Biomedical subjects

L F James

Publications and source records attributed to L F James.

At least 37 records · Page 2Linked to original sources

PubMed1998

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.

Animals↗

PubMed1998

Abortifacient effects of lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) on cattle.

Lodgepole pine (Pinus contorta) and common juniper (Juniperus communis) contain high levels of isocupressic acid that has been identified as the abortifacient component of ponderosa pine needles in cattle. Therefore, the abortifacient potential of P contorta and J communis needles was tested in feeding trials with pregnant cattle. Cows (2 groups of 2 each) were fed by gavage 4.5-5.5 kg/d ground dry needles from either P contorta or J communis starting on gestation day 250. Isocupressic acid (ICA) levels in P contorta needles and J communis plant material were 0.8 and 2.0% (dry weight) respectively. Cows fed P contorta received a daily dose of 62-78 mg ICA/kg body weight and aborted after 8 and 10 d. The 2 cows fed J communis received a daily dose of 190 and 245 mg ICA/kg body weight and aborted after 3 and 4 days respectively. All cows retained fetal membranes and had classical clinical signs of pine needle-induced abortion. Pinus ponderosa, P contorta, J communis, and Cupressus macrocarpa samples were also analyzed for the presence of myristate and laurate esters of 1,14-tetradecanediol and 1,12-dodecanediol. These lipid like compounds of P ponderosa have potent vasoconstrictive activity in a placentome perfusion assay and are proposed as possible abortifacients in cattle. Concentration of the vasoactive lipids were 0.028% (P ponderosa), 0.023% (P contorta), 0.001% (J communis), and none detected (C macrocarpa). It was concluded that these compounds are not required for the plant material to be abortifacient in cattle.

Abortifacient Agents↗

PubMed1996

The toxic and abortifacient effects of ponderosa pine.

Ponderosa pine needles cause abortion and a poorly described toxicosis when eaten by cattle. In previous trials, the abortifacient compound of pine needles was identified as isocupressic acid. At abortifacient doses, isocupressic acid caused no other toxicosis. However, other pine needle fractions, similar in composition to several commercially available rosin products, caused no abortion but were very toxic. The purpose of this study was to describe the toxicoses of ponderosa pine, compare its toxicity with other rosin and related pine products, and identify the toxin. Four groups of three pregnant beef cows each were treated with either ponderosa pine tips, rosin gum, dehydroabietic acid, or ground alfalfa. The cows treated with pine tips aborted, had retained placentas with endometritis, and developed both renal and neurologic lesions. The cattle treated with rosin gum or dehydroabietic acid did not abort but developed similar signs and lesions of intoxication. Clinical signs of intoxication included anorexia, mild rumen acidosis, dyspnea, paresis progressing to paralysis, and death. Clinical biochemical results, suggestive of renal, hepatic, and muscular disease, included azotemia, hypercreatinemia, hyperphosphatemia, proteinuria, and marked elevations of various serum enzymes. Histologically, all poisoned animals had nephrosis, vacuolation of basal ganglia neuropil with patchy perivascular and myelinic edema, and skeletal myonecrosis. The alfalfa-treated controls were normal. These findings suggest that ponderosa pine needles and tips are both abortifacient and toxic. Because the lesions caused by pine tips, rosin gum, and dehydroabietic acid are similar, toxicosis is most likely due to the diterpene abietane acids, common in all three.

Abietanes↗

PubMed1996

Pyrrole detection and the pathologic progression of Cynoglossum officinale (houndstongue) poisoning in horses.

Houndstongue (Cynoglossum officinale), a noxious weed that contains pyrrolizidine alkaloids (PAs), infests pastures and fields in the western United States and Europe. The purpose of this study was to develop techniques to better diagnose PA poisoning and describe the progression of gross and microscopic lesions caused by houndstongue intoxication. Six horses were gavaged daily with a suspension of houndstongue containing 5 or 15 mg/kg total PA for 14 days. Two horses were treated similarly with ground alfalfa as controls. Liver biopsy samples and serum biochemical and hematologic values were evaluated biweekly. Within 7 days after dosing, horses treated with 15 mg/kg PA developed severe liver disease characterized by altered bile acid metabolism, elevated serum enzymes, and extensive hepatocellular necrosis with minimal periportal fibrosis and biliary hyperplasia. The condition of these animals continued to deteriorate, and they were euthanized. For several weeks after dosing, horses treated with 5 mg/kg PA were depressed, had transient elevations of serum enzymes and bile acids, and developed minimal periportal hepatocellular necrosis with fibrosis. The biochemical changes resolved by 6-8 weeks; however, the histologic disease persisted with extensive megalocytosis by week 14. Throughout the study, the rate of hepatocellular proliferation remained constant. Biliary cells had an increase in mitotic rate that correlated with the histologic changes. Hepatic tissue-bound pyrroles (PA metabolites) were identified in necropsy samples of treated animals using gas chromatography/mass spectrometry and photometrically with Ehrlich's reagent. These findings suggest that pyrrole extraction and identification are useful in documenting PA exposure and that houndstongue is extremely toxic to horses.

Alkaloids↗

PubMed1996

Operant analysis of chronic locoweed intoxication in sheep.

Five sheep were fed a 10% locoweed (Oxytropis sericea) pellet or alfalfa pellets for 3- to 5-wk periods to determine the effects of intermittent locoweed ingestion on operant responding; three controls were fed alfalfa pellets for 22 wk. Sheep were trained to respond to a multiple schedule with a fixed ratio (FR) 5 and fixed interval (FI) 50 s as major elements; performance was reinforced with rolled barley. Locoweed-treated sheep decreased (P < .05) FR response rate after 4 wk of locoweed feeding, but this decrease first appeared during the first recovery period (wk 6). The FR response rate of intoxicated sheep did not return to baseline during the remainder of the study and differed from controls during most of the study. Controls did not deviate (P > .05) from their FR baseline except during wk 2. Sheep did not stabilize on the FI component. As locoweed-treated sheep became progressively more intoxicated, they altered their pattern of FR responses, with longer post-reinforcement pauses, and a slower overall FR rate. Intoxicated sheep ingested an average of .21 mg swainsonine.kg-1.d-1. Overt signs of intoxication were noted when two sheep were stressed on wk 17. These two sheep had neuroviseral vacuolation typical of locoweed poisoning, whereas the three remaining locoweed-treated sheep that were euthanatized 5 wk later showed little histologic evidence of intoxication. Our findings indicate that "on-off" or cyclic grazing of locoweed ranges should be approached cautiously. Such a grazing program may be feasible because of the rapid resolution of histologic pathology; however, an initial toxic insult of 4 wk seems to be excessive, even at low doses, because sheep may exhibit persistent behavioral abnormalities that require > 6 wk to resolve.

Animals↗

PubMed1996

Comparative toxicity of selenium from seleno-DL-methionine, sodium selenate, and Astragalus bisulcatus in pigs.

Selenium is an essential micronutrient, although ingestion in excess in pigs can cause disease conditions including neurological dysfunction and chronic skin and hoof lesions. Controlled feeding trials in growing swine, using the same Se content in feed sources, resulted in higher concentrations (p < or = 0.05) of Se in blood and organs of pigs fed seleno-DL-methionine compared with those receiving Astragalus bisulcatus or sodium selenate. Clinical signs of Se toxicity including neurological signs of paralysis were more severe and occurred sooner in the A. bisulcatus group than in the sodium selenate or seleno-DL-methionine groups. All five pigs fed A. bisulcatus developed neurological signs of paralysis, and in four the signs occurred within 5 days of the start of treatment. Four of five pigs fed sodium selenate also developed paralysis, but this occurred 4 to 21 days after treatment began. The fifth pig in the group developed signs of chronic selenosis. Two of five pigs fed seleno-DL-methionine developed paralysis on 9 and 24 days, respectively, and the remaining three developed chronic selenosis. Selenium fed to pigs in three forms [plant (A. bisulcatus), sodium selenate, or seleno-DL-methionine] resulted in neurological dysfunction and lesions of symmetrical poliomyelomalacia. These were most severe in the A. bisulcatus group, which also had polioencephalomalacia. Although seleno-DL-methionine caused the greater increase in tissue and blood Se concentrations, this did not correlate with severity of pathological changes, since animals fed A. bisulcatus developed more severe and disseminated lesions.

Animal Feed↗

PubMed1995

The lesions of locoweed (Astragalus mollissimus), swainsonine, and castanospermine in rats.

To better characterize and compare the toxicity of and lesions produced by locoweed (Astragalus mollissimus) with those of swainsonine and a related glycoside inhibitor, castanospermine, 55 Sprague-Dawley rats were randomly divided into 11 groups of five animals each. The first eight groups were dosed via subcutaneous osmotic minipumps with swainsonine at 0, 0.1, 0.7, 3.0, 7.4, or 14.9 mg/kg/day or with castanospermine at 12.4 or 143.6 mg/kg/day for 28 days. The last three groups were fed alfalfa or locoweed pellets with swainsonine doses of 0, 0.9, or 7.2 mg/kg/day for 28 days. Swainsonine- and locoweed-treated rats gained less weight, ate less, and showed more signs of nervousness than did controls. Histologically, these animals developed vacuolar degeneration of the renal tubular epithelium, the thyroid follicular cells, and the macrophage-phagocytic cells of the lymph nodes, spleen, lung, liver, and thymus. Some rats also developed vacuolation of neurons, ependyma, adrenal cortex, exocrine pancreas, myocardial epicytes, interstitial cells, and gastric parietal cells. No differences in lesion severity or distribution were detected between animals dosed with swainsonine and those dosed with locoweed. Rats dosed with castanospermine were clinically normal; however, they developed mild vacuolation of the renal tubular epithelium, the thyroid follicular epithelium, hepatocytes, and skeletal myocytes. Special stains and lectin histochemical evaluation showed that swainsonine- and castanospermine-induced vacuoles contained mannose-rich oligosaccharides. Castanospermine-induced vacuoles also contained glycogen. These results suggest that 1) swainsonine causes lesions similar to those caused by locoweed and is probably the primary locoweed toxin; 2) castanospermine at high doses causes vacuolar changes in the kidney and thyroid gland; and 3) castanospermine intoxication results in degenerative vacuolation of hepatocytes and skeletal myocytes, similar to genetic glycogenosis.

Animals↗

PubMed1995

Reproductive response of ewes fed alfalfa pellets containing sodium selenate or Astragalus bisulcatus as a selenium source.

Selenium fed to open cycling ewes in the form of sodium selenate or Astragalus bisulcatus (a selenium accumulator plant) at 24 or 29 ppm selenium, respectively, in alfalfa hay pellets did not alter the estrous cycle length, estrus behavior, progesterone or estrogen profiles, pregnancy rate or outcome of parturition (P > 0.05). There was wool loss in some ewes fed seleniferous pellets and the mean whole blood selenium levels were 0.45, 1.3 and 2.4 ppm, respectively, for control, A bisulcatus and sodium selenate; however, ewe condition and appearance remained good. All lambs appeared normal and the number of lambs born and the individual and total lamb weight averages were not significantly (P > 0.05) different between treatment groups and control group.

Animal Feed↗

PubMed1995

Serum swainsonine concentration and alpha-mannosidase activity in cattle and sheep ingesting Oxytropis sericea and Astragalus lentiginosus (locoweeds).

Serum alpha-mannosidase activity and swainsonine concentration were determined in 4 cattle and 15 sheep (3 groups of 5 each) that were administered ground locoweed (Oxytropis sericea or Astragalus lentiginosus) containing swainsonine at dosages of approximately 0.8 mg/kg of body weight/d (cows, 30 days each) and 0, 1.0, and 1.5 mg/kg/d (sheep, 11 days each). The cattle developed mild clinical signs of locoism, including signs of depression, lethargy, and slight intention tremors. Clinical signs of toxicosis were not observed in the sheep. Within 24 hours of initial treatment, serum alpha-mannosidase activity in cows and sheep, measured by the release of 4-methylumbelliferone from an artificial substrate, was markedly decreased to 28 and 40 mumol of 4-methylumbelliferone/L, respectively. Mean serum alpha-mannosidase activity of control cows and sheep was 400 +/- 94 and 422 +/- 42 (mean +/- SD), respectively. In the treated animals, decreased serum alpha-mannosidase activities returned to normal or higher activities within 6 days after treatment was discontinued. Using a jack bean alpha-mannosidase assay, increased swainsonine activity (153, 209, and 381 ng/ml, respectively) was detected in the serum of cattle and of sheep in the high- and low-dose groups within 24 hours after treatment with locoweed. Swainsonine concentration remained high, with mean concentrations of 204, 432, and 395 ng/ml (cows and 2 sheep groups, respectively) during the treatment period. After treatment, swainsonine was rapidly cleared, with estimated serum half-life of 16.4, 17.6, and 20.3 hours (cows, and high- and low-dose sheep groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1995

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.

Animals↗

PubMed1994

Effect of natural toxins on reproduction.

Poisonous plants grow in most plant communities found on rangelands and pastures. They are one of the principal causes of economic loss to the livestock industry. One major costly effect is on reproduction, which includes birth defects, abortions, lengthened calving intervals, and interference with oogenesis, spermatogenesis, libido, and estrus. Those plants that cause wasting, temporary illness, and other such effects can adversely effect reproduction livestock.

Abortion, Veterinary↗

PubMed1994

Serum alpha-mannosidase activity and the clinicopathologic alterations of locoweed (Astragalus mollissimus) intoxication in range cattle.

Subclinical intoxication of livestock with Astragalus and Oxytropis species (locoweeds) results in decreased animal feed conversion, reduced weight gains, and reproductive failure. Sensitive diagnostic methods to definitively diagnose and monitor intoxication are needed to minimize these losses and better manage locoweed-infested pastures and rangelands. Sera from cattle grazing locoweed were evaluated for alpha-mannosidase activity, serum biochemical values, electrolytes, and thyroid hormone concentrations. As the cows began to ingest locoweed, the mean serum alpha-mannosidase activities dropped significantly (400.0 microM to 72.5 microM). Changes in other serum chemistry values were less specific; however, individual animals (generally those ingesting more locoweed) had elevated levels of alkaline phosphatase (ALP), aspartate aminotransferase, and lactate dehydrogenase, with decreased serum total protein (5.8 +/- 0.8 g/dl) and albumin (2.3 +/- 0.3 g/dl). Mean serum thyroid concentrations (both T4 and T3) were lower in animals that were ingesting locoweed. The calculated swainsonine dose correlated statistically with serum alpha-mannosidase activity, ALP, albumin, Cl, CO2, and thyroid hormone T3. This correlation suggests that serum alpha-mannosidase activity along with potential changes in ALP, albumin, and thyroid hormone concentrations is a sensitive indicator of locoweed exposure and intoxication. These parameters may also be useful for monitoring intoxication and allowing subclinically affected cattle to be removed from infested areas before irreversible damage occurs.

Animals↗

PubMed1994

Effect of feeding ponderosa pine needle extracts and their residues to pregnant cattle.

Solvents including ethanol, methylene chloride, acetone, hexane, and hot and cold water were used in separate procedures to extract needles and bark from ponderosa pine (Pinus ponderosa L.) to determine which system was optimal for the extraction of abortifacient compound(s). The extracts and residues therefrom were fed by gavage to pregnant cows beginning at day 250 of gestation. After methylene chloride extraction, the pine needle residue fed by gavage failed to abort 4 cows. Subsequently, 4 cows fed the methylene chloride extractable material, adsorbed on ground hay, but free of methylene chloride, aborted (days 253-260 of gestation) and all 4 cows retained fetal membranes. Only 2 of 6 cows fed the pine needle residue after ethanol extraction aborted (days 260 and 261 of gestation) and both retained their fetal membranes, while the other 4 cows calved normally. Hot and cold water extracts did not cause abortion, whereas the extracted plant residue did. One cow fed the plant residue after acetone extraction calved normally as did 1 of 2 cows fed residue after hexane extraction. One cow fed hexane extract absorbed on ground hay also calved normally. These results demonstrate that abortifacient compound(s) present in pine needles are most efficiently extracted by methylene chloride.

Abortifacient Agents↗

PubMed1992

Effects of feeding ponderosa pine needles during pregnancy: comparative studies with bison, cattle, goats, and sheep.

Four experiments were conducted to determine the effect of feeding dried pine needles (Pinus ponderosa; PN) on the abortion rate of ruminants. In Exp. 1, cattle were fed 5.4 kg of PN daily for 21 d starting at 116, 167, 215, or 254 d of pregnancy. The PN did not cause abortions when started at 116 d; thereafter, the percentage of cows that aborted increased linearly, and the interval to abortion decreased linearly (both P < .01); all cows fed PN beginning at 254 d aborted. In Exp. 2, cattle were fed .7, 1.4, or 2.7 kg of PN for 21 d or 2.7 kg for 1 or 3 d. Sheep and goats were fed .8 and .5 kg of PN, respectively, starting at 121 d of pregnancy. The PN induced some abortions in cattle when fed for 1 (11%) or 3 (30%) d, but the abortion rate was greater (P < .01) when the PN were fed for longer periods of time (80, 90, and 100% aborted in 19, 17, and 10 d for .7-, 1.4-, and 2.7-kg doses, respectively). No goats or sheep aborted in response to PN feeding. Pregnancy rates during the next breeding season for cows that aborted in response to the PN were slightly higher than rates for control cows (94 vs 87%). In Exp. 3, buffalo (Bison bison) and cattle were fed 2.25 kg of PN from the same collection. Abortions were induced in all buffalo and cattle that were fed PN.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Veterinary↗

PubMed1992

The effect of natural toxins on reproduction in livestock.

Reproductive efficiency is the most important economic factor in livestock production. Thus, the hypothalamo-pituitary-gonadal regulatory axis, accessory sexual organ functionality, and the complex events involved in fertilization, implantation, and embryonic and fetal development may be sensitive to therapeutic agents, environmental pollutants, and natural toxicants. There are many factors that adversely affect reproduction, one of which is toxic substances in the diets of animals. Toxic materials can affect reproductive success by causing abortions, interfering with libido, estrus, oogenesis, or spermatogenesis, causing emaciation and subsequent abnormal mating behavior, birth defects, and increasing the time between parturition and rebreeding. Examples of natural toxicants in poisonous plants interfering with reproduction are numerous. Abortion in livestock from locoweeds, ponderosa pine needles, broom snakeweeds, fescue, and others are reported in studies. Selenium and seleniferous forage inhibit estrus in cattle and swine. Emaciation and temporary illness from sneezeweeds, bitterweed, locoweed, larkspur, lupines, and others may interfere with mating. Embryonic loss and birth defects from Veratrum, lupines, locoweeds, poison hemlock, and so on, may occur. As suggested, toxins have many diverse and economically adverse effects on reproductive performance in livestock.

Animals↗

PubMed1992

Ponderosa pine needle-induced parturition in cattle.

Needles of the Ponderosa pine (Pinus ponderosa) induce premature parturition in cattle when ingested during late pregnancy, especially during the third trimester. The closer to term, the more likely that pine needles will induce parturition. Experiments were designed to describe the clinical signs and behavior associated with ingestion of pine needles. Pine needles adversely affected only pregnant cows and did not seem to affect nonpregnant, cycling cows, sheep, goats, or rabbits. Premature parturition was more likely if cows ingested the needles after the 8th mo of pregnancy, if they ingested pine needles over a period of 3 d or more, and if cows ate a relatively large amount of pine needles (about 2.2 to 2.7 kg/d). A synthetic progesterone, melangesterol acetate, and a prostaglandin inhibitor (ketoprofen) seemed to be of some prophylactic benefit; however, further research is required to assess the practicality of the approach and the magnitude of the benefit. Ponderosa pine bark and new-growth branch tips, which seem to be more potent inducers of premature parturition, may be useful in the extraction and identification of the parturifacient component(s).

Animals↗

PubMed1992

Ultrasound studies of the effects of certain poisonous plants on uterine function and fetal development in livestock.

Ingestion of locoweed (Astragalus spp. and Oxytropis spp.) by pregnant livestock may result in fetal malformations, delayed placentation, reduced placental and uterine vascular development, hydrops amnii, hydrops allantois, abnormal cotyledonary development, interruption of fetal fluid balance, and abortion. Ultrasonography of pregnant sheep fed locoweed demonstrated that abortion was first preceded by changes in fetal heart rate and strength of contraction and structural changes of the cotyledons, followed by increased accumulation of fetal fluid within the placental membranes and death of the fetus. During pregnancy the toxic agent in locoweed (swainsonine) apparently passes through the placental barrier to the fetus and during lactation through the milk to the neonate. Poison-hemlock (Conium maculatum), wild tree tobacco (Nicotiana glauca), and lunara lupine (Lupinus formosus) all contain piperidine alkaloids and induce fetal malformations, including multiple congenital contractures and cleft palate in livestock. Ultrasonography studies of pregnant sheep and goats gavaged with these plants during 30 to 60 d of gestation suggests that the primary cause of multiple congenital contractures and cleft palate is the degree and the duration of the alkaloid-induced fetal immobilization.

Animals↗

PubMed1991

Swainsonine-induced high mountain disease in calves.

Swainsonine, an indolizidine alkaloid in the locoweeds (certain species of the Astragalus and Oxytropis genera), was fed to young Holstein bull calves in their milk at high elevation (3090 m), and the incidence of high mountain disease (HMD) was compared with locoweed-fed and control calves. Five of 5 calves fed swainsonine and 5 of 5 calves fed fresh Oxytropis sericea showed outward signs of HMD, which included edema under the jaws, throat area and brisket and gross and microscopic lesions of HMD and locoweed poisoning. Grossly there were HMD lesions, including congestion of the liver, right ventricular hypertrophy, and dilatation and excessive fluid in the thoracic and abdominal cavities. Microscopically, the severe centrilobular lesions in the liver, edema of the pulmonary artery, severe edema and/or fibrosis of the roof of the right atrium were suggestive of HMD. The mild to moderate neurovisceral cytoplasmic foamy vacuolation of selected tissues and cerebellar neuroaxonal dystrophy in all calves fed swainsonine and locoweed were indicative of locoweed poisoning. In control calves, 1 of 6 showed equally severe outward, gross, and microscopic lesions of HMD, but none had any lesions indicative of locoweed poisoning. The ratio of right ventricle to left ventricle wall weights were significantly higher (P = 0.033) for the swainsonine-fed calves (1.4) and the locoweed-fed calves (1.3) compared to the controls (0.9). Scores indicating the severity of HMD from observations prior to necropsy were significantly higher for the swainsonine and locoweed-fed calves compared to controls (P = 0.032).(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗