7 June 1996

CATER FOR WATER NEEDS

Last summers drought hightlighted the importance of efficient use of water. Greg Beeton of Dairy Research and Consultancy, based at Myerscough College, Preston outlines likely water needs

COW requirements for drinking water vary greatly and are linked to milk production, dry matter of feed, total dry matter intake, temperature and type of diet.

High-yielding cows require more water than low yielders. For each extra litre of milk produced at least 0.9 litres (0.2gal) of water is required.

As total dry matter intake (DMI) increases then drinking water needs also rise. Research has shown that average yielders require at least 4kg of drinking water for each kg of dry matter consumed.

Higher temperatures also increase water demand, as do diets containing alkali-treated feeds and mineral salts.

In fact dairy cow drinking water requirements may vary from 20 litres (4gal) to over 100 litres (22gal) a cow a day. The dairy cows at Myerscough College are fed parlour concentrates and a 26% DM grass silage. A survey showed an average water intake during housing of 61 litres (13gal) a cow a day.

Water for milk plant cleaning

Potable water (meets drinking standards) must be available for removing milk residues and for cleaning and disinfecting milking equipment.

Volume required depends on parlour make and design, cleaning system used and the frequency of milking.

As a guide between 14 (3gal) and 22 litres (5gal) a cow a day is required.

Water for milk cooling

Quantity of water required for use in a mains plate cooler system can be estimated from the quantity of milk cooled for the ratio of water:milk should be about 2:1.

Water for udder washing

Good management reduces the need but general requirement may be two litres (0.4gal) a cow a day.

Water for yard washing

At Myerscough College daily water use for washing down the collecting and dispersal yards, parlour and tank room using a high volume wash-down pump is 4140 litres (910gal). This equates to an average of 9l/sq m (108sq yd) of cleaning area a day or 23 litres (5gal) a cow.

Maximising water intake

Restricting water can reduce dry matter intake, milk yield and growth rate, and increase health disorders. It is, therefore, important to ensure optimum consumption and cow performance. Water intake will be affected by cow behaviour, supply and presentation of the water, water quality and water temperature.

How behaviour affects water intake

Cows normally drink between two and five times, and up to seven times in 24 hours. This drinking routine will vary slightly depending on whether the cows are housed or grazing, but in both situations similar peaks in drinking behaviour occur (see graph).

Competition between animals, especially at periods of peak demand, means less dominant animals fail to satisfy their water requirements. This, alongside the stress and bullying that may occur, will decrease production.

Cows are unwilling to walk more than 250m (273yd) for water. This is reduced further by extremes of weather, or lameness.

How to maximise intakes

Water supply must be adequate at peak demand times. So it is vital to monitor supply at that time. Peak demand is usually one to three hours after afternoon milking, a time when mains water demand may also be high from plant washing. Water companies will carry out a flow test to determine whether supply is adequate for peak demand.

A cow can easily drink 20 litres (4gal) of water a minute. An average supply of 15-20 litres/min (3.3-4.4gal/min) into a standard 1.8m (6ft) trough will not meet the demand of a large group of cows. Flow rates and, therefore, trough refill rate, can be improved by use of quality pipes of a suitable diameter and pressure specification, a higher gravity feed tank or a pumping system.

When supply is still inadequate for high demand periods then it could pay to install storage systems. These can be as tank systems or simply larger capacity troughs. Whats important is that supply is continuous at all times.

Troughs should be adequate for a minimum of 10% of the herd to drink at once. Total drinking space requirements for the herd can be calculated by allowing 6cm (2.4in) a cow, providing the flow rate is adequate. For example, 100 cows require 6m (20ft) of trough space. Remember that cows can often only use one side of a trough.

Aim for a maximum water height within the trough of 0.9m (3ft) from the floor. When too high then cows will lap at the water increasing intake times.

Avoid siting troughs in corners of fields or buildings where water cannot be drunk from all sides.

Also take care to provide enough troughs to reduce locomotion time in reaching them. At grazing the number of drinking points must complement the grazing system. Maximum grass use using rotational grazing will require increased water supply.

The provision of a concrete surround coupled with correct ball valve adjustment will reduce spillage, poaching and potential foot ailments.

Dont forget to provide water bowls in isolation or AI pens.

Water quality reduces intake

Quality is usually reduced by the presence of dissolved minerals or bacterial contamination. It can also be compromised by stray electrical voltage.

Alternative supplies to the mains can have variable quality. Research in Holland has shown that water from sources other than public supply can increase the incidence of mastitis.

Quality can be improved by filtration or ultraviolet treatments, and research in Israel has shown water intake is improved by charging the water magnetically. The result is increased mineral absorption and milk yields.

Tepid water for optimum intake.

During winter cows prefer heated water as opposed to water at normal mains temperature. Mains water readings taken in a cubicle house at Myerscough college show a range of 5-12C (41-45F).

Increased consumption of tepid water at 17-20C (63-68F) has been shown in Swedish and American research to increase DMI and milk yields.

The economics of heating water for cows will depend on individual heating systems and mains water temperatures. Where possible use recycled water from the milking system.

When a recycled supply of water is available, but insufficient for the whole herd, target the high yielders.

Peak demand for water is usually one to three hours after afternoon milking. Dont let water levels get too high in the trough. This will encourage cows to lap at the water, so increasing their intake time.

A cow can drink 20 litres (4 gal) of water a minute. Ensure troughs are large enough for at least 10% of the herd to drink at any one time.