POISONS AND THEIR ANTIDOTES. 1363 



The white loco is found much more widely distributed than the purple 

 loco, extending from the northern to the southern border of the United 

 States, as far east as central Minnesota, and as far west as western Utah 

 and Arizona. 



III. Poisoning by Loco Plants. 



It was found when the loco investigation was undertaken by the Bureau 

 of Plant Industry that there was a very general belief among stockmen 

 that the purple loco weed was a poisonous plant and a less general belief 

 that the white loco weed was injurious. 



The field work which has been carried on during the past three years 

 has demonstrated that horses, cattle, and sheep in the field can be poisoned 

 by feeding upon these two plants. It has also been shown very clearly 

 that the purple loco weed is very rarely injurious to cattle. In those sec- 

 tions where the purple plant is the only loco weed known, the losses from 

 poisoned stock are found to consist almost exclusively of horses. This 

 seems to be because cattle will not readily eat , this plant. The 

 experiments show that under ordinary circumstances most cattle would 

 prefer to starve rather than to eat any of the purple loco weed. The 

 majority of horses do not take readily to this plant except as they are 

 induced in the first place to eat some of it because of short feed. It has 

 been demonstrated that the so-called loco disease of the Plains is not sim- 

 ply a matter of starvation, as has been supposed by many, and it is also 

 clear that when other food is abundant very few horses will eat loco. 

 When, however, because of shortness of grass a horse is induced to begin 

 the eating of loco, it is very likely to contract a habit which leads to con- 

 tinual feeding upon the weed, with eventually fatal results. 



In regard to the white loco weed the experiments showed very clearly 

 that horses, cattle, and sheep will eat this plant with great readiness, par- 

 ticularly if they come across it at a time when grass is somewhat scarce. 

 Both the white and the purple loco weeds are green during the winter, 

 when all grass on the plains is dry and brown. They are prominent 

 plants, too, which induces an animal to try them, and because of their 

 succulent character and somewhat pleasant taste, it may continue to eat 

 them. Not only horses but cattle and sheep will eat the white loco weed, 

 and sometimes even with great avidity. Many animals will eat this weed 

 even when grass is abundant, but it is more common for the habit to be 

 contracted during the autumn, winter, and spring, when there is a scarcity 

 of green grass. Both horses and cattle will eat the white loco weed read- 

 ily, but perhaps cattle take to it more readily than horses. During the 

 spring months, before the grass starts, where the white loco weed is abun- 

 dant, practically all animals eat more or less of it. As the grass becomes 

 more abundant many of these leave the loco weeds and devote themselves 



