Jeff Rushen

Stereotypies, aggression and the feeding schedules of tethered sows

Thirty tethered sows were observed for 5 min every half-hour for 9 h spanning the two feeding periods. Activity, consisting largely of food searching behaviour and drinking, was largely restricted to two 2-h periods following each feed. Three categories of stereotyped behaviour were observed and these were closely tied to the feeding periods. Short-duration bouts of rubbing, head-waving and bar-biting occurred during food delivery, while long-duration bouts of highly stereotyped and idiosyncratic sequences of rubbing and drinking were shown by older sows immediately after feeding. Vaccuum chewing tended to occur slightly later. I suggest that frustration of feeding motivation rather than under-stimulation underlies stereotypies in pigs, and that the different forms may represent stereotype of the appetitive and consummatory phases. Aggression was rare and was not closely related to the feeding periods or to stereotypies.

Stereotyped behaviour, adjunctive drinking and the feeding periods of tethered sows

The behaviour of 25 tethered sows in an intensive piggery was observed for 1 h before and 1 h after the delivery of food to determine if behavioural stereotypies appeared as adjunctive behaviours. The different components of behavioural stereotypies were found to have different associations with the feeding period. Head-waving, bar-biting, and rubbing the snout against the cage were most common before feeding, and were shown particularly by the older sows. Manipulating the drinker and, for some sows, rubbing were most common after. There was some evidence of polydipsia. Vacuum chewing, playing with the chain, and aggressive behaviours, however, did not appear to be associated with the feeding period. The last two behaviours occurred only rarely. Seven sows showed stereotyped sequences of rapid rubbing or rapid drinking after the delivery of food, and these sows showed more excitement before food was delivered. Rooting was common for the full hour after all food had been consumed, and occurred in conjunction with long duration drinking. I suggest that the occurrence of adjunctive drinking by sows results from the persistence of feeding motivation, perhaps because concentrated food does not provide sufficient stomach distension, combined with the knowledge that food will definitely not be forthcoming. Stereotyped sequences of behaviour may be a means of reducing the arousal generated by the expectation of food.

The peck orders of chickens: How do they develop and why are they linear?

The development of peck orders in mixed sex groups of domestic chickens was observed to determine how linearity occurred. Based on threats, head-pecks and submission, dominance relationships emerged in a virtual peck right form. Leaping by males, however, did not closely conform to dominance relationships. There were no rank reversals in 50% of male-male and 80% of female-female relationships, and only single changes occurred in most of the others. These resulted from the movements of individuals up the hierarchy rather than from any general reorganization of relationships. Reversals did not necessarily occur between rank neighbours, and stable triangles were sometimes introduced. The initial status of males and females depended upon the age at which they first showed aggression, while the final, stable status of males depended upon the age at which they were first submitted to. Sexual maturity of the males produced a number of changes, with earlier-maturing birds tending to rise in status above their later-maturing companions. Linear hierarchies therefore appear to result from birds developing at different rates.

Relationship between plasma cortisol and stereotypic activities in pigs.

The relationship between the performance of post-feeding stereotypic behaviour and plasma cortisol levels and the effect of prevention of stereotypic behaviour on plasma cortisol levels were studied in chronically restrained sows. In experiment 1 sows classified as high or low stereotypers on the basis of time spent manipulating chain and behaviour directed to the nipple drinker were found not to differ in plasma cortisol levels. Removing the chain and nipple drinkers also did not affect cortisol concentrations of either group. In experiment 2 detailed recordings were made by an automatic logging system of two major categories of stereotypy; chain manipulation and drinking. There were large individual differences in levels of both chain manipulation and drinking. Both activities showed a similar diurnal pattern, but average levels across individuals were not correlated. Both activities showed a continuous distribution across individuals and therefore a correlational rather than factorial analysis was used. Chain manipulation was not correlated to cortisol concentrations on any of the control days and removing the chain for one day (experiment 2A) or for seven days (experiment 2B) was also not accompanied by increased cortisol levels. However individuals showed a consistent cortisol response to chain removal as indicated by correlations between treatment days. Drinking showed a tendency to be negatively correlated to cortisol concentrations on control days. Long-term chain removal was accompanied by an increase in average drinking that showed a non-significant tendency to be negatively correlated to plasma cortisol on treatment days and thus may explain part of the consistency of response to chain removal. The lack of correlation between chain manipulation and plasma cortisol suggests that this activity does not serve to reduce plasma cortisol in chronically restrained sows. The relationship between drinking and cortisol need not necessarily reflect the coping capacity of this behaviour but may be a physiological consequence of the large amounts of water ingested.

How peck orders of chickens are measured: A critical review

The peck orders of chickens have been measured in many ways, and the question of which measure is most appropriate arises. This can only be answered in reference to the way that the measure is to be used. Staging paired contests between unacquainted birds is best used to assess the stable, intrinsic traits that underly dominance relationships. However, this method does not give reliable estimates of the relationships the birds form when grouped. The social environment of each bird is best assessed by observing the agonistic encounters that occur. However, the comparability of the different forms of aggressive behaviour needs to be established. Measures based upon priority of access to food cannot be used with confidence. Measures of rank need to be normally distributed and reflect the actual magnitude of the difference between birds only when these are to be used in assessing the underlying traits.

The development of sexual relationships in the domestic chicken

Mixed sex groups of chickens were observed from hatching until 25 weeks of age, to determine the behavioural factors responsible for the association between status and mating activity, and to describe the development of sexual relationships. Factor analysis showed no association between sexual activity and the status of either cocks or hens, perhaps because these were young birds. A high frequency of treading occurred in social relationships where the male chased the female frequently, or where the male waltzed to the female frequently. Treadings most often resulted from crouchings by the females, chasing the female, and previous treadings by other males. Sexual preferences between particular pairs of individuals were noted, but this was not due to dissortive mating with regard to status. Throughout development, aggressive behaviour was more frequent between individuals of the same sex, but there was a marked distinction between inter- and intrasex aggression.

Frequencies of agonistic behaviours as measures of aggression in chickens: A factor analysis

Different types of aggressive behaviour have often been treated as comparable in measures of aggressiveness in chickens. Are these different forms of behaviour equivalent? Observations were made of behaviour in small mixed-sex groups of domestic chickens, from hatcing to 25 weeks of age. Threats and headpecks both tended to elicit avoidances, and retaliation was rare. However, leaps and horizontal threats tended to elicit other leaps. Factor analysis showed that threats and pecks tended to occur in the same dyadic relationships. Dyads with a high frequency of chases and waltzes, however, were not necessarity those with a high frequency of threats and pecks. The frequency of waltzing was dependent on the amount of crowing a male showed. The frequency of leaps and horizontal threats tended to be closely linked to the occurrence of running bouts rather than to the occurrence of threats and pecks.

Development of social behaviour in chickens: A factor analysis

Factor analysis was used to describe the week by week changes in the frequency of a wide range of behaviours of chickens. Oblique rotation resulting in correlated factors was compared with the more conventional orthogonal rotation, and was found to provide a clearer interpretation of the factors. Mixed sex groups of chickens were observed from hatching until sexual maturity, and the changes in the occurrence of agonistic behaviours could be described in terms of three factors. Factor 1 involved early sparring and running, but there was some doubt as to whether this should be labelled aggressive. Factor 2 involved non-reciprocated leaping, horizontal neck threats, and headpecks between males. Factor 3 involved threats and headpecks between males and females. Sexual development could be described by two factors; the first involving sexual development of the male, and the second the beginning of sexual interactions between males and females. Waltzes and rear approaches were associated with the sexual development of males, while chases were associated with sexual interactions. There was an increase in the frequency of prolonged male-male agonistic encounters when these sexual interactions began to occur.