This study consisted of two experiments to assess soybean meal (SBM) with improved traits fed to Cobb 500 male broilers. In Experiment 1, 3 dietary treatments replicated 10 times (540 broilers) varying in SBM source were tested (0 to 45 d-of-age): conventional soybeans processed using solvent extraction (ConvSE), conventional soybeans processed using extrusion and expeller pressing (ConvEE), and an experimental line of soybeans selected for increased amino acid composition (i.e., less limiting amino acids) processed using extrusion and expeller pressing (ExpEE). In Experiment 2, the ConvEE and ExpEE dietary treatments were replicated 10 times and fed to chicks (240 broilers) from d 0 to 13. In Experiment 1, the treatment design allowed for all treatments being equal in the first five limiting amino acids (i. e., varying levels of SBM) and iso-caloric, and in Experiment 2 the treatment design represented direct substitution of soybean meal source. In Experiment 1, 45-d broiler performance and processed yields (i.e., BW gain, feed intake, feed:gain, intestinal tight junction integrity, and processed yields and myopathies) did not differ among dietary treatments (P > 0.05). In Experiment 2, 13-d chick BW gain, feed intake, and feed:gain were not affected by dietary treatments. However, the ExpEE compared to the ConvEE contained higher (P ≤ 0.05) digestible amounts of Lys, Thr, Ser, Val, Ile, Leu, Arg, Trp, Phe, and Tyr. In conclusion, although ExpEE diets contained 1.30-1.80 % less SBM than the other treatments, broilers fed ExpEE treatments exhibited similar performance to broilers fed higher inclusions of SBM, which can be explained by ExpEE having soybeans selected for increased amino acid composition that were found to be more digestible in Thr, Ser, Val, Iso, Leu, Tyr, Phe, Lys, Arg, and Trp (P<0.05).
Keywords: Amino acid; Breast myopathies; Broiler performance; Digestibility; Genotype; Processing; Soybean.
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