatments, 32 virgin Angus heifers were used to study effects of tall fescue endophyte Acremonium coenophialum and energy supplementation on reproductive performance. Treatments were feeding of endophyte-free (EF) or endophyte-infected (EI) tall fescue without (0%) and with energy supplementation at one percent group mean body weight (1%). Blood samples were collected at 28-day intervals for prolactin (PRL). Starting 21 days before the breeding season, blood was also collected weekly for progesterone (P(4)) and PRL. After 99 days of grazing, heifers received Syncro-Mate-B (SMB) and were then artificially inseminated over a 30-day period. Heifers on EI-0% had a lower (P<0.05) average final body weight. Highest average daily gain was observed in heifers fed EF-1% (0.98 kg/day), whereas, heifers fed EI-0% had lowest average daily gain (0.53 kg/day; P<0.05). Endophyte-infected fescue depressed serum PRL concentrations (171 and 143 ng/ml vs 70 and 85 ng/ml; EF-0% and EF-1% vs EI-0% and EI-1%, respectively; P<0.05). No differences were observed among treatments in luteal activity before or after SMB, in pregnancy rates after a synchronized estrus or in overall pregnancy rates during the 30-day breeding season. Endophyte-infected fescue decreased average daily gain and depressed serum concentrations of prolactin, but had no effect on reproductive performance as measured in this study.     

Endophyte-infected tall fescue diet alters gene expression in heifer luteal tissue as revealed by interspecies microarray analysis

Cattle consuming endophyte-infected tall fescue grass have an associated reduction in circulating progesterone and reduced reproductive rates. In this study, commercially available rat microarrays were used to analyze the gene expression in luteal tissues from heifers fed endophyte-free fescue, endophyte-infected fescue, or endophyte-infected fescue supplemented with the dopamine (DA) antagonist, domperidone. The number of hybridized spots represented approximately 40% of the total 10,000 rat genes/ESTs evaluated. Each luteal sample was analyzed in triplicate, resulting in within treatment correlation coefficients of >/=0.98. Median values of mRNA abundance from luteal tissue taken from the endophyte-infected fed heifers revealed 598 genes and ESTs that were down regulated and 56 genes and ESTs that were upregulated compared with luteal mRNA values from the endophyte-free treatment. There were fewer comparative differences between median values from luteal mRNA from the endophyte-free versus feeding endophyte-infected plus domperidone treated heifers. Only 19 genes and ESTs were upregulated and two were down-regulated.     

Interaction of endophyte-infected fescue and heat stress on ovarian function in the beef heifer.

The objective of the experiment was to examine the interaction of endophyte-infected tall fescue and environmental temperature on follicular and luteal development and function in beef heifers. Heifers were fed endophyte-free or endophyte-infected tall fescue seed at thermoneutral or heat stress temperatures (n = 6/treatment) 4 wk before and 3 wk after synchronized ovulation. All heifers were subjected to thermoneutral conditions (19 degrees C, 50% relative humidity) from Days -7 to -2; temperature increased incrementally from Days -1 to 0 and cycled between 25 degrees C and 31 degrees C between Days 1 and 20 for heat-stressed heifers. Serum was collected and ovaries monitored every other day after induced luteolysis between Days 1 and 23 or until ovulation. Size and location of follicles >4 mm and corpora lutea were recorded. Serum concentrations of prolactin were reduced in heat-stressed heifers fed infected seed and both heat stress and infected seed decreased total cholesterol. Rectal temperature and respiration rate were greatest in heifers fed the infected seed when exposed to maximal temperatures. Heat stress led to reduced diameter of the corpus luteum and serum progesterone compared with thermoneutral conditions. Progesterone was reduced more so in heifers fed infected seed. The combination of infected seed and heat stress was associated with reduced diameter of the preovulatory dominant follicle, and consumption of infected seed led to fewer large follicles during the estrous cycle. Both stressors led to reduced serum estradiol. Impaired follicle function may explain reduced pregnancy rates commonly observed in heifers grazing infected tall fescue pasture.     

The effect of feeding tall fescue seed infected by Acremonium coenophialum on pregnancy and parturition in female rats

1. Female Sprague-Dawley rats (Rattus norvegicus) were randomly assigned to various dietary treatments containing: (1) 100% Purina rodent chow, ad libitum; (2) same as 1, but restricted to daily intake of 7; (3) 50% rodent chow (w/w) and 50% endophyte-free tall fescue (Festuca arundinacea) seed; (4) same as 3, but restricted to intake of 5; (5) 50% rodent chow, 25% endophyte-free tall fescue seed and 25% endophyte-infected (Acremonium coenophialum) tall fescue seed; (6) 50% rodent chow, 12.5% endophyte-free and 37.5% endophyte-infected tall fescue seed; and (7) 50% rodent chow and 50% endophyte infected tall fescue seed. 2. Average daily feed intakes and average daily weight gains decreased with higher levels of endophyte infected seed. 3. Frequency of litter production was affected by all endophyte-infected containing diets. 4. Conception was reduced only in dietary treatment (7). 5. Litter weights, number of pups per litter and weight per pup were proportionally reduced as higher levels of infected seed were incorporated in the ingested diets.     

Changes in ovarian function in mature beef cows grazing endophyte infected tall fescue

The objective was to examine follicular and luteal development and function in mature, lactating beef cows grazing endophyte free (E-) or endophyte infected (E+) tall fescue during the early postpartum period. Angus, Hereford, and Angus x Hereford cows were exposed to pasture for 37-39 days before synchronized estrus. Serum concentrations of prolactin were evaluated during the luteal phase before the synchronized estrus. Every Monday, Wednesday, and Friday for one estrous cycle ovaries were monitored by transrectal ultrasonography and blood was collected for determination of serum concentrations of progesterone and estradiol in cows that responded to synchronization. Signs of fescue toxicosis in E+ cows included decreased serum concentrations of prolactin (84.9+/-13.6 pg/ml versus 32.3+/-12.0 pg/ml; P < 0.009) measured during the luteal phase (day 37 of grazing) and decreased body condition of cows and weight of cows and calves (P < 0.001). Neither serum concentrations of progesterone or estradiol, nor diameter of the CL differed between treatments. Diameter of the largest follicle tended to be smaller for cows grazing E+ fescue, especially between days 8 and 12 of the estrous cycle (P < 0.08). Numbers of class 1 (3-5 mm) and class 3 (>10 mm) follicles were similar (P > 0.05) between treatments, but number of class 2 (6-9 mm) follicles was reduced in E+ cows for most of the cycle (days 10 through 20; P < 0.03). Length of synchronized estrous cycle, days open, calving interval, and pregnancy rate at 30, 45, 60, and 90 days post-breeding was similar (P > 0.05) among treatment groups. Even though follicular dynamics (diameter of the largest follicle and number of class 2 follicles) were altered in cows grazing E+ tall fescue, follicular function was apparently not affected by ergot alkaloids.     

Embryonic loss in mares: Pregnancy rate, length of interovulatory intervals, and progesterone concentrations associated with loss during days 11 to 15

Pregnancy rates, length of interovulatory intervals, and progesterone concentrations were examined in mares which had ultrasonically detected collections of fluid in the uterine lumen and in mares which lost the embryonic vesicle during Days 11 to 15 and did not become pseudopregnant. In mares with embryonic loss, the loss rate for mares with re-established pregnancies (9 18 ) was greater (P<0.05) than the loss rate for all pregnancies (38 154 ), indicating repeatability. Pregnancy rates were higher (P<0.01) in controls (100 177 ) than in mares with intrauterine fluid collections (2 34 ) or mares with embryonic loss (10 33 ), excluding the pregnancy associated with embryonic loss. The mean length (days) of the interovulatory interval was reduced (P<0.05) in mares with intrauterine fluid collections (20.4 +/-0.9) and in mares with embryonic loss both for the intervals in which loss occurred (19.6 +/-0.7) and for intervals in which pregnancy was not detected (21.0 +/-1.0; controls, 23.5 +/-0.6). Mean progesterone concentration (ng/ml) on Day 7 was lower (P<0.05) in mares with intrauterine fluid collections (8.8 +/-1.8) and in mares with embryonic loss (12.1 +/-1.1) than in pregnant controls (17.2 +/-0.9) and nonpregnant controls (17.5 +/-0.1). The embryonic loss seemed attributable to uterine-induced luteolysis in association with uterine inflammation, but the possibility of involvement of a primary luteal inadequacy or other factors in at least some of the mares was not eliminated.     

Reproductive responses to grazing endophyte-infected tall fescue by postpartum beef cows

The objective was to determine pregnancy rate and stage of embryonic loss in response to grazing endophyte-free (E-; n = 20) or infected (E+; n = 30) tall fescue in postpartum beef cows with calves. Three weeks before estrus synchronization, cow-calf pairs were introduced to pastures (April 1999). Cows were synchronized and bred by AI after detected estrus for a period of 6 d and then by natural service for 62 d. Bulls were rotated weekly to minimize effects of fescue toxicosis on male fertility. Fetal development was monitored weekly between 30 and 60 d of pregnancy and at weaning using transrectal ultrasound. Respiration rate (52.0 +/- 1.4 vs 46.6 breaths/min; P < 0.02) and rectal temperature (39.6 +/- .09 vs 38.8 +/- .12 degrees C; P < 0.001) increased in E+ cows and serum concentrations of prolactin (7.2 vs 57.4 +/- 4.4 ng/mL; P < 0.001), total cholesterol (123.2 vs 149.6 +/- 3.6 mg/dL; P < 0.001), body condition (3.8 vs 5.2 +/- 0.15; P < 0.001; 1 = thin, 9 = fat) and adjusted weaning weight of calves (195.8 vs 210.8 +/- 4.5 kg; P < 0.02) were reduced compared to that of E- cows. Differences were not detected (E- vs E+) for estrus detection rate (84.9 +/- 10.6% vs 80.2 +/- 8.4%), pregnancy rate to synchronized estrus (41.7 +/- 11.8% vs 46.8 +/- 9.5%), overall pregnancy rate 30 d postbreeding (93.8 +/- 6.2% vs 93.5 +/- 5.1%), overall pregnancy rate at 60 d postbreeding (86.7 +/- 10.1% vs 81.2 +/- 8.3%), or serum concentrations of progesterone on day of PGF2alpha treatment (4.5 +/- 0.7 vs 4.5 +/- 0.8 ng/mL). Pregnancy losses that occurred between 30 and 60 d gestation were 6.0 (E-) vs 15.0 (E+) +/- 8.0% (P > 0.10) and occurred after environmental temperatures rose above 37.8 degrees C for three weeks. Total pregnancy losses that occurred by weaning (between 70 and 126 d of gestation) were 5.5 (E-) vs 17.6 (E+) +/- 8.0% (P > 0.10). Pregnancy rate and embryonic losses were not different between cows grazing E- and E+ tall fescue under these management conditions.     

Acute exposure to ergot alkaloids from endophyte-infected tall fescue does not alter absorptive or barrier function of the isolated bovine ruminal epithelium

Ergot alkaloids in endophyte-infected (Neotyphodium coenophialum) tall fescue (Lolium arundinaceum) have been shown to cause a reduction in blood flow to the rumen epithelium as well as a decrease in volatile fatty acids (VFA) absorption from the washed rumen of steers. Previous data also indicates that incubating an extract of endophyte-infected tall fescue seed causes an increase in the amount of VFA absorbed per unit of blood flow, which could result from an alteration in the absorptive or barrier function of the rumen epithelium. An experiment was conducted to determine the acute effects of an endophyte-infected tall fescue seed extract (EXT) on total, passive or facilitated acetate and butyrate flux across the isolated bovine rumen as well as the barrier function measured by inulin flux and tissue conductance (G_t). Flux of ergovaline across the rumen epithelium was also evaluated. Rumen tissue from the caudal dorsal sac of Holstein steers (n=6), fed a common diet, was collected and isolated shortly after slaughter and mounted between two halves of Ussing chambers. In vitro treatments included vehicle control (80% methanol, 0.5% of total volume), Low EXT (50 ng ergovaline/ml) and High EXT (250 ng ergovaline/ml). Results indicate that there is no effect of acute exposure to ergot alkaloids on total, passive or facilitated flux of acetate or butyrate across the isolate bovine rumen epithelium (P>0.51). Inulin flux (P=0.16) and G_t (P>0.17) were not affected by EXT treatment, indicating no alteration in barrier function due to acute ergot alkaloid exposure. Ergovaline was detected in the serosal buffer of the High EXT treatment indicating that the flux rate is ~0.25 to 0.44 ng/cm² per hour. Data indicate that specific pathways for VFA absorption and barrier function of the rumen epithelium are not affected by acute exposure to ergot alkaloids from tall fescue at the concentrations tested. Ergovaline has the potential to be absorbed from the rumen of cattle that could contribute to reduced blood flow and motility and lead to reduced growth rates of cattle.     

Endophytic fungus improves growth and metal uptake of Lolium arundinaceum Darbyshire ex. Schreb

The effect of endophyte infection on plant growth, cadmium (Cd) uptake, and Cd translocation was investigated using tall fescue (Lolium arundinaceum) grown in greenhouses in contaminated solution. Endophyte infection significantly increased tiller number and biomass of the host grass under both control and Cd-stress conditions. Endophyte infection not only enhanced Cd accumulation in tall fescue, but also improved Cd transport from the root to the shoot. Under 20 mg L(-1) Cd stress, the phytoextraction efficiency of endophyte-infected (EI) tall fescue was 2.41-fold higher than endophyte-free plants. Although the total Cd accumulation in EI tall fescue was insufficient for practical phytoextraction applications, the observed high biomass production and tolerance of stress from abiotic factors including heavy metals, gives endophyte/plant associations the potential to be a model for endophyte-assisted phytoremediation of metal-polluted soils.     

Connecting plant–microbial interactions above and belowground: a fungal endophyte affects decomposition

Mutualisms can strongly affect the structure of communities, but their influence on ecosystem processes is not well resolved. Here we show that a plant–microbial mutualism affects the rate of leaf litter decomposition using the widespread interaction between tall fescue grass (Lolium arundinaceum) and the fungal endophyte Neotyphodium coenophialum. In grasses, fungal endophytes live symbiotically in the aboveground tissues, where the fungi gain protection and nutrients from their host and often protect host plants from biotic and abiotic stress. In a field experiment, decomposition rate depended on a complex interaction between the litter source (collected from endophyte-infected or endophyte-free plots), the decomposition microenvironment (endophyte-infected or endophyte-free plots), and the presence of mesoinvertebrates (manipulated by the mesh size of litter bags). Over all treatments, decomposition was slower for endophyte-infected fescue litter than for endophyte-free litter. When mesoinvertebrates were excluded using fine mesh and litter was placed in a microenvironment with the endophyte, the difference between endophyte-infected and endophyte-free litter was strongest. In the presence of mesoinvertebrates, endophyte-infected litter decomposed faster in microenvironments with the endophyte than in microenvironments lacking the endophyte, suggesting that plots differ in the detritivore assemblage. Indeed, the presence of the endophyte in plots shifted the composition of Collembola, with more Hypogastruridae in the presence of the endophyte and more Isotomidae in endophyte-free plots. In a separate outdoor pot experiment, we did not find strong effects of the litter source or the soil microbial/microinvertebrate community on decomposition, which may reflect differences between pot and field conditions or other differences in methodology. Our work is among the first to demonstrate an effect of plant–endophyte mutualisms on ecosystem processes under field conditions.     

The Effects of Endophytes on Seed Production and Seed Predation of Tall Fescue and Meadow Fescue

Fungal endophytes of grasses are often included in agricultural management and in ecological studies of natural grass populations. In European agriculture and ecological studies, however, grass endophytes are largely ignored. In this study, we determined endophyte infection frequencies of 13 European cultivars and 49 wild tall fescue (Schedonorus phoenix) populations in Northern Europe. We then examined seed production and seed predation of endophyte-infected (E+) and endophyte-free (E?) tall fescue (in wild grass populations and in a field experiment) and meadow fescue (Schedonorus pratensis; in a field experiment only). Endophytes were detected in only one of the 13 cultivars. In contrast, >90% of wild tall fescue plants harbored endophytes in 45 wild populations but were absent in three inland populations in Estonia. In three wild tall fescue study sites, 17%, 22%, and 56% of the seeds were preyed upon by the cocksfoot moth. Endophyte infection did not affect seed mass of tall fescue in the field experiment. However, seed predation was lower in E+ than E? grasses in the two tall fescue populations with higher predation rates. For meadow fescue, the mean number of seeds from E+ plants was higher than E? plants, but E? and E+ seeds had equal rates of predation by the moth. Our results suggest that the effects of grass endophytes on seed production and cocksfoot moth seed predation vary considerably among grass species, and the effects may depend on herbivore pressure and other environmental conditions.     

Prevalence of Escherichia coli O157:H7 and Salmonella in beef steers consuming different forage diets

AIMS: To compare the prevalence of faecal shedding of Escherichia coli O157:H7 and Salmonella in growing beef cattle consuming various forages. METHODS AND RESULTS: In Experiment I, faecal samples were collected from steers grazing either endophyte-infected (E+) tall fescue or common bermudagrass (CB). Steers grazing E+ tall fescue were confined to a dry-lot pen and fed CB hay ad libitum for 10 days. In Exp. II, faecal samples were collected from steers grazing either E+ or novel endophyte-infected (NE) tall fescue and treated with one of two anthelmintics: ivermectin (I) or fenbendazole (F). In Exp. I, prevalence of E. coli O157:H7 was less in E+ tall fescue steers fed CB hay than steers grazing CB. More I-treated steers shed Salmonella than F-treated steers at 42-day postanthelmintic treatment but shedding of Salmonella was similar between anthelmintics at day 63 in Exp. II. CONCLUSIONS: Faecal shedding of pathogenic bacteria was not affected by grazing E+ tall fescue. Alterations of forage diets may influence the prevalence of E. coli O157:H7, and anthelmintic treatment could affect faecal shedding of Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of factors that influence shedding of pathogenic bacteria in cattle is necessary to develop on-farm intervention strategies aimed at reducing pathogen shedding.     

Importance of host plant species, Neotyphodium endophyte isolate, and alkaloids on feeding by Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae

Three grass host species--tall fescue, Festuca arundinacea Schreber; meadow fescue, Festuca pratensis Hudson; and perennial ryegrass, Lolium perenne L.--each infected with a number of different Neotyphodium endophyte isolates, were investigated for their effects on fall armyworm, Spodoptera frugiperda (J.E. Smith). Alkaloid profiles varied among associations. Choice and no-choice tests comparing feeding and early development of S. frugiperda larvae on endophyte-infected and endophyte-free leaf blade material were performed. Endophyte-mediated resistance to S. frugiperda was greatest in meadow fescue and weakest in tall fescue. Some endophyte isolates, particularly in perennial ryegrass and meadow fescue, had a major effect on feeding and development of S. frugiperda, whereas others had no effect or were only weakly efficacious. In tall fescue, some associations deterred S. frugiperda from feeding in choice tests but had no effect on development, whereas larvae reared on other associations weighed significantly more than control larvae fed endophyte-free grass. It was concluded that the deleterious consequences of endophyte infection were easily masked by other factors in tall fescue. Relative leaf age had no effect on feeding preferences in the three host species. Chemical analysis of herbage from the plants used, and results from a no-choice study using spiked artificial diets, failed to individually implicate any of the major known alkaloids (peramine, lolitrem B, ergovaline, and lolines) in the observed effects on S. frugiperda. Hypotheses explaining these observations, and their impact on creating desirable grass-endophyte associations for use in pastures, are discussed.     

Systemic relaxin in pregnant pony mares grazed on endophyte-infected fescue: effects of fluphenazine treatment

Tall fescue is one of the most widely grown forage grasses for horses in the United States. However, it is frequently infected with the endophyte Neotyphodium coenophialum which produces ergot alkaloids that cause severe adverse effects in the pregnant mare. The objectives of this study were to determine the effects of fescue toxicosis and fluphenazine on circulating relaxin in pregnant pony mares and evaluate the usefulness of relaxin as a monitor of treatment efficacy. Twelve mares were maintained on endophyte-infected tall fescue pasture. Group TRT (n = 6), received 25 mg of fluphenazine decanoate (i.m.) on Day 320 of gestation while Group UTRT served as untreated controls. Daily blood samples were collected from Day 300 of gestation until Day 3 post partum and analyzed for plasma relaxin concentrations using a homologous equine radioimmunoassay. Mean gestation lengths were 330 +/- 0.7 and 336.5 +/- 3.2 days for TRT and UTRT mares, respectively (P = 0.07). Mean plasma relaxin concentrations in both groups of mares during the week before treatment (Day 313 to 319) were not different (UTRT, 53.4 +/- 11.3 ng/mL; TRT, 61.4 +/- 9.3 ng/mL). In the week after treatment (Day 320 to 326), mean plasma relaxin tended to be higher (P = 0.1) in TRT mares (66.7 +/- 6.2 ng/mL) when compared with UTRT mares (49.6 +/- 6.6 ng/mL), representing a 17.1 ng/mL difference in circulating relaxin between the two groups. Systemic relaxin during the last week before delivery (days relative to parturition) for UTRT and TRT mares was 45.7 +/- 6.7 and 64.7 +/- 6.4 ng/mL (P = 0.06), respectively. At Day -8 and Day -5 relative to parturition, systemic relaxin in TRT mares was significantly higher (P < 0.05) than in UTRT mares. Three of the six UTRT mares and one TRT mare showed clinical symptoms of fescue toxicosis. In the week before delivery, circulating relaxin in mares with problematic pregnancies (39.9 +/- 7.8 ng/mL) was significantly lower than concentrations measured in mares with normal pregnancies (63.4 +/- 5.4 ng/mL; P = 0.03). Clinical observations suggest that a one-time injection with fluphenazine improved pregnancy outcome by reducing the adverse effects of fescue toxicosis concomitant with a stabilization of plasma relaxin concentrations. These data support the hypothesis that systemic relaxin may be a useful biochemical means of monitoring placental function and treatment efficacy in the mare.     

Assessing short-term responses of prokaryotic communities in bulk and rhizosphere soils to tall fescue endophyte infection

In contrast to endophyte-free (E−) tall fescue, endophyte-infected (E+) tall fescue pastures appear to enhance soil carbon sequestration. A hypothetical mechanism that may account for the enhanced carbon sequestration is that the E+ tall fescue affects the soil microbial community or components of it that are involved in organic carbon turnover. A 60-week mesocosm study with a factorial arrangement of soil type, loamy sand (LS) and clay loam (CL), and E+ and E− tall fescue was conducted to determine if the soil microbial communities were affected by the presence of the endophyte. Bulk and rhizosphere soil samples were fixed in paraformaldehyde, and prepared for total direct microbial counts, and with a combination of one of a domain or subdivision fluorescent oligonucleotide probe for enumerating metabolically active Eubacteria, bacterial subdivisions, and Archaea. E+ tall fescue suppressed the archaeal and high G+C gram-positive bacterial communities of the bulk CL, the delta-proteobacterial community in the rhizosphere CL, and the Planctomycetes community of the rhizosphere LS. In the long-term, suppression of these microbial communities may be a factor in enhanced soil carbon sequestration associated with E+ tall fescue.     

Grass species and endophyte effects on survival and development of fall armyworm (Lepidoptera: Noctuidae)

Grass selections including 10 zoysiagrasses, 18 paspalums, 34 Bermuda grasses, tall fescue, creeping red fescue, and perennial ryegrasses with and without endophyte were evaluated for potential resistance to fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae. Laboratory evaluations assessed the degree of antibiosis among >70 grass lines to first-instar fall armvworms. When all parameters measured were considered, the trend in resistance to fall armyworm among endophyte-infected (E+) and endophyte-free (E-) cool season grasses from greatest to least was: 'Dawson' E+ > APR 1234 > 'Dawson' E- > 'Rosalin' E+ > Lp 5425, 'Rosalin' E-, ATF 480 > 'Tulsa' or: E+ slender creeping red fescue > E+ turf- type perennial ryegrass > E- slender creeping red fescue > E+ forage-type perennial ryegrass > E- forage-type perennial ryegrasses, and E+ tall fescue > E- turf-type tall fescue. Among warm season grasses larval weight gain was reduced on all zoysiagrasses. Larval weight gain also was lower on the Bermuda grasses 'Tifsport', 'Tifgreen', 97-4, 97-14, 97-22, 97-28, 97-39, 97-40,97-54, 98-15, 98-30, and 98-45 than when larvae were fed 'Tulsa' tall fescue or the diet control. Only APR1234 and 'Dawson' creeping red fescue reduced larval survival to the same extent that was observed for zoysiagrasses. Survival on Bermuda grasses was least on 97-8. Seashore paspalums were only rarely less susceptible to fall armyworm than tall fescue, although pupal weights were consistently lower on 'Temple 1' and 'Sea Isle 1' paspalums than that on 'Tulsa' tall fescue. Genetic resistance to key grass pests can reduce insecticide use and simplify management of these cultivars.     

Survival of day-4 embryos from young, normal mares and aged, subfertile mares after transfer to normal recipient mares

The estimated embryonic loss rate between Days 4 and 14 after ovulation for young, normal mares (9%) was significantly lower (P less than 0.01) than the estimated embryonic loss rate for aged subfertile mares (62%). Fertilization rates, which were based on the recovery of embryos at Day 4 after ovulation, were 96% and 81% (P less than 0.1) for normal and subfertile mares, respectively. Day-4 embryos were collected from the oviducts of normal and subfertile donors mares. These embryos were transferred to the uteri of synchronized, normal recipient mares to test the hypothesis that the high incidence of embryonic loss in subfertile mares was related to embryonic defects. The hypothesis was supported because embryo survival rates were significantly higher (P less than 0.05) for Day-4 embryos from normal compared to subfertile mares. These defects may have been intrinsic to the embryo or might have arisen due to the influence of the oviducal environment before Day 4 after ovulation.     

Neotyphodium Coenophialum-Infected Tall Fescue and Its Potential Application in the Phytoremediation of Saline Soils

The growth response of endophyte-infected (EI) and endophyte-free (EF) tall fescue to salt stress was investigated under two growing systems (hydroponic and soil in pots). The hydroponic experiment showed that endophyte infection significantly increased tiller and leaf number, which led to an increase in the total biomass of the host grass. Endophyte infection enhanced Na accumulation in the host grass and improved Na transport from the roots to the shoots. With a 15 g l^?1 NaCl treatment, the phytoextraction efficiency of EI tall fescue was 2.34-fold higher than EF plants. When the plants were grown in saline soils, endophyte infection also significantly increased tiller number, shoot height and the total biomass of the host grass. Although EI tall fescue cannot accumulate Na to a level high enough for it to be termed a halophyte, the increased biomass production and stress tolerance suggested that endophyte / plant associations had the potential to be a model for endophyte-assisted phytoextraction in saline soils.