Water Intake in Dairy Cattle
Water makes up 80% of an animal’s blood, and 87% of cow milk. After oxygen, it is the most important part of a cow’s diet. Thus, an adequate supply of clean, fresh water is absolutely necessary for dairy cattle at all times. Water intake of cows is related to their size, age, activity, production and environment. It will also be affected by environmental and water temperature, humidity, availability and quality. The table below shows the estimated daily water consumption of dairy cows at different stages in their lives and at different lactation volumes,.
a - A result of cow’s environment and management
b - Typical consumption over a year on a daily basis under average agricultural conditions in Ontario, Canada.
c - The average milk production in 2006 for a Holstein dairy cow in Ontario was 33kg/day.
d - Approximately 15% of the milking-age cows present on a dairy farm could be considered ‘dry’.
Lack of water intake will reduce dry matter intake and milk production – even with ‘minor’ water problems, a cow’s production can drop by 10 to 20%. Water does not only come from drinking, but also from the moisture in a cow’s feed. Cows with very wet feed will drink less water, but overall, as measured on commercial dairy farms in the U.S.A, an average Holstein dairy cow needs about 1.8kg of water per 0.5kg of milk. So, a cow producing 25kg of milk a day needs to consume 90kg of water altogether, with some coming from feed moisture and some from drinking water. However, cows under heat stress, i.e. at temperatures greater than 20ºC will drink 1.2 to 2 times as much water than cows living in neutral temperatures and humidity. There are many ways to maximise the water intake of your cows. These include:
Maintaining adequate water pressure and availability.
Cows drink the most after feeding and milking, so water troughs should be close to feed troughs, easily accessible and full of clean water after feeding and milking.
Provide water at your milking parlour entrance and exit. Water at the entrance will help to alleviate heat stress, especially if cows are waiting in the heat of the day. Research has shown that cows drink up to 60% of daily water immediately after milking.
Make sure there is enough watering space for each cow. Research at Kansas state university indicates that, at the minimum, you should have enough watering space for 15% of your cows to drink at any one time. One cow needs approximately 61cm of trough space, so, for 100 cows in a single area or free stall barn, you should have 915 linear cm of water trough space. However, you might consider providing more troughs than this to ease congestion around water troughs, especially when they are located in the crossovers in free stall barns.
Check your troughs regularly for any malfunctions or other problems during the day.
Water troughs should be easy to drain and remove any sediment, e.g. by being equipped with non-return valves and an outlet.
The depth of water in the trough should allow cows to submerge their muzzles 2.5 to 5cm and drink water without gulping down any air.
Adding water to your total mixed ration, if that is the system on your farm.
A water content of 55% in your TMR should increase water intake and reduce sorting of feed.
Ensuring good water quality
Clean tanks at least once a week
Take water testing samples at the place where cows drink and test the water at least once a year.
Install water filters and/or add water softeners.
If you suspect that your water quality is affecting production, try an alternative water source for 2 weeks and observe the change in milk production – if production goes up, you need to change your water source.
High nitrate levels in the water can result in nitrate poisoning. It is difficult to treat water contaminated with nitrate – you would be better off correcting the contamination problem at its source, or finding a new water source altogether.
Ensuring water pH is correct.
Water pH should be between 5.5 to 8.5, with 7 as the ideal. A pH outside of this range can cause acidosis or alkalosis. Correct pH using neutralisation systems. High nitrate levels in the water can result in nitrate poisoning. It is difficult to treat water contaminated with nitrate – you would be better off correcting the contamination problem at its source, or finding a new water source altogether.
 Adams, R.S., et al. “Calculating drinking water intake for lactating cows.” Dairy reference manual (NRAES-63). Ithaca, NY: Northeast Regional Agricultural Engineering Service, 1995.  McFarland, D.F. “Watering dairy cattle.” Dairy feeding systems management, components and nutrients (NRAES-116). Ithaca, NY: Natural Resources, Agriculture and Engineering Services, 1998.  Water Intake Determines a Dairy Cow’s Feed Intake and Milk ProductionBy: Donna Amaral-Phillips, Ph.D. University of Kentucky College of Agriculture.  https://www.dairyherd.com/article/three-key-water-trough-placement-principles  http://www.milkproduction.com/Library/Scientific-articles/Housing/Water/