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Impact of Water


Impact of Water on Laboratory Animals

Animal watering is done using either drinking bottles placed in each cage, or an automatic watering system. While animal feed quality is usually tightly controlled, the requirements for animal watering are less stringent. The US National Research Council Guide for the Care and Use of Laboratory Animals is recognized in many countries as the standard for quality animal care and use. It states that “Ordinarily animals should have continuous access to fresh, potable, uncontaminated drinking water, according to their particular requirements.”

While ordinary tap water can be used for animal watering in some cases, the fact that its composition may vary with time and with the seasons can be a problem for researchers. Tap water variations may also be an issue when comparing the results of research performed in laboratories located in different geographical locations. In order to obtain consistent and reliable experimental results, it is important to provide laboratory animals with drinking water of consistent quality. In addition, some animals (for example, immuno-compromised animals) or disease models are known to be very sensitive to their environment and require very pure water.

The following water contaminants should be avoided:
  • Organics
    Some organics, such as pesticides, endocrine disrupters, etc. which may be present in tap water, can affect the health of laboratory animals and interfere with the research being conducted. In addition, in the presence of chlorine, organics may form disinfection by-products (DBP), some of which are thought to be carcinogenic or affect reproduction. Organics can also be used as nutrients by bacteria, and lead to bacterial proliferation. Organics can be removed by activated carbon and reverse osmosis technologies.

  • Bacterica
    Bacteria can cause serious health problems to the animals and are a main concern in animal facilities. Immuno-compromised and transgenic animals are especially sensitive to bacterial contamination. Pseudomonas aeruginosa, for example, is an opportunistic pathogen commonly found in water, and may affect the health of vulnerable animals. Bacteria levels in water can be minimized by reverse osmosis.

  • Heavy metals
    High levels of heavy metals (copper, iron, zinc, lead …) can be toxic for health-compromised animals. These metals can be leached from piping. Ions and metals present in water can be greatly removed by reverse osmosis.

  • Hardness and particles
    Hard water deposits and particles can damage the valves of automated watering systems, and cause leaks inside the animal cages. They will also increase the need for system maintenance.
In conclusion, water purified by reverse osmosis is usually recommended for this application, as it removes most of the organics and ions present in the feed water, and provides a consistent water quality. Tap water composition may vary with time and with the seasons, and should not be used for laboratory animals. Deionized water, purified with ion exchange resins, may contain organics and microorganisms, and is therefore not recommended.

Reverse osmosis water is usually treated before being used to water laboratory animals, in order to minimize the risks of bacterial contamination within the animal facility. Ozone treatment or ultra-violet irradiation may be used, but the most commonly methods are chlorination and acidification.
  • Chlorination
    Chlorination is commonly used. Water pH should be regularly controlled, as chlorination is less effective at high pH. Accepted practice is to reach a residual range of free chlorine between 5 and 12 ppm.

  • Acidification
    Acidification is more stable and lasts longer in the system than chlorine. The disadvantage of chlorination is that corrosion-resistant materials must be used. The pH range should be between 2.6 and 3 in order to be effective. The animals may refuse to drink the water if the pH is 2.5 or lower because of poor taste.


References
You may find more information related to laboratory animals in the following web sites:
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