Dietary inclusion of phytase and stimbiotic decreases mortality and lameness in a wire ramp challenge model in broilers

Abstract

ABSTRACT Lameness due to bacterial chondronecrosis with osteomyelitis (BCO) is an infection of weak bone by opportunistic bacteria that infiltrate the circulation as a result of immune suppression or gastrointestinal deterioration. One mitigating strategy is the dietary inclusion of products to support overall broiler robustness and bone health. To test the ability of phytase and stimbiotic supplements to alleviate lameness, broilers were reared for 56 days on either litter flooring or wire ramps to induce BCO and fed one of 6 diets: positive control (PC); negative control (NC, Ca and P deficient); PC plus stimbiotic; PC plus stimbiotic and phytase; NC plus phytase; NC plus stimbiotic and phytase. Stimbiotic was added at 100 g/tonne, and phytase at 3000 FTU/kg. Birds were scored for BCO on d56, or when culled for lameness. All-cause mortality was higher on ramp as compared to litter, regardless of treatment. Lameness was significantly induced by wire ramps, with the greatest incidence in the NC diet. Importantly, the addition of stimbiotic and phytase to the NC diet reduced lameness by ∼50%. Femur BCO scores were similarly reduced, with ∼60% of femurs scored ≥1 in the NC group compared to 30–37% in stimbiotic and phytase supplemented groups, indicating that these supplements can impact the onset/progression of lameness in poultry. There was no correlation between plasma and bone inositol levels; however, wire flooring reduced bone inositol, regardless of diet. Additionally, blood pH was greater and circulating PCO2, HCO3, BE, TCO2, K, haematocrit, and haemoglobin were lower on ramp compared to litter flooring. RESEARCH HIGHLIGHTS Wire ramp model reproducibly induced lameness/BCO in broilers. Treatments did not affect growth, but phytase with stimbiotic significantly reduced BCO. Phytase increased circulating inositol, and wire flooring decreased bone inositol.