Trusted information & resources for animal nutrition.

Technical Resources

Effect of particle size on nutritional value of soybean meal for poultry

Ahasic, E.

Five experiments were conducted to determine the effect of particle size on the nutritional value of soybean meal (SBM) for poultry. A single sample of unmilled solvent-extracted SBM was acquired from a commercial solvent extraction facility located in the Midwest and ultimately processed to obtain seven particle sizes. Experiments 1 and 2 used the precision-fed rooster assay to determine true metabolizable energy corrected to zero nitrogen retention (TMEn) and standardized amino acid digestibility in seven SBM samples that had a mean particle size of < 386, 466, 809, 1,174, 1,577, 2,026, or 2,321 μm. The TMEn of the SBMs were determined using conventional roosters while the standardized amino acid digestibility was determined using cecectomized roosters. In both experiments, six single comb white-leghorn roosters were tube fed 30 g of one of the seven SBM samples. There were no significant differences for TMEn among SBM samples. There was also no consistent significant effect of particle size on standardized amino acid digestibility. In Experiment 3, growth performance, apparent metabolizable energy (AMEn), ileal phosphorus (P) digestibility, excreta P retention, gizzard weight, and standardized amino acid digestibility were determined using a 21 d broiler chick assay. Four corn-SBM diets that only differed in the mean particle size (466, 809, 1,174, or 1,577 μm) of the SBM were fed from 2-23 d of age. Weight gain, feed intake, feed efficiency, gizzard weight, AMEn, and excreta P retention showed differences (P<0.05) among dietary treatments. Ileal P digestibility and standardized amino acid digestibilities did not differ among treatments. Chicks fed diets containing 809 or 1,174 μm SBM had increased weight gain compared with chicks fed 466 μm SBM, and chicks fed diets containing 1,174 or 1,577 μm SBM had increased feed efficiency compared with chicks fed 466 μm SBM. The diet containing 466 μm SBM yielded the highest AMEn and excreta P retention. Relative gizzard weight (percent of body weight) was increased by the largest SBM particle size. Experiments 4 and 5 were both chick assays and were conducted to determine the digestibility or bioavailability of P in four SBM particle sizes. Experiment 4 was a 4 x 2 factorial treatment arrangement of four mean SBM particle sizes (466, 809, 1,174, and 1,577 μm) and two dietary calcium (Ca) levels (0.2 and 0.75%) and was conducted to determine ileal P digestibility and excreta P retention at 20 d of age in commercial broiler chicks. Ileal P digestibility values (86 to 90%) were not affected by SBM particle size when Ca was 0.2%. However, at 0.75% dietary Ca, ileal digestibility of the P in 1,577 μm SBM was higher (P<0.05) than the other SBM particle sizes. Chicks fed diets containing 0.2% Ca had higher ileal P digestibility and excreta P retention values when compared with chicks fed the diets containing 0.75% Ca. Experiment 5 was conducted to determine the relative bioavailability of P in the four SBM relative to potassium phosphate (KH2PO4) using a tibia bone ash assay. Crossbred chicks (New Hampshire x Columbian) were fed one of 11 experimental diets from 8-22 d of age. The first diet was a P-deficient-cornstarch-dextrose-SBM diet (0.14% nonphytate P). The remaining diets were the first diet supplemented with 0.05 or 0.10% P from KH2PO4 or 12.5 or 25% SBM that had a mean particle size of 466, 809, 1,174, or 1,577 μm. Bioavailability of SBM P relative to KH2PO4 was estimated using the slope ratio method for multiple regression of tibia ash (mg/tibia or tibia ash %) regressed on supplemental P intake. The 1,577 μm SBM yielded the highest P bioavailability value (30%) which was higher (P<0.05) than the value for 466 μm SBM (20%). The relative bioavailability values based on tibia ash in Experiment 5 were lower than the ileal P digestibility and excreta P retention values in Experiment 4.

The results of Experiments 1-3 suggest that increasing SBM particle size may be beneficial to broiler growth performance and may increase gizzard size. Based on the results from Experiments 4 and 5, increased particle size has the potential to increase digestibility/bioavailability of P in SBM, and dietary Ca level greatly affected SBM P digestibility values.