Acute Physiological Response Variability in Lidia Bulls Following Roping Bull Celebrations: Effects of Age, Previous...

Roping Bull celebrations involve prolonged physical activity in Lidia cattle and are associated with marked acute hematological, biochemical, and endocrine responses. Previous research has characterized these physiological changes, but less is known about the factors that may explain inter-individual variability in their magnitude. The present study evaluated whether age, previous participation history, and sampling period influence the PRE-POST physiological response of Lidia bulls. A total of 101 adult Lidia bulls were evaluated immediately before and after participation in a standardized 45 min Roping Bull event. Fifty-three bulls (52.4%) had also been included in a previous study in which the physiological variables evaluated in the present investigation had been reported. Linear mixed-effects models were fitted separately for each biomarker, with Time (PRE vs. POST), age group (AGE), previous participation history (RACES), and sampling period (MOMENT) included as fixed effects, together with prespecified interactions with Time. Individual bull was included as a random intercept to account for the repeated PRE-POST measurements. Participation was associated with significant changes in several hematological, biochemical, and endocrine biomarkers, particularly lactate, creatine kinase, lactate dehydrogenase, leukocyte variables, cortisol, and ACTH. In contrast, AGE, RACES, and MOMENT showed comparatively limited influence on the magnitude of most PRE-POST responses. Selected Time × factor interactions indicated some biomarker-specific inter-individual variability, although these effects were less consistent than the overall Time effect. The present study extends the previous physiological characterization of Lidia bulls by identifying potential factors associated with variability in the acute PRE-POST response. Overall, the physiological response was relatively consistent across age and previous participation categories, although selected interactions indicate that individual and event-related factors may contribute to variation in specific biomarkers. These physiological measurements should not be interpreted in isolation as direct evidence of either preserved or compromised animal welfare.