Reactivity is associated with greater subcutaneous fat deposition in young Canchim bulls

Abstract

The objective of this study was to evaluate the correlations between reactivity and carcass characteristics in young Canchim  bulls. Thirty intact male (594±23 days of age), were allocated to collective pens at the Central Bela Vista Technology Center (Botucatu, São Paulo). After 77 days, a reactivity score (REAT) was assigned, and carcass images were captured and read by ultrasound. These included ribeye area (REA), loin height/length ratio (RATIO), marbling (MAR), rump fat thickness (RFT), and backfat thickness (BFT). The Reactivity (REAT) was quantified using the REATest, a system employing an accelerometer mounted on the squeeze chute to capture vibrations resulting from animal movements. Following this, Spearman's correlation analyses were conducted to determine the existing relationship between REAT and carcass characteristics. Results indicate that more reactive animals exhibited greater subcutaneous fat thickness, with significant positive correlations between REAT and Backfat Thickness (BFT) (rho = 0.41, p < 0.05) and Rump Fat Thickness (RFT) (rho = 0.51, p < 0.05). This pattern may be linked to increased activation of the hypothalamic-pituitary-adrenal axis and subsequent elevation of cortisol, a hormone that, in chronic stress situations, favors body fat accumulation. Furthermore, reactive animals tend to show lower feed efficiency and alterations in energy metabolism. The results demonstrate that reactive animals developed increased subcutaneous fat thickness, with significant positive correlations observed between REAT and Backfat Thickness (BFT) (rho = 0.41, p < 0.05) and Rump Fat Thickness (RFT) (rho = 0.51, p < 0.05). This phenomenon may be linked to a more activated hypothalamic-pituitary-adrenal axis and consequently higher cortisol, which facilitates body fat accumulation under chronic stress. Although most other carcass characteristics showed only weak, non-significant correlations. This highlights a crucial interaction between behavior and energy metabolism in young cattle, underscoring the importance of considering temperament in performance evaluation and carcass finishing strategies.