Two important questions in bioacoustics are whether vocal repertoires of animals are graded or discrete and how the vocal expressions are linked to the context of emission. Here we address these ...questions in an ungulate species. The vocal repertoire of young domestic pigs, Sus scrofa, was quantitatively described based on 1513 calls recorded in 11 situations. We described the acoustic quality of calls with 8 acoustic parameters. Based on these parameters, the k-means clustering method showed a possibility to distinguish either two or five clusters although the call types are rather blurred than strictly discrete. The division of the vocal repertoire of piglets into two call types has previously been used in many experimental studies into pig acoustic communication and the five call types correspond well to previously published partial repertoires in specific situations. Clear links exist between the type of situation, its putative valence, and the vocal expression in that situation. These links can be described adequately both with a set of quantitative acoustic variables and through categorisation into call types. The information about the situation of emission of the calls is encoded through five call types almost as accurately as through the full quantitative description.
Fear of human can impact negatively offspring’s behaviour and cognition whereas early positive handling has positive impacts. The aim of this study was to evaluate the crossed effects of ...trans-generational transfer and familiarisation with human on piglets’ behaviour. Sows were classified into two categories (Fearful, n = 11 and Docile, n = 13) based on whether they avoided human contact or not during a human approach test at 71 days of gestation. Fear of human was not related to salivary cortisol levels of the sows (F =2.72, P = 0.10). Fearful sows’ piglets stood immobilized longer (Chisq= 6.24, P = 0.01), as well females (8.70, P = 0.003) during a tonic immobility test (TIT) at 7 days but not at 15 days. The behaviour of two male and two female piglets per sow (n = 96) was studied after weaning (28 days). We found no effect of sow’s reaction to human on piglets’ emotionality expressed during an open-field test (OFT) at 32–33 days. However, during a Human voluntary approach test (VHAT) piglets born from fearful sows were more fearful than piglets born from docile sows (Chisq=8.23, P = 0.004,). Half of the piglets (n = 48, 1 male and 1 female per sow) were then familiarised with human while the others received minimum contact. We found no main or crossed effect of sow’s reaction to human and piglet’s treatment on piglets’ emotionality during an OFT, nor on their exploratory behaviour during VHAT at 46–47 days. Piglets’ born from fearful sows were less attracted to human during VHAT2 (Chisq=8.33, P = 0.004) and familiarised piglets were more attracted (Chisq=15.05, P < 0.001). Piglets born from docile sows found the reward faster in a spatial maze test than those born from fearful sows. Both sows HAR and piglet familiarisation with human seemed to specifically affect human related behaviours without affecting their general emotionality, but also behaviour in a spatial maze test.
●Sows docility or fearfulness is not linked to salivary cortisol concentration.●Piglets born from docile sows stay less immobile in a tonic immobility test.●Piglets born from docile sows approach more an unfamiliar human.●Piglets born from docile sows are faster to find a reward in a maze.●Piglets tamed after weaning are less fearful of humans whatever their sow reaction.
Pig groups are known to be organised along dominance hierarchies. Little is known about the characteristics of the hierarchy in groups of sows and there are various methods to calculate dominance ...ranks within the hierarchy. Assessing dominance through recording agonistic interactions requires time-consuming observations. In order to compare the ranking methods, to investigate the sociometric characteristics of pig hierarchy such as stability, linearity and steepness, and to identify easy-to-record proxy indicators of hierarchy, four groups of 18 (+/-2) gestating sows were studied. The sows were followed from 71 to 106 days of gestation. Starting from day 79, the access to the self-locking automatic feeders was limited to 6hours a day from to stimulate agonistic interactions. Each week, agonistic interactions were recorded during six continuous hours allowing the calculation of several dominance scores and sociometric variables. The restriction of feeding time increased the number of agonistic interactions but did not impact the proportion of agonistic behaviours with physical contact. The Dominance index, the David score and the Elo-score, used to rank the sow according to their dominance position, were highly inter-correlated (R >0.92). The hierarchy was stable (stability index Stab = 0.996 ± 0.081), transitive (proportion of transitive triads Pt= 0.967 ± 0.035), quasi linear (Improved Landau index of linearity h’ = 0.701 ± 0.068) and moderately steep (real steepness Steep=0.545 ± 0.085). The rankings obtained through Elo-score were highly correlated with the mean order feeding order (RS = 0.76), weakly correlated with the total number of feeder visits (RS =-0.21, P<0.001) and not correlated with the daily mean time spent in the feeder (RS =0.09, P=0.10), or the total daily spent time in the feeder (RS =0.10, P=0.07). The rank was also highly negatively correlated to parity (RS =-0.83, P<0.001) and to the weight at the end of gestation (RS =-0.75, P<0.001). The results suggest that dominance hierarchies in stable groups of pregnant sows are stable and strong. Dominance rank of an individual can be estimated according to the feeding order, body weight or parity if there is enough variability in the group.
•Elo-score, dominance index and David score similarly ranked sows’ dominance•The hierarchy inside groups of pregnant sows is stable, transitive and quasi-linear•The Feeder order is a good indicator of hierarchical status of pregnant sows•Parity and weight are good predictors of hierarchical status in mixed parity sow groups
Few studies have examined sows and piglets' use of outdoor access during their first weeks of life, when reared with access to a hut and a pasture as in the organic system. We studied whether the age ...of the piglets and the season of the year influenced the use of an outdoor area by piglets and the sow, and the use of indoor spaces. For this, the localisation of sows and their piglets inside and outside the hut was analysed on 16 sows and their litters during the summer and 16 others during the winter, by scan sampling, on days 2, 7 and 13 after parturition in an organic herd in Denmark. When inside the hut, the number of piglets in the creep area, next to the sow or other piglets was noted. All parameters were analysed by linear mixed-effects ANOVA models. Sows were less often observed outside the hut in the wintertime and during the mornings compared to later times of the day (P<0.001). Furthermore, the sows increased their outdoor use with the age of their litter (P<0.001). The season also influenced the piglet use of outdoor areas (winter < summer; P<0.001). Piglets that were observed outside for the first time were older (8.9±0.9 d) during winter than during summer (3.5±0.5 d). The proportion of piglets observed outside increased with age, with a significant Season x Age interaction (P<0.001). The proportion of observations where the sows and piglets were outdoors together increased with the piglets’ age (P < 0.001). Sows’ outing was correlated with summer (R=0.3) and winter (R=0.2) temperatures, unlike piglets, where outings were correlated only with summer temperatures (R=0.3, P<0.001). The proportion of piglets observed in the creep area was significantly affected by the age with a Season x Age interaction effect (P<0.001). Piglets were rarely observed lying alone inside the hut. The proportion of piglets in contact with the sow and other piglets inside the pen was influenced by a significant Age x Season interaction effect (P<0.001). We showed that piglets given access to an outside paddock gradually increase their use with age and don’t go outside right away. Their first exit and the proportion of piglets outside depended also on the season. In general, a higher proportion of sows and piglets were observed indoor during the wintertime. Thus, sows and piglets adjust their use of outdoor paddock with season and piglet age during the first weeks of life.
•Piglets adjust their use of outdoor paddock according to season and age.•Outdoor use by sows, with or without their piglets, increased with piglets’ age.•The first observation of piglets outside was later in winter than in summer.•Use of creep area depended on Season x Age interaction.•Contact between the sow and other piglets inside the hut depended on Season x Age.
Vocal expression of emotions has been observed across species and could provide a non-invasive and reliable means to assess animal emotions. We investigated if pig vocal indicators of emotions ...revealed in previous studies are valid across call types and contexts, and could potentially be used to develop an automated emotion monitoring tool. We performed an analysis of an extensive and unique dataset of low (LF) and high frequency (HF) calls emitted by pigs across numerous commercial contexts from birth to slaughter (7414 calls from 411 pigs). Our results revealed that the valence attributed to the contexts of production (positive versus negative) affected all investigated parameters in both LF and HF. Similarly, the context category affected all parameters. We then tested two different automated methods for call classification; a neural network revealed much higher classification accuracy compared to a permuted discriminant function analysis (pDFA), both for the valence (neural network: 91.5%; pDFA analysis weighted average across LF and HF (cross-classified): 61.7% with a chance level at 50.5%) and context (neural network: 81.5%; pDFA analysis weighted average across LF and HF (cross-classified): 19.4% with a chance level at 14.3%). These results suggest that an automated recognition system can be developed to monitor pig welfare on-farm.
This study examined whether piglet distress vocalizations vary with age, body weight and health status, according to the predictions of the honest signalling of need evolutionary model. Vocalizations ...were recorded during manual squeezing (a simulation of being crushed by mother sow) and during isolation on Days 1 and 7 after birth in piglets from 15 litters. We predicted that during squeezing, younger, lighter and sick piglets would call more intensely because they are in higher risk of dying during crushing and therefore they benefit more from the sow's reaction to intensive vocalization. For isolation, we predicted that lighter and younger piglets would call more because they are more vulnerable to adverse effects of the separation. Calls were analyzed in their time and frequency domain. The rate of calling, call duration, proportion of high-pitched calls and eight acoustic parameters characterizing frequency distribution and tonality were used as indicators of acoustic signalling intensity. Piglets that experienced "squeezing" on Day 1 produced more intense acoustic distress signalling than on Day 7. Lighter piglets called more during squeezing than heavier piglets. Health status did not significantly affect any of the indicators of intensity of vocalization during squeezing. In isolation, none of the parameters of vocalization intensity were affected either by the age or by the weight of the piglets. In summary, the model of honest signalling of need was confirmed in the squeezed situation, but not in the isolation situation.
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•Precision feeding of sows reduces feed costs by improving sow’s efficiency.•Behaviour and health status can strongly influence individual nutrient requirement.•Thermal conditions and ...housing type can affect nutrient requirement.•Machine learning to automatize and improve precision feeding.
Taking into account individual variability while feeding a group of sows allows feed cost reductions and therefore improves animal efficiency. This precision feeding strategy is based on 1) nutritional models, which are able to predict daily individual nutrient requirements; 2) automatons, that can deliver individual rations; and 3) new technologies such as sensors which provide real-time information on the animal performance and life conditions that should be integrated into the estimation of requirements. Up to now, only production data (body weight, backfat thickness) have been integrated into the calculation of individual nutrient requirements.
However, the literature reported that health status and behavior, such as physical activity, social behavior, and location in the pen, can strongly influence nutrient requirements. A change in the feeding or drinking behavior can also indicate a health or welfare problem. Sensors, automatons and cameras are now able to detect some diseases or injuries, and record certain on-farm behaviors. Therefore, nutrient requirements should be adjusted based on these health and behavioral parameters. Environmental factors such as thermal conditions, housing type and noise level have also been reported to affect nutrient requirements. On-farm sensors can easily be installed to record these parameters to be integrated into the nutritional model and improve its precision. A decision support system can be used to integrate these new measurements into the nutritional model for gestating sows. It would also be helpful to trigger alerts and propose corrective actions when behavior changes or health issues are detected.
Prenatal sensory experience, notably auditory experience, is a source of fetal memories in many species. The contiguity between sensory stimuli and maternal emotional reactions provides opportunity ...for associative learning in utero but no clear evidence for this associative learning has been presented to date. Understanding this phenomenon would advance our knowledge of fetal sensory learning capacities. In the present study we tested the hypothesis that sounds (human voice) broadcast to pregnant sows while they experienced positive or negative emotional situations influences postnatal reactions of their offspring to these same sounds. The results show that: 1) from the first testing at the age of 2 days, the experimental piglets were less distressed by a social separation than controls if they heard the "familiar" voice, 2) piglets generalized to any human voice although the influence of novel voices was less pronounced, 3) in a challenging situation, piglets were more distressed if they heard the voice that was associated with maternal negative emotional state in utero. These findings open a whole line of new research on the long term effect of in utero associative learning that goes well beyond pigs, providing a framework for reconsidering the importance of sensory and emotional experiences during gestation.
In an effort to mitigate piglet acute responses to surgical castration, the procedure can be preceded by injections of a local anaesthetic. Regardless of potential benefits at castration, the impact ...of local anaesthetics on piglet welfare following the procedure remains under-documented. The present paper is based on data collected in two separate castration studies investigating the impact of injection with procaine, using different injection methods, different volumes of injected drug and different timing of injection, on behavioural responses of 3–4 day old piglets, as measured by indicators of social motivation immediately after castration (Study 1 and 2), as well as behaviours recorded continuously for 10 min upon return to the home pen (Study 2 only). Study 1 involved 597 piglets, and 13 treatments: castration without anaesthesia (CC), local anaesthesia followed by castration involving all combinations of two methods of injection (intra-funicular and intra-testicular) and four intervals between injection and castration (2.5, 5, 10 and 30 min), and sham handling separated by the same four intervals (SH). Study 2 involved 290 piglets and 5 treatments: castration without anaesthesia (CC), castration after intra-testicular injections of 0.5 or 0.3 mL of procaine per testis, and sham handling with either one (SH1) or two stays in a castration bench (SH2). Across both studies, piglets injected with procaine showed signs of reduced motivation to approach their siblings in the social motivation test compared to controls castrated without anaesthesia or sham handled. The indicators of social motivation did not differ from the controls in case of castration 30 min after drug injection. In addition, responses shown in the social motivation test were less impacted after injection of 0.3 compared to 0.5 mL of procaine per testis. In Study 2, piglets injected with 0.5 mL of procaine appeared to be less active at the udder, and displayed more huddled up postures, immediately upon return to the home pen, as compared to piglets injected with 0.3 mL of procaine or the controls castrated without anaesthesia or sham handled. Altogether, the results suggest that injections with a procaine-based local anaesthetic negatively impact the responses of piglets in a test of social motivation as well as the home-pen behaviour of piglets in the early post-operative period. The present results call for attention towards the post-surgical phase, but understanding the potential welfare impacts as well as the motivational changes underlying these findings require further study.
•This study examined behaviour of piglets in the minutes after castration.•Behaviour was studied in a test of social motivation and upon return to home pen.•Local anaesthesia led to signs of impaired social motivation in piglets.•Locally anaesthetised piglets were less active at udder after castration.•The findings may be interpreted as systemic responses to the procaine anaesthetic.
Although animals rarely use only one sense to communicate, few studies have investigated the use of combinations of different signals between animals and humans. This study assessed for the first ...time the spontaneous reactions of piglets to human pointing gestures and voice in an object-choice task with a reward. Piglets (Sus scrofa domestica) mainly use auditory signals-individually or in combination with other signals-to communicate with their conspecifics. Their wide hearing range (42 Hz to 40.5 kHz) fits the range of human vocalisations (40 Hz to 1.5 kHz), which may induce sensitivity to the human voice. However, only their ability to use visual signals from humans, especially pointing gestures, has been assessed to date. The current study investigated the effects of signal type (visual, auditory and combined visual and auditory) and piglet experience on the piglets' ability to locate a hidden food reward over successive tests. Piglets did not find the hidden reward at first presentation, regardless of the signal type given. However, they subsequently learned to use a combination of auditory and visual signals (human voice and static or dynamic pointing gestures) to successfully locate the reward in later tests. This learning process may result either from repeated presentations of the combination of static gestures and auditory signals over successive tests, or from transitioning from static to dynamic pointing gestures, again over successive tests. Furthermore, piglets increased their chance of locating the reward either if they did not go straight to a bowl after entering the test area or if they stared at the experimenter before visiting it. Piglets were not able to use the voice direction alone, indicating that a combination of signals (pointing and voice direction) is necessary. Improving our communication with animals requires adapting to their individual sensitivity to human-given signals.
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