Glen W. Almond
College of Veterinary Medicine
North Carolina State University
Raleigh, NC 27606


Water is the single nutrient required in the greatest quantity by animals. Pigs require water for a variety of reasons, including most metabolic functions, adjustment of body temperature, movement of nutrients into the body tissues, removal of metabolic waste, production of milk, and for growth and reproduction. In fact, 80% of the empty body weight of the newborn pig and about 53% of a market hog is water. An animal can lose practically all its fat and over half of its protein and yet live, while a loss of one-tenth of its water results in death.

Pigs consume the majority of their water by drinking. However, some water is ingested in feed and metabolism also generates water. The pig loses body water via urine, feces, respiration and from the skin. The balance between water intake and water loss is affected by numerous factors including health status, nutrition and the environment. It should be obvious that there is no simple answer to the question "How much water do pigs need?". Surprisingly, few studies have directly addressed the question and many investigations erroneously equate water use or water consumption with water requirements. The primary aims of this paper are to provide useful guidelines for water delivery and to illustrate the importance of management to adapt water delivery to the specific and changing needs of the pig.

Water Requirements of Pigs

It is necessary to recognize that there is no single water requirement for a species or an individual; the amount of water consumed depends upon factors such as temperature, diet, frequency with which water is provided, housing and stresses in the environment. A summary of water requirements of the pig are provided in Table 1. These values are based on the requirements of pigs in a thermoneutral environment and under ideal conditions. It is difficult to maintain pigs in such favorable conditions in commercial farms. Producers must adjust water delivery to meet the needs of the pigs in their unique farms and facilities. Most water delivery systems currently used in North Carolina offer little opportunity to adjust flow rates, nor do the systems meet the demands of individual pigs. Consequently, a certain percentage of animals in each pen and barn do not receive sufficient water to meet their needs. The precise water requirements of the boar previously have not been examined. Values are extrapolated from requirements of sows of similar body weight.

Table 1. Water requirements of pigs. Values (liters/day or gallons/day) indicate the range of requirements as presented in the literature.

Class of Pig
Nursery pigs (up to 60 lbs BW) 2.8
2.5-3.0 L/kg of feed consumed
0.3 gal/lb of feed consumed
Grower Pigs (60-100 lbs BW) 8-12
2.5-3.0 L/kg of feed consumed
0.3 gal/lb of feed consumed
Finishing Pigs (100-250 lbs BW) 12-20
2.5-3.0 L/kg of feed consumed
0.3 gal/lb of feed consumed
Nonpregnant gilts 12 3
Pregnant sows 12-25 3-6
Lactating sows 10-30 2.5-7
Boars 20??? 5???

Factors Affecting Water Requirements and Intake

Pigs affected with diseases require more water than healthy pigs of the same age and body weight. For example, water loss associated with diarrhea or increased water demands of an animal with a fever change the water requirements of a sick pig. These special needs are often overlooked on commercial farms. Increased water intake is difficult for a pig to achieve in large pens with numerous pigs or when water supply is intentionally restricted by certain water delivery systems (eg. intermittent water delivery in troughs for gestating sows).

Water demand will increase in proportion to the crude protein of the diet. Thus, 3.9 and 5.3 liters of water were consumed daily by nursery pigs fed 12 or 16% crude protein diets, respectively. The influence of added artificial lysine to the diet on water intake has not been addressed and unpublished studies indicate that pigs consuming a pellet ration have greater water demands than pigs eating a diet fed as meal. Higher salt or potassium intake increases the demand for water. "Salt poisoning" is not generally a result of a toxic level of salt intake per se, but a disruption of the pig's water balance (ie, a disruption of water supply). Water starvation is more appropriate to describe this condition.

High ambient temperatures will increase water requirements, particularly sows and finishing pigs. The increased consumption coupled with increased urinary water loss is an effective mechanism by which pigs lose body heat. A change in ambient temperature from 54-60oF to 86-95oF gives an increase of >50% in water consumption. These higher requirements may be met by supplying water at the high ranges given in Table 1. When pigs are fed ad libitum, a reduction in feed intake is a typical response to high temperatures. The decreased feed intake lowers the animals' need to eliminate metabolic heat. Fortunately, the diurnal pattern of high ambient temperatures allows pigs to consume feed during the cooler parts of the day. Evaporative cooling devices also are useful to reduce the impact of high temperatures on feed intake. One interesting observation is that at high ambient temperatures, pigs will consume almost double the quantity of cool (50oF) water than the amount of warm (80oF) water.

It is an accepted industry procedure to provide 4-6 lbs of feed to gestating sows. This restricted feed intake is usually matched by increased water intake (assuming sufficient water is available). The extra water intake is presumed to occur by the animals' attempts to gain abdominal fill.

Influence of Water Intake on Health, Growth & Production

Growing/Finishing Pigs:

Results of various studies, designed to evaluate water delivery rate on performance, are somewhat conflicting. This variation in results is due to the numerous confounding factors involved in the experimental designs (ie, number of pigs/pen, ambient temperatures, diets, etc). Tables 2 and 3 provide some insight to the influence of water delivery on performance. These tables have been modified to show the major differences.

Table 2. Influence of water delivery rate on performance of weaned pigs from 3-6 weeks of age (Barber et al., 1989).

Water Delivery
Rate (mL/min)
Water intake (L/day)
Feed intake (g/day)
Daily gain (g)
Time drinking (min/day)

The study by Barber and coworkers was conducted with pigs housed in a thermoneutral environment (83oF). All values, with the exception of FCR, differed (P<.01) between treatments.

Several other studies examined water delivery rate on grower/finishing pigs. Some of the results from one of more comprehensive studies are given in Table 3. These results showed that a higher flow rate was useful in maintaining pig performance when the ambient temperature was 95oF. When pigs were exposed to cooler ambient temperatures, the higher flow rates were detrimental to performance.

Table 3. Influence of water delivery rate and environmental temperature on performance of pigs from 10 to 14 weeks of age (Nienaber and Hahn, 1984).

House Temperature
40º F
95º F
Water flow rate (mL/min)
Water intake (L/day)
Feed intake (kg/day)
Daily gain (g)
Drinking time (min/day)

It is important that producers consider the experimental design and commercial applicability of the research results. Most studies used fewer than 12 pigs/pen and the typical duration of the studies was less than one month. Commercial farms rarely house so few pigs in one pen and competition for water nipples presumably is a factor that will influence water and feed intake. The number of pigs/water nipple is also a source of debate. One study indicated that one nipple/16 pigs (4 wks of age) had minimal influence on performance but the weight variation between pigs was significantly increased. Obviously, this weight variation will have a major influence in sort loss and uniformity. Other investigators suggest that the best performance and uniformity were achieved with one nipple/5 pigs.

It should be clear that additional research on the influence of flow rates and numbers of nipples/pen needs to be conducted with long-term (the entire finishing period) studies with commerical swine units. The popularity of liquid-feed systems in the United Kingdom are based on the reduction of waste and improved feed utilization. Perhaps some consideration and research on liquid-feed systems would be appropriate in North Carolina.

Lactating and Gestating Sows:

Most studies of water consumption by lactating sows have established voluntary intake levels and not the absolute requirements. Reported water intake by lactating sows ranges from 8 to 25 liters (2-6 gals)/day/sow. Litter size (milk demand and production), ambient temperatures and quantity/quality of feed intake can influence water consumption. Conversely, reduced water intake will decrease feed intake, milk production and pig performance. The most dramatic influence by water intake on milk production is evident in the first 3 days of lactation. Restricted flow rates (ie. < 0.5 liters/min) in later lactation lead to lower feed intake by the sow with significant weight loss; however, piglet survival and weight gain are seemingly unaffected. The sow weight loss and condition may play a more important role in her post-weaning reproductive performance. A flow rate of 1.0 liters/min evidently is sufficient to meet the sows' demand for water. Despite support for the forementioned recommendations, the water requirements of sows in a typical North Carolina summer have not been addressed.

Water consumption by gestating sows was reported to be between 2 and 5 gals/sow/day. Limited information was available on the potential influence of water delivery system on the health of gestating sows. We recently completed a project, funded by the NCPPA, designed to evaluate the role of water delivery system on the incidence of urinary tract infections in gestating sows. Four systems were evaluated in this study; (1) gestation crates with a nipple in each crate, (2) gestation crates with intermittent water delivery (15 mins every 2 hours) in troughs, (3) gestation crates with a level trough (6" deep) filled three times a day and (4) pen gestation with two nipples (6 sows/pen).

In summary, it was evident that the nipples in gestation crates provided the most optimal system in regard to minimal urinary tract infections. The traditional and popular trough with intermittent water delivery severely compromised the health of gestating sows. The other systems were intermediate. Perhaps the best explanation for these differences was that the nipples provided sufficient water to meet the needs of individual sows, regardless of age, parity, body weight and specific demands of each and every sow. In contrast, the provision of water at intermittent periods likely provided sufficient water for the healthy animals, but failed to the meet the needs of other sows. In fact, it was apparent that most of the water, provided to sows on an intermittent schedule, became nothing but wastewater in the lagoons. In cooperation with Dr. Jim Barker (Coll. Ag & Life Sciences), our group will conduct studies to evaluate the relative contribution of water delivery systems to wastewater in commercial swine units.

Summary and Conclusions

Water is generally abundant, inexpensive and not traded commercially. Therefore, limited research has been conducted on the role of water intake and use in commercial swine farms. This will change, as the cost of storing and handling waste water is a serious industry concern. Common sense dictates that producers should reduce the quantity of waste water without compromising the health and performance of their pigs.

As mentioned by Fraser and coworkers (1990), research on water requirements needs to look well beyond "average" values. The "average" piglet or the "average" sow does not become dehydrated or affected with cystitis. The difference between good and excellent management may rest on how well the system supports the atypical needs of the more vulnerable animals, without generating tremendous quantities of waste water.

Take-Home Message

Consider the different needs of the various ages/weights of pigs on your farm - ensure that these needs are being met by your water delivery systems.

Check the flow rates on all nipples on a regular basis (once a week and prior to the introduction of new animals to a pen or barn).

Don't take water for granted. Too little hurts your pigs, too much is a waste problem.

Suggested Reading and References

Barber J, PH Brooks and JL Carpenter. In: The Voluntary Food Intake of Pigs. Ed. Forbes JM, MA Varley and TLJ Lawrence. British Society of Animal Producers. Occasional Publication No 13. pp. 103-104. 1989.

Brooks PH and JL Carpenter. The water requirement of growing-finishing pigs: Theoretical and practical considerations. In: Recent Advances in Animal Nutrition. Ed. Haresign W. and DJA Cole. Butterworths; Boston. pp. 115-136. 1990.

Fraser D, JF Patience, PA Phillips and JM McLeese. Water for piglets and lactating sows: Quantity, quality and quandaries. In: Recent Advances in Animal Nutrition. Ed. Haresign W. and DJA Cole. Butterworths; Boston. pp. 137-160. 1990.

Nienaber JA and GL Hahn. Effects of water flow restriction and environmental factors on performance of nursery-age pigs. J. Anim. Sci. 59:1423-1429, 1984.

National Research Council. Nutrient Requirements of Swine. 9th Revised Ed. pp. 43-45. 1988.

Thulin AJ and MC Brumm. Water: The forgotten nutrient. In: Swine Nutrition. Ed. Miller ER, DE Ullrey and AJ Lewis. Butterworths-Heinemann; Boston. pp. 315-326. 1991.

Useful Conversions

2.2 lbs. = 1 kilogram (kg)
1 lb. = 454 grams (g)

1 fl. oz. = 29.5 milliliters (mL), 1000 mL = 1 liter (L)
1 quart 1 liter (L)
1 gallon = 4 quarts 3.8 liters