Because it is all around, we tend to take water for granted. Nevertheless, water is the most important essential nutrient supplied to dairy cattle. Water intake can be affected by various factors such as milk production, dry matter of the ration, sodium intake, and ambient temperature. It is a good thing to keep in mind that 87 percent of the make up of milk is water. A typical dairy cow can consume an average of 115 litres of water daily. A cow can fulfill up to sixty percent of her daily requirements in the hour following milking. It is therefore critical that water availability be adequate. A cow can ingest up to 16 litres of water per minute when she has access to a water trough. Flow rates in water bowls should be monitored to make sure that the delivery rate is at least 4 litres per minute. Behaviour studies have shown that cows will spend less than 30 minutes a day drinking. High producing cow are known to absorb up to 160 litres of water during that short period of time and so, good access to water and adequate flow rates are key. One should remember that in tie-stall barn designs, just after milking, many cows will be drinking at the same time and the last bowl on the line should deliver as much water as the first one. In order to achieve this goal, delivery pressure and size of piping are critical.
The longer the waterline, the less the pressure and flow rate will be at the end. Similarly, the smaller the diameter the pipe, the faster the pressure and flow will drop along its length. This is why it is important to avoid any restriction on the line, especially close to the pump, since it will have an impact on the downstream system. Remember, the water pump is the heart of the system and should be chosen according to the pressure and flow rate required. It also be inspected and serviced regularly.
Water pipes should be checked for clogging regularly, especially if the delivery system is made from galvanized pipes. Hard water, a high level of iron or manganese can contribute to the premature clogging of the system. A clogged system will provide much less water per minute to the cows and can be the sole reason for low milk production. For example, let's compare two pieces of one inch diameter pipe. One pipe is clean and clear from obstruction and the other is clogged and only _ of the original diameter remains. At equal pressures, the unclogged pipe will provide 15 times more water per minute that the clogged one.
Water bowls and water troughs should be cleaned regularly to make sure that water consumption is not affected simply by deficient hygiene.
If water intake, feed intake, and animal performance are sub-optimal; careful evaluation of the quality of water should be initiated by conducting a laboratory analysis for anti-quality factors (constituents in excess or unwanted compounds). Anti-quality factors that may affect water intake and animal performance include: total dissolved solids, sulfur, sulfate, iron, manganese, nitrate, toxic compounds (e.g., heavy metals, pesticides), and harmful microorganisms.
On most farms, water originates from privately owned wells; therefore, control for water quality resides in the hand of the producer. It is wise to have your water analysed regularly since there could be seasonal variations in the water quality.
Several factors are known to affect water quality for dairy cows such as total dissolved salts (TDS), sulphur, sulphate, chloride, iron, nitrate, manganese and fluoride. When in doubt about the quality of you water or the amount that your animals receive, do not hesitate to consult a specialist to get the full picture. After all, in terms of kilogram ingested per day per cow, water is at the top of the list!
Table 1. Maximum Acceptable Concentrations of Minerals, Mineral Compounds and Physical Properties