Effects of isoquinoline alkaloids on apparent ileal digestibility of amino acids, crude protein, starch, and acid hydrolyzed ether extract and apparent total tract digestibility of energy and crude protein by growing and finishing pigs fed corn-soybean meal diets

Two experiments were conducted to test the hypotheses that a preparation of isoquinoline alkaloids (IQ) obtained from Macleaya cordata included in corn-soybean meal (SBM) diets increases apparent ileal digestibility (AID) of nutrients, increases apparent total tract digestibility (ATTD) of gross energy (GE) and crude protein (CP) and increases plasma amino acids (AA) and protein when fed to growing or finishing pigs. Experiment 1 utilized 12 barrows (body weight: 27.1 ± 2.10 kg) equipped with a T-cannula in the distal ileum, which were allotted to 4 treatments and 4 periods for 12 replicates per treatment. Treatments included a corn-SBM basal diet and three diets formulated by adding 40, 80, or 160 mg/kg of IQ to the basal diet. In experiment 2, twelve T-cannulated barrows (BW: 77.2 ± 6.23 kg) were allotted to the same treatments as in experiment 1, but diets were fed for 3 periods for a total of 9 replicate pigs per treatment. Each period had a 10-day adaptation period, followed by fecal sample collection on day 11 and 12, and ileal digesta collection on day 13 and 14. Results indicated that AID of some AA increased when IQ was included at 40 or 160 mg/kg in experiment 1, but a reduction (P < 0.05) in the AID of acid-hydrolyzed ether extract (AEE) and starch was observed at 80 mg/kg IQ. Including 80 mg/kg IQ to diets in experiment 2 increased the AID of CP, whereas 40 mg/kg IQ resulted in an increased (P < 0.05) AID of His, Met, and Pro, and a tendency (P < 0.10) for an increase in AID of Ile, Leu, Lys, Cys, Gly, and Tyr. The ATTD of CP was also increased (P < 0.05) if the diet containing 80 mg/kg IQ was fed in experiment 2. Albumin was reduced (P < 0.05) in plasma of finishing pigs fed 40 mg/kg IQ in experiment 2. Including 80 mg/kg IQ in a diet for growing pigs increased (P < 0.05) plasma Lys, and adding 80 or 160 mg/kg increased (P < 0.05) plasma Asp, but a reduction (P < 0.05) in some plasma AA as 160 mg/kg IQ was added to diets for finishing pigs was observed. In conclusion, IQ may be added to diets for growing and finishing pigs to increase the AID of AA and CP, with optimal results observed at inclusion levels of between 40 and 80 mg/kg IQ.