Water in Livestock and Poultry Nutrition: A Review on Consumption and Quality

Abstract

This review paper provides a comprehensive overview of the use of water in livestock and poultry nutrition, focusing on both quantitative requirements and quality standards. The review is based on the evaluation and synthesis of the published scientific literature addressing water intake, physiological functions, and quality parameters in farm animals. It summarizes the physiological roles of water in key metabolic processes and examines the primary factors influencing water requirements, including animal species, stage of production, and environmental conditions. Furthermore, the article compiles available data on water intake across major livestock systems and outlines the physicochemical and microbiological characteristics required to ensure animal health and food safety. Water constitutes a large proportion of body weight, ranging from 50% to 95% depending on species, and is essential for nutrient transport, thermoregulation, and waste elimination. Water requirements are highly variable and influenced by multiple interacting factors, such as ambient temperature, humidity, and dietary composition. Ensuring continuous access to adequate quantities of safe, high-quality water is essential for optimizing animal health, productivity, and welfare and should be integrated into routine farm management and regulatory frameworks.

1. Water in Livestock and Poultry Nutrition

Water is the second most essential nutrient, after oxygen, for sustaining life. Water content in adult livestock animals ranges between 50% and 70% of their body weight; in newborns and young animals it accounts for over 80% of total body weight [1]. Water is consumed in greater quantities than other nutrients and participates in various important physiological processes of living organisms [2]. Beyond its physiological importance, water use in livestock production has significant environmental implications. The livestock sector contributes substantially to global water use, with agriculture accounting for approximately 70% of freshwater withdrawals worldwide, while livestock systems represent an important share of this demand. Moreover, water intake in livestock production varies considerably across regions and production systems, reflecting differences in climate, management practices and resource availability [3,4].

In general, water deprivation is tolerated by animals less comfortably than lack of feed. If fasted, animals may lose virtually all body fat and up to 50% of body protein and nevertheless survive. In contrast, loss of over 20% of body water may lead to death [1,5]. Initial signs of insufficient water intake are thirst and body weight loss. If the problem persists, anorexia, reduction in milk production, indigestion, disorientation, decreased heart rate and blood pressure, dehydration, constipation (to complete disruption of defecation), decreased volume of urine and pyrexia may progressively develop. In severe cases of water deprivation, hallucinations and uremia may potentially develop in affected animals [6].

The quality of water consumed by livestock is also important. Water is an excellent solvent of various chemical elements and chemical associations and therefore toxic chemicals may be taken by animals, leading to adverse effects in these animals [1,7].

The supply of an adequate quantity of good quality water to livestock is essential for achievement of high yields and ensuring optimum health. Indeed, all livestock species should have ad libitum access to an adequate quantity of fresh water throughout the day, which also covers the relevant welfare requirements [8].

Despite the recognized importance of water in livestock and poultry production, available information is often fragmented, focusing either on water intake requirements or on quality parameters and typically addressing specific species or production stages in isolation. A comprehensive synthesis integrating both quantitative and qualitative aspects of water use across different livestock systems remains limited. Therefore, the present review aims to provide an integrated overview of water intake and quality in livestock and poultry, taking into account species-specific differences, production stages and environmental influences, in order to support improved animal health, productivity and sustainable management practices.

Metabolic Cycle of Water and Its Importance for Livestock and Poultry

Water is involved in all basic metabolic functions of the body. Maintaining stable levels of water content contributes to sustaining health of animals [9]. Body water is available in two forms: (a) intracellular water, present within cells and accounting for two-thirds of body water, and (b) extracellular water, referring to water in connective tissue, blood plasma and the gastrointestinal track [10,11].

Water plays a role in many functions within the body, as detailed below. Water must be kept in balance within the animal body in order to fulfill these roles and functions.

• Water participates in all biochemical reactions within the animal, acting as a solvent for a wide variety of compounds [12,13,14].
• It contributes to the morphology and development of body cells [14].
• It is part of the composition of normal blood and other body fluids and of glandular secretions and excretions [6,14].
• It supports the animal organism in maintaining body temperature, even during heat stress situations, because of its high specific heat; further, water has a high thermal conductivity, thus allowing a stable body temperature through its evaporation from the lungs and the skin [12,13,14,15].
• It contributes to the increase in daily food intake and improves the degradation and absorption of nutrients [6].
• It acts as a transport medium for nutrients to tissues and organs, participating in anabolic functions; further, it accumulates toxic and useless elements during catabolic functions, leading to their excretion from the animal through the relevant tissues and organs (kidneys, integumentary system, lungs, intestine and liver) [6,13,16].
• Finally, water contributes to the integrity of the nervous tissue, as being part of the cerebrospinal fluid it protects against external mechanical effects [5,17], contributes to the functionality of the joints as a component of synovial fluid [5,17] and supports vision as a component of the aqueous humor and the vitreous humor [5].

Water is indispensable because it serves as the medium for all cellular processes and because its requirement is tightly linked to the biochemical form in which nitrogen is eliminated. Across vertebrate species, the principal nitrogenous end products of protein catabolism differ markedly among taxa, and these differences have profound evolutionary and physiological implications. Ammonotelic species excrete ammonia, which is highly toxic and therefore must be rapidly diluted and eliminated in large volumes of water, imposing a strong dependence on continuous water availability. Ureotelic species, including mammals, convert ammonia into urea in the liver. Although less toxic, urea remains highly soluble and still requires substantial water for renal excretion, resulting in significant obligatory water losses [13,16]. By contrast, uricotelic species (e.g., birds and various reptile species) excrete nitrogen mainly as uric acid, a relatively insoluble compound that can be eliminated in a semi-solid form with minimal water loss. This metabolic strategy represents a major evolutionary adaptation to arid and terrestrial environments, where water conservation is essential, and has also been associated with reproductive independence from aquatic systems [18,19,20].

These evolutionary differences in nitrogen metabolism are fundamental determinants of species-specific water economy, renal physiology, and environmental adaptability. Species characterized by higher obligatory water turnover require continuous access to adequate water supplies to sustain metabolic processes, thermoregulation, and production-related functions, e.g., growth and lactation [10,21,22]. Conversely, species with more efficient water conservation mechanisms may tolerate better limited water availability, but can still be highly sensitive to even small reductions in intake due to tight physiological regulation of hydration status and feed consumption [23,24]. Importantly, water intake is directly linked to the level of exposure to dissolved substances, including minerals, nitrates, sulfates, heavy metals, and microbial contaminants. Animals with greater water consumption inevitably ingest higher loads of relevant constituents, increasing their susceptibility to adverse effects when water quality is compromised [1,25,26].

Consequently, the importance of water extends beyond its role as a nutrient to encompass its function as a vector of environmental exposure, with species-specific physiological traits determining both requirement and vulnerability. Differences in digestive physiology, osmoregulatory capacity, and nitrogen excretion pathways contribute to variation in tolerance to water quality parameters such as salinity and total dissolved solids [1,27,28]. For example, ruminants exhibit a degree of tolerance to elevated salinity, due to rumen buffering and adaptive mechanisms, whereas monogastric animals and poultry are more sensitive to similar conditions, particularly under high metabolic demand or environmental stress [2,24]. Therefore, a mechanistic understanding of water importance must integrate evolutionary biology, nitrogen metabolism, and environmental physiology, linking water intake, excretion strategies, and water quality to animal health, welfare, and productivity.

These fundamental physiological differences also influence species-specific sensitivity to water quality constraints. Species with higher water turnover rates can be more exposed to dissolved contaminants and require greater volumes of water intake to maintain homeostasis, potentially increasing cumulative exposure to undesirable substances [19,20]. Consequently, excretory strategy not only determines baseline water requirements but also contributes to differential vulnerability to water quality stressors across species.

Animals obtain water mostly from the following three sources: (a) drinking water from various sources, (b) water contained in feeds consumed for nutrition and (c) metabolic water arising during nutrient metabolism of fats, proteins and carbohydrates [12,14,16].

Water is absorbed from the gastrointestinal tract, mainly in the intestine (small and large intestine). The rate of absorption depends on various factors, e.g., type of diet and osmotic relationships within the intestine. Water absorption is more rapid and complete when it is obtained with no feed. When feed is consumed during water drinking, polysaccharides present in feed ingredients (e.g., pectin) can form gels within the gastrointestinal tract, which hold water and reduce its absorption [13].

Animals lose water mainly through (a) urine from the kidneys, (b) feces (which also include bile) from the gastrointestinal tract, (c) water vaporization from the skin and the lungs, (d) sweat from the skin and (e) milk from the mammary glands [10,29]. The amount of daily water loss varies in accordance with the activity of the animal and its living conditions [29], increasing under heat stress conditions and decreasing in humid conditions [17]. Increased physical activity also increases water loss through vaporization and sweat [29]. Feeds containing high amounts of proteins or inorganic salts increase loss of water through the urine, whilst an increased amount of undigestible nutrients within the feed can positively affect water loss [17].

Animals must uptake adequate water quantities daily to balance water losses in order to ensure optimum health and production [12,17]. Thirst and the antidiuretic hormone vasopressin (or in poultry arginine vasotocin) affect water balance. Thirst is primarily triggered by an increase in the osmolarity of blood (particularly affected by changes in sodium chloride concentration) and secondarily by a decrease in blood volume. Dryness of the pharyngeal and oral mucosa also increase the desire for water. The thirst center is located in the anterior hypothalamus and regulates the release of the antidiuretic hormone, which controls reabsorption of water from the renal tubules and ducts; thus, it affects excretion of urine, according to water availability [1,29,30].

Water intoxication may occur in some animal species following the sudden ingestion of large amounts of water after a period of water deprivation, particularly when this is accompanied by excessive loss of electrolytes, especially sodium, due to physical exercise or exposure to high environmental temperatures. Although this condition is relatively rare under field conditions, young animals such as calves are considered more susceptible than other livestock species [30]. Water intoxication results in disturbances of fluid and electrolyte balance, which may progress to neurological signs, including disorientation, convulsions, and, in severe cases, death. From a practical livestock management perspective, this condition is most likely to occur when animals are reintroduced to water without restriction after prolonged restriction or deprivation. Therefore, gradual and controlled rehydration is recommended in order to allow physiological adaptation and reduce the risk of acute osmotic imbalance. Ensuring appropriate management of water access under such conditions is an important preventive measure for maintaining animal health and welfare [30].

2. Water Requirements of Livestock and Poultry

It is difficult to determine the precise water requirements of animals, as various factors may affect their intake and loss. Hence, various computational models have been used to estimate these requirements [11,12,13]. The main factors affecting the requirements of livestock in water include animal species, ambient temperature, diet composition, age, production stage, health status and water quality. Differences between animal species are largely related to the nature of the nitrogenous end products of protein metabolism excreted in the urine. For example, poultry have lower water requirements, as they excrete uric acid in a nearly solid form, whilst mammals, in contrast, excrete urea, which is toxic to tissues unless diluted [13,14]. Further, it is noted that cattle excrete feces with higher moisture content than in feces of sheep or poultry; therefore, their water requirements are thus somewhat higher than those of the latter species [25]. Ambient temperature is a major determinant of water intake, as animals exposed to temperatures above their thermal neutral zone increase water intake to replace losses from sweating or evaporation from the lungs and to aid in the thermal regulation of internal body temperature [1,13].

Moreover, diet composition also plays an important role, as dry matter intake is strongly correlated with water intake at moderate temperatures, while high levels of protein, energy or dietary salts such as sodium chloride increase both water intake and excretion [7,13]. Younger animals generally have higher water requirements per unit of body weight due to a higher metabolic rate compared with adults [5,31]. Similarly, lactating animals have particularly high requirements for water in order to replace the losses incurred through milk production [1]. In laying hens, water is discharged mainly through egg production [32]. Moreover, water requirements are high during growth or pregnancy due to the formation of new tissue [17].

Health status further influences water needs, as conditions such as diarrhea or excessive urination can rapidly lead to substantial fluid losses and potentially life-threatening dehydration, requiring timely water and electrolyte replacement [1]. Finally, water quality is a critical factor, as poor-quality water can reduce voluntary water intake and consequently decrease feed intake and animal performance [11,12,13].

Table 1. Indicative daily water intake by adult livestock and poultry (adapted from NRC [25]).

Animal Species	Water Intake (Liters per Day)
Dairy cattle	38–110
Beef cattle	26–66
Horses	30–45
Sheep and goats	4–15
Swine	11–19
Chickens	0.2–0.4
Turkeys	0.4–0.6

, Tables S1 and S2 compile reported water requirements across livestock and poultry species at different ages and physiological stages. Overall, the tabulated data confirm that water intake increases with body size and productivity level, with the highest requirements observed in rapidly growing and lactating animals. Marked interspecies variation is also evident, reflecting physiological differences in metabolism, digestive processes, and nitrogen excretion patterns. These data further emphasize that water requirements cannot be defined as fixed values, but should be interpreted as dynamic ranges influenced by environmental conditions, diet, and management practices.

2.1. Dairy Cattle

An adequate supply of high-quality water is essential for dairy cattle, as milk consists almost of 87% water [21,31,32,33]. Hence, 83% of the high daily water requirements must be covered through drinking water. Usually, farmers provide animals with ad libitum availability of fresh water [22].

The following equation, developed by Murphy et al. [22], has been recommended for predicting daily water intake (FWI, expressed in liters) by dairy cattle:

FWI = 15.99 + (1.58 × DMI) + (0.90 × daily milk production) + (0.05 × daily Na intake) + (1.20 × minimum temperature),

where DMI = daily dry matter intake, expressed in kilograms (kg); daily milk production is expressed in kilograms (kg); daily Na intake is expressed in grams (g); and minimum temperature is expressed in °C.

Further, Holter and Urban [34] and Meyer et al. [35] suggested the respective equations below, modeling the daily water intake (FWI, expressed in liters) for housed dairy cows:

FWI = −10.34 + [0.2296 × percentage (%) of the dry matter of the total diet] + (2.212 × DMI) + [0.03944 × percentage (%) of the crude protein of the total die],

where DMI = daily dry matter intake, expressed in kilograms (kg) and

FWI = −26.12 + (1.516 × average ambient temperature) + (1.299 × daily milk production) + (0.058 × body weight) + (0.406 × daily Na intake),

where average ambient temperature is expressed in °C, daily milk production is expressed in kilograms (kg), body weight is expressed in kilograms (kg) and daily Na intake is expressed in grams (g).

The above equations are used to estimate daily water requirements in dairy cattle based on key influencing factors [36,37,38,39] such as milk yield [40], ambient temperature or other environmental factors, dry matter intake and sodium intake (Table S3) [41]. In practical farm management, these models provide a useful decision-support tool for adjusting water supply according to production stage and environmental conditions. For example, higher-producing cows or animals exposed to heat stress require increased water provision to maintain physiological balance and sustain milk production. Therefore, these equations can assist farmers and nutritionists in optimizing water delivery strategies, improving animal welfare and enhancing production efficiency under variable farm conditions.

During the liquid feeding stage, calves receive most of their water via milk or milk replacer; therefore, pre-weaned calves are often not provided with additional water separately [42]. Kertz et al. [43] have illustrated the strong relationship between water intake, calf starter intake and body weight gain. It is recommended that water be provided ad libitum to calves receiving liquid diets to enhance growth and dry matter intake [9,44].

Despite their practical utility, a critical evaluation of these predictive models reveals several important limitations regarding their broader applicability. Their development is largely based on data derived from high-yielding breeds (e.g., Holstein–Friesian) maintained under controlled housing systems and temperate climatic conditions [22,34,35]. Consequently, these models reflect relatively stable relationships among dry matter intake (DMI), milk production, sodium intake and ambient temperature, which may not be directly transferable to other production contexts. As a result, their predictive accuracy in cattle with varying genetic backgrounds, under grazing-based systems or in extreme climatic conditions, remains uncertain.

From a biological viewpoint, cattle populations differ in traits that directly influence water metabolism, including feed efficiency, thermoregulatory capacity, renal function and behavioral responses. Such variation may modify the relationship between water intake and key predictors (e.g., DMI or milk yield), potentially introducing systematic bias when equations would be applied beyond the populations for which they were originally developed [22,34,35].

In grazing-based systems, additional sources of variability further limit model performance. Water intake can be influenced by drinking behavior, as well as by feed-derived water, with forage moisture content varying considerably depending on pasture composition, maturity and environmental conditions [11,12,13]. Moreover, factors such as walking distance to water sources, grazing patterns, social interactions and irregular drinking events can substantially affect intake, but have not been clearly and explicitly represented in current models. These factors can introduce a variability that is difficult to capture using static regression equations developed under confined conditions [11,12,13].

Environmental conditions, particularly heat stress, represent another important limitation. Although temperature has been included in some equations [22,34,35], it does not fully describe the thermal load experienced by animals. Water intake is influenced indirectly through changes in feed intake and also directly through the increased evaporative losses and thermoregulatory responses [1,13]. In addition, interactions between temperature and humidity further affect heat stress, suggesting that the use of temperature alone in the various models may oversimplify prediction under challenging climatic conditions.

Further, water quality, which affects voluntary intake and animal performance [11,12,13], is not incorporated into existing predictive models. Variations in salinity, total dissolved solids or other physicochemical characteristics may influence drinking behavior, particularly under conditions of high demand or environmental stress, thereby affecting the accuracy of intake predictions.

Overall, these considerations indicate that current predictive equations should be interpreted as context-specific tools rather than ’blue-print’-type models. Therefore, their application outside the conditions under which they had been developed should be performed with caution.

Future research should aim to improve model robustness by incorporating a broader range of variables, including breed-specific characteristics, more comprehensive indicators of heat stress, grazing-related factors (e.g., forage moisture content and animal movement) and water quality parameters. In addition, the integration of behavioral observations and advanced data-driven approaches may allow better representation of the complex and dynamic interactions that determine water intake in modern dairy production systems.

2.2. Beef Cattle

Water requirements in beef cattle are influenced by several interrelated factors, including growth rate, body weight gain composition, physiological status (e.g., pregnancy), activity level, diet composition, feed intake and environmental temperature, as well as water losses through urine, feces, respiration and skin evaporation [29,45,46,47,48,49,50] (Table S4). Among these, feed intake and environmental conditions are considered the primary drivers of daily water consumption in these production systems.

Meyer et al. [45] proposed an empirical equation to estimate water requirements in fattening bulls under housing and feeding conditions typical of temperate Central European systems. The model integrates the main factors influencing water intake under practical farm conditions and can be used as a decision-support tool for estimating daily water supply needs:

FWI = −3.85 + 0.507 × average ambient temperature (°C) + 1.494 × dry matter intake (kg/day) − 0.141 × percentage (%) of the roughage part of the total diet + 0.248 × percentage (%) of the dry matter content of the roughage part of the total diet + 0.014 × body weight (kg).

In practical terms, this equation can assist farm managers in adjusting water provision according to feeding intensity and environmental conditions, particularly in housed fattening systems where both feed intake and thermal environment can vary substantially.

2.3. Sheep

The exact water requirement of sheep has not been precisely established and shows considerable variation depending on body metabolism, ambient temperature, stage of production cycle, feed intake, and diet composition [51,52,53,54,55,56]. Under certain extensive grazing systems, such as free-ranging sheep, animals may obtain sufficient water from pasture moisture and may not require direct access to drinking water throughout the year [57]. In general, however, sheep should have free and continuous access to drinking water to ensure physiological needs are met. The National Research Council [8] provides reference values and predictive equations to estimate water requirements under different physiological states. More precisely, in ewes in the maintenance stage, total water intake (TWl) is 2 to 3 L per kg of dry matter intake (DMI). Also, when DMI is either known or can be estimated, TWI correlates with DMI (kg/d) for diets of moderate nitrogen content [8] according to the following equation:

TWI = 3.86 × DMI − 0.99

where TWI = free water intake (FWI) + preformed water in or on food (PW).

Water intake increases during the pregnancy period. TWl/DMI is 4.3 to 5.2 L per kg in ewes bearing a single fetus and 7.0 to 8.0 L/kg in ewes bearing twin fetuses, which is almost twice and 3.5-fold, respectively, the maintenance requirements. In the final stage of pregnancy, for sheep bearing a single fetus, water requirement amounts approximately to 215 to −290 mL per kg BW^0.75 [8]. Furthermore, water requirements during lactation have been expressed as a total requirement, 3.5 L per L of milk produced and can be estimated as the sum of daily maintenance plus expected water output in milk (peak 50 to 150 mL per kg BW^0.75). The combination gives an estimated 200 to 220 mL per kg BW^0.75 for ewes producing 50 to 60 mL of milk per kg BW^0.75 [8]. Finally, age and growth status affect these requirements. Water requirements of lambs are about 120 to 140 mL per kg BW^0.75 for daily maintenance, plus 8 to 13 mL per g of body weight gain daily for growth. For example, lambs with an average daily gain (ADG) of 100 to 400 g require 255 to 316 mL per kg BW^0.75 per day. The water requirements of penned lambs (not on a milk diet exclusively) are 143 mL per kg BW^0.75 for daily maintenance, plus 7 to 8 mL per g of body weight gain for growth, i.e., for a body weight gain of 200 to 400 g daily, the predicted water requirements are 244 to 348 mL per kg BW^0.75 [8].

Consequently, based on these recommendations, sheep should be provided with unrestricted access to clean drinking water, particularly during late pregnancy, lactation and periods of high feed intake or rapid growth. In practical systems, water supply should be sufficient to accommodate increased demand associated with physiological stressors and higher dry matter intake. For lambs, water provision should account for growth rate, particularly in penned systems where dietary water alone may be insufficient. Monitoring intake is especially important in high-producing ewes and fast-growing lambs to prevent production losses linked to suboptimal hydration. Table S5 indicates the average water intake rates of sheep according to Annicchiarico and Taibi [58].

2.4. Goats

Goats are considered among the most efficient domestic livestock species in their use of water. According to the National Research Council [59], they exhibit a relatively high tolerance to heat stress compared with other livestock species and rely less on evaporative cooling, thereby reducing overall water loss. In addition, goats can conserve water effectively through reduced urinary and fecal losses, including the formation of dry fecal pellets, which decreases their dependence on free water sources [59,60]. Water intake in goats is influenced by multiple environmental and physiological factors. Ambient temperature, production stage (growth, maintenance and lactation), dietary moisture content and the intake of salt and trace minerals all affect total water consumption [8,60,61]. Morand-Fehr and Sauvant [62] reported that recommendations for water requirements of goats are 146 g of water per kg BW^0.75 for maintenance and 1.43 kg of water per liter of milk as a production requirement. The combination gives an estimated 200 to 220 mL per kg BW^0.75 for does producing milk at 50 to 60 mL per kg BW^0.75. For pregnant does bearing a single fetus, the water requirement during the final stage of pregnancy is approximately 140 mL per kg BW^0.75. For kids, the water requirements appear to be similar to those of lambs [8].

From a practical management perspective, goats should be provided with continuous access to fresh, clean and palatable water, as they are relatively selective in drinking and may refuse water with an unpleasant taste. Although free access to water is recommended, in many production systems goats are kept in environments where water availability may be limited, requiring careful management of supply [59,60,61].

Table 2. Comparison of water requirements (liters per day) for maintenance by goats, as calculated by different researchers and their proposed equations (adapted from NRC [8]).

References	Equations	Water Requirements (Liters per Day)
Maintenance a
Morand-Fehr and Sauvant [62]	146 g/kg BW0.75	2.75
Giger-Reverdin and Gihad [63]	107 g/kg BW0.75	2.01
Giger-Reverdin and Gihad [63]	3 L/kg DMI	3.36
Forbes [64]	3.86 × DMI − 0.99	3.33
Silanikove [65]	0.911 × DEI − 5.38	1.56
Literature mean water intake		2.54

Note(s): ^a Assuming body weight (BW) is 50 kg and daily dry matter intake (DMI) is 1.12 kg, with a daily digestible energy intake (DEI) of 45.1 kcal/kg BW.

shows a compilation of recommendations for estimating the daily water requirements of goats for maintenance.

2.5. Pigs

The water requirements of pigs have been relatively less studied compared to those of other livestock species. Water intake is influenced by several interacting factors, including housing system, body weight, reproductive stage, diet composition and ambient temperature [66]. A key consideration is that a distinction must be made between water requirements and actual water consumption, as drinking systems in pig production can lead to substantial water losses due to behavioral patterns at drinkers [28,67]. In particular, pigs have a limited ability to regulate body temperature via sweating and therefore rely heavily on water turnover through urine and feces for thermal and metabolic balance [17]. In general, pigs should always have access to clean and uncontaminated drinking water to maintain health and productivity [68].

Water intake in pigs is strongly affected by environmental and physiological conditions. Differences in housing and drinker systems can significantly affect apparent consumption due to water wastage, particularly at nipple drinkers, where losses of 15% to 42% have been reported in growing–finishing pigs depending on animal size, drinker height and flow rate [67]. Body weight and physiological stage also play an important role. Yang et al. [69] reported that the water requirements of pigs under confined and dry feeding conditions were around 120 mL per kg for growing pigs (body weight 30 kg to 40 kg) and 80 mL per kg for non-lactating adult pigs (body weight of 150 kg to 160 kg) [17]. Moreover, according to the National Research Council [17], despite the fact that swine milk contains 80% water, piglets start drinking water already on the first or second day of life. Water use can vary greatly among litters, ranging from 0 to 200 mL daily, with an average daily intake of 46 mL per piglet during the first week of life. Thereafter, a principal concern regarding water intake by piglets is the role it plays in stimulating creep feed consumption. In weanling piglets, the relationship between feed intake and water intake was described by Brooks et al. [70] using the following equation:

Water intake (L per day) = 0.149 + [3.053 × daily dry feed intake (kg)].

In growing pigs, which were provided with unrestricted access to dry feed for up to 3 kg per animal daily and free access to water, the water-to-feed ratio averaged 2.56:1, from 10 to 22 weeks of age. In wet-feeding systems, water-to-feed ratios range from 1.5:1 to 3.0:1, but there is top-up water available from independent water points [64]. Non-pregnant gilts can consume 11.5 L and gilts in later stages of pregnancy consume 20 L of water daily. Finally, the average daily water intake by lactating sows is 18 L daily, varying from 12 to 40 L daily.

Based on the provided information, practical recommendations include providing pigs with continuous access to fresh, clean water at all times, ensuring that drinker systems are properly designed and maintained to minimize water wastage. Particular attention should be given to nipple drinker height, flow rate and functionality to reduce unnecessary losses, especially in growing–finishing systems [67]. Regular monitoring of water use is recommended to avoid inefficiencies, improve accuracy of intake estimation and reduce unnecessary production costs [28]. Given the modifying effects of feed intake and environmental temperature on water requirement, generalized approximations of water usages are provided in

Table 3. Indicative daily water intake (kg) by pigs ^a according to different physiological stages (adapted by Kyriazakis and Whittemore [68]).

Pig Type	Equation	Water Intake (kg per Day)
Piglets	Dry matter intake (kg) × 6
Growing/fattening pigs, 20–160 kg	Dry matter intake (kg) × 5
Pregnant sows		10–20
Lactating sows		25–40

Note(s): ^a Water should be provided ad libitum to all physiological stages of pigs, even when feed is given wet.

[68].

2.6. Poultry

Water is an essential component of the daily nutrient intake of poultry. Daily access to water throughout the lighting period and a sufficient number of drinkers, which need to be well-distributed and correctly adjusted within the animal house, should be provided [71,72,73]. Ad libitum water intake of broilers can be highly variable and depends on diet composition and feed form (e.g., dietary nutrient content in excess of the animal’s requirements will have a higher impact on water intake than on feed intake, as water is the vehicle for excretion of excess nutrients via the kidney), on production performance (e.g., rate of growth or egg production), on intestinal health, on stress (water intake of broilers is increased during physiological stress according to Virden et al. [74]) and on environmental conditions, such as the environmental temperature and relative humidity [23].

Poultry have lower water requirements than mammals because they excrete uric acid (nitrogenous end product of protein metabolism) in a nearly solid form, which does not require dilution [12]. Generally, it has been assumed that poultry drink approximately twice the amount of feed on a weight basis, but water intake actually varies greatly [24].

Data regarding water intake in Table S6 are for environmental temperatures of approximately 21 °C, except for brooding chicks and poults. For broilers, water intake increases by about 7% for each 1 °C above 21 °C.

Water deprivation for 12 h or more has adverse effects on the growth of young poultry and the egg production of laying hens, and water deprivation of 36 h or more results in a marked increase in mortality. Water restoration, after extended periods of water deprivation (36 to 40 h), may cause the so-termed “drunken syndrome” or “water intoxication” in poultry, leading to death. Notably, young turkeys are particularly susceptible to this condition [24].

3. Quality of Water for Livestock and Poultry

Water is an excellent solvent for almost all elements and compounds. This may cause problems in animal nutrition, as water may ultimately be a means by which animals consume excessive, or even undesirable, minerals or toxic substances [1,8]. Therefore, it is particularly important, especially in the case of livestock producing food intended for human consumption, to ensure the quality of the water that is available for consumption by these animals. This protects the quality and safety of food products and, consequently, public health [75,76].

The key properties that must be taken into consideration when assessing water quality for livestock and poultry include the following [2,10,75,76]:

• Physicochemical properties (i.e., pH, total dissolved solids, salinity and hardness) along with sensory (‘organoleptic’) characteristics (i.e., odor and taste).
• Microbiological quality (i.e., bacterial and viral pathogens).
• Contaminants (i.e., nitrates, sodium sulphates) and toxic substances (i.e., heavy metals, pesticides, herbicides, hydrocarbons).

As a general rule, drinking water for humans is also suitable for consumption by farm animals [13].

3.1. Physicochemical Parameters

Farmers should ensure that the water provided to livestock is clean, fresh and at an appropriate temperature, as these factors directly influence intake and animal performance. Sensory (i.e., organoleptic) characteristics, such as odor and taste, although not always indicative of water safety, should be evaluated because adverse properties may reduce voluntary intake and negatively affect productivity and health [2]. The physicochemical properties of water including pH, total dissolved solids (TDS), salinity and hardness are key determinants of water suitability for livestock and poultry. Typically, water pH ranges between 6.5 and 8.5. In ruminants, consumption of water with pH below 5.5 may contribute to metabolic acidosis, whereas alkaline water (pH above 8.5) may increase the risk of metabolic alkalosis [2]. In addition, pH can influence taste, corrosivity and the efficiency of disinfection processes such as chlorination [25]. The concentration of TDS in water is commonly expressed as parts per million (ppm), micrograms per milliliter (mg mL⁻¹) or milligrams per liter (mg L⁻¹), which are considered equivalent units [26]. TDS represents the total concentration of dissolved inorganic salts and small amounts of organic matter and is widely used as an overall indicator of water salinity and mineral load [26].

Water salinity is a critical factor affecting intake and animal health. In general (

Table 4. Water quality guidelines for livestock and poultry, according to total soluble salts (mg L⁻¹) (adapted by NRC [25]).

Total Soluble Salts (mg L−1)	Comment
Less than 1000	These waters have a relatively low level of salinity and present no serious threat to any class of livestock or poultry.
1000–2999	These waters should be satisfactory for all classes of livestock and poultry. They may cause temporary and mild diarrhea in livestock not accustomed to them or watery droppings in poultry (especially at the higher levels) but should not affect their health or performance.
3000–4999	These waters should be satisfactory for livestock, although they might cause temporary diarrhea or be refused initially by animals not accustomed to them. They are unproper waters for poultry, often causing watery feces and (at the higher levels of salinity) increased mortality and decreased growth, especially in turkeys.
5000–6999	These waters can be used with reasonable safety for dairy and beef cattle, sheep, swine and horses. It may be wise to avoid the use of those approaching the upper limits for pregnant or lactating animals. They are not acceptable waters for poultry, almost always causing some type of problem, especially near the upper limit, where reduced growth and production or increased mortality will probably occur.
7000–10,000	These waters are unacceptable for poultry and probably for swine. Considerable risk may arise for pregnant or lactating cows, horses, sheep, their offspring or for any animals subjected to heavy heat stress or water loss. In general, their use should be avoided, although older ruminants, horses, and even poultry and swine may subsist on them for long time periods under stress-free conditions.
Over 10,000	The risks with water of increased salinity are so great that they cannot be recommended for use under any conditions.

), water containing less than 1000 mg L⁻¹ of TDS is considered safe for all livestock species, whereas higher concentrations may reduce intake and performance, particularly in sensitive species such as poultry [25]. Nevertheless, there is a number of factors needed to be considered during the evaluation of water salinity for livestock and poultry use [25,77]. These factors include (i) the species, the age and the gender of animals, (ii) their reproductive stage (pregnancy or lactation), (iii) the intensity of work performed by the animals and the level of production, iv) the climatic conditions, (v) the type of diet, its moisture content, and the amount of minerals therein and (vi) the potential access to other sources of water [25]. For example, adult sheep appear to be fairly tolerant to water with increased salinity, whereas cattle are less tolerant than sheep, but still more tolerant than pigs and poultry (

Table 5. Maximum allowed concentrations of total soluble salts (g L⁻¹) in water for livestock and poultry (adapted by Pallas [77]).

Animal Species	Total soluble Salts (g L−1)
Dairy cattle	7.1
Beef cattle	10.0
Sheep, in dry period	12.8
Pigs	4.3
Poultry	2.8

) [77].

Water hardness, defined by the concentration of calcium and magnesium salts (

Table 6. Guidelines for drinking water for livestock (adapted by Danicke and Flackowsky [7]).

Parameter	Unit	Allowed Limits	Possible Problems
Physicochemical parameters
pH value a		5.0–9.0	Corrosion of pipelines
Electrical conductivity	μS cm−1	<3000.0	Possible diarrhea, if higher values; reduced palatability of water
Oxidization capacity b	mg L−1	<15.0	Index of oxidizable substances content
Soluble salts, total	g L−1	<2.5	-
Chemical parameters
Ammonia (NH4+)	mg L−1	<3.0	Information for pollution
Arsenic (As)	mg L−1	<0.05	Health disturbances, lower yields
Cadmium (Cd)	mg L−1	<0.02
Calcium (Ca) c	mg L−1	500.0	Functional disturbances, calcium deposition in pipelines and vents
Chloride (Cl−)	mg L−1	<250.0 f <500.0 g	Watery feces a
Copper (Cu) d	mg L−1	<2.0	Consider total intake in sheep and calves
Fluorine (F)	mg L−1	<1.5	Disturbances of teeth and bones
Iron (Fe) c	mg L−1	<3.0	Competition with other trace elements, iron deposition and biofilm formation on pipelines, adverse effect on palatability
Lead (Pb)	mg L−1	<0.1	Avoidance of residues
Manganese (Mn)	mg L−1	<4.0	Possible precipitation in the distribution system and formation of biofilm
Mercury (Hg)	mg L−1	<0.003	General disturbances
Nitrate (NO3−)	mg L−1	<300.0 h <200.0 i	Risks for methemoglobinuria (consider total intake)
Nitrite (NO2−)	mg L−1	<30.0
Potassium (K)	mg L−1	<250.0 f <500.0 g	Watery feces a
Sodium (Na)	mg L−1	<250.0 f <500.0 g	Watery feces a
Sulfate (SO42−)	mg L−1	<500.0	Possible diarrhea
Zinc (Zn) e	mg L−1	<5.0	Mucous membrane alterations

Note(s): ^a pH < 5: acidic and possibly corrosive, addition of organic acids may decrease pH; ^b parameter for organic substances in water (<5 mg/L for added water); ^c clogging of pipelines and nipple trough; ^d recommendations difficult for sheep and milk replacers for calves (use milk replacers low in copper); ^e recommendations for milk replacer for calves; ^f poultry; ^g further animal species; ^h ruminants; ⁱ calves and other animals.

), generally has limited direct effects on animal health; however, high hardness levels may contribute to scaling and clogging in water distribution systems [7,25]. Overall, physicochemical characteristics primarily influence water palatability, intake and system functionality rather than causing direct toxicity.

3.2. Microbiological Quality

Microbiological contamination of drinking water represents a significant risk to animal health and productivity. Water may act as a vehicle for various pathogenic microorganisms, including bacteria, viruses, fungi and parasites, which can lead to disease outbreaks and reduced performance [78]. Biological contaminants include pathogens such as Escherichia coli, Salmonella spp., Campylobacter spp., Shigella spp., Cryptosporidium spp. and Rotavirus strains [7,32]. In particular, the presence of intestinal pathogens such as E. coli O157:H7 is of major concern due to their ability to persist in water and their implications for both animal and public health [2,79]. Additional pathogens potentially transmitted through water include Leptospira spp., Burkholderia pseudomallei and Clostridium botulinum. Water intended for livestock consumption should be free from key indicator organisms such as E. coli and enterococci, as well as from major pathogens (Table S7). Moreover, total aerobic bacterial counts should not exceed 10,000 cfu mL⁻¹ at 20 °C and 1000 cfu mL⁻¹ at 37 °C [7,32]. Maintaining hygienic water sources and distribution systems is therefore essential to prevent contamination and ensure animal health.

In addition to bacterial and parasitic contamination, water may also represent a potential indirect transmission route for highly stable viral pathogens, e.g., porcine epidemic diarrhea virus [80] or foot-and-mouth disease virus [81], particularly under conditions of inadequate biosecurity, high animal density or shared environmental resources. The relevance of water as a transmission medium is linked to the ability of these viruses to persist in the environment under favorable conditions. Foot-and-mouth disease virus, a non-enveloped virus, exhibits considerable resistance to environmental degradation, especially in water with neutral pH, low temperatures and limited ultraviolet exposure, whilst porcine epidemic diarrhea virus, although enveloped, can remain infectious in aqueous environments for extended periods, particularly in the presence of organic matter and under low-temperature conditions [81].

Contamination of water sources may occur through fecal shedding from infected animals, runoff from contaminated housing areas, leakage from manure storage systems, or improper disposal of infected carcasses [80,81]. In intensive livestock production systems, particularly where surface water or shallow groundwater sources are shared between farms, such contamination pathways may facilitate both within-farm and between-farm transmission [80,81]. During outbreak situations, high viral loads in excreta further increase the likelihood of environmental contamination, potentially allowing water to act as a secondary vehicle for pathogen dissemination [81].

Therefore, integration of virological parameters into water quality assessment (particularly in high-risk regions or during outbreak investigations) could enhance surveillance and early detection capacities. This may include the application of molecular diagnostic techniques (e.g., RT-qPCR) for the detection of viral nucleic acids in water sources, combined with the monitoring of environmental factors influencing viral survival [82]. Such an approach would contribute to a more comprehensive assessment of water safety and align with the “One Health” concept by linking animal health, environmental contamination and biosecurity practices [82,83].

3.3. Contaminants and Toxic Substances

Water may contain chemical contaminants and toxic substances originating from natural processes or anthropogenic activities, including agriculture and industry. These include heavy metals (e.g., arsenic, cadmium, lead), pesticide residues, hydrocarbons and excessive concentrations of minerals such as nitrates, sulfates and sodium chloride [1,14]. Reference values for a range of chemical substances are provided in Table S8. Although macro-elements (Table 6) such as calcium, magnesium, phosphorus and potassium are essential for animal nutrition and rarely reach toxic concentrations, trace elements (Table 6) may accumulate to harmful levels depending on the geological characteristics of the water source [1]. Elevated concentrations of elements such as arsenic, iron, manganese, nitrate, sodium, and sulfur may adversely affect animal health and productivity.

Nitrate and nitrite contamination (Table 6) is a commonly occurring issue, particularly in areas with intensive livestock production or heavy use of fertilizers. Nitrate is considered to be of lower potential toxicity; its biological impact in ruminants is mediated primarily through its rapid reduction in the rumen. Specifically, nitrate (NO₃⁻) is reduced by ruminal microbiota to nitrite (NO₂⁻) and subsequently to ammonia (NH₃), which is incorporated into microbial protein [13,26]. Under conditions of excessive intake or inadequate microbial adaptation, the rate of nitrite formation may exceed its further reduction, resulting in nitrite accumulation in the rumen and subsequent absorption into the bloodstream. Then, nitrite is absorbed into the bloodstream, where it can oxidize hemoglobin to methemoglobin, thereby reducing the blood oxygen-carrying capacity and potentially leading to tissue hypoxia and death [13,14,26].

At subacute or chronic exposure levels (approximately 200–300 ppm), nitrate intake may not produce overt clinical toxicity, but may still impair animal performance. Under such conditions, partial methemoglobinemia may persist, leading to chronic reduction in oxygen delivery to tissues [10,30]. This subclinical hypoxic state can impair oxidative metabolism and ATP production, particularly in metabolically active tissues such as muscle, mammary gland and reproductive organs. Consequently, animals may exhibit decreased feed intake, reduced feed efficiency and lower milk production, partly due to impaired mitochondrial function and altered metabolic regulation. Growth performance may also be affected through reduced protein synthesis and altered endocrine responses, while reproductive performance may be compromised due to impaired ovarian and uterine function, resulting in reduced conception rates or early embryonic loss [10,30]. In addition, chronic exposure has been associated with increased oxidative stress through the formation of reactive nitrogen species, as well as disturbances in vitamin metabolism (e.g., vitamins A and E), further contributing to subclinical health and production losses [30].

High sulfate concentrations (Table 6) may also adversely affect ruminant health through various interacting mechanisms and pathways, which involve rumen microbial activity, sulfur metabolism and mineral interactions [26]. In the rumen, sulfate (SO₄²⁻) is reduced by sulfate-reducing microorganisms to sulfide (S²⁻), which exists in equilibrium with hydrogen sulfide (H₂S), depending on ruminal pH. Hydrogen sulfide is a volatile and highly diffusible compound that can be absorbed across the rumen wall or inhaled following eructation [7]. Elevated hydrogen sulfide concentrations exert neurotoxic effects primarily through the inhibition of cytochrome C oxidase in the mitochondrial electron transport chain, thereby impairing cellular respiration and ATP production, particularly in neural tissue [7]. This mechanism is central to the development of polioencephalomalacia (vitamin B₁ deficiency), especially under conditions of high concentrate feeding or sulfate-rich water, where ruminal pH favors increased H₂S formation and absorption [7,14,26].

In addition to direct neurotoxicity, increased sulfate intake may disrupt rumen microbial ecology by promoting the growth of sulfate-reducing bacteria, which compete with other microbial populations for hydrogen, potentially altering fermentation patterns and reducing feed digestibility and energy utilization [14]. Further, sulfate plays a key role in mineral antagonisms, particularly with copper. In the rumen, sulfide interacts with molybdenum to form thiomolybdate ions, which can bind copper and thus reduce its bioavailability [7,14]. This can result in secondary copper deficiency, leading to impaired immune function, reduced growth, anemia, depigmentation and decreased reproductive performance. High sulfate concentrations may also reduce feed and water intake due to decreased palatability and osmotic effects, contributing to diarrhea and further impairing nutrient utilization [7,14,26].

Similarly, elevated concentrations of sodium, potassium and chloride (Table 6) may affect animal performance, particularly in poultry [7]. High iron content (Table 6) may reduce water palatability and cause technical problems in water systems due to precipitation and biofilm formation [7,32]. In addition, various anthropogenic contaminants, including herbicides, insecticides, and chlorinated hydrocarbons, may pose toxicological risks, particularly in areas exposed to agricultural runoff or industrial pollution [14]. Cyanobacteria represent an additional source of toxicity in surface water systems, producing hepatotoxins, neurotoxins and gastrointestinal toxins (

Table 7. Guidelines for the calculated tolerance levels (where no effect was observed) equivalent to the toxicity of microcystin-LR and the cell count of Microcystis aeruginosa ^a (adapted by Olkowski [2]).

Animal Species	Body Weight (kg)	Maximum Water Intake (L Day−1)	Calculated Total Toxin Level (μg/L)	Equivalent Cell Number (Cells mL−1)
Cattle	800	85.0	4.2	21,000
Sheep	100	11.5	3.9	19,500
Pigs	110	15.0	16.3	81,500
Poultry	2.8	0.4	3.1	15,500

Note(s): ^a Adopted from ANZECC [84].

). Compounds such as microcystins are associated with significant health risks, and livestock exposure has been linked to morbidity and mortality events [2,14,26].

3.4. Species-Specific Tolerance Limits

Tolerance to water quality parameters varies considerably among livestock and poultry species, reflecting fundamental differences in physiology, digestive function and nitrogen metabolism. Ruminants, particularly sheep, generally exhibit a higher tolerance to elevated salinity levels, which is partly attributed to their ability to regulate osmotic balance and efficiently utilize water under conditions of increased mineral load. In contrast, monogastric species such as pigs and poultry are more susceptible to adverse effects of high concentrations of dissolved salts due to a more limited capacity for electrolyte regulation and water conservation (Table 4 and Table 5) [25,77]. Although the indicative threshold values for total soluble salts and other physicochemical parameters are presented in Table 4, Table 5 and Table 6, as well as for specific chemical substances in Table S8, these limits should not be interpreted as absolute. Water tolerance is a dynamic trait influenced by multiple interacting factors, including environmental temperature, dietary composition, mineral intake and overall management conditions [25]. For example, high ambient temperatures or diets rich in protein and salts may exacerbate the negative effects of marginal water quality by increasing water turnover and disturbing electrolyte balance. Physiological status further modifies tolerance, with pregnant and lactating animals generally exhibiting increased sensitivity to suboptimal water quality due to higher metabolic demands and fluid turnover. Under such conditions, even moderate deviations from recommended thresholds may impair feed intake, productivity and overall health status [25]. In addition, the presence of specific chemical contaminants, such as nitrates, heavy metals or pesticide residues (Table S8), may pose species-dependent risks, further complicating the establishment of universal tolerance limits. It is also important to recognize that available data on species-specific tolerance limits remain relatively limited and, in some cases, inconsistent across studies, which may explain the discrepancies observed among published guidelines (Table 6) [7]. Consequently, evaluation of water suitability for livestock and poultry should adopt a flexible, risk-based approach that integrates species characteristics, production stage and environmental context, rather than relying solely on generalized threshold values.

3.5. Evaluation of Water for Livestock Consumption

Water quality should be monitored regularly, as it may vary over time due to environmental changes or management practices. Periodic testing by accredited laboratories is recommended to ensure suitability for animal consumption and to prevent adverse effects on health and productivity [2]. The regulatory framework governing water quality and safety in livestock production within the European Union is summarized in Table S9. Water samples should be collected from the source or the main supply line entering the farm, as sampling within the distribution system may reflect contamination from pipes or equipment rather than the original water quality [2,7,32]. Sampling should follow standard aseptic procedures, using sterile containers and appropriate handling to avoid contamination. Typically, approximately 2 L of water should be collected and stored at low temperature (approximately 4 °C) during transport to the laboratory [26]. Additional testing is recommended when changes in water characteristics (e.g., odor, taste, clarity) are observed or when reductions in water intake or animal performance occur.

3.6. Perspective of Water Quality Assessment in Livestock and Poultry Systems

Overall, water quality should not be evaluated solely on the basis of physicochemical and microbiological parameters, but rather in relation to its direct and indirect effects on animal health, productivity and food safety. Suboptimal water quality may reduce voluntary intake due to impaired palatability, leading to decreased feed consumption, altered nutrient utilization and reduced growth or production performance. In addition, the presence of chemical contaminants or excessive mineral concentrations may disrupt metabolic processes, impair reproductive efficiency and increase the risk of clinical or subclinical disorders, particularly under conditions of environmental or physiological stress.

From a food safety perspective, water may also act as a vehicle for the transmission of pathogenic microorganisms or chemical residues, thereby contributing to contamination of products of animal origin and posing risks to public health. Consequently, ensuring adequate water quality is not only essential for maintaining animal welfare and productivity, but also for safeguarding the integrity of the food chain.

Although several international and regional guidelines are available (e.g., NRC recommendations and European Union regulatory frameworks), notable variability exists in the proposed threshold values and assessment approaches. These differences reflect variations in underlying objectives, with some standards primarily focusing on animal health and performance, while others are aligned with human potable water criteria. Furthermore, the limited availability of species-specific data and the influence of environmental and management factors contribute to inconsistencies among recommendations.

Therefore, a critical and integrative approach is required when interpreting water quality guidelines, taking into account species-specific tolerance, production stage and local conditions. In practice, water quality assessment should be incorporated into routine herd health management, with emphasis on risk prevention, regular monitoring and alignment with both animal health and food safety standards.

3.7. Future Perspective on Data-Driven Water Management in Livestock and Poultry Systems

Future research in livestock and poultry water management is expected to increasingly benefit from the integration of advanced data-driven approaches, including the application of machine learning technologies and precision livestock farming methodologies [85]. The growing availability of high-resolution data from sensors (e.g., water flow meters, environmental monitoring systems, and animal behavior tracking) offers new opportunities to develop predictive models of water intake, detect early deviations associated with health or welfare issues, and optimize water allocation under varying climatic and production conditions [86,87]. Machine learning algorithms, including supervised and unsupervised techniques, could be applied to large-scale datasets in order to identify complex, non-linear relationships among environmental variables, dietary factors and physiological responses that are not easily captured by conventional statistical models [88]. In addition, such approaches may support real-time decision-making systems for farmers, enabling early warning of water quality deterioration, improved management of heat stress and more efficient use of water resources in the context of climate change and increasing resource constraints [87]. Integration of these technologies with existing knowledge on animal physiology and nutrition could enhance both predictive accuracy and biological interpretability, thereby bridging the gap between empirical research and practical farm applications. However, the successful implementation of machine learning in this field will require standardized data collection protocols, interdisciplinary collaboration, and careful validation to ensure robustness, transparency, and applicability across diverse production systems [88]. Overall, while still emerging, these approaches represent promising tools for the improvement of sustainability, animal welfare and productivity in modern livestock systems [85].

4. Conclusions

Animals must receive all necessary nutrients in order to maintain health, develop and be able to reproduce. Water is a particularly important nutrient for animals. It involves a large proportion of animal body weight, from 50% to 95% depending on species. Moreover, water participates in all basic physiological roles of an organism (e.g., nutrient transfer, elimination of undesirable substances through secretions, and regulation of body temperature regulation). Intake of water by animals originates from external sources (i.e., drinking), from consumed foods or from nutrient metabolism. In cases of inadequate water intake, various clinical signs may occur (for example, dehydration, anorexia, increased sweating, and a drop of arterial pressure), with long-standing water deprivation resulting in animal death.

Water intake requirements vary in accordance with an array of factors. First, water requirements differ greatly between the various animal species. Other relevant variables include ambient temperature and humidity, animal-related variables (e.g., age, production and reproduction stage) and, of course, nutrition, as well as water quantity and quality already provided to the animals.

Water is consumed daily in larger quantities than other nutrients; thus, its quality is of prime importance. Generally, standards for water quality for animals are similar to those for humans. Quality specifications vary according to animal species and should be assessed as part of a farm’s standard health management evaluations.