Comparing the effect of selenium yeasts, betaine, and capsaicin on heat stress response in fattening bulls.

Prolonged high temperatures cause heat stress in fattened cattle, negatively affecting growth and health. This study evaluated dietary supplements in Limousin bulls under mild heat stress (THI = 75.01 ± 4.13). Forty-eight bulls were divided into four groups, receiving either a standard TMR or TMR supplemented with selenium yeast (YSE), betaine (BET), or capsaicin (CAP) for 60 days. Results showed all additives improved daily gains (p ≤ 0.05). Redox markers varied; total antioxidant capacity (TAC) was highest in the control group, while BET had the lowest. The BET also showed the highest GPx activity (p ≤ 0.01). Heat shock protein (HSP70) concentrations were elevated in YSE and BET compared to CON and CAP. Lymphocyte content decreased in YSE and BET. The CAP reduced calcium and creatinine levels (p ≤ 0.05). Feeding behavior differed, with CON and CAP having longer feeding times, while YSE and BET spent more time resting (p ≤ 0.01). The BET and YSE provided the greatest economic benefits, while the higher cost of CAP reduced its economic advantage despite improved production performance. In conclusion, all supplemented additives were effective under mild heat stress. The factor limiting the practical use of capsaicin compared to other additives may be its price. Further research is needed on the interaction of these supplements for practical application.