Ryegrass Staggers Research Articles

Potential of Accelerometers and GPS Tracking to Remotely Detect Perennial Ryegrass Staggers in Sheep

Perennial ryegrass staggers (staggers) is a neurotoxic condition in livestock that is caused by consumption of ryegrass (Lolium perenne) infected with specific strains of Epichloë fungal endophytes. These grass-endophyte associations produce toxins that can adversely affect animals and can in some cases lead to death. In sheep, symptoms typically include head shaking, changes in gait, stiffness and falling. Affected sheep can recover after removing them from pastures containing toxic strains of endophyte. A pilot case study was conducted in Lincoln, New Zealand to determine if ryegrass staggers could be identified with data collected through GPS tracking and accelerometers. Fourteen sheep per treatment grazed in either a toxic endophyte-infected ryegrass paddock or an endophyte-free control paddock for 17 days in late March and early April 2017. Randomly selected sheep were fitted with collars containing a 3-axis accelerometer recording movements at 12 Hz (10 collars in endophyte infected paddock and 6 in the control paddock). Three sheep per treatment were also tracked at 3-minute intervals with GPS receivers. Sheep were scored by an experienced observer for symptoms of staggers weekly and at the end of the study using a 0 to 5 scale. Control sheep did not display any symptoms of staggers and 10 sheep in the infected pasture displayed little or no symptoms (0 or 1 score). The other 4 sheep in infected pasture had scores from 2 to 4 at the end of the study. Sheep grazing in the infected pasture (2.91 m/min ± 0.04 SE) moved slower (P=0.04) than sheep in the control pasture (3.12 m/min ± 0.05 SE). Distance travelled varied among days, but there did not appear to be any temporal trends. Machine learning analyses of accelerometer data showed that the behavior of affected sheep changed during the study. Activity of sheep displaying symptoms (scores ≥ 2) increased more in the morning and midday during the latter part of the study than control sheep and sheep with few or no symptoms (score < 2). However, behavior of individual sheep at night remained relatively consistent during the study. Accelerometers may be useful for remotely detecting perennial ryegrass staggers.

Potential of Accelerometers and Gps Tracking to Remotely Detect Perennial Ryegrass Staggers in Sheep

Potential of Accelerometers and Gps Tracking to Remotely Detect Perennial Ryegrass Staggers in Sheep

Development and validation of an ultrahigh performance liquid chromatography-high resolution tandem mass spectrometry assay for nine toxic alkaloids from endophyte-infected pasture grasses in horse serum

Endophyte fungi (e.g. Epichloë ssp. and Neotyphodium ssp.) in symbiosis with pasture grasses (e.g. Festuca arundinacaea and Lolium perenne) can produce toxic alkaloids, which are suspected to be involved in equine diseases such as fescue toxicosis, ryegrass staggers, and equine fescue oedema. The aim of this study was, therefore, to develop and validate a quantification method for these and related alkaloids: ergocristine, ergocryptine, ergotamine, ergovaline, lolitrem B, lysergic acid, N-acetylloline, N-formylloline, peramine, and paxilline in horse serum.Horse serum samples (1.5mL) were worked up by solid-phase extraction (OASIS HLB). The extracts were analyzed by ultra high performance liquid chromatography-high resolution tandem mass spectrometry (UHPLC-HRMS/MS). Chromatographic separation was achieved by gradient elution with ammonium formate buffer and acetonitrile on a RP18 column (100×2.1mm; 1.7μm). HRMS/MS detection was performed on a QExactive Focus instrument with heated positive electrospray ionization and operated in the parallel reaction monitoring (PRM) mode. Method validation included evaluation of selectivity, matrix effect, recovery, linearity, limit of quantification (LOQ), limit of detection (LOD), accuracy, and stability.With exception of lolitrem B solid phase extraction yielded high recoveries (73.6–104.6%) for all analytes. Chromatographic separation of all analytes was achieved with a run time of 25min. HRMS/MS allowed sensitive detection with LODs ranging from 0.05 to 0.5ng/mL and LOQs from 0.1 to 1.0ng/mL. Selectivity experiments showed no interferences from matrix or IS, but N-acetylloline and N-formylloline were found to be ubiquitous in horse serum. Newborn calf serum was therefore used as surrogate matrix for the validation study. Calibration ranges were analyte-dependent and in total covered concentrations from 0.1 to 50ng/mL. Lolitrem B and paxilline could be sensitively detected, but did not meet quantification requirements. For the other analytes, accuracy and precision were shown for 3 different concentrations (QC low, medium, high) with acceptable bias (−10, 5%–7.9%) and precision (CV 2.6%–12.5%). Matrix effects varied from 55.0% to 121% (RSD 7.8–18.5%) and were adequately compensated by IS. Matrix effects of N-acetylloline and N-formylloline could only be estimated in newborn calf serum (n=1) and ranged from 52.5–88.3%. All analytes were stable under autosampler conditions and over 3 freeze and thaw cycles. Applicability was proven by analyzing authentic horse serum samples (n=24).In conclusion, the presented method allows a sensitive detection of ergocrisitine, ergocryptine, ergotamine, ergovaline, lolitrem B, lysergic acid, N-acetylloline, N-formylloline, peramine, and paxilline in horse serum and reliable quantification of all but lolitrem B and paxilline.

Ergovaline does not alter the severity of ryegrass staggers induced by lolitrem B

AIM: To investigate a possible interaction between lolitrem B and ergovaline by comparing the incidence and severity of ryegrass staggers in sheep grazing ryegrass (Lolium perenne) containing lolitrem B or ryegrass containing both lolitrem B and ergovaline.METHODS: Ninety lambs, aged approximately 6 months, were grazed on plots of perennial ryegrass infected with either AR98 endophyte (containing lolitrem B), standard endophyte (containing lolitrem B and ergovaline) or no endophyte, for up to 42 days from 2 February 2010. Ten lambs were grazed on three replicate plots per cultivar. Herbage samples were collected for alkaloid analysis and lambs were scored for ryegrass staggers (scores from 0–5) weekly during the study. Any animal which was scored ≥4 was removed from the study.RESULTS: Concentrations of lolitrem B did not differ between AR98 and standard endophyte-infected pastures during the study period (p=0.26), and ergovaline was present only in standard endophyte pastures. Ryegrass staggers was observed in sheep grazing both the AR98 and standard endophyte plots, with median scores increasing in the third week of the study. Prior to the end of the 42-day grazing period, 22 and 17 animals were removed from the standard endophyte and AR98 plots, respectively, because their staggers scores were ≥4. The cumulative probability of lambs having scores ≥4 did not differ between animals grazing the two pasture types (p=0.41).CONCLUSIONS AND CLINICAL RELEVANCE: There was no evidence for ergovaline increasing the severity of ryegrass staggers induced by lolitrem B. In situations where the severity of ryegrass staggers appears to be greater than that predicted on the basis of concentrations of lolitrem B, the presence of other tremorgenic alkaloids should be investigated.

Ergot alkaloid intoxication in perennial ryegrass (Lolium perenne): an emerging animal health concern in Ireland?

Four primary mycotoxicosis have been reported in livestock caused by fungal infections of grasses or cereals by members of the Clavicipitaceae family. Ergotism (generally associated with grasses, rye, triticale and other grains) and fescue toxicosis (associated with tall fescue grass, Festuca arundinacea) are both caused by ergot alkaloids, and referred to as ‘ergot alkaloid intoxication’. Ryegrass staggers (associated with perennial ryegrass Lolium perenne) is due to intoxication with an indole-diperpene, Lolitrem B, and metabolites. Fescue-associated oedema, recently described in Australia, may be associated with a pyrrolizidine alkaloid, N-acetyl norloline.Ergotism, caused by the fungus Claviceps purpurea, is visible and infects the outside of the plant seed. Fescue toxicosis and ryegrass staggers are caused by Neotyphodium coenophalium and N. lolii, respectively. Fescue-associated oedema has been associated with tall fescue varieties infected with a specific strain of N. coenophialum (AR542, Max P or Max Q). The name Neotyphodium refers to asexual derivatives of Epichloë spp., which have collectively been termed the epichloë fungi. These fungi exist symbiotically within the grass and are invisible to the naked eye.The primary toxicological effect of ergot alkaloid involves vasoconstriction and/or hypoprolactinaemia. Ingestion of ergot alkaloid by livestock can cause a range of effects, including poor weight gain, reduced fertility, hyperthermia, convulsions, gangrene of the extremities, and death. To date there are no published reports, either internationally or nationally, reporting ergot alkaloid intoxication specifically associated with perennial ryegrass endophytes. However, unpublished reports from the Irish Equine Centre have identified a potential emerging problem of ergot alkaloid intoxication with respect to equines and bovines, on primarily perennial ryegrass-based diets. Ergovaline has been isolated in varying concentrations in the herbage of a small number of equine and bovine farms where poor animal health and performance had been reported. Additionally, in some circumstances changes to the diet, where animals were fed primarily herbage, were sufficient to reverse adverse effects. Pending additional information, these results suggest that Irish farm advisors and veterinarians should be aware of the potential adverse role on animal health and performance of ergot alkaloids from perennial ryegrass infected with endophytic fungi.

Physiological effects of endophyte-infected perennial ryegrass straw on female camels in the Middle East

Recently, the United Arab Emirates has increased importation of perennial ryegrass (Lolium perenne) straw as part of the grass/hay ration for camels. Unfortunately, perennial ryegrass straw may be infected with the endophyte Neotyphodium lolii which produces lolitrem B, a toxic alkaloid responsible for the disease ‘ryegrass staggers.’ A range-finding study was conducted using 24 non-pregnant female camels fed four doses (0, 1111, 1478 and 2273 ppb) of lolitrem B-containing perennial ryegrass straw over 56 days to establish a threshold of toxicity in camels so that perennial ryegrass straw can be safely fed as part of their dietary ration. Physiological parameters were evaluated. Neurological deficits were evaluated by videotape and scored according to an established scale for the neurological syndrome ryegrass staggers. Camels in the endophyte-infected groups developed varying degrees of ataxia. Brain edema, degenerative renal and hepatic lesions as well as Purkinje cell vacuolar degeneration were observed in camels receiving the highest dose. To avoid clinical disease in camels, endophyte-infected perennial ryegrass straw should be fed at 500 ppb or lower lolitrem B; straw at 1000 ppb or higher should be diluted to achieve the 500 ppb threshold of toxicity.

Toxicological evaluation and bioaccumulation potential of lolitrem B, endophyte mycotoxin in Japanese black steers

Lolitrem B, a causative toxin for ryegrass staggers, is produced by Neotyphodium lolii infecting perennial ryegrass (Lolium perenne). Japanese black cattle have been suspected to be more sensitive to lolitrem B than to other strains, and there has been a concern about the public health hazard of eating beef contaminated with lolitrem B. We carried out a feeding experiment to examine the sensitivity of Japanese black cattle to lolitrem B and the residual level of lolitrem B in several animal tissues. Japanese black steers were fed a 0, 500, 750, 1000, 1500 or 2000 µg kg−1 diet of lolitrem B provided by endophyte-infected perennial ryegrass straw for 12 weeks. All six animals in the 2000 µg kg−1 diet group exhibited ryegrass staggers symptoms. Furthermore, two out of three animals in the 1500 µg kg−1 diet group, three out of six animals in the 1000 µg kg−1 diet group and one out of three animals in the 750 µg kg−1 diet group presented clinical signs of ryegrass staggers. These results suggest that a daily intake of 18 µg kg−1 body weight of lolitrem B can produce ryegrass staggers in Japanese black steers. Perirenal fat tissues of the steers from those groups having one or more animals exhibiting ryegrass staggers symptoms contained approximately 150 ng g−1 of lolitrem B, while only small amounts of lolitrem B were detected in muscle, liver and kidney. Because the residual amount of lolitrem B in tissues of Japanese black cattle is small, the exposure to lolitrem B in consumers of the beef is likely to be low.

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.

黒毛和種繁殖牛に認められた輸入ストローによるライグラススタッガーの1症例

繁殖雌牛33頭を飼養する黒毛和種牛繁殖農場において，輸入ペレニアルライグラスストローを1日1頭あたり6kg 給与したところ，4頭が給与6～7日目に食欲不振となり，うち1頭が振戦，後弓反張及び起立不能を呈して死亡した．種子内に，エンドファイト様菌糸が確認された．同ストロー中ロリトレムB濃度は約2,000μg/kgであり，繁殖雌牛は毒性量のロリトレムBを摂取したと考えられた．死亡牛の急性硝酸塩中毒，低カルシウム血症，低マグネシウム血症，大脳皮質壊死症，BSE，脳脊髄炎及びコリンエステラーゼ阻害物質による中毒が否定された．以上から，死亡牛の神経症状をライグラススタッガーと診断した．黒毛和種牛におけるロリトレムBの毒性量などの詳しい病態に関する情報は少ないため，本症例で得られた知見は有益である.

The Molecular Mechanism of “Ryegrass Staggers,” a Neurological Disorder of K+ Channels

"Ryegrass staggers" is a neurological condition of unknown mechanism that impairs motor function in livestock. It is caused by infection of perennial ryegrass pastures by an endophytic fungus that produces neurotoxins, predominantly the indole-diterpenoid compound lolitrem B. Animals grazing on such pastures develop uncontrollable tremors and become uncoordinated in their movement. Lolitrem B and the structurally related tremor inducer paxilline both act as potent large conductance calcium-activated potassium (BK) channel inhibitors. Using patch clamping, we show that their different apparent affinities correlate with their toxicity in vivo. To investigate whether the motor function deficits produced by lolitrem B and paxilline are due to inhibition of BK ion channels, their ability to induce tremor and ataxia in mice deficient in this ion channel (Kcnma1(-/-)) was examined. Our results show that mice lacking Kcnma1 are unaffected by these neurotoxins. Furthermore, doses of these substances known to be lethal to wild-type mice had no effect on Kcnma1(-/-) mice. These studies reveal the BK channel as the molecular target for the major components of the motor impairments induced by ryegrass neurotoxins. Unexpectedly, when the response to lolitrem B was examined in mice lacking the beta4 BK channel accessory subunit (Kcnmb4(-/-)), only low-level ataxia was observed. Our study therefore reveals a new role for the accessory BK beta4 subunit in motor control. The beta4 subunit could be considered as a potential target for treatment of ataxic conditions in animals and in humans.

Progress in breeding sheep for resistance to ryegrass staggers

Ryegrass Staggers (RGS) is predominantly a summer/autumn metabolic disorder of ruminants, caused by ingestion of the toxin lolitrem B. The toxin is produced by an endophyte (Neotyphodium lolii) found in perennial ryegrass (Lolium perenne). In clinical cases of RGS, animals experience neuromuscular uncoordination when under stress, e.g. when mustered by sheep dogs. Experiments with a standardised RGS scoring system show that resistance/susceptibility in sheep has a moderate/high heritability (0.37 ± 0.05). An AgResearch flock was established in 1993, with two lines bred for resistance (R) or susceptibility (S) to RGS. Annually, lambs are scored for susceptibility, when both lines graze together on high endophyte pastures, and are mustered by sheep dogs. In 2005 and 2006, 2% and 6.5% of R-line lambs, respectively, showed clinical staggers, compared with 94% and 91% of S-line lambs (P

Toxicological evaluation of endophyte-infected perennial ryegrass straw to Japanese Black steers

Experimental feeds containing 0, 500, 1000, 1500 or 2000 ppb of lolitrem B derived from perennial ryegrass straw were fed to 9 month-old Japanese Black steers (average liveweight 180 kg) to determine their threshold level of lolitrem B. Steers received feeds containing 1000, 1500 and 2000 ppb of lolitrem B showed signs of ryegrass staggers after 2 to 7 weeks of feeding. The lowest observed adverse effect level (LOAEL) of lolitrem B was approximately 24 μg/kg body weight per day. Only small amounts of lolitrem B residue were detected in muscle, liver, kidney and cerebrum. In contrast, approximately 100 ng/g of lolitrem B was detected in perirenal fat of steers with ryegrass staggers. Keywords: Lolitrem B, Japanese Black cattle, ryegrass staggers, muscle, fat

A review of the ergot alkaloids found in endophyte-infected tall fescue and perennial ryegrass and their metabolism after ingestion by livestock

Tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) are perennial cool-season grasses which are infected with the endophytic fungi, Neotyphodium coenophialum and N. lolii, respectively. These endophytes have been increasingly selected for, as they confer benefits such as pest resistance and drought tolerance to the plant. However, livestock grazing endophyte-infected (E+) grasses are negatively impacted by fungal ergot and lolitrem alkaloids, which are responsible for a variety of mammalian diseases including fescue toxicosis (summer syndrome, fescue foot and fat necrosis) and ryegrass staggers. Most likely, not all of the ergot alkaloids involved in fescue toxicosis have been identified to date. During sample processing for the diagnostic analysis of the endophyte toxin ergovaline, other unidentified peaks occasionally elute that appear to coincide with clinical disease. Analysis of unidentified chromatographic peaks was performed on feed samples by LCMS/ MS to determine their chemical structures and identities. Ergotamine, ergovaline, ergocornine, ergonovine, ergocryptine, ergocrystine and lysergol appeared in various samples and matched controls. Newly identified compounds included ergosine, ergostine and ergoptine. In addition, several samples showed one or more of fourteen new ergots ranging in size from 381-611 mw, with key mass spectral characteristics of ergot alkaloidsspecifically, m/z 223 and 208 corresponding to the ergoline ring system and its demethylated variant, respectively. Once ingested, ergot alkaloids are thought to be metabolised in the rumen and/ or liver of livestock species. Ruminal metabolism of ergovaline was studied in sheep offered Neotyphodium coenophialuminfected tall fescue straw at two ergovaline levels (

Phytoalexins and endophyte related mycotoxins as hazards to the animal industry

Phytoalexins, compounds produced by plants in response to pathogens, and biologically active metabolites produced by endophyte are beneficial to plant growth. There are many trials to utilize these biologically active substances for plant disease control. On the other hand, some of these substances are toxic to mammals. We experienced ryegrass staggers of cattle caused by endophyte infected ryegrass straw. In this review, toxicities of phytoalexins and endophyte related substances to animals are overviewed. Furthermore, toxic substances found in false smut balls in rice plant are cited.

Ryegrass endophyte (Neotyphodium lolii) alkaloids and mineral concentrations in perennial ryegrass (Lolium perenne) from southwest Victorian pasture

On all of 120 farms in south-west Victoria that were selected at random and sampled during autumn and winter over 2 years, perennial ryegrass was present in the pasture and tested positive for the presence of the naturally occurring ryegrass endophyte, Neotyphodium lolii (mean frequency 78%). Ryegrass staggers were reported on 33% (1999) and 43% (2000) of the surveyed farms. Clinically significant concentrations of lolitrem B were detected in perennial ryegrass samples with concentrations in the range 0–4.44 mg/kg. Concentration exceeded 1.8 mg/kg in 37% of pastures indicating an inherent, widespread problem for livestock farmers. Concentration was independent of endophyte frequency, pasture age, pasture height, annual rainfall and origin of sown cultivar. Ergovaline was detected in most of the perennial ryegrass samples with concentrations up to 3.90 mg/kg. In 1999, the mean concentration of ergovaline was 0.76 (± 0.70) mg/kg with 33% of pastures having a level &gt;0.4 mg/kg, the level associated with heat stress in cattle. In 2000, sampling was carried out later in the year than for the 1999 survey and the mean concentration of ergovaline was 0.12 (± 0.10) mg/kg; 3% of samples exceeded 0.4 mg/kg. The mean concentration of peramine was 13.7 (± 6.6) mg/kg in the 1999 survey and 4.2 (± 5.1) mg/kg in the 2000 survey. Mineral analysis indicated that perennial ryegrass nutrition was inadequate with regard to phosphorous on 17% of the dairy pastures and on 37% of the sheep/beef pastures. Potassium was deficient in perennial ryegrass on 5 and 37% of dairy and sheep/beef pastures respectively. For perennial ryegrass in sheep/beef pastures, 25% were deficient in sulphur. For lactating cattle having only perennial ryegrass as a food source, phosphorous and copper concentrations in the grass were inadequate on 80% of the pastures. Calcium, zinc, magnesium, potassium and sulphur concentrations in perennial ryegrass were also inadequate on some pastures. However, with 1 exception, the ratio [K/(Ca+Mg) expressed as equivalents] was less than 2.2, the level associated with the development of hypomagnesemia. Hypomagnesemia (grass tetany) was therefore unlikely to be a major cause of the staggers syndrome. Lolitrem B was negatively correlated with grass potassium concentration (P&lt;0.001). Ergovaline was negatively correlated with date of sampling (P&lt;0.001). Peramine concentration was positively correlated with endophyte frequency, the potassium and sodium concentrations in perennial ryegrass and negatively correlated with date of sampling. The need for research on the economic impact and management of pasture contaminated with ryegrass endophyte toxins is discussed.

Farmer experience of perennial ryegrass endophyte on a Manawatu dairy farm

Case studies of two Manawatu properties currently experiencing ryegrass staggers (RGS) are presented; a dairy farm and a run-off grazing both dairy heifers and intensive bull beef. Before its conversion from a sheep and cattle enterprise to dairying an outbreak of RGS was experienced in 1987. Tall fescue-based pastures were established to minimise the potential threat of RGS. In the intervening 12 years high endophyte ryegrass cultivars have been established and hotter, drier summers are being experienced in this region. Severe cases of RGS have been observed in the last three years. On the dairy farm in 1998/99, 21 cows were dried off in January due to severe RGS. The loss in production is impossible to measure. Sixteen heifers and weaner bulls died during that summer due to RGS and those alive were 35 kg LWT below target. Management options to reduce the effects of endophyte-related disorders include establishing non-toxic pastures such as tall fescue or forage crops to utilise during periods of the year when RGS can be experienced. While limited in cultivar choice at present, the use of novel endophytes provides long-term options for farmers wishing to reduce RGS yet still maintaining ryegrass pastures. Including herbaceous species such as chicory or plantain in pasture mixes will provide high quality summer forage and can dilute the effects of endophyte in the total daily intake. Keywords: bull beef, dairy cows, endophyte, heifers, perennial ryegrass, ryegrass staggers

Six years of selection responses for resistance or susceptibility to ryegrass staggers in sheep

Ryegrass staggers (RGS) is a neurotoxic disease in ruminants. It is caused by the mycotoxin lolitrem B, found in endophyte-infected perennial ryegrass (Lolium perenne L.). This paper reviews genetic studies on the resistance of sheep to RGS at Ruakura. Genetic differences in susceptibility among sire groups were evaluated in lambs born in 1988-92 (Phase 1). Selection lines were then formed and responses to selection for resistance or susceptibility are described for the 1993-98 birth years (Phase 2). The incidence of RGS was recorded on a presence or absence basis from January to March or April each year, in experimental flocks with animals of known pedigree. For estimating genetic parameters (Phase 1), there were 3587 RGS records available from 2307 animals representing 232 sires. Clinical cases of RGS occurred in 17 of 25 contemporary groups, with incidences per group up to 16%. Estimates of heritability and acrossyear repeatability for RGS incidence were 0.068 ± 0.028 and 0.24 ± 0.05 respectively. Breeding value data were used at the beginning of Phase 2 to screen ewes, two-tooths and ewe lambs into resistant and susceptible selection flocks (lines). Breeding values were also used to select rams that were elite for RGS, and to allocate these to each line for mating. At least some natural RGS challenge was experienced by the resulting selection-line stock born in five of the six years of Phase 2. Susceptible-line lambs had a mean incidence of 39% clinical RGS cases over these five years, whilst the resistant-line lambs grazing the same paddocks had a much lower mean clinical RGS incidence (P

Toxicology of ryegrass endophyte in livestock

The ryegrass endophyte/plant interaction produces a number of toxic metabolites responsible for a range of toxicoses including ryegrass staggers. Although lolitrem B has long been considered the toxin responsible for ryegrass staggers in farm animals, it is only recently that we have demonstrated that oral administration of the pure toxin causes tremors in mice consistent with the symptoms of ryegrass staggers. Various levels of the toxin were incorporated into the diet of mice and tremor response measured regularly. Mice were very susceptible to the tremorgenic action of lolitrem B with a dose of only 1.1 mg/kg per day being sufficient to induce a tremor response. Analysis of faeces from a dosed mouse showed that approximately 40% of the toxin ingested was excreted unchanged. The profile of tremor response shows that tremors build up over a 24-hour period and then reach a dose dependent plateau suggesting that toxin turnover reaches a steady state. In experiments designed to test the possibility that tremorgens bind to specific receptors in the brain, mice were injected with the 14C-labelled tremorgen, paxilline. Paxilline was chosen as it is similar in structure and possible action to lolitrem B and could be more easily prepared with an isotopic label. Following injection of 14C-paxilline to mice their brains and spinal cord were sectioned and analysed for 14C content. Localised binding was not detected but rather an even distribution of isotope was observed. This is probably due to the lipophilicity of the tremorgens, which distribute randomly throughout the fatty brain matrix, masking any binding to specific regions or receptors. This study showed, however, that only a minute proportion of the administered tremorgen reached the brain and spinal cord, indicating that, if this is the site of action, the receptors involved in the initiation of staggers are extremely sensitive to the tremorgens. Keywords: endophyte, lolitrem, Lolium perenne, mycotoxin, Neotyphodium lolii, neurotoxin, oral dosing, ryegrass staggers, tremor, tremorgen

Experiences of ryegrass endophyte on farms on the East Coast of the North Island

A case study of a Hawke's Bay farm with a history of ryegrass staggers (RGS) and results of a survey of veterinarians from three regions are presented. A RGS outbreak in 1989 on the 'Tunanui' property at Sherenden resulted in the loss of 900 sheep and three cattle, with total costs estimated to be $61,000. There have been no severe outbreaks since then, despite similar climatic conditions occurring. The probable reason for this is a combination of improved awareness of RGS and conscious avoidance of the problems, and the indirect effects of other changes to farm management. The survey of veterinarians showed a rise in the prevalence of ryegrass endophyte related disorders in Manawatu and Waikato between the 1980s and 1990s, but no change for East Coast regions. Veterinarians spend very little time assisting clients with endophyte related problems, despite 41% of clients having problems. It is recommended that veterinarians provide more prevention advice to farmers, and farm management practices that successfully reduce RGS be promoted. Keywords: cattle, deaths, disorders, East Coast, farm, prevalence, remedies, ryegrass staggers, sheep, veterinarians