Brain opioid receptor density relates to stereotypies in chronically stressed pigs.

Opioid receptor densities were measured in the hippocampus of chronically stressed (tethered) pigs to study the involvement of endogenous opioid systems in stereotypy performance. Three groups of animals were housed tethered for 2 (n=12), 5.5 (n=12) and 8-9 months (n=8), respectively, and the intensity of stereotypy performance was determined. Opioid receptor densities were measured post mortem using membrane binding assays with [(3)H]naloxone as a ligand. A negative correlation was found between the density of opioid receptors and the intensity of stereotypy performance in the animals that had been housed tethered for 2 months. This correlation seemed to disappear with increasing duration of tethered housing. The data further suggest that, associated with the duration of tediered housing, there was a gradual decrease in the density of opioid receptors in the left hippocampal lobe of the low-stereotyping animals, but not in the right lobe, nor in the left and right lobes of the high-stereotypers. This suggests that chronic stress leads to a (asymmetrically expressed) progressive loss of opioid receptors in the hippocampus, and that stereotypies exert a mitigating effect on stress-induced changes in opioid receptor densities, supporting the hypothesis that stereotypies help the animals cope wife the adverse effects of chronic stress.

Endogenous opioids are involved in abnormal stereotyped behaviours of tethered sows.

Tethered sows continuously performed stereotypies during a substantial part of the day time. A single subcutaneous injection with naloxone significantly decreased the profound stereotypies, while explorative behaviours of pigs were not affected by naloxone. In addition a long-term effect of naloxone was noticed. It is suggested that performing the seemingly purposeless stereotypies may function as an effective strategy in order to cope with the conflict-inducing housing conditions. The present data implicate endorphins in this strategy. The involvement of endorphins in the stereotypies of the sows may be related to the calming, rewarding and dependency-inducing effects of the endorphins.

Effect of anterior hypothalamic and mammillary area lesions on territorial aggressive behaviour in male rats.

Adult male Wezob-rats were bilaterally lesioned in either the medial anterior hypothalamic area or the mammillary bodies. The behaviour of these animals when confronted with a male intruder within their own territory, was observed and recorded before and after lesioning and compared with the behaviour of sham-operated animals. Anterior hypothalamic lesions, including large parts of the anterior hypothalamus, the rostral part of the ventromedial hypothalamic nucleus and smaller caudal parts of the preoptic area, led to strong increases in defensive behaviour. This included a decreased tendency to investigate the intruder and an exaggerated defensive reaction when approached by the intruder. Ingestive behaviour and bodyweight were enhanced. Mammillary body lesions, including large parts of the ventral and dorsal premammillary nucleus, the caudal part of the arcuate nucleus, the medial mammillary nucleus, the posterior mammillary nucleus, the supramammillary peduncle and closely surrounding areas, led to a marked increase in offensive behaviour. This was characterized by high levels of initiatives and aggression towards an intruder. It is suggested that two distinct neural substrates exist in the medial hypothalamus, which normally modulate defensive (anterior medial hypothalamus) or offensive (posterior medial hypothalamus) aspects of intermale aggression.

Nembutal treatment of the VMH (rat): effects on feeding and sexual behaviour.

In male rats two brain cannulae were implanted bilaterally and directed to an area just dorsal of the ventromedial hypothalamic nucleus. The behaviour of these animals was observed before and after the injection through these cannulae of either 1 micronl saline or 1 micronl Nembutal. Injections were performed under three behavioural conditions: (1) animal alone in cage with food, (2) animal in the presence of an oestrous female and (3) animal in cage with food and oestrous female. Following the Nembutal injection, sniffing and feeding are disinhibited temporarily in condition 1, whereas in condition 3 only sniffing, but not feeding, is disinhibited. In conditions 2 and 3 male sexual behaviour is not influenced by the Nembutal except for an increase of sniffing at the female. It is concluded that a temporary elimination of the VMH leads to a disinhibition of feeding only if the external conditions are favourable for feeding. The same elimination of the VMH does not influence the occurrence of male sexual behaviour under the conditions used in these experiments.

Individual behavioral and physiological strategies in pigs.

Previous experiments demonstrated consistent individual behavioral differences in pigs. Some showed a more active behavioral response (so-called A/R pigs), others a more passive behavioral response (so-called NA/NR pigs). In the present study we selected 32 A/R and 32 NA/NR individuals and tested them individually in an open field at 3 (OF1) and 8 weeks of age (OF2). Individual response patterns were remarkably consistent between OF1 and OF2. While more A/R than NA/NR pigs made escape attempts, the A/R ones vocalized less, and were less inhibited to approach novel objects in OF1 and OF2, although they spent less time in exploring these objects than NA/NR pigs. Cortisol (CS) level after OF1 increased in A/R pigs but did not change in NA/NR ones, while CS level in OF2 remained constant in A/R pigs but decreased in NA/NR pigs. CS response to ACTH1-39 was measured at 3 and 8 weeks of age but did not differ between types. Basal CS level was higher in NA/NR than in A/R pigs and accompanied by adrenal hypertrophy. Mean heart rate (HR) was higher of A/R pigs compared to NA/NR ones in two backtests. HR of A/R pigs substantially increased (23.9 bpm = 15.5%) in reaction to the novel object in OF2, while HR of NA/NR ones only slightly increased (4.5 bpm = 2.9%), or even decreased (bradycardia). A/R pigs had more often heart deviations than NA/NR ones. The present study demonstrates that the two behavioral strategies of pigs are characterized by consistent differences in behavioral, physiological, and endocrine responses to conflict situations.

Brain opioid receptor density reflects behavioral and heart rate responses in pigs.

Results from our previous research indicate that long-term tether-housed pigs with high and low levels of stereotypies show differences in the density of endogenous opioid receptors in the hippocampus and hypothalamus. It was not clear whether differences in opioid receptor density were induced by the chronic stress of tether housing or stereotypy performance, or were already present before the animals were tethered. The latter possibility was tested in the present experiment. We used a group of 18 nonstereotyping pigs that had no experience with tether housing and investigated whether the animals differed in the density of endogenous opioid receptors in the brain and, if so, whether these differences were related to the animals' reactions to acute challenges. The pigs were subjected to two tests: an open field test and a tethering test. Behavioral reactions as well as heart rate responses were measured. Opioid receptor densities were determined postmortem in the hippocampus and hypothalamus using a membrane binding assay with [(3)H]naloxone as a ligand. Animals differed widely in their responses to the two tests. In support of our hypothesis, we found a relationship between behavioral and heart rate responses and densities of naloxone binding sites in the hippocampus and hypothalamus. The data suggest that endogenous opioid systems in the brain contribute to differences in stress responding between individual pigs.

Social rank and disease susceptibility in pigs.

Two experiments were carried out to investigate the inter-individual variation in immune reactivity and disease susceptibility of group housed pigs of different social status. The social status of the individual pig was determined by the outcome of social ranking fights and food competition tests. On Day 75 after the start of both experiments, all pigs were challenged with 0.5 ml of an Aujeszky disease virus (ADV) in each nostril. Data combined from both experiments showed that mortality and/or morbidity after the ADV challenge was highest among subordinates. In both experiments, a lymphocyte proliferation assay, using purified ADV as an antigenic stimulus, showed that dominant pigs had significantly higher counts per minute than subdominant and subordinate pigs. Kendall's partial correlations showed that morbidity had been associated with high values in haematological and clinicochemical blood parameters and not with social status of the individual pig. In each experiment, maternal derived antibodies against the ADV and the antibody level after the ADV challenge hardly differed between pigs of different social status. Major histocompatibility complex typing of class I and II by iso-electro focusing of all pigs in Experiment 2 showed that not all haplotypes were distributed equally among dominant, subdominant and subordinate pigs. The present work shows that there are large individual differences in immune reactivity and disease susceptibility which appear to be related to the social status of the individual pig in a stable social structure.

Coping styles of tethered sows.

Behaviour of 20 non-pregnant primiparous sows was observed from the moment of first tethering till 2 hours thereafter, and after being tethered for 1 and 2 months. After 2 months of tethering the sows could be divided into 2 distinct groups; (1) high stereotypers and (2) low stereotypers. Sows that resisted most at first tethering showed the lowest level of stereotyping after 1 and 2 months of tethering. High resisting sows may experience the uncontrollability of first tethering most drastically and develop a state of helplessness. Low resisting sows may accept tethering easier and adapt by means of developing stereotypies. Low stereotyping sows were more alert after 1 and 2 months of tethering than high stereotyping ones. Heart rate measurements showed that high stereotyping sows had lower mean heart-rates after feeding (when stereotyping is most pronounced) than low stereotyping ones. This difference was already present before tethering when the sows were loose-housed. The results show differences in styles of coping in sows that become more visible during tethering.

Proceptive and receptive aspects of oestrus behaviour in gilts.

Proceptive and receptive aspects of behaviour were studied during the oestrus cycle of the female pig. These aspects were studied in a T-maze with one or two stimulus compartments that did or did not contain a teaser boar. Receptive behaviour was observed during several consecutive days and was quantified in front of the boar by using the back pressure test (BPT). Three aspects of proceptive behaviour, i.e. the tendency to 'search the boar', 'stay close to the boar' and 'to present' in front of the boar peaked in the middle of the receptive period, and in most gilts on the day preceding the last receptive day (Experiment 1). In contrast, preference for a particular boar, another aspects of proceptive behaviour, was only expressed during the days preceding and following the receptive period (Experiment 2). The results are discussed in terms of the possible functional implications of proceptive and receptive behaviour in relation to fertilization.

Oiling behaviour and the effect of lipids on dustbathing behaviour in laying hens Gallus gallus domesticus.

Laying hens oiled the plumage twice a day, while oiling behaviour consisted of a bout of five oilings (median value). During one oiling, a hen collected lipids from the preen gland with her bill and subsequently performed (as a median) five strokes or rubs over and through the feathers. The breast was oiled most, whereas during later oilings within an oiling bout the wings and the flanks were oiled as well. The back and the tail were seldom oiled. An artificial distribution of stale uropygial gland lipids in a more or less natural way on the breast feathers within a 3-day period of sand deprivation resulted in an increase of the duration of the first dustbath after the deprivation by 12%, compared with a control treatment. Within the dustbath, the total number of the side-lying and side-rubbing elements - two related consummatory dustbathing elements - doubled and tripled, respectively. In contrast to these highly significant effects, the duration of the dustbathing did not change after a fresh uropygial gland lipid treatment, while the effects on side-rubbing and side-lying were not straightforward; the total number of the side-rubbing element was doubled, but the duration of side-lying was reduced by 29%. The results are discussed in relation to the chosen methodology and the maintenance of the lipid condition of the integument.

Food intake and body measurements of Atlantic bottlenose dolphins (Tursiops truncates) in captivity.

The food consumption (recorded in kg of individual fish species), body length and mass of 11 Atlantic bottlenose dolphins kept first at Windsor Safari Park, UK (1979-1993/1994), and later at Harderwijk Marine Mammal Park, The Netherlands (1993/1994-1995) are reported. This broad-scale, longitudinal study is based on historical data that were originally recorded for short-term husbandry purposes. The chemical composition and caloric value of the diet were variable and were not recorded. The food intake quantities should therefore be viewed as rough weight estimates of what wild conspecifics might eat (depending on their diet). The average annual food consumption of adult males and non-pregnant, non-lactating females was approximately 2000 kg of fish (estimated at 176 x 10(5) kJ). Food consumption showed little increase during gestation, but was 58-97% higher during lactation than during similar periods in non-reproductive years. All six calves began to eat solid food within a year of birth although suckling continued for 14-37 months after birth. The pattern of food intake of mothers and calves varied substantially between suckling periods. No seasonal changes in food consumption were detected, although there were small seasonal changes in water temperature. Births occurred at various times of year, since the timing of mating varied between years. The animals' body length increased rapidly during the first 3 years of life after which the growth rate decreased. Body length reached asymptote at approximately 270 cm. Adults of both sexes weighed around 260 kg. The relationship between standard body length (in cm) and body mass (in kg), although based on a small sample size (n = 16), can be expressed as body mass = 17.261e(0.0156(body length-100)). Animals weighing 155-225 kg consumed between 2 and 4% of their body mass per day.

Developmental aspects of motivated behavior in domestic animals.

Biological functions like health, reproduction or the performance of specific behavior programs change over time. Therefore, their actual significance can only be understood fully if their history or development is well known. This point is illustrated with respect to behavior patterns in farm animals. Early life or ontogenetic processes strongly determine (sub)adult behavior. Prepuce suckling performed by group-housed veal calves during the age of 2 to 8 wk depends on sucking experience of the same calves during their first week of life. Restless behavior of fattening pigs is largely determined by rearing conditions in the first weeks of life. Disturbed behaviors like stereotypies develop out of conflict behaviors (biting, escape, etc.), as is the case in tethered sows. These stereotypies appear to promote the release of endorphins. In veal calves, different stereotypies (biting or licking the crate and tongue playing) develop during different periods of time and probably are related to different sorts of conflicts experienced by the developing calf. Tongue playing shows a specific relationship with abomasal ulcers. In veal calves, individual coping differences are observed that strongly parallel those described in other vertebrates (rats, dogs, men).

Handling and diet-induced atherosclerosis in rabbits.

Atherosclerosis was induced in rabbits by feeding them a 2% cholesterol diet (CHOL) during a 5-week period. Twelve rabbits were fed with increasing amounts of CHOL food until the ad libitum level was reached, whereas in 24 other rabbits the food was limited to the amount eaten by the lowest consumer of the group to reduce individual variability in total amount of food consumed. Twice a day, half of the rabbits were handled carefully, the other half had normal laboratory practice contact with their caretaker. Feed intake and amount of atherosclerosis were determined for all experimental animals, while for the handled animals behavioural parameters and changes were recorded daily and per animal. On average the handled and non-handled rabbits took the same amount of food per week, although there were large individual differences. The handled animals showed some behavioural adaptation to being handled. Handling had no influence on atherosclerosis size; this latter measure was only roughly determined by the amount of CHOL food eaten.

Studies of feather pecking in poultry.

Feather pecking and cannibalism are obviously detrimental to birds' welfare. Moreover, the introduction of alternatives to battery cage housing of laying hens is seriously hampered by these behaviours. Our experimental work reviewed here supports the hypothesis that feather pecking evolves as redirected ground pecking. Thus the main practical strategy to prevent feather pecking and cannibalism is to provide an adequate substrate throughout life, from the start of the rearing period onwards. However, no strategy guarantees that feather pecking will not develop in practical poultry husbandry and beak trimming may be required in specific cases to prevent the risk of greater welfare problems caused by cannibalism. Studies in birds showing different propensities for feather pecking may lead to a better understanding of the processes underlying feather pecking as well as providing simple procedures to select strains of birds in which the incidence of feather pecking and cannibalism is low.

[Stress in our farm animals]. / Overbelasting van ons vee.

Individual vertebrates are characterised by the flexible way they cope with stressors: mammals and birds provide good examples of coping behaviour. When stressed and an adequate solution is not available, vertebrates experience a state of uncertainty. Stress symptoms occur under conditions of lowered predictability and/or controllability of the environmental situation. Neuroendocrine changes associated with stress may reduce the immune and reproductive capability. Although the performance of disturbed behaviour has adaptive value, it simultaneously demonstrates an overtaxed and unhealthy state. Individual vertebrates appear to cope with stressors in a predominantly sympathetic or parasympathetic way. The severity of the stress experienced by an individual is also determined by the quality of its social contacts with conspecifics and men.

[Behaviour and well-being (author's transl)]. / Gedrag en welzijn.

The question how problems of behaviour and well-being of (farm) animals can be studied by ethological methods is central in the present paper. An ethologist uses basic concepts such as behaviour element, behaviour system and 'Umwelt' of an animal; these concepts are described. The normal course of all sorts of processes of behaviour can be readily accounted for by regulating systems. These regulating systems are directed towards homeostasis of several environmental aspects of the organism. Regulation of these aspects is based on criteria which may be regarded as genetic and ontogenetic memory images or those resulting from experience. Well-being may be defined as conformity of environmental characteristics and accompanying criteria. However, not all criteria are of equal biological importance. This model concept renders it plausible that animals also have some awareness of their environment and must experience sensations while functioning. The present paper concludes with a discussion of these points.

[Limits of biotechnology]. / Grenzen in de biotechnologie.

Biological manipulation of reproduction and growth in farm animals may easily lead to gross underestimation of biological characteristics of these vertebrates. When possible damage to these animals is assessed four peculiarities of vertebrates are of considerable interest. Vertebrates are characterised by being (1) cognitive individuals which show typical symptoms of stress when they become uncertain and insecure, (2) adapted to a species-specific niche, the essential parts of which should be recognised and used in actual husbandry systems of farm animals, (3) dependent on intensive contacts with their fellows or, in the case of farm animals, with men and (4) adults which are the final stage of a species-specific and undisturbed development. Biotechnology should not interfere with these aspects. Although biotechnology is an ethically neutral activity, it should not be permitted for every purpose and at any cost.

[Behavioral disorders in animals of stock farms]. / Over gedragsstoringen bij dieren in de veehouderij.

Intensively kept farm animals often show behavioural disturbances; some of these disturbances will cause pain (injurious behaviour), others will reflect pain (limping, colic). Also, the very common stereotypies are associated with pain. These stereotypies are characterized by their constant form and senseless repetitions. Stereotypies of tethered sows would appear to be specifically related with endorphins; they may act as agents promoting the release of endorphins and thereby calming the animal. This tranquilizing and protective function of stereotypies may play a role in veal calves showing abomasal injury. It was found that those calves that displayed most stereotypies had the least abomasal damage. Finally, a model is described, which makes it clear why emotions are essential in the behaviour of man and animals.

[Current possibilities of improving health and welfare status of pigs through introduction of the specific 'Stress Free' (SSF) System]. / Nieuwe mogelijkheden tot het verhogen van de gezondheids- en welzijnsstatus van varkens door introductie van het 'Specific Stress Free' (SSF)-systeem.

Health and welfare problems of pigs in intensive husbandry systems are mainly caused by housing and management of the animals. The actual structure of these systems also gives rise to health and welfare problems. Solving these problems is very difficult to achieve in the existing systems. It will be necessary to create new structures and housing systems from a preventive veterinary point of view to avoid harm to health and welfare caused by specific stressors. Specific stressors which can be prevented are associated with the risk of infection, mixing and replacing animals, high density, inadequate house climate, handling of animals and the farmer's attitude towards his animals. The SSF-system specifies the method by which these specific stressors are prevented.

[Mucosal lesions in the pars esophagus in swine: prevalence and the effect of stress]. / Slijmvliesveranderingen in de pars oesophagea bij varkens: prevalentie en de invloed van stress.

Morphological investigations of slaughterhouse material revealed a prevalence of 63% of the sows (n = 224) and 36% of the slaughter pigs (n = 209) with mucosal lesions in the pars oesophagea. The mucosal lesions were composed of severe hyperkeratosis, erosions or ulceration. Microscopic examination showed that hyperkeratosis is attended with parakeratosis. From experiments in a climate controlled pighouse it could be concluded that mixing of unfamiliar pigs resulted in higher prevalences of gastric lesions as compared with keeping the litter together until the end of the experiment (farrow to finish system). There was no relation between gastric lesions and climatic stressors or between gastric lesions and growth and sex of the pigs. When pigs, according to social ranking, were divided in high, middle and low rank it showed that more pigs in the middle-ranked group had gastric lesions. The serum pepsinogen was not related with gastric lesions. There was a tendency that plasma cortisol increased with severity of gastric lesions. There was a strong significant 'litter-effect', which can indicate a genetic predisposition for the development of gastric lesions. Maybe that the presence of mucosal lesions in the pars oesophagea can be used as an objective indicator for welfare in intensive pig husbandry.