Standardized and true ileal amino acid digestibilities in field pea and pea protein isolate fed to growing pigs

• We determined standardized and true ileal amino acid digestibilities in field pea and pea protein isolate fed to growing pigs.
• The results show that processing of field pea to produce pea protein isolate improved apparent AID of AA.
• Processing of field pea to produce pea protein isolate reduced ileal endogenous AA losses.
• However, the processing of field pea to produce pea protein isolate had limited effect on TID of AA.

Four ileal-cannulated Cotswold barrows (50.41 ± 5.05 kg body weight) were used to determine apparent (AID), standardized (SID) and true (TID) ileal digestibility of amino acids (AA) in field pea and pea protein isolate (PPI) processed from the same batch of the whole field pea. Pigs were allotted to 2 experimental diets in a simple cross-over design. Diets contained either field pea or PPI as the sole source of protein and were formulated to contain 155 g/kg CP. The AID of nutrients was determined by the indicator method. The SID of AA was calculated using published values for basal endogenous AA losses obtained from our laboratory. The total endogenous flow of lysine and the TID of lysine were determined by the homoarginine method. The TID of AA other than lysine were estimated using their published ratios in endogenous protein relative to lysine. The AID coefficient of CP (0.88 vs. 0.80), Ile (0.91 vs. 0.79), leucine (0.92 vs. 0.81), lysine (0.93 vs. 0.84), phenylalanine (0.92 vs. 0.84) and valine (0.89 vs. 0.76) were greater (P < 0.05) in PPI than in field pea. The total (363 vs. 2167 mg/kg [dry matter intake (DMI)] and endogenous (312 vs. 1777 mg/kg DMI) lysine flow were lower (P < 0.05) in PPI compared with field pea. Likewise, field pea had greater (P < 0.05) total and endogenous nitrogen (N) and AA (other than lysine) flow compared with PPI. The SID of indispensable AA for PPI was greater (P < 0.05) than that for field pea. However, PPI and field pea were similar in the TID of all indispensable amino acid except lysine whose TID coefficient in PPI (0.99) was greater (P < 0.05) than for field pea (0.94). In conclusion, the results indicate that processing of field pea to produce pea protein isolate improved apparent AID of AA and reduced ileal endogenous AA losses. However, the processing of field pea to produce pea protein isolate had limited effect on TID of AA.