A review of behavioral factors involved in the development and continued performance of stereotypic behaviors in pigs

Abstract

Environmentally induced stereotypies, commonly observed in farm and zoo animals, are behaviors that are relatively invariant, that are regularly repeated, and that serve no obvious function. However, there is as yet no accepted means of discriminating between normal and abnormal behavior, and the assumption that stereotypies are abnormal may mask the fact that they arise in part through processes that "normally" control behavior. There is growing evidence that stereotypies in sows and broiler breeders are strongly related to feeding motivation. For example, sows only develop oral stereotypies if their feed intake is restricted, and operant conditioning experiments have shown commercial levels of feed restriction to give rise to high levels of feeding motivation. Stereotypies in animals whose feed intake is restricted largely occur in the postprandial period, and ingestion of food has specifically been shown to elicit stereotypies in sows. These observations suggest that positive feedback from feeding produces a short-term increase in feeding motivation that at the end of the meal is directed toward available, alternative stimuli such as chains, the choice of stimuli reflecting the sensory feedback from the activity. Drinking behavior may also become an expression of feeding behavior after metabolic water requirements are met. In addition to these processes specific to feeding motivation, it seems likely that nonspecific processes, which operate more generally across motivational systems, contribute to the persistence of the behavior. Behavioral arousal may facilitate performance of active behaviors, and sensitization of the underlying neural elements may lead to the behavior being more easily elicited and maintained. A crucial factor in the sensitization process would seem to be the channeling of complex behavior by the environment into a few and very often repeated sequences of behavior. This approach suggests that stereotypies can be prevented by either reducing the level of motivation underlying the stereotypy, or by allowing for the expression of more complex behavior and thereby preventing the processes of channeling and sensitization from occurring.

Group housing during gestation affects the behaviour of sows and the physiological indices of offspring at weaning

“…Sham chewing and other non-feeding oral activities were classified as stereotypical behaviour, and sham chewing is most likely the most detrimental stereotypy because it is considered to be in a more advanced stage of development (Stolba et al, 1983;Lawrence and Terlouw, 1993;VieuilleThomas et al, 1995). Stereotypical behaviour was mainly performed during 2 h following feeding, and it is always higher in the stalls (Jensen, 1988;Chapinal et al, 2010).…”

Provision of straw as a foraging substrate reduces the development of excessive chain and bar manipulation in food restricted sows

“…Recently, Lawrence and Terlouw ( 1993) suggested that food restriction and the inability to express resulting foraging behaviour is one of the main causes for the development of stereotypies in sows. They argue that in food-restricted sows the positive feedback effects of feeding in the early stages of a meal (Wiepkema,197 1) overrules the negative feedback from ingestion of nutrients.…”

“…This 'channelling' of complex behaviour into a few repeated sequences could be an important prerequisite stage in the sensitisation of underlying neural elements (Dantzer, 1986)) which would allow stereotypies to be more easily elicited and maintained. Lawrence and Terlouw (1993) hypothesise that there are two methods of preventing stereotypies from developing: by reducing the level of feeding motivation, or by allowing the expression of more complex behaviours to prevent the channelling process. The present study was designed to investigate this hypothesis.…”

Effect of locomotion score on sows’ performances in a feed reward collection test

“…To achieve this goal, we used a reward that had great incentive value because it was highly palatable and because our sows were fed at commercial feed levels, which satisfy only about 40% to 60% of their ad libitum feed intake (Brouns et al, 1995;Meunier-Salaün et al, 2001). Such commercial feeding levels are known to leave sows hungry (Lawrence et al, 1988;Lawrence and Terlouw, 1993). Both feed deprivation (Robert et al, 1997;Patterson-Kane et al, 2011) and good palatability (Baldwin, 1976) are known to increase feeding motivation in sows.…”