Water quality generally refers to the mineral composition, pH, and bacterial contamination of drinking water. Minerals most commonly found in ground and surface waters are sulfates, chlorides, bicarbonates, and nitrates, which form salts with calcium, magnesium, or sodium. The combined concentrations of these minerals are called total dissolved solids (Patience, 2012). The potential for water quality issues increases with heavy applications of fertilizers to fields, contamination of run-off water by animal wastes, and severe drought. Pigs are typically adaptive to a wide range of water quality, but concerns arise with elevated levels of sulfate, nitrate and nitrite in the water source.
Sulfates are a common cause of water quality problems. Sulfates are of special concern because of laxative effects. As a result, pigs consuming water with high levels of sulfates typically have diarrhea. Growth and reproductive performance do not seem to be adversely affected unless extreme levels of sulfates are present in drinking water. Recommended maximum sulfate level in water is 1,000 ppm (NRC, 2012).
Nitrates and Nitrites
In water, nitratesare converted to the toxic compound, nitrites. Nitrites impair the oxygen-carrying capacity of the blood by reducing hemoglobin to methemoglobin. As a result, nitrites toxicity causes low oxygenation of tissues and results in signs of cyanosis and difficulty breathing. Recommended maximum level in water is 100 ppm of nitrates plus nitrites nitrogen (NRC, 2012).
Total Dissolved Solids
Total dissolved solids (TDS) is a measure of the total minerals dissolved in a water, which is also referred to as water salinity. As many elements contribute to TDS, further analyses need to be conducted to determine specific mineral contaminants in the water. Pigs consuming water with high levels of TDS have transitory diarrhea, but health, growth and reproductive performances are not usually affected. Recommended maximum TDS level in water is 3,000 ppm (NRC, 2012).
Hardness is the level of calcium and magnesium in the water. Water hardness contributes to the formation of scale deposits that can lead to accumulation of scale in the water system, causing nipple drinkers to become blocked. Water is considered soft if the concentration of calcium and magnesium is below 60 ppm and hard if above 120 ppm (NRC, 2012).
pH is the measure of water acidity or alkalinity. Most water sources are within the acceptable pH range of 6.5 to 8.5 (NRC, 2012). Acidic water (pH lower than 5) can create corrosion and cause damage to water lines. Basic water (pH above 9) can form scale deposits and block the nipple drinkers. Moreover, water pH influences the dispersion of medications used via water application and influences proliferation and survivability of pathogens. Basic water (pH above 7) is considered a risk factor for E. colidiarrhea and water pH should be controlled if diarrhea is a problem.
Water contamination by bacteria is estimated by measuring the level of coliforms per milliliter of water. Recommended maximum level of coliforms in the water is 50 CFU/ml (NRC, 2012).