Locoweed, a well-known teratogenic plant affecting livestock, is prevalent in mountain regions of the Western United States. Two common species (Astragalus lentiginosus and A. wootoni), administered to pregnant rats, induced behavioral deviations in their offspring. Treated mothers consumed less feed and gained less wieght during gestation than controls when gavaged locoweed at the rate of 1 gram whole plant per day on days 7 through 17 of gestation. A. lentiginosus reduced pup weight at birth (13% less than controls) and this weight reduction (as much as 29% less than controls) continued at least four weeks. A. lentiginosus also reduced number of offspring born alive (34.9% less than controls) and number which survived until weaning (86.4% less than controls). No gross malformations were observed in the offspring of loco-treated dams. however, when the pups were subjected to behavioral testing (beginning at 30 days of age), deviations were observed. there was considerable difference among the treatment groups when tested with the activity wheel (P=.0000). Water-intubated controls did not differ from non-fed controls, but the two loco-treated groups differed in opposite directions from controls. A. lentiginosus offspring were more active (26.5%) overall than other groups, and had an abnormal pattern of activity in the day to evening night activity totals. A. wootoni offpsring were less active (25%) than other groups in the activity wheel. Significant differences among groups were also observed in the open-field test. The trend was toward decreased activity (P=.027; 31 and 43% less than controls - A. lentiginosus and A. wootoni respectively) and increased number of fecal boluses (P=.06; 45.5 and 19.3% more than controls - A. lentiginosus and A. wootoni respectively) in the loco-treated offspring. There were no significant differences in avoidance conditioning in a two-way shuttle box among the groups, though the loco offspring made fewer avoidance responses than controls. Alizarin Red-S staining of fetuses revealed no skeletal defects in the pups. Microscopic examination of maternal tissues showed the kidney and liver degenerative changes which are typical of locoweed intoxication: primarily vacuolation of proximal tubular epithelium and of the hepatocytes. Tissues from pups on day of birth also showed mild kidney and liver changes. Older pups had no visible microscopic deviations from normal. The results indicate that the locoweed teratogen produces behavioral deviations in the offspring of rats in the absence of gross malformations.

Locoweed poisoning, caused by ingestion of certain species of Astragalous and Oxytropis, has had serious economic impacts through a loss of productivity in livestock. This study has attempted to evaluate losses suffered by livestockmen grazing their cattle on areas infested with locoweed species. The results indicate a serious economic impact on these individuals. Personal interviews were carried out with five cattle ranchers faced with typical locoweed problems. These beef cattle operations were located in Utah, Wyoming, and New Mexico. All of these producers described similar problems and losses due to locoweed poisoning. Information obtained from these interviews was used to estimate a 1978 dollar loss for three ranches, running in common, and located near Park Valley, Utah. This study found the problem areas to be: (1) reduced weaning weights of calves; (2) increased requirements in the number of replacement heifers; (3) an increase in death loss; (4) reproductive problems (abortions and infertility); and (5) increased costs associated with labor and management problems. The summation of economic losses in each of these problem areas reflected a total estimated loss of $30,689.02 in 1978. To determine if locoweed poisoning had long-range effects on weight gains, a sample of 20 calves were put on a 138-day feeding experiment. Of these 20 calves, 12 had grazed a locoweed-infested area, while the remaining 8 had no access to the plant. Overall average gain of both groups was found to be nearly identical. This indicates that animals will recover with proper but, sometimes, costly management. Profitability of spraying locoweed-infested ranges with 2,4-dichlorophenoxy acetic acid (2,4-D) was determined through information supplied by the Wyoming rancher. An internal rate of return of 39.4 percent was found by using this method of locoweed control in this particular instance. Ranchers interviewed in this study estimated their losses due to locoweed poisoning to be from 30 to 40 percent reduction in profit. Although profit margins were not determined, the estimated loss of $30,689.02 found in this study would be close to their determination. With the rampant increase in operating costs which have occurred in the past decade, producers could not long endure losses of this magnitude. However, it was determined that with proper plant control and management these losses could be substantially reduced.