Research Note: Evaluation of phytic acid disappearance, ileal P digestibility, and total tract P retention in canola meal supplemented with increasing levels of exogenous phytase using conventional and cecectomized precision-fed roosters and growing chicks

Apparent ileal digestibility (AID) of P, apparent total tract retention (ATTR) of P, and phytic acid disappearance in canola meal were evaluated in the presence of increasing levels of exogenous phytase. In Experiment 1, a precision-fed rooster assay was used to determine phytic acid (myo-inositol 1,2,3,4,5,6-hexakis; InsP6) and inositol phosphate (InsP6-3; InsP-P) disappearance in conventional and cecectomized Leghorn roosters. Roosters were crop intubated with 25 g of canola meal mixed with 0, 500, 1,000, or 2,000 FTU/kg of exogenous phytase. In Experiment 2, InsP6 and InsP-P disappearance and AID and ATTR of P were determined using ad libitum-fed broiler chickens. Treatments consisted of semi-purified diets containing 45% canola meal as the sole source of P. Phytase was added to increase phytase activity by 0, 500, 1,000, or 2,000 FTU/kg. Experiments contained 6 replicates per treatment. Canola meal contained a high phytase activity (1,630 FTU/kg as-fed) due to contamination with a commercially available phytase at the feed mill from which the canola meal was sourced. In Experiment 1 with precision-fed roosters, there was no effect (P > 0.05) of phytase or bird type on InsP6 and InsP-P disappearance; however, phytase linearly reduced (P < 0.05) InsP3 concentrations in excreta. In Experiment 2 with ad libitum-fed chickens, phytase linearly increased (P < 0.05) ileal InsP6 and InsP-P disappearance, and phytase had a quadratic effect (P < 0.05) on excreta InsP6 and InsP-P disappearance. Increasing dietary phytase activity resulted in a linear increase (P < 0.05) in AID of P and phytase had a quadratic effect (P < 0.05) on ATTR of P. In conclusion, titration of high levels of phytase (1,600 to 3,600 FTU/kg as-fed) reduced InsP3 concentrations in precision-fed roosters but did not affect overall phytic acid hydrolysis, which was 78% or greater for all treatments; however, increasing the total phytase activity from 700 to 2,700 FTU in ad libitum-fed broiler chickens increased phytic acid disappearance and P digestibility.

Determination of TMEn, standardized amino acid digestibility, phosphorus digestibility, and phosphorus bioavailability in conventional and reduced phosphorus distillers dried grains with solubles

The TME_n, amino acid (AA) digestibility, and P availability in 2 conventional corn distillers dried grains with solubles (C-DDGS1 and 2; 0.86 to 1.14% P, DM basis) and reduced phosphorus DDGS (RP-DDGS; 0.39% P) were evaluated. The TME_n of C-DDGS1 and 2 and RP-DDGS were determined in Experiment 1 using conventional adult Leghorn roosters, while standardized AA digestibility was determined in Experiment 2 using cecectomized roosters. Apparent ileal digestibility (AID) of P at different Ca levels was determined using precision-fed (crop intubation) broiler chickens in Experiments 3 and 4. The AID and total tract retention of P in C-DDGS2 were evaluated in Experiment 5 using ad libitum-fed broilers. Phosphorus bioavailability in C-DDGS2 relative to KH₂PO₄ based on bone ash was determined in Experiment 6. Experiments contained 4 to 5 replicates per treatment. In Experiment 1, the TME_n of C-DDGS1 and RP-DDGS was 3,428 and 2,840 kcal/kg, respectively (DM basis). In Experiment 2, there were no differences (P > 0.05) in rooster AA digestibility values between C-DDGS1 and RP-DDGS. In Experiment 3 with precision-fed chicks, AID of P in C-DDGS1 and RP-DDGS was 81 and 59%, respectively; there was no effect (P > 0.05) of increasing dietary Ca level from 0.04 to 1.0% for C-DDGS1 or reducing Ca from 1.5 to 1.0% for RP-DDGS. The AID of P in precision-fed chicks for C-DDGS2 in Experiment 4 was 48 and 80% at 1.3 and 0.3 Ca:total P ratios, respectively (P < 0.05). In Experiment 5, AID of P in C-DDGS2 at Ca:total P ratios of 1.3 and 2.5 was 63 and 42%, respectively, in precision-fed chicks. Regression of bone ash content (mg/tibia) on supplemental P intake in Experiment 6 yielded a P bioavailability of 61% relative to KH₂PO₄ for C-DDGS2. In conclusion, total and digestible P content in RP-DDGS was greatly reduced compared with C-DDGS, and the digestibility and bioavailability of the P in C-DDGS was affected by type of experimental assay and dietary Ca level.

Quantification of secretory IgA and mucin excretion and their contributions to total endogenous amino acid losses in roosters that were fasted or precision-fed a nitrogen-free diet or various highly digestible protein sources

The objective of this study was to quantify total secretory IgA (sIgA) and mucin excretion via excreta in roosters fed diets containing highly digestible protein sources and to determine their proportional contributions to total endogenous amino acid (AA) losses. Precision-fed rooster assays with 24 h excreta collections were conducted using conventional White Leghorn roosters (4-8 roosters per treatment). In Experiment 1, roosters were fasted or precision-fed 30 g (crop intubation) of a nitrogen-free (NF) or semi-purified diet containing 10% casein. Roosters in Experiment 2 received a NF or semi-purified diet containing either 10% casein, 17% whole egg, 10% egg white, 9.8% soy protein isolate, 10.2% chicken breast meat, 11.2% spray-dried animal plasma (SDAP), or an AA mixture containing the same AA as casein. A Latin square design was used in Experiment 3, where roosters received NF or semi-purified diets containing either 10% casein, 17% whole egg, or 9.6% of a crystalline AA mixture to evaluate both diet and individual bird effects. In Experiment 1, mucin excretion did not differ (P > 0.05) among treatments; however, total sIgA excretion was lower for fasted birds, intermediate for the NF diet, and highest for casein (P < 0.05). Total endogenous AA losses (proportion of the total) from sIgA were higher for roosters fed casein, whereas mucin contributions were higher for fasted roosters (P < 0.05). In Experiment 2, sIgA excretion did not differ (P > 0.05) among treatments; however, mucin excretion was reduced for NF, whole egg, egg white, and chicken breast compared with casein and SDAP. In Experiment 3, sIgA and mucin excretion did not differ (P > 0.05) among treatments; however, sIgA excretion differed among individual roosters (7-27 mg/24 h; P < 0.05). Overall, fasting reduced sIgA excretion and sIgA and mucin excretion were affected by dietary protein source. Further, roosters excreted a substantial amount of sIgA, and sIgA and mucin were considerable contributors to total endogenous AA losses.

Research Note: Evaluation of a precision-fed rooster assay for determination of phytic acid disappearance in feedstuffs

The objective of this study was to evaluate a precision-fed rooster assay that is suitable for determination of phytic acid (myo-inositol 1,2,3,4,5,6-hexakis; InsP₆) disappearance in plant-based feed ingredients. A 48-h precision-fed rooster assay was used to measure InsP₆ disappearance using conventional White Leghorn roosters. A minimum of 4 individually-caged roosters per treatment were fasted for 26 h prior to crop intubation with 15 to 30 g of sample, and excreta were quantitatively collected for 48 h. Soybean meal, soybean hulls, canola meal, conventional distillers dried grains with solubles (DDGS), palm kernel meal (PKM), and wheat bran were evaluated in Experiment 1, whereas wheat middlings (WM) and rice bran (RB) were evaluated without and with 1,000 and 1,800 U/kg phytase in Experiment 2. Data from Experiment 1 were subjected to a one-way ANOVA for a completely randomized design, while data from Experiment 2 were subjected to two-way ANOVA for a 2 × 3 factorial arrangement of treatments. In Experiment 1, InsP₆ disappearance ranged from 3 to 95% among all ingredients. The InsP₆ disappearance for conventional DDGS (95%) was the highest (P < 0.05), wheat bran and soybean hulls were intermediate (47-48%), PKM was low (24%), and soybean meal and canola meal were very low (3-5%). In Experiment 2, there was a significant ingredient × phytase interaction (P < 0.05). Phytase inclusion at both 1,000 and 1,800 U/kg resulted in a significant improvement (P < 0.05) in InsP₆ disappearance for RB; however, only the addition of 1,800 U/kg resulted in an increase in InsP₆ disappearance for WM. The addition of 1,800 U/kg phytase increased the InsP₆ disappearance from 58 to 74% for WM and from 26 to 53% for RB. These results suggest the precision-fed rooster assay can be used to evaluate phytic acid disappearance in plant-based feed ingredients and the assay was able to detect a significant effect of 1,800 U/kg of exogenous phytase on phytic acid disappearance for WM and RB.

Standardized amino acid digestibility and true metabolizable energy for several increased protein ethanol co-products produced using back-end fractionation systems

Precision-fed rooster trials were conducted to evaluate standardized AA digestibility and TME_n of the increased protein ethanol co-products corn fermented protein (CFP), high protein-distillers dried grains with solubles (HP-DDGS), and reduced fiber high protein-DDGS (RFHP-DDGS) produced using post-fermentation back-end fractionation systems. The TME_n was determined using conventional adult Leghorn roosters, while cecectomized roosters were used to determine standardized AA digestibility. Three to 6 roosters were fasted per treatment for 26 h prior to crop intubation with 27 g of sample and excreta were collected for 48 h post-feeding. Statistical analyses were conducted using a one-way ANOVA for a completely randomized design. Eight samples of CFP were found to contain a mean of 56% CP (DM basis) compared with a mean of 32% for conventional DDGS. The mean TME_n of CFP (3,556 kcal/kg) was greater (P < 0.05) than conventional DDGS1 and 2 (2,767 kcal/kg DM); mean standardized AA digestibility for CFP was similar to conventional DDGS and ranged from 88 to 94%. The mean digestible Lys, Met+Cys, and Thr concentrations for conventional DDGS were 0.79, 1.12, and 0.94%, respectively, whereas those for CFP were 1.74, 2.06, and 1.88%, respectively (DM basis). Two samples of HP-DDGS contained a mean of 51% CP (DM basis), a mean TME_n of 3,325 kcal/kg DM, a mean standardized AA digestibility of 90%, and mean concentrations of digestible Lys, Met+Cys, and Thr, which were 1.53, 1.77, and 1.60%, respectively (DM basis). The mean CP content of 2 RFHP-DDGS was 48% and the mean TME_n was 3,711 kcal/kg DM, which was greater (P < 0.05) than conventional DDGS3 and 4 (2,920 kcal/kg DM). Mean standardized AA digestibility of RFHP-DDGS was 90% and mean digestible Lys, Met+Cys, and Thr concentrations increased from 0.82, 1.01, and 0.95% for conventional DDGS, respectively, to 1.00, 1.59, and 1.44% for RFHP-DDGS, respectively (DM basis). Results indicate these high protein corn ethanol co-products have increased nutritional value for poultry compared with conventional DDGS.

Metabolizable energy and amino acid digestibility in spray-dried animal plasma using broiler chick and precision-fed rooster assays

Four experiments were conducted to determine ME and amino acid (AA) digestibility of spray-dried animal plasma (SDAP) and soybean meal (SBM). The 48-h precision-fed adult rooster assay was used in 2 experiments; TMEn and standardized AA digestibility were determined using conventional and cecectomized roosters, respectively, 50 weeks of age and weighing approximately 2,200 g. Eight individually-caged roosters (4 per diet) were fasted for 26 h, then precision-fed 30 g of SDAP mixture (containing 50% corn) or SBM mixture (containing 50% corn). The TMEn and AA digestibility for SDAP and SBM were calculated by the difference procedure. The TMEn for SDAP was greater (P < 0.05) than SBM (3,743 and 2,669 kcal/kg DM, respectively). Similarly, mean AA digestibility of SDAP was greater (P < 0.05) than SBM (94 and 86%, respectively). Two assays were conducted using Ross male broilers to determine AMEn and apparent (AIAAD) and standardized (SIAAD) ileal AA digestibility of SDAP and SBM. A 3 × 2 factorial arrangement of treatments was used to determine AMEn; 126 chicks (6 replicate pens of 7 chicks) were fed a corn-SBM-based reference diet, a diet containing 30% SDAP, or a diet containing 30% SBM from d 7 to 10 and 18 to 21. A 2 × 2 factorial arrangement of treatments was used to determine AIAAD and SIAAD; 168 chicks (12 replicate pens of 7 chicks) were fed a semi-purified diet containing 25% SDAP or a semi-purified, isonitrogenous diet containing 41% SBM from d 7 to 10 and 18 to 21. The AMEn for SDAP was greater (P < 0.05) than SBM at d 10 (3,851 and 2,089 kcal/kg DM, respectively) and d 21 (4,239 and 2,849 kcal/kg DM, respectively). The second assay showed an increase (P < 0.05) in AIAAD and SIAAD for SDAP compared with SBM at d 10 (mean SIAAD for SDAP and SBM were 96% and 84%, respectively) and d 21 (97% and 87%, respectively). Regardless of assay or age, these results indicate SDAP is a highly digestible feed ingredient with high ME and AA digestibility.