Standardized ileal amino acid digestibilities and energy content of different sources of soybean meals in pigs

The use of apparent ileal digestibilities (AID) of crude protein (CP) and amino acids (AA) in diet formulation for pigs has been limited due to the considerable variation in AID among different samples of the same feedstuff (Mosenthin et al. 1997, Sauer et al. 2000). By definition, AID of AA are calculated as the percentage of AA intake, which does not appear in ileal digesta. 'Apparent' refers to the fact that the digestibility coefficients are not adjusted for basal ileal endogenous CP and AA losses that contribute to the total flow of CP and AA at the distal ileum. With increasing dietary CP and AA levels, these basal ileal endogenous losses affect AID in a non-linear manner. If corrections are made for these basal ileal endogenous losses, then the so-called 'standardized' ileal digestibilities (SID) of CP and AA can be calculated. Since SID of CP and AA are independent of the CP and AA contents in the assay diet, these values have proven to be superior over AID and represent a fundamental property of the individual feedstuff. The key issue for the calculation of the SID is the measurement of AID above the so-called dietary threshold levels and the quantification of the basal endogenous losses at the ileal level (Fan et al. 1995, GfE 2005, Rodehutscord and Mosenthin 2005). Based on an extensive literature review, published values on AID in grower finisher pigs were corrected for basal ileal endogenous losses. The results of this survey were recently published by the German Society of Nutrition Physiology (GfE 2005) to be officially used for the calculation of SID in diet formulation for pigs. lt could be confirmed in own studies that dietary threshold levels and basal ileal endogenous losses are similar between grower finisher and newly weaned pigs (Eklund et al. 2005, 2006). Based upon these results, several studies have been carried out to measure SID in a variety of protein ingredients frequently used in piglet nutrition. The results of this study have been published recently (Urbaityte et al. 2005) and are available in form of a pamphlet distributed by Hamlet Protein A/S (2006). Publications of the results in refereed journals as part of a PhD Thesis are in progress.