Response of pre-weaned dairy calves to positive human-animal interaction studied using qualitative behavioural assessment and avoidance distance

The human-animal relationship (HAR) is a crucial aspect for enhancing animal welfare at farm level, particularly when addressed to young animals. Studies have shown that positive human-animal interactions can improve productivity and overall health, while reducing stress and undesirable behaviors. Strategies to strengthen HAR include animal training, socialization, and environmental enrichment. In particular, gentle human touch during sensitive periods, such as after birth, can be highly effective in establishing a positive human-animal relationship and reducing future stress. The aim of this project was to evaluate the effects of a strokes-based Early Positive Human-Animal Interaction (EPHAI) on dairy calves’ response to human approach through two Flight Reaction tests, namely Avoidance Distance Test (ADT) and Calf Escape Test (CET) and their dynamic style of interaction with the environment and conspecifics using the Qualitative Behavioural Assessment (QBA), on a commercial dairy farm in Azambuja, Portugal. In this case study, 101 female dairy calves were divided into two groups: Control (n = 49), experiencing only minimal human-animal interactions pertinent to their management, and Treatment (n = 52), being exposed to a strokes-based EPHAI once per week while housed in individual crates. ADT and CET data were collected once the calves were moved to the collective park. In addition, a QBA was conducted at mixed group level as an indicator of the calves’ state in relation to the EPHAI administration. All data were submitted to statistical analysis considering the main effects of EPHAI and of time, applying different statistical models in accordance with their distribution. Results showed that milk consumption and number of visits to the Automatic Milk Feeder were not affected by EPHAI, likely due to the feeder’s settings. Control and Treatment groups received in total 113 medical treatments (Carposan, Synulox, Zeleris), administered to 49 calves (NC = 26, NT = 23) regardless of the EPHAI effect. Regarding the behavioral detections, 17 sessions of ADT and CET assessed 77 calves from the original study sample, assessing long- and short-term effects of EPHAI. The analysis of variance on ADT showed a significant influence of EPHAI, showing that the Treatment group had a lower avoidance distance (Treatment = 60.8 ± 8.2; Control = 83.8 ± 7.5), suggesting having reduced fear when approached by the assessor. Moreover, CET results supported the ADT outcomes with higher CET scores for the Treatment calves, while also demonstrating a tendency for EPHAI's effect to vanish over time. QBA was conducted on 96 calves (NC = 49, NT = 47), during 14 sessions grouped into two classes (A and B) according to the percentage of Treatment calves over the total in the group pen. The analysis of the main two Principal Components, accounting for 57.5% of explained variance, apparently revealed that Treatment calves may exhibit greater expression of the relaxation and disinterest, whereas at the same time being less tense, sociable and friendly. In conclusion, the study reaffirmed the association between the EPHAI and the reduction of calves' stress and fear towards humans, as proved by the lower avoidance distances and higher CET scores. On the other hand, QBA demonstrated that calves who received EPHAI were less interactive and sociable with other animals, in favor of an improved relationship with humans. Hence, this study also showed that Flight Reaction tests and QBA are not interchangeable, but complementary methods of animals’ assessment.