Sustainable Swine Nutrition

Finding sustainable means of swine nutrition is important to both pork industry personnel and the environment alike. This reference comprehensively covers the most recent advancements in sustainability that results in more efficient diets, thus reducing both production costs and waste. Chapters include information on alternative feedstuffs, feed additives, bioavailabity of nutrients, and management of wastes and odors. Written by internationally recognized experts in the field, Sustainable Swine Nutrition will be a valuable reference for those involved in all aspects of pork production.

• Comprehensively covers the most recent advancements in sustainability to promote reduced pork production costs and waste
• Covers recent topics such as alternative feedstuffs, feed additives, and bioavalability
• Discusses environmental topics such as waste and odor management
• Written by an international team of experts in the field

• Language: English
• Publisher: Wiley
• Release date: Nov 7, 2012
• ISBN: 9781118485859

Book preview

nc02f004.eps

This edition first published 2013 © 2013 by John Wiley & Sons, Inc.

Wiley-Blackwell is an imprint of John Wiley & Sons, formed by the merger of Wiley's global Scientific, Technical and Medical business with Blackwell Publishing.

Editorial Offices

2121 State Avenue, Ames, Iowa 50014-8300, USA

The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK

9600 Garsington Road, Oxford, OX4 2DQ, UK

For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell.

Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by Blackwell Publishing, provided that the base fee is paid directly to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923. For those organizations that have been granted a photocopy license by CCC, a separate system of payments has been arranged. The fee codes for users of the Transactional Reporting Service are ISBN-13: 978-0-8138-0534-4/2013.

Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought.

Library of Congress Cataloging-in-Publication Data

Sustainable swine nutrition / edited by Lee I. Chiba.

pages cm

Includes bibliographical references and index.

ISBN 978-0-8138-0534-4 (hardback : alk. paper) - ISBN 978-1-118-48582-8 (mobi) (print) -

ISBN 978-1-118-48583-5 (epdf/ebook) (print) - ISBN 978-1-118-48585-9 (epub) (print) - ISBN 978-1-118-49145-4

(obook) (print) 1. Swine-Nutrition. 2. Swine-Feeding and feeds. I. Chiba, Lee, editor of compilation.

SF396.5.S87 2013

636.4-dc23

2012030223

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Disclaimer

The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation warranties of fitness for a particular purpose. No warranty may be created or extended by sales or promotional materials. The advice and strategies contained herein may not be suitable for every situation. This work is sold with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional services. If professional assistance is required, the services of a competent professional person should be sought. Neither the publisher nor the author shall be liable for damages arising herefrom. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read.

Dedication

This book is dedicated with appreciation to my wife, Shoko. Her continuous support, patience, and willingness to give me space to take on challenges such as this are forever cherished!

Contributors

Preface

Swine nutrition is a dynamic and rapidly changing science. New information is generated and added to the field of swine nutrition continuously, expanding the fundamental knowledge base. Obviously, all the information would be extremely important for successful and sustainable commercial swine production. To utilize the information effectively, all those recent developments or current advances in swine nutrition must be put into a proper context simply because of the diversity of such information. We have many books that cover various aspects of swine nutrition, but, unfortunately, there are not many books that are specifically designed to address pertinent issues necessary for successful and sustainable swine production. I am hoping that this book will fill the void and make contributions to the development of environmentally friendly feeding strategies for successful and sustainable swine production.

In commercial swine production, the main objective of diet formulation and feeding strategy is to maximize profits, which does not necessarily imply maximal animal performance. To maximize the economic efficiency, therefore, it is advantageous to supply energy and indispensable nutrients as close as possible to meeting but not exceeding the requirements of the pig. Such optimum feeding strategies would contribute greatly to the efficiency of energy and nutrient utilization, which helps ensure continuous availability of quality sources of energy and nutrients for future swine production, and produce a positive impact on today's environmentally conscious society by reducing the excretion of unutilized nutrients. The development of such feeding strategies involves consideration of a multitude of factors such as genetic variations in the pig, variability, availability, and stability of nutrients in feed ingredients, interactions among nutrients and non-nutritive factors, voluntary feed intake, physical and social environment, and others, and thorough, comprehensive reviews on some of those factors are, obviously, warranted.

The competition between humans and animals for quality sources of energy and nutrients is likely to increase continuously in the future because of ever-increasing world population and an increase in the economic development of both newly industrialized and less economically developed countries. Clearly, it is important for us to find alternative sources of energy and nutrients for swine production. Alternative feed ingredients have different feeding values because of variations in nutrient content and other factors such as bioavailability and stability, anti-nutritional factors, interactions among the nutrients and possibly with non-nutritive factors, and palatability. To utilize potential alternative sources effectively or efficiently can be, therefore, challenging, and we obviously need all the fundamental and applied nutritional information to accomplish such a daunting task. Furthermore, satisfying consumer demands for healthy and nutritious food and alleviating public concerns on the environmental issues are an integral part of successful and sustainable swine production. Therefore, addressing not only the nutritional issues associated with maximizing growth performance and the utilization of energy and nutrients but also the issues associated with the carcass and pork quality and impacts of swine production on the environment are extremely important.

As a comprehensive book on swine nutrition, it is, obviously, important to cover some basic or fundamental aspects of nutrition, i.e., water, protein or amino acids, lipids, carbohydrates, energy metabolism, vitamins, minerals, and also nutrition and immunology. The emphasis of the present book is, however, on recent developments or current advances or some pertinent issues in each of those major areas. Therefore, some fundamental aspects will be reviewed briefly, and the focus of review is on the latest up-to-date information. Then, the remaining book is dedicated to the discussion of some specific, pertinent issues that may contribute to the ultimate goal or theme of the book, that is, to provide a comprehensive review on each pertinent area necessary for successful and sustainable swine production.

It is with the deepest sorrow to acknowledge the loss of Dr. David H. Baker, one of the contributing authors. Dr. Baker was Professor Emeritus of Nutritional Sciences and Animal Sciences at the University of Illinois at Urbana-Champaign. He was elected to membership in the National Academy of Sciences in 2005, which is considered as one of the highest and most prestigious honors that can be accorded to a scientist, in 2005. Dr. Baker received six major awards from the American Society of Animal Science, five major awards from the Poultry Science Association, and two major awards from the American Society of Nutrition. In addition, along with countless others, Dr. Baker received USDA Distinguished Service Award in Research and Charles A. Black Award from the Council for Agricultural Science and Technology. Dr. Baker published almost 600 peer-reviewed journal articles, a record that is not approached by anyone in the field today. Dr. Baker was a Fellow of the American Society of Animal Science, the Poultry Science Association, and the American Society of Nutrition. His legacy will certainly continue to inspire further research in the field of nonruminant nutrition and beyond.

This book would not have been possible without the help of my colleagues, and I would like to thank our contributors for their willingness to participate in this endeavor. I sincerely appreciate their time and dedicated effort on this book project. Also, I would like to thank my graduate students, Sean D. Brotzge and Chhabi K. Adhikari, for their assistance in reviewing and (or) formatting a reference section for each chapter.

Editor

Lee I. Chiba is a professor of animal science in the Department of Animal Sciences at Auburn University, Auburn, Alabama. He received his B.S. in animal science and M.S. and Ph.D. in nonruminant nutrition from the University of Nebraska, Lincoln, Nebraska. Dr. Chiba teaches undergraduate courses in animal nutrition and swine production and graduate courses in nonruminant nutrition and vitamin and mineral metabolism. His research interests are in the areas of dietary manipulations to improve leanness and efficiency of growing pigs and organoleptic quality of pork and also nutritional management to improve reproductive performance of sows. Dr. Chiba has served as a member of the Editorial Board for three terms and an associate editor of the Journal of Animal Science for two terms. He is currently serving his second term as a division editor of the Journal of Animal Science and a section editor of the Livestock Science.

Part 1

Fundamental Nutrition

1

Fundamental Nutrition

John F. Patience

Introduction

Water is a critical component of the pig's diet. Therefore, it seems incongruous that water receives so little attention, either in the popular press or in the scientific literature. It has earned the title of the forgotten nutrient because it rarely attracts attention unless problems arise. The classic phrase expressing the importance of water to the body can be attributed to Maynard (1979) who stated, The body can lose practically all of its fat and over half of its protein and yet live, while a loss of ten percent of its water results in death.

In most major pork-producing regions of the world, water is abundant, inexpensive, and not traded commercially, making it a rare focus of research (Fraser et al., 1990). This helps to explain the dearth of information on a topic of such importance, relative to many other nutrients. However, to give credit to the research community, water is also a particularly difficult nutrient to study. Classical approaches to the study of energy, amino acids, minerals, and vitamins are extremely difficult, if not impossible, to apply to water.

Water is also surprisingly difficult to measure in the laboratory. The water in feed, fecal, urine, or carcass samples is in continuous exchange with the surrounding air, such that samples may either accumulate or lose substantial quantities of water over time. Furthermore, methods to determine the dry matter content of a sample may remove not only water but also volatile compounds, such as ammonia and short-chained fatty acids, introducing yet another source of error. Whereas the measurement of dry matter requires the simplest of laboratory equipment, its determination is anything but simple. For such a simple molecule, water is a very complicated nutrient to study!

Water Content of the Body

The water molecule is by far the most abundant in the pig's body, representing some 99% of the total (Shields et al., 1983). By weight, water ranges from about 82.5% at birth to 53% of the body at market weight; the difference is explained largely by declining lean and increasing lipid in the carcass (Shields et al., 1983). Water in the body is distributed among three pools: the intracellular space, representing about 69% of the total; the interstitium, representing about 22% of the total; and the remainder, which is found in the vascular system (Mroz et al., 1995). Maintaining proper water balance for the total body, as well as within cells and tissues, is a critical requirement of life in terrestrial species. This is intimately related to electrolyte balance within and among cells and organs, another essential homeostatic process (Patience et al., 1989).

Regulation of drinking in the pig is not well understood. Although hypovolemia and hypertonicity appear to be involved, other signals related to food consumption must also exist (Mroz et al., 1995). Furthermore, behavioral stimulation is well known in the pig, leading to luxury consumption of water during periods of boredom, hunger, and other stressors (Fraser et al., 1990).

Water is absorbed from, and secreted into, all sections of the intestinal tract, except the stomach. Absorption occurs by both active and passive processes (Argenzio, 1984). As the chyme passes progressively through the small and large intestines, the osmotic gradient increases, allowing for removal of most water by the terminal colon. The osmotic balance can be disturbed, for example, by the presence of large quantities of osmotically active ions in the intestine. This is the cause of the diarrhea (Fraser et al., 1990).

Water as a Nutrient

Functional Properties of Water

There are few processes in the body that do not involve water directly or indirectly. It is no coincidence that water is central to all living things. Its unique structure elegantly matches its chemistry with its role in physiology, biochemistry, and nutrition.

Its high specific heat makes it ideally suited to its role in thermal homeostasis. For example, the heat of vaporization of water is 540 cal/g, more than double that of other liquids like alcohols and five times that of solvents such as hexane and benzene (Lehninger, 1982). This high specific heat is also 2.5 times that of the dry matter in the body. Under heat-stress conditions, water can absorb much larger quantities of heat energy than other liquids or solids with less consequent change in temperature. In this way, it effectively contributes to constant internal body temperature. Because of its heat of vaporization, it also serves an essential role in the dissipation of heat from the body, through evaporation from the lungs.

Water also plays a central role in acid–base homeostasis. The pH of water is 7, very close to the ideal physiological pH of most tissues. Furthermore, water is an integral part of the bicarbonate buffer system, whereby CO2 and H2O are in equilibrium with H+ and HCO−3:

Unnumbered Display Equation

In this way, water participates in the mechanism responsible for excreting the greatest quantity of acid produced by normal metabolism in the body, namely, through CO2. The bicarbonate system, in association with hemoglobin in the blood, supports removal of an otherwise toxic molecule, CO2, with little damage to tissues and little change in venous pH. In this respect, water plays two roles, the chemical one illustrated previously and that of the solute carrying the molecules throughout the body.

As a solvent, water is the major transportation medium for the exchange of nutrients, chemical energy, metabolites, and waste products among cells and among organs. It also supports movement of hormones from their site of production or release to the target cells or organs or both. Its success as a solvent lies in its unique chemical structure, namely, the dipolar character of the molecule. As an example, simple salt readily dissolves in water, but it is nearly insoluble in other liquids such as benzene or chloroform (Lehninger, 1982).

Water is the basis for chemical reactions in the body such as oxidation and hydrolysis. Oxidation is involved in the degradation of dietary amino acids not used in synthetic processes, and of dietary carbohydrates and lipids not directly deposited into the body. Because about two-thirds of dietary protein is not retained in the body and most of the dietary carbohydrate is oxidized, this represents a substantial source of metabolic water, which we have estimated at about 12% of total daily water balance in the growing pig (Table 1.1). The exact portion of dietary lipid that is oxidized will be highly dependent on the physiological and nutritional state of the pig at any point in its growth curve. It can, therefore, be seen that water is not only ideally suited to its central role in the body, but also essential to so many facets of life.

Table 1.1 Estimated water balance of a 45-kg grower pig.

Table01-1

Water Balance

Water Intake

Although drinking represents the most important way for the pig to obtain water, it is by no means the only source. Feed contains free water, which is obligatorily ingested during meals. Oxidation of amino acids, carbohydrates, and lipids also contributes a substantial portion of the pig's daily needs. However, understanding drinking behavior has proven to be a very complex topic because there are so many factors that influence the pig's need and demand for water (Fraser et al., 1990). These factors include the need to satisfy physiological, biochemical, and nutrition requirements, which themselves are influenced by environment, health, diet, and the quality of the drinking water. However, the pig will also use water to satisfy a variety of behavioral needs, if water is freely available to it.

Schiavon and Emmans (2000) have proposed a simplified model to predict water intake of the growing pig. The model indicates that water intake will be increased by the quantity of water needed to support digestive processes, the quantity lost via the feces and urine, and the amount retained during growth. In turn, water intake will be reduced by water obtained from the feed, water produced by oxidative processes, and water released during protein and lipid synthesis. However, the authors concluded that additional experimentation was required to refine estimates of, for example, the quantity of water required to excrete excess nitrogen and electrolytes from the body, the partitioning of mineral excretion between urine and feces, and the water required for osmotic regulation, among others.

Drinking Water in General

The largest source of daily water intake for the pig is derived from drinking. Indeed, many publications indicate that the only management required in the supply of water is to ensure that it is readily available and of good quality. It is widely viewed that under such conditions, the pig will correctly regulate its own water supply according to its need. However, as Fraser et al. (1990) have pointed out, this is definitely not the case, as pigs will exhibit considerable drive to consume additional water beyond that required for physiological need (Vermeer et al., 2009). However, the main factors affecting drinking-water intake are body weight, feed intake, and temperature (Mroz et al., 1995).

It is critically important to the body that water balance remains under tight control, because dehydration and overhydration are both fatal. The hypothalamic region of the brain is considered to be the center for the control of thirst and drinking behavior (Koeppen and Stanton, 2001). Osmoreceptors located in the hypothalamus detect changes in the osmolality of extracellular fluids, and a rise in plasma osmolality of only 10 mOsm/kg is sufficient to induce the sensation of thirst, which results in drinking (Anderson and Houpt, 1990). Hypovolemia also serves as a signal for thirst, such that a 6–7% fall in blood volume also induces thirst (Anderson and Houpt, 1990). However, based on drinking patterns, other signals must be involved. Mroz et al. (1995) have suggested mucosal blood flow, vascular stretch or distention, and dryness of the mouth as possibilities.

The literature contains many estimates of the drinking-water intake of pigs under ad libitum conditions. These estimates sometimes refer to water disappearance opposed to water intake because no allowance is made for waste. Wasted drinking water has substantial financial implications, especially as it relates to manure volumes and annual slurry hauling costs. Consequently, the selection of drinker design and location is generally given considerable weight to minimize wastage (Brumm, 2010).

Factors Affecting Water Intake

The primary influences on the pig's water intake are body weight, the thermal environment, and feed intake. Like all nutrients, as the pig grows, its daily requirement for water increases. Unfortunately, there are insufficient data in the literature to develop a credible relationship between body weight and water requirement. Schiavon and Emmans (2000) reported that the R² between body weight and water intake was only 0.45; this was measured under highly controlled conditions, and one would reasonably assume that under commercial conditions, the relationship would be even less powerful. Thus, there are numerous other influences affecting the pig's free-choice water consumption.

Intuitively, elevated environmental temperatures increase water intake. Schiavon and Emmans (2000) suggested that for every 1°C increase in the air temperature, water intake increased by 0.12 L/d. Vandenheede and Nicks (1991) reported that water intake increased from 2.2 to 4.2 L/d in finishing pigs when the temperature increased from 10°C to 25°C, a difference that supports the relationship established by Schiavon and Emmans (2000). Mount et al. (1971) reported that raising the temperature from 12°C–15°C to 30°C–35°C increased water consumption by 57% in 33.5-kg pigs, whereas Straub et al. (1976) reported a 63% increase in 90-kg pigs. Yang et al. (1981) observed that total body water remained constant, whereas water turnover increased when the temperature rose from 27°C to 35°C.

It should be noted that during periods of heat stress, pigs tend to increase the amount of time spent playing with waterers, thereby increasing water wastage. That could cause an exaggeration of water requirements during periods of thermal stress.

Estimates of the water-to-feed ratio vary widely in the literature, from as little as 1.5:1 to more than 5:1. Although some of the variation may be explained by environmental conditions, the nature of the diets, or behavioral influences, experimental procedures for such studies also differ widely. However, when the growing pig is housed in thermoneutral conditions, free of behavioral influences, and fed typical commercial diets, the ratio will typically be about 2.5:1 (Shaw et al., 2008); this ratio will be lower in the finisher pig (perhaps 2:1).

Sometimes, failure to account for wastage increases apparent intake. Thus, one should be careful about terminology because water intake refers to the quantity actually consumed by the pig, whereas water disappearance refers to water that leaves the water delivery system. For example, wastage of water dispensed by a wall-mounted nipple drinker can typically range from 25% to 50%, or even higher (Li et al., 2005).

It is widely held that water intake increases as dietary protein increases. This is supported by numerous reports in the literature (Suzuki et al., 1998; Pfeiffer et al., 1995) and makes sense physiologically, because excess protein in the diet places demands on the kidney to excrete greater quantities of urea. However, there is also a body of literature that indicates the relationship between dietary protein level and water intake is not linear (Albar and Granier, 1996; Tachibana and Ubagai, 1997; Shaw et al., 2006). Therefore, it may be concluded from the literature that lowering dietary protein as a means of conserving water may not be successful, and that dietary protein only elevates water intake when it is present in substantial excess (Shaw et al., 2006). Mroz et al. (1995) have suggested that many studies relating water intake and dietary protein content were confounded by concurrent changes in dietary mineral levels.

It is also well known that increasing the salt concentration in the diet will result in elevated water consumption (Seynaeve et al., 1996). Interestingly, pigs also consume greater quantities of water when the water itself is high in minerals (Maenz et al., 1994).

As occurs in many species, hunger will induce increases in water consumption. For example, Yang et al. (1984) reported that providing restrictively fed pigs with increasing amounts of feed reduced the observed water-to-feed ratio from 5.1:1 to 3.3:1.

It is widely accepted that pigs consume luxury amounts of water for play or because of hunger-induced or stress-induced polydipsia, such that simply measuring water disappearance may introduce errors into the estimation of water requirements (Fraser et al., 1990; Vermeer et al., 2009).

Feed Water

The pig obtains a certain amount of water from the feed. The actual amount consumed with feed would be a function of the quantity of feed eaten and of the percent moisture in that feed. Quantitatively, this is not a large portion of the pig's daily intake, representing something less than 5% of the total.

Metabolic Water

The oxidation of 1 g of lipid, protein, or carbohydrate, on average, releases 1.10, 0.44, and 0.60 g of water, respectively. Of course, the exact quantity will be a function of the structure of the specific fatty acid, amino acid, or carbohydrate (Patience, 1989).

Water Released by Tissue Synthesis

Water is released by the synthesis of body constituents. Thus, 1 g of protein retained in the body releases 0.16 g water, whereas 1 g of lipid releases 0.07 g water (Schiavon and Emmans, 2000).

Water Excretion

Renal Excretion

The quantity of water eliminated from the body via urine will be a function of the solutes present in the urine and the ability of the kidney to concentrate the urine, which has been estimated at 1 mOsm/L in the pig (Brooks and Carpenter, 1990). The solutes of greatest importance in this regard will be nitrogen (primarily but not exclusively as urea), calcium, phosphorus, sodium, chloride, magnesium, and potassium. These fixed cations and anions will be accompanied by metabolizable anions and cations, respectively (Patience, 1989).

The permeability of the renal tubules is under the influence of the antidiuretic hormone (ADH), which is released from the pituitary gland. The ADH is released when receptors in the atria of the heart detect a decrease in blood volume. In response to ADH, the kidney reabsorbs more water, thus returning blood volume to a desirable level (Berdanier, 1995). In addition to ADH, the rennin-angiotensin system plays a role in maintaining fluid volume by stimulating ADH and aldosterone release, enhancement of sodium and chloride resorption, and vasoconstriction. Aldosterone is secreted by the adrenal glands and serves to conserve sodium and chloride reserves (Berdanier, 1995).

Fecal Excretion

Water lost with the feces can be estimated in a number of ways. The simplest, but least precise, is to assume a typical moisture content of feces (Table 1.1). More sophisticated approaches look at the individual constituents of the feces and determine the quantity of moisture associated with each. Unfortunately, there are insufficient data available to undertake this approach with any reasonable degree of precision (Schiavon and Emmans, 2000).

Water Balance

One cannot simply feed graded levels of water to the pig and define requirement as the level that optimizes performance. Because the pig possesses such a large and dynamic pool of water in the intracellular, intercellular, and extracellular spaces, any growth study would require a quantitative measurement of both sources of water supply to the pig, including drinking water, water in the feed, water generated by metabolism, and excretion of water from the body via feces, urine, respiration, and sweat. The difference would, of course, be water accumulated as a consequence of growth. Measuring so many water pools would be extremely difficult, and, based on the literature, it has never been attempted. However, Schiavon and Emmans (2000) have attempted to model water intake in the pig, accounting for water required for digestion, fecal excretion, urinary excretion, evaporation, and growth.

Table 1.1 demonstrates an attempt to quantify water balance in a typical growing pig housed in a thermoneutral environment and fed a typical commercial diet ad libitum, which is based on experimental data reported by Shaw et al. (2006). From this determination of the water balance of a growing pig, it is readily apparent that water generated by metabolism of dietary fat, protein, and carbohydrates represents a substantial portion (12%) of the total daily water supply. Conversely, moisture in the feed represents a modest 4% of the total. In terms of excreted water, urine is only slightly greater than other losses (47% versus 39%); the latter will consist mainly of water lost by evaporation, a component that obviously would be greatly affected by ambient environmental temperature. Fecal losses of water, representing 11% of the total, will vary somewhat by diet composition, but will obviously be impacted by the presence of gastrointestinal pathologies such as diarrhea.

Water Requirement

Numerous approaches to the study of water requirements are available (Fraser et al., 1990). The classical approach of providing graded levels of the nutrient in the daily diet and then evaluating performance outcomes is difficult to apply to water, because the results will be influenced by many factors such as environmental temperature, the nature of the diet (e.g., levels of protein and minerals), and the portion of gain that is lean or lipid.

A second approach is to provide water to the pig on an ad libitum basis, and select the level of intake associated with optimum gain. This is a particularly troubling approach, although it has been used all too often in the literature, because there is no assurance that the pig's intake is established by physiological need. It is well known that pigs, as well as other species, engage in luxury intake of water because of factors such as stress and hunger (Patience et al., 1987). In one experiment, where water was provided ad libitum to 40-kg pigs, daily intake varied from 1.70 to 16.8 L/d (Patience et al., 1987), revealing how inadequate this approach to defining requirements can be.

A third approach is to define the level of intake that prevents specific pathologies—in this case, dehydration. However, the pig will resort to metabolically costly means of preventing dehydration, such as excreting hyperosmotic urine, to conserve water balance. Although one can argue that hyperosmotic urine is produced only when blood volume declines, such mechanisms are extremely precise and would be very difficult to detect in a simple study of water intake.

It has been suggested that the water requirement of the pig can be defined as a ratio of water-to-feed intake (Brumm et al., 2000), but this ignores the impact of body weight, environmental temperature, and diet composition as key factors influencing water intake (Mroz et al., 1995). However, such ratios provide a useful practical tool, provided their limitations are well understood by the user. By understanding that recommended water-to-feed ratios are defined in a thermoneutral environment, one can suggest the following standard: 2.5:1 for early growing pigs and 2.0:1 for the late finishing pig. In some instances, water-to-feed ratios, as low as 1.5:1, have been reported in late finishing. From this, one can suggest that the average water intake in a thermoneutral environment will be about 3.2 L for a 25-kg pig, increasing to 5.5 L at a market weight of 130 kg. However, it must be reemphasized that specific requirements will vary among farms because of widely varying feed intake, changes in the thermal environment (Mroz et al., 1995), and the unique behavioral demands of different populations of pigs (Fraser et al., 1990).

Water Delivery to the Pig

There are a number of issues associated with the proper delivery of water to swine (Gonyou and Zhou, 2000; Brumm et al., 2000). Inadequate water impairs pig performance and in cases of severe restriction reduces feed digestibility (Mroz et al., 1995). Excess water leads to waste and unnecessarily increases manure volumes. This, in turn, increases manure hauling costs when applied to the land. Excessive water waste also leads to increased medication costs, if medications are supplied via the drinking water. Fecal contamination of drinkers can lead to reduced intake and impaired performance. Consequently, the selection of the correct drinker is an important decision in pig management.

Nipple Drinkers

Water can be delivered to the pig using a number of different approaches. Traditionally, nipple drinkers have been mounted on or near the rear wall of the pen to provide water ad libitum. Water wastage is an important issue with such systems; 25% of the water delivered by a typical nipple drinker is wasted by the pig and unnecessarily leads to excessive manure volumes that must be removed from the barn (Li et al., 2005). In the study by Li et al. (2005), water flow rate was set at the manufacturer's recommended level and the height of the drinker was adjusted as the pigs grew. The authors suggested that under more typical commercial practice, where nipple-drinker height is fixed and flow rates often exceed that required by the drinking device, wastage can approach 50–60%. It is recommended that the bottom of the nipple drinker be located 50 cm above the shoulder of the smallest pig in the pen (Gill and Barber, 1990), which itself can be calculated as 150 × BW⁰.³³ (Petherick, 1983). Excessive flow rates will also increase water wastage.

Although excessive water flow rates of nipple drinkers should be avoided to minimize wastage, inadequate flow rates can also be a serious concern. For example, in the nursery, salt poisoning has been reported in newly weaned piglets because they were unable to consume adequate water to remove dietary salt from their systems. Neinable and Hahn (1984) reported that flow rates adequate at low temperatures can be inadequate when pigs are heat stressed. Table 1.2 presents typical recommendations for nipple-drinker flow rates, which balance the need to avoid excessive wastage while ensuring adequate water intake.

Table 1.2 Recommended nipple drinker flow rates for various classes of swine.

A variant of the wall-mounted nipple drinker is the swinging nipple drinker, which is suspended from the ceiling of the barn. It reduces the amount of water wasted by the pig, although the exact amount has not been quantified. Brumm et al. (2000) reported a 11% reduction in water disappearance with the use of swinging drinkers compared to wall-mounted drinkers, but waste was not measured.

Dish Drinkers

Wall-mounted dish drinkers tend to waste very little water if correctly adjusted, but their height must be increased as the pigs grow. Otherwise, they may be fouled and this leads to reduced water intake. Dish drinkers should not be located close to pen corners, as this increases the risk of fouling. Brumm et al. (2000) reported 25% less water disappearance from bowl drinkers than swinging nipple drinkers.

Wet–Dry Feeders

Wet–dry feeders are another alternative method to provide drinking water. They allow pigs the opportunity to eat feed either in dry form or wetted (hence, their name). Wet–dry feeders reduce water wastage by 35%, compared to wall-mounted nipple drinkers. In temperature climates, an additional source of water is not required, but in warmer climates, where heat stress is a common occurrence, additional drinkers are recommended. The selection of drinker type will determine if water wastage will be a concern. Table 1.2 provides recommended flow rates for nipple drinkers for different classes of swine (Patience et al., 1995).

Liquid Feeding

Liquid feeding offers numerous advantages over conventional dry feeding of pigs. These include improved growth rates or improved feed efficiency or both (Hurst et al., 2008). However, these advantages may be more noticeable when the diet contains wheat and barley as compared to corn (De Lange et al., 2006). There is increasing interest in fermented liquid feeding to improve piglet health, and also to improve the bioavailability of phytate-bound phosphorus in many feedstuffs of plant origin.

There is a lack of agreement in the literature on the most appropriate water-to-feed ratios to apply to liquid feeding systems. Minimum water is required for mechanical purposes to ensure the adequate flow of feed from the mixer to the pigs, but beyond that, recommendations vary. For example, it has been shown that dry matter intake increases as the water-to-feed ratio increases to 3:1 or 3.5:1 (Barber et al., 1991a,b), but further increases up to 6:1 lowered dry matter intake. In current commercial practice, water-to-feed ratios tend to fall within the range of 2.5:1 to 3.5:1.

Water Management

Gestating Sows

Water intake in gestating sows is greatly influenced by behavioral factors, notably hunger-induced polydipsia. Like many other species, pigs overconsume water when their appetite for food is not fully satisfied. Consequently, water intake values reported in the literature for gestating sows vary widely. Examples include 5.6 L/(d kg) feed (Lightfoot and Armsby, 1984) and 2.5 L/(d kg)(Friend, 1971), 14.9 L/d (Bauer, 1982), 17.2 L/d (Madec et al., 1986), and 25.8 L/d (Kuperus, 1988). Where ranges were reported, they were very large; for example, Pollman et al. (1979) reported a range in daily water intake from 3.4 to 46.2 L/d. It is very difficult to assign a specific intake need for the dry sow, because hunger-induced polydipsia is a legitimate consideration. Therefore, the recommendation for dry sows is fresh water supplied ad libitum throughout the day.

Lactating Sows

A common question in nursing sow management relates to water and whether insufficiency of water intake impairs lactation performance, at least in some instances. Most studies on lactational water intake have simply measured intake, without attempting to determine its adequacy. In a survey of many such studies, Fraser et al. (1990) summarized the results from twelve different reports. The only reasonable conclusion was that intake varied widely, both within and among studies. Mean intake among studies ranged from 8.1 to 25.1 L/d.

Fraser and Phillips (1989) presented interesting data that indicated that low water intake during the first five days postfarrowing was correlated with reduced piglet growth rates. Sows with low water intakes nursed piglets with low gains and sows with high water intakes were the opposite. It is impossible to assign cause and effect in such studies, but it seems that paying attention to water intake in the early nursing period is critical to good piglet growth.

Paying attention to water intake during the first five days postfarrowing seems to be very important. This means making it as easy as possible for sows to access drinkers, whether they are standing or lying, because postpartum lethargy may be important. Because sow's milk is about 81% water, the need to optimize water intake is self-evident.

Nursing Piglets

There is no agreement on the need for supplemental water by the nursing piglet, especially during the first one to two weeks after birth. Fraser et al. (1990) have suggested that early water intake in piglets ranges from nil to more than 100 mL/d. Deligeorgis et al. (2006) reported that piglets visited the drinker, on average, 16 hours after birth; pigs that visited the drinker weighed more 48 hours after birth than those that did not, and placement of the drinker affected water intake.

Because sow milk production, thermal environment, and creep feed consumption all influence water intake by suckling pigs, it is generally recommended to make water available to piglets from the time of birth. As weaning ages in North America increase from less than 21 days to 25 days or higher, it will become increasingly important to provide a continuous supply of fresh drinking water in the farrowing crate to encourage creep feed consumption.

Weaning Pigs

During the late nursing period, a pig will be consuming 700 mL to more than 1.0 L of water per day in the form of milk. Yet, immediately after weaning, water intake follows an unusual pattern of decline from about 1.0–1.5 L/d on the first day of weaning to 0.4–1.0 L/d around the fourth day postweaning (McLeese et al., 1992; Maenz et al., 1993, 1994; Torrey et al., 2008). This indicates that during the first few days postweaning, water intake: (1) does not follow feed intake patterns, and (2) may be a limiting factor in postweaning growth rate. Furthermore, water intake has not been found to be associated with the severity of diarrhea suffered by the pig during the first week postweaning (Maenz et al., 1994). Phillips and Phillips (1999) reported that the choice of drinker delivery system failed to alter this unusual pattern of water intake.

Because adequate water intake is required to support maximal feed intake, and because depressed feed intake is a key concern in the postweaning period, it is clear that more attention should be paid to water during this important transition period in the pig's life. Water should be made readily available to the pig, and assurance that the pig knows where water is supplied is a key part of early postweaning management (Dybklaer et al., 2006). However, simply making water available to the pig does not seem to ensure adequate intake. The use of dish-type drinkers may provide benefit in this regard because pigs can see the water, but to date, the advantage has not been shown experimentally.

Grower and Finisher Pigs

Many factors influence ad libitum water intake during the grower–finisher period. The subject has been reviewed by Brooks and Carpenter (1990). In a thermoneutral environment, typical water-to-feed ratios (corrected for waste) decrease from about 2.5:1 during the early growing period (approximately 25 to 50 kg) to 2:1 during the late finishing stage (80+ kg; Mroz et al., 1995; Li et al., 2005). Variations from these standards exist, and are often explained by unaccounted for wastage or deviations in thermal environment. Inadequate water intake may reduce both growth rate and feed digestibility, but the level of feed restriction to do so must be quite substantial (Mroz et al., 1995).

Water Quality

Quality Criteria in General

The objective of any pork producer is to provide an abundant supply of high-quality drinking water to pigs on a regular basis. However, the term quality has many meanings. Often, quality for pigs is adopted from human drinking water standards and, therefore, includes considerations such as smell, clarity, color, and taste, which in all likelihood mean different things to pigs than to people.

Therefore, caution is advised when considering water quality because the criteria employed and the measurements of those criteria are all important. Although the best-quality drinking water should always be used, pigs are adaptive to a wide range of water quality, such that water considered marginal for humans may be quite acceptable to pigs. Water quality can be considered under three broad categories: physical, chemical, and microbiological.

Physical

Physical attributes by themselves tend to be of little practical importance in pork production. Pigs are much more tolerant, if not oblivious, of unusual colors and tastes in water. However, turbidity, color, and odor can be symptoms of other problems that may need attention.

Turbidity

Turbidity is more of an aesthetic attribute than a quality one. High turbidity may simply represent suspended colloidal material, such as silt or clay, in the water. At low levels, this means very little to the pig. However, it may also represent suspended microorganisms, which may be of great importance. Turbidity, therefore, is a measurement that can be considered more qualitative than quantitative for the pig. If the water has a turbidity of less than 5 nephelometric turbidity units (NTU), then it is probably acceptable for pigs. If turbidity is above 5 NTU, then additional measurements of chemical and microbiological content of the water should be undertaken to determine their cause.

Color

Color, measured in true color units (TCU), is not a concern for drinking water supplied to the pig, unless the color is due to an undesirable contaminant in the water. Other assays will be of much greater value to the pig than color, and these include total dissolved solids, sulfate, hardness, and microbiology.

Odor

Odor, measured in threshold odor number (TON) is not an issue for pigs. Fresh water should be almost free of any odors. However, if present, the cause of off-odors may be important, so further analysis is warranted. The most likely cause of off-odors would be microbiological contamination or the presence of organic compounds.

Chemical

Total Dissolved Solids (TDS)

As imprecise as TDS is, it is still used as a means of determining the suitability of drinking water for swine. Total dissolved solids are due mainly to the presence of bicarbonate, chloride, and sulfate salts of sodium, calcium, and magnesium. Generally, if TDS is low (i.e., below 1,000 mg/L) then mineral contamination cannot be a problem and no further testing is required. If TDS is between 1,000 and 3,000 mg/L, then it could cause transient diarrhea, particularly in young swine. This would be particularly true if the predominant anion in the water is sulfate. Total dissolved solids between 3,000 and 5,000 mg/L is probably still acceptable (NRC, 1974), but needs to be watched carefully, and greater than 5,000 mg/L must be carefully scrutinized before being fed to pigs. Simply stated, TDS is a broad-brush assay. If the results are low, then the water will be fine, in terms of mineral contaminants. As TDS increases, the risk of diarrhea increases. Pigs can adapt to a wide variety of water qualities, but the best option is always to select the water with the lowest TDS, if a choice is available.

Conductivity

As the name suggests, conductivity is a measure of the ability of the water sample to conduct an electrical current. A high conductivity indicates a high level of dissolved mineral ions in the water. Because it is nonspecific, an elevation in conductivity provides little useful information on water quality. However, if conductivity is high, it provides an indication that additional assays of the water sample are required to determine the exact ions present.

Conductivity, sometimes also referred to as specific conductance, is reported in microsiemens, (μS)/cm, and can be converted to TDS by multiplying by a factor (K), as follows:

Unnumbered Display Equation

Unfortunately, the value of K can range from 0.75 to 0.55, depending on the water composition. For example, if the primary contaminants in the water are sodium and chloride, the factor will be 0.67; the factor will be higher if the primary contaminant is sulphate.

In pig nutrition, a direct measure of TDS is preferred over conductivity. However, neither TDS nor conductivity provides sufficiently specific information to properly identify water quality problems.

Water pH

The pH of the water is a measure of the acidity or alkalinity of the water. The vast majority of water samples will fall within the acceptable range of 6.5–8.5. If the pH of the water is elevated, it can impair the effectiveness of chlorination. If the pH is low, certain water medications may precipitate. The addition of pH modifiers to the water is known to interact with certain pharmaceutical products, such that great care must be taken when administering these via the drinking water (Dorr et al., 2009).

Hardness

Hardness is a measure of the multivalent cations in the water, primarily calcium and magnesium as carbonates, bicarbonates, sulfates, and chlorides. Hardness has no known impact on animal health, but it does impair washing because of an increased requirement for soap or detergents. Hardness can also lead to the accumulation of scale in water delivery, treatment, and heating equipment. Thus, water hardness can lead to problems with water heaters, nipple drinkers, and filters. The United States Geological Survey considers water soft if hardness is less than 60 mg/L as CaCO3 and considers it very hard if the concentration is greater than 180 mg/L (Chinn, 2009).

Sulfate

Sulfate is a mineral that occurs naturally in most groundwater sources but is usually low enough in concentration to not cause any problems with pigs. However, in some instances, sulfates can exceed 1,000 mg/L, which is generally considered the threshold for acceptable drinking water for swine. Although the intestinal tract of the pig is well supplied with transporters that can absorb sulfates, sulfates are often resecreted back into the large intestine, resulting in an osmotic diarrhea (Maenz and Patience, 1997). Depending on the level of sulfates in the water, pigs can adapt over a period of weeks so that associated diarrhea is transient. The problem is most acute in newly weaned pigs, as they have not been exposed to sulfates and perhaps are physiologically more susceptible, as well. In any event, sulfates, whether of magnesium or sodium origins, can lead to osmotic diarrhea. The impact is clearly dose dependent.

However, there are ample data to show that pigs can perform as well in the presence of sulfate-induced diarrhea as in its absence. The pigs will not look as robust, largely due to dirtiness, but they show a remarkable ability to tolerate relatively high levels of sulfate in the water (Table 1.3). In this particular experiment (McLeese et al., 1992), the increase in scouring as sulfate levels increased was reflected in the scour score, but performance was unaffected. It should be noted that the pigs employed in this study were weaned at four weeks of age. Some bacteria can extract the oxygen from sulfate, leaving H2S or HS− as the residue; H2S creates the rotten egg odor that sometimes exists in water samples.

Table 1.3 Impact of elevated total dissolved solids and sulfates in the drinking water in weanling pig performance¹.

Table01-1

To reduce the incidence or severity of diarrhea, salt can be reduced in the feed because of the heavy salt load in the water. However, this must be undertaken with great care. Reducing salt lowers both sodium and chloride, and if done incorrectly, this can result in a primary sodium or chloride deficiency, either of which impairs feed intake.

Iron and Manganese

There are no known direct health issues associated with elevated iron and manganese in drinking water, but they can cause handling problems. Iron and manganese tend to exist in ground waters in their reduced form, and thus are soluble. However, as water is extracted from the well and exposed to oxygen, they are oxidized and rendered insoluble. Oxidized iron has a typical reddish-brown hue, whereas manganese tends to be darker, almost black. If present in the water, they can be seen in persistent discoloring of toilets and sinks, but more critically, they coat water-heater elements, nipple drinkers, chlorinators, and others. Iron in the water should not exceed 0.3 mg/L, although staining can occur at levels as low as 0.1 mg/L (Chinn, 2009). The level of manganese should not exceed 0.05 mg/L (Chinn, 2009).

Iron in the water can also support the growth of iron bacteria. The organisms can cause foul odors and reduce well water output; both of these indications are caused by the accumulation of bacterial slime in the water or along the well casing.

Nitrates and Nitrites

Nitrates and nitrites are a particular concern in human drinking water because babies are particularly susceptible to the blue baby syndrome, so called because nitrates and nitrites bind hemoglobin, reducing its oxygen-carrying capacity and forming methemoglobin. Cattle are much more susceptible to nitrates than pigs because rumen bacteria convert nitrates to the much more dangerous nitrites. Garrison et al. (1966) reported that 200 mg nitrates/L impaired growth rate and impaired vitamin A metabolism. Sorensen et al. (1994) fed even higher levels of nitrates, up to 2,000 ppm, to pigs from weaning to market and saw no adverse effects on any growth performance criteria or on hemoglobin or methemoglobin levels in the blood. Both experiments used nitrate levels that are higher than typically observed in most water supplies. However, these data indicate that nitrate guidelines for human infants probably do not apply to pigs after weaning.

The recommended limit of nitrates plus nitrites in drinking water for swine is 100 mg/L and nitrites alone should not exceed 10 mg/L (Chinn, 2009). However, drinking water for humans is recommended to contain no more than 10% of these levels.

Sodium

Sodium is not a concern in drinking water by itself, unless it is being consumed by people who are on a low-sodium diet. However, cations like sodium are associated with an anion in the water. If this anion is sulfate it will lead to diarrhea, because sodium sulfate, also known as Glauber's Salt, is a powerful laxative. If the cation is chloride, there is little cause for concern, and if the cation is carbonate or bicarbonate, the water may have a higher pH. It is important to note that simple ion-exchange water softeners replace calcium and magnesium with sodium, and thus elevate the levels of sodium in the water.

Magnesium

Magnesium by itself would be of little concern in the water. As mentioned previously, it contributes to water hardness. Also, it is associated with a counterbalancing anion; if the anion is sulfate, it is called Epsom salt, which has a potent laxative effect on the pig (also see previous discussion on sulfates).

Magnesium can be removed from the water through ion-exchange water softening. The magnesium ion will be replaced with sodium in a 1-to-2 ratio. Although this will reduce the hardness of the water, it will have no impact on the incidence of diarrhea in the pig because sodium sulfate is also a potent laxative.

Chloride

Chloride is not normally elevated in either groundwater or surface water. If it is high (> 400 mg/L), it will impart a metallic taste to the water, which so far does not appear to adversely affect the pig. If drinking water is high in chloride, the quantity of salt in the diet can be reduced concomitantly; however, this can only be done if sodium is also elevated in the water, or if a source of sodium other than NaCl is included in the diet.

Microbiological

The microbiological quality of water is often considered the primary issue in water quality discussion. The presence of pathogenic organisms in the water can lead to disease breaks in the herd and make it almost impossible to achieve the highest level of performance. Surface water is at greatest risk because of the higher chance of contamination, but groundwater can also contain pathogens. For example, water can contain bacteria such as salmonella, shigella, cholera, and campylobacter; viruses such as enteroviruses; and protozoa such as cryptosporidium and giardia. Also, certain algae in the water can lead to gastroenteritis.

Water Treatment

The technology exists to modify drinking water in any number of ways to achieve a final product that meets minimum quality standards. Treatment systems for human water supplies are highly sophisticated and capable of removing a wide array of organic and inorganic contaminants. However, these processes can be very expensive and require supervision by highly qualified personnel. Such levels of sophistication are rarely employed in agricultural settings, unless unusual conditions exist. However, some aspects of water treatment technology have been adapted to farm applications when the need arises.

Removal of Colloids

If physical attributes need to be corrected, the use of activated charcoal is commonly recommended. It can adsorb many of the constituents that impact taste, color, and odor and also remove some organic impurities, as well.

Water Softening

Water can be softened. The most common and simplest treatment system is ion exchange, which replaces calcium and magnesium with sodium. There is no logic to softening drinking water, unless the water is so hard that it plugs drinkers and affects other equipment. However, office water, used for laundry or showering, may be softened to reduce the demand for soap.

Removal of Sulfates

The only practical way to reduce or remove sulfates from the water is through reverse osmosis. However, this tends to be quite expensive, both in terms of initial capital cost and ongoing operating costs, so it is not normally adopted by pork producers.

Removal of Iron and Manganese

Both iron and manganese can be reduced in drinking water through the use of specific filters. However, aeration, followed by a settling tank, is somewhat effective for iron removal (Table 1.4) and the cost is low. To maximize the quantity of iron removed from the water, chlorination antecedent to the settling tank is recommended. The process is most effective when the pH is above 7.5 (Vigneswaran and Visananthan, 1995). Chlorination also helps to prevent microbiological contaminaton of the water in the settling tank. The settling tank needs to be cleaned from time to time to remove accumulated iron and/or manganese. Filtration after the settling tank is recommended for the final step in the removal of iron.

Table 1.4 Effect of aeration and seven days' settling on water composition, mg/L.

Removal of manganese by aeration and filtration is not recommended. It occurs maximally at a pH greater than 9.5, which is much higher than most water supplies. Also, the sedimentation time is much longer (Vigneswaran and Visananthan, 1995), so this process is much more effective with iron than with manganese.

Disinfection

Disinfection of water supplies is a critical component of any treatment system. Water should be monitored and when microbial contamination rises, disinfection needs to be initiated. Fortunately, in many parts of the pork-producing world, water supplies are free of bacterial, viral, and protozoal contamination, so disinfection is not required.

The most common form of