The standard protocol of the World’s
Poultry Science Association recommends using pc P
digestibility for raw material evaluation (WPSA, 2013).
Regardless of approach, P sources must be supplemented
to a basal diet for determination of P availability,
and the results of a P availability study may depend on
the type of basal diet used. For example, semi-synthetic
diets are often selected in digestibility experiments
for poultry, but this choice of diet raises the question
of whether results obtained from semi-synthetic diets
are valid for the phytate-containing diets used in the
practical feeding of broilers. Semi-synthetic diets are
also less palatable to poultry than practical-type diets
(Sullivan, 1999). Further, various practical-type
diets differ considerably in composition and how this
variability can affect the availability of added mineral
P sources is unclear. Differences in intrinsic phytase
activity, content of InsP, or nonstarch polysaccharide
content between corn and wheat, for example, could
affect the availability of mineral P sources included in
these diets (Shastak and Rodehutscord, 2013). The few
studies available to date that have compared different
basal diet types in evaluation of mineral P sources used
bone ash or BW gain as response criteria and are out-
The standard protocol of the World’sPoultry Science Association recommends using pc Pdigestibility for raw material evaluation (WPSA, 2013).Regardless of approach, P sources must be supplementedto a basal diet for determination of P availability,and the results of a P availability study may depend onthe type of basal diet used. For example, semi-syntheticdiets are often selected in digestibility experimentsfor poultry, but this choice of diet raises the questionof whether results obtained from semi-synthetic dietsare valid for the phytate-containing diets used in thepractical feeding of broilers. Semi-synthetic diets arealso less palatable to poultry than practical-type diets(Sullivan, 1999). Further, various practical-typediets differ considerably in composition and how thisvariability can affect the availability of added mineralP sources is unclear. Differences in intrinsic phytaseactivity, content of InsP, or nonstarch polysaccharidecontent between corn and wheat, for example, couldaffect the availability of mineral P sources included inthese diets (Shastak and Rodehutscord, 2013). The fewstudies available to date that have compared differentbasal diet types in evaluation of mineral P sources usedbone ash or BW gain as response criteria and are out-
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