Evaluation of nutritional traits of soy protein concentrate (SPC) in broiler chicks and turkey poults
The objectives of this study were to determine the apparent metabolizable energy (AME), nitrogen corrected AME (AMEn) of soy protein concentrate (SPC), and standardized ileal amino acid digestibility (SIAAD) of (SPC) and dehulled soybean meal (SBM) in broiler and turkey poults. Soy protein concentrate and SBM was the only source of CP in their respective semi-purified diets used for estimating SIAAD in 7 and 21 d-old broiler chicken and turkey poults. Two experiments (Exp 1 and 2) were conducted with 6 replicate cages of 20 (d 7) and 6 (d 21) birds/cage. In Exp.1, experimental diets containing 0, 7, 14, and 21% of SPC replaced the energy contributing ingredients in the diet. Excreta were collected from d 5 to 7 and d 19 to 21, frozen, and dried. In Exp. 2, two semi-purified diets were formulated to contain 20% CP. Experimental diets were fed for 5 d (d 2 to 7) and (d 16 to 21) and ileal digesta was collected on d 7 and 21.In Exp.1, increasing dietary SPC had no effect on AME or nitrogen-corrected AME (AMEn) at 7 d of age in broiler chicken. However, increasing SPC linearly improved AME (P=0.002) and AMEn (P=0.019) at 21 d. The AME and AMEn for SPC containing diets based on linear regression was 2,784 and 2,622 Kcal/Kg at 7 and 3,676 and 3,473 kcal/kg at 21 d, respectively. In Exp. 2, apparent DM and N digestibility for SPC and SBM based diet increased (P=0.0001) from d 7 to 21. There was a soy source by age interaction (P<0.05) for SIAAD, where SBM digestibility increased only slightly from d 7 to 21, while digestibility of SPC increased quite remarkably. In turkey poults, increasing SPC linearly improved AME and AMEn on d 7 and 21 (P ≤ 0.028). The AME and AMEn for SPC containing diets based on linear regression was 3,385 and 3,152 at 7 and 3,666 and 3,409 on d 21, respectively. In Exp. 2, apparent DM digestibility for SPC-and SBM-based diets were not significantly different between ages (P >0.10) and diets (P=0.097). Apparent N digestibility was different between ages (P<0.05) but not different between diets (P>0.10) with no age by diet interaction. The SIAAD were not significantly different between ages and diets. In conclusion, replacing the energy contributing ingredients of a corn/SBM basal diet with graded levels of SPC resulted in significant improvement in AME and AMEn in both broiler chicks (21d) and turkey poults (7 and 21d). SBM has a slightly higher SIAAD compared to SPC in broiler chicks and the digestibility of DM, N, and amino acids were substantially less at 7 versus 21 d of age. In turkey poults, the amino acid content of SPC was well utilized by the young poults compared to the broiler chicken. Nevertheless, SPC has considerably higher energy and amino acid density than SBM in both species.
Applegate, Purdue University.
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