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Chapter 19 Management of growing pigs.

INTRODUCTION

The stockperson cares for the growing pigs (the term "growing pig" in this chapter refers to both nursery [wean plus 4 to 12 wk] and growing-finishing pigs [8 to 12 wk post-nursery until market]). Workers on commercial farms have a significant challenge to care for individual pigs. More often, workers may view pens and barns full of pigs rather than viewing individual pigs. While a small operation may have only a few growing pigs to care for, modern commercial farms have one employee per 1,000 pigs per hr of work. In traditional pork production, a worker grinds and mixes the feed, cares for sows and nursing pigs, repairs fences and pens, manages the manure, and takes care of any other problems that may arise. In modern corporate pork production, the workers who are assigned care of the growing pigs provide animal care as their primary job responsibility. If they need feed, they call the feed mill; if they need plumbing or electrical repairs, they perform triage and then call the maintenance staff. Manure is the responsibility of others when it leaves the barn.

MANAGEMENT OF THE MODERN GROWER/FINISHER UNIT

Modern technology and efficient pen and barn design have made such advances that one person can care for up to 8,000 pigs in a day. If events such as a disease outbreak or a major equipment failure occur, more than 8 hr/8,000 pigs is required.

To spend 8 hr/d caring for 8,000 pigs or 1 hr/1,000 pigs and to provide good animal care requires an alert, well-trained individual. Assuming that 1/2 hr is spent treating individual pigs or equipment problems, the worker must look at 33 pigs/min, or about 2 sec/pig. The keen observer will find exceptions to the normal in such a quick scan of the pigs and equipment. Noticing and dealing with these exceptions in a timely manner are the keys to success in the growing pig barns. This management style is appropriately called management by exception.

NORMAL PIG BEHAVIOR

Understanding normal pig behavior requires some appreciation of how the pig evolved. The pig's ancestor was a forest-dwelling creature that also foraged in grass if necessary. These pigs preferred to be in social groups and avoided, rather than confronted by other species.

The life of the pig's ancestor was spent searching for food. The search included feeding off the ground and on low plants, and rooting in the ground in search of roots and insects. If these pigs happened on a bit of carrion, they were happy to eat it in its entirety. They were slightly neophobic (fear of eating new things), but they consumed any food that did not make them sick. If they were to come across a field of grain plants, they ate until the grain was consumed. They did not travel unless it was necessary.

To manage the exceptions, producers must be intimately familiar with what is normal. Normal pig behavior is well-known to experienced stockpersons, who often cannot explain what normal behavior is, but they can recognize it and move their eyes to other areas in their search for abnormal exceptions. Understanding normal pig behavior is in the best interest of the growing pig caregiver.

MAINTENANCE BEHAVIORS

Figure 19-1 shows data on the maintenance behaviors (feeding, drinking, lying) of indoor pigs. They spend a large amount of their time (80% or more) lying down. About half the lying-down time is spent sleeping. Over time, as the pigs consume larger, but less frequent, meals they spend more and more time lying down and less time eating. Ad libitum-fed pigs spend 20% of their time active when in the nursery, but only 12% active 4 mo later in finishing. The increase in time spent lying comes almost entirely from a reduction in time spent feeding.

The pattern of behavior changes with time of day. Pigs show clear cycles in behavior with some active and some inactive times. The hours of activity depend on the feeding system, the thermal environment, and, to some degree, the genetic line. Genetics, however, is more likely to change the overall level of behavior and not the daily rhythm. Some lines, such as the Meishan, are less active than European breeds (see Figure 19-2). Even when the Meishan influence is diluted to 25% through crossbreeding, the crossbred pig is less active than more traditional crossbred pigs.

FEEDING BEHAVIORS

Pigs feed in discreet meals throughout the day (see Figures 19-3 and 19-4). A pattern of nursing is established in about 24 hr. Nursing occurs about once/hr (each 45 to 50 min) in a synchronized manner at least until 4 wk of age. Piglets can eat more milk in a given meal than the sow's udder can provide. After weaning, domestic pigs, unless provided with creep feed before weaning, are unwilling to eat the dry feed. Later, with ad libitum access to feed, pigs will eat larger meals less often during the day. They would not have enough space and time to eat once/hr with the amount of feeder space usually provided. Even with a wide-open trough, they would synchronize their feeding to some degree after weaning. Growing pigs naturally tend to eat in groups.

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The feeding behavior of pigs is facilitated by their pen mates. This increase in feeding associated with being in a social environment is called social facilitation. Social facilitation of feeding should take place among group-housed growing pigs as long as the feeding space is neither too limited nor in excess. Some individual pigs who are socially submissive will have socially induced lower feed intake, but the majority of pigs will be stimulated to eat more in the presence of other pigs.

In the late 19th century (1888), Harris described social facilitation among growing pigs destined for the fair. He described how he was able to get his prize pig to eat even more feed than its normal ad libitum intake. The prize pig was given enough feed to eat until it was full and stopped eating. A second, skinny and hungry pig was let in the pen and ran over and ate feverishly. The excited feeding of the hungry pig caused the prize pig to eat a bit more. Harris was using social facilitation to increase the prize pig's feed intake. Pigs of a given genetic line fed a given diet will have a repeatable pattern of feed intake. Feeding patterns are described by the numbers of meals or feeding bouts/d, the feed intake/meal, and the total intake/d.

Feeding patterns may change with age. As pigs get older, they eat fewer, but larger, meals. If given enough room to eat simultaneously, pigs will develop a circadian pattern of feed intake--eating more meals during the day than at night. As feeder space becomes limited, more pigs must eat at night and the group pattern becomes flat (no peak of feeding in the day hours).

Growing pigs eat 1 to 8 meals/d. Each meal may be from 0.1 to 2 lb (0.05 to 0.9 kg) and will require 2 to 15 min/feeding bout for the usual grain-based feeds. With some less-dense feed, feeding may require several hr/d.

The fact that pigs of a given genotype eat more or less meals/d does not mean that the overall feed intake will be increased or decreased. In one investigation at Texas Tech University, Berkshires ate more meals/d than did pigs of Duroc or a commercial crossbred line (see Figure 19-4). Although the Berkshires ate more meals/d, they ate less feed/meal. The overall feed intake (lb/d) was similar for all three genotypes.

Managers must understand the normal feeding pattern of the pigs in their charge. When "normal" is understood, exceptions to normal can be identified more easily.

Feed intake declines during warm weather and is noticeably depressed above temperatures of 85[degrees]F (29[degrees]C) for pigs 100 lb (45 kg) and above. Younger pigs can grow and behave normally at warmer temperatures.

Feed intake tends to increase when the air temperature is cooler. Pigs use some of the feed to burn as fuel to keep their bodies warm. The increased feed intake in cool temperatures is associated with a progressively lower feed efficiency. In this case, from an economic point of view, the cost of feed as a fuel should be considered carefully.

DRINKING BEHAVIORS

Pigs require water to sustain life. They will drink from streams, cups, and bowls, bite nipples, and drink from almost any available source. Pigs do not unequivocally prefer clean water. For example, outdoor pigs are often observed drinking from a lived-in wallow when clean water is available nearby. However, clean water should be provided so they can remain healthy. Some have suggested that pigs prefer drinking clean water over dirty water. Preferences are complicated to interpret and other factors may interfere with a given choice (e.g., difficult, uncomfortable, or remote accessibility). Pigs may then seem to "prefer" to drink dirty water. Pigs often drink when they eat. Being normally fed dry feed, they alternate between eating and drinking. If water intake is limited, feed intake will become limited.

DUNGING BEHAVIORS

Pigs do not defecate and urinate in a random manner. They seem to have reasons, or at least preferences, for their dunging behavior. Pigs defecate when they are frightened or in a new environment, but in their home pen, pigs defecate and urinate in a relaxed and calm manner, away from most pigs and away from the feed. They may defecate against a wall or in a corner because the chances of disturbance are minimal. Other pigs investigate their pen mate's defecation and urination behaviors using their senses of smell, taste, and touch.

When given enough room, pigs establish clear areas of the pen for different uses. A well-designed pen has areas for feeding, drinking, resting, and dunging. Pigs ordinarily will not dung where they eat, but rather do so in a wet or cold area away from their feed. They may, however, dung near their water supply. During thermoneutral and cool temperatures, pigs urinate and defecate in the wet and cool areas of the pen.

During these times, they rest in the dry, warm parts of the pen. In warm weather, pigs may lie in the wet places in the pen and become dirty as the result of resting and wallowing in manure. Pigs do not avoid manure and will use feces and urine as they would use mud to cool their skin during warm weather.

When pigs live on totally slatted flooring, they have a difficult time establishing clear dunging areas, although they still try. On a totally slatted-floored pen, pigs may defecate against a wall to attempt to establish a clear area for dunging.

Changing the defecation pattern is difficult. The job of directing them to eliminate in the desired place is easier, if producers plan ahead, than it is to try to change their elimination behavior. When pigs are first introduced into a partially slotted pen or into a pen in which a producer wishes to shape the pig elimination pattern, water should be applied where defecation is desired (e.g., over the slatted area). Directing cool air currents over the desired area will help make the area cool. Feed should be sprinkled on the floor where elimination is discouraged. These actions will discourage the pigs from defecating in the area with feed--they will rest in these places.

CHEWING/ROOTING AND PLAYING

Pigs spend 10% to 50% of their waking, active times chewing and rooting with objects and animals in their environment. Pigs explore their environment through their senses and they will taste any new object in the pen. While it is easier for them to chew and root on soil, they will chew and root on any material available to them, including concrete flooring and stainless steel feeders--any material in the pen will become the focus of their attention.

A moderate amount of chewing, rooting, and playing with equipment is normal pig behavior. An excess of chewing may be the result of unintended selection or some dietary deficiency. Mineral deficiency has been blamed for excess chewing, but this has not been clearly demonstrated. When chewing and exploration become either too intense or too reserved, the stockperson should seek causes in the diet or the environment.

SICKNESS BEHAVIORS

When pigs become sick, their behavior changes. During the early hours after exposure to a pathogenic microorganism, a cascade of metabolites is produced that includes some immune cell cytokines. These cytokines travel to the brain to cause sickness behavior.

The behavior of sick pigs varies with the type of illness, but some general trends can be described. Sick pigs eat less and may drink less. They spend more time lying and their appearance is often different. They may have a hunched-up or hunched-over look. Their hair may be raised and appear rough. Sick pigs often lie down and their apparent resting behavior can be mistaken for healthy resting when they are actually ill. The stockperson with a keen eye is able to detect the very early signs of sickness and will begin interventions (such as antibiotic treatment or adjustment of the thermal environment) during the early stages of sickness.

DAILY PIG MANAGEMENT

Each operational unit on a swine farm should develop standard operating procedures (SOPs) for the daily care of the animals. The SOP for growing pigs should include at least a careful, daily observation of each pig. A second, quicker walkthrough later in the day is desirable.

On some farms, stockpersons look at the pigs from the aisle while on others, they enter each pen each day for a closer observation of individual animals. On many well-managed farms, the caregivers enter each pen each day and ensure that each pig can stand, walk, and move with ease. The SOPs should state exactly how much human contact is to be provided each day.

WHAT IS STOCKMANSHIP?

Peter English and his colleagues (1992) have given considerable study and thought to the description of stockmanship, especially with pigs. They suggest good stockmanship involves a combination of:

* A sound knowledge of the pigs and their requirements

* A basic attachment and patience for the pig * The ability and willingness to communicate and develop a good relationship with the pigs (empathy)

* The ability to recognize individual animals and to remember their particular eccentricities

* A keen sensitivity for recognizing slight departures from normal behavior of individual pigs (perceptual skills)

* An ability to organize working time well

* A keen appreciation of priorities and a ready willingness to attend to individual animals even if it disrupts the schedule

Successful animal workers provide sound stockmanship or animal care. They know their pigs and their pigs know them. They know when to follow the routine and when intervention is needed. They know how to handle pigs in a routine manner and how to handle the occasional difficult pig. The good caregiver has a work-day flow that is logical and efficient, but is flexible enough to be interrupted for reasons of providing sound animal care.

People are not born with skills of good stockmanship, but some people are better suited to provide animal care than others. With proper training, people with the predisposition to care for pigs can develop into outstanding pig caregivers. These stock-people are an important asset to the successful farm.

Today, many large farms have multiple units of 1,200 or 2,400 sows. These units have identical pig genetics, nutrition, and housing. The difference between the best and worst units is in the people. How they care for the pigs and how they interact with each other (people skills) determine their success. Some of the success is a function of how well they were trained--people do not often become outstanding caregivers without some training.

POSITIVE HUMAN-PIG INTERACTIONS

How human caregivers interact with their pigs can have significant effects on pig behavior and productivity. Pigs on each farm will have a pattern of behavior that is shaped by the animal workers. Some of the behaviors exhibited by pigs include:

* Fear, due to being abused (even mildly)

* Fear, due to no human exposure

* Neutral toward people

* Comfortable around people

* Aggressive toward people

Pigs that are dealt with in a crude or mean manner, even in passing, will develop a fear of people (see Figure 19-5). Pigs have good memories and they will generalize their fear of one person to other handlers. Pigs that have an intense fear of humans may have been shocked, prodded, kicked, slapped, or beaten. These fearful pigs will avoid people and some individual pigs may actually scream when people are near or when people touch them. Some of this extreme pig behavior may have a genetic component, so one should not automatically assume that screaming and fearful pigs were abused. Most likely, these behaviors are caused by a combination of a predisposed genotype and hostile treatment.

Pigs that are not handled often by people show a different type of fear of humans. These pigs have a very large flight zone (the closest a person can get to a pig before it flees). When a person approaches these pigs, they run away in fear of the unknown. Pigs on some commercial farms show this extreme flight zone. These pigs are easy to handle in well-designed facilities, but they can be very difficult to handle in poorly designed facilities where an individual pig can get turned around and, thus, disrupt the flow of animals in the desired direction.

Pigs that are neutral toward people are very uncommon. These pigs will have an intermediate flight zone and express a middle level of fear toward people.

Pigs that are comfortable around people have had many experiences with people and the majority of experiences were positive in nature. Positive experiences include people touching, stroking, petting, and talking to the pigs. The pigs may actually move toward people and, therefore, they may have a negative flight zone, which may cause an increased time required to move pigs through chutes and races.

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Some pigs that are very comfortable around people are problematic. These pigs seem to think people are something to chew on, play with, or eat. They do not so much bite, as chew, on people. They start with chewing on shoes, boots, or pant legs and graduate to chewing on legs or arms. These pigs increase their aggressive chewing the longer people are in the pen. Working with equipment in the pen is very difficult with aggressive pigs. Some genetic lines may show this increased aggressive behavior more than other lines.

The Fear Test

Australian researchers developed a simple test to determine the relative level of fear among pigs (Coleman et al., 2000). In the fear test, a person abruptly places a hand in the direction of the head of an awake pig. The pig's normal reaction is to step back. The person then times how long it takes for the pig to return to the still hand and to touch the hand (or alternatively, to get within 6 in (15 cm) of the hand). The greater the pig's fear of people, the longer it will take for the pig to return to the hand. Pigs that have had limited positive experiences average about 1 min. Pigs that take longer than 2 min have a significant fear of people. Some genetic lines and some environments may require an adjustment of normal and fearful times.

How much human interaction is best for growing pigs? This question has not been answered fully, but the simple answer is that minimal human contact is needed. When human interaction is required, handlers should make the interactions as positive as possible.

When human interaction is required, make the interactions as positive as possible.

Researchers have examined how different levels of human interaction impact pig behavior and productivity. In one study, Hemsworth et al. (1987) showed that pigs handled in a positive and pleasant manner had improved ADG and F:G ratios compared with pigs handled in an unpleasant manner (see Figure 19-6). Inconsistent handling was nearly as bad for pig performance as unpleasant handling.

One interesting insight into the Hemsworth work was that pigs handled in a minimal way had fairly good ADG and F:G ratios. This finding supports the argument that if some unpleasant experiences are necessary (injections, ear tagging, etc.), it may be better to handle pigs infrequently or in a minimal manner to minimize the stress reaction when pigs see people approaching. When faced with the need for pleasant handling in a consistent manner, many farmers choose to provide only minimal human-pig interactions.

Scientists at Texas Tech University have studied the effects of positive human interactions and use of toys (suspended chains and hoses) in growing pigs. Hill et al. (1997) recently completed an investigation of the efficacy of toys and/or positive human interaction. They compared the following treatments:

* Negative (Neg) control (nearly zero human contact)

* Control (Con) (once/d quick walkthrough the pen; once/wk a longer time was spent adjusting equipment)

* Toys (same as control, plus two hanging chains and two hanging hoses)

* Human (positive human interactions, 2 min per pen per day, 5 d/wk)

* Toys + human (same as each of the above)

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In this work, there was a large effect of handling on pig behavior during standardized tests. For example, the data for pigs that had little or no human contact showed clearly that they avoided humans (see Figure 19-7). They did not avoid people because they were abused, but rather because they were unfamiliar with people, especially at close range.

Hill et al. (1997) used two genotypes in their work. The Camborough-15 (C-15) is a common, crossbred maternal genotype. The Exp-94 contains 25% Meishan. The C-15 showed no performance boost or decline with different levels of enrichment (see Figure 19-8). The Exp-94 line did respond to enrichment in certain ways. The 25% Meishan genetic line increased its ADG and improved its F:G ratio with provision of toys. However, the body fat percentage increased with more enrichment for both genotypes. In fact, provision of toys increased backfat by 12%. Packers would pay a premium for carcasses with lower backfat thickness and, therefore, producers would be discouraged from providing toys. Also, the "Neg" treatment, wherein human caregivers did not enter pens, would be the lowest labor input. Furthermore, these pigs were easy to handle in that they moved away from people in handling tests.

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Pork producers must weigh animal welfare concerns against economic concerns (pig performance, body composition, and labor costs). The balance between pig welfare and economics is not yet clear, although there is general agreement that achievement of animal well-being is often associated with economic costs.

BEHAVIORAL PROBLEMS

TAIL BITING AND EAR CHEWING

The majority of growing pigs in pens and buildings have few behavioral problems. Most farms have an occasional behavioral problem that expresses itself as an acute outbreak varying in degree and with unknown cause. Other farms have chronic behavioral problems.

Chronic behavioral problems include, but are not limited to, tail biting, ear chewing, navel sucking, belly nosing (persistent inguinal thrusts), massage, excessive human-directed chewing/biting, hyperactivity, and hypersensitive syndrome.

The most pervasive form of behavioral problem is the tail-biting and ear-chewing syndrome. Van Putten (1969) suggested that tail biting occurs when pigs take the tail of another in their mouth sideways, while cannibalism involves pigs chasing a victim around the pen and chewing as they chase. Tail biting leads to cannibalism. Cannibalism occurs when an animal of one species eats part or all of the body of an animal of the same species. When pigs show excessive tail or ear chewing, they are clearly exhibiting cannibalism. Opinions differ as to when idle chewing turns to cannibalism. However, pigs with bloody stumps for tails or ears indicate that a tail biting-ear chewing episode is clearly cannibalistic. After healing from an extreme outbreak, these pigs will have no tails and no ears.

Pigs groom, rub, nibble, and chew on one another as forms of social and maintenance behaviors. Most oral-body interactions are around the head and the analgenital regions. The head grooming focuses on the ears and eyes. The posterior interactions focus on the tail and anus (in prepubertal pigs). The natural chewing, rooting, and grooming sometimes progress to a more persistent chewing. When the skin is broken and blood is spilled, the chewing pig receives a reward and his/her chewing may increase.

As the syndrome develops, it moves from occasional chewing to persistent chewing. The chewed-upon pig seems to accept most of the chewing, with only an occasional scream of discomfort. Meanwhile, other pigs may join the chewing of the unfortunate victim. At this point, if the victim is not removed, it may bleed to death or it may incur such a massive wound that irreversible infection leads to death or the need for euthanasia. Sometimes the tail infection reaches the spinal cord or the victim suffers direct spinal cord injury. If the chewed-upon pig becomes paralyzed, the others will continue chewing on it and they will certainly kill it. In this case, intervention is needed.

Genetic lines vary in the basal rate of tail biting and ear chewing. In one field investigation at Texas Tech University (McGlone et al., 1992), there was a tail-biting incidence of 5.4% among Camborough gilts and 10.2% incidence among Camborough-15 gilts. Air-flow patterns did not influence the incidence of tail biting, confirming that poor air quality is not a primary cause. Lop-eared pigs (Landrace and Welch breeds) had a higher incidence of cannibalism than did erect-eared pigs (Yorkshire and Large White) (Penny and Hill, 1974).

When genetic lines predisposed cannibalism are uncomfortable, they will begin tail biting. When tail biting occurs, the pigs' tails or tail stumps (if docked) will be down, rather than in the usual up position.

Stockpeople will notice the uncomfortable look among their pigs; this look includes a tail down or tucked between their legs.

Older reports from the United Kingdom showed that the incidence of tail biting was 10% to 12% among undocked pigs (Penny and Hill, 1974). Tail docking clearly lowers the incidence of tail biting. While over 40% of the pigs with intact tails may have tail-biting scars or wounds, only 2% of the docked pigs would have tail scars or wounds. In a recent UK survey, tail-docked pigs had a 21% incidence of tail biting. That the incidence of tail biting seems to be higher in the United Kingdom today than in the United States is speculative, but this may be the case because UK producers use more intact males, they meal feed (rather than ad libitum), and they use more wet feeding systems.

The incidence of tail biting is about twice as common among castrated males as females (Colyer, 1970; Chambers, 1995). The suggestion is that barrows are more hungry and when they have to wait to eat, they are more likely to chew on tails.

Concrete slats clearly increase the incidence of tail biting compared to pigs on bedding. Field studies show that the incidence of tail biting is several-fold higher when pigs are on concrete slats than when they are in straw-bedded pens. However, floor surface and bedding are confounded factors in this syndrome. Most solid-floored pens use bedding and, among finishing pigs, most pigs on slatted floors are on concrete slats. Thus, to be on concrete slats often means to be without bedding. The concrete slats increase the incidence of tail injury (inciting an apparent thirst for blood) and the lack of bedding means a preferred chewing object is not available.

Theorists report (Fritchen and Hogg, 1983; Colyer, 1970; Helms, 1961) causes of the tail-biting and ear-chewing syndromes are often multi-factorial, drawing from one or more categories of:

* Genetic predisposition

* Human management

* Pathogens

* Temperature, humidity, air pressure changes

* Dietary inadequacy

* Wet feeding

* Injury

* Facility design or operation

* Boredom

The entire area of pig behavioral problems suffers from a lack of solid scientific information and controlled studies. One series of studies (Fraser, 1987) showed that a complete deletion of minerals or salts from the diet increases chewing of model tails. However, few cases of cannibalism in the field can be linked to severe mineral deficiencies.

The few studies in the literature on cannibalism often contradict one another. Therefore, determining the cause, prevention, and treatment of behavioral problems becomes a matter of professional judgment. Of the putative causative factors, the following factors have been shown to not cause tail biting in controlled studies:

* Crowding (McGlone and Nicholson, 1992)

* Limited feeder space (McGlone and Nicholson, 1992)

* High atmospheric ammonia or CO2 (Ewbank, 1973)

* High nutrient density (Ewbank, 1973)

* A lack of toys (giving hanging chains or hoses did not reduce tail biting; Hill et al., 1998)

* Lack of dietary magnesium (Krider et al., 1975)

Factors that predispose pigs to tail biting include:

* Viral or bacterial infections (ex., TGE, PRRS, hemolytic Streptococcus)

* Dirty pigs with feces covering their bodies for various reasons

* Concrete slotted floors/lack of bedding

* Meal or limit feeding and wet feeding

* A genetic predisposition

Some potential remedies to an outbreak of tail biting or ear chewing include:

* Provision of a small amount of chewing material, such as straw or earth in a handful on the floor or in a hanging basket

* Moving the biter pigs out of the pen and isolating the badly chewed pigs

* Addition of MgO (0.1% to 1%) to the diet

OTHER BEHAVIORAL PROBLEMS

Other behavioral problems that are less of an industry-wide concern than tail biting and ear chewing include pacing, rocking, rubbing, pawing, sham chewing, bar or fence biting, excessive drinking (polydipsia), self-mutilation, urine or prepuce sucking, belly nosing, anal massage, mounting, unresponsiveness, and its opposite, hysteria (Fraser and Broom, 1990). The suckling-related behaviors (urine sucking and belly nosing) are often symptoms observed in early-weaned pigs. These behaviors often pass as the pigs mature. Other abnormal behaviors are shaped by features of the environment; for example, frequent drinking develops if the water pressure is low. After the problem is resolved, polydipsia may have been created or shaped. If the equipment has sharp edges, pigs may seem to self-mutilate to obtain resources (especially feed and water). Removing the sharp edges should solve the problem.

On a given farm, some of these behaviors may be a significant problem. However, their incidence on most farms is insufficient to call them a behavioral problem.

MIXING, SIZING,AND SORTING

When pigs that have no experience with each other are first grouped (mixed), they fight to establish a dominance order. Pigs in group sizes up to about 20 individuals have a clear dominance hierarchy. Dominant pigs occupy preferred resting, feeding, and drinking places. Some pigs are more dominant over certain commodities within the pen (such as a given resting place). With about a 75% accuracy, pigs dominant for one resource are dominant for other resources.

Pigs will fight for a period ranging from hours to days after they are regrouped. Pigs in small, group-sized pens will establish a dominance order in 4 to 8 hr. Intermediate group sizes (8 to 30 pigs/pen) will establish a dominance order in about 48 hr. Very large groups may never fully establish a stable dominance order--they may fight a very small amount of time during most waking hours, or they will establish subterritories in the pen in which they maintain stable dominance orders.

The dominance order is linear in small group sizes with a clear, socially dominant, intermediate, and submissive pig. In larger group sizes, many pigs occupy the middle of the social order and participate many social triangles. In any group size above three pigs/pen, the dominance order is nonlinear.

When pigs of uniform body weight are grouped, some individuals become dominant. Even a small difference in body weight is likely to lead to the slightly heavier pig becoming dominant. The dominant pigs clearly gain more weight faster than do subdominant pigs. Figure 19-9 presents data from Hicks et al. (1997) that document the effect of dominance status on post-weaning weight gain. This relationship between weight (or weight gain) and social status is difficult to quantify in medium to large group sizes because the dominance hierarchy is not totally linear. However, in any group size, the social status of pigs has a powerful influence on pig growth.

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The effects of mixing and sorting pigs on pig performance are well documented. During the initial stages when pigs are fighting, their feed intake and weight gains are reduced compared to those of pigs of the same weight and age who were not mixed. In the period immediately after weaning, the pigs are not eating much feed anyway and, in fact, the effect of weaning on weight gain is much greater than is the effect of mixing and fighting.

The consequence of mixing increases as pigs get larger. Larger pigs have a greater slowdown in weight gain due to mixing than do smaller pigs. The "costs" of mixing are summarized in Table 19-1. Pigs should not be regrouped after 125 to 150 lb body weight--this will cause a significant growth check. At all times, mixing pigs causes injuries and wounds that can become infected. Mixing pigs beyond weaning should be avoided when possible.

Methods of reducing fighting among growing pigs have been studied for the past few decades. Two solutions to fighting have been published. The first involves use of hiding areas for pigs--areas where pigs can place their head and ears. With their heads hidden, other pigs will not attack them (McGlone and Curtis, 1985).

The odor of a boar (5-[alpha]-androsten-16-en-3-one) in very low concentrations will reduce fighting among growing pigs (McGlone et al., 1986). However, this compound is not approved for use with commercial pigs and the economic return to develop this market is not great enough to cause development of the product. Other remedies such as masking odors are not effective in reducing fighting.

In some countries, tranquilizers are given to pigs to reduce fighting or to reduce the stress of transport. Mind-altering drugs provide only a temporary solution to the problem of fighting. When the pigs recover, they may resume fighting and, in the end, the same total amount of aggressive behavior may occur.

TAIL ENDERS

Due in large part to the social hierarchy, pigs will establish a certain amount of variation in body weight. Even in pigs that are tightly grouped by size, the social order will cause a spreading of weights in the group. For this reason, sorting pigs by size is recommended only to group the very large and very small pigs together. Mixing pigs is only recommended at weaning. After that, further mixing does not have an economic advantage.

Regardless of the amount of mixing of pigs, those of a common age will vary in weight at the same number of days of growth. At 160 d of age, pigs may weigh more than 70 lb. The normal way to send pigs to market is to send them over a 3- or 5-wk period. Then the last group of pigs, called the tail enders, will be variable. These pigs should either be sold for a reduced price for slaughter or they should be moved to another site to add weight. The entire building's biosecurity should not be compromised to allow these few pigs to grow. The tail enders must be dealt with in a manner that utilizes expensive building space and does not compromise biosecurity (finishing buildings should be managed all-in-all-out, if possible).

HANDLING PIGS

Some general principles should be understood when handling pigs during weighing, sorting, or moving:

* Pigs have good memories (they remember good and bad experiences).

* Pigs will follow other pigs.

* Pigs will explore as they go (they will explore unique lighting, smells, surfaces, sounds, and other animals).

* Restraint is very stressful to pigs of all ages.

* Pigs respond to handling or fear by vocalizing and attempting to escape.

* Response: vocalize and escape.

* The reason for restraint has to outweigh the stress reaction.

* There are strong correlates between human attitude and pig productivity.

* A positive attitude toward pigs is preferred.

* Producers can be too positive and this may hurt the pigs and the bottom line.

* Training improves worker attitude and herd performance.

* Touching is good--make sure each experience is positive.

* The stockperson's behavior translates into the pigs' reproductive performance and growth performance.

* Some genotypes are more or less fearful of humans.

When designing loading and moving areas, producers need to consider that pigs have features of the environment that make them comfortable and other features that make them uncomfortable. Pigs move easier if the floor is a solid color with no drains, discolored areas, or other variations. A uniformly lit walkway is also needed for smooth animal flow. Data from a recent study of floor color effects on pig movement are given in Table 19-2. A solid, white flooring caused the easiest, quickest movement onto and over the floor pattern. Any variation in floor pattern slowed the pigs. These data add confidence in the suggestion that floors should be solid-colored and uniform in appearance.

The texture and feel of the flooring to the pigs' feet should be comfortable--a compromise between smooth and nonslip. A slightly abrasive floor is best for sure footing, which allows pigs to walk easier and with more confidence, and reduces the chance of injury.

In addition to the color, lighting, and texture needs, the area into which pigs are moved should be uniform in air currents. Pigs will balk (stop moving or even turn) if they receive a cold air draft while they are moving forward. This represents a special challenge when pigs are going out of a building and into a truck. The doorway may have bright light from the sun and a breeze from the open door. This combination will cause pigs to balk.

DEVICES TO HELP MOVE PIGS

The caregiver has several choices for devices to help move pigs. The handlers' natural (but not the best) method is to clap their hands, whistle, shout, and wave their arms. This technique can do in a pinch, but should not be the usual method used to move pigs.

The traditional sorting board (hurdle) is a solid piece of wood, plastic, or aluminum that has a handle (see Figure 19-10). The board is placed in front of the worker and if a pig turns, the board is placed squarely on the ground, giving the pig the impression that a solid wall is behind it. Pigs will more likely move forward if they are convinced a solid wall is behind them.

[FIGURE 19-10 OMITTED]

[FIGURE 19-11 OMITTED]

Other devices that can be used to move pigs are slappers, paddles, and electric prods (see Figure 19-11). Electric prods are not recommended for pigs of any size. However, an electric prod may be needed when pigs must be moved quickly for their own safety. Farms and processing plants should be designed so electric prods are not needed.

TRANSPORTING PIGS

Pigs need to be transported at ages varying from early weanlings to adults. Care must be taken when transporting pigs to avoid injuries and illness. Shipping is one of the most powerful stressors to a pig and, at times, shipping cannot be avoided. Everything must be done to make the shipping experience as nonstressful as possible.

[FIGURE 19-12 OMITTED]

Trucks should be bedded when pigs are transported. Bedding should be sand or, in the summer, a wetable material. Straw or sawdust is a good bedding in the winter. Transporting pigs in cold weather is usually not a problem, except for very young pigs that must be kept warm. Transporting pigs during very warm weather is a hazard (see Figure 19-12). Pigs should not be transported in the emergency phase of the Livestock Weather Safety Index. Pigs can be moved at night and in the morning hours to avoid very warm temperatures.

SUMMARY

This chapter focuses on the care and management of pigs during the period of growth from weaning at a few weeks of age to slaughter at 5 or 6 mo of age. Pigs exhibit normal behaviors related to maintenance (eating, drinking, lying), excretory activities, chewing/ rooting/ playing, and sickness. Daily pig management, in terms of providing appropriate care and husbandry to satisfy the pigs' normal behavioral patterns and animal well-being, was discussed. Producers must be able to recognize abnormal behavior patterns in pigs and address the causes of such behaviors. The chapter reviewed the general principles of handling pigs and appropriate design and layout of pens, floors, and transport facilities and pig movement devices.

QUESTIONS AND ACTIVITIES

1. Growing pigs react differently if they have been handled extensively in a positive, negative, or neutral manner. A fear test is performed to assess pig "fear" of humans. This is done most easily to sows in gestation crates. The observer places his or her hand in the crate while the sow is standing, but not eating. The observer starts a stop watch. The sow steps back. The observer measures the time it takes for the sow to return within a short distance (_1 in) of his or her hand. Sows with a large amount of fear of people will take longer to return. Using available pigs at your farm, perform the fear test on 10 sows. Calculate the mean and standard deviation of the response time.

2. Find a price grid from a pork packer near you. Weigh a group of late finishing pigs (on two occasions, if possible, 7 d apart). Estimate when the average pig will reach the market weight. How many pigs will fall in the price range that pays the best? Develop a spreadsheet that includes a discount or premium based on the variation of the group of pigs. How many batches of pigs should be marketed (e.g., in a single batch, or over 1 to 4 wk) to optimize dollar income?

3. The flow of pigs through a chute can be very pleasant or it can be very stressful for the pigs and the workers. What is the rate of pig movement in pigs/min if you wish to achieve 1,000, 500, 250, or 100 pigs/hr? What can be done to improve pig flow assuming the physical facility is well-designed?

4. In a study by Sarignac et al. (1997), litters were managed either as individual litters or in a communal manner (piglets could interact) during lactation. After weaning, litters were mixed and the following average number of fights were observed:
Isolated-Indoors  Social-Indoors  Isolated-Outdoors  Social-Outdoors
       5.0              0.0               0.0              0.0


Explain these results.What "normal" agonistic behaviors should weanling pigs exhibit?

INTERNET RESOURCES

Growing pig handling sites:

http://www.gov.mb.ca/agriculture/livestock/pork/swine/bab10s06.html

http://www.grandin.com/

http://www.pighandling.com/

http://www.gov.mb.ca/agriculture/livesock/pork/swine/bab02s23.html

LITERATURE CITED

Chambers, C., L. Powell, E. Wilson, and L. E. Green. 1995. A postal survey of tail biting in pigs in Southwest England. Vet. Rec. 136:147-148.

Coleman, G. J., Hay, M., Hemsworth, P. H., and Cox, M. 2000. Modifying stockperson attitudes and behaviour towards pigs at a large commercial farm. Appl. Anim. Behav. Sci. 66:11-20.

Colyer, R. J. 1970. Tail biting in pigs. Agriculture 77:215-218.

English, P., G. Burgess, R. Segundo, and J. Dunne. 1992. Stockmanship: Improving the care of the pig and other livestock. Farming Press, Ipswich, UK.

Ewbank, R. 1973. Abnormal behaviour and pig nutrition. An unsuccessful attempt to induce tail biting by feeding a high energy, low fibre vegetable protein ration. Br. Vet. J. 129:366-369.

Fraser, A. F. and D. M. Broom. 1990. Farm animal behaviour and welfare. Bailliere Tindall, London.

Fraser, D. 1987. Mineral-deficient diets and the pig's attraction to blood: Implications for tail-biting. Can. J. Anim. Sci. 67:909-918.

Fritschen, R. and A. Hogg. 1983, January. Preventing tail biting in swine (anti-comfort syndrome). NebGuide.

Grandin, T., K. Ernst, D. Ernst, and J. McGlone. 1989. Handling Hogs. Pork Industry Handbook. PIH-116.

Harris, 1888. On the Pig. Guilford: Globe Pequot Press. Guilford, CT.

Helms, H. T. 1961, May 15. Tail-biting in swine: The ecologic approach. Modern Vet. Practice: 56-60.

Hemsworth, P. H., J. L. Barnett, and C. Hansen. 1987. The influence of inconsistent handling by humans on the behaviour, growth and corticosteroids of young pigs. Appl. Anim. Behav. Sci. 17:245-252.

Hicks, T. A., J. J. McGlone, C. S. Whisnant, H. G. Kattesh, and R. L. Norman. 1998. Behavioral, endocrine, immune and performance measures for pigs exposed to acute stress. J. Anim. Sci. 76:474-483.

Hill, J. D., J. J. McGlone, S. D. Fullwood, and M. F. Miller. 1998. Environmental enrichment influences on pig behavior, performance and meat quality. Appl. Anim. Behav. Sci. 57:51-68.

Krider, J. L., J. L. Albright, M. P. Plumlee, J. H. Conrad, C. L. Sinclair, L. Underwood, R. G. Jones, and B. G. Harrington. 1975. Magnesium supplementation, space and docking effects on swine performance and behavior. J. Anim. Sci. 40:1027-1033.

McGlone, J. J. and S. E. Curtis. 1985. Behavior and performance of pigs in pens equipped with hide areas. J. Anim. Sci. 60:20-24.

McGlone, J. J., W. F. Stansbury, and L. F. Tribble. 1986. Aerosolized 5-[alpha]-androst-16-en-3-one reduced agonistic behavior and temporarily improved performance of growing pigs. J. Anim. Sci. 63:679-684.

McGlone, J. J. and R. I. Nicholson. 1992. Effects of limited floor and feeder space on pig performance and tail biting. Texas Tech University Animal Science Research Report T-5-317.

McGlone, J. J., W. Vermette, and G. Larson. 1992. Field investigations of tail biting episodes on a pork production unit. Texas Tech University Animal Science Research Report T-5-317.

Penny, R. H. C. and F. W. G. Hill. 1974, March 2. Observations of some conditions in pigs at the abattoir with particular reference to tail biting. Vet. Rec. 94:174-180.

Sarignac, C., J. P. Signoret, and J. J. McGlone. 1997. Relation mere-jeune, comportement et performances en fonction du systeme de logement et de l'environnement social [Sow and piglet performance and behavior in either intensive outdoor or indoor units with litters managed as individuals or as small social groups]. Journees Rech. Porcine en France. 29:123-128.

Van Putten, G. 1969. An investigation into tail-biting among fattening pigs. Br. Vet. J. 125:511-517.
TABLE 19-1
The Costs of Mixing Growing Pigs.

                            DURATION OF GAIN     ADDED D TO
WEIGHT AT MIXING            DEPRESSION           MARKET

5-40 lb (0.07-18.1 kg)      Not measurable              0
40-80 lb (18.1-36.3 kg)            7 d                  0
80-150 lb (36.3-68.0 kg)           28 d                 0
Over 150 lb (over 68 kg)           28 d                 7+

WEIGHT AT MIXING            OTHER PROBLEMS

5-40 lb (0.07-18.1 kg)      Wounds
40-80 lb (18.1-36.3 kg)     Wounds
80-150 lb (36.3-68.0 kg)    Wounds and injury
Over 150 lb (over 68 kg)    Wounds and injury

Source: Adapted from Grandin et al. (1989).

TABLE 19-2
Time-Naive Finishing Pigs Required to Step on the Floors of
Different Patterns and the Total Time to Walk, Unassisted, Over
4 ft of Floor Length.

                                                     TOTAL TIME
FLOOR STYLE                TIME TO ENTER, S       TO MOVE 4 FT, S

Solid white                       3.8                   16.7
Solid black                       3.5                   28.3
Longitudinal lines               10.9                   52.4
Horizontal lines                 22.3                   58.1
Chevron forward (>)              10.6                   42.2
Chevron back (<)                 16.6                   48.5

Source: Adapted from data from Texas Tech University (Song and
McGlone, 1997, unpublished).

FIGURE 19-1

Behavior of Nursery and Growing-Finishing Pigs Fed Ad Libitum
and Housed on Totally Slotted-floor Pens. Each Pen had Access
to Four Toys (two chains and two hoses) Suspended from the
Ceiling.

Behavior of Growing Pigs

Nursery                Growing-Finishin

Lying       80%        Lying       88%
Feeding     16%        Feeding      9%
Drinking     2%        Drinking     1%
Toy-play     3%        Toy-play     2%

Note: Table made from pie chart.

FIGURE 19-4

Daily Feeding Behavior and Feed Intake for Berkshires,
Terminal Crossbred Pigs, and Durocs. Note That Although
the Bershires Had More Meals/D, Ate Less/Meals, and
This Resulted in about the Same Weight of Feed Eaten/d
as the Other Genotypes of Pig.

Breed of pig       Feeding         Feeding             Feeding
                  bouts/day     intake, lb/day     intake, lb/day

Berkshire           6.8             1.87                0.27
Cross               2.4             1.54                0.66
Duroc               3.5             2.41                0.68
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Title Annotation:SECTION V Pig Production Applications That Make Business Sense; stockperson
Publication:Pig Production, Biological Principles and Applications
Geographic Code:1USA
Date:Jan 1, 2003
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Previous Article:Chapter 18 Management of sows and piglets: before, during, and after farrowing.
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