Positive or negative emotion induced by feeding success or failure can affect behaviors, heart rate and immunity of suckling calves.

This study investigated behavioral and physiological responses of suckling calves to either positive or negative situations. Twelve healthy female suckling Holstein calves at approximately 30 days of age were randomly selected and allocated to two groups: a) a positive situation (POS) group that received a feed reward and b) a negative situation (NEG) group that experienced food frustration. Behavior, heart rate (HR), and immune parameters were measured during the emotion-inducing periods and analyzed via ANOVA. The results indicated that the POS calves showed significantly increased locomotive play but decreased self-grooming, head shaking, and tongue-rolling behaviors as compared to the NEG counterparts (p < .05). The NEG calves had the highest HR (p < .01) after negative emotion induction. Salivary cortisol (S-CORT) level significantly increased following both positive and negative emotional induction (p < .05). In humoral immunity, serum concentrations of IgA were not significantly affected by either the positive or negative situation (p > .05), but the salivary SIgA level of the POS calves was higher than that of the NEG group (p < .01). Serum IL-2 and IL-3 levels in the POS calves were significantly higher than those of the NEG group (p < .01). However, the serum TNF-α level in the POS group was significantly lower than in the NEG group (p < .05). The results suggest that hunger satiation or food frustration may induce different behavioral and physiological responses in suckling calves, presenting an interesting set of reactions appropriate in response to the emotional situations elicited by this short-term stimulus.