the animals or secondarily through the effect of 

 ground water pollutants upon composition of plant 

 forages subsequently consumed. In some cases 

 plants serve as a protective buffer against animal 

 damage since they cannot themselves tolerate 

 amounts of contaminants that would be hazardous 

 to livestock. A case in point is boron which, al- 

 though required by growing plants, cannot be 

 tolerated by them in soil water concentrations of 

 over 4.0 mg/1 on a continuous basis. No evidence 

 has been found that such a level in drinking water 

 is injurious to animals. On the other hand, some 

 plants take up from either soil water or the parent 

 soil material considerably larger amounts of cer- 

 tain materials than animals can ingest with safety. 

 One of the best examples of this type of situa- 

 tion is the "selenium accumulator" type of plant, 

 like the genus Astragalus, which has been reported 

 to contain from 1,000 to 10,000 mg/kg of sele- 

 nium (143). When one considers that the toxic 

 level of selenium in feeds consumed by animals 

 on a routine basis is about 4 mg/kg, it is obvious 

 that plant growth cannot be accepted as a valid 

 criterion of safety to animals. A further example 

 of dangerous contamination of water, as far as 

 livestock are concerned, is molybdenum. In Flor- 

 ida, where cases of molybdenosis have occurred, 

 the molybdenum content of ground water varied 

 from to 8.5 mg/I (38) and in some instances 

 forages were produced that were so high in molyb- 

 denum that severe scouring occurred among live- 

 stock. It is perhaps unwise to deal with mineral 

 contaminants individually as distinct entities since 

 there are frequently metabolic interrelationships 

 among them. It is generally accepted, for example, 

 that molybdenum toxicity may be alleviated to a 

 considerable extent by increasing copper content 

 of the diet (707). 



Other, less direct effects of water contamination 

 upon livestock production are evidenced by the 

 relationships of soil and irrigation water salinity 

 to plant growth. Here the effects are measured in 

 terms of reduced forage yield, or perhaps inability 

 to produce certain desirable forage plants, rather 

 than in terms of any direct action upon the animals 

 themselves. 



Fish as indicators of water safety for 

 livestock 



The presence of fish in a source of water for 

 livestock may be an excellent measurement of 

 toxicity and to a limited extent its acceptability 

 from an aesthetic viewpoint. Ultimately, livestock 



standards may include aesthetic values applied to 

 water used by man despite the fact that animals 

 may consume water which is grossly contaminated 

 with fecal organisms, animal matter, and dissolved 

 substances available in the environment. 



Considerable evidence is available in the sci- 

 entific literature suggesting lower tolerance levels 

 for various agricultural chemicals (including pesti- 

 cide residues) for fish than for livestock. Accord- 

 ingly, presence of living fish in agricultural water 

 supplies indicates their safety for livestock (105). 

 Some examples of individual effects in fish and 

 animal species are included in table IV-9. 



TABLE IV-9. Examples of Fish as Indicators of 

 Water Safety for Livestock (105) 



Changing patterns of livestock production have 

 introduced some problems and variables affecting 

 man's activity. The economic capability to pro- 

 duce livestock, whether it be poultry, swine, beef, 

 or dairy cattle, in confinement creates a very 

 practical problem of sewage disposal equal in 

 volume to effluent from some small cities. The 

 problem may be made acute by the concentration 

 of wastes in a single drainageway with its impli- 

 cation of gross contamination of larger water sys- 

 tems particularly during rainfall periods. If fish 

 are able to survive in the terminal management of 



131 



