Combined Bifidobacterium bifidum and Bacillus toyonensis supplementation in drinking water improves productive efficiency, physiological status, and meat quality in broiler chickens.

Developing combined, multistrain probiotic strategies in drinking water represents a promising approach to improve broiler productivity, health, and economic returns under intensive farming. This study evaluated the effects of supplementing broiler drinking water with Bifidobacterium bifidum (BB), Bacillus toyonensis (BT), or their combination on growth performance, physiological status, meat quality, and economic efficiency. A total of 320 one-day-old, unsexed IR broiler chicks were randomly allocated to four treatments with eight replicates of 10 birds each: an unsupplemented control, BB (0.5 g/L; 5 × 10⁸ cfu/L), BT (0.5 g/L; 5 × 10⁸ cfu/L), and BB+BT (1.0 g/L; 5 × 10⁸ cfu/L of each probiotic). Birds receiving probiotics exhibited improved growth performance compared with the control. The combined BB+BT treatment produced the greatest advancements in final body weight, feed conversion ratio, and European Production Efficiency Factor. Carcass yield was unaffected by treatments. However, probiotic supplementation improved meat proximate composition, oxidative stability, color characteristics, tenderness, and juiciness, without affecting muscle pH or water-holding capacity. Hematological indices, including hemoglobin concentration, red and white blood cell counts, and packed cell volume, were optimized by probiotic supplementation, whereas erythrocyte indices remained unchanged. The combined treatment also increased serum total protein, reduced circulating transaminases, lowered total cholesterol and low-density lipoprotein cholesterol, and enhanced immune and antioxidant status through higher immunoglobulins (G and M) and superoxide dismutase activity, together with lower malondialdehyde concentration. Despite the additional supplementation cost, the combined probiotic treatment generated the greatest economic return. Overall, combined supplementation with B. bifidum and B. toyonensis via drinking water was associated with improved productive performance, physiological status, and meat quality compared with individual supplementation or the control.