Wild-type Endophyte Research Articles

161 Effects of Sericea Lespedeza Supplementation on Steers Grazing Wild-Type Endophyte-Infected Tall Fescue

Abstract Fescue toxicosis poses a significant challenge to the United States beef industry, resulting in considerable economic losses. This syndrome arises from the consumption of tall fescue (Schedonorus arundinaceous) infected with the wild-type endophyte (WE; Epichloe coenophiala), which produces toxic alkaloids. The most effective solution for mitigating fescue toxicosis is renovating WE tall fescue pastures to novel endophyte-infected (NE) tall fescue. However, pasture renovation is costly and may not be feasible under certain conditions, with the economic profitability taking up to 3 yr. While the potential of condensed tannins (CTs) in specific leguminous forages to reduce the absorption of toxic alkaloids is recognized, their use as supplements remains underexplored. This study aims were to investigate the potential of CT-containing feed supplements, specifically sericea lespedeza (Lespedeza cuneata) pellets, in reducing the post-ingestive effects of fescue toxicosis in steers. Over two summers,12 steers were assigned to either Schedonorus arundinaceous (LES) or LES mixed with polyethylene glycol (LES + PEG) as a positive control for 12 wk. Body weight, hair retention score, rectal and extremities temperatures, cortisol concentrations, and lumen area of caudal arteries were collected at 4-wk intervals. Data were analyzed using a mixed-effect ANOVA test in SAS Studio 3.5. Steers on the LES diet exhibited significantly less (P < 0.05) hair retention scores compared with those on the LES + PEG diet. In 2021, steers on the LES diet showed greater (P = 0.0101) ADG, while in 2022, there was no difference (P = 0.9916) in ADG between the treatments. Steers on the LES diet displayed greater (P = 0.0332) tail skin temperatures and decreased (P < 0.0001) rectal temperatures compared with those on the LES + PEG diet. Hair cortisol concentrations were greater (P < 0.05) in steers on the LES + PEG diet than in those on the LES diet. Additionally, steers supplemented with the LES + PEG diet showed a 21.2% smaller caudal artery lumen area compared with those on the LES diet (P < 0.01). These findings underscore the potential of CTs in reducing the post-ingestive effects of fescue toxicosis. However, further research is needed to explore the complex mechanisms underlying these effects, establish the long-term efficacy of such interventions, and extend the investigation to include a broader range of physiological parameters affecting livestock health and performance.

Non-Invasive Techniques Reveal Heifer Response to Fescue Endophyte Type in Grazing Studies.

Cattle grazing tall fescue (Schedonorus arundinaceous) infected with wild-type endophytes (WE) leads to a syndrome commonly known as fescue toxicosis. Replacing WE tall fescue with a novel endophyte-infected (NE) tall fescue can mitigate this problem but adoption of this technology has been limited. This study measured and determined the physiological and behavioral responses of heifers that grazed either WE or NE tall fescue, utilizing relatively non-invasive techniques including hair cortisol, thermography (for extremity temperatures), small loggers for intravaginal temperature, and remote observation of in-field behavior. Heifers that grazed WE had greater (p < 0.0001) hair cortisol levels, lower extremity temperatures (p ≤ 0.0075), and 0.3-0.9 °C greater (p ≤ 0.02) intravaginal temperatures (particularly during the daytime) than heifers that grazed NE. From 1200 h-1700 h each day, heifers on WE pastures spent 1.5 more (p = 0.0003) hours standing up and 0.9 fewer (p = 0.0402) hours lying down than heifers on NE pastures. Differences (p = 0.0160) in ADG were small (0.1 kg d-1) and were only observed in the first year of these 8-week studies. However, even in the mild environment of the study site, grazing NE tall fescue provided clear welfare benefits as evidenced by heifer behavioral changes, temperature differentials, and hair cortisol levels. This study underscores the potential utility of non-invasive techniques, such as thermographic imaging and hair cortisol analysis, for evaluating animal responses to stress in extensive grazing systems.

Condensed Tannins Attributes: Potential Solution to Fescue Toxicosis?

Tall fescue (Schedonorus arundinaceous (Schreb.) Dumort. nom. cons. Lolium arundinaceum (Schreb.) Darbysh.) toxicosis results from the consumption of alkaloids released by wild-type endophytes (Epichloe coenophiala) that live in symbiosis with the plant. Alkaloid consumption causes significant production and reproductive losses which cost the U.S. beef industry approximately $2 billion every year. Incorporating species that contain condensed tannins (CTs) into forage systems may be an effective strategy to reduce the effects of fescue toxicosis in livestock. It has been hypothesized that stable complexes formed between CTs and toxic alkaloids could help reduce their absorption through the gastrointestinal epithelia, thus reducing their toxic effects. However, it is not yet clear whether CTs are effective in reducing the effects of fescue toxicosis in grazing systems. A comprehensive literature search was carried out using Google Scholar to identify studies relevant to the research question, from which the cited articles were selected. This review covers the value and issues of tall fescue employed as useful forage, summarizes the impact endophyte-infected tall fescue can have on cattle, and sets out the current management strategies implemented to minimize fescue toxicosis. The review continues with a brief summary of tannin structure and the well-documented benefits that CT-containing forages can contribute to the productivity and sustainability of ruminant agriculture. Finally, a summary of the potential forage sources, mechanisms, and benefits of CTs in reducing the negative post-ingestion effects of fescue alkaloids in livestock is provided.

Can endophyte-infected tall fescue minimize the grass tetany risk?

Non-toxic Neotyphodium (novel endophyte) has been shown to provide similar agronomic performance as wild-type endophyte to deter pathogens without exerting adverse effects on livestock. While the grass/novel endophyte interaction does not synthesize alkaloid peramine that has been linked to mammal toxicity, the connection between wild (naturally occurring) and/or novel endophyte infection and tetany ratio in forage has not been evaluated. The risk of grass tetany was evaluated in naturally occurring endophyte-infected tall fescue grass grown in Japanese Andisol. Three tall fescue (Festuca arundinacea Schreb.) ecotypes (Fukaura, Koiwai and Showa) either infected with Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin (E+), or noninfected (E-) were grown in low phosphorus (P) availability black Andisol and high P availability red Andisol under a controlled environment. The biomass nutrient concentration was measured and the tetany ratio, K/(Ca+Mg), was established for all three fescue ecotypes. &#x0D; Results showed that K, Ca, and Mg concentrations and the K/(Ca+Mg) were significantly affected by endophytes, soils, and ecotypes and their interactions. Regardless of ecotypes and soils, K, Ca, and Mg concentrations were higher in endophyte-infected plants when compared to the control. Among the endophyte-infected ecotypes, the Fukaura and Koiwai showed higher K, Ca, and Mg concentrations in red Andisol. In contrast, the Showa ecotype showed higher K, Ca, and Mg concentrations in endophyte-infected plants than the control in black Andisol. Notwithstanding ecotypes and soils, endophyte-infected plants showed lower K/(Ca+Mg) than their counterparts, suggesting that the grass/endophyte interaction could provide a means of reducing the incidence of grass tetany in livestock.

Endophytes matter: Variation of dung beetle performance across different endophyte-infected tall fescue cultivars

Traditional tall fescue cultivar, Kentucky 31, possesses a wild-type endophyte strain that produces several bioactive compounds including the ergot alkaloid, ergovaline, known to cause cattle toxicity and effects on insects. Novel cultivars, BarOptima PLUS E34, Jesup MaxQ, and Texoma MaxQ II, possess different endophyte strains that do not have negative effects on cattle but still protect from insect grazing. Our study investigated if different cultivars have different effects on insect dung decomposers such as dung beetles and determined if ergovaline could be detected in cow dung. Ergovaline at 0.04 and 0.27 μg/g was detected only from Kentucky 31 dung samples from 2017 and 2018 collections, respectively. From the 2017 dung collection, we tested Onthophagus taurus oviposition substrate preferences for each cultivar versus dung from uninfected pasture and also larval survival and development for each dung-type. From the 2018 dung collection, O. taurus and Digitonthophagus gazella oviposition substrate preferences, larval survival and development were tested for Texoma MaxQ II versus Kentucky 31 dung-types. Among the four cultivars, for making brood-balls O. taurus preferred dung from Texoma MaxQ II while dung from Kentucky 31 and BarOptima PLUS E34 were avoided. Both beetle species preferred dung from Texoma MaxQ II versus Kentucky 31 pasture. Larval survival was not affected by dung-type with the 2017 samples. However, with the 2018 samples both beetle species had reduced larval survival on Kentucky 31 than on Texoma MaxQ II brood-balls. Development time for O. taurus was shorter for larvae from Texoma MaxQ II versus Kentucky 31 or uninfected dung brood-balls. Adult mass was not affected in the 2017 collection but was reduced in 2018 Kentucky 31 samples when compared with Texoma MaxQ II. Finally, dung beetles can differentiate dung from pastures with different tall fescue cultivars. Novel cultivar, Texoma MaxQ II, provides more benefits for dung beetles. Pasture renovations with Texoma MaxQ II may improve pasture ecology by enhancing dung beetle populations.

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+.

A comparison of spring- and fall-calving beef herds grazing tall fescue

Nineteen years of beef cow herd records were obtained from the Research and Education Center at Ames Plantation, near Grand Junction, Tennessee. The cow herds were under the same management, and all cows were strictly culled for reproductive failure, age, and low performance of their calves. The cows primarily grazed tall fescue (Lolium arundinaceum Schreb.) with the wild-type endophyte (Neotyphodium coenophialum) that is known to cause the symptoms of tall fescue toxicosis. For 19 yr the total number of cows and calves were 478 and 1,534 for the spring-calving herds and 474 and 1,727 for the fall-calving herds, respectively. Phenotypic parameters were days to first calf, calving interval, number of calves born, birth BW, weaning weight (WW), adjusted 205-d WW, ADG from birth to weaning, and weight/day of age. The data were analyzed from a historical standpoint using herd as a fixed effect and years as replicates. Heifers in the spring-calving herd averaged 27 d older (P < 0.0001) at calving than the fall-calving heifers. The spring-calving herd had a shorter calving interval (P < 0.05) and produced fewer calves per cow (P < 0.05). Although calves born in the spring and fall herd had similar birth BW (P = 0.751), the calves born in the spring had a higher ADG and higher 205-d WW than did those born in the fall. Even though the spring-born calves gained faster and had higher 205-d WW, the fall-calving herd increased the income of the farm because of greater number of calves and reduced need for replacement heifers.

Comparison of wild type, AR1 and AR37 endophyte infected perennial ryegrass on in vitro methanogenesis

Perennial ryegrass (Lolium perenne) is a major pasture species grazed by cattle and sheep in the temperate regions of Australia. The principal aim our study was to examine effects of ryegrass endophytic fungi on in vitro ruminal methanogenesis. Samples of perennial ryegrass pasture infected with either wild-type endophyte or the novel endophytes, AR1 or AR37, were seasonally collected, over 3years. Samples were collected during spring, a period which usually coincides with low alkaloid concentrations, and in late summer–autumn, a period in which alkaloid concentrations generally peak. The pasture samples were freeze–dried, ground and measured for concentrations of lolitrem B, ergovaline, peramine and total epoxy janthitrems. Samples of freeze–dried ground pasture were incubated in triplicate for 48h in vitro in cow rumen fluid. Gas production was measured at 9, 24 and 48h post inoculation, the same time at which gas headspace was sampled for CH4 concentration. Culture pH and in vitro dry matter disappearance were measured at 48h. In ryegrass with wild-type endophyte, mean (±SD) concentrations (mg/kg DM) of lolitrem B were 0.02±0.041 in spring and 1.2±0.89 in summer–autumn while, for ergovaline, the respective concentrations were 0.1±0.04 and 0.5±0.26 and for peramine 6.8±2.27 and 12.5±2.78. For ryegrass infected with AR1, concentrations of peramine were 6.7±2.17 in spring and 12.7±2.97 in summer–autumn. For ryegrass infected with AR37, concentrations of total epoxy-janthitrems were 0.05±0.060 in spring and 10.8±5.89 in summer–autumn. Lolitrem B and ergovaline were not detected in samples of ryegrass infected with AR1 or AR37 endophytes. Peramine was not detected in ryegrass infected with AR37 endophyte and epoxy-janthitrems were not detected in ryegrass infected with wild-type or AR1 endophytes. Neither endophytic strain nor concentration of alkaloid had any effect on CH4 production expressed as ml/g DM. However, CH4 production expressed as ml/g digested DM was lower from samples collected in spring than from samples collected in summer-autumn (P=0.001). Endophyte strain and sampling period had minor effects on other indices of rumen fermentation. Compared to ryegrass infected with wild type endophyte, the novel endophyte strains AR1 and AR37 do not inhibit CH4 production in vitro, and are unlikely to have any useful role in CH4 abatement strategies.

Bacillus subtilis and Enterobacter cloacae endophytes from healthy Theobroma cacao L. trees can systemically colonize seedlings and promote growth

Clonal genotypes resistant to fungal diseases are an important component of the cocoa production system in southeastern Bahia state (Brazil), so that technologies for faster production of stronger and healthier plantlets are highly desirable. In this study, the effects of inoculated bacterial endophytes isolated from healthy adult cacao plants on seedlings, and aspects related to inoculation methods, colonization patterns, and photosynthesis were investigated. Sequencing of 16S rRNA, hsp-60, and rpo-B genes placed the wild-type isolates within the species Enterobacter cloacae (isolates 341 and 344) and Bacillus subtilis (isolate 629). Spontaneous rifampicin-resistant (rif(R)) variants for 344 were also produced and tested. Endophytic application was either by immersion of surface sterilized seeds in bacterial suspensions or direct inoculation into soil, 20days after planting non-inoculated seeds into pots. Results from in vitro recovery of inoculated isolates showed that the wild-type endophytes and rif(R) variants systemically colonized the entire cacao seedlings in 15-20days, regardless of the inoculation method. Some endophytic treatments showed significant increases in seedlings' height, number of leaves, and dry matter. Inoculation methods affected the combined application of endophytes, which maintained the growth-promotion effects, but not in the same manner as in single applications. Interestingly, the 344-3.2 rif(R) variant showed improved performance in relation to both the wild type and another related variant. Photosynthetic rates and stomatal conductance increased significantly for some endophytic treatments, being partially associated with effects on growth and affected by the inoculation method. The results suggest that E. cloacae and B. subtilis endophytes from healthy adult plants (not transmitted by seeds) were able to promote vegetative growth on cacao seedlings. The development of products for large-scale use in seedlings/plantlets production systems was discussed.

The evaluation of fungal endophyte toxin residues in milk

AIM: To determine the concentrations of fungal endophyte toxins in the milk of cows fed perennial ryegrass containing wild-type or AR37 endophyte. METHODS: Groups of 10 multiparous Holstein-Friesian cows were fed wild-type (containing lolitrem B) or AR37 (containing epoxy-janthitrems) endophyte-infected perennial ryegrass (Lolium perenneL.). Animals were kept indoors and fed for 12 days. Over this period, animals were regularly assessed for ryegrass staggers and herbage intake measured. At the conclusion of the 12-day indoor-feeding period, cows were grazed on AR1 (toxin-free) pastures for a further 8 days. Daily individual milk samples and milk yields were collected over the complete 20-day period. Milk samples were analysed for endophyte toxins using HPLC methods developed during this study. Daily herbage samples were also taken and concentrations of endophyte toxins measured. RESULTS: Methods were successfully developed for the analysis of lolitrem B and epoxy-janthitrems in milk which allowed the concentrations of these compounds in milk to be compared with the concentrations in feed consumed by the animals. Both toxin types could be detected in milk after only 1 day of exposure to respective treatment pastures. The maximum concentration of endophyte toxins in milk was 5 ng/mL lolitrem B and 109 ng/mL epoxy-janthitrems from cows fed wild-type and AR37 endophyte-infected ryegrass pastures, respectively. Concentrations of epoxy-janthitrems present in herbage were much higher than for lolitrem B (Day 1–12 average of 14.6 and 1.8 ppm, respectively). Despite the high concentrations of epoxy-janthitrems consumed by cows fed AR37 endophyte-infected pastures no signs of ryegrass staggers were observed over the experimental period, whereas those cows fed wild-type endophyte-infected pastures all showed signs of ryegrass staggers. This is consistent with the view that epoxy-janthitrems are low potency tremorgens. At the conclusion of the toxin feeding period, endophyte toxin concentrations in milk quickly dropped to almost zero after 8 days. A comparison of the quantities of lolitrem B and epoxy-janthitrems consumed by each cow with the quantities secreted in milk showed that only very low proportions of the total amount ingested are secreted in milk (0.23% lolitrem B and 0.49% epoxy-janthitrems). CONCLUSION: Lolitrem B and epoxy-janthitrems can be detected in the milk of cows consuming wild-type and AR37 endophyte-infected perennial ryegrass, respectively. Concentrations detected were low and changed quickly in association with the amounts being consumed by the cows. Available evidence gives no indication that these compounds may pose a threat to human health.

Effects of novel and wild-type endophytes in perennial ryegrass on cow health and production

AIM: To measure the effects of AR37, AR1 and Wild-type endophytes in perennial ryegrass on cow health and milk production. METHODS: Four indoor and six grazing experiments were used to evaluate a perennial ryegrass cultivar containing either novel (AR37, AR1) or Wild-type (HE or Standard) endophytes or no endophyte (Nil). Three hectares of each ryegrass/endophyte association were sown with a white clover cultivar in April 2005 and either grazed or cut for indoor feeding from July 2005 to March 2009. The novel endophytes were distinguished by the production of epoxy-janthitrems by AR37 and peramine only by AR1, both of which deter insect attack. This is the first assessment of the effects of AR37 endophyte on dairy cow health and production. In all experiments, cows were monitored for indications of ryegrass staggers (RGS) by visual scoring, respiration rate as an indicator of heat stress and, in some instances, packed cell volume (blood haematocrit), blood serum albumin concentrations and skin elasticity as indicators of dehydration. Milk production and composition were measured routinely. Pasture production, composition and alkaloid content were determined, as well as temperature and humidity in the indoor feeding facility. Indoor experiments enabled accurate measurement of dry matter intakes, as well as water consumption in some instances. RESULTS: Cows eating AR37 or AR1 ryegrass did not develop RGS. During indoor feeding experiments in summer and autumn, cows eating ryegrass infected with Wild-type (Wild-type ryegrass) always developed RGS, while under rotational grazing, onset of RGS was less predictable and rarely affected all animals in the group. Severity of RGS was related to the concentration of lolitrem B in ryegrass. No cows demonstrated signs of extreme heat stress in any situation. During summer indoor feeding, cows eating ryegrass infected with AR1 endophyte (AR1 ryegrass) sometimes produced more milk and milksolids (MS) compared to ryegrass infected with AR37 (AR37 ryegrass). The dry matter intakes of cows fed AR37 ryegrass were sometimes higher than those fed AR1, and intakes were lowest when Wild-type ryegrass was fed. Water intakes of cows fed Wild-type ryegrass indoors were lower than those of cows fed AR1 or AR37 ryegrass in two of the three summer indoor experiments. The cows fed AR1 ryegrass indoors always produced more MS than cows fed Wild-type ryegrass. Under grazing, the same trends were detected, but production over three full lactations was similar for AR1 and AR37 ryegrass. CONCLUSIONS AND CLINICAL RELEVANCE: The absence of animal health and management problems, especially RGS, makes the novel endophytes AR37 and AR1 attractive alternatives to Wild-type ryegrass. Total MS production over three consecutive lactations was not affected by endophyte treatment. The choice of novel endophyte for pasture renewal will depend on local insect pest populations.

Effects of wild-type, AR1 and AR37 endophyte-infected perennial ryegrass on dairy production in Victoria, Australia

A 3-year experiment compared the effects of wild-type ryegrass endophyte and two novel endophytes on milk production in dairy cattle. On three 9.9-ha farmlets in West Gippsland, Victoria, pasture swards were established that were dominant in perennial ryegrass (Lolium perenne) infected with either wild-type, AR1 or AR37 endophytes. Each farmlet was stocked with 25 spring-calving Holstein–Friesian cows, which rotationally grazed nine paddocks within their farmlet during three lactations over 3 years. The three endophytes are known to produce different alkaloids, with wild-type producing ergot alkaloids, lolitrems and peramine, AR1 producing peramine and AR37 producing epoxy-janthitrems. These alkaloids were present in fresh pasture as well as hay and silage made from that pasture. Grazed pasture comprised 53% of estimated annual DM intake. The proportion was least from December to March when the daily ration of 2 kg DM/cow.day cereal grain was increased to 6 kg/day and forage supplements were fed consisting of purchased lucerne (Medicago sativa) hay and pasture silage grown on the farmlets. There were no differences in pasture accumulation rates or nutritive characteristics of ryegrass pastures on the three farmlets and no differences in the production of milk, fat or protein by cows grazing pasture infected with the three endophytes. Ryegrass staggers was only observed in four cows consuming the wild-type-infected ryegrass in the first year when the highest concentrations of lolitrem B were recorded in pasture. Soil samples showed lower numbers of root aphids (Aploneura lentisci), mealybugs (Pseudococcidae) and pasture tunnel moths (Philobota spp.) beneath ryegrass infected with the AR37 endophyte compared with the other two endophytes. Numbers of redheaded (Adoryphorus couloni) and blackheaded (Aphodius tasmaniae) cockchafers did not differ between treatments. Under dairy management and supplementary feeding regimes common to south-eastern Australia, the novel endophytes AR1 and AR37 had no effect on the milk production compared with the wild-type endophyte, and did not cause ryegrass staggers.

Effect of the wild-type tall fescue endophyte on growth rate and feed consumption in nulliparous meat goat does

Tall fescue is one of the primary pasture forages used to manage goats in the United States. Data are limited on how the wild-type endophyte (Neotyphodium coenophialum) found in most tall fescue stands affects meat goat performance. In two experiments across four summers, nulliparous yearling does were fed diets containing tall fescue seed to assess the effect of endophyte infection on goat growth and feed intake. In Experiment 1, does were fed endophyte-infected or endophyte-free tall fescue seeds added to the diets for 10 weeks. Feed refusals were weighed daily. The endophyte-infected diet reduced (P<0.05) weight gain and increased (P<0.05) feed refusals. In Experiment 2, feed refusal values of endophyte-infected pens were used to adjust feed offering to endophyte-free pens daily. When daily feed intake was equalized for endophyte-infected and endophyte-free pens, doe weight gain was still reduced by the endophyte-infected diet over 10 weeks. These data suggest that endophyte infection in tall fescue can adversely affect meat goat growth rates in a manner not totally dependent on nutrient intake levels.

Haemodynamics of lambs grazing perennial ryegrass (Lolium perenne L.) either infected with AR6 novel, wild-type endophyte, or endophyte-free

AIM: To compare vasoconstriction of the auricular artery and characteristics of blood flow in the carotid arteries between lambs grazing perennial ryegrass that was either infected with the AR6 novel endophyte (AR6), wild-type endophyte or endophyte-free. METHODS: Sixteen Coopworth lambs, mean 23.7 (SD 1.8) kg, were randomly assigned to graze three, 0.10-ha pastures of perennial ryegrass (cultivar Extreme) located in Lincoln, New Zealand, that were infected with either the AR6 novel endophyte (n=5) or wild-type endophyte (n=6) or were endophyte-free (n=5), for 18 days until 16 March 2009. Lambs on AR6 pasture were then switched to endophyte-free pasture, and those on endophyte-free were switched to AR6 pasture, for 18 days. Lambs continued grazing the wild-type ryegrass during both phases of the study. Colour Doppler ultrasonography was used to monitor cross-sectional area of lumina in the auricular and carotid arteries as measurements of vasoconstriction, and to measure pulsatility indices, heart rate, systolic and diastolic velocities, and mean velocity in the carotid artery. Urine was sampled once during each phase, to measure the concentration of urinary alkaloids. A heat challenge (32°C) was imposed on the last day of the experiment, to determine treatment effects on rectal temperature and respiration rate. RESULTS: Vasoconstriction was detected in the auricular arteries of lambs grazing AR6 and wild-type pastures. Areas of lumina declined linearly over 9 days in lambs that were switched from endophyte-free to AR6 pastures (p<0.05), and areas increased linearly in lambs that were switched from AR6 to endophyte-free pasture (p<0.001). Resistance to blood flow in the carotid arteries decreased linearly in the 9 days after lambs were switched from AR6 to endophyte-free pasture(p<0.05), and tended to increase after lambs on endophyte-free pasture were switched to AR6 (p<0.10). The concentrations of urinary alkaloids decreased after switching lambs from AR6 to endophyte-free pasture, and increased after switching from endophyte-free to AR6 pasture (p<0.05). The concentrations of urinary alkaloids of lambs on wild-type pasture were similar between the conditioning and experimental phases. There were no treatment effects on rectal temperature and respiration rate during the heat challenge. CONCLUSIONS: These results indicated that management approaches are needed to overcome potential vulnerabilities to heat stress for sheep grazing AR6 perennial ryegrass. Furthermore, following grazing such pasture, lambs will need to graze endophyte-free ryegrass for >18 days, to completely clear ergot alkaloids from their vasculature, assuming that complete clearance can be achieved.

Fluctuations in the concentration of ergovaline and lolitrem B produced by the wild-type endophyte (Neotyphodium lolii) in perennial ryegrass (Lolium perenne) pasture

Mammalian toxins produced by the wild-type endophyte, Neotyphodium lolii, in perennial ryegrass (PRG) pasture cause production losses and animal health and welfare problems in livestock. Managing this risk is limited by the lack of information on fluctuations in the concentration of toxin in Australian pasture. We investigated how the toxin concentrations may be related to recent observations of weather. Swards sown from common seedlots of two cultivars of wild endophyte-infected PRG, grazed short by sheep, were sampled at 2–4 weekly intervals from spring to autumn at two sites in Victoria. The highest concentration of ergovaline and lolitrem B was observed at Hamilton, the site with the longer-growing season. The concentration of ergovaline peaked in early summer, coinciding with seed development, and declined through summer, before increasing with the commencement of autumn growth. The concentration of lolitrem B remained low in summer, then rose in autumn. Variation between the two cultivars in the concentration of toxins was small and rarely significant. The concentration of ergovaline declined as the mean daily maximum temperature over the preceding 1–5 days increased. Similarly, for lolitrem B, the concentration declined over the temperature range 12−20°C, from 1.3 to 0.3 mg/kg. At Hamilton, where solar radiation and soil temperature were recorded, both were superior to maximum temperature for predicting lolitrem B. Serial sampling of PRG from old naturalised pasture on seven farms across south-eastern Australia found two seasonal peaks for both alkaloids in most pastures. The concentration of ergovaline reached or exceeded tolerance levels for livestock in 23 of 43 samples, compared with 5 of 43 for lolitrem B. Ergovaline concentrations initially peaked (at 1.0–1.6 mg/kg) when mature reproductive material was present (coinciding with peduncle elongation and seed development). In pastures with low grazing pressure, i.e. where growth was allowed to continue through summer, ergovaline concentration was relatively low (&lt;0.7 mg/kg) but in a hard-grazed pasture (sward height 3 cm), the ergovaline concentration was greater (up to 1.1 mg/kg). Concentration of lolitrem B also peaked in December, except on pasture where growth continued through summer. High concentrations of lolitrem B associated with neurotoxic signs in sheep (viz. 2.4–3.9 mg/kg) were observed only in mid-summer and autumn, and only if conditions favoured growth or where close grazing by sheep left the crown as the dominant source of herbage.

Tall Fescue Copper and Copper-Zinc Superoxide Dismutase Status in Beef Steers Grazing Three Different Fescue Types

Copper status of steers (n = 24; 258 kg initial BW) grazing tall fescue (Festuca arundinacea Shreb.) pastures was measured for 2 consecutive grazing seasons. The forages tested included ‘Kentucky-31’ wild-type endophyte (Neotyphodium coenophialum)-infected tall fescue and endophyte-free tall fescue, and ‘Quantum’ tall fescue infected with endophyte AR542, a non-ergot alkaloid-producing strain. Forage Cu concentration was similar (P = 0.20) across treatments and averaged 4.4 mg/kg. Steers consumed less (P 0. 22). In yr 1, liver Cu concentrations of cattle grazing endophyte-free tall fescue were greater (P 0.33) among treatments in either year. These results suggest that the tendency for less Cu intake of steers grazing endophyte-infected tall fescue and ‘Quantum-AR542’ (P ≤ 0.10) was related to the smaller DMI on these pastures. The smaller Cu intakes likely contributed to differences in liver Cu. Endophyte status of forage did not affect Cu-Zn SOD enzymatic activity or relative mRNA abundance.

An investigation of non-target impacts of ryegrass endophytes on nematodes and soil microorganisms

A pot trial with two sampling times was conducted to compare the non-target effects of Nil endophyte ryegrass with three endophyte/ryegrass combinations, two selected endophytes (AR1 and AR37) and a wild-type, in the same cultivar. Shoot dry weight, soil nematode and microbial abundance and community diversity were assessed at each sample time. Plants infected with wildtype endophyte produced significantly less shoot weight than all other treatments due to slow initial growth. Keywords: Neotyphodium, Denaturing Gradient Gel Electrophoresis, Enrichment Index, Structure Index, Nematode Channel Ratio

Testing for Variation in Animal Preference for Jesup Tall Fescue Hays with Wild‐Type, Novel, or No Fungal Endophyte

Tall fescue [Schedonorus phoenix (Scop.) Holub.] is an important source of forage but often contains a fungal endophyte [Neotyphodium coenophialum (Morgan‐Jones and Gams) Glenn, Bacon, and Hanlin] that can produce alkaloids and decrease animal performance. Removing the endophyte can reduce agronomic performance and persistence. An improved cultivar (‘Jesup’) with a novel (nontoxic) endophyte (trademark “MaxQ”) has improved agronomic performance. Persistence may be related to agronomic traits and animal feeding preferences. We tested for variation in animal preference among two harvests by testing each of three hays made from Jesup tall fescue that varied in endophyte status (no endophyte, containing the novel endophyte, or containing a wild‐type endophyte that produces alkaloids associated with toxicosis). We tested for preference using goats (Capra hircus), sheep (Ovis aries), and cattle (Bos taurus). All possible pairs were tested using traditional analysis of variance as well as multidimensional scaling. Multidimensional scaling of the animal preferences indicated that two dimensions were being used to rank the hays. The first dimension for all three animal species was related to variation in forage nutritive value. The second dimension was not correlated with any of the measured variables. Endophyte status was not a factor in the preferences expressed by the three animal species. It appears that no effective feedback mechanism exists related to endophyte status.

Effects of Fescue Type and Sampling Date on the Nitrogen Disappearance Kinetics of Autumn-Stockpiled Tall Fescue ,

Two tall fescue [Lolium arundinaceum (Schreb.) Darbysh] forages, one an experimental host plant/endophyte association containing a novel endophyte that produces low or nil concentrations of ergot alkaloids (HM4) and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56kg/ha of N to assess N partitioning and ruminal disappearance kinetics of N for these autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361±56.4-kg replacement dairy heifers were stratified by weight and breeding, and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh pasture strip (December 26, January 15, and February 4), and when the study was terminated (February 26). Generally, fescue type and the fescue type×sampling date interaction exhibited only minor effects on total forage N, or partitioning of N within the cell solubles or the cell wall. For pregrazed forages, concentrations of N and N partitioned within the cell solubles both declined in a strongly linear relationship with sampling dates. In contrast, concentrations of cell-wall–associated N changed in erratic and often higher-ordered relationships with time, but the magnitude of these responses generally was limited. Unlike the partitioning of N within cell-wall and cell-soluble fractions, kinetic characteristics of ruminal N disappearance frequently exhibited interactions of fescue type and sampling date. For pregrazed forages, these included interactions for all response variables, and for postgrazed forages, fractions B and C, as well as rumen degradable protein. Ruminal disappearance rate for pregrazed E+ and HM4 exhibited quadratic (range=0.057 to 0.082/h) and cubic (range=0.057 to 0.075/h) relationships with time, respectively. For postgrazed E+ and HM4 forages, ruminal disappearance rate was unaffected (mean=0.066/h) or only tended to be affected by sampling date (mean=0.065/h), respectively. Concentrations of rumen degradable protein exhibited various curvilinear relationships with sampling dates, but disappearance was consistently extensive, and the overall range was relatively narrow (71.3 to 78.9% of N). These findings suggest that ruminal disappearance of N for autumn-stockpiled tall fescue forages remains extensive throughout the winter months and is only affected minimally by fescue type, sampling date, and grazing status.

Effects of Fescue Type and Sampling Date on the Ruminal Disappearance Kinetics of Autumn-Stockpiled Tall Fescue

Two tall fescue (Festuca arundinacea Schreb.) forages, one an experimental host plant/endophyte association containing a novel endophyte (HM4) that produces low or nil concentrations of ergot alkaloids, and the other a typical association of Kentucky 31 tall fescue and the wild-type endophyte (Neotyphodium coenophialum; E+), were autumn-stockpiled following late-summer clipping and fertilization with 56kg/ha of N to assess the nutritive value and ruminal disappearance kinetics of autumn-stockpiled tall fescue forages. Beginning on December 4, 2003, sixteen 361±56.4-kg replacement dairy heifers were stratified by weight and breeding and assigned to one of four 1.6-ha pastures (2 each of E+ and HM4) that were strip-grazed throughout the winter. Pastures were sampled before grazing was initiated (December 4), each time heifers were allowed access to a fresh strip (December 26, January 15, and February 4), and when the study was terminated (February 26). For fiber components, there were no interactions between fescue type and sampling date for either pregrazed or postgrazed forages. Over sampling dates, neutral detergent fiber (NDF; 56.5 to 67.8%), acid detergent fiber (27.7 to 34.9%), hemicellulose (28.8 to 34.0%), cellulose (25.0 to 28.1%), and lignin (3.61 to 10.05%) varied with sampling date, but patterns were almost exclusively curvilinear with time. Ruminal disappearance rate of dry matter (DM) was not affected by any treatment factor (overall mean for both pregrazed and postgrazed forages = 0.050h−1); similar responses were observed for NDF disappearance (overall mean = 0.048h−1). Interactions of fescue type and sampling date were observed for both pregrazed and postgrazed forages with respect to effective ruminal disappearance of DM; however, estimates were relatively high for all forages (overall mean = 64.0%). Effective disappearance of NDF was relatively extensive for all forages (overall mean = 55.4% of NDF). Based on the results of this trial, the endophyte status of stockpiled tall fescue forages had little practical effect on forage nutritive value and kinetics of ruminal DM or NDF disappearance. Overall, autumn-stockpiled tall fescue forages would appear to be a legitimate and lower cost alternative to harvested forages, and appear to possess suitable nutritional characteristics for developing dairy heifers in the Ozark Highlands.