Ileal amino acid digestibility and reactive lysine content in peas (Pisum sativum) fed to growing pigs

Four barrows with an average initial BW of 24.4 ± 1.8 kg and fitted with a simple T-cannula at the distal ileum were used to determine the coefficients of ileal apparent (CIAD), standardized (CISD) and true (CITD) digestibility of crude protein (CP) and amino acids (AA) in four pea-based diets according to 4 × 4 Latin square design. Coefficients of ileal true digestibility of reactive lysine (CITDrlys) and digestible reactive lysine content (Drlys) were also determined. The CITD of lysine, CITDrlys, and Drlys were determined using the homoarginine (HA) method. The pigs were fed four pea-based diets formulated to contain 145 g CP/kg DM from three pea cultivars; Profi, Swing, Croma and a pea mixture of AC Melfort, CDC Mozart, and Eclipse. The diets were formulated to contain either of the three pea cultivars or pea mixture as the sole source of AA. Chromic oxide and titanium oxide (4 g/kg) were included as indigestible markers to determine CIAD of nutrients and homoarginine, respectively. Each experimental period lasted 8 days and ileal digesta were collected continuously for 24-h on day 6 for determining CIAD. On the morning of day 8, pigs were fed a diet in which half of the pea was replaced with the respective guanidinated pea to determine CITD of lysine. Part of the digesta collected on day 6 was guanidinated for determining CITDrlys and Drlys. The CIAD, CISD and CITD of CP were similar (P>0.05) among the diets. The CIAD of indispensable AA, except phenylalanine were different (P<0.05) among the diets. The CITD of AA other than lysine were estimated using observed endogenous lysine flows and their published ratios relative to lysine. The CISD and CITD of AA were similar (P>0.05) among the diets. The Drlys were different (P<0.05) among the diets. The values of CITDrlys (range: 0.964–0.982) were similar (P>0.05) to the CITD of lysine (range: 0.981–0.993) within and among the diets. The CIAD of AA obtained in this study were more variable compared with CISD and CITD. The results also indicate that the CITDrlys and CITD of lysine provide close values, validating suitability of either method in determining true ileal digestibility of lysine.