The Optimal Supplementation of Fermented Product Produced by Bacillus subtilis Strain LYS1 with High Surfactin Yield for Improving Growth Performance, Intestinal Villi Morphology, and Tibial Bone Strength in Broilers.

This study aimed to investigate the physiochemical characterizations of the fermented product (FP) produced by the high-yield surfactin strain Bacillus subtilis LYS1 (LYS1), as well as its effects on growth performance, carcass traits, intestinal morphology, tibial bone characteristics, and clinical blood biochemistry in broilers. Accordingly, the optimal supplementation of FP for improving growth performance, intestinal villi development, and tibial bone strength in broilers was elucidated using a broken-line quadratic (BLQ) ascending model. Three hundred and sixty 0-day-old Ross 308 broiler chicks, with equal numbers of both sexes, were randomly assigned to dietary supplementation of 2.5% fish meal or 0, 1, 1.5, 2, or 2.5% FP. Each treatment had six replicates, and the experimental period was 5 wk. The LYS1 count, surfactin content, and surfactin composition of the FP were 9.1 log CFU/g, 11.23 mg/g, and C 12 to C 18 , respectively. The FP-supplemented groups improved feed intake, weight gain (WG), and production efficiency factor at 0 to 5 weeks old ( p < 0.05) compared with the 0% group. The villus height/crypt depth (V/C) in the jejunum and ileum of the FP-supplemented groups was higher than in the 0% group ( p < 0.05). The tibiotarsal index, Ca, and P in the tibia showed a linear effect with increased FP supplementation ( p < 0.05). Moreover, the tibiotarsus weight/length index (TWLI) showed a quadratic effect with increased FP supplementation ( p < 0.05). The optimal supplementation of FP for WG, V/C in the jejunum and ileum, and TWLI was 1.8, 1.9, and 1.6%, respectively. In conclusion, dietary supplementation with 1 to 2.5% LYS1 FP in broilers can improve their growth performance and the development of intestinal villi. Moreover, 1.9% is the optimal supplementation of LYS1 FP in the diet, based on the fitting results obtained with the BLQ model.