At the 2011 Allen D. Leman Swine Conference, Dr John Patience presented an excellent review on water quality issues and pork production. As he describes in the article, when it comes to measuring water quality for pork production, there are certain issues that are real, and there are others which are probably irrelevant. Most water quality criteria published for humans have little if any relevance to the pig. In addition, with the possible exception of microbiological contamination, human standards are lower, or much lower, than will be tolerated by the pig. Dr Patience recommends that when addressing water quality, the focus should be on the impact of the water directly on the pig, or the impact of water quality on the delivery system which in turn could impact the pig.

As the article outlines, water quality can be evaluated in terms of its physical, chemical and microbiological composition. The following points summarise the practical characteristics that producers should be aware of when examining water quality issues in swine facilities.

Physical Composition

Physical attributes tend to be of little practical importance in pork production. Pigs are quite tolerant of unusual colours and tastes in water, unless they are extreme. However, turbidity, colour and odour can be symptoms of other problems that may need attention.

Turbidity

• Turbidity is a measurement that is more qualitative than quantitative for pigs. High turbidity may result from suspended material in the water, such as silt or clay. It may also be due to suspended micro organisms, which are of greater importance.
  
  
• If the water has a turbidity of less than 5 NTU’s (Nephelometric Turbidity Units), it is probably acceptable for pigs.
  
  
• If turbidity is above 5 NTU’s, additional measurements of chemical and microbiological content of the water should be undertaken to determine their cause.
  
  
• Clay or silt suspended in water, which results in elevated turbidity, could lead to problems with the water delivery system, may impact the effectiveness of sand filters and also impair the effectiveness of water disinfection.

Colour

• Colour, measured in TCU’s (True Colour Units), is not a concern for drinking water supplied to the pig, unless the colour is due to an undesirable contaminant in the water.

Odour

• Odour, measured in TON’s (Threshold odour Number), is not an issue for pigs.
  
  
• Fresh water should be almost free of any odours; however, if present, the cause of off-odours may be important, and would require further analysis.
  
  
• The most likely cause of off-odours would be microbiological contamination or the presence of organic compounds.

Chemical Composition

Total dissolved solids (TDS)

• While not precise, TDS is still used as a means of determining the suitability of drinking water for swine. Total dissolved solids are due mainly to the presence of bicarbonate, chloride and sulphate salts of sodium, calcium and magnesium.
  
  
• Generally, if TDS is low (i.e. below 1,000mg per litre), mineral contamination is not an issue and no further testing is required.
  
  
• If TDS is between 1,000 and 3,000mg per litre, then it could cause transient diarrhoea, particularly in young pigs. This is often the case if the predominant anion in the water is sulphate.
  
  
• TDS between 3,000 and 5,000mg per litre is likely still acceptable but needs to be watched carefully, and over 5,000mg per litre must be carefully examined before being fed to pigs.
  
  
• Pigs can adapt to a wide variety of water qualities, but the best option is always to select the water with the lowest TDS, if a choice is available. If TDS is high, further analysis of the water is required to determine its composition, as some minerals are of greater concern than others.

Conductivity

• Conductivity is a measure of the ability of the water to conduct an electrical current.
  
  
• High conductivity suggests a high level of dissolved mineral ions in the water and is an indication that additional analyses are required, to determine the exact ions present.
  
  
• TDS is a preferred assay over conductivity because it is a direct measure of total inorganic contaminant content of the water.

pH

• pH is a measure of the acidity or alkalinity of the water. The vast majority of water will fall within the acceptable range of 6.5 to 8.5.
  
  
• If the pH is elevated, it can impair the effectiveness of chlorination. If the pH is low, certain water medications may precipitate out.
  
  
• The addition of pH modifiers to the water will interact with certain pharmaceutical products, so great care must be taken when administering both via drinking water.

Hardness

• Is a measure of the multivalent cations in the water, primarily calcium and magnesium as carbonates, bicarbonates, sulphates and chlorides and is generally expressed as calcium carbonate (CaCO₃) equivalents.
  
  
• Hardness has no known impact on health but it does impair washing due to an increased requirement for soap or detergents.
  
  
• Hardness can also lead to the accumulation of scale in water delivery, treatment and heating equipment and therefore can lead to problems with water heaters, nipples drinkers, filters, etc.
  
  
• The United States Geological Survey considers water soft if hardness is <60mg per litre as CaCO₃ and considers it very hard if it is >180mg per litre as CaCO₃.

Sulphate

• Is a naturally occurring mineral in most groundwater sources but is usually low in concentration and does not cause any problems with pigs. In general, sulphates less than 500mg per litre should be of no concern.
  
  
• In some instances, sulphates can exceed 1,000mg per litre or even 1,500mg per litre. While the intestinal tract of the pig can absorb sulphates, they are often re-secreted back into the large intestine, resulting in an osmotic, or non-pathogenic, diarrhoea.
  
  
• Depending on the level of sulphates in the water, pigs can adapt over a period of weeks so that associated diarrhoea is transient. The problem is the greatest in newly-weaned pigs, as they have not been exposed to sulphates and are perhaps physiologically more susceptible.
  
  
• Some bacteria can extract the oxygen from sulphate, leaving H₂S or HS as the residue; H₂S creates the &lsquotrotten egg’ odour that sometimes exists in water samples.

Iron and manganese

• There are no known direct health issues associated with elevated iron and manganese in drinking water but even at low levels, they can cause water handling problems.
  
  
• Iron and manganese tend to be present in ground water in their reduced form (e.g. ferrous, Fe+2) and thus are soluble. As water is extracted and exposed to oxygen, they are oxidised (eg. ferric, Fe+3) and rendered highly insoluble.
  
  
• Oxidised iron is typically a reddish–brown hue, while manganese tends to be dark and almost black. If present in the water, they can be seen as persistent discolouration of toilets and sinks but more importantly, coat water heater elements, drinker nipples, chlorinators, etc. Iron should not exceed 0.3mg per litre although staining can occur at levels as low as 0.1mg per litre. Manganese should not exceed 0.05mg per litre.
  
  
• Iron in the water can also support the growth of iron bacteria. These organisms can cause foul odours and reduce well water output. This is caused by the accumulation of bacterial slime in the water or along the well casing.

Nitrates and Nitrites

• Nitrates and nitrites are a particular concern in human drinking water, because they bind haemoglobin, reducing its oxygen–carrying capacity and form methaemoglobin.
  
  
• Experiments with swine suggest that nitrate guidelines for humans probably do not apply to pigs after weaning.
  
  
• The recommended limit of nitrates plus nitrites in drinking water for swine is 100mg per litre and nitrite alone should not exceed 10mg per litre. Drinking water for humans is recommended to contain no more than 10 per cent of these levels.

Sodium

• Sodium by itself is not a concern in drinking water unless it is at levels that exceed the kidneys’ ability to handle (i.e. brine). Such levels would be exceptionally difficult to find in drinking water.
  
  
• However, cations like sodium are associated with an anion in the water. If this anion is sulphate, it will lead to diarrhoea. Sodium sulphate, also known as Glaubers salts, is a powerful laxative. If the cation is chloride, there is little cause for concern, and if the cation is carbonate or bicarbonate, the water may have a higher pH.
  
  
• It is important to note that simple ion-exchange water softeners replace calcium and magnesium with sodium, and will elevate the levels of sodium in the water.

Magnesium

• Magnesium by itself is of little concern in the water. Like sodium, it is associated with an anion; if the anion is sulphate, it is called Epsom salts and is a potent laxative.

Chloride

• Chloride is not normally elevated in either groundwater or surface water.
  
  
• If it is high (>400 mg per litre), it will give a metallic taste to the water which does not appear to affect the pig.
  
  
• If drinking water is high in chloride, the quantity of salt in the diet can be reduced. However, this can only be done if sodium is also elevated in the water, or a source of sodium other than sodium chloride (NaCl) is included in the diet.

Microbiological Composition

• The microbiological quality of water is often the primary issue in water quality discussions. The presence of pathogenic organisms in the water can lead to disease breaks in the herd and make it almost impossible to achieve the highest level of performance.
  
  
• Surface water is at greatest risk, due to the higher chance of contamination but groundwater can also contain pathogens.
  
  
• For example, water can contain bacteria such as E. coli, Salmonella and Shigella, viruses such as enteroviruses and protozoa, such as Cryptosporidium and Giardia. Also, certain algae in the water can lead to gastroenteritis.

The above points are only a small portion of the entire review. The remainder discusses methods of water treatment to correct some of the above issues and the effects of water, especially water high in sulphates, on pig performance. It is an excellent resource on water issues and well worth having on your shelf.

Patience, J.F. 2011. Water Quality Issues in Pork Production. Proceedings of the 2011 Allan D. Leman Conference. 157-164

February 2012