A PASTURE HANDBOOK 59 



PRECAUTIONS AGAINST DISEASES AND PARASITES 



Although, as previously stated, pastures are conducive to the 

 general health and vigor of hvestock, there is need for taking precau- 

 tions against certain diseases and parasites. Tuberculosis, for instance, 

 though much less common among cattle on ranges than in those 

 confined much of the time in stables, may be spread by such means as 

 infected watering holes and ponds. It is apparent that the droppings 

 of tuberculous animals in the water supply may pollute it sufficiently 

 to infect other cattle that drink the water. 



Anthrax, another serious germ disease, is caused by bacilli that 

 thrive best under certain conditions of the soil, especially in regions 

 subject to floods and inundations. Fields containing stagnant pools 

 may be a source of infection. Various parasitic diseases, such as tick 

 fever of cattle and infestation of sheep and other anunals with various 

 internal parasites, are associated with the spread of parasites directly 

 or indirectly in connection with grazing. When it is possible, young 

 animals should be given fresh pasture land. Rotating hogs and 

 horses with cattle and sheep in alternate years should lessen materially 

 hazards from parasites. 



Certain ailments result from animals' gorging themselves on suc- 

 culent pasture or from grazing on poisonous plants. Methods of 

 preventing loss from such causes are discussed more fully in the 

 specific recommendations for pasture management. As a general 

 precautionary measure it is advisable to burn to ashes or bury deeply, 

 animals that die of infectious diseases, never leaving them on pasture 

 where the infection may be spread by other animals or birds. Helpful 

 information may be obtained, also, from Department publications, 

 relating to the control and eradication of animal diseases and para- 

 sites, which wiU be furnished on request. 



STOCK-POISONING PLANTS ^ 



Poisoning of animals from eating certain plants usually occurs 

 when the more nutritious and palatable plants or other feeds are 

 not available in sufficient quantities or in great enough variety to 

 satisfy the animals' appetites or requirements. Most poisonous 

 plants are unpalatable; therefore as a general rule, animals do not 

 readily eat them in sufficient quantities to be seriously injured. 



Poisonous plants vary greatly in the following respects: (1) The 

 condition under which animals are poisoned by them, (2) the portion 

 of the plant that is most poisonous, (3) changes in the toxicity of the 

 parts of the plants during growth and in drying, (4) the susceptibility 

 of different species of animals to being poisoned by them, and (5) the 

 effects on the poisoned animals. To diagnose cases of plant poisoning 

 correctly, one must have considerable information about the dift'erent 

 plants and their effect on animals. Diagnosis is simplified by a 

 knowledge of the principal poisonous species in the area in which the 

 pasture is located. Essential facts regarding the principal poisonous 

 plants in the United States are given in table 9. 



« This discussion was prepared by A. B. Clawson, associate physiologist, Pathological Division, Bureari 

 of Animal Industry. 



