Level of zearalenone in blood serum and lesions in ovarian follicles of sexually immature gilts in the course of zearalenone micotoxicosis

The aim of the study was to determine how a low dose of zearalenone applied orally for eight days influences the level of zearalenone (ZEN) and alpha-zearalenole in blood plasma and causes the occurrence of histopathological changes in the cells of the ovarian follicles in sexually immature gilts. The animals were divided into 2 groups (control, C; n = 4 and experimental, E; n = 4). The gilts from group E were treated daily with zearalenone at a dose of 200 microg/kg b.w. The level of zearalenone and alpha-zearalenole (ZON as the sum of the levels of both zearalenone and alpha-zearalenole) was measured daily. On day eight of the experiment the animals were sacrificed and their ovaries were taken for histopathological examination. The tissue sections obtained were HE- and PAS-stained according to McManus. The presence of PCNA antigen was also estimated. The highest concentration of ZON was noted on day 5 in group E (8.16 +/- 2.49 ng/ml). External estrus symptoms without standing reflex were observed in group E on day 4. In group C there were no pathological changes in the ovaries. In group E, a few ovarian follicles were found, but they were located in the cortical layer. They were filled with a liquid substance rich in protein and without the granulosa layer. There was disintegration with apoptotic-like changes of the PCNA-negative cells in the granulosa layer of single mature follicles. On day 4 the dose of zearalenone caused disturbances in the process of development and maturation of some of the best developed ovarian follicles. This probably occurred through the activation of on apoptosis-like process of the granulosa cells with simultaneous manifestation of estrus without standing reflex.

Effect of probiotic containing Saccharomyces boulardii on experimental ochratoxicosis in broilers: hematobiochemical studies

In the present investigation, the toxicopathological effects of ochratoxin A of 0.5 ppm on hematobiochemical parameters of broilers were studied with efficacy of dietary concentration of probiotic containing yeast culture Saccharomyces boulardii of 10 mg/kg of feed. One hundred twenty day old chicks were randomly divided into four groups, thirty chicks each. Groups A and C chicks were offered normal feed and that added with probiotic Saccharomyces boulardii respectively. The birds in group B were fed ochratoxin A of 0.5 ppm of feed. Where as, the birds of group D, were fed with ochratoxin A of 0.5 ppm along with probiotic Saccharomyces boulardii of 10 mg/kg of diet. Hematological studies carried revealed significant decrease in the haemoglobin and packed cell volume in birds of group B and reduced effect in birds of group D due to probiotic. Biochemical profiles revealed significant improvement in probiotic treated group D when compared with decreased values of Total protein, albumin, globulin and increased levels of serum creatinine and SGPT in birds of groups B.

Experimental Mycotoxicosis in Chickens Induced by Ochratoxin A and Penicillic Acid and Intervention with Natural Plant Extracts

The combined toxic effect of ochratoxin A (OTA) and penicillic acid (PA) on the body mass, the weight and pathomorphology of some internal organs was studied in 85 broiler chickens fed a mouldy diet containing 130, 300 or 800 ppb OTA and 1000-2000 ppb PA. The main pathomorphological changes were cloudy swelling and granular degeneration in the epithelium and mononuclear cell proliferation and activation of capillary endothelium in the kidney and liver; degenerative changes and depletion of lymphoid cells in lymphoid organs (bursa of Fabricius, thymus and spleen) were also seen. Protective effects of 5% total water extract of artichoke and a new natural phytosubstance Rosallsat against these pathomorphological changes were observed. A significant decrease in body mass and relative weight of lymphoid organs was found after 6 weeks of exposure and a greater decrease after 10 weeks of exposure to OTA and PA, and a protective effect of artichoke extract and a slight effect of Rosallsat against that decrease was observed. A significant increase in relative weight of liver and kidneys was also observed as well as a protective effect of artichoke extract against that increase. The quantity of OTA and the percentage of positive samples were significantly lower in tissues of chickens treated with artichoke extract or Rosallsat in addition to OTA than in those treated with only OTA.

Effects of feeding blends of grains naturally contaminated with Fusarium mycotoxins on performance and metabolism of laying hens

An experiment was conducted to evaluate the effects of feeding laying hens grains naturally contaminated with a combination of Fusarium mycotoxins. Parameters measured included performance, organ weights, and plasma chemistry. One hundred and forty-four, 45-wk-old laying hens were fed diets including: (1) control, (2) contaminated grains, and (3) contaminated grains + 0.2% polymeric glucomannan mycotoxin adsorbent (GMA) for a 12-wk period. The feeding of contaminated grains decreased feed consumption compared with controls in the first 4 wk. Feed consumption increased, however, from 4 to 8 wk and from 8 to 12 wk. The efficiency of feed utilization (feed consumption/egg mass) decreased compared with controls in the periods from 4 to 8 and from 8 to 12 wk when birds were fed contaminated grains. Supplementation with GMA decreased feed consumption and increased the efficiency of feed utilization in the period from 8 to 12 wk. Egg production and egg mass decreased in wk 4 and 8 compared with controls when contaminated grains were fed, whereas egg and eggshell weights decreased in the fourth wk. Plasma uric acid concentrations increased throughout the experiment and relative kidney weights increased at the end of the experiment compared with controls when birds were fed contaminated grains. The feeding of GMA prevented the elevation in uric acid concentrations and relative kidney weights. It was concluded that layer performance and metabolism were adversely affected by chronic feeding of a combination of Fusarium mycotoxins, and that GMA prevented many of these effects.

Influence of dietary culture material containing aflatoxin and T2 toxin on certain serum biochemical constituents in Japanese quail

Forty newly hatched unsexed Japanese quail (Coturnix coturnix japonica) chicks were fed diets containing 3 ppm aflatoxin (AF) and 4 ppm T(2) toxin either singly and in combination for 35 days. Sera samples were collected from six birds in each group at the end of the trial to study the effect of certain serum biochemical parameters. Highly significant (P < 0.01) differences were observed for serum total protein, albumin, globulin, glucose, cholesterol, aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT) between control and toxin treated groups. Toxin treated groups did not reveal any significant difference for serum urea nitrogen, creatinine, uric acid, calcium, phosphorus, sodium and potassium. There was a reduction in the levels of serum total protein, albumin, globulin, glucose, cholesterol, ALT and elevation of AST and GGT and variable ALP levels observed in toxin treated groups.

Efficacy of a commercial mycotoxin binder in alleviating effects of ochratoxin A, fumonisin B1, moniliformin and zearalenone in adult mink

The addition of nutritionally inert adsorbents to mycotoxin-contaminated animal feed has been a popular approach to decreasing toxicity in animals and carryover of mycotoxins from contaminated feed to animal by-products. Some studies suggest that esterified glucomannan derived from the cell wall of Saccharomyces cerevisiae is effective in reducing the bioavailability of at least some of the mycotoxins occurring in contaminated feed. Because cereal grains are important components of ranch mink diets, mycotoxicoses in mink is a potential problem faced by mink ranchers. We conducted a series of studies to determine if inclusion of a commercially available esterified glucomannan in ranch mink feed was effective in alleviating clinical signs indicative of exposure to ochratoxin A, fumonisin B1, moniliformin or zearalenone in adult mink. In 4 separate trials, mink were fed diets that contained 2.5, 5 or 10 mg ochratoxin A/kg feed, 200 mg fumonisin B1/kg feed, 20 mg moniliformin/kg feed, or 30 mg zearalenone/kg feed with or without 2 g esterified glucomannan/kg feed. Male mink fed diets containing ochratoxin A had significantly decreased feed intake as well as renal lesions characteristic of exposure to that mycotoxin. Inclusion of the esterified glucomannan did not ameliorate these effects. Male mink exposed to fumonisin B1 had increased urinary sphinganine concentration, which was not significantly reduced by the mycotoxin adsorbent. Male mink that consumed monilformin-contaminated diets had characteristic ultrastructural changes in the heart that were not reduced in severity by the esterified glucomannan. Female mink exposed to zearalenone had increased uterine weight, which was not reversed by inclusion of commercial mycotoxin binder in the contaminated feed. The results of this study suggest that a commercial esterified glucomannan was generally ineffective in alleviating effects indicative of exposure to ochratoxin A, fumonisin B1, monilformin and zearalenone in mink.

Modification of zearalenone structure in model and natural conditions

Zearalenone is a mycotoxin widely occurring in cereals and animal feed, and it is associated with hyperestrogenism and other reprodutive disorders in animals. A new method of detoxication of feedstuffs involves alkaline hydrolysis of toxic macrolactone (1) (as well as model compounds (2a, 2b)). The method caused modification of zearalenone structure under mild conditions and the toxin underwent irreversible hydrolysis with high efficiency.

Metabolic profile of pigs fed feed containing zearalenone destructor

Zearalenone (ZEA) is a member of macrocyclic lactons family. It is a toxin--phytosteride produced by fungi of Fusarium ssp. genus. Zearalenone contaminates food and animal feeding stuffs and its destruction is difficult. It requires application of particular compounds that would bind zearalenone in the feed or feeding stuff or in the gastrointestinal tract and decrease its bio-accessibility. It should also fulfil all the safety requirements regarding the plant supplements and animals that are fed with this feed. The aim of the study was to estimate if the feed supplemented with different doses of zearalenone and zearalenone destructor causes changes of the metabolic profile in gilts. The results obtained show that applied destructor did not cause negative haematological and biochemical changes in the blood of the gilts examined. It can be suggested that it is a safe feed supplement pigs in prevention of zearalenone micotoxicosis.

Use of natural and synthetic aluminosilicates in decontamination of feed contaminated by fungi and micotoxins

The contamination of feed with micotoxin has been a serious problem in animal nutrition. Many existing methods of decontamination are not satisfying due to the toxicological safety and health quality of the fodder materials. It stimulates the scientists to search for the new methods. The use of sorbents in the form of natural and synthetic aluminosilicates is a promising direction. The efficacy of aluminosilicates towards aflatoxins has been proved. However, their influence on other micotoxins is not that obvious. According to the last investigations, the use of aluminosilicates in nutrition does not cause any side effects and widespread pathological effects are observed only when dosage is incorrect. Regarding the analyses that were published, it can be supposed that the addition of several different aluminosilicates is a sufficient protection against mycotoxicoses.

Influence of zearalenone micotoxicosis on selected immunological, haematological and biochemical indexes of blood plasma in bitches

The immunological, haematological and biochemical analyses of blood plasma in bitches with 50 days lasting induced zearalenone micotoxicosis were carried out. It can be indirectly suggested that the inhibition of the humoral reaction of the organism, stimulation of detoxification effect in the liver and decreased cellular answer took place.

Efficacy of esterified glucomannan to counteract mycotoxicosis in naturally contaminated feed on performance and serum biochemical and hematological parameters in broilers

A study was conducted to determine the efficacy of esterified glucomannan in counteracting the toxic effects of mycotoxins in naturally contaminated diet (aflatoxin 168 ppb, ochratoxin 8.4 ppb, zearalenone 54 ppb, and T-2 toxin 32 ppb) fed to commercial broilers. One-day-old broiler chicks were randomly assigned to one of the four dietary treatments with five replicates of 14 chicks each. Four dietary treatments were 1) control; 2) esterified glucomannan, an adsorbent, tested at 0.05% of diet; 3) naturally contaminated diet; and 4) esterified glucomannan (0.05%) plus naturally contaminated diet. Body weight, feed consumption, feed efficiency, hematology, and serum biochemical and enzyme activities were evaluated. Compared with the control, the naturally contaminated diet significantly decreased body weight and feed consumption and resulted in poor feed efficiency. Esterified glucomannan effectively alleviated the growth depression caused by the naturally contaminated diet. Increased relative weights of liver and gizzard were observed in chicks fed the naturally contaminated diet. Further, feeding a naturally contaminated diet was associated with significant decreases in urea nitrogen and hematocrit values along with altered gamma-glutamyl transferase activity; however, urea nitrogen concentration was improved with addition of esterified glucomannan. These findings suggest that addition of dietary esterified glucomannan is effective in counteracting the toxic effects of naturally contaminated feed with mycotoxins.

Zearalenone--undesirable substances in feed

The main arguments, discussed by different international organizations, which confirm the significance of problems connected with the presence of zearalenone in animal feed materials and their influence on the safety of food materials are shown in this review article. The main world research trends focused on zearalenone, as undesirable substances, are also presented. A variety of Fusarium fungi produce a number of different mycotoxins, for example zearalenone. Is not true that Fusarium fungi are they the most prevalent toxin-producing fungi only in the northern temperate regions, are also commonly found on cereals grown in the temperate regions of America, Europe and Asia. Zearalenone have been shown to cause a variety of toxic effects in both experimental animals and livestock, and have also been suspected of causing toxicity in humans. Zearalenone is a stable compound, both during storage/milling and the processing/cooking of food, and it does not degrade at high temperatures. Studies of metabolism indicate that zearalenone is fairly rapidly absorbed following oral administration, with the formation of alpha- and beta-zearalenol and alpha- and alpha-zearalanol, which are subsequently conjugated with glucuronic acid. This mycotoxin and some of these metabolites have been shown to competitively bind to estrogen receptors in a number of in vitro systems. Binding to specific receptors has been demonstrated in the uterus, mammary gland, liver and hypothalamus of different species. Additionaly alterations of immunological parameters were found at high zearalenone concentrations in vitro. Zearalenone causes alterations in the reproductive tract of laboratory animals and domestic animals. Various estrogenic effects such as decreased fertility, increased embryolethal resorptions, reduced litter size, changed weight of adrenal, thyroid and pituitary glands and change in serum levels of progesterone and estradiol have been observed, and teratogenic effects were found in pigs and sheep. It may be that the safety of zearalenone could be evaluated on the basis of the dose which had no hormonal effects in pigs, the most sensitive species, and a temporary Tolerable Daily Intake for zearalenone of 0.2 microgram/kg of body weight, could be established.

Tremorgenic mycotoxin intoxication with penitrem A and roquefortine in two dogs

In this report, we describe the natural intoxication of 2 dogs that consumed moldy dairy products found in the household garbage and the procedures used to identify and quantify the tremorgenic mycotoxins, roquefortine and penitrem A, in the remaining portions of ingested materials. Following the ingestion of mycotoxins, the dogs of our report developed muscle tremors or seizures that resembled clinical signs of strychnine poisoning. Roquefortine was the predominant mycotoxin in a moldy cream cheese wrapper that was found among scattered garbage consumed by the first dog. Penitrem A was the only mycotoxin detected in discarded moldy macaroni and cheese that was consumed by the second dog. Treatment of dogs with tremorgenic mycotoxin intoxication involves supportive care. Close monitoring is important because the development of aspiration pneumonia is common and has been reported as the cause of death. Clinical signs of intoxication gradually resolve within 24 to 48 hours.

Tremorgenic neuromycotoxicosis in 2 dogs ascribed to the ingestion of penitrem A and possibly roquefortine in rice contaminated with Penicillium crustosum

Two dogs developed alarming tremorgenic nervous stimulation shortly after ingesting discarded rice that had been forgotten in a refrigerator for an undetermined period and that was covered with a grey-green mould. Both dogs exhibited vomition followed by slight salivation, tremors and ataxia and 1 showed such severe agitation and seizures that it necessitated anaesthesia with thiopentone followed, on recovery, by xylazine. The other dog was only sedated with xylazine. They made an uneventful recovery. The rice vomitus yielded a pure culture of Penicillium crustosum. On chemical analysis it was negative for organochlorine, organophosphor and carbamate insecticides, as well as for strychnine, but contained 2.6 microg/g of the mycotoxins penitrem A as well as 34 microg/g of roquefortine as determined by LC-MS and confirmed by MS-MS. This is the 1st South African case of naturally occurring penitrem A toxicosis and also the 1st case where quantification of the levels of mycotoxins in dog vomitus is reported. The tremorgenicity of roquefortine and its contribution towards this syndrome, is questioned.

Tremorgenic mycotoxicosis in four dogs from a single household

Mycotoxins are fungal metabolites that induce undesirable effects. The effects of these mycotoxins vary depending on the chemical structure of the toxin and degree of toxicity. Mycotoxins that induce muscle tremors, ataxia, and convulsions are termed tremorgenic mycotoxins. Our report documents the clinical course of 4 dogs from a single household that were simultaneously affected by tremorgenic mycotoxins. Diagnosis of tremorgenic mycotoxicosis was confirmed by stomach content analysis from 1 of the dogs. The mycotoxins identified were penitrem A and roquefortine, which are both produced by Penicillium spp. Treatment goals following tremorgenic mycotoxin ingestion include minimizing absorption, controlling tremors and seizures with methocarbamol and pentobarbital sodium administration, and providing supportive care. Two of the affected dogs required ventilatory support. With early aggressive treatment, prognosis is good and recovery is complete without sequelae. It is helpful for the clinician to be familiar with the typical clinical signs at the time of admission, treatment, and clinical course of dogs with tremorgenic mycotoxicosis.

Plant poisonings and mycotoxicoses of importance in horses in southern Africa

Well-known plant poisonings such as 'dunsiekte' (seneciosis) and 'jaagsiekte' (crotalariosis) of horses in southern Africa are briefly reviewed. Relatively unfamiliar mycotoxicoses such as stachybotryotoxicosis and perennial rye grass staggers and potentially occurring exotic intoxications such as equine nigropallidal encephalomalacia and ergot alkaloid poisoning are also discussed. This article is aimed at informing the southern African equine practitioner about probable poisonings that might occur locally in horses.

Acute penitrem A and roquefortine poisoning in a dog

Penitrem A and roquefortine poisonings were diagnosed in a Laborador retriever following garbage consumption. Clinical signs of mycotoxicosis included polypnea, tachycardia, and ataxia that quickly progressed to lateral recumbency and seizures. Removal of the mycotoxins from the stomach soon after ingestion allowed the dog to recover within 72-96 hours.

Mycotoxins

The relevance of many mycotoxins to small animal health is difficult to assess, because available information has not been collated and reviewed. Only aflatoxins, penitrem A, and roquefortine have been confirmed in natural mycotoxicoses in pets. Effects of tricothecene mycotoxins, patulin, and penicillic acid on dogs and cats have only been studied experimentally and have not been confirmed in natural outbreaks. Although they make up only a small portion of the cases presented to veterinarians, mycotoxicoses often require special effort. Establishing an accurate diagnosis is crucial to minimize exposure and provide adequate treatment. In most cases, clinical examination, clinical pathologic testing, and analytical chemistry analysis of suspect feed are necessary to reach a diagnosis.

Biological suppression of aflatoxicosis in Japanese quail (Coturnix coturnix japonica) by dietary addition of yeast (Saccharomyces cerevisiae)

The amelioration of aflatoxicosis in Japanese quails was examined by the dietary addition of live yeast (Saccharomyces cerevisiae; SCE). Yeast incorporated into the diet at 1 g kg(-1) was evaluated for its ability to reduce the deleterious effects of 2.5 mg total aflatoxin (AF; 82.30 per cent AFB1, 2.06 per cent AFB2, 7.68 per cent AFG1 and 7.96 per cent AFG2) kg(-1)diet on growing Japanese quail chicks from 10 days to 45 days of age. Forty 10-day-old Japanese quail chicks were assigned to 2x2 factorial arrangement of treatments (control, AF, SCE, AF plus SCE) each consisting of 10 quails. The performances of birds were evaluated. The AF treatment significantly and dramatically decreased food consumption and body-weight gain from the first week onwards. The significant adverse effect of AF on the food conversion ratio was also determined from week 1 to the end of the experiments. The addition of SCE to the AF -containing diet significantly reduced these deleterious effects of AF on food consumption, body-weight gain and food conversion ratio. Compared to controls, the cumulative body weight gain was reduced by 37 per cent among the quails consuming AF without SCE, but increased 15 per cent for the birds fed AF plus SCE. Interestingly, the single inclusion of SCE to the AF-free diet provided significant improvements in all the investigated growth performances of birds (approximately 40 per cent) compared to controls.

Mycotoxins

Horses consume feed grains and forages that can produce a range of mycotoxins resulting from mold invasion. Toxicosis of horses often occurs from fumonisins or aflatoxin in grains, from the tremorgenic mycotoxins in dallis grass, or from slaframine in red clover. Fumonisin toxicosis often is severe and fatal, and aflatoxin can be acute or chronic and debilitating. Other mycotoxins reported in horses may cause moderate to mild signs that regress when the contaminated feedstuff is removed. Overall, horses appear to have a relatively low prevalence of reported mycotoxicoses among domestic animals, but they are extremely sensitive to the fumonisins. Since there are no good therapies for mycotoxin poisoning, attention to providing high quality grains and forages to prevent mycotoxicoses is the most effective means for reducing the risk of mycotoxins in horses.

Ameliorative effects of dietary clinoptilolite on pathological changes in broiler chickens during aflatoxicosis

The amelioration of aflatoxicosis in broiler chickens was examined by feeding two concentrations of natural zeolite (clinoptilolite). Clinoptilolite (ClI), incorporated into the diet at 1.5 and 2.5 per cent, was evaluated for the ability to reduce the deleterious effects of 2.5 mg total aflatoxin (AF) kg(-1)diet on growing broiler chicks from 1 to 21 days of age. A total of 360 broiler chicks were divided into six treatment groups [Control, AF, CLI (1.5 per cent), AF plus CLI (1.5 per cent), CLI (2.5 per cent), and AF plus CLI (2.5 per cent)] each consisting of 60 chicks. Compared to controls, the AF consuming chicks showed increases in the relative weights of liver and kidney; and gross-histopathologic hepatic lesions such as paleness, friability, diffuse hydropic degeneration and/or fatty change, bile-duct hyperplasia and periportal fibrosis. Glumerular hypertrophy, increases in the number of mesengial cells and hydropic degeneration of tubuler epithelium in kidneys of chicks fed diet AF alone were also observed. Atrophy and lymphoid depletion were seen in the thymuses and bursa of Fabricius from the chicks fed AF alone. The additions of CLI (1.5 and 2.5 per cent) to the AF -containing diet moderately (significantly in some cases) decreased the number of affected broilers and/or the severity of lesions. The addition of CLI to the AF-free diet did not produce any significant changes compared with the controls. These results suggest that CLI was effective for the protection of AF-toxication in broilers and it could contribute to a solution of the AF problem in poultry production.

Aflatoxin production in supplemental feeders provided for northern bobwhite in Texas and Oklahoma

Mycotoxins are toxic metabolites produced by varous species of fungi. Aflatoxin (AF), a particular type of mycotoxin, can negatively impact many wildlife species in the laboratory; however, the magnitude of the problem in the field environment is unclear. Wild birds generally consume a combination of native foods and agricultural grains. A common practice in which birds, such as northern bobwhite (Colinus virginianus), contact stored agricultural grain is through supplemental feeding. This feeding practice may promote the production of AF. The objectives of this study were to (1) examine AF production in supplemental feeders and (2) examine the relationship between weather and AF production in supplemental feeders. Samples were collected from supplemental feeders from November through February of 1996-97 and 1997-98. Mean monthly AF concentration of samples from feeders ranged from 0.57+/-2.86 to 15.47+/-14.69 ppb. Aflatoxin concentration in supplemental feeders increased from pre-sample to one month after filling the feeders each year. AF production in supplemental feeders was highly variable among months with no real temporal pattern between years. Instead, AF production was related to the highly variable relative humidity of the study area which influences moisture content of grain. Average relative humidity can be used to predict AF production.

Aflatoxin levels in corn available as wild turkey feed in Georgia

Samples of corn available as wildlife feed from retailers throughout Georgia (USA) were collected during April 1997 and analyzed for aflatoxin to determine if levels harmful to wild turkeys (Meleagris gallopavo) were present. Three of 31 (10%) samples collected from a 40-country area were positive. An enzyme-linked immunosorbent assay qualitatively determined that two samples contained from 0 to 20 ppb aflatoxin. A chromatography analysis of a third sample measured 380 ppb total aflatoxin. A small percentage of our sample of wildlife feed collected during one season contained levels of aflatoxin that may cause harm to turkeys, especially poults. However, because aflatoxin levels ranging from 100 to 400 ppb may cause liver dysfunction and immunosuppression in turkey poults and other wildlife, grains known to be contaminated with aflatoxin at levels unacceptable for domestic animal feeds (> or =100 ppb) should not be sold as wildlife feed. Further analyses of grains sold as wildlife feed should be conducted to address this potential problem.

Correlation of endophyte toxins (ergovaline and lolitrem B) with clinical disease: fescue foot and perennial ryegrass staggers

Fescue foot, summer syndrome, reproductive problems, and ryegrass staggers are all diseases of livestock related to endophyte toxins in pasture grasses. Range finding experiments and case studies of fescue foot relative to ergovaline toxin found in endophyte infected tall fescue and lolitrem B present in endophyte infected perennial ryegrass were conducted. Within 42 d of initiating a feeding trial with chopped tall fescue straw containing 825 ppb ergovaline and at environmental temperatures of 15.9 C clinical signs of fescue foot were seen in cattle. Sheep on tall fescue pastures in November consuming feed with 540 ppb ergovaline and at environmental temperatures of 7.8 C developed fescue foot in 21 d while sheep on the adjacent field in the previous 2 mo with environmental temperatures of 16.6 C and 12.8 C and 458 ppb ergovaline in the pasture grasses did not. In a field outbreak of fescue foot affecting 42/425 feeder lambs in November, the ergovaline of sample pasture grasses had a mean concentration of 813 ppb. Perennial ryegrass staggers was seen in 42/237 feeder lambs when mean lolitrem B in the sampled grass was 2,135 ppb. Overgrazing both tall fescue and ryegrass fields increased probability of clinical disease since the highest levels of toxin were found in the crowns and basal leaf sheaths of tall fescue and perennial ryegrass respectively. Based on these findings, ergovaline dietary levels of 400 to 750 ppb to cattle and 500 to 800 ppb to sheep and lolitrem B levels of 1,800 to 2,000 ppb in feed for both species are approximated threshold values for disease. Cold environmental temperatures are equally important to toxin concentrations in precipitating fescue foot disease.