Effect of tannins in sorghum on amino acid ileal digestibility and on trypsin (EC2.4.21.4) and chymotrypsin (EC2.4.21.1) activity of growing pigs

Two experiments were conducted to evaluate the effect of tannin levels in sorghum on coefficient of apparent ileal digestibility (CAID), coefficient of standardised ileal digestibility (CSID) of amino acids, and total and specific activity (TA, SA) of trypsin and chymotrypsin of growing pigs. In the first experiment, 24 castrates (60:L 5 kg) were fitted with a simple T cannula to evaluate four different sorghum samples (I, II, III, and IV) with different tannin levels (1.4, 4.6, 9.8 and 10.0 g kg(-1)). At the end of the trial, pigs were slaughtered to obtain samples of pancreas and intestinal digesta. Data were analysed as a randomized block design. The highest CAID (P < 0.05) was observed on sorghum I and the lowest on sorghum II. Leucine and glutamic acid were the most digestible amino acids in the four samples of sorghum, with glycine, lysine, threonine and cysteine being the least digestible. As tannin levels increased, proline CAID decreased (P<0.05). CSID of amino acids in sorghum I was higher (P<0.05) than on sorghum II, except for proline. Similarly, the CSID for isoleucine, lysine, threonine, valine, alanine and aspartic acid was similar among sorghums I, III and IV. Tannin content did not affect pancreas weight, protein content, or TA and SA of trypsin and chymotrypsin on pancreatic tissue. However, in the digesta of duodenum, trypsin TA was increased (P < 0.05) by 6.7% in the two treatments with the highest tannin content. In the second experiment, 32 castrates (53 +/- 7 kg) were fitted with a simple T cannula to evaluate eight different hybrids of sorghum: four Pioneer (8172, 8428, 8443, and 8641), and four Dekalb (D-45, D-65, D-68, and D-69). High-tannin sorghums (8172 and 8428) had the lowest (P<0.05) CAID for arginine, glycine, and proline. Furthermore, sorghum 8428 had the lowest (P<0.05) CAID for lysine (0.339). The CAID for proline was negative (-0.110) for sorghum 8428 and extremely low (0.031) in sorghum 8172. These sorghums had a low (P < 0.05) CSID for arginine, histidine, and proline. In sorghums with a high content of tannins the CSID for proline and glycine was very low. Lysine CSID was lower (P<0.05) in sorghum 8428, when compared to the others samples of sorghums. In conclusion, tannin levels up to 1.05% are not the main depressors of the CAID and CSID of amino acids in the sorghum grain; however, tannins have a clear negative effect on CAID and CSID in sorghum with high levels (4% or more) of tannin. (C) 2004 Elsevier B.V. All rights reserved.