W41 

 (leaf 2) 



summer, the poisoning hazard is lessened since succulent grasses and 

 other forage are more likely to be present. This plant remains green 

 through the late fall and winter when it again is readily eaten, 

 especially by horses. 



Livestock losses are largely confined to horses on ranges where 

 woolly loco is the only poisonous plant. However, occasional cattle 

 and sheep losses are attributed to this pest. Losses are much less 

 among animals native to the range than they are among newcomers to 

 the range. Generally, the finer breeds of horses and cattle are much 

 more susceptible to loco than the usual range breeds, grades, cross- 

 breeds, or scrubs. This is true also of sheep, since losses are more 

 likely to occur among such breeds as Hampshires and Southdowns 

 than with Rambouillets and Merinos. 2 



Losses of horses have been especially heavy in Texas and Arizona, 

 while the major cattle fatalities have occurred in Colorado. A 

 peculiar feature about loco poisoning is that death usually does not 

 occur immediately from a single feeding, but comes only after con- 

 tinued and comparatively heavy use of the plant. However, this 

 species frequently exerts a more pronounced effect on horses than 

 any other loco, so that heavy losses sometimes occur in a short time. 

 In many cases, several weeks or months may elapse before the animal 

 is observed to be affected. Initial symptoms of poisoning include 

 in horses a general depression; the animal becomes dull and in- 

 clined to laziness, loses weight, and often looks poor and scrawny. 

 As the disease develops, the symptoms become more evident, The 

 animal is generally weak, walks with an irregular gait, drags its 

 feet, particularly the hind ones, and exhibits an apparent lack of 

 muscular control and coordination. The optical nerves are evidently 

 affected, because the animal usually mistakes small objects for large 

 ones, often steps high over the slightest obstruction and leaps over 

 small depressions, as if they were big ditches. The disease apparently 

 causes near-sightedness, since a badly locoed horse often fails to 

 notice any objects except those within close range. In fact, a person 

 can approach within a few feet of a locoed horse without detection. 

 Then, unexpectedly, the animal will rear backwards and often fall 

 upon the ground. The diseased beast drinks with a chewing move- 

 ment of the jaws, shies violently at imaginary objects, cannot be 

 backed readily and, if started forward, will travel at the same gait 

 until stopped by some obstruction. 2 During the later stages of the 

 disease, the horse loses flesh and its coat becomes rough. 



Locoed cattle display symptoms very much like those of similarly 

 affected horses, but the symptoms of sheep are not so marked, al- 

 though the animals soon evince weakness. They fall frequently, and 

 rise only with great difficulty. The animals usually die of starva- 

 tion; post-mortem examinations almost invariably reveal accumula- 

 tions of coagulated serum in various parts of the body. These con- 

 centrations are most pronounced around the heart and along the 



z Marsh, C. D. THE LOCO-WEED DISEASE. U. S. Dept. Agr. Farmers' Bull. 380. 16 pp. 

 1909. 



