Aggressive Pigs Research Articles

A Functional Single Nucleotide Polymorphism in the 3' Untranslated Region of the Porcine JARID2 Gene Is Associated with Aggressive Behavior of Weaned Pigs after Mixing.

In pig production, pigs often show more aggressive behavior after mixing, which adversely affects animal welfare and growth performance. The Jumonji and structural domain-rich AT interaction domain 2 (JARID2) gene plays an important role in neurodevelopment in mice and various psychiatric disorders in humans. The JARID2 gene may impact the aggressive behavior of pigs. By observing the behavior of 500 weaned pigs during the first 72 h after mixing, the ear tissue samples of the 12 most aggressive and 12 least aggressive pigs were selected for DNA resequencing based on the intensity of their aggressive behavior. Large group correlation analysis indicated that the rs3262221458 site located in the 3'-UTR region of the porcine JARID2 gene has a strong relationship with the aggressive behavior of weaned pigs. Pigs with the mutant TT genotype of rs3262221458 have more aggressive behavior than those pigs with the GG and GT genotypes. The dual luciferase assay indicated that the luciferase activity of the plasmids containing the G allele of rs326221458 was significantly less than that of plasmids containing the T allele of rs326221458 and control groups. The binding ability of miR-9828-3p to sequences containing the T allele was less than that of sequences containing the G allele. The overexpression of miR-9828-3p in porcine neuroglial cells (PNGCs) and PK15 cells significantly decreased the mRNA and protein levels of the JARID2 gene. In addition, miR-9828-3p inhibited the proliferation of PNGCs. After inhibiting miR-9828-3p, the mRNA and protein expression levels of JARID2 increased, and the proliferation of PNGCs showed an opposite trend to the cells that forced the expression of miR-9828-3p. In addition, interference with the JARID2 gene by siRNA can effectively inhibit the proliferation of PNGCs. In summary, we found that the rs326221458 locus regulates the expression of the JARID2 gene by affecting the binding of miR-9828-3p and the JARID2 gene, thereby affecting the aggressive behavior of weaned pigs after mixing.

Comprehensive Genome and Transcriptome Analysis Identifies SLCO3A1 Associated with Aggressive Behavior in Pigs.

Copy number variation (CNV) represents a significant reservoir of genetic diversity within the genome and exhibits a strong association with economically valuable traits in livestock. The manifestation of aggressive behavior in pigs has detrimental effects on production efficiency, immune competency, and meat quality. Nevertheless, the impact of CNV on the aggressive behavior of pigs remains elusive. In this investigation, we employed an integrated analysis of genome and transcriptome data to investigate the interplay between CNV, gene expression changes, and indicators of aggressive behavior in weaned pigs. Specifically, a subset of pigs comprising the most aggressive pigs (MAP, n = 12) and the least aggressive pigs (LAP, n = 11) was purposefully selected from a herd of 500 weaned pigs following a mixing procedure based on their composite aggressive score (CAS). Subsequently, we thoroughly analyzed copy number variation regions (CNVRs) across the entire genome using next-generation sequencing techniques, ultimately revealing the presence of 6869 CNVRs. Using genome-wide association study (GWAS) analysis and evaluating variance-stabilizing transformation (VST) values, we successfully identified distinct CNVRs that distinguished the MAP and LAP counterparts. Among the prioritized CNVRs, CNVR-4962 (designated as the top-ranked p-value and VST value, No. 1) was located within the Solute Carrier Organic Anion Transporter Family Member 3A1 (SLCO3A1) gene. The results of our analyses indicated a significantly higher (p < 0.05) copy number of SLCO3A1 in the MAP compared to the LAP. Furthermore, this increased copy number exhibited a positive correlation with the CAS of the pigs (p < 0.05). Furthermore, we integrated genomic data with transcriptomic data from the temporal lobe to facilitate the examination of expression quantitative trait loci (eQTL). Importantly, these observations were consistent with the mRNA expression pattern of SLCO3A1 in the temporal lobe of both MAP and LAP (p < 0.05). Consequently, our findings strongly suggest that CNVs affecting SLCO3A1 may influence gene expression through a dosage effect. These results highlight the potential of SLCO3A1 as a candidate gene associated with aggressive traits in pig breeding programs.

Identification of functional single nucleotide polymorphisms in the porcine SLC6A4 gene associated with aggressive behavior in weaned pigs after mixing.

Variation in genes of the serotonergic system influences aggressive behavior by affecting serotonin levels in the central and cortical nervous system. SLC6A4 (serotonin transporter) is a master regulator of 5-HT signaling and involved in the regulation of aggressive behavior in humans and rodents. To identify potential functional single nucleotide polymorphisms (SNPs) for the porcine SLC6A4 gene associated with aggressive behavior, a total of 500 pigs (268 barrows and 232 gilts) were selected and mixed in 51 pens. Their behavior was recorded and observed for 72 h after mixing. Based on a composite aggressive score (CAS), the most aggressive and the least aggressive pigs within each pen were selected separately (a total of 204 pigs). Ear tissue was sampled to extract genomic DNA. Eight SNPs in the 5'-flanking region, coding region, and 3'-untranslated region (3'-UTR) of SLC6A4 were genotyped, of which 6 SNPs had significant differences (P < 0.05) in allele frequency between the most aggressive and least aggressive pigs. Luciferase activity was greater in plasmids of genotype GG than plasmids of genotype CC of rs345058216 (P < 0.01). Computational analysis nominated MAZ as putative transcription factor (TF) with higher probability to bind the SLC6A4 promoter at the SNP (rs345058216) site. Also, we demonstrated that MAZ overexpression modulates SLC6A4 promoter activity in allele-specific manner with an in vitro assay. In addition, we demonstrated that SLC6A4 was a direct target of miR-671-5p. The dual luciferase reporter gene assay and cell transfection were performed to examine the role of miR-671-5p in regulating SLC6A4 expression. The luciferase assays revealed that the SNP rs332335871 affects regulation of miR-671-5p in SLC6A4 expression. After overexpression of miR-671-5p in porcine primary neural cells, the SLC6A4 mRNA levels can be significantly reduced. In conclusion, we here found that miR-671-5p and MAZ mediated porcine SLC6A4 expression level, which provides the possible molecular mechanism of aggressive behavior.

A Single-Nucleotide Polymorphism in the Promoter of Porcine ARHGAP24 Gene Regulates Aggressive Behavior of Weaned Pigs After Mixing by Affecting the Binding of Transcription Factor p53.

Pigs are important biomedical model animals for the study of human neurological diseases. Similar to human aggressive behavior in children and adolescents, weaned pigs also show more aggressive behavior after mixing, which has negative effects on animal welfare and growth performance. The identification of functional single-nucleotide polymorphisms (SNPs) related to the aggressive behavior of pigs would provide valuable molecular markers of the aggressive behavioral trait for genetic improvement program. The Rho GTPase–activating protein 24 (ARHGAP24) gene plays an important role in regulating the process of axon guidance, which may impact the aggressive behavior of pigs. By resequencing the entire coding region, partially adjacent introns and the 5′ and 3′ flanking regions, six and four SNPs were identified in the 5′ flanking region and 5′ untranslated region (UTR) of the porcine ARHGAP24 gene, respectively. Association analyses revealed that nine SNPs were significantly associated with aggressive behavioral traits (p = < 1.00 × 10–4–4.51 × 10–2), and their haplotypes were significantly associated with aggressive behavior (p = < 1.00 × 10–4–2.99 × 10–2). The core promoter region of the ARHGAP24 gene has been identified between −670 and −1,113 bp. Furthermore, the luciferase activity of allele A of rs335052970 was significantly less than that of allele G, suggesting that the transcriptional activity of the ARHGAP24 gene was inhibited by allele A of rs335052970. It was identified that the transcription factor p53 bound to the transcription factor binding sites (TFBSs) containing allele A of rs335052970. In porcine primary neural cells, p53 binds to the target promoter region of the ARHGAP24 gene, reduces its promoter transcriptional activity, and then reduces its messenger RNA (mRNA) and protein expression. The results demonstrated that the ARHGAP24 gene had significant genetic effects on aggressive behavioral traits of pigs. Therefore, rs335052970 in the ARHGAP24 gene can be used as a molecular marker to select the less aggressive pigs.

Once bitten, twice shy: Aggressive and defeated pigs begin agonistic encounters with more negative emotions

Aggression between unfamiliar commercial pigs is common and likely invokes strong emotions in contestants. Furthermore, contest outcomes affect subsequent aggressive behaviour, suggesting a potential lasting influence on affective state. Here we used a combination of qualitative and quantitative methods to assess the emotional expression of pigs in agonistic encounters. We investigated how recent victory or defeat influences emotions expressed in a subsequent contest, and the role of aggressiveness as a personality trait in emotional expression. We observed the pre-escalation contest behaviour (second contest; age 13 wks) in animals of different aggressiveness (categorised using two resident intruder tests as Agg+ or Agg-, age 9 wks), which had recently won or lost a contest (first contest; 10 wks). We measured gaze direction and ear position. Observers watched video clips of the initial 30 s of the second contest and evaluated the emotional expression of 57 pigs (25 contest 1 winners, 32 contest 1 losers) using qualitative behavioural assessment (QBA) with a fixed list of 20 descriptive terms.QBA identified three principal components (PCs), accounting for 68% of the variation: PC1 (agitated/tense to relaxed/content), PC2 (fearful/aimless to confident/enjoying) and PC3 (listless/ indifferent). Agg- pigs and males showed a more positive emotionality (PC2). PC1 and PC3 were unaffected by first contest outcome and aggressiveness. Agg+ pigs were more likely to hold their ears back (X2 =7.8, p = 0.005) during the early contest period. Differences in attention were detected in the contest outcome × aggressiveness interaction (χ24.3, p = 0.04), whereby approaching the opponent was influenced by winning and losing in the Agg- pigs only. QBA and gaze behaviour reveal differences in emotional valence between pigs of different aggressiveness: less aggressive pigs may be more susceptible to the emotional impact of victory and defeat but overall, more aggressive pigs express more negative emotionality at the start of agonistic encounters.

Identifying blood-based biomarkers associated with aggression in weaned pigs after mixing

Animal behavior, including agonistic behavior, is regulated by various neurotransmitters and hormones in the blood. To Identify blood-based biomarkers associated with aggression in weaned pigs after mixing, a total of 500 weaned pigs from 65 litters were selected and mixed into 51 pens with littermates separately placed into different pens, and their behavior was recorded for 36 h. Blood samples were taken at 24 h before mixing and 24 h after mixing. An aggressive behavior index composite aggressive score was used to assess the aggressive behavior of weaned pigs after mixing. The most aggressive (n = 51) and the least aggressive pigs (n = 51) were selected in each pen. The concentrations of plasma triiodothyronine (T3) in the most aggressive pigs were lower (P < 0.01) than those of the least aggressive pigs at 24 h before (3.42 vs. 5.56 ng/mL) and 24 h after regrouping (3.88 vs. 5.51 ng/mL). In addition, skin lesion scores on the front body in the most aggressive pigs was greater (Pearson Chi-Square = 14.053; P = 0.001) than those of the least aggressive pigs 2 h after mixing. The concentrations of salivary cortisol from pen at 2, 24, and 48 h after mixing were higher than that at 24 h before mixing (2.2, 1.8, 2.1 vs. 0.9 ng/mL; P < 0.05). Plasma triiodothyronine levels at −24 (3.42 vs. 5.56 ng/mL; P < 0.05) and 24 h (3.88 vs. 5.51 ng/mL; P < 0.05) of mixing were higher in the most aggressive pigs than in the least aggressive pigs. The most aggressive pigs had less whole blood 5-hydroxytryptamine (293 vs. 330 ug/mL; P < 0.05) and more platelet number (1926 vs. 1571 ×109; P < 0.05) than the least aggressive pigs at 24 h after mixing. Number of defeat was positively related (r = 0.241, P < 0.05) to plasma tryptophan at 24 h after mixing. A significant canonical correlation (r = 0.7734, P = 0.006) was found between blood-based biomarkers and aggressive behavior indicators at 24 h before mixing. In conclusion, in this research blood-based biomarkers were partly associated with social stress-induced aggression in pigs, but the relationships are complicated.

A kinetic energy model based on machine vision for recognition of aggressive behaviours among group-housed pigs

The aim of this study is to build a kinetic energy model to recognise aggressive behaviours in pigs. Pig mixing experiments were performed 10 times. In each experiment, 7 pigs from 3 pens were mixed and then videos of the first 3 h after mixing and the 3 h after 24 h were selected as experimental data. A 30 h data of 5 groups of pigs were used as training set and a 30 h data of another 5 groups of pigs as test set. Firstly, according to connected area and adhesion index, aggressive pigs were separated from the herd and then key frame sequences with aggression were extracted. Secondly, head and 4 kink points of pigs were selected as feature points. By analysing motion of these points, kinetic energy of 2 aggressive pigs was calculated and kinetic energy difference between adjacent frames was selected as features. Finally, these features were trained by using hierarchical clustering to obtain the thresholds of high and medium aggression. These thresholds were used to design the rule of aggression recognition. By using the proposed algorithm, high aggression could be recognised with an accuracy of 95.8%, a sensitivity of 92.8%, specificity of 96.7% and precision of 90.2%, and medium aggression could be recognised with an accuracy of 92.3%, a sensitivity of 92.6%, specificity of 91.9% and precision of 93.0%. The results indicate that this algorithm can be used to recognise aggressive behaviours of pigs.

Relationships among aggressiveness, fearfulness and response to humans in finisher pigs

Mixing unfamiliar pigs is common in modern production, resulting in intense aggression potentially leading to injury and stress. One solution is breeding against aggressiveness. However, in order to anticipate the consequences of such selection, we need to understand how individual aggressiveness is related to other behavior traits. Tests were used to assess three traits of importance to pig producers: interaction with humans, response to handling, and fearfulness. Test responses (human approach (HAT), handling, and novel object (NOT)) were compared with skin lesions for 257 grow-finish pigs, mixed at 10 wk of age. Skin lesions, a reliable proxy for aggressiveness, were counted pre-mixing, 24 h post-mixing, and 3 wk post-mixing. Lesions were recorded by body location (front, middle, rear). HAT was conducted at 14 wk of age in home pens by all-occurrence scans every 30 s for 9 min. Frequency and intensity (low/moderate or extreme force) of oronasal contact with observer was recorded. Activity and reactivity while entering, in, and leaving a weigh crate were recorded in the handling test (14 and 17 wk of age). NOT was conducted at 17 wk of age. Pigs were moved to an arena, given a 1 min acclimation period, then 5 min exposure to a novel object (basketball). Pigs were scored for latency to approach within 1 m, 0.5 m, and to touch the ball, and on number of times crossing the 1 m and 0.5 m lines, and touching the ball. Generalized linear mixed models compared behavior test variables and lesions. Test responses were compared using a Mantel test. Pigs with more 24 h post-mix front lesions took longer to cross the 1 m line (P = 0.049). Pigs with more 24 h post-mix rear lesions interacted intensely with observer (P = 0.026). Pigs with more 3 wk post-mix front lesions were less active in the weigh crate (P = 0.021) and took longer to touch the ball (P = 0.033). Pigs with more 3 wk post-mix middle lesions were faster to the 0.5 m line (P = 0.005), took longer to touch (P = 0.006), but touched it more (P = 0.049). There were no significant relationships between behavior tests, suggesting no consistency in responses across contexts. In conclusion, responses in HAT and NOT were related to 24 h post-mix lesions, while responses in NOT and handling test were related to 3 wk post-mix lesions suggesting that selecting for less aggressive pigs could have unintended consequences for other important behavior traits and that these relationships should be explored further.

Image motion feature extraction for recognition of aggressive behaviors among group-housed pigs

The aim of this study is to develop a computer vision-based method to automatically detect aggressive behaviors among pigs. Ten repetitions of the same experiment were performed. In each of the experiment, 7 piglets were mixed from three litters in two pigpens and captured on video for a total of 6h. From these videos, the first 3h of video after mixing were recorded asa training set, and the 3h of video after 24h were recorded asa validation set. Connected area and adhesion index were used to locate aggressive pigs and to extract key frame sequences. The two pigs in aggression were regarded asa whole rectangle according to their characteristics of continuous and large-proportion adhesion. The acceleration feature was extracted by analyzing the displacement change of four sides of this rectangle between adjacent frames, and hierarchical clustering was used to calculate its threshold. Based on this feature, the recognition rules of medium and high aggression were designed. Testing 10 groups of pigs, the accuracy of recognizing medium aggression was 95.82% with a sensitivity of 90.57% and with a specificity of 96.95%, and the accuracy of recognizing high aggression was 97.04% with a sensitivity of 92.54% and with a specificity of 97.38%. These results indicate that the acceleration can be used to recognize pigs’ aggressive behaviors.

Effect of lairage time, behaviour and gender on stress and meat quality parameters in pigs.

The objective of this study was to determine the effects of lairage time (short vs. long), behavior (aggressive vs. non-aggressive) and gender (gilts, barrows and boars) on stress and meat quality parameters in pigs (n = 100). In the group with short lairage, aggressive behavior of gilts and boars was observed. At exsanguination, blood samples were collected and levels of blood lactate and plasma cortisol were determined. Post mortem pH value, temperature, drip loss, sensory and instrumental color and meat quality class were determined on the muscle Longissimus dorsi. Higher blood lactate concentration (P < 0.05) and skin blemish score (P <0.001), lower temperature (P < 0.05) and drip loss (P < 0.01), as well as darker, less red and yellow meat color (P < 0.001) were found after long lairage compared to short lairage. Gilts had higher plasma cortisol concentrations than barrows (P < 0.05), while barrows had lower skin blemish scores (P < 0.05) than gilts and boars after long lairage. The highest incidence of PSE (pale, soft and exudative) meat was observed in barrows (100.00%) and boars (91.67%) after short lairage, while the lowest incidence of PSE meat was found in barrows (28.89%) after long lairage. Aggressiveness affected meat temperature, as aggressive pigs had higher meat temperature (P < 0.05) than non-aggressive pigs.

Pigs’ aggressive temperament affects pre-slaughter mixing aggression, stress and meat quality

Pre-slaughter stress has a negative impact on animal welfare and on meat quality. Aggressive behaviour when pigs are mixed together for transportation to, or on arrival at, the abattoir is an important factor in pre-slaughter stress. Aggressiveness of pigs varies between individuals in the population, and this study investigated its effects on stress and meat quality at slaughter. We mixed pigs at a young age to identify individuals of high (H) or low (L) aggressive temperament using the previously validated approach of lesion scoring. To contrast extremes of social stress single-sex groups of eight pigs were mixed according to their aggressiveness in HH, HL or LL combinations or left unmixed (U) prior to transport and slaughter (n = 271). Each treatment was replicated in at least two groups in each of four slaughter batches. Mixing per se had little effect, but mixed groups composed of aggressive pigs (HH) had more carcass skin lesions and higher levels of plasma cortisol at slaughter and had loin muscle samples with higher pH at 24 h, and lower redness (a*) and yellowness (b*) compared to the other treatments. Females had higher levels of plasma cortisol at slaughter, a more rapid decline in pH post-slaughter and greater lean content of meat. Lactate and creatine kinase (CK) levels and meat pH were affected by the interaction of sex and treatment. Genetic factors, dam and sire line composition, and halothane locus (ryanodine receptor 1, RYR1) genotype, also affected a number of production and meat quality parameters as expected. Additionally, ‘commercially normal’ levels of social stress were studied in four further slaughter batches with no manipulation of group composition (n = 313). In these pigs, the proportion of unfamiliar pigs and group size of lairage groups explained limited variation in lesion scores at slaughter, but earlier aggressiveness did not. High numbers of skin lesions on the carcass were associated with high levels of cortisol and lactate and low glucose at slaughter, but not with meat quality measures. When stress and meat quality measures were compared for all pigs, high lactate was associated with low early pH and high drip loss, while high cortisol and CK were associated with high pH at 24 h and changes in meat colour. In conclusion, mixing pigs of above average aggressiveness resulted in greater aggression and stress, and changes in meat quality parameters, consistent with the effects of pre-slaughter stress on muscle chemistry.

Resident–Intruder Trait Aggression is Associated with Differences in Lysine Vasopressin and Serotonin Receptor 1A (5‐HT1A) mRNA Expression in the Brain of Pre‐Pubertal Female Domestic Pigs (Sus scrofa)

Aggressive behaviour exhibited by domestic pigs following encounters with unfamiliar individuals is a serious welfare and economical problem. Aggression resulting in skin lesions is similarly prevalent in prepubertal pigs of either sex. Little is known about the neural circuits and neuropeptides that control aggression in the pig. Because there is evidence for the involvement of the vasopressin and serotonergic systems in the regulation of aggressive behaviour in male mammals, we sought differences using quantitative in situ hybridisation of vasopressin and serotonin 1A receptor (5-HT1A) mRNA expression within specific brain regions of aggressive and nonaggressive prepubertal female pigs. The number of cells expressing vasopressin mRNA was significantly higher in aggressive pigs in the medial amygdala, lateral septum (LS) and showed a similar trend in the bed nucleus of the stria terminalis (BnST) but not the paraventricular nucleus (PVN) or supraoptic nucleus. The 5-HT1A receptor was widely expressed through the porcine brain and a significantly lower intensity (silver grain density) of 5-HT1A mRNA expression was observed in the BnST. In the medial amygdala and LS fewer cells expressed 5-HT1A mRNA in aggressive pigs but no differences were found in the PVN. In the absence of inbred strains or selection lines, these findings have shown that prior identification of phenotypic behavioural extremes in a population in advance of neural studies is a useful technique. Moreover, these findings support a central role for vasopressin and serotonin in the mediation of high trait aggression in prepubertal female pigs.

Early life predictors of the development of aggressive behaviour in the domestic pig

Individuals show stable differences in their aggressive responses towards unfamiliar conspecifics. We investigated the extent to which variables present during early life could be identified that were correlated with these later individual differences in aggressive behaviour. The behaviour and growth of 125 domestic pigs, Sus scrofa, from 16 litters, were studied from birth until 18 days after weaning, when they were tested on two occasions in resident–intruder tests to measure their aggressiveness. Aggressiveness was affected by litter, although not by sex. A number of early life correlates of later resident–intruder aggressiveness were found at the litter level. Pigs became more aggressive if they had been born into larger litters. Pigs in these aggressive litters were more active in the 8-h period immediately after birth, perhaps taking longer to achieve satiety at the udder. They were also in poorer condition 2 days after birth. Aggressive pigs also engaged in more pushing with littermates over the whole preweaning period. The best correlates of aggressiveness appear to be a number of correlated variables relating to low nutrition, either prenatally or in the early postnatal period. The results are consistent with the concept that early environmental conditions can programme behavioural responses for later life.

Individual aggressiveness measured in a resident-intruder test predicts the persistence of aggressive behaviour and weight gain of young pigs after mixing

Young growing pigs of both sexes housed in littermate groups of eight were given an aggressiveness score based on two resident-intruder tests. They were then mixed into new groups of eight, composed of four randomly selected pigs from each of two litters, and behaviour was observed for 2 days (days 1 and 2). Aggressive social behaviour at mixing was analysed using weight and aggressiveness score (at both the group and individual levels) as explanatory variates. On day 1: heavier pigs in each group were more involved in fighting, won more fights, and also initiated more brief aggressive acts (headknocks and bites). Bullying was more frequent in groups with higher aggressiveness scores, and aggressive pigs also initiated more headknocks. On day 2: pigs with high aggressiveness scores persisted in showing aggressive behaviour, initiating fights, headknocks and chases. Aggressiveness score was now also associated with fighting success (in addition to weight). On both days, pigs preferred to lie with littermates rather than unfamiliar pigs, although this preference was less marked on day 2. A stronger preference for littermates was shown in heavier groups. A greater number of skin lesions were recorded at the beginning of day 2 in groups containing heavier pigs and/or pigs with higher aggressiveness scores. Weight gain in the 5 days following mixing was lower in groups containing pigs with high aggressiveness scores. Overall, weight and aggressiveness score (measured in a resident-intruder test) each affected different aspects of aggressive behaviour at mixing. While weight predicted success in agonistic interactions, aggressiveness affected the nature and time scale of interaction: high aggressiveness score pigs showed more one-sided aggression (bullying) and their aggressive behaviour was more persistent, continuing into the day after mixing. Thus, aggression at mixing can be reduced by mixing smaller pigs, and identifying a means of reducing individual aggressiveness would be worthwhile.

Making pigs less ‘piggy’

William Muir and other Purdue University researchers aim to increase hog production by a unique route – identifying the genes responsible for aggression in pigs. Within groups, aggressive pigs grow better at the expense of less aggressive pigs and overall group productivity. Thus, groups of less-aggressive pigs should grow faster. Muir, who previously found a genetic basis for aggression in chickens, suspects pig aggression will also have a genetic component. He hopes to identify such genes using marker-assisted selection. The stakes are high; even a 20% increase in productivity will result in farmers receiving an additional $2 billion per year. And that's a lot of bacon! (http://news.uns.purdue.edu/html4ever/010119.Muir.hoggenome.html) NJ

Does aggressiveness of individuals affect the feeding behaviour of group-housed growing pigs?

The feeding behaviour of group-housed pigs differs from that of pigs housed individually in that they make fewer visits to the feeder of a longer duration (Bornett et al., 2000). Possible reasons for this difference in feeding behaviour include competition and group cohesion and these may be influenced by group composition in terms of aggressiveness. Indeed, Erhard et al. (1997) found that groups comprising all low aggressive pigs integrated into a group quicker than groups of all high aggressive pigs. The aim of this study was to investigate the effect of aggressiveness of individuals on the feeding behaviour of group-housed growing pigs.

Evidence for aggression-modulating pheromones in prepuberal pigs

A series of behavioral bioassays were conducted to determine the aggression-influencing properties of urine and other fluids. Subjects were prepuberal castrated male and female domestic pigs from commercial stocks. In the behavior assay, pigs were painted with a test fluid and grouped for a videotaped 90 min observation period. Experiment 1 validated use of videotape recording by showing that duration of aggressive behavior registered live was correlated with that obtained from video records (R = .98). In experiment 2, urine and plasma collected from actively aggressive pigs reduced the durations of aggressive behavior of test pigs compared with the effects of urine and plasma collected from socially stable, handled pigs. In Experiment 3, a new set of test pigs confirmed that urine from fighting pigs reduced the duration of attack by test pigs compared with urine from nonfighting, handled pigs. In addition, the suggested reproductive pheromone, 5 alpha-androst-16-en-3-one, substantially reduced the duration of attack. The effects of gender and aggressive state of urine-donor pigs on test pigs was determined in Experiment 4. Again, urine from castrated male and female aggressive pigs reduced attack by test pigs compared with the level of attack shown by test pigs coated with urine from handled castrated males and females. Urine from fighting and nonfighting intact males had similar effects on test pig aggression. In Experiment 5, urine was obtained from nonhandled, socially stable pigs in their home pens and again from the same pigs after they had been regrouped (aggressive). These urine types had no significant influence on test pigs' aggression over the entire 90-min observation. However, during the first 30 min nonhandled, nonfighting pigs' urine induced less aggression in test pigs than did urine from fighting pigs. Results indicate that urine and blood plasma from aggressive pigs reduces aggression by test pigs compared with the effects of urine from handled pigs. Handling may increase the aggression-promoting properties of urine, and aggression may inhibit this aggression-promoting property.

Validating techniques to sample behavior of confined, young pigs

Ten 1-h segments of videotaped behavior served as the population from which behavior was sampled. Half of the videotape segments were behaviors of recently re-grouped and aggressive pigs and the remaining segments were of the later socially-stable groups. Attack, feeding, drinking, lying, moving and standing were recorded. Time-sampling (recording less than the full periods) resulted in acceptable correlations and mean values when sampling periods were greater than 20 min per hour. Focal animal sampling was an accurate sampling technique for all behaviors except attack. Observing videotapes at 4 times faster than life provided an accurate sample of all behaviors, but viewing tapes 24 times faster than life was inaccurate for drinking and feeding behavior. These results highlight the need for validation of sampling techniques for studies measuring pig behavior.

Time-restricted feeding of pigs: social and feeding behavior (1984)

Twenty finishing pigs were used to evaluate effects of time-restricted feeding on social interactions and feeding patterns of pigs at feeding time. Correlation analysis for pairs of traits, involving feeding activities, social interactions, and rate of gain indicate that more aggressive pigs went first to the feeder, fed more frequently, and gained faster. Although on continuous artificial lighting, timed-fed pigs displayed more feeding and aggressive behavior during day light hours.; Swine Day, Manhattan, KS, November 15, 1984