The development and significance of abnormal stereotyped behaviours in tethered sows

G.M. Cronin

    Research output: Thesisinternal PhD, WU


    <p/>The development and performance of abnormal stereotyped behaviours (stereotypies) by tethered sows were studied in order to investigate the consequences of the behaviours for animal welfare and sow productivity.<p/>In Chapter 2, the behaviour of 36 tethered sows in a commercial herd was analysed to determine the characteristics of stereotypies, and to enable their definition. The proportion of observation time that sows performed stereotypies was related to the stage of pregnancy, i.e. the time spent tethered in the current parity. Sows increased the proportion of time spent stereotyping between 10.00-14.00 h up to day 80 of pregnancy, after which stereotyping decreased.<p/>Chapter 3 describes the process of development of stereotypies in sows after tethering. Sows were initially very vigorous and aggressive in their response to tethering. Stereotypies eventually developed after the sows had passed through a number of distinct stages, termed 1) escape attempt, 2) inactivity, 3) outwarddirected activity and 4) basic stereotypy stages. The median durations (and ranges) of the first 3 stages were 45 min (10 to 180 min), 1 day (140 min to 16 days) and 15.7 days (7.8 to 55 days), respectively. Once a basic stereotypy was developed, random aggressive-like acts were rarely observed. The stereotypies that developed in response to tethering contained components that were directed at features in the sows' external environment (e.g. chains, drinker, bars, etc.), and were in part derived from redirected aggressive acts. Over time, the level of aggression declined and the actions were "rounded off". In stage 4, sows built larger stereotypies through the addition of new elements, although they could always revert to the performance of just the basic components.<p/>It was concluded that environment-directed stereotypies develop as a result of frustration/conflict at being restrained, and the consequent loss of controllability over the environment.<p/>An hypothesis was proposed which implicated endorphins (endogenous opiates) in the development and performance of stereotypies by tethered sows. Evidence to support this hypothesis is presented in Chapter 4. Eight tethered and 3 loose-housed sows were treated with saline and the specific opioid antagonist naloxone on consecutive days. The tethered and loose sows were treated while they performed stereotypies and exploratory behaviours, respectively.<br/>Stereotypy performance levels were reduced in the 2 h following naloxone (median = 33% of the time) compared with saline (86%), but there was no effect on the performance of exploratory behaviour by loose sows. Many of the behaviours performed by the tethered sows after naloxone treatment were similar to behaviours performed by sows in response to initial tethering. Seven of the 8 tethered sows ceased the performance of their stereotypies in the short-term following naloxone. The latency to cease performance was positively related to the "age" of the particular stereotypy.<p/>The results strongly suggest that endorphins may be the factor underlying the development and performance of stereotypies. Endorphins are released in response to stress, and in time, sows may learn to self-stimulate the release through the performance of stereotypies. Stereotypies probably function to reduce the perception of the negative aspects of the real environment, over which tethered sows have no control, and "rebuild" a new and possibly much reduced environment that they control through the performance of stereotypies. The results suggest that sows perceive tethering in a very negative way.<p/>In Chapters 2, 3 and 4, it is reported that the stereotypies of tethered sows contain a certain amount of variability. For example, sows could vary the duration of stereotyped components between cycles of the stereotypy, or even omit components, and so on. Thus stereotypies were found to be considerably more variable than indicated by the classic definition of these behaviours.<p/>It is suggested in Chapter 7 that this variability may be an indication that the sow had not adapted to the stress of tethering. The continued perception of negative aspects in the environment may stimulate the release of endorphins, but also introduces variability into the performance of stereotypies.<p/>Stereotypies are behavioural indicators of past or current poor welfare status, a phenomenon which may be quantifiable via measurement of the degree of variability in stereotypy performance.<p/>Since stereotypies develop out of chronic stress situations, and since it has been reported that chronic stress influences the productivity of pigs, it was expected then that the performance of stereotypies may have consequences for sow productivity.<p/>In Chapter 5, tethered sows in a commercial herd were categorized according to the proportion of observation time between 10.00 and 14.00 h that they performed stereotypies. Within parity x pregnancy stage classes, non-lactating sows were classed as either HIGH or LOW stereotypers if they performed more or less than the mean level. At the farrowing prior to observation, HIGH stereotypers produced larger litters in parities 2 and 3, but smaller litters in parities 5 and 6, than LOW stereotypers. At the farrowing after observation, HIGH stereotypers tended to produce smaller litters in parities 5 and 6 than LOW stereotypers. Low parity number sows were less stable than older sows, in that more than half of the younger sows observed in successive parities changed stereotypy performance class between observations. Hence, the effects of stereotypy performance level on litter size of low parity number sows at the farrowing after observation were not consistent with those from the farrowing before observation.<p/>Contrary to expectation, the LOW stereotypers also tended to be less reactive to novel stimuli than HIGH stereotypers, suggesting that the former sows were "less normal" than the latter. The results further suggest that sows may be subject to chronic stress for at least 2 to 3 parities before adapting to tether housing. Young sows that were able to develop a stereotypy more rapidly (i.e. HIGH stereotypers), coped better in the short-term than LOW (non-coping) stereotypers.<p/>In Chapter 6, the metabolic rate and behaviour of sows were measured. The 2 treatments of sows had different degrees of adaptation to tethering. The experienced tethered sows were active stereotypers (HIGH sows) and the inexperienced tethered sows (T/LOW) were relatively inactive at the time of the experiment. The latter sows were released into a group (G/LOW) half-way through the experiment, for a comparison of tethered versus loose-housed sows.<p/>HIGH sows were about 3 times more active than T/LOW sows, due mostly to high stereotypy performance levels amongst the former sows. HIGH sows produced 35.7% more heat than the T/LOW sows during the 12 h light period of the day. During this period, 40.2% and 20.1% of heat production from HIGH and T/LOW sows was associated with activity. In comparison, G/LOW sows were slightly more active than T/LOW sows, with 23.5% of heat production being associated with activity.<p/>Stereotypy behaviour and excessive drinker manipulation by the HIGH, T/LOW and G/LOW sows accounted for 86, 52 and 24% of activity. The proportion of metabolizable energy intake required for these activities were 23, 7 and 4%, respectively, for sows in the 3 treatments. The results of the experiment indicate that tethering is stressful because of the need for sows to develop and perform large quantities of "coping behaviours% and the association with increased metabolic rate. It was also suggested that during the experiment, the T/LOW sows were following a path of adaptation to tether housing similar to that experienced earlier by the HIGH sows.<p/>Thus it is apparent that there is a positive association between welfare status and productivity of sows. Improvements in the welfare status of non-lactating sows will result in improved sow productivity. In the situation of the commercial environment, improvements to welfare status can only occur through improvements in the quality of the environment, for example by the removal of chronic stressors such as restraint.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Wiepkema, P.R., Promotor, External person
    • van Ree, J.M., Co-promotor, External person
    Award date14 Jun 1985
    Place of PublicationWageningen
    Publication statusPublished - 1985


    • sows
    • tethering
    • chains
    • animal behaviour

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