Plant and Fungal Hepatotoxicities of Cattle in Australia, with a Focus on Minimally Understood Toxins

Plant- and fungus-derived hepatotoxins are a major cause of disease and production losses in ruminants in Australia and around the world. Many are well studied and described in the literature; however, this is not the case for a number of hepatotoxicities with economic and animal welfare impacts, such as acute bovine liver disease (ABLD), brassica-associated liver disease (BALD) and Trema tomentosa, Argentipallium blandowskianum and Lythrum hyssopifolia toxicity. Additionally, significant overlap in the clinical presentation and pathology of these conditions can present a diagnostic challenge for veterinarians. This review summarizes the current and most recently published knowledge of common plant- and fungus-associated hepatotoxins affecting cattle in Australia, with a focus on the mechanisms of toxicity and distinguishing diagnostic features. Consolidation of the current understanding of hepatotoxic mechanisms in cattle provides insight into the potential mechanisms of lesser-known toxins, including cellular and subcellular targets and potential metabolic pathways. In the absence of specific etiological investigations, the study of epidemiological, clinical and pathological features of hepatotoxicity provides valuable insights into potential toxic mechanisms and is integral for the successful diagnosis and management of these conditions.

Summer Pheasant's Eye (Adonis aestivalis) Poisoning in Three Horses

Three horses died as a result of eating grass hay containing summer pheasant's eye ( Adonis aestivalis L.), a plant containing cardenolides similar to oleander and foxglove. A 9-year-old thoroughbred gelding, a 20-year-old appaloosa gelding, and a 5-year-old quarter horse gelding initially presented with signs of colic 24–48 hours after first exposure to the hay. Gastrointestinal gaseous distension was the primary finding on clinical examination of all three horses. Two horses became moribund and were euthanatized 1 day after first showing clinical signs, and the third horse was euthanatized after 4 days of medical therapy. Endocardial hemorrhage and gaseous distension of the gastrointestinal tract were the only necropsy findings in the first two horses. On microscopic examination, both horses had scattered foci of mild, acute myocardial necrosis and neutrophilic inflammation associated with endocardial and epicardial hemorrhage. The third horse that survived for 4 days had multifocal to coalescing, irregular foci of acute, subacute, and chronic myocardial degeneration and necrosis. A. aestivalis (pheasant's eye, summer adonis) was identified in the hay. Strophanthidin, the aglycone of several cardenolides present in Adonis spp., was detected by liquid chromatography-mass spectrometry-mass spectrometry in gastrointestinal contents from all three horses. Although Adonis spp. contain cardiac glycosides, cardiac lesions have not previously been described in livestock associated with consumption of adonis, and this is the first report of adonis toxicosis in North America.

Toxicity of white snakeroot (Ageratina altissima) and chemical extracts of white snakeroot in goats

White snakeroot (Ageratina altissima) is a sporadically toxic plant that causes trembles in livestock and milk sickness in humans that drink tainted milk. The putative toxin in white snakeroot is tremetone and possibly other benzofuran ketones, even though it has not been demonstrated in vivo. Toxic white snakeroot was dosed to goats, and they developed clinical signs of poisoning, exercise intolerance, significant increases in serum enzyme activities, and histological changes. Tremetone and the other benzofuran ketones were extracted with hexane; the extracts and residues were analyzed for tremetone and dosed to goats at tremetone and benzofuran ketone concentrations similar to the original plant material. However, none of the dosed goats developed the disease. The results demonstrate for the first time that white snakeroot is a potent myotoxin in goats and that other compound(s), which may be lost or modified during the extraction process, could be involved in causing trembles and milk sickness.

Evaluation of drying methods and toxicity of rayless goldenrod ( Isocoma pluriflora ) and white snakeroot ( Ageratina altissima ) in goats

White snakeroot and rayless goldenrod cause "trembles" and "milk sickness" in livestock and humans, respectively. The toxin in white snakeroot and rayless goldenrod was identified in 1927 and 1930, respectively, as tremetol. It was reported that the toxin in white snakeroot disappears as it is dried and that completely dried plants were incapable of producing trembles or milk sickness. Conversely, it has been reported that the rayless goldenrod toxin was not destroyed by drying and that the plant is toxic either fresh or dry. In this study the concentrations of tremetone, dehydrotremetone, and structurally similar compounds were determined in white snakeroot and rayless goldenrod before and after various drying conditions. Tremetone, dehydrotremetone, and structurally similar compounds in rayless goldenrod and white snakeroot are most stable upon freeze-drying, followed by air-drying, and least stable upon oven-drying (60 °C). Also demonstrated is that tremetone is stable and that dried white snakeroot and rayless goldenrod are capable of inducing toxicosis in livestock.

Distribution of ibogaine and noribogaine in a man following a poisoning involving root bark of the Tabernanthe iboga shrub

In the present paper, we report for the first time the tissue distribution of ibogaine and noribogaine, the main metabolite of ibogaine, in a 48-year-old Caucasian male, with a history of drug abuse, found dead at his home after a poisoning involving the ingestion of root bark from the shrub Tabernanthe iboga. Ibogaine and noribogaine were quantified in tissues and fluids using a fully validated liquid chromatography-electrospray mass spectrometry method. Apart from cardiac tissue, ibogaine and noribogaine were identified in all matrices investigated. The highest concentrations were found in spleen, liver, brain, and lung. The tissue/subclavian blood concentration ratios averaged 1.78, 3.75, 1.16, and 4.64 for ibogaine and 0.83, 2.43, 0.90, and 2.69 for noribogaine for spleen, liver, brain, and lung, respectively. Very low concentrations of the two drugs were found in the prostatic tissue. Both ibogaine and noribogaine are secreted in the bile and cross the blood-brain barrier. Four other compounds were detected in most of the studied matrices. One of them was identified as ibogamine. Unfortunately, we were not able to positively identify the other three compounds because of the unavailability of reference substances. Two of them could possibly be attributed to the following oxidation products: iboluteine and desmethoxyiboluteine. The third compound could be ibogaline.

Testing for atropine and scopolamine in hair by LC-MS-MS after Datura inoxia abuse

Datura inoxia belongs to the family of Solanaceae. This is a very common plant in New Caledonia that contains two main toxic alkaloids, l-atropine and l-scopolamine. In this study, we report the case of a 20-year-old male admitted to an Emergency Unit after consumption of 6 dried flowers in hot water for hallucinations, mydriasis, and agitation associated with tachycardia and increase of systolic blood pressure to 180. Full recovery was observed after one week. Three weeks later, a lock of about 80 hairs (200 mg) was collected from the subject in vertex posterior with scissors to be tested for both atropine and scopolamine. After decontamination with dichloromethane, a strand of hair was segmented into three parts, cut into small segments (< 1 mm), incubated overnight in 1 mL pH 8.4 phosphate buffer in the presence of 2.5 ng atropine-d(3), the internal standard, then extracted with 5 mL dichloromethane/isopropanol/n-heptane (50:17:33). The residue was reconstituted in 100 microL of methanol, from which 10 microL was injected into an XTerra MS C18 column (100 x 2.1 mm, 3.5 microm) eluted with a gradient of acetonitrile and formate buffer delivered at a flow rate of 0.2 mL/min. A Quattro Micro triple-quadrupole mass spectrometer (MS) was used for analyses. Ionization was achieved using electrospray in the positive ionization mode. For each compound, detection was related to two daughter ions (atropine: m/z 290.2 to 124.0 and 92.9; atropine-d(3): m/z 293.1 to 127.0 and 92.9; scopolamine: m/z 304.1 to 138.0 and 156.0). Although atropine was never detected (limit of detection = 2 pg/mg), scopolamine was identified in the three segments, in the range 14 to 48 pg/mg. The absence of atropine in hair is consistent with its very low dosage in the flower of Datura inoxia. Hair segmentation indicated that the subject was previously exposed on several occasions to the plant. Liquid chromatography-tandem MS appears to be a necessity for testing tropane alkaloids of the Datura group, given the low concentrations to be measured.

BMAA selectively injures motor neurons via AMPA/kainate receptor activation

The toxin beta-methylamino-l-alanine (BMAA) has been proposed to contribute to amyotrophic lateral sclerosis-Parkinsonism Dementia Complex of Guam (ALS/PDC) based on its ability to induce a similar disease phenotype in primates and its presence in cycad seeds, which constituted a dietary item in afflicted populations. Concerns about the apparent low potency of this toxin in relation to estimated levels of human ingestion led to a slowing of BMAA research. However, recent reports identifying potential new routes of exposure compel a re-examination of the BMAA/cycad hypothesis. BMAA was found to induce selective motor neuron (MN) loss in dissociated mixed spinal cord cultures at concentrations ( approximately 30 muM) significantly lower than those previously found to induce widespread neuronal degeneration. The glutamate receptor antagonist NBQX prevented BMAA-induced death, implicating excitotoxic activation of AMPA/kainate receptors. Using microfluorimetric techniques, we further found that BMAA induced preferential [Ca(2+)](i) rises and selective reactive oxygen species (ROS) generation in MNs with minimal effect on other spinal neurons. Cycad seed extracts also triggered preferential AMPA/kainate-receptor-dependent MN injury, consistent with the idea that BMAA is a crucial toxic component in this plant. Present findings support the hypothesis that BMAA may contribute to the selective MN loss in ALS/PDC.

Toxicokinetic profile of swainsonine following exposure to locoweed(Oxytropis sericea)in naïve and previously-exposed sheep

AIM

To determine the toxicokinetic profiles of swainsonine (SW) in sheep previously (subacute) and not previously (acute) exposed to locoweed.

METHODS

Twenty-nine wethers were stratified by bodyweight (BW; 68.0 (SE 7.6) kg) and randomly assigned to one of six treatments. Treatments were: 0 (n=5), 0.4 (n=5), and 1.6 (n=5) mg SW/kg BW for Trial 1, and 0 (n=4), 0.2 (n=5), and 0.8 (n=5) mg SW/kg BW for Trial 2. Acute exposure in both trials included adaptation to blue grama (Bouteloua gracilis) hay for 14 days and no previous exposure to locoweed (i.e. SW), followed by administration of a single oral dose of SW prepared from an extract of locoweed, in the doses described above. Subacute exposure comprised ingestion of a blue grama and locoweed (428 microg SW/g locoweed) diet for 21 days in Trial 1 and 28 days in Trial 2, followed by removal from locoweed for 5 days, then an oral dose of SW, as above. Quantities of locoweed fed in the diet were adjusted to achieve the dose rates specified for each treatment. Blood samples were collected via jugular venepuncture twice daily for 3 days prior to initial exposure to SW and then every 7 days for the duration of the trials, to monitor serum alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) activities. For intensive sampling periods, SW was administered immediately following blood sampling at 0 h, and blood samples were collected at hourly intervals from 0-12 h, 3-h intervals from 15-24 h, 6-h intervals from 30-48 h, and 12-h intervals from 60-168 h. Concentrations of SW in serum and locoweed extract were determined using the alpha-mannosidase inhibition assay (detection limit=25 ng/ml). Rates of absorption and elimination of SW from serum were calculated for each animal, using exponential curve fits of the concentration of SW in serum concentration vs time plots.

RESULTS

In both trials, SW was detected in serum in all animals exposed to locoweed. Elevated (p<0.05) serum Alk-P and AST activities indicated that subclinical SW intoxication was induced during the subacute exposure phase. Calculated rates of elimination were faster (p<0.001) for the 1.6 vs 0.4 (Trial 1) and 0.8 vs 0.2 (Trial 2) mg SW/kg BW doses. Rates of elimination indicated that, in both trials, SW was removed from serum faster (p<0.06) following acute exposure than subacute exposure. Higher exposure rates to SW resulted in higher concentrations of SW in serum within a trial.

CONCLUSIONS

Multiple compartments were involved in the kinetics of SW, and dose and previous exposure altered the toxicokinetics of SW. CLININCAL RELEVANCE: Should the true elimination half-life prove to be as high or higher than the 95 h demonstrated for the treatment using 0.4 mg SW/kg BW in Trial 1, then withdrawal periods for clearing SW from sheep should be >40 days (assuming 10 half-lives to clear the compound).

Clearance of para-aminohippuric acid in wethers consuming locoweed

AIM

To validate the use of para-aminohippuric acid (PAH) as a marker for measuring blood flow in wethers consuming a mixed diet of locoweed and blue grama hay.

METHODS

Fourteen sheep, stratified by bodyweight (BW), were assigned to one of three treatments: 0.8 mg swainsonine (SW)/kg BW (HI), 0.2 mg SW/kg BW (LO), and no SW (Control). Sheep were fed various ratios of locoweed and blue grama hay to deliver SW treatments, for 28 days prior to infusion of PAH. Concentrations of SW and activities of alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) in serum were measured to confirm exposure to SW and subclinical intoxication. A single 20-ml injection of 5% PAH was delivered into the jugular vein after subclinical intoxication had been achieved. Blood samples were collected and serum analysed for PAH immediately prior to injection, then every 5 min from 5-30 min, and every 10 min from 30-60 min, following injection of PAH.

RESULTS

Effective delivery of SW was evident from the greater concentrations of SW measured in the serum of HI compared with LO animals (p<0.05). No significant differences were detected in the rate of elimination (range 0.097-0.108 L/min), elimination half-life (range 6.62-7.24 min), apparent volume of distribution for the central compartment (range 7.14-9.72 L), and clearance (range 0.73-0.92 L/min) of PAH, between treatments.

CONCLUSIONS

Subclinical intoxication with SW did not affect the pharmacokinetics of PAH. Thus, use of downstream dilution of PAH is a valid method to determine the rate of blood flow in nutrient flux experiments that involve consumption of locoweed.

Synaptophysin: an Immunohistochemical Marker for Animal Dysautonomias

Equine and feline dysautonomias are characterized histopathologically by degenerating neurons with chromatolysis, pyknotic and sometimes eccentric nuclei, and loss of Nissl substance in the peripheral autonomic ganglia. Because it may be difficult to distinguish pathological from post-mortem changes in affected ganglia by histopathological examination, synaptophysin was evaluated as an immunohistochemical marker. Degenerating neurons showed strong intracytoplasmic labelling indicating abnormal accumulation of synaptophysin. It was concluded that synaptophysin immunohistochemistry is a helpful tool for detecting degenerating neurons in equine (grass sickness) and feline (Key-Gaskell syndrome) dysautonomias.

Pyrrolizidine Alkaloids—Genotoxicity, Metabolism Enzymes, Metabolic Activation, and Mechanisms

Pyrrolizidine alkaloid-containing plants are widely distributed in the world and are probably the most common poisonous plants affecting livestock, wildlife, and humans. Because of their abundance and potent toxicities, the mechanisms by which pyrrolizidine alkaloids induce genotoxicities, particularly carcinogenicity, were extensively studied for several decades but not exclusively elucidated until recently. To date, the pyrrolizidine alkaloid-induced genotoxicities were revealed to be elicited by the hepatic metabolism of these naturally occurring toxins. In this review, we present updated information on the metabolism, metabolizing enzymes, and the mechanisms by which pyrrolizidine alkaloids exert genotoxicity and tumorigenicity.

Symmetric focal degeneration in the cerebellar and vestibular nuclei in swine caused by ingestion of Aeschynomene indica seeds

A vestibulocerebellar disorder was observed in 2- to 4-month-old swine after consumption of broken rice contaminated with 13% Aeschynomene indica seeds. Affected animals recovered in 2-14 days after removal of the contaminated food. To reproduce the syndrome, 10 pigs were fed 13% A. indica seeds in commercial pig ration or rice. They showed clinical signs similar to those observed in the spontaneous cases, 1 hour to 6 days after ingestion. Three pigs recovered after the withdrawal of the contaminated food. The others were killed. Two pigs that were fed for 25 days with food containing 3% and 6% seeds and two control pigs did not show clinical signs. Histologic lesions were characterized by symmetric focal degeneration in the cerebellar and vestibular nuclei. The initial lesion, observed 24 hours after the first ingestion, was characterized by vacuolation of the neuropil. Subsequently, there was progressive loss of parenchyma, vascular reaction, a few small spheroids, astrocytosis, and accumulation of gitter cells. The brains from four pigs were perfused with a buffered solution of glutaraldehyde-paraformaldehyde 12-48 hours after they started to ingest the seeds. No ultrastructural lesions were observed in the cerebellar nuclei after 12 hours of seed consumption. At 24 hours, endothelial cells and pericytes were separated by empty spaces from astrocyte foot processes, suggesting perivascular edema. The astrocytes were enlarged, consistent with intracellular fluid accumulation. These results suggest that A. indica seeds are toxic, causing functional derangement of the vestibulocerebellar system, followed by alterations in the microvasculature in the cerebellar and vestibular nuclei.

Appearance and disappearance of swainsonine in serum and milk of lactating ruminants with nursing young following a single dose exposure to swainsonine (locoweed; Oxytropis sericea)

A series of experiments were conducted to investigate the elimination of swainsonine in the milk of lactating ruminants following a single dose oral exposure to swainsonine (locoweed; Oxytropis sericea) and to assess subsequent subclinical effects on the mothers and their nursing young. In a preliminary experiment, lactating ewes were gavaged with locoweed providing 0.8 mg swainsonine/kg BW (n = 4; BW = 75.8 +/- 3.6 kg; lactation = d 45) and lactating cows were offered up to 2.0 mg swainsonine/kg BW free choice (n = 16; BW = 389.6 +/- 20.9 kg; lactation = d 90). Serum and milk were collected at h 0 (before treatment), 3, 6, 12, and 24 for ewes, and h 0 (before treatment), 6, 12, 18, and 24 for cows. Swainsonine was highest (P < 0.05) by h 6 in the serum and milk of ewes. Consumption of at least 0.61 mg swainsonine/kg BW induced consistent (> 0.025 microg/mL) appearance of swainsonine in cow serum and milk. In response to the results obtained in the preliminary experiment, a subsequent experiment utilizing lactating ewes (n = 13; BW = 74.8 +/- 6.4 kg; lactation = d 30) and cows (n = 13; BW = 460.8 +/- 51.9 kg; lactation = d 90) was conducted. Each lactating ruminant was gavaged with a locoweed extract to provide 0 (control), 0.2, or 0.8 mg swainsonine/kg BW and individually penned with her nursing young. Serum and milk from the mothers and serum from the nursing young were collected at h 0 (before treatment), 3, 6, 9, 12, 24 and 48 (an additional sample was obtained at h 72 for ewes and lambs). Serum and milk swainsonine was higher (P < 0.05) in the 0.8 mg treated groups and maximal (P < 0.05) concentrations occurred from h 3 to 6 for ewes and h 6 to 12 h for cows (P < 0.05). Rises in alkaline phosphatase activity indicated subclinical toxicity in the treated ewes (P < 0.05). Following a single dose oral exposure to 0.2 and 0.8 mg swainsonine/kg BW provided by a locoweed extract, swainsonine was detected in the serum and milk of lactating ewes and cows, and rises in serum alkaline phosphatase activity were observed in the ewes. Neither swainsonine nor changes in alkaline phosphatase activity was detected in the serum of the lambs and calves nursing the ewes and cows dosed with swainsonine.

Interplant alkaloid variation and Senecio vernalis toxicity in cattle

Senecio vernalis and other plants containing pyrrolizidine alkaloids (PA) are implicated in the poisoning of cattle. The liver is a known target organ. In this study the content of the alkaloids senecionine (SCO), senkirkin (SKK) and seneciphyllin (SCP) and their toxic effects in cattle were studied. The content of these 3 compounds only varied by a factor of 2 within 10 plant collections at different locations in western Denmark (Jutland). However, individual alkaloids varied 3-fold, and the interplant variation for some of the PA up to 8-fold. SCO and SKK had very short half lives, 20 min and 70 min respectively. In cattle fed dried plant material corresponding to 200 and 400 g of fresh material for 10 d alanine aminotransferase, alkaline phosphatase and g-glutamyl transferase activities remained unchanged. Cattle subsequently fed fresh plant material up to 1 kg/d for 8 d also had no change in liver enzyme activities. Cattle did not show any clinical signs of poisoning, and no morphological liver changes were observed.

The effect of zinc supplementation on antioxidant and lipid peroxidation status during Brachiaria decumbens intoxication in sheep

An attempt was made to clarify the association between zinc (Zn) and antioxidants due to Zn supplementation on lipid peroxidation occurring during Brachiaria decumbens intoxication. The concentration of Zn, copper, malondialdehyde (MDA), superoxide dismutase (SOD), and gluthathione peroxidase (GSH-Px) were determined in tissues. There was a gradual increment in the concentration of Zn and MDA in serum and hepatocytic SOD in groups given Zn + B decumbens. A decline in erythrocytic GSH-Px and SOD, and lower concentration of reduced glutathione in hepatocyte cytosols were also detected in these sheep. It is highly suggestive that Zn supplementation may depress antioxidant status and enhance lipid peroxidation during B decumbens intoxication.

Rare Jatropha multifida intoxication in two children

Two children were admitted to the Emergency Department (ED) after ingesting a large amount of fruit of a plant identified as Jatropha multifida. They were mildly obtunded, had intractable vomiting, and seemed dehydrated. Intravenous fluid replacement and urine alkalinization were initiated. After stabilization, their 5-day hospital stays were uneventful except for a subclinical rise of liver enzymes. Jatropha species contain the toxalbumin ricin, which causes severe vomiting and diarrhea, dehydration, shock, and renal and hepatic impairment. Ricin also has cardiotoxic and hemolytic effects and several deaths have been documented. Children are attracted by the shape and the color of the Jatropha fruits. Mortality can be prevented by immediate fluid and electrolyte replacement.

Tissue swainsonine clearance in sheep chronically poisoned with locoweed (Oxytropis sericea)

Locoweed poisoning is seen throughout the world and annually costs the livestock industry millions of dollars. Swainsonine inhibits lysosomal alpha-mannosidase and Golgi mannosidase II. Poisoned animals are lethargic, anorexic, emaciated, and have neurologic signs that range from subtle apprehension to seizures. Swainsonine is water-soluble, rapidly absorbed, and likely to be widely distributed in the tissues of poisoned animals. The purpose of this study was to quantify swainsonine in tissues of locoweed-poisoned sheep and determine the rate of swainsonine clearance from animal tissues. Twenty-four crossbred wethers were gavaged with ground Oxytropis sericea to obtain swainsonine doses of 1 mg swainsonine x kg(-1) BW x d(-1) for 30 d. After dosing, the sheep were killed on d 0, 1, 2, 3, 4, 6, 14, 30, 60, and 160. Animal weights and feed consumption were monitored. Serum was collected during dosing and withdrawal periods, and tissues were collected at necropsy. Serum swainsonine concentrations were determined using an alpha-mannosidase inhibition assay. Swainsonine concentrations in skeletal muscle, heart, brain, and serum were similar at approximately 250 ng/g. Clearance from these tissues was also similar, with half-lives (T(1/2)) of less than 20 h. Swainsonine at more than 2,000 ng/g, was detected in the liver, spleen, kidney, and pancreas. Clearance from liver, kidney, and pancreas was about T(1/2) 60 h. These findings imply that poisoned sheep have significant tissue swainsonine concentrations and animals exposed to locoweed should be withheld from slaughter for at least 25 d (10 T(1/2)) to ensure that the locoweed toxin has cleared from animal tissues and products.

Effects of previous grazing treatment and consumption of locoweed on liver mineral concentrations in beef steers

Twelve Hereford steers (average BW = 231 kg) that had previously grazed native rangeland (Range) or irrigated winter wheat pasture (Wheat) were allowed to graze locoweed-infested rangeland from April 1 to June 9, 1994 (six steers/previous grazing treatment). Relative consumption level of locoweed and other forage classes was measured as observed bites per steer. Liver biopsy and whole blood samples were obtained from each steer before and after grazing. Liver samples were analyzed for several minerals by inductively coupled plasma-atomic emission spectroscopy, and whole blood samples were analyzed for Se. Liver concentrations of Ba (P < .001), Cd (P < .001), Ca (P < .01), Cr (P < .01), Ni (P < .001), Na (P < .01), and V (P < .001) were greater and concentrations of Mn (P < .09), P (P < .01), and K (P < .07) were less in Wheat than in Range steers. Liver concentrations of Fe, Mg, S, and Zn and whole blood Se concentrations did not differ (P > .10) between the two groups. Liver concentrations of Cr (P < .04) and Mn (P < .001) were less, and Fe concentrations were greater (P < .01), in samples taken after grazing than in samples taken before grazing of locoweed-infested range. Whole blood Se concentrations decreased (P < .01) from the beginning to the end of the grazing period, but this effect was not related (P > .15) to locoweed consumption. Changes in liver concentrations of minerals were compared relative to consumption levels of all forage classes in the locoweed-infested range. Liver concentrations of Cu decreased (r2 = .45; P < .02) as the percentage of bites consumed as locoweed increased, but concentrations after grazing locoweed-infested range were still within normal ranges. Changes in liver concentrations of other minerals were not related (P > .15) to consumption of locoweed. These data indicate that previous grazing history can have significant effects on liver mineral stores and that, under our conditions, consumption of locoweed by grazing beef steers altered liver Cu concentrations. Toxic effects of locoweed consumption would likely occur before Cu deficiency would be induced by grazing locoweed-infested range; hence, supplementation of Cu would seem unlikely to alter the course of locoweed toxicosis.

Tissue and serum swainsonine concentrations in sheep ingesting Astragalus lentiginosus (locoweed)

Locoweed intoxication or locoism results when animals continuously graze certain plants of the general Astragalus or Oxytropis. The locoweed toxin, swainsonine, is water soluble and is rapidly absorbed and eliminated. The purpose of this study was to determine the distribution of swainsonine in tissues of sheep eating locoweed and to determine if the tissue swainsonine concentrations change with continued locoweed ingestion. Fifteen cross-breed whethers were divided into 3 groups of 5 each and fed alfalfa pellets (Group 1) or alfalfa pellets with 10% Astragalus lentiginosus for 13 d (Group 2) or for 21 d (Group 3). After the feeding periods, the animals were slaughtered and tissues were collected, frozen and later analyzed for swainsonine using an in vitro, alpha-mannosidase inhibition assay. Significant alpha-mannosidase inhibitory activity (interpreted as ng/ml of swainsonine) was detected in whole blood, skeletal muscle, brain, kidney, liver, thyroid and urine. The swainsonine concentrations in tissues were significantly correlated with daily swainsonine intake (r = 0.58 to 0.96). With the exception of kidney, longer exposure did not result in significant increases in the swainsonine concentrations in blood, muscle, brain, liver or thyroid. Liver had the highest swainsonine concentrations with 3049 +/- 1952 and 3947 +/- 457 ng/ml (mean +/- SD) in Groups 2 and 3 respectively. Swainsonine concentrations varied widely within the groups suggesting individual animal variability in swainsonine absorption, metabolism and excretion. These findings suggest that swainsonine is present in tissues of animals eating locoweed and that in most tissues the amount was directly correlated to the swainsonine dose ingested, but not to the length of exposure.

The effects of fescue toxicosis on beef cattle productivity

Consumption of tall fescue forage infested with the endophytic fungus Acremonium coenophialum can result in a condition termed "fescue toxicosis," which is characterized by decreased weight gains, milk production, conception, and serum prolactin and an inability to dissipate body heat by beef cattle. These decreases in productivity have been estimated to cost beef producers more than $600 million annually. The unthrifty appearance of cattle consuming endophyte-infected tall fescue (E+) is most evident during periods of environmental heat or cold stress, suggesting an interaction with environmental conditions. Without temperature stress, cows consumed similar amounts of E+ and endophyte-free tall fescue (E-). But, when temperatures exceeded 32 degrees C, cows that grazed E+ consumed less forage than cows that grazed E-. After removal of E+ from the diet of steers, compensatory growth was observed, indicating no long-term negative effects of E+. A decrease in serum prolactin but apparently little change in other hormones has been measured after consumption of E+. Under periods of heat stress, animals had reduced ability to dissipate body heat, and blood flow to peripheral (rib skin), core-body (duodenum colon), and brain (cerebellum) tissues was decreased. Due to the depressive effects of E+ on prolactin and heat dissipation, dopamine antagonist therapy has been used in an attempt to rectify these changes. Dopamine antagonists have increased serum prolactin but there is limited evidence to suggest an improvement in heat dissipation. Experiments to elucidate the effects of E+ on alpha-1 and -2 adrenergic receptors may also offer insights into developing strategies to overcome the negative effects of E+ consumption. Preliminary results suggest that injections of an alpha-1 adrenergic antagonist (prazosin) in rats fed E+ under 32 degrees C conditions increased DM intake and reduced rectal temperature.

Endocrine responses in cows fed Ponderosa pine needles and the effects of stress, corpus luteum regression, progestin, and ketoprofen

Pregnant cows were fed pine needles (PN, 2 kg.cow-1.d-1) mixed with the diet to determine factors that affect abortion response. In Exp. 1, treatments were used to determine the effects of experimental stress and pelleting of pine needles. Pelleting needles and experimental stress delayed abortion response (P < .01). Stress-induced delay was associated with abnormal patterns of progesterone and cortisol (P < .01). In Exp. 2A and 2B, the role of the corpus luteum (CL) in abortion response to PN consumption was investigated by regressing the CL with prostaglandin F2 alpha. Regression of the CL and PN feeding reduced interval to parturition, but the effect of PN feeding was less when the CL was regressed (PN x CL, P < .01). The progesterone increase in response to experimental stress was decreased by CL regression (P < .01). In Exp. 3, melengestrol acetate (MGA) was fed (0, 2, or 4 mg.cow-1.d-1) in addition to PN. Parturition was blocked more effectively as dose of MGA increased (P = .075), but only parturition was blocked rather than the effects of PN. In Exp. 4, CL regression was blocked by feeding ketoprofen. Ketoprofen delayed response to PN, but the effect was only temporary (P < .01). Our conclusions are that 1) experimental stress delays abortion response to PN by increased concentrations of progesterone, 2) pelleting PN decreases their abortifacient activity, and 3) abortions caused by PN can be blocked by feeding a progestin or a prostaglandin inhibitor, but these compounds do not block the primary abortifacient effects of PN.

In vitro ruminal metabolism of larkspur alkaloids

Larkspur (Delphinium sp) poisoning of range cattle is a serious, recurring problem in the western United States. Numerous stratagems have been recommended to ameliorate larkspur intoxication, but none are completely effective. Previous studies in this laboratory indicated bovine ruminal microflora are capable of chemically modifying Delphinium alkaloids. Research reported herein was undertaken to further evaluate whether differences in ovine and bovine rumen metabolism might explain differences in susceptibility to larkspur intoxication and whether existing metabolic activity can be enhanced by sustained exposure to Delphinium alkaloids. Comparison of ovine and bovine rumen metabolism of Delphinium geyeri alkaloids in vitro failed to demonstrate differences in the rate of alkaloid metabolism. Rumen liquor collected sequentially from a fistulated cow dosed with dried Delphinium geyeri did not vary in ability to metabolize larkspur alkaloids.

Neuropathological effects and deaths of cattle and sheep in Argentina from Phalaris angusta

Neuropathological disorders and mortality occurred in cattle and sheep grazing P angusta. This native plant of South America is frequently found as a good quality component of natural pastures. Cattle and sheep feeding in pastures where P angusta was dominant started dying or showing signs 3 to 5 d after rain-falls started following a period of drought. Some animals died suddenly, while others nervous effects( incoordination, inability to walk normal, recumbency) and death for up to 2 w after the beginning of the signs. Postmortem findings were bilaterally symmetrical, greenish pigmented areas in the grey matter of the brain stem and diencephalon. A greenish tinge was also noted between the cortex and the medulla of the kidneys. Granules of a brown pigment were noted within the cytoplasm of neurons. An alkaloid substance was detected in the plant. Morbidity was 2.3 to 10.5% in herds B and A, and 0 to 3.4% in flocks D and C, respectively. Mortality was 0.8 to 1.0% in herds B and C, and 3.4 to 11.7% in flocks D and C, respectively. P angusta behaves, in terms of toxicity, as other Phalaris spp. Its widespread distribution in areas of extensive grazing poses a threat to cattle and sheep production in Argentina.

Altered metabolic hormones, impaired nitrogen retention, and hepatotoxicosis in lambs fed Kochia scoparia hay

Livestock grazing lush Kochia scoparia (L.) Schrad, sometimes experience BW loss, hyperbilirubinemia, photosensitization, and polyuria. Animals fed kochia hay may exhibit milder or negligible signs of toxicosis but fail to utilize nutrients efficiently. To characterize early aspects of kochia toxicosis and to evaluate prospective treatments, 12 wether lambs (34 +/- 3 kg) were fed prebloom kochia hay (83% OM, 15% CP, and 6.3% total oxalate) and treated as follows: 1) no treatment; 2) drenched daily with aqueous ZnSO4 to provide 30 mg of Zn/kg of BW); 3) injected i.p. twice weekly with N-acetyl-L-cysteine (CYS) in saline (21 mg/kg of BW) plus trans-stilbene oxide (TSO) in corn oil (27 mg/kg of BW); and 4) treated as 2) plus 3). Treatments were imposed factorially (2 x 2) with three lambs per treatment. Kochia intake (ad libitum) averaged .57 kg/d (1.7% of BW) for 80 d, and digestibility of DM and CP were 44 and 59%, respectively, at wk 4, but BW loss was severe (6 to 11 kg/lamb). After 14 d, serum insulin and prolactin were decreased (P less than .05) below initial values (.48 to .11 and 102 to 28 ng/ml, respectively). Serum somatotropin increased (P less than .05) from 4.5 to 6.8 ng/ml at 4 wk. Serum total bilirubin increased threefold at 3 wk (P less than .05) and declined slightly thereafter through 10 wk. Early changes in serum enzymes reflected mild hepatotoxicosis without cholestasis, whereas histopathology (at 80 d) showed diffuse hepatocyte swelling and nephrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum constituents and metabolic hormones in sheep and cattle fed Kochia scoparia hay

Kochia scoparia (L.) Schrad. is a prospective forage crop for arid areas, although its potential value is constrained by occasional toxicity that may involve alteration of metabolic hormones. The present research compared serum clinical profiles and metabolic hormone concentrations in steers and wethers fed kochia hay (85% OM, 13% CP, 45% ADF, and 6.3% total oxalate) to those of suitable controls that were pair-fed equal amounts of DM as alfalfa hay (91% OM, 13% CP and 42% ADF). Eight steers (240 +/- 2 kg BW) that were pair-fed kochia or alfalfa hay for 21 d had similar levels of serum insulin (INS) or somatotropin (GH), but kochia lowered prolactin (PRL) (6.0 vs 118 ng/ml; P = .14). Kochia hay did not elevate serum bilirubin at d 21 in these steers; however, lactic dehydrogenase and aspartate aminotransferase activities were elevated 1.3-fold (P less than .05). Ten fine-wool wethers (29 +/- kg BW) pair-fed kochia or alfalfa hay for 21 d had similar levels of PRL and INS at d 0, 5, 10, and 21; however, GH was lower in wethers fed kochia at d 5 (P less than .05) and somewhat lower at d 10 and 21. Kochia elevated serum unconjugated bilirubin 1.25-fold over pair-fed controls (P = .06) and increased (P less than .05) activities of aspartate and alanine aminotransferases. Metabolic hormone responses to kochia hay differed in steers vs wethers during undemutrition and mild toxicosis that occurred within 3 wk.

Toxicosis in pigs fed selenium-accumulating Astragalus plant species or sodium selenate

Three groups of 5 pigs each were fed a high selenium (Se) diet by mixing either Astragalus praelongus (31.6 ppm Se in feed), A bisulcatus (31.7 ppm Se in feed), or sodium selenate (26.6 ppm Se in feed) with commercial hog feed. Ten control pigs were fed only commercial hog chow containing trace selenium (0.44 ppm Se). Pigs were fed for 9 weeks and necropsied when they had ataxia or paralysis. Blood was collected for hematologic and serum biochemical determinations, and samples of various tissues were collected and fixed in neutral-buffered 10% formalin for histologic evaluation or frozen for determination of selenium concentration. All forms of selenium induced clinical signs of weight and hair loss, with cracked hooves and inflamed coronary bands developing in all Na2SeO4-fed pigs and 1 A praelongus-fed pig, but not in A bisulcatus-fed pigs. Serum calcium, phosphorus, and albumin concentrations were unchanged or significantly decreased from prefeeding values in groups fed selenium. Serum aspartate transaminase (AST) activities in Astragalus species-fed groups, and amylase activities and PCV in all groups of pigs fed selenium, were increased. Serum alkaline phosphatase and creatine kinase activities were significantly increased in the A praelongus-fed pigs and significantly decreased in Na2SeO4-fed pigs. Terminal tissue and body fluid selenium concentrations were determined in all groups of pigs fed selenium and compared with values in control pigs. Urine and bile concentrations were increased by the greatest factor (40 to 100x), with tissue concentrations of selenium increased by a lesser factor (6 to 17x).(ABSTRACT TRUNCATED AT 250 WORDS)

Signal grass (Brachiaria decumbens) toxicity in sheep: changes in motility and pH of reticulo-rumen

In addition to generalized icterus, enlargement of the liver and severe photosensitization, signal grass (Brachiaria decumbens) toxicity also caused ruminal stasis and a decreased rumen pH in sheep. Ruminal stasis, which occurred within 3 weeks of grazing on this grass, may be the effect of the toxin produced in the rumen rather than a sequele of a decreased rumen pH. Animals were anorexic and the volume of their rumen content was very much reduced.

Hypothesis: plant and fungal biocides, copper and Indian childhood liver disease

Hepatic copper accumulation is characteristic of Indian childhood cirrhosis (ICC) but in experimental animals causes only modest liver damage. Plant and fungal biocidal agents may be hepatotoxic, may increase hepatic copper concentration, and may be secreted in milk of lactating animals. Crotalaria species, Parthenium hysterophorus and Aspergillus flavus are possible contaminants of animal feeds in rural India, and we hypothesise that their products may be synergistic with copper in causing ICC.

A novel nigrostriatal dopaminergic disorder in sheep affected by Tribulus terrestris staggers

An investigation was carried out into the pathogenesis of a unique locomotory disorder of sheep. Thirty sheep which had exhibited clinical signs for more than 15 months were examined for the presence of muscle atrophy, limb paresis, and spontaneous rotational behaviour. A single large dose of levodopa was administered to 12 normal and 12 affected sheep, and the drug-related effects of sedation and excitation were monitored continuously for three hours. The striatum was removed from eight normal and eight affected sheep and assayed for dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC). The findings of asymmetrical atrophy of pelvic limb extensor muscles, asymmetrical paresis of the limbs, a left:right dominance ratio of 50:50, spontaneous rotational behaviour, decreased response to levodopa loading, and decreased levels of DA (19 per cent reduction) and DOPAC (30 per cent reduction) in the striatum of affected sheep, were interpreted as indicative of a primary nigrostriatal dopaminergic disorder. It is suggested that a striatal presynaptic receptor malfunction has occurred.

Oleandrin distribution in a fatality from rectal and oral Nerium oleander extract administration

In a fatal (cardiotoxic) case of oleander extract poisoning of a young female, ethanol extracts of blood and tissue homogenates were purified by lead acetate. After removal of excess lead by ammonium sulfate, oleandrin was extracted into chloroform. Oleandrin in the extract concentrates was detected by thin-layer chromatography, with location by fluorescence and chromogenically by means of p-anisaldehyde. Quantitation was performed on dried extracts reconstituted in water/methanol, reacted with hydrogen peroxide, ascorbic acid, and hydrochloric acid, and analyzed by fluorescence spectrophotometry. Excitation was at 355 nm, and fluorescence scanning from 340 to 580 nm. The fluorescence peak at 460 nm was used for the quantitative measurement. The concentrations of oleandrin measured in blood, stomach wall, colon tissue, liver, heart, lung, brain, spleen, and kidney ranged from 10 to 39 micrograms/g, with 200 micrograms/mL in the total gastric content residue submitted for analysis.

Effects of induced fescue toxicosis on plasma and tissue catecholamine concentrations in sheep

Sixteen crossbred wethers were distributed among four treatments and fed a control ration based on annual rye-orchardgrass (R-O) for 8 days. Indwelling jugular cannulae were installed and experimental regimes begun the following day (experimental day 1). One-half of the wethers were fed a ration based on endophyte-infected Kentucky-31 fescue while the remainder continued to receive the R-O control diet for 10 days. Spiperone, a dopamine antogonist, was administered to one-half of the wethers receiving each ration on days 8 and 9. Plasma prolactin (PRL), dopamine (DA), norepinephrine (NE) and epinephrine (E) were measured in jugular venous blood on days 1, 3, 5 and 7-10 of the trial. On day 10, the animals were decapitated; and DA, NE, E and 3,4-dihydroxyphenylacetic acid (DOPAC) and monoamine oxidase (MAO) were determined in hypothalamic and pituitary tissue. Plasma DA was elevated (P less than .05) following day 8 in wethers fed infected fescue over those fed (R-O), while plasma PRL was reduced (P = .08). Wethers receiving Spiperone had lowered (P less than .05) plasma DA and elevated (P less than .01) plasma PRL. Plasma DA was negatively correlated (P less than .01) with plasma PRL (r = -0.50) following day 8. Plasma NE and E levels and NE, E, DA and DOPAC tissue concentrations were not affected by Spiperone administration or diet. MAO levels in pituitaries were higher (P less than .01) for Spiperone-treated wethers. Wethers receiving the toxic fescue ration exhibited elevated plasma DA concentrations which was associated with depressed prolactin secretion in wethers.(ABSTRACT TRUNCATED AT 250 WORDS)

Paralysis and lipofuscin-like pigmentation of farm stock caused by the plant, Trachyandra laxa var. laxa

A paralytic condition of farm stock in South West Africa, characterized by prominent neuronal and some mild extraneuronal pigmentation, is described. The distribution of the pigment, which was mainly located in the larger neurones of the brain and spinal cord, is given. Experimental evidence, obtained by feeding the plant, is presented that the condition is caused by Trachyandra laxa var. laxa. The histochemical features of the pigment proved to be compatible with a lipofuscin.

Reduced progesterone and altered cotyledonary prostaglandin values induced by locoweed (Astragalus lentiginosus) in sheep

Feeding 300 or 400 g of dried spotted locoweed, Astragalus lentiginosus per day to 11 pregnant Columbia ewes from the 20th to the 50th days of their gestations resulted in dead and edematous fetuses. Aspartate aminotransferase values were increased, whereas serum progesterone values were significantly diminished (P less than 0.05) in a dose-dependent manner by locoweed ingestion. Cotyledonary 6-keto-prostaglandin (PG)F1 alpha (400 g/day only) and PGF2 alpha (300 and 400 g/day) values were significantly increased (P less than 0.05), whereas PGE values were not affected by the treatment. Alterations in PG values in these sheep may be a mechanism for altering corpus luteum function and inducing fetal death, which would ultimately result in abortion.

Identification of oenanthotoxin and related compounds in hemlock water dropwort poisoning

The case histories are presented of three separate incidents of poisoning by ingestion of Hemlock Water Dropwort tubers (Oenanthe crocata). Two of these cases involved a fatality. An analytical profile is provided for oenanthotoxin, the major toxic principal of the tubers. Chromatographic, spectroscopic and mass spectral data for related compounds are also given.

A suspected lipofuscin storage disease of sheep associated with ingestion of the plant, Trachyandra divaricata (Jacq.) Kunth

Paresis afflicted 85 out of a flock of 770 young Merino ewes kept on old wheat lands in the western Cape during a period of drought. Many of the paretic ewes died. The vegetation was sparse and was dominated by Trachyandra divaricata. At necropsy, yellowish-brown discoloration of the grey matter throughout the brain and spinal cord and mild brown discoloration of the liver, renal cortex and lymph nodes were consistently seen. Light microscopical examination revealed abundant, yellowish-brown pigment granules in the cytoplasm of most of the larger neurons. Similar pigment also occurred in some non-nervous tissues. Shrinkage and loss of a few randomly scattered axons were observed in the white matter of the spinal cord in 2 sheep. Histochemical and ultrastructural features of the pigment were consistent with those of lipofuscin. T. divaricata failed to reproduce the condition when dosed to a sheep, but the paresis and pigmentation shown to be caused by the closely related plant, T. laxa, are strikingly similar. Trachyandra poisoning appears to be the first documented example in farm animals of an acquired lipofuscin storage disease involving nervous and non-nervous tissues for which a specific plant has been causally implicated.

Effects of Crotalaria saltiana on Nubian goats

Ten Nubian goats were given daily oral doses ranging from 0.5 to 10 g/kg/day of the fresh shoots of Crotalaria saltiana; they died at various times after dosing. The main signs of Crotalaria poisoning were dullness, dyspnea, inappetence, loss of condition and arching of the back. An increase in the concentration of ammonia, in the activity of GOT, and a decrease in total protein, calcium and magnesium were detected in the serum. The main pathological changes were hemorrhages in the lungs, heart and spleen, focal catarrhal enteritis, hepatic portal fibrosis, dilatation of the renal tubules and straw-colored fluid in the peritoneal cavity.

Review of the biochemical effects of Lantana camara toxicity

Lantana intoxication of guinea pigs causes a decrease in liver dry weight, protein and DNA content while the amount of lipids in liver increases. Biochemical changes have been observed in liver mitochondria, lysosomes, microsomes, canalicular plasma membrane and cytosol of lantana-poisoned guinea pigs. There is cholesterol enrichment of mitochondria, microsomes and plasma membrane. Activities of oxidative enzymes of mitochondria or cytosol are elevated. On the other hand, activities of microsomal enzymes associated with drug metabolism are decreased. Similarly, activity of cytosol glutathione-S-transferase is significantly decreased. The out put of lipid peroxides by a number of tissues of lantana-affected guinea pigs decreases and can be attributed to enhanced activity of glutathione peroxidase and hyperbilirubinemia. There is leakage of lysosomal enzymes from the liver of lantana-intoxicated guinea pigs. Significant alterations have been observed in different blood constituents of lantana-affected animals. There is an increase in blood bilirubin (prominently in the conjugated form) hemoglobin, urea, and erythrocyte and leucocyte numbers. Erythrocytes of lantana-poisoned animals are more fragile to osmotic shock. Alterations in blood plasma enzyme activities are consistent with hepatic injury and cholestasis.

The effect of consumption of the pyrrolizidine alkaloid-containing plant Senecio jacobaea on iron and copper metabolism in the rat

The effect of dietary tansy ragwort (Senecio jacobaea), a pyrrolizidine alkaloid (PA)-containing plant, on mineral metabolism in rats was studied. In experiment 1, rats were fed a dietary level of 5% tansy ragwort. At intervals of 1, 2, 4, 6 and 8 weeks animals were killed and tissue mineral levels determined. As compared to comparable controls, rats fed tansy ragwort showed by 6 weeks elevated liver and spleen copper and iron levels. Experiment 2 was a 3 X 4 factorial experiment with added dietary copper levels of 0, 50 and 250 ppm, and tansy ragwort levels of 0, 1, 2.5 and 5%. Liver copper levels increased markedly with increasing levels of tansy ragwort; at 0, 50 and 250 ppm added copper, liver copper levels were 4, 18 and 21 times greater in rats fed 5% tansy ragwort as compared to those with no tansy ragwort. Increases in liver iron and spleen copper were noted with consumption of tansy ragwort. Higher liver copper levels were observed when a casein-based diet rather than a soybean meal diet was used, suggesting an effect of phytate in soybean meal in reducing copper absorption. In the last experiment, 59Fe was administered to rats fed diets with or without tansy ragwort. After 5 weeks on tansy ragwort, rats showed very low levels of 59Fe in erythrocytes, tibia and liver, and elevated levels in spleen and kidney, suggesting either an impairment of hematopoesis or accelerated erythrocyte destruction as a result of PA consumption. These results indicate that PA's cause increased liver copper content, and disturbances in iron metabolism.

The similar effects of swainsonine and locoweed on tissue glycosidases and oligosaccharides of the pig indicate that the alkaloid is the principal toxin responsible for the induction of locoism

A neurological condition resembling that observed in hereditary mannosidosis occurs in animals ingesting spotted locoweed and plants of the genus Swainsona. Swainsonine has been isolated from these plants and has been suggested to be the primary causative agent in inducing the pathological condition. This alkaloid has also been found to increase tissue acid alpha-D-mannosidase levels in rats while lowering liver Golgi mannosidase II levels. In the present study, the effects of locoweed and swainsonine were directly compared for the first time, with the pig as experimental animal. Both increased most lysosomal acid glycosidase activities in most tissues, decreased liver Golgi mannosidase II levels, increased plasma hydrolase levels, and greatly increased tissue oligosaccharide, especially Man5GlcNAc2 and Man4GlcNAc2. These results indicate that swainsonine is the agent in locoweed responsible for the enzymatic and oligosaccharide changes. The behavior of the animals was also similarly affected by swainsonine and locoweed.

Toxicity of threadleaf groundsel (Senecio douglasii var longilobus) to cattle

Threadleaf groundsel (Senecio douglasii var longilobus), a common plant on much of the rangeland of southwestern United States, was experimentally fed to 55 cattle by gastric gavage, mixed in alfalfa hay, or pelleted in feed. Since the pyrrolizidine alkaloid (PA) content of threadleaf groundsel fluctuates greatly, dosage was determined by the plant PA content. Animals that died survived up to 506 days. Whether they were acutely or chronically affected they had typical signs of seneciosis. Major gross and histopathologic changes are reported. The estimated minimum lethal plant dose by gavage was sufficient plant to provide 13 mg of PA/kg of calf body weight/day for 15 days or a total of approximately 200 mg of PA/kg in a 15-day period. Cattle that consumed up to 600 mg of PA/kg total in 20- to 100-day periods in hay or pellets were unaffected or minimally affected. These findings emphasize the importance of the time-dose relationship in PA toxicosis in cattle and indicate that there is a threshold level of PA that must be exceeded for the toxicosis to develop.

Wheat pasture poisoning. II. Tissue composition of cattle grazing cereal forages and related to tetany

Thirty-two aged Hereford and Angus cows (avg 10.2 yr old) grazed mixed cereal (wheat and rye) pastures from December 6, 1979 to April 23, 1980 (138 d). On d 104 (March 19), five cows developed tetany. On the day of tetany, the mean plasma Ca of the cows with tetany was 4.1 mg/dl. Cows with tetany had plasma Mg concentrations of 1.7 mg/dl on the day of tetany, but 15 d before tetany and 6 d post-tetany, levels were lower (1.2 mg/dl). Cows with tetany had large increases in plasma parathyroid hormone (PHT) as well as vitamin 1, 25 dihydroxy D3 [1,25(OH)2D], plasma glucose, lactic acid and beta-hydroxybutyric acid. Plasma K of these cows followed a similar trend as plant K, except it was not as pronounced. Plasma inorganic P of these same cows was exceedingly low, less than 3 mg/dl several times, although the forage P did not indicate a P deficiency. Levels of plasma hydroxyproline in these cows indicated that bone resorption may have been low during most of the grazing season, even though levels of plasma hydroxyproline were initially high and high subsequent to tetany. High levels of plasma glucose and lactic acid were associated with the time of tetany. Apparently, cows developed inappetence around the time of tetany, as suggested by the high levels of plasma beta-hydroxybutyric acid. Cows with wheat pasture poisoning appeared to respond to the severe hypocalcemia with large increases in plasma 1,25(OH)2D. Plasma 1,25(OH)2D changes were similar to plasma hydroxyproline changes (and possible bone resorption rates) and seemed inversely proportional to plasma Ca and directly proportional to plasma PTH concentrations. Generally, cerebrospinal fluid (CSF) composition was not affected as much as plasma composition, except for the low levels of CSF Ca. These data indicate that a metabolic deficiency of Ca (hypocalcemia) was the cause of tetany.

Effect of lantana on the composition of the extracellular fluid of sheep

Experiments were done to examine the effects of lantana poisoning on the composition of the extracellular fluid of sheep. Packed cell volume and total plasma protein increased after dosing with lantana and plasma osmolality increased markedly in the days prior to death. During the early stages of the disease plasma electrolytes were unchanged except for a decrease in potassium, but electrolyte levels varied late in the disease. A metabolic acidosis gradually developed as the disease progressed. It is concluded that fluid, electrolyte and acid-base imbalances are minor in the early stages of intoxication, but in the terminal stages of the disease, some major changes occur.

Changes in rumen contents associated with lantana poisoning of sheep

The effects of lantana poisoning on the microbial populations of the rumen and on fermentation within the rumen were compared to the effects of starvation in sheep. The protozoal and bacterial populations of the rumen were decreased to the same extent by lantana poisoning and starvation. Fermentation appeared to continue for several days in the rumen of lantana-poisoned animals, as shown by the concentrations of volatile fatty acids and ammonia, and the pH and rH of rumen fluid. It is suggested that this was due to retention of plant material in the static rumen of lantana-poisoned animals. It is concluded that lantana toxins do not affect rumen microorganisms directly and that the changes observed in lantana-poisoned animals are probably due to anorexia and rumen stasis.

Effect of Lantana camara toxicity on lipid peroxidation in guinea pig tissues

Lantana intoxication of guinea pig inhibited lipid peroxidation in different tissues in the order: adrenals greater than liver greater than kidneys greater than heart greater than lungs greater than testes greater than brain. The inhibitory factor(s) appear to be present in the postmitochondrial fraction. Lantadene A, the toxic principle of lantana plant caused just marginal inhibition of lipid peroxidation in guinea pig liver homogenates. Bilirubin and fraction "p', a partially purified toxin of Lantana camara are more potent inhibitors of lipid peroxide formation. Lantana toxicity did not affect ascorbic acid, phospholipid content and superoxide dismutase activity of guinea pig liver. The enzyme activity of glutathione peroxidase was significantly elevated.