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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)

Calves, lambs, and kittens given milk from cows fed locoweeds developed microscopic lesions typical of locoweed poisoning. Serum aspartate aminotransferase activities increased markedly during the feeding period in both the cows given the locoweed and the animals receiving their milk. The results of this experiment indicate that the toxin in locoweed can be secreted in the milk.

Certain plants accumulate selenium at levels that render them toxic. One of the principle groups of selenium-accumulating plants is the selenium-accumulating Astragalus. Reports in early literature suggest that selenium is the only toxin in these plants. Sheep fed Astragalus bisulcatus, a selenium-accumulating plant, had signs similar to those observed in locoweed poisoning, and the microscopic lesions from tissues collected from these sheep were similar to those of locoweed poisoning rather than selenium poisoning. This suggests this group of plants contains toxin compounds in addition to selenium.

Pollens collected from Astragalus lentiginosus and Oxytropis sericea were fed to mice. At the end of the feeding period, uterine weights were taken to determine estrogenic activity, and tissue was collected for microscopic examination. The pollen from A lentiginosus, but not from O sericea, induced lesions similar to those of locoweed poisoning. The pollen from neither plant was estrogenic. Seeds from A lentiginosus produced toxicosis when fed to rats.

Locoweed (Astragalus lentiginosus) fed to mature rams induced transient degenerative changes in the seminiferous, epididymal and vas deferens epithelium. There were changes in behavior and loss of condition in the treatment rams. Observed libido was reduced. Estimated percent abnormal sperm was significantly (P less than 0.05) higher in the locoweed-fed rams than in the controls. Increased retained proximal cytoplasmic droplets, separation of the heads and tails of the spermatozoa, and reduced sperm motility were observed. Serum SGOT (serum glutamic oxaloacetic transaminase) levels were significantly (P less than 0.01) elevated, and WBC (white blood cell) counts were decreased (P less than 0.01). Grossly no changes were observed. Histologically there were advanced lesions of foamy cytoplasmic vacuolation in all tissues taken at necropsy, but particularly in the epithelium of the seminiferous tubules, epididymis and vas deferens. Reduced spermatozoa production was evident. Testicular changes were transient and rams appeared clinically normal 70 days after locoweed feeding was terminated; however, there was slight residual atrophy of the germinal epithelium at necropsy.

Locoweed (Oxytropis sericea), when fed to calves at high elevations, increased the prevalence and severity of congestive heart failure. Forced exercise did not increase the prevalence of congestive heart failure, but it did increase severity. Calves consuming locoweed at high elevations developed signs and gross lesions of congestive heart failure and microscopic lesions of congestive heart failure and locoweed poisoning. Calves fed locoweed at low elevations developed only signs and lesions of locoweed poisoning.

Locoweed (Astragalus lentiginosus) was fed to ewes from 70 to 100 days of pregnancy. Ewes were killed at 100, 115, 130, and 145 days, and selected tissues were collected from both the dam and the fetus for histologic examination. Neurovisceral cytoplasmic vacuolation and neuroaxonal dystrophy decreased in dam and fetus with time after the feeding of locoweed was discontinued.

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)

Various species of nitro-containing Astragalus, and the toxic principle of these plants, 3-nitropropionic acid or 3-nitro-1-propanol, were fed to sheep and cattle at doses which produced chronic or acute intoxication. The signs of intoxication produced were similar to those observed in poisoning that occurs under field conditions. The signs of intoxication were emphysema and difficulty in locomotion. Primary microscopic lesions were observed in the lungs and CNS. The lungs had varying degrees of alveolar emphysema and there were varying degrees of wallerian degeneration of the spinal cord.