Comparing interspecific socio-communicative skills of socialized juvenile dogs and miniature pigs.

Previous research proves dogs' outstanding success in socio-communicative interactions with humans; however, little is known about other domestic species' interspecific skills when kept as companion animals. Our aim was to assess highly socialized young miniature pigs' spontaneous reactions in interactions with humans in direct comparison with that of young family dogs. All subjects experienced similar amount of socialization in human families. In Study 1, we investigated the appearance of human-oriented behaviours without the presence of food (Control condition) when a previously provided food reward was withheld (Food condition). In Study 2, we measured responsiveness to two types of the distal pointing gesture (dynamic sustained and momentary) in a two-way object choice test. In the Control condition of Study 1, the duration of pigs' and dogs' orientation towards and their frequency of touching the human's body was similar. In the Food condition, these behaviours and orienting to the human's face were intensified in both species. However, pigs exhibited face-orientation to an overall lesser extent and almost exclusively in the Food condition. In Study 2, only dogs relied spontaneously on the distal dynamic-sustained pointing gesture, while all pigs developed side bias. The results suggest that individual familiarization to a human environment enables the spontaneous appearance of similar socio-communicative behaviours in dogs and pigs, however, species predispositions might cause differences in the display of specific signals as well as in the success of spontaneously responding to certain types of the human pointing gestures.

Behavioral phenotyping of minipigs transgenic for the Huntington gene.

BACKGROUND: While several novel therapeutic approaches for HD are in development, resources to conduct clinical trials are limited. Large animal models have been proposed to improve assessment of safety, tolerability and especially to increase translational reliability of efficacy signals obtained in preclinical studies. They may thus help to select candidates for translation to human studies. We here introduce a battery of novel tests designed to assess the motor, cognitive and behavioral phenotype of a transgenic (tg) HD minipig model. NEW METHODS: A group of tgHD and wildtype (wt) Libechov minipigs (n=36) was available for assessment with (1) a gait test using the GAITRite(®) automated acquisition system, (2) a hurdle-test, (3) a tongue coordination test, (4) a color discrimination test, (5) a startbox back and forth test and (6) a dominance test. Performance of all tests and definition of measures obtained is presented. RESULTS: Minipigs were able to learn performance of all tests. All tests were safe, well tolerated and feasible. Exploratory between group comparisons showed no differences between groups of tgHD and wt minipigs assessed, but low variability within and between groups. COMPARISON WITH EXISTING METHOD(S): So far there are no established or validated assessments to test minipigs in the domains described. CONCLUSIONS: The data shows that the tests presented are safe, well tolerated and all measures defined can be assessed. Prospective longitudinal application of these tests is warranted to determine their test-retest reliability, sensitivity and validity in assessing motor, cognitive and behavioral features of tg and wt minipigs.

The stress response and exploratory behaviour in Yucatan minipigs (Sus scrofa): Relations to sex and social rank.

According to the coping styles hypothesis, an individual demonstrates an integrated behavioural and physiological response to environmental challenge that is consistent over time and across situations. Individual consistency in behavioural responses to challenge has been documented across the animal kingdom. Comparatively few studies, however, have examined inter-individual variation in the physiological response, namely glucocorticoid and catecholamine levels, the stress hormones secreted by the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, respectively. Variation in coping styles between individuals may be explained in part by differences in social rank and sex. Using 20 Yucatan minipigs (Sus scrofa) we: (1) investigated the existence of consistent inter-individual variation in exploratory behaviour and the hormonal stress response, and tested for correlations as predicted by the coping styles hypothesis; and (2) evaluated whether inter-individual behavioural and hormonal variation is related to social rank and sex. Salivary stress biomarkers (cortisol, alpha-amylase, chromogranin A) were assessed in the presence and absence of a stressor consisting of social isolation in a crate for 10 min. Principal components analysis on a set of behavioural variables revealed two traits, which we labelled exploratory tendency and neophobia. Neither exploratory tendency nor neophobia predicted the physiological stress response. Subordinate pigs exhibited higher catecholamine levels compared to dominant conspecifics. We observed sex differences in the repeatability of salivary stress markers and reactivity of the stress systems. The results do not provide support for the existence of behavioural-physiological coping styles in pigs. Sex is an important determinant of the physiological stress response and warrants consideration in research addressing behavioural and hormonal variation.

Successive and conditional discrimination learning in pigs.

We studied the ability of pigs to discriminate tone cues using successive and conditional discrimination tasks. Pigs (n = 8) were trained in a successive discrimination Go/No-Go task (Experiment 1) to associate a Go-cue with a reward at the end of a runway and a No-Go-cue with the absence of reward. Latency to reach the goal-box was recorded for each cue-type. Learning of a conditional discrimination task was compared between low-birthweight (LBW, n = 5) and normal-birthweight (NBW, n = 6) pigs (Experiment 2) and between conventional farm (n = 7) and Göttingen miniature (n = 8) pigs (Experiment 3). In this active-choice task, one cue signalled a response in a right goal-box was correct and a second cue signalled a response in a left goal-box was correct. Cues were differentially rewarded. The number of sessions to learn the discrimination and number of correct choices per cue-type were recorded. In Experiment 1, four out of eight pigs showed learning on the task, that is, a higher latency to respond to the No-Go-cue, within 25 sessions. In Experiment 2, eight out of 11 pigs learned the discrimination within 46 sessions. LBW learners learned faster than NBW learners. In Experiment 3, all 15 pigs learned the task within 16 sessions. Göttingen miniature pigs learned faster than conventional farm pigs. While some methodological issues may improve the Go/No-Go design, it is suggested that an active-choice task yields clearer and more consistent results than one relying on latency alone.

Performance of conventional pigs and Göttingen miniature pigs in a spatial holeboard task: effects of the putative muscarinic cognition impairer Biperiden.

BACKGROUND: The pig is emerging as a model species that bridges the gap between rodents and humans in research. In particular, the miniature pig (referred to hereafter as the minipig) is increasingly being used as non-rodent species in pharmacological and toxicological studies. However, there is as yet a lack of validated behavioral tests for pigs, although there is evidence that the spatial holeboard task can be used to assess the working and reference memory of pigs. In the present study, we compared the learning performance of commercial pigs and Göttingen minipigs in a holeboard task. METHODS: Biperiden, a muscarinic M1 receptor blocker, is used to induce impairments in cognitive function in animal research. The two groups of pigs were treated orally with increasing doses of biperiden (0.05 - 20 mg.kg-1) after they had reached asymptotic performance in the holeboard task. RESULTS: Both the conventional pigs and the Göttingen minipigs learned the holeboard task, reaching nearly errorless asymptotic working and reference memory performance within approximately 100 acquisition trials. Biperiden treatment affected reference, but not working, memory, increasing trial duration and the latency to first hole visit at doses ≥ 5 mg.kg-1. CONCLUSION: Both pig breeds learned the holeboard task and had a comparable performance. Biperiden had only a minor effect on holeboard performance overall, and mainly on reference memory performance. The effectiveness needs to be evaluated further before definitive conclusions can be drawn about the ability of this potential cognition impairer in pigs.

The effect of the inter-phase delay interval in the spontaneous object recognition test for pigs.

In the neuroscience community interest for using the pig is growing. Several disease models have been developed creating a need for validation of behavioural paradigms in these animals. Here, we report the effect of different inter-phase delay intervals on the performance of Göttingen minipigs in the spontaneous object recognition test. The test consisted of a sample and a test phase. First, the pigs explored two similar objects. After a 10-min, 1-h, or 24-h delay two different objects were presented; one familiar from the sample phase and one novel. An exploration-time difference between the novel and the familiar object was interpreted as recognition of the familiar object. We scored the exploration times both manually and automatically, and compared the methods. A strong discrimination between novel and familiar objects after a 10-min inter-phase delay interval and no discrimination after 24h were found in our set-up of the spontaneous object recognition test. After a 1-h delay, the pigs still showed a significant habituation to the familiar object, but no discrimination was observed. Discrimination between the two objects was mainly confined to the first half of the test phase, and we observed a high between-subject variation. Furthermore, automatic tracking was valid for determination of habituation and discrimination parameters but lead to an overestimation of individual measurements. We conclude that the spontaneous object recognition test for pigs is sensitive to increasing inter-phase delay intervals, and that automatic data acquisition can be applied.

Human-directed aggression in miniature pet pigs.

OBJECTIVES: To determine whether associations exist between human-directed aggression and sex, neutering status, age of weaning, the presence of other pet pigs, or the presence of environmental enrichment objects in miniature pet pigs. DESIGN: Internet survey. STUDY POPULATION: Responses from 222 owners of miniature pet pigs. PROCEDURES: Pet pig owners were requested to complete a 48-item multiple-choice and short-answer Internet survey for each pig that they presently owned. RESULTS: Among 222 surveys that met enrollment criteria, human-directed aggression that occurred on at least 1 occasion was reported in 64% (n = 142) and aggression that occurred once or more per month was reported in 31% (69). No significant differences were found in the prevalence of human-directed aggression among castrated males, sexually intact females, and spayed females. Ages of weaning and neutering and the presence of objects intended to serve as environmental enrichment were not associated with frequency of aggression. A significant inverse association was detected between presence of other pigs in the same household and human-directed aggression, such that 21% (20/95) of pigs that lived with at least 1 conspecific were aggressive on a frequent basis, compared with 39% (49/126) of pigs that lived with no conspecific. A similar inverse association was evident regarding aggression that occurred on at least 1 occasion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that human-directed aggression is a common problem in miniature pet pigs. The presence of a conspecific can be expected to reduce the likelihood of human-directed aggression.

Survey of humane organizations and slaughter plants regarding experiences with Vietnamese potbellied pigs.

OBJECTIVE: To determine to what extent humane organizations are receiving requests to take unwanted Vietnamese potbellied pigs and to determine whether owners of potbellied pigs are selling them for slaughter. DESIGN: Mail survey. SAMPLE POPULATION: 1,178 humane organizations in 7 states and 978 slaughter plants in 4 states. RESULTS: 802 (68%) humane organizations and 787 (81%) slaughter plants responded. Of the humane organizations that responded, 479 (60%) stated they were willing to accept potbellied pigs. Humane organizations received 4,380 requests from owners to accept potbellied pigs during the study period and accepted 3,149 (72%) of these pigs. Six hundred fifteen (20%) of the potbellied pigs accepted were strays. Of the 437 humane organizations that provided reasons why owners relinquished their potbellied pigs, 255 (58%) reported larger than expected size, 148 (34%) reported zoning restrictions and 82 (19%) reported aggression. Of 485 slaughter plants that normally slaughtered hogs, 255 (53%) had received requests to slaughter potbellied pigs. These plants slaughtered 2,640 and refused 1,407 potbellied pigs during the study period. CLINICAL IMPLICATIONS: Problems with larger than expected size, zoning restrictions, and aggressive behavior caused owners of Vietnamese potbellied pigs to relinquish their pets to humane organizations and slaughter plants.

Behavior problems of pet pigs.

Pigs of all kinds can be enjoyable, charming pets, but the reduced size of the Vietnamese potbellied pig makes it an excellent choice for a porcine pet. Their curious, almost childlike behavior, as well as their adaptability and ease of learning, can make them a real pleasure and a great challenge to keep. The author fears that as many as 25% to 50% of potbellied pigs are no longer in their original homes by 1 year of age primarily because of a high incidence of behavior problems. These are, in reality, "people problems," not "pet problems." The environmental and training requirements of the potbellied pig are more complex and require more understanding than those of the average dog or cat. The author's belief is that the potbellied pig's strong drive to be dominant is a unique behavioral characteristic that more people should be made aware of before acquiring a pet pig. With knowledge of normal pig behavior, problems can be avoided through proper socialization and training. If pet owners consult a veterinarian knowledgeable about pig behavior at the first sign of a problem, treatment usually can be successful.

Prenatal cocaine alters open-field behavior in young swine.

Yucatan minisows received 2 mg/kg cocaine i.v. 4 times daily during the last third of gestation. Their piglets were fostered at birth to paired, unexposed sows with their litters, and studied at age 2 to 9 (young group) and 22 to 29 days (older group). Three to 5 exposed and unexposed piglets of each age group were videotaped together for 30 min on 5 consecutive days in an open-field environment. For each piglet, 41 behaviors were scored, timed, summed and clustered into 9 behavioral categories. With age, and independently of drug exposure, piglets spent more time in ingestion, immobility while alone and play/aggression, and less time in group locomotion. For the first 4 test days, the young exposed piglets spent more time in group immobility and less time in individual locomotion and rooting than their age-matched controls. In contrast, the older exposed and unexposed piglet groups did not differ in any of these behavioral clusters. These results suggest that prenatal cocaine exposure in neonatal swine may transiently affect responses to spatial novelty.