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Broiler diets free of feed phosphates
Many studies aimed at reducing inorganic phosphate in phytase supplemented diets, but full substitution of iP by phytase is a more recent objective. It is favoured by continuous advancements in enzyme science and technology. Full replacement of iP is especially challenging in young birds with high rates of growth and bone mineralisation. Two studies measured the effect of high dosed-phytase on broilers during all growth phases (4 feeds, 1-42d) after withdrawal of phosphate supplementation. A negative control was avoided to prevent severe P deficiency and bone abnormalities. The positive control with MCP met phosphorous requirements defined by the genetic company. Treatments groups were : IPF1 with 1000 FTU/kg and reduced Ca; IPF2 with same phytase dosage and reduced Ca/Na, amino acids (dig AA) and ME; IPF3 with 3000 FTU/kg in starter phase, 2000 FTU/kg in grower phase, and 1000 FTU/kg in finisher 1 and 2 phases, with reduced Ca.
All iP free treatments were able to maintain the same levels of growth performance and bone ash. They measured a positive impact on bone breaking strength (https://animine.eu/did-you-know-11/#main). Their economic benefit, measured by feed cost/kg BW, was improved at 2019 market ingredient prices : cost savings were largely explained by the use of cheaper, phytate-rich ingredients such as rapeseed meal, rice and wheat bran.
Bone breaking strength (42 days)
Successful complete replacement of iP was possible in the conditions of these studies : a high phytate P complex diet without P-rich animal-derived ingredients, the addition of oat hulls, optimised calcium level, and tiered-dosing regimen by phase.
Phosphate-free diets for monogastric animals are very close to becoming reality. Based on current usage levels, it is estimated that total removal of inorganic phosphate from broiler production could reduce usage of MCP and its equivalent in broiler feeds by 1 million tons per year.
Source: Marchal et al, A novel consensus bacterial 6-phytase variant completely replaced inorganic phosphate in broiler diets, maintaining growth performance and bone quality: data from two independent trials, Poult Sci 2021 Vol. 100:3 , 100962