Influence of guanidination on apparent ileal digestibility of amino acids in pigs fed diets with soybean meal, rapeseed meal or peas as a protein source

The objective of this study was to determine the effect of guanidination, the conversion of dietary lysine to homoarginine, on the apparent ileal digestibilities (AID) of amino acids (AA) from 3 protein sources in diets for pigs. Six barrows, initial body weight of 18±1.5 kg, fitted with a simple T-cannula at the distal ileum, were fed one of three corn starch-based diets that contained 18% crude protein (CP) from soybean meal, rapeseed meal or peas for an experimental period of 10 d according to a repeated 3×3 Latin square design. On d 9 of each experimental period, the pigs were fed one meal of the guanidinated test meals, which corresponded to their respective diets. In the test meals, 50% of the protein source in each diet was replaced, on an equal weight basis, with a guanidinated source. Guanidination increased the content of CP by 190, 116 and 28 g kg for soybean meal, rapeseed meal and peas, respectively. With the exception of lysine, the AID of CP and AAwere 2.2 to 8.2 percentage units (pu) higher in the test meal than in the soybean meal diet. Other than arginine and isoleucine, the differences were significant (Pb0.05) for all indispensable AA. With the exception of lysine, the AID of CP and AAwere 3.8 to 11.9 pu higher in the test meal than in the diet with peas. The differences were significant (Pb0.05) for all indispensable AA. Other than lysine, glycine and proline, the AID of CP and AAwere slightly higher, 0.1 to 4.3 pu, in the test meal than in the rapeseed meal diet. Of the indispensable AA, the differences were significant (Pb0.05) for arginine, leucine and phenylalanine. The AID of lysine was 10.9 pu lower (Pb0.05) in the test meal than in the rapeseed meal diet, 61.5 vs. 72.4%, indicating that guanidination of rapeseed meal was not uniform and random. The increase in the AID of CP and AA after guanidination may result from solubilisation of protein and degradation of antinutritional factors such as fiber, trypsin inhibitors and tannins. © 2007 Elsevier B.V. All rights reserved.