BOOTS, TUBERS, AND MISCELLANEOUS FORAGES 253 



These must be broken down and the free prussic acid liberated, before 

 poisoning occurs. However, these glucosides are readily decomposed by 

 certain enzymes which are usually present in the plants. Therefore the 

 prussic acid may be set free in the digestive tract of an animal eating 

 plants containing these glucosides. 



Normally the sorghums are entirely harmless, for they contain no 

 prussic acid, or only such small amounts that no poisoning is produced. 

 However, when plants of the sorghum family, including the grain sor- 

 ghums, the sweet sorghums, and also Sudan grass and Johnson grass, 

 are stunted by drought, prussic acid may accumulate in such quantities 

 as to kill animals eating the plants. The affected stock often die in a 

 few minutes after eating only a few mouthfuls of the forage, so poison- 

 ous is prussic acid. Cases of poisoning by the sorghums have been large- 

 ly confined to the western semi-arid districts, which are especially subject 

 to protracted droughts. Second-growth sorghum and that grown on 

 rich soil are most apt to be poisonous when stunted. 



The prussic acid largely disappears from sorghum when it is cured. 

 Hence dry sorghum fodder or stover is practically always safe to feed. 

 In the ensiling process the prussic acid is destroyed, so sorghum silage is 

 entirely safe. In pasturing the sorghums the only way to prevent serious 

 loss is to turn an animal of little value into the field first. If no poison- 

 ous effects are observed, the rest of the stock may then be allowed to 

 graze the crop. 



The leaves of the wild cherry are particularly fatal to cattle, especially 

 when wilted. 



396. Ergot. The seeds of rye and many grasses are sometimes at- 

 tacked by a fungus which produces enlarged black, sooty masses, known 

 as ergot. Occasionally rye grain containing ergot, or hay or straw bear- 

 ing the fungus severely injures cattle which are continuously fed there- 

 on during winter. Ergot acts on the nervous system, depressing heart 

 action and thereby restricting the blood circulation. In pregnant ani- 

 mals abortion is often caused. Affected animals have colicky pains and 

 the circulation in the ears, the tip of the tail, and the feet may be stopped 

 to such a degree that gangrene sets in and the diseased parts slough off. 

 Animals showing symptoms of this trouble should have their feed 

 changed to remove the cause, and be warmly housed and liberally sup- 

 plied with nourishing food. 



397. Forage poisoning. From time to time serious losses of stock have 

 occurred in various parts of the country, especially in the Central West, 

 from forage poisoning, or blind staggers. It affects horses, mules, and 

 cattle chiefly, and sheep less frequently. During the summer and fall 

 of 1912 thousands of horses were killed by forage poisoning in the 

 Mississippi valley, and local outbreaks have caused serious losses in 

 recent years. The trouble occurs most frequently in animals fed corn 

 silage or corn fodder or stover. 



Graham of the Illinois Station has recently found that at least many 



