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Ileal digestibility of crude protein and amino acids of soybean meals of different origins in broilers

L. Aguirre, L., L. Cámara, A. Smith, G. Fondevila, J. Mabrouk and G. Mateos

The influence of the origin of the soybeans on the apparent (AID) and standardized (SID) ileal digestibility of CP and amino acids (AA) of 27 commercial soybean meals (SBM) from Argentina (ARG), Brazil (BRA), and USA was studied in broilers at 21 d of age. The samples (n = 9 per origin) were collected at the arrival of the vessels to Europe or at the crushing plants and were analyzed for main components (CP, AA, ether extract, carbohydrates, and minerals), protein quality indicators (urease activity, protein dispersibility index, KOH solubility, and trypsin inhibitor activity), and reactive Lys, using the homoarginine and furosine procedures. Broilers received a commercial corn-SBM diet in crumble form from hatch to 16 d of age and then, their corresponding experimental diets for 5 d. The experimental diets resulted from the combination of 53% of a N-free diet (dextrose, soybean oil, lignocellulose, minerals, and vitamins) and 47% of the corresponding SBM tested, as the unique source of N. Each of the 27 experimental diets was replicated 6 times and the experimental unit was a cage with 8 broilers. Chemical analyses and in vivo data were analyzed as a completely randomized design using the MIXED procedure of SAS, with SBM origin as main effect. For the in vivo data, SBM sample within each origin, was used as a nested effect. On 88% DM basis, CP (N × 6.25) was higher for the BRA meals than for the ARG and USA meals (47.4, 46.3, and 46.5%; P < 0.05). Per unit of protein, however, the contents in Lys, TSAA, and the sum of 5 key AA (Lys, Met, Cys, Thr, and Trp) were higher for the USA meals than for the South American meals (P < 0.05). At 21 d of age, the SID of the protein (92.2 vs. 91.2 and 91.6%; P < 0.05) and of the sum of 5 key AA (91.7, 90.5, and 91.3%; P < 0.05) were higher for the USA meals than for the BRA and ARG meals. When each AA was evaluated individually, the SID of Arg (94.9 vs. 93.8 and 94.1%) and Lys (93.8 vs. 92.4 and 93.3%) were higher (P < 0.05) for the USA meals than for the BRA and ARG meals. Similar differences to those reported for the SID were found for the AID values. Based on the coefficient of variation (%), the SID and AID values of the SBM samples for all key AA except Trp, were less variable for the USA than for the South American meals.

In summary, the ileal digestibility of the protein and of the AA of the SBM in broilers at 21 d of age was more variable than expected and depended, at certain extent on the country of origin of the soybeans. Consequently, a continuous update on the chemical content and nutritional value of the SBM, based on the particular shipment and on the origin of the soybeans, is needed to optimize diet cost in the feed formulation process.