EFFECT OF CONFINEMENT STRESS ON PLASMA LEVELS OF PROTEINS, GLUCOSE, AND HEMATOLOGICAL INDEXES IN NILE TILAPIA (OREOCHROMIS NILOTICUS)

The present study investigated the effects of confinement on secondary biochemical and physiological stress responses in Nile tilapia (Oreochromis niloticus). Stress is a central issue in physiology due to its impact on animal health and life. In this study, 36 juvenile tilapia (n = 12/group) were divided into three groups: control (CT), confinement stress (EC), and confinement plus "aggression" stress (CA). The CT group was free from manipulation, while the EC group was confined for 30 minutes in a space representing 10% of the original tank volume. The CA group was confined under the same conditions and then subjected to the "mirror test" paradigm. This test is a stressor for the animal, as it simulates the presence of another fish through its reflection in the mirror, generally inducing stress by triggering aggressive-like behavior. After the experiments, blood was collected, and the following parameters were evaluated: ventilatory frequency (VF), blood glucose, hemoglobin, hematocrit, erythrocytes, hematimetric indices (VCM, HCM, and CHCM), and plasma proteins. Our results showed that only confinement combined with stress from the "mirror test" (CA group) significantly elevated FV and glucose levels compared to the CT group, and hemoglobin and plasma protein levels compared to the CT and EC groups (p < 0.05). These results suggest that confinement alone (for 30 minutes) is not sufficient to alter the biochemical and physiological parameters evaluated. Additionally, confinement in a restricted space may trigger an exaggerated biochemical and physiological response when the animal is subjected to another type of stressor. The study highlights the importance of strategies to mitigate the effects of stress, as it can cause various disorders that directly impact the animal's life.