Introduction

Although water is a critical resource for profitable livestock production, there has been surprisingly little research done to better understand how its use can be optimised. The lack of research on water and its use in swine production has been as a result of the fact that until recently, water supply in most parts of the world has been plentiful and inexpensive, and therefore easily taken for granted. It is for this reason that water has been described as the forgotten nutrient (Thalin and Brumm 1991).

Water can no longer be taken for granted mainly because access to good quality water is becoming increasingly limited, thus presenting major challenges to the growth and development of swine production in Canada. Also, poor quality water negatively affects pig performance and may encourage excessive water usage. The latter will create manure handling and disposal problems as a result of increased slurry volume (McLeese et al. 1992). Various factors including the concentration of dissolved minerals and bacterial contamination affect the quality of drinking water for livestock.

The response of pigs to these factors varies widely. Dealing with a water quality problem can be a major challenge and often water treatment does not correspond to improved animal performance. Furthermore, pig production in large scale provides abundant amounts of manure, which is increasingly contributing to environmental pollution and eutrophication of water bodies (Nyachoti et al. 2007). High concentration of water in the manure (86-98 per cent) increases the costs of storage and disposal (Mroz et al. 1995). Water in the manure originates mainly from excreted urine and this is closely related to water intake.

As the livestock sector becomes more aware of the fact that water is a critical resource for profitable production, it is critical that producers adopt water management strategies that will help conserve this resource. This review aims to update the information available on water use in swine production and to suggest best management practices for conserving water in commercial swine production facilities.

Why Pigs Need Water

Pigs obtain water from three sources: water contained in the feed, metabolic water and water consumed by drinking. They need sufficient quantities of water to maintain optimal production levels.

Water is the single largest constituent of the body, making up to 82 per cent of a young pig’s and 55 per cent of market hog body weight (Kober, 1993) and is also a major component of secretions made by the pig, e.g. milk and saliva.

The amount of water consumed by pigs varies depending on factors such as quality of the water provided, diet composition, physiological status of the animal, environmental conditions, social factors, and equipment design and placement. Interactive effects of these factors may also influence water intake by pigs. As a result, the recommended allowances of water for particular classes of pigs differ markedly (NRC, 1998), because of limited information on the underlying physiological mechanisms regulating water consumption and difficulties in establishing the impact of some extrinsic factors, such as ambient temperature, humidity, diet quality and quantity, frequency of provision, maintenance conditions or stress (NRC, 1998).

Furthermore, the conventional methods for establishing nutrient requirements cannot be applied directly to water since, in addition to the requirements for tissue maintenance, body growth, foetus development or lactation, the pig needs water in order to fulfill a number of other physiologically significant functions, namely thermoregulation, mineral homeostasis, excretion of metabolites and/or anti-nutritional substances, achievement of satiety and behavioral purposes (Mroz et al., 1995). Therefore, in practice, pigs are provided free access to water.

Sources of Water for Commercial Pork Production

Water for pork production in North America is derived from three main sources namely, well (ground) water, surface (dug-out) water and pipeline water (public supply).

Water quality from these sources varies as does their risks for contamination. Surface water sources have the highest risk of microbial contamination and are more likely to vary over time in mineral content, due to the contributions of run-off and the concentrating effect of evaporation. The risk of contamination declines progressively with cisterns, natural springs, shallow hand-dug or sandpoint wells (<50 ft), artesian wells, drilled wells, and public water supplies (Meek 1996).

Although pigs can tolerate a wide range of water quality, there is no information indicating use of recycled water for drinking purposes. Also, there is lack of information on the proportions of the various sources (i.e. wells water, pipeline water, dugouts) of water used in Manitoba hog operations.

The data shown in Table 1 provides a summary of nursery pig performance when drinking surface (dug-out) water or pipeline water in a large commercial facility. On the basis of this finding, and pending further research, it can be concluded that surface water can be used effectively for nursery pig production (Nyachoti et al. 2005). As the use of surface water for pig production becomes increasingly important, it is critical that its effect on animal performance be determined.

Water Quality Effects on Pig Performance

Pigs require a supply of good quality water for optimal growth and production performance. Performance indices such as mortality, feed intake, growth rates, feed efficiency and most critically, profitability may be affected by the quality of water provided (Stull et al. 1999).

When given poor quality water, pigs drink excess water, which in turn increases slurry volume (McLeese et al. 1992). This is undesirable because it adds to the growing concern of manure disposal within the livestock industry (Mroz et al. 1995) and increases the cost of applying manure on the land. Furthermore, because animals must excrete any excess water consumed, their performance can suffer as energy, which could otherwise be used for growth or production, is expended on water excretion (Mroz et al. 1995). Inadequate water intake as a result of poor quality is equally undesirable as it can lead to poor performance.

In general, the presence of chemical elements and bacterial contamination (including the specific type of bacteria) are the main factors that determine the quality of water for swine (Veenhuizen 1993). Table 2 lists standards for some chemical contaminants in livestock water as suggested by the Canadian Task Force on Water Quality (1987).

Chemical Factors Affecting Water Quality

Chemical factors affecting the quality of water include pH, hardness, total dissolved solids (TDS), nitrates and nitrites, sulphates, iron and lead (Kober 1993). Iron and lead, which may be of concern in relation to a piping problem, are not discussed. Each of these are discussed briefly below.

pH

Water pH ranging from 6.5 to 8.5 is considered acceptable to pigs (NRC 1998). A low pH (less than 6.5) is undesirable as it may corrode and dissolve metals from the plumbing and cause precipitation of medication delivered via water. High water pH (greater than 8.5), on the other hand, gives the water a slippery feeling and leaves scaly deposits (Kober 1993).

Importantly, a recent study demonstrated that altering water pH either significantly changed the state or precipitated 15 drugs commonly delivered in the water system for swine (Dorr et al. 2009). The implications include sub-optimal drug delivery, clogging of the medicators and waterlines and persistent drug residues in the system which could impact pork quality by causing deposits of drug residues in meat. Another practical problem with high water pH is that it reduces the efficacy of chlorine used for water treatment.

Although wide deviations in water pH are uncommon, practices such as liquid whey feeding (acidic whey) through the water system can dramatically reduce the water pH. Like many liquid by-products, which tend to be very variable, liquid whey pH should be routinely checked so that dilution is such that the water pH is within the tolerable range.

Hardness

Water hardness is a measure of the sum of divalent cations in the water, which for the most part in practical circumstances means calcium and magnesium salts. Other divalent ions in the water are quantitatively lower and therefore irrelevant to the determination of hardness. Water hardness is expressed as calcium carbonate (CaCO₃) equivalents (Kober 1993), although one needs to know the actual amount of calcium and magnesium to be able to predict how animal performance might be impacted.

Water with low levels (i.e. <60 ppm; soft water) has no effect on pig performance but excess calcium intake might interfere with phosphorus utilisation. Thus, dietary phosphorus levels may require adjustment when using water with high CaCO₃ (>300 ppm) levels (Kober 1993).

In pork production, the most significant practical problem associated with the use of hard water relates to the deposition of scales in the watering system, which causes serious water delivery problems and requires considerable labor resources to manage.

Total Dissolved Slids

Total dissolved solids (TDS; also known as the salinity of water), is the amount of soluble salts (commonly magnesium, calcium and sodium bicarbonate, chloride, or sulphate forms) in the water (Kober 1993).

Drinking water with less than 1,000ppm is considered safe while levels exceeding 7,000ppm are unsafe for any class pigs. At high levels (i.e. 1,000-5,000) water refusal or mild temporary diarrhoea might occur (Kober 1993; NRC 1998).

There is contradictory evidence as to the level of TDS at which pig performance is impaired. For example, growth rates, feed intake, and feed efficiency were better for weanling pigs fed water with 217ppm compared with water with 4,390 ppm TDS (McLeese et al. 1992; Table 3). However, TDS at between 1,000-6,000ppm have, generally, not been shown to consistently affect pig performance (Anderson et al. 1978). Furthermore, performance of growing-finishing pigs was not influenced by TDS levels up to 7,000ppm in the form of sulfates (Anderson et al. 1994). As the experimental period in this experiment was only four days, the long-term effects of high TDS levels on pig performance cannot be substantiated.

When water with high salinity is used, there might be merit in adjusting dietary salt levels but this should be done carefully to avoid a sodium deficiency. Because TDS is a very general descriptor of water quality, incorporating the sum of all mineral contaminants into one value, it is important to determine its composition to evaluate its potential impact on pig production if it exceeds 1,000ppm.

Nitrates and Nitrites

Contamination of groundwater with nitrates and nitrites mainly occurs through leaching from the soil or through surface water run-off that has been exposed to material with high nitrogen levels, e.g. animal wastes, nitrogen fertilizers, decaying organic matter, silage juices, soils high in nitrogen-fixing, etc. A high level of either nitrites or nitrates may be indicative of bacterial contamination (Kober 1993). Nitrites are 10 times more toxic than nitrates in monogastric animals (Emerick 1974). The Canadian Task Force on Water Quality (1987) recommends a limit for nitrite-nitrogen and nitrate-nitrogen at 10 and 100ppm, respectively, in water for livestock and poultry (Table 2). Symptoms of nitrate poisoning include high respiration rate, increased incidence of diarrhoea, reduced feed intake, poor growth, increased abortions among sows and reduced vitamin A utilisation (Meek 1996; Thacker 2001).

Water nitrates less than 1,500ppm (around 333 ppm nitrate-nitrogen) might not affect pig performance (Kober 1993) although a higher respiration rate was observed with the inclusion of 300ppm nitrate in water fed to weaned pigs (Anderson et al. 1978). In a survey conducted in the United States, high water nitrate-nitrogen was found to be negatively correlated to body weight and positively correlated to condemnations in broiler chickens (Barton 1996).

Sulphates

Of all mineral contaminants, sulphates are the cause of most water quality problems with respect to pig production in North America (NRC 1998). A survey by McLeese et al. (1991) found 25 per cent of Saskatchewan well water to contain more than 1,000ppm of sulphates. Plaizier et al. (2003) observed sulphate values ranging from 180 to 4,770ppm in water from Manitoba dairy farms, although 75 per cent of the farms had less than 210ppm sulphate in the water.

There is considerable inconsistency in the literature regarding the effect of water sulphate content on pig performance. According to Canadian Task Force on Water Quality 1987 (Table 2), a water sulphate level of less than 1,000ppm may not affect pig performance. Water with up to 3,300ppm causes a laxative effect and increases water intake in pigs. Higher levels cause diarrhoea and make water unsuitable for pigs (Anderson and Stothers 1978 Table 4; AAFRD 1993; Gomez et al. 1995; NRC 1998). Nonetheless, pigs may tolerate higher sulphate levels than poultry as drinking water with 3,000ppm had no effect on pigs weaned at 28 days of age (Paterson et al. 1979). However, studies conducted later suggest that water with less than 1,500ppm sulphate may affect performance of early-weaned pigs (Kober 1993; NRC 1998).

Water with 3,500ppm sulphate is unfit for sows and generally water with more than 4,500 ppm should not be used for any livestock (Kober 1993).

Sulphate in the drinking water will inevitably lead to diarrhoea in most classes of swine (Veenhuizen et al. 1992). Younger pigs are most susceptible but even sows will have a transient diarrhoea if rapidly switched to water high in sulphates. For young pigs, levels as low as 750ppm can be problematic, while older animals are tolerant of even higher levels. Because sulphate causes diarrhoea of an osmotic nature, care must be taken not to assume that performance is impaired. On the other hand, diarrhoea even of osmotic origins can increases the pig’s susceptibility to secondary causes of gastrointestinal disturbance that might have a much more profound impact on performance and health.

Bacterial Contamination and Water Quality

Bacterial contamination is currently viewed as a serious problem in water for both human and livestock use. The main types of bacteria that have been associated with water quality problems include Cryptosporidium, enterotoxigenic Escherichia coli, Salmonella and Leptospira (Meek 1996; NRC 1998; Thacker 2001).

The degree of water pollution by bacteria is traditionally estimated by measuring the level of coliforms, which represents a group of generally pathogenic bacteria, as an indicator (Meek 1996). A count of 5,000 total coliform per 100 millilitres is normally used as a guideline for maximal levels in water for pig production (Meek 1996; NRC 1998).

It must be emphasised, however, that the actual level that can impact on water quality will vary depending on the virulence of specific bacteria present. The effect of waterborne bacteria on pig performance is poorly characterised. However, studies with poultry have shown that the impact of bacterial contamination is worsened in water with higher contents of other contaminants.

Dealing with a Water Quality Problem

To ensure a supply of good quality water, regular monitoring is critical. At the minimum, water quality should be monitored at least once a year and should always include a measurement of bacterial (coliform) contamination (Kober 1993). Ideally, water test results should be used to adjust feed formulas to compensate for any excessive amounts of minerals supplied by the water (Flipot and Ouellet 1988). However, the challenge here is that the availability of many of the water minerals is unknown although one will expect that if a mineral is soluble then it is also available (Christensen 2001).

Because the levels at which pig performance is impaired by water contaminants varies widely, water analysis results alone may not be sufficient to justify changes in a production system. Therefore, any steps to institute water quality corrective measures should be guided by the impact the water has on animal performance (Veenhuizen 1993). This is particularly important because water treatment methods can be costly.

Water Treatment Techniques

Considerable resources are spent on water treatment, particularly in the nursery. Although in some cases pigs may be able to acclimatise to water of poor quality (Veenhuizen 1993), there are situations that the quality of the water is too poor to be utilised economically for pork production and therefore either an alternative source of water has to be found or the water has to be treated before use (Meek 1996).

A major challenge with respect to water treatment is to identify a suitable treatment system that is not only effective but also affordable. Various water treatment methods (e.g. chlorination, coagulation, filtration, and pH adjustment; Table 5) are available to the livestock industry, but their impact on animal performance is largely unknown.

Best Management Practices for Water Use in Pork Production

There is no question that good quality water is a critical resource for profitable pork production. Pigs must have access to drinking water to grow and reproduce. Also, the need to use water wisely in livestock production cannot be overstated.

Although research on water relative to other nutrients is limited, there is sufficient information on what producers can do to ensure that pigs have access to good quality drinking water at all times and to minimise the amount of water used in their operations. The latter is very important because in large swine production facilities, significant amount of water is used for cleaning pens and equipment, enforcing dunging habit, as cooling agent (sprayers and drippers), as a vehicle to move manure, and as a wetting agent for feed in wet feeding systems. The following is a brief outline of best management practices that could be used to achieve these goals:

Repair leaking water lines promptly

Water lines should be monitored routinely and leakage, however, small should be fixed right away. According to Dr Mike Brum, a drinker leaking at 90 drips per minute will waste around 29 litres of water a day! (Brum 2007). This has also been identified in many parts of the world as a major cause of water wastage in commercial hog production units (Gonzalez 2008).

Use a power washer to clean barns

The amount of water used for cleaning purposes can be substantial. Pre-soaking pig housing facilities to loosen dirt followed by use of power washing can help reduce the total amount of water used for cleaning. This is clearly illustrated by study reported by Hurnik (2003, Table 6); pre-soaking reduced the pen-washing time by 40 per cent.

The study also showed that the use of hot water when power-washing (without pre-soaking) will decrease the wash time by 15.8 minutes. However, when pre-soaking pens, wash time between cold and hot water can be significantly reduced, which offers an opportunity to use cold water in situations where it might be expensive to use hot water.

Choose drinkers that minimise water wastage

It has been known for a long time now that some drinker devices lead to more water wastage than others. In particular, nipple drinkers tend to lead to more water wastage than ball-bite nipple or bow drinkers. For example, at the 2007 Banff Pork Seminar, it was reported that on an Alberta farm, ball-bite nipples reduced the amount of water used for drinking purposes by growing-finishing pigs by up to 46 per cent compared with the standard nipple drinkers (McKerracher 2007).

Ensure that drinkers and water flow rates are set correctly

Drinkers should be positioned 10 to 15cm above the pigs’ backline to minimise the amount of water waste (Gadd 1988a). If set too low, the pig turns sideways to drink and up to 60 per cent of water flows out the other side of the mouth (Gadd 1988b). Water flow rate should also be set correctly; an excessive flow rate of 900ml per minute compared with a more conventional rate of 300ml per minute for 30- to 60-kg pigs produces an extra 78 litres of slurry per pig over 40 days (Gadd 1988a).

Use properly formulated rations

Dietary crude protein and mineral content in swine diets have major impacts on water intake levels (Thalin and Brumm 1991; Mroz et al. 1995; NRC 1998). When pigs are fed diets with a protein concentration that exceeds their requirements for maintenance and growth or production purposes, the excess protein is broken down and excreted as urea (NRC 1998). This process exerts an additional need for water to help in the excretion of the excess nitrogen, which explains why pigs consuming high protein diets have high water intake levels (NRC 1998). Lower protein diets, formulated to maintain the essential amino acids and therefore pig performance, may lower nitrogen excretion by 40 per cent (Smith and Crabtree 2005). As well, the accompanying decrease in water intake reportedly can decrease overall slurry volume by approximately 30 per cent (Smith and Crabtree 2005).

It is therefore critical that nutritionists take into account potential water wastage when relaxing maximum protein inclusion level to allow more DDGS (high protein ingredient) in their formulations. High salt (NaCl) intake also results in increased water consumption in all classes of pigs and this is associated with increased urine output (Nyachoti 2004).

Maintaining proper temperature and humidity conditions

Water requirements for pigs increase in hot environments due to the greater amount of water vapour that is expired from the lungs. Respiration is the major way that pigs cool themselves because they cannot sweat like other animals. It is thus very important that adequate supply of drinking water be available.

High humidity in itself does not have a negative effect on swine performance. However, combined with high temperatures, it enhances the negative effects of the high temperatures. Since the pig must rely heavily on evaporative heat loss to try to stay cool when it is hot, humidity level is very important. The higher the humidity level in the air, the less effective is the process of evaporative cooling (less moisture can evaporate into humid air than dry air). It has been estimated that at 30°C, an increase of 18 per cent in humidity is equivalent to an increase in air temperature of 1°C (Huynh et al., 2005). In a hot-humid environment, typical of Western Canada summer months, water as a cooling agent for pig becomes very important through the application of water sprinkler, fogging and dripping systems. Whereas numerous studies have shown these systems to be beneficial in maintaining pig performance in hot summers their use should not override provision of adequate floor spaces, insulation and ventilation as well as diet reformulation strategies (low fibre and high energy) as these might save on the amount of water used for cooling purposes and thus manure volumes in the long run. For example, studies at the University of Kentucky with finishing pigs (weighing around 50 to 110kg and with a space allowance or 10 square feet per pig) and conducted in two summers months of 1996 and 1997 (temperature range: 22 to 34°C) demonstrated importance of cooling (either by fan or sprinkler) on performance (Table 7; Cromwell 1999). Whereas combining fans and sprinkler resulted in better performance, data from the fan only suggests that having well insulated buildings with good air movement might be as good as or better than using sprinklers.

Animal management

Factors such as boredom, season of the year and the stage of the breeding cycle can influence the water needs of the pig and therefore potential wastage. For instance, group-housing gestating sows rather than confining them in individual crates may reduce boredom, which has been associated with excessive intake of water. Additionally, such factors as stocking densities in hot weather will affect the environmental temperature felt by the pigs and influence their need for water for cooling purposes.

Recovery of wastewater and recycling

Wastewater can be reclaimed for reuse purposes when conventional treatment is combined with advanced treatment technologies. However, according to a report compiled by Premium Standard Farms. among many, there are three major reasons why water reclamation for reuse purposes is not widely practised; 1) perception associated with direct or indirect reuse for human consumption; 2) the cost of advanced treatment necessary for wastewater reclamation, and 3) health concerns with the consumption of reclaimed water. Animal health concerns may be the most difficult challenge to overcome. If all of the wastewater is reused, the concentrations of dissolved ions, or total dissolved solids (TDS) will increase in concentration in the recycle loop over time. If allowed to build to levels higher than can be tolerated by the livestock, adverse health effects could occur.

Premium Standard Farms has conducted several wastewater reclamation demonstration projects using a conceptual flow diagram for a water reuse system as shown in Figure 1.

Using this model several preliminary studies have been conducted under experimental conditions by Premium Standard Farms to determine the feasibility of recovering water from animal waste, removing nutrients, coliform/pathogens, and reusing the recovered water for drinking by pigs. In those studies there was no evidence of any performance reduction or other adverse animal responses to the inclusion of a significant portion of the drinking water as recycled water from animal waste (Bull et al., 2005).

Other studies conducted or ongoing at the University of North Carolina have evaluated similar and other technologies for recycling waste water. These include collecting water from an aerobic digestion pond, removing solids and then filtering through sand or membrane filtration followed by chlorination. While such methods show definite promise, a number of challenges need to be overcome and the cost effectiveness has yet to be confirmed. In Manitoba, limited efforts towards recycling of waste water have been made, and mostly directed towards recycling the water for washing purposes rather than for animal consumption. Similarly, in Ontario, commercialisation of a waste water recycling technology for washing purposes is being attempted (Nutrient Management technologies Ltd website), but again, it is directed towards very large hog operations and the economic feasibility is questionable.

Moving waste with minimal or no water addition

A strategy to minimise water use in hog operations is to reduce the amount to of water needed to move the manure from the barn to storage facilities. To achieve this goal, various technologies have been tested but it is not clear whether these are currently used in any system within Manitoba or anywhere else in Canada.

An example of these technologies is a system demonstrated by research at North Carolina University. The basic principle underlying this technology is that urine is separated from faeces and that the faeces are swept away from the barn using conveyor belts underneath the slatted floors. Thus, the amount of water required to move the waste is drastically reduced and because of the drier nature of the manure, nitrogen loss through volatilisation is reduced and the cost of transporting the manure is also reduced. There may be other examples of these technologies but as indicated their use in the Manitoba swine industry is unclear.

Solid manure housing systems

The large majority of swine operations in Manitoba, as in the rest of North America, are based on slurry manure systems. Solid manure systems are used primarily by smaller operations and/or those looking for alternative systems.

The greatest advantage of solid manure systems from a water usage standpoint would be the elimination of the water requirement for flushing or moving the manure. There may be some decrease in wash water but in any facility, the need to wash and disinfect thoroughly between batches of pigs would still be required.

There are a number of solid manure system concepts available – an example is the alternative hog barn at the University of Manitoba – most of which have the pigs directly on bedding, which is seen to require more labour and more space per pig to maintain properly.

One option studied in the United States evaluated a two-storey hog building whereby the animal excrement falls through the slotted floor where it is collected onto a dry bulking agent (e.g. sawdust, straw, shredded newspaper), stored and treated before removal. This unique design, which incorporates traditional confinement production practices including slotted flooring, incorporates manure composting within the facility and was considered most appropriate for areas with limited local land base for manure application. While the concept has many positive attributes, it has not seen wide adoption by the swine industry. There are likely several reasons for this; economic viability being one deterrent not fully assessed.

In general, adopting solid manure technologies for most current production systems would be cost prohibitive. Although there may be a place for such technologies, with the right available resources, for new construction there is minimal research to support the viability and management strategies necessary for such enterprises to be economically viable.

Summary and Conclusions

In a modern swine operation, water is mainly used for drinking by the animals, cleaning the barns, enforcing dunging habits, sanitising equipment and in liquid manure systems, for flushing or moving the manure to the storage site.

The quality of drinking water for pigs and poultry varies widely depending on the concentration and type of contaminant in question. Although pigs can acclimatise to some water quality problems, there is no doubt that poor quality water can negatively impact on performance. For most water contaminants, there is not a single level at which performance is impacted. This is partly due to the fact that effects on animal performance at any one level vary depending on the presence of other contaminants. Therefore, whenever assessing water quality problems caused by a specific factor, consideration for other factors present is critical. As water systems are increasingly becoming important in the administration of drugs, water quality factors which might affect the drug efficacy assume importance.

There are a number of management practices that can reduce the total fresh water usage. These include: use of waterers that reduce wastage, correct diet formulation, use of housing design and management strategies that minimize the need for routine use of the sprinkler systems for cooling. Possibility of using technologies which maximise whole farm water usage efficiency such as solid manure handling and water recycling might become attractive as means of conserving water in the future. The National Centre for Livestock and the Environment (NCLE) at the University of Manitoba has an alternative swine barn whose principle is based on manure solid manure management. This initiative along with the hoop shelter concept highlights potential for conserving water usage/wastage through minimising water requirement for flushing or moving manure. It is no doubt that the NLCE which is focused on sustainable animal production systems is a pivotal research resource to provide water conservation strategies applicable in swine production in Manitoba.

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Further Reading

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You can view the other papers presented at the Manitoba Swine Seminar 2010 by clicking here.