Effect of including purified jack bean lectin in casein or hydrolysed casein-based diets on apparent and true ileal amino acid digestibility in the growing pig

The effect of including purified jack bean lectin (concanavalin A) in the diet of grower pigs on endogenous ileal nitrogen (N) and amino acid (AA) losses, and apparent and true ileal AA digestibility was investigated in a study with four growing pigs ( average initial live weight (LW) 25 kg) fitted with simple T-cannulae at the terminal ileum. Both the homo- arginine (HA) method and peptide-alimentation method were used to estimate endogenous gut AA losses. The animals were offered four diets : (1) an enzymatically hydrolysed casein (EHC) containing diet, (2) an EHC containing diet supplemented with 266 mg/kg jack bean lectin, (3) a normal casein (NC) containing diet, and (4) a NC containing diet supplemented with 266 mg/kg lectin. For the estimation of ileal endogenous AA flows in pigs given NC diets, a subsample of NC was guanidinated to convert lysine to HA. The experiment was conducted using a 4x4 Latin-square design. In each experimental period, pigs were adjusted to the experimental diets for 5 days. On day 6, ileal digesta was collected continuously for 24 h for determination of apparent ileal digestibility. At 08: 30 h of day 8 the HA NC diets were offered to pigs on NC treatments and ileal digesta were again collected for 24 h from all pigs. There were no interactive effects of casein type and added dietary lectin on apparent and true ileal AA digestibility and endogenous ileal AA flows (P>0.05). The addition of lectin to the diet did not influence (P>0.05) the apparent ileal digestibility of dry matter (DM), crude protein (CP) and AA. Casein type did not affect ileal DM digestibility (P>0.05). Pigs given the NC-based diets had higher (P<0.05) apparent ileal AA digestibility than pigs given the EHC-based diets. Addition of lectin to the diet did not influence (P>0.05) endogenous ileal CP and AA flows. Endogenous ileal AA losses were generally higher (P<0.05) in pigs given EHC diets than in pigs given NC diets. Neither casein type nor diet lectin level influenced (P>0.05) the true ileal digestibility of CP and AA; values ranged for most AA between 0.98 and 1.00. These data suggest that including purified jack bean lectin at the level of 266 mg/kg in a casein-based diet did not influence the ileal endogenous CP and AA flow, nor the apparent and the true ileal digestibility of CP and AA, in growing pigs between 25 and 50 kg LW. Compared with the HA method, the peptide-alimentation method yielded higher estimates of ileal endogenous CP and AA acid losses in pigs given casein-based diets, although these two methods yielded similar estimates of true ileal AA and CP digestibility.