Enhancing Production, Reproduction, and Health in Laying Quails Through Probiotic Supplementation ( <i>Bacillus toyonensis</i> and <i>Bifidobacterium bifidum</i> ): Effects on Performance, Physiological Parameters, and Gut Microbiota

Abstract The objectives of this investigation were to evaluate the influence of dietary supplementation with different levels of Bacillus toyonensis ATCC 55050 (BT), Bifidobacterium bifidum ATCC 29521 (BB), and a combination of half the dose of BT and BB on the productive performance, carcass characteristics, physiological parameters, and gut microbiota of laying Japanese quails ( Coturnix coturnix japonica ). A total of 144 laying quail chicks (56 days old, Japanese quail) were assigned to four experimental groups in a fully randomized design experiment for 12 weeks. Twelve replicates, each consisting of two female and one male bird, were created for each group. The control group of birds received a corn-soybean basal diet from 56 to 140 days of the trial. In contrast, the groups receiving probiotics were given the same control diet supplemented with 0.1% Bacillus toyonensis (BT), 0.1% Bifidobacterium bifidum (BB), or a combination of 0.05% Bacillus toyonensis plus 0.05% Bifidobacterium bifidum (BT+BB). There was a significant enhancement (P&lt;0.05) in performance traits during different weeks of age as a result of the treatments with Bacillus toyonensis (BT), Bifidobacterium bifidum (BB), and the combination of both (BT+BB), except for live body weight. The results demonstrated a significant influence (P&lt;0.05) of various probiotic treatments on fertility (Fer) and hatchability (Ha) percentages. BT+BB showed the highest fertility (98.57%) and total embryonic mortality (15.95%) compared to the other treatments. Also, the digestive enzymes activity was significantly (P&lt;0.05) enhanced by BT and BT+BB treatments; besides, the BT+BB treatment showed higher levels of all antioxidant traits. In summary, the addition of Bacillus toyonensis (BT), Bifidobacterium bifidum (BB), and their combination (BT+BB) to the diet of laying quails significantly improved performance, blood traits, and decreased total bacterial counts, coliform levels, total fungi, and the cecal microflora.