Pigs are conspicuously sensitive animals who require special attention to guarantee their physical and behavioral well-being in the often stressful environment of a research institution. A stressed pig will yield stressed research data of little or no value, while a well kept and carefully handled pig is more likely to yield reliable research data of scientific value.    

• Provide pigs with roughage such as oat hulls and straw so that the animals can perform foraging activities and fill their gut. Abnormal behaviors in pigs can be prevented or ameliorated by the provision of straw (van Putten, 1980; Arellano et al., 1992; Arey, 1993; Whittaker et al., 1998). Long natural straw is more effective than chopped straw. If experiments last more than a few weeks, avoid using pigs who have been bred for rapid weight gain and consequently have such a high feeding motivation that supplemental roughage may not satisfy them. Such animals are susceptible to developing stereotypical behavior and experiencing impaired well-being if they are kept on a calorie-restricted diet (Appleby and Lawrence, 1987; Terlouw et al., 1990).
       
• Enrich the environment of pigs to counteract frustration and boredom resulting from chronic understimulation. A barren concrete floor offers no stimulation, and it may cause discomfort and pain resulting from foot and joint irritations and inflammations. This is most likely to be a problem in lean hybrids. The author has observed that some breeding companies do not select for sound feet and legs. They have selected for rapid lean growth and have ignored other important traits such as structural soundness (Grandin, 1998). Keep the animals on straw bedding (cf. figure 3) to reduce physical discomfort and the risk of leg injuries, to promote foraging and rooting behaviors and to stimulate exploratory and play behavior (cf. Lay et al., 2000). Evidence suggests that pigs kept in a barren environment use penmates as substitutes for substrates leading to harmful social behavior (Buré, 1981; Hughes and Duncan, 1988; Fraser et al., 1991; Burbidge et al., 1994). Some lean hybrids have a more excitable disposition and they are more likely to engage in ear sucking than fatter types of pigs when they are housed on an unbedded concrete floor. This has to be avoided by all means. If extreme cleanliness is required, provide the pigs with suspended tires and hanging rubber hoses to play with and to chew on. Such objects can easily be sanitized.
  
       Pigs will avoid enrichment objects that are contaminated with manure. To solve this problem toys should be suspended over the pens with rope or twine. This keeps them clean and still will allow the animals to manipulate them almost as freely as though they were on the floor of the pens (Grandin, 1986). Chains are not very attractive enrichment gadgets for pigs (Horell and Ness, 1995; Hill et al., 1998). Pigs will play with chains, but they prefer to play with pliable objects when they are given a choice (Grandin, 1988). Cloth strips are particularly effective enrichment items (Grandin and Curtis, 1984). Strips of old bedsheet about 3 in. wide and 24 in. long can be easily tied to the fence and replaced when they get dirty (Figure 1). Environmental enrichment will make the animals calmer and less likely to be startled by sudden noise (Grandin, 1986; Grandin et al., 1987) or by people (Pearce et al., 1989; Moore et al., 1994). Pigs who are distracted in species-adequate ways will also show less apathy and engage in less stereotypical (Apple and Craig, 1992; Haskell et al., 1995) and anti-social activities (Schaefer et al., 1990; Arey, 1993) such as biting (Fraser, 1975; Beattie et al., 1995) and chewing ears and tails of their penmates (van Putten, 1979; Simonsen, 1990; Beattie et al., 1993).

Figure 1. Author petting pigs. Contact with people produces calmer animals. The white cloth strips provide the pigs with opportunities for chewing and playing. The animals prefer soft pliable enrichment objects such as cloth strips to hard objects such as chains.

    

• Preparturient sows must have access to straw (Figure 2). The importance of straw approaches that of feed, particularly during the 24 hours before farrowing when sows are highly motivated to build a nest for their young (Arey, 1992). The performance of nest-building behavior is in itself reinforcing independent of functional results (Hutson, 1992). An argument against straw in the research laboratory is the possibility of straw clogging drainage systems; a trap on the drain can readily avoid this problem (Batchelor, 1991).

Figure 2. Preparturient sows have a strong instinct to build a nest for their piglets (Photo by Diane Halverson, Animal Welfare Institute, Washington, DC).

• Provide pigs with regular positive human contact in their home pens. Attending care personnel should enter the pens every day and interact with the animals by allowing them to approach without fear and by stroking them firmly and talking to them gently (Figure 1). This will produce calmer animals who will be less fearful of humans (Tanida et al., 1995) and less excited and less stressed during research procedures (Grandin et al., 1983). The author has found that playing a radio at a reasonable volume helps to prevent excitement when pigs hear a sudden noise. Choose a station with a variety of talk and music. A radio with a lot of talk gets pigs accustomed to human voices.
      
• House pigs in groups to account for their strong social disposition. Keeping the animals in compatible groups is a safeguard for their behavioral health and general well-being (Figure 3). Avoid disrupting the composition of the group; this will help the animals to form stable social relationships and avoid aggressive conflicts. Provide the animals sufficient space and visual barriers to minimize aggressive conflicts arising from confinement. Housing with increased space allowance and partial stalls has welfare advantages in the long term, on the basis of decreased aggression, reduced cortisol concentrations and increased immunological responsiveness (Barnett et al., 1992; Waren and Broom, 1993; Andersen et al., 1999). A minimum space of between 2.4 and 3.6 m²/adult pig is necessary to avoid undue, injurious aggression and hence promote good welfare (Weng et al., 1998).

Figure 3. Pigs have a need for social companionship. Access to straw will help prevent behavioral problems (Photo by Diane Halverson, Animal Welfare Institute, Washington, DC).

    

      Pigs form stable groups, but there is a tendency to fight if unfamiliar animals are placed together. Tailbiting and overt aggression are common results of mixing, particularly if done in confined spaces. To avert this, pigs should be mixed on neutral territory (Wolfenshohn and Lloyd, 1994). There are welfare advantages in reducing aggression by grouping unfamiliar adult pigs after dark and subsequently providing ad libitum food to reduce aggression at feeding (Barnett et al., 1994).

• When a pig has to be removed from the home pen for a research procedure, always take another familiar pig along. Pigs are social animals who quickly become apprehensive, agitated, and distressed when they are separated from their herdmates.
   
• Do not house pigs alone unless there is a good veterinary reason or an IACUC-approved research reason for it. If the research protocol requires temporary single-housing, allow the animal to keep visual contact with other familiar pigs to mitigate negative long-term effects of isolation (Herskin and Jensen, 2000). If this is not possible, provide the pig extra physical contact with a friendly, familiar person. Patting a pig is not a waste of time because it improves scientific methodology by making the animal feel more at ease and increasing his or her coping capacity in a potentially distressing situation (Geers et al., 1995).
        Provide single-housed animals enough room not only to lie fully relaxed without head or nose touching the feeder but also to turn around freely.
   
• Allow the pigs to run up and down the aisle at least once a week. This gives the animals some extra exercise and reduces their fear when they have to be moved from their pen to another location. Moving pigs in the aisle and walking through their pens every day will make the animals easier to handle (Abbott et al., 1997; Grandin, 2000), thereby minimizing or eliminating data-biasing stress reactions.
     
• Do not subject pigs to forced movement and handling procedures. Pigs are intelligent animals and - with a good understanding of their species-typical behavior and sensory physiology - can be readily trained to cooperate during common research procedures. When training pigs to work with rather than against you, never punish them but reward them with highly palatable treats. The training does take a little extra time, but researchers who have used trained pigs in their laboratories find that the benefits are worth the time investment. Trained animals experience less stress and hence provide more reliable research data. Needless to say, a well-designed training program also serves as a mental stimulation not only for the pigs but also for the care personnel. 
   
• Do not tether pigs. Being tethered is a chronic stress situation for them (Barnett et al., 1985; Barnett et al., 1987; Schouten et al., 1991), which is likely to negatively influence research data.
     
• Pigs should not be restrained unless it is absolutely necessary. The animals must be completely tamed and acclimated to people before being trained to accept a restraint device. Slings make the best restraints for pigs. The pressure on the belly seems to have a calming effect. When sling-restrained, most Yucatan miniature swine will not only lie quietly but often sleep during the experimental procedures (Panepinto et al., 1983). Pressure on the side of a pig's body will cause the animal to relax (Grandin et al., 1989). The time period of restraint should always be the very minimum required to accomplish a specific research objective (National Research Council, 1996).

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Temple Grandin wrote her widely recognized Ph.D. thesis on the effect of rearing environment and environmental enrichment on behavior and neural development in young pigs. Sheis Assistant Professor of Animal Science at Colorado State University. Her extraordinary sensitivity for the needs of animals have made her an internationally respected consultant to the livestock industry.

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