Redefining dominance calculation: Increased competition flattens the dominance hierarchy in dairy cows.

Dominance hierarchies are known for mitigating conflicts and guiding priority of access to limited resources in gregarious animals. The dominance hierarchy of dairy cows is typically investigated using agonistic interactions, often monitored at the feed bunk right after fresh feed delivery when competition is high, resulting in frequent interactions. Yet, the outcome of agonistic interactions during times of high competition may be more influenced by cows' high valuation of fresh feed than their intrinsic attributes, such that the dominance hierarchy constructed using agonistic interactions under high versus low competition times might differ. We tested how the structure of the dominance hierarchy changes in relation to different levels of competition in a dynamic group of 48 lactating dairy cows over 10 mo, with 6 cows exchanged every 16 d, for a total of 159 cows. Using a validated algorithm, we continuously detected the actor and reactor of replacement behaviors in 30 feed bins as cows competed for feed. We also calculated the percentage of occupied feed bins to characterize competition at the moment of each replacement. These data were combined to create hierarchies using Elo ratings, separately for 25 occupancy levels ranging from 13% to 100%. For each 1% rise in feeder occupancy, hierarchy steepness fell by 2.41 × 10-3 ± 9.71 × 10-5 (SE), and the percentage of dyads where both cows replaced each other rose by 0.13% ± 0.01%. At the highest feeder occupancy level in comparison to the lowest one, we observed 7.57% more dyads in which the dominant individual (those that won more interactions at the lowest feeder occupancy) started to lose proportionally more. The magnitude of decrease in the winning rate of the dominant individual in those dyads also got amplified by 1.06 × 10-3% ± 1.37 × 10-4% (SE) for each 1% increase in feeder occupancy. These findings illustrate how inferred hierarchies vary with competition, with high competition flattening the hierarchy due to increased success of subordinate animals. We suggest that during heightened competition, increased valuation of resources can affect competitive success more than the individual's intrinsic dominance attributes. We recommend against calculating dominance hierarchies based on agonistic interactions during periods of high competition alone, and more generally urge researchers to differentiate agonistic interactions based on context when constructing dominance hierarchies.

Invited review: Social dominance in dairy cattle: A critical review with guidelines for future research.

Cattle are gregarious animals able to form social relationships. Dominance is one of the most widely studied social behaviors of dairy cattle, especially cows confined indoors. However, much of the past dairy cattle research has used an unstandardized approach, differing in definitions and conceptual understanding of dominance, as well as their methods of data collection and dominance calculation. The first of the 3 aims of this review is to evaluate how dominance relates to the social behavior of housed dairy cows. Cows engage in agonistic interactions to establish and reinforce dominance relationships. An individual's dominance is influenced by intrinsic characteristics, such as personality, and extrinsic factors, including group composition. When competing for resources, agonistic interactions can also be influenced by individual motivational differences, such as hunger, which may diminish the role of dominance in regulating competition. Our second aim is to critically review methods used to assess dominance in cows. This includes discussions on the effect of time and location of data collection on measured values as well as the viability and limitations of some dominance calculation methods. We propose that different methodologies lend themselves to different types of research questions. For example, the use of data stream-based methods that consider the sequence of interactions are useful for estimating how dominance fluctuates with changing conditions and can be used in a dynamically changing group. In contrast, matrix-based methods that aggregate social interactions may be best for identifying the social position of individuals and understanding how social characteristics influence the attributes of a stable hierarchy. Our third aim is to discuss the future of dominance research. We use a flowchart to illustrate guidelines for a more standardized approach to measuring dominance in cattle. We also identify areas in need of further conceptual clarification, suggest practical applications of dominance when managing dairy cattle, and discuss some limitations of dominance research.

Crowd sourcing remote comparative lameness assessments for dairy cattle.

Lameness assessments are rarely conducted routinely on dairy farms and when completed typically underestimate lameness prevalence, hampering early diagnosis and treatment. A well-known feature of many perceptual tasks is that relative assessments are more accurate than absolute assessments, suggesting that creating methods that allow for the relative scoring of which cow is more lame will allow for reliable lameness assessments. Here we developed and tested a remote comparative lameness assessment method: we recruited nonexperienced crowd workers via an online platform and asked them to watch 2 videos side-by-side, each showing a cow walking, and to identify which cow was more lame and by how much (on a scale of -3 to 3). We created 11 tasks, each with 10 video pairs for comparison, and recruited 50 workers per task. All tasks were also completed by 5 experienced cattle lameness assessors. We evaluated data filtering and clustering methods based on worker responses and determined the agreement among workers, among experienced assessors, and between these groups. A moderate to high interobserver reliability was observed (intraclass correlation coefficient, ICC = 0.46 to 0.77) for crowd workers and agreement was high among the experienced assessors (ICC = 0.87). Average crowd-worker responses showed excellent agreement with the average of experienced assessor responses (ICC = 0.89 to 0.91), regardless of data processing method. To investigate if we could use fewer workers per task while still retaining high agreement with experienced assessors, we randomly subsampled 2 to 43 (1 less than the minimum number of workers retained per task after data cleaning) workers from each task. The agreement with experienced assessors increased substantially as we increased the number of workers from 2 to 10, but little increase was observed after 10 or more workers were used (ICC > 0.80). The proposed method provides a fast and cost-effective way to assess lameness in commercial herds. In addition, this method allows for large-scale data collection useful for training computer vision algorithms that could be used to automate lameness assessments on farm.

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.

Automated monitoring of brush use in dairy cattle.

Access to brushes allows for natural scratching behaviors in cattle, especially in confined indoor settings. Cattle are motivated to use brushes, but brush use varies with multiple factors including social hierarchy and health. Brush use might serve an indicator of cow health or welfare, but practical application of these measures requires accurate and automated monitoring tools. This study describes a machine learning approach to monitor brush use by dairy cattle. We aimed to capture the daily brush use by integrating data on the rotation of a mechanical brush with data on cow identify derived from either 1) low-frequency radio frequency identification or 2) a computer vision system using fiducial markers. We found that the computer vision system outperformed the RFID system in accuracy, and that the machine learning algorithms enhanced the precision of the brush use estimates. This study presents the first description of a fiducial marker-based computer vision system for monitoring individual cattle behavior in a group setting; this approach could be applied to develop automated measures of other behaviors with the potential to better assess welfare and improve the care for farm animals.

The Effect of Placement and Group Size on the Use of an Automated Brush by Groups of Lactating Dairy Cattle.

Mechanical brushes are often provided on dairy farms to facilitate grooming. However, current brush designs do not provide data on their use, and thus little is known about the effects of group size and placement of brushes within the pen. The objectives of this study were to automatically detect brush use in cow groups and to investigate the influence of (1) group size and the corresponding cow-to-brush ratio and (2) brush placement in relation to the lying stalls and the feeding and drinking areas. We measured brush use in groups of 60, 48, 36, and 24 cows, with the brush placed either in the alley adjacent to the feed bunk and water trough or in the back alley. Cows used the brush for longer when it was placed in the feed/water alley compared to when placed in the back alley. Average brush use per cow increased when cows were housed in smaller groups, but the brush was never in use more than 50% of the day, regardless of group size. We conclude that brush use increases when availability is increased and when the brush is placed closer to the feed and water.

The effects of cow dominance on the use of a mechanical brush.

An animal's social position within a group can influence its ability to perform important behaviours like eating and resting, but little is known about how social position affects the ability to express what are arguably less important but still rewarding behaviors, such as grooming. We set out to assess if dominance measured at the feeder is associated with increased use of a mechanical brush. Over a 2-year period, 161 dry cows were enrolled in a dynamically changing group of 20 individuals with access to a mechanical brush. We determined dominance using agonistic behaviors at the feeder and retrospectively analyzed brush use for the 12 most, and 12 least dominant individuals during the week before calving. Cows that were more dominant at the feeder used the brush more, especially during peak feeding times. Agonistic interactions at the brush did not differ between dominants and subordinates and were not related to brushing duration. These findings indicate that social position, calculated using competition for feed, affects mechanical brush access such that subordinates use the brush less than dominant cows independent of competition or time of day.

Competition Strategies of Metritic and Healthy Transition Cows.

Our study aimed to characterize social competition strategies in transition cows, and determine how these varied with health status. We retrospectively followed 52 cows during 3 periods (PRE: d -6 to -1 prepartum, POST1: d 1 to 3 postpartum, POST2: d 4 to 6 postpartum). Cows diagnosed with metritis on d 6 postpartum (n = 26) were match paired with healthy cows (n = 26). Measures of agonistic behavior (i.e., replacements at the feeder) and feeding synchrony were determined by an algorithm based on electronic feed bin data, and used to calculate competition strategies via principal component analysis. We found consistent strategies, defined by two components (asynchrony and competitiveness; explaining 82% of the total variance). We observed no differences in strategies when comparing healthy and metritic cows, but metritic cows tended to change their strategies more between PRE and POST1, and between POST1 and POST2, indicating that strategies change in association with parturition and metritis. We conclude that cows show individual variation in competition strategies, and that automated measures of strategy change may help in detecting metritis.

Evaluating the temporal and situational consistency of personality traits in adult dairy cattle.

Recent research suggests that personality, defined as consistent individual behavioral variation, in farm animals could be an important factor when considering their health, welfare, and productivity. However, behavioral tests are often performed individually and they might not reflect the behavioral differences manifested in every-day social environments. Furthermore, the contextual and longer-term temporal stability of personality traits have rarely been investigated in adult dairy cattle. In this study, we tested three groups of lactating Holstein cows (40 cows) using an individual arena test and a novel object test in groups to measure the contextual stability of behavior. Among the recorded individual test parameters, we used seven in the final analysis, which were determined by a systematic parameter reduction procedure. We found positive correlations between novel object contact duration in the group test and individual test parameters object contact duration (Rs = 0.361, P = 0.026) and movement duration (Rs = 0.336, P = 0.039). Both tests were repeated 6 months later to investigate their temporal stability whereby four individual test parameters were repeatable. There was no consistency in the group test results for 25 cows tested twice, possibly due to group composition changes. Furthermore, based on the seven individual test parameters, two personality traits (activity/exploration and boldness) were identified by principal component analysis. We found a positive association between the first and second tests for activity/exploration (Rs = 0.334, P = 0.058) and for boldness (Rs = 0.491, P = 0.004). Our results support the multidimensional nature of personality in adult dairy cattle and they indicate a link between behavior in individual and within-group situations. The lack of stability according to the group test results implies that group companions might have a stronger influence on individual behavior than expected. We suggest repeating the within-group behavioral measurements to study the relationship between the social environment and the manifestation of personality traits in every-day situations.