1. The essentiality of
silicon for skeletal development has been established, but the adequacy of bioavailable
silicon supply in broiler diets has not been considered for 30 years, despite average daily
weight gain of birds increasing by almost a third over that time. Therefore, two studies were undertaken to investigate whether modern strains of broiler chicken benefit from diet supplementation with bioavailable
silica. 2. Trial 1 was a 2x2x2 factorial study where six replicate pens of seven chicks were fed one of the eight freshly prepared diets from hatch to 21 days of age, with bodyweight gain and feed intake recorded weekly. Diets combined the following factors:
silicon supplement fed at 0 ppm or 1000 ppm,
phytase levels of either 0 FTU/kg or 1500 FTU/kg and either 0.6% or 0.7% Ca. Tibia were analysed for bone breaking strength, extent of tibial
dyschondroplasia and feet measured for
bone ash and pododermatitis score. 3. Trial 2 used a 0.7% Ca with 1500 FTU
phytase diet as the control and compared this with the same diet containing either 1000 ppm
silicon (MONO-Si) freshly added each week or 1000 ppm
silicon added in a single, advance-prepared batch per feeding phase. Each diet was fed to nine pens of seven birds from 0 to 35 d with feed consumption and weight recorded weekly. Two birds per pen were euthanised on d 14, 21 and 35 and tibias collected for measurement of bone breaking strength, ash and
mineral content. Serum was collected for Si content. 4. Univariate analysis of means from each trial showed that
silica supplementation improved bird
weight gain over the starter phase, though there was no effect on feed conversion. 5. Bone strength improved with added
silica in both studies, without affecting bone mineral content; indicating that modern strains of broiler may require dietary supplementation with bioavailable
silicon.