The effects of dietary probiotic inclusion on skeletal health of poultry and its possible mechanisms

Probiotics are live microorganisms which may confer health benefits on the host when administered in appropriate amounts. Numerous studies have shown that probiotics improve bone health in humans and rodents with less information available on the skeletal health of avians given probiotics. The objective of this study was to determine the effects of probiotic supplementation on bone health of egg-laying and meat-type chickens. Dietary supplementation of a multi-species based probiotic reduced the percentage of shell-less eggs beginning at 4 wk following treatment and increased tibial and femoral bone mineral density in egg-laying hens at 7 wk post-treatment. Similarly, bone mineralization accrual of the tibia and femur was improved in broilers subjected to daily cycling heating episodes fed the same probiotic for 6 wk. Broilers consuming the probiotic also had a lower incidence of lameness as characterized by an improved gait score and longer latency to lie. The effects of a single-species based probiotic fed to broilers beginning at 1 d of age on bone health were investigated. Bone mineral densities of the tibia and femur were increased at 43 d of age. Concomitantly, serum calcium concentrations were increased at 14 d of age, serotonin levels were up-regulated in the raphe nuclei, and the catecholamine concentrations of NE and DA were down-regulated in the hypothalamus at 43 d of age. With the exception of bone mineral density, the bone health of probiotic-fed broilers was maintained under elevated temperature as indicated by larger bones and higher bone mineral content of the tibia and femur at 43 d of age accompanied by reduced plasma concentrations of TNF-α, a pro-inflammatory cytokine. Dietary inclusion of probiotics is a useful strategy for improving skeletal health in chickens under both normal and elevated ambient temperature. Probiotics enhance intestinal absorption of nutrients like calcium and may reduce sympathetic activity, thus improving mineralization of bone. Under the condition of daily cycling heating episodes, probiotics increased bone growth and bone size of broilers perhaps via inhibition of bone resorption resulting from the down-regulation of TNF-α, thereby reducing systemic inflammation