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Correlations between chemical composition and in vivo AMEn and ileal digestibility of amino acids of soybean meals of different origins in broilers

Mateos, G.

The objective of this research was to study the correlations among the chemical composition, protein quality, and AMEn content and standardized ileal digestibility (SID) of CP and amino acids (AA) determined in vivo in 21-d old broilers of soybean meal (SBM) samples from Argentina, Brazil, and USA. The samples (n= 9 per country) were collected at random in Europe and analyzed for main components (CP, AA, ether extract, fiber fraction, sucrose, stachyose, raffinose, and minerals), protein quality indicators [(urease activity, KOH solubility, protein dispersibility index, trypsin inhibitor activity (TIA)], and reactive Lys, using the homoarginine and furosine procedures. In addition, protein digestibility was determined in vitro, using 3 published methodologies based on pepsin and pancreatin. Broilers received a commercial corn-SBM diet in mash form from 0 to 16 d of age followed by the experimental diets which resulted from the combination of 53% of a N-free diet and 47% of the SBM tested, as the unique source of N. Each of the 27 SBM samples was replicated 6 times and the experimental unit was a cage with 8 broilers. Data were analyzed as a completely randomized design with origin of the SBM as main effect. The Pearson correlation coefficient (r) among the key variables studied, was determined using the CORR procedure of SAS. Numerous correlations between in vivo data and chemical composition of the SBM were detected and therefore, only those most relevant for the industry are discussed. Independent of the origin of beans, the AMEn contents of the SBM were positively correlated with the SID of CP (r = 0.523; P < 0.01), Lys (r = 0.492; P < 0.01), and the sum of five (Lys, Met, Cys, Thr, and Trp) key AA (r = 0.543; P < 0.01). Also, positive correlations between AMEn and reactive Lys (% Lys) determined by the homoarginine procedure (r = 0.526; P < 0.01), and between the SID of CP and key main protein quality indicators [PDI (r = 0.403; P < 0.05), TIA (r = 0.360; P < 0.10), and KOH (r = 0.324; P < 0.10)] were observed. Also, significant correlations between the SID of CP and Lys and reactive Lys (% Lys) of the SBM using the homoarginine procedure, were detected (r= 0.553 and 0.599; P < 0.01). However, no significant correlations between in vivo SID and in vitro CP digestibility were observed.

In summary, significant correlations among the AMEn and ileal digestibility of CP and quality traits of the protein fraction of commercial SBM were found. A better understanding of the existing correlations between AMEn content, protein ileal digestibility, and chemical analyses of commercial SBM, might help to improve the estimated nutritive value and use of this ingredient in feed formulation.