Novák,P., Malá, G., Polcr,S., – Výzkumný ústav živočišné výroby, v.v.i., Praha Uhříněves, Tekro Praha, s.r.o.

Water is one of the most important nutrients for animals. Due to the ever-increasing problems with the provision of water with sufficient quality, the issue of drinking water for poultry is a topical issue. Breeders often pay great attention primarily to achieving optimal production indicators. However, they do not pay much attention to the amount of water received and its quality. It is common that often the causes of breeding failures are due to poor quality of drinking water or insufficient water intake by animals. Likewise, only a part of poultry farmers pay attention to regular sanitation of watering systems.  On most farms, various problems can be encountered, ranging from minor faults such as minor defects in watering lines (e.g. valve leaks, water pressure fluctuations, etc.), up to the use of completely unsatisfactory water sources for the watering of animals. At the same time, regular cleaning and disinfection of watering systems is a prerequisite for maintaining the quality indicators of the water intended for livestock watering. It is important to distinguish processes aimed at cleaning and disinfection of drinking water from the cleaning and disinfection of all components of the watering systems (distribution systems, reservoirs, filters, drinkers, drain valves, dosing devices etc.).

Water contamination consists mainly of organic and inorganic substances, which serve both as a source of nutrients for microorganisms and also support biofilm formation in watering systems.
The cleaning process promotes the maintenance of the operational reliability of the watering system, while the micro-organisms are mechanically removed during cleaning, including nutrients, which are involved in biofilm formation. Effective cleaning is a prerequisite for achieving high efficiency of subsequent disinfection, which aims to devitalize the microorganisms in watering systems.
The cleaning of watering systems can be divided into external and internal ones. External cleaning is aimed at cleansing the surface of watering systems, including the surface of drinkers, preferably by using alkaline detergent products applied as a foam using low-pressure washers. Internal cleaning is aimed at removing dirt from the watering lines. Besides the chemical products, physical procedures can also be used to clean watering systems. One of the simple methods is to flush the water system with fresh water under high pressure, which can also be carried out during the run, when animals are present in the hall. Some authors recommend using this method of watering line cleaning always before and after the use of feed additives, medicines and vaccines administered through drinking water.
Disinfection focuses on the devitalization of microorganisms in watering systems and drinking water.

Many factors influence the effectiveness of disinfection:
-    amount and type of microorganisms in the watering system,
-    active substance in the disinfectant use,
-    concentration and contact time of disinfectant,
-    structure of inner surface of watering lines,
-    the level of scale contamination of the inner surface of watering lines,
-    presence of other contaminant substances in the watering system.

When disinfecting the watering systems between individual runs, it is necessary to drain the disinfectant from the pipeline after the contact time and thoroughly flush the system with clean water. The rests of some preparations used to disinfect watering lines can lead to a significant reduction in water consumption in animals. Residual concentrations of some preparations may also have a negative effect on the amount and composition of intestinal microflora; toxic effect of some preparations may even result in increased morbidity and mortality of housed animals.

Disinfectants that can be used to disinfect water and water pipelines: 
- halogen compounds (chlorine, iodine),
- oxidizing agents (hydrogen peroxide, peracetic acid),
- organic acids (acetic acid, propionic acid),
- quaternary ammonium compounds (benzalkonium chloride).

The mechanism of action of chlorine preparations is based on the action of active chlorine on organic substances and bacteria not only by means of oxidation, but also chlorination. Chlorine disrupts the integrity of the bacterial cytoplasmic membrane, leading to disruption of cell permeability and disruption of cell function, leakage of RNA and DNA proteins, and also affects the activity of enzymes. In addition to active action on nucleic acids, there are also the reactions with ribosome proteins - oxidation of amino- and imino- groups to form chloramines. Furthermore, the sulfhydryl groups of the proteins oxidize to form disulfides, which results in the formation of granules in the cytoplasm. However, chlorine by-products have a negative effect. It is mainly the formation of trihalomethanes (chloroform, dichloromethane, etc.), which have a potential carcinogenic effect when used in long-term and they also affect the central nervous system. Similarly, the relationship between chlorination of water and increased incidence of cardiovascular disease has been reported in the literature. Another disadvantage of chlorine is that it practically does not affect viruses.

The use of inorganic chloramines for the purpose of sanitation of potable water is advantageous especially where there is a retention time of potable water between the waterworks (or the last place of water chlorination) and the point of collection (in stables). During this long period of time, chlorine could be completely decomposed - water would no longer be secured against contamination in the water pipeline. Inorganic chloramines are more stable, so a slower decrease in the concentration of active chlorine in drinking water can be expected. Another advantage of chloramination of potable water is that chloramines produce incomparably lower haloform concentrations when reacted with haloform precursors compared to chlorine alone. On the other hand, inorganic chloramines are a weaker disinfectant than chlorine (or hypochlorous acid) alone, so their use is possible only for sources with less contents of bacteria.

Iodine has a unique position among disinfectants, thanks to its intensive, rapid action on all microorganisms at a relatively low toxicity. Active iodine is characterized by its reaction with complex-forming non-ionic surfactants in water to form iodophors, which simultaneously have disinfectant and cleansing effects. 
The mechanism of action of most oxidizing agents (e.g. hydrogen peroxide, peracetic acid) is based on the cleavage of atomic oxygen, which breaks molecular bonds and thus probably irreversibly inactivates enzymes. The advantage of the disinfectants based on of oxidizing agent is the fact that they act not only on vegetative forms of bacteria, but in higher concentrations also on spores and non-enveloped viruses. 

Chlorine dioxide has a long-term disinfecting effect, it removes biofilm, it does not cause sensory changes of water and does not form trihalomethane, nor does it react with ammonia to form chloramines. However, since it cannot be stored in compressed form as chlorine, it must be prepared on site. The mechanism of action of chlorine dioxide is, firstly, in the disruption of protein synthesis of bacterial cells, and secondly in the disruption of outer membrane of gram-negative bacteria. The main target for its action on viruses is their protein envelope. 
Other oxidizing agents, such as potassium permanganate and hydrogen peroxide, have not found wider application in practice.
The disinfecting effect of organic acids is mainly caused by their ability to denature proteins. In addition to the peracetic acid mentioned above, boric acid is today mainly used. 1% acetic acid and other organic and inorganic acids also have microbicidal effects. They change the pH of the environment, and low pH consequently has an inhibitory effect on bacterial growth. They also removes deposits and limescale as well.

The bactericidal effect of quaternary ammonium compounds is due to the permeabilization of cell membrane. Their effect is virtually cancelled by anionic surfactants (soaps), so quaternary ammonium salt formulations must not be combined with other cleaning agents.
Ozone and UV radiation can also be used to disinfect water. Ozone is a colourless gas with a characteristic odour produced by UV rays. It is the strongest oxidizing agent that destroys both bacteria and viruses. The mechanism of action is the formation of free radicals in the aquatic environment. It affects the permeability, enzymatic activity and DNA of bacterial cells. In viruses, it damages their nucleic acids and also protein envelope. It also has an oxidizing effect on organic substances present in water. Organic epoxides can form during ionization, alkylating agents that have been identified as genotoxic and carcinogenic substances. In spite of that, ozone is considered more effective and safer than chlorine. In addition, brominated by-products, such as bromates, that have carcinogenic effects, may be formed when water containing bromide ions is ozonized.

UV radiation is part of the electromagnetic spectrum located between X-rays and the visible part of the spectrum (wavelengths of 200-400 nm). The wavelength of 254 nm is most effective. The mechanism of action is to damage nucleic acids in microbial cells. UV systems use mercury lamps enclosed in quartz tubes around which water flows. 
When UV radiation is applied, reactivation of microorganisms can occur (the process of recovery of the cells damaged by UV radiation). Some microorganisms are not capable of reactivation (e.g. Bacillus subtilis, Haemophilus influenza etc.), others may repair (e. g. many enterobacteria, streptococci, micrococci, saccharomycetes, fungi, etc.). Under certain wavelengths and suitable environmental conditions, nitrates or formaldehyde may be formed during UV disinfection.

Summary
The supply of drinking water to poultry farms is an important area that needs to be adequately addressed in considering level of farm hygiene. The procedure for cleaning and disinfecting the watering systems must always be prepared individually for each farm, based on the specific conditions and level of contamination of the watering systems, in direct dependence on the abundance and quality of the sources of drinking water. The disinfection alone of technological systems for watering on the farm is not able to ensure the removal of scale and biofilm from the piping of the watering systems.

The importance of cleaning the watering systems can be seen in the following areas:
- promoting the operational reliability of watering systems,
- mechanical removal of micro-organisms,
- removal of nutrients for micro-organisms,
- a prerequisite for optimum efficiency of subsequent disinfection.
- The importance of the disinfection following the cleaning of watering systems can be seen in the following areas:
- devitalization of micro-organisms in watering systems,
- ensuring the microbial quality of drinking water. 

The paper was elaborated within the project NAZV QJ1530058, based on the results of cooperation with Tekro spol. s r.o. Prague.