Nitrate toxicity, while it is still imperfectly under- 

 stood, tends to show some tendency toward preva- 

 lence in areas of the Great Plains having high- 

 soil fertility and a high water table. 



Sulfates and their derivatives may also be used 

 as examples of product-oriented contamination 

 in discharge waters from paper mills which are 

 located in various regions of the country where 

 geographical conditions support timber growth. 

 Development of large-scale livestock feedlots has 

 generally taken place in dryer regions where dis- 

 ease control is easier. Consequently, specific prob- 

 lems of water pollution related to this industry 

 acquire a regional pattern. 



description of major 

 quality considerations 



Species 



Some interesting species differences also exist 

 among livestock tolerances to water pollutants. 

 A pertinent example of these is the variable re- 

 sponse of different types of animals to salinity con- 

 centrations. Standards developed in western Aus- 

 tralia as safe upper limits for livestock are listed 

 in table IV-10 (122,190). 



TABLE IV-10. Proposed Safe Limits of Salinity 

 for Livestock 



Threshold salinity 

 concentration ^ 

 Animal TDS mg/l 



Poultry 2,860 



Swine 4,290 



Horses 6,435 



Dairy cattle 7,150 



Beef cattle 10,000 



Sheep (adult, dry) 12,000 



1 Total salts, mainly NaCI. 



These values should not be taken as absolute, 

 but rather interpreted as indicative of the signifi- 

 cant species variation that exists. They were de- 

 veloped in a subtropical environment and may not 

 be readily translatable to more temperate areas. 

 Obviously, when feed is also high in salt content, 

 a lower water salinity would be desirable. More- 

 over, when animals are consuming high-moisture 

 forage they can tolerate more saline water than 

 when they are grazing dry "bush" or "scrub." 



Discussion of individual items as they 

 affect livestock 



Mineral Salts 



One of the commonest types of water contami- 

 nants is the mineral salts due to their ubiquitous 

 occurrence and their solubility characteristics. 

 Highly mineralized waters can cause physiological 

 disturbances in animals including gastrointestinal 

 symptoms, wasting disease, and sometimes death. 

 Animals subjected to physiological stresses, such 

 as reproduction, lactation, or rapid growth, are 

 particularly susceptible to mineral imbalances, 

 hence they pose a real threat to animal production. 

 It is not prudent to generalize on overall "salt" 

 levels in water since some salts are specifically 

 toxic, such as nitrates, fluorides, selenates, and 

 molybdates (77). "Alkalinity" of water, while it 

 does not represent a single polluting substance, 

 but rather a combination of various effects and 

 conditions, is a common measurement that carries 

 some significance. Caustic alkalinity in concentra- 

 tions of 50 mg/l and 170 mg/l has been reported 

 to cause diarrhea in chickens and other animals 

 (77). The following data are pertinent to estab- 

 lishment of tolerance levels for specific inorganic 

 elements or their salts. 



The establishment of criteria for every poten- 

 tially hazardous material which might occur in 

 water is not feasible. Allowable concentrations of 

 certain trace elements, as listed in table IV-1 1 , are 



134 



