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Determination of TMEn, standardized amino acid digestibility, and phosphorus digestibility in soybean expellers produced from a new variety of soybeans fed to chickens

Cristobal, M., J. Blair, P. Utterback , H. Stein and C. Parsons

The objective of this study was to test the hypothesis that nitrogen-corrected true metabolizable energy (TMEn), standardized amino acid (AA) digestibility, and apparent ileal P digestibility are not different in a soybean expeller (SBE) produced from a new variety of Photoseed soybeans compared with SBE produced from conventional soybeans. The Photoseed soybeans have been developed to capture more carbon and sunlight, leading to an ingredient that has reduced environmental footprint from crop production. The two SBE contained approximately 46.3 % protein on a DM basis. In Experiments 1 and 2, two precision-fed rooster assays were conducted to determine TMEn and standardized AA digestibility in conventional and Photoseed SBE using conventional and cecectomized roosters, respectively. For each experiment, six replicate White Leghorn roosters were fasted for 26 h and then tube fed 25 g of each SBE, and excreta samples were collected for 48 h post-feeding. Data were analyzed as a one-way ANOVA for a completely randomized design. Differences between treatments were considered significant at P < 0.05. Results from Experiment 1 yielded TMEn values of 3.162 and 3.261 kcal/g DM for the conventional SBE and Photoseed SBE, respectively, with the value being greater (P < 0.05) for Photoseed SBE. Results from Experiment 2 showed standardized digestibility of most AA of approximately 90%, and there was no difference between the two SBE. However, Photoseed SBE had greater (P < 0.05) concentrations of digestible Arg, Lys, Phe, Trp, and Val compared with conventional SBE. In Experiment 3, an ad-libitum-fed broiler chicken assay was conducted to determine apparent ileal P digestibility in conventional and Photoseed SBE. Eighty commercial Ross 308 male chicks were fed a standard corn- SBM diet from 0 to 16 d of age and birds were then fed diets containing one of the SBE as the only source of P from d 17 to 21. The 2 experimental diets had a Total Ca:Total P ratio of 1.4:1 and TiO2 was used as a digesta marker. There were 5 chicks per pen and 8 replicate pens per treatment and the pen was the experimental unit. On d 21, chicks were euthanized and ileal digesta were collected. Data were analyzed as in Experiments 1 and 2. Results indicated values for apparent ileal P digestibility of 46.8% and 40.6% for conventional SBE and Photoseed SBE, respectively, and these values were not different. In summary, TMEn was greater in Photoseed SBE compared with conventional SBE, but digestibility of AA and P was not different although Photoseed SBE had greater concentrations of some indispensable AA compared with conventional SBE.

Results of this study indicated that Photoseed SBE has greater nutritional value than conventional SBE.