Effects of a dietary synbiotic inclusion on bone health in broilers subjected to cyclic heat stress episodes

The objective of this study was to determine the effects of a dietary synbiotic inclusion on broiler bone health under daily cyclic heat stress. A total of 360 Ross 708 broilers were randomly assigned to 1 of 3 dietary treatments (8 replicates per treatment): a regular diet (control) and the regular diet mixed with a commercial synbiotic product at 0.5 (0.5X) or 1.0 (1.0X) g/kg. The synbiotic contains a prebiotic (fructooligosaccharides) and a probiotic mixture of 4 microbial strains (Enterococcus faecium, Pediococcus acidilactici, Bifidobacterium animalis, and Lactobacillus reuteri). Room temperature was gradually decreased from 34°C on d 1 by 0.5°C/d for the first 14 d; then a cyclic heat stress episode (32°C/9 h/d) was applied from d 15 to 42. Gait score assessment and the latency-to-lie test were conducted when broilers were 40 and 41 d of age, respectively. The tibia, femur, and humerus were collected for measuring bone parameters at 42 d of age. The data indicated that bone mineral density, bone mineral content, and bone area were higher and the level of gait score was lower in the 1.0X group (P = 0.05) but not in the 0.5X group (P > 0.05) compared to controls. The proportions of broilers showing signs of lameness were ranked 1.0X group (25%) < 0.5X group (45%) < control (54%). Compared to controls, broilers of 0.5X group stood longer (P = 0.03) during the latency-to-lie test. In conclusion, under the present conditions the synbiotic profoundly improves multiple indices of leg health of broilers subjected to the cyclic heat episodes, resulting in an improvement in walking ability.