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A total of seven [(Yorkshire-Landrace) x Duroc] ileal-cannulated weanling pigs (mean initial body weight 9.50 (SD 0.42) kg) were fed a casein–maize starch-based diet with PA (as sodium phytate) at 0, 5, 10 or 20 g/kg in 4 x 4 Latin square design with three added columns to give seven observations per treatment. The basal diet was formulated to meet energy and AA requirements for piglets. The diets included a control diet either unsupplemented or supplemented with 5, 10 or 20 g/kg PA (as sodium phytate). Two sets of four diets were prepared: one set of diets contained chromic oxide (3 g/kg) as an indigestible marker and intact casein; whereas the other set contained titanium oxide (3 g/kg) as an indigestible marker and 50% of the dietary casein was guanidinated to convert lysine to homoarginine for determination of endogenous AA flow at the terminal ileum by the homoarginine method. The respective digestibility and endogenous lysine loss were determined by indicator and homoarginine methods.
The apparent ileal digestibility (AID) of Na, K and P was linearly and quadratically reduced (P<0.05) by increased dietary PA concentration, whereas that of Ca and Mg was only linearly reduced (P<005) by the dietary PA. The AID values for Mg and Na were negative (20.03 and 20.18, respectively) when PA was supplemented at 20 g/kg. The AID of isoleucine, leucine and valine responded quadratically to dietary PA concentration, though the differences between the AID values of the AA due to change in dietary PA concentration were marginal (at most by 1.8 percentage units). Furthermore, dietary PA did not affect (P>0•05) endogenous AA losses.
The results suggest that PA has limited effect on the digestibility and endogenous losses of AA in piglets, but can reduce AID of Mg and Na partly by increasing endogenous losses of these minerals as evidenced by their negative AID values.
TA Woyengo, AJ Cowieson, O Adeola and CM Nyachoti. 2009. British Journal of Nutrition. 102: 428-432.
