introduction and 

 general problem areas 



Relationship of water to total diet 



Domestic livestock represent an important seg- 

 of the complex, interdependent organization of 

 living things on earth. As plants are considered 

 the "great anabolizers," animals are the "great 

 converters" which provide energy and other basic 

 necessities in forms that are both useful and palata- 

 ble to mankind. It is significant that they are a part 

 of the world's renewable sources of energy, as 

 opposed to the fixed sources, such as fossil fuels. 

 Because of these attributes, the future of domestic 

 animals must be carefully guarded. 



Both domestic animals and man occupy the 

 ■paradoxical position of contributing to, and being 

 affected by pollutants in their environment. Much 

 of this environment, even for land animals, is 

 aqueous, and water is of paramount importance 

 as a vehicle for metabolites and their degradation 

 products — hence the purity of water consumed 

 by livestock has far-reaching implications. There 

 are many ways in which livestock water supplies 

 may be contaminated. These may be direct, as 

 for example where ground water rises from a 

 parent soil or rock formation having unusual 

 mineral content — either excessive or deficient in 

 relation to the nutrient requirements of animals. 

 They may also be indirect in the sense that fertil- 

 izers added to aid crop production may stimu- 

 late biological growth (microbial, algal) in 

 impounded water to the point where animals con- 

 suming that water may be affected. These ma- 

 terials may also produce varied effects. They may 

 impede the husbandry of livestock either by caus- 

 ing death losses or by interfering with reproductive 

 processes. They may also contaminate animal 

 products (e.g. milk) to the point where human 

 consumption may be objectionable. Pollutants may 



be of varied types including mineral salts, organic 

 growth, parasitic organisms, pesticide and herbi- 

 cide residues, and more recently, radionuclides. 

 It is important to have some understanding of the 

 levels of these various substances that can be 

 safely tolerated by livestock and the levels that 

 constitute hazards. 



In approaching this study, it is axiomatic that 

 although water is universally needed and consumed 

 by farm animals it does not constitute their entire 

 ingested intake. Thus, the tolerance levels that 

 have been established for many substances in 

 livestock feed do not accurately represent the 

 tolerance levels in water. In this connection, some 

 assessment of the amounts of water consumed by 

 various species of livestock is useful; however, the 

 literature on this subject is not voluminous. Since 

 water is usually given ad lib., it is not customary 

 to measure its uptake by individual animals except 

 on an experimental basis. Terminology may also 

 sometimes be confusing. "Water consumption" 

 usually denotes free water drunk by an animal, 

 whereas "total water intake" includes the moisture 

 content of the feed. The former designation is more 

 appropriate for the purpose of this study; however, 

 the interaction between water and dry diet cannot 

 be ignored. Many factors influence the water 

 consumed by livestock so that generalizations be- 

 come unwise if not impossible. Some of the more 

 obvious of these factors are species, age, and con- 

 dition of animal; the coat covering (as related to 

 evaporation losses); ambient temperature, and 

 the nature of the diet — particularly with relation 

 to its moisture content. With the reservations noted 

 above, table IV-8 has been assembled as repre- 

 sentative of approximate "normal" ranges of water 

 consumption for various classes of livestock (/, 

 85,161). 



TABLE IV-8. Normal Water Consumption 



Water consumed. 

 Animal gallons per day 



Beef cattle, per head 7-12 



Dairy cattle, per head 10-16 



Horses, per head 8-12 



Swine 3-5 



Sheep and goats, per head 1-4 



Chickens, per 100 birds 8-10 



Turkeys, per 100 birds 10-15 



Effect of water on plant composition 



The effects of water pollutants upon livestock 

 may be mediated directly through water drunk by 



130 



