Behaviour of groups of weaner pigs in three different housing systems

88 show this response as there were no trees in this habitat. In contrast to the inland habitat, no fresh water was available on the marsh. The consequent allocation o f substantial time to grazing by the marsh animals may be an attempt to compensate for water losses produced by constant exposure to the sun. Grazing on semi-succulent plants (such as Sueda spp. and Salicornia spp.) may help replace water losses. The results provide an indication that ponies modify their behaviour when living on the marsh, but a much more extensive analysis is required to assess the relevance o f the changes. Behavioural scientists formerly tended to assume that particular species were characterised by typical and rather immutable social orgauisations. The present findings confirm that feral ponies (as has been demonstrated recently in many other organisms such as primates and rodents), obviously adapt to circumstances and situations by modifying their behaviour. This rather basic point has relevance to questions o f appropriate rearing conditions for many domestic species.

BEHAVIOUR OF GROUPS OF WEANER PIGS IN THREE DIFFERENT HOUSING SYSTEMS

A.J. M c K I N N O N

1, S . A . EDWARDS 2 and D.B. STEPHENS 3

1Ministry of Agriculture and Fisheries, Private Bag, Auckland (New Zealand) Terrington Experimental Husbandry Farm, King's Lynn, Norfolk (G t. Britain) 3AFRC Institute of Animal Physiology, Babraham, Cambridge (Gt. Britain)

ABSTRACT The behaviourai changes induced by modern intensive husbandry methods may form a reliable basis for assessing the welfare o f the animals kept under such conditions. This study compared the behaviour o f groups o f pigs housed in different types o f post-weaning accommodation. Large White × Landrace pigs were weaned at 3 weeks o f age and housed in groups of 13 in a controlled-environment weaner house. Each room in the weaner house contained 8 pens (2.5 × 1.2 m) with pigs of similar age. The rooms contained either conventional flat-deck pens, with fully perforated floors o f wire mesh, or kennelled pens with an insulated concrete floor in the rear two-thirds which was covered by a kennel lid and plastic front curtain. The open portion of these pens had a wire-mesh floor. By placing a retaining board 13 cm high at the kennel entrance, chopped straw could be held in the lying area. Two pens o f 13 pigs aged 5--6 weeks were observed in each o f the following conditions: (1) fully perforated floor, no straw; (2) part solid floor, no straw; (3) part solid floor, 0.5 kg per pen per day chopped straw. Each pen was observed for three sessions of 3 h covering the period 07.30--16.30 h when lighting would normally he on. Pigs were individually marked and their behaviour was recorded at 4-rain intervals. With standardised light and temperature regimes and ad libitum feeding, synchronisation of activity between pens in the same room was not observed. High ambient temperatures affected the behaviour observed, with wallowing on the solid floors tending to minimise the effects of straw. Pigs housed on fully perforated floors were less active than those on part solid floors, while those given chopped straw showed highest activity levels (22 v. 27 v. 33% o f observations, P < 0.001). The proportion of behaviour classified as abnormal was much higher on fully perforated floors than on the concrete floors, either without or with straw (25.5 v. 1 1 . 5 v. 11.0% o f active behaviour, P < 0.001). Belly-nosing

89 was the most c o m m o n f o r m of abnormal behaviour in all three conditions (46, 43 and 48% o f total a b n o r m a l behaviour o n wire mesh, part solid and with straw, respectively). Pen-chewing was m o s t c o m m o n in t h e straw t r e a t m e n t (20 v. 20 v. 43% of abnormal behaviour, P < 0.01), which also had the lowest incidence o f chewing pen-mates (21 v. 30 v. 7% of a b n o r m a l behaviour, P < 0.01). These results indicated that the behaviour o f groups o f pigs was influenced by their housing, with part solid floors and straw provision giving best results.

VICES IN STABLED CRIB--BITING

HORSES

WITH SPECIAL

REFERENCE

TO

M.B.H. S C H I L D E R

Laboratory of Comparative Physiology, State University of Utrecht, Utrecht (The Netherlands)

ABSTRACT F o r horses, the stable constitutes an e n v i r o n m e n t quite different f r o m its normal situation. As t i m e spent on feeding and l o c o m o t i o n is greatly reduced c o m p a r e d to horses on the range (60 and 9%, respectively, c o m p a r e d to Camargue horses (Duncan, 1979)), behavioural p r o b l e m s related to the underactivity o f these behavioural systems m a y arise. A third source o f possible p r o b l e m s for stabled horses lies in the limitations for social contacts with conspecifics. In t h e literature, lack o f e n v i r o n m e n t a l stimulation, stress related to intensive training and s o m e t i m e s crowding are suggested as causes o f vices. As practically no quantitative data on vices have been published, it remains difficult to assess the merits o f these and o t h e r suggestions. The p e r f o r m a n c e o f a vice is o f t e n damaging to the horse and a nuisance to the owner, and m a y be a sign that the horse's welfare is affected. Therefore, a quantitative study on the o n t o g e n y of vices, especially cribbiting, has been started. A horse is said to crib-bite w h e n it grabs the manger or s o m e related part of t h e e n v i r o n m e n t in its m o u t h , arches its neck and sucks wind. The following m o d e l serves as a starting point in this research. Assuming that the regulation o f behaviour is organised in a hierarchial manner, it is hypothesized that, in a stable, the environm e n t a l stimulation is inadequate to keep behavioural systems o f high a u t h o r i t y activated. These systems are supposed to c o n t r o l systems lower in the hierarchy. So, sub-systems lower in the hierarchy, which regulate parts of larger behavioural complexes, m a y escape the inhibiting influence o f systems with a higher authority. F o r example, the t e n d e n c y to grab s o m e t h i n g with the m o u t h , which is a part o f the normal feeding repertoire, m a y be disinhibited in a stabled horse deprived of adequate stimulation. Then, by postural and c o n t e x t u a l facilitation, the horse m a y grab the manger. This grabbing m a y be considered as a precursor o f crib-biting. Grabbing m a y be reinforced w h e n the horse eats f o o d i m m e d i a t e l y afterwards. Moreover, the care-taker m a y play a part in the c o n d i t i o n i n g o f the grabbing b y providing f o o d or attention, thus reinforcing the behaviour. When cribbiting has thus b e c o m e a fixation, further r e i n f o r c e m e n t m a y result f r o m the p r o d u c t i o n of endorphines. E n d o r p h i n e s are t h o u g h t to reduce the awareness o f unpleasant situations. It is n o t yet u n d e r s t o o d h o w the sucking o f wind b e c o m e s part o f t h e vice. There m a y be three possibilities: (1) the sucking m o v e m e n t s m a y o c c u r accidentally during the grabbing o f the manger and m a y be rewarded in a similar fashion as described above; (2) the air incidentally swallowed partially fills t h e stomach, which is rewarding because the