Effects of kafirins and tannins concentrations in sorghum on the ileal digestibility of amino acids and starch, and on the glucose and plasma urea nitrogen levels in growing pigs

Two experiments were conducted to determine the effects of sorghum kafirins and tannins concentrations on the apparent and standardized ileal digestibility (AID and SID, respectively) of protein, amino acids, and starch; as well as on the glucose and plasma urea nitrogen (PUN) response in growing pigs. Two hybrids of sorghum, 82G93 and 81G67 that were low and high in tannins (LT and HT), respectively, were evaluated. Each hybrid had low or high levels of kafirins (LK and HK, respectively). Pigs were fed 4 experimental diets that were formulated with sorghum as the sole source of CP and AAs: LT-LK, LT-HK, HT-LK, and HT-HK. In experiment 1, ileal cannulation was performed in 4 pigs weighing 25 ± 0.60 kg to determine protein, amino acids, and starch digestibility. In experiment 2, internal jugular venous catheterization was performed in 4 pigs weighing 26 ± 0.52 kg to determine glucose and PUN response. Experiment 1 results revealed that starch digestibility was not affected (P > 0.05) by kafirins neither tannins. Kafirins levels negatively affected (P < 0.05) the AID of glutamic acid and histidine; and tended to reduce (P < 0.10) alanine, aspartic acid, and valine AID. A higher level of tannins negatively affected (P < 0.001) the AID of dry matter, energy, lysine, (P < 0.01) cystine, histidine, methionine, (P < 0.05) crude protein, aspartic acid, leucine, and threonine. There was kafirins × tannin interaction effect which decreased (P < 0.05) the AID of glutamic acid and lysine; the AID of glycine and proline were negative in all diets. The SID of alanine, glutamic acid, histidine, and valine showed a tendency (P < 0.10) to be lower in high kafirins sorghums. Tannins level negatively affected the SID of (P < 0.001) lysine, (P < 0.01) cystine, histidine, (P < 0.05) protein, aspartic acid, leucine, methionine, serine, threonine, and valine digestibility. Experiment 2 results revealed that kafirins levels did not affect the glycemia until 300 min postprandial when a tendency (P = 0.08) to increase the glucose response was observed in pigs fed HK sorghums. Tannins level showed a tendency (P < 0.10) to decrease glycemia at 150 and 360 min postprandial. At 300 min postprandial HT sorghums diminished (P = 0.02) glycemia. The PUN level was not affected (P > 0.05) by kafirins but was reduced (P < 0.001) by the HT sorghums. The findings of the present study indicated that kafirins had a minimal but significant effect on the criteria studied; however, sorghum tannins reduced amino acid digestibility, glucose and PUN response in growing pigs.