Unveiling factors prompting physical engagement with human handlers in trained and untrained Holstein dairy heifers

ABSTRACT Fearful and agitated animals represent a risk in cattle farming, while training techniques have been reported to boost heifers’ confidence making their handling easier and reducing stress. We investigated the impact of training aimed at desensitising animals to handling on heifers’ behaviour, focusing on physical interactions with human handlers, such as rubbing, licking and pushing, which can be considered undesirable by farmers. Sixty Holstein heifers of two age classes and three categories of Responsiveness to Humans (RTH), assessed through an Avoidance Distance Test (ADT) were studied. Half of the animals were trained and half not. Faecal cortisol metabolites, heart rate parameters and behaviour during handling were determined and a Physical Animal-Human Contact Behaviour Test (PAHCBT) was performed to detect behaviours which involve physical contact. The number of approaches and Physical Animal- Human Contact Behaviour events (PACHB) were recorded. During the PAHCBT (11 replicates), individual heifers exhibited an average number of 4.3 approaches (range: 0–18) and 8.2 PAHCBs (0–75). Older class heifers exhibited a higher number of approaches (5.31 vs. 3.22, p=0.04). 13 heifers (21.7%) were considered highly physical contact driven (PCDs) showing more than 5 PAHCBs and more than 1 PAHCB per approach. Among predictors, training (p=0.031) and high initial ADT values (p=0.078) acted as a protective factor against being PCDs, whereas the presence of kicking during handling was a proxy for PCDs (p=0.034). The results show that training, besides facilitating handling, helps preventing heifers from being considered PCDs.