The short-term behavioural response of sows, but not gilts, to a social stimulus is related to sow aggressiveness in groups

Effects of group size on agonistic interactions in dairy cows: a descriptive study

Group-housed cattle may engage in agonistic interactions over resources such as feed, which can negatively affect aspects of welfare. Little is known about how contextual factors such as group size influence agonistic behaviour. We explored the frequency of agonistic interactions at the feeder when cattle were housed in different-sized groups. We also explored the consistency of the directionality of agonistic interactions in dyads and of the number of agonistic interactions initiated by individuals across the group sizes. Four replicates of 50 cows each were assessed in two group-size phases. In Phase 1, cows were kept in one group of 50. In Phase 2, these same cows were divided into five groups of 10, maintaining stocking density (i.e., ratio of animals to lying stalls and feed bunk spaces). We measured agonistic replacements (i.e., interactions that result in one cow leaving the feed bin and another taking her place) at an electronic feeder using a validated algorithm. We used these data from Phase 1 to calculate individual Elo-ratings (a type of dominance score). Cows were then categorised into five dominance categories based upon these ratings. To ensure a consistent Elo-rating distribution between phases, two cows from each dominance category were randomly assigned to each small group of 10 cows. The mean ± SE number of replacements per cow was similar regardless of whether the cows were housed in groups of 50 (34.1 ± 2.4) or 10 (31.1 ± 4.5), although the groups of 10 were more variable. Further, 81.6 ± 7.7% (mean ± SD) of dyads had the same directionality across group sizes (i.e., the same individual won the majority of interactions in the dyad) and individuals were moderately consistent in the number of replacements they initiated (intraclass correlation coefficient = 0.62 ± 0.11; mean ± SD). These results indicate that the relationship between group size and agonistic behaviour is complex; we discuss these challenges and suggest new avenues for further research.

Emotional Contagion and Social Support in Pigs with the Negative Stimulus

This study expects to confirm the existence of emotional transmission in pigs from multiple perspectives and to provide theoretical references for improving animal welfare in livestock farming. A group that could directly observe (DO) and a group that could not directly observe (NO) were created based on whether or not their peers observed the treatment process, as the treated pig (TP) was treated with electrical shock and the companion pig (CP) either witnessed the treatment inflicted upon TP or not, and a third group was a control group, in which neither pig was stimulated. The behavioral responses of both the TPs and CPs were recorded to evaluate the emotional reaction. The results found that in both the DO and NO groups, the frequency of TP freezing was significantly higher than that of CP, and CP was significantly higher than that of the control group. Interestingly, although the social interaction responses of the CPs were not similar in the DO and NO groups, there were no significant differences between the behaviors of TPs in the DO and NO groups, except for nose-nose contact and a single approach to the partition, which allowed us to conclude that, whether or not the pigs directly observed the negative treatment, they were able to respond accordingly to fear and provide similar social support to their companions who were treated negatively.

Social Status Differentially Affects Behavioral and Immunological Outcomes of Group-Kept Sows Fed Different Dietary Fiber Using Different Length Feeding Barriers

Social conflict is inevitable among group-housed sows and may contribute to poorer welfare among those sows experiencing more social stress. The degree of individual welfare is associated with social position within the group. Therefore, this study examined the effects of social status on behavior, immune, endocrine, and productivity of group-housed pregnant sows fed a diet supplemented with 30% wheat middlings and 15% soybean hulls (MID-SH) or 30% distillers dried grains with solubles and 30% corn germ meal (DDGS-GM) and in pens with individual feeding places made from short (58.4 cm) or long (203.2 cm) barriers. A 2 × 2 factorial design resulted in 4 experimental treatment groups (n = 9 sows/diet-length-block combination): (1) MID-SHshort; (2) MID-SHlong; (3) DDGS-GMshort; (4) DDGS-GMlong. Groups of sows equally representing all diet-length combinations across 4 blocks (n = 36 sows/block) were subjected to a feeding competition test to identify highest (dominant) and lowest (subordinate) ranked sows within each group resulting in 64 sows (n = 16 sows/treatment; n = 32 sows/social status). Data revealed 2- and 3-way interactive effects on aggressive behavior (P < 0.005), postural (P < 0.01), oral (P < 0.0001), and eating (P < 0.005) behaviors, sow mean body weights and gains (P < 0.05) and litter weaning weights (P < 0.05), especially among subordinates in pens with long barriers. Subordinates in pens with long barriers received 21% less aggression and were 73% less likely to be displaced than subordinates in pens with short ones (P < 0.0001). Dietary treatment also influenced some of these measures among the subordinates in pens with long barriers. For example, subordinates in DDGS-GMlong received 64 and 67% less aggression than subordinates in DDGS-GMshort and MID-SHshort (P < 0.005). Eat bouts were greatest among subordinates in MID-SHlong, and sitting and sham-chewing were less. However, those in DDGS-GMlong spent less time standing and laying, and their litters were 15.28 kg heavier (P = 0.01), but overall subordinates fed DDGS-GM diet were lightest and gained less total body weight than those fed MID-SH (P < 0.05). Other measures such as neutrophil-to-lymphocyte ratio were elevated among dominants in MID-SHlong (P < 0.05); whereas, cortisol (P = 0.06) was lowest and glucose (P = 0.09) highest for subordinates in DDGS-GMlong. These data imply that subordinates benefited from being housed in pens with long barriers, but the type of dietary fiber consumed differentially influenced behavioral budget and several sow- or litter-related traits among subordinates in pens with long barriers. In contrast, the subordinates in pens with short barriers had poorer welfare regardless of diet. Collectively, these data imply that social status is a crucial factor contributing to variation in individual well-being among group-housed sows and that sows of different social positions within a group may evoke different biological responses in an attempt to cope.

Forming groups of aggressive sows based on a predictive test of aggression does not affect overall sow aggression or welfare

This experiment examined the effects of group composition on sow aggressive behaviour and welfare. Over 6 time replicates, 360 sows (parity 1-6) were mixed into groups (10 sows per pen, 1.8 m²/sow) composed of animals that were predicted to be aggressive (n = 18 pens) or groups composed of animals that were randomly selected (n = 18 pens). Predicted aggressive sows were selected based on a model-pig test that has been shown to be related to the aggressive behaviour of parity 2 sows when subsequently mixed in groups. Measurements were taken on aggression delivered post-mixing, and aggression delivered around feeding, fresh skin injuries and plasma cortisol concentrations at days 2 and 24 post-mixing. Live weight gain, litter size (born alive, total born, stillborn piglets), and farrowing rate were also recorded. Manipulating the group composition based on predicted sow aggressiveness had no effect (P > 0.05) on sow aggression delivered at mixing or around feeding, fresh injuries, cortisol, weight gain from day 2 to day 24, farrowing rate, or litter size. The lack of treatment effects in the present experiment could be attributed to (1) a failure of the model-pig test to predict aggression in older sows in groups, or (2) the dependence of the expression of the aggressive phenotype on factors such as social experience and characteristics (e.g., physical size and aggressive phenotype) of pen mates. This research draws attention to the intrinsic difficulties associated with predicting behaviour across contexts, particularly when the behaviour is highly dependent on interactions with conspecifics, and highlights the social complexities involved in the presentation of a behavioural phenotype.