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Evaluation of in situ valine production by Bacillus subtilis in young pigs
- J. V. Nørgaard, N. Canibe, E. A. Soumeh, B. B. Jensen, B. Nielsen, P. Derkx, M. D. Cantor, K. Blaabjerg, H. D. Poulsen
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Mutants of Bacillus subtilis can be developed to overproduce Val in vitro. It was hypothesized that addition of Bacillus subtilis mutants to pig diets can be a strategy to supply the animal with Val. The objective was to investigate the effect of Bacillus subtilis mutants on growth performance and blood amino acid (AA) concentrations when fed to piglets. Experiment 1 included 18 pigs (15.0±1.1 kg) fed one of three diets containing either 0.63 or 0.69 standardized ileal digestible (SID) Val : Lys, or 0.63 SID Val : Lys supplemented with a Bacillus subtilis mutant (mutant 1). Blood samples were obtained 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding and analyzed for AAs. In Experiment 2, 80 piglets (9.1±1.1 kg) were fed one of four diets containing 0.63 or 0.67 SID Val : Lys, or 0.63 SID Val : Lys supplemented with another Bacillus subtilis mutant (mutant 2) or its parent wild type. Average daily feed intake, daily weight gain and feed conversion ratio were measured on days 7, 14 and 21. On day 17, blood samples were taken and analyzed for AAs. On days 24 to 26, six pigs from each dietary treatment were fitted with a permanent jugular vein catheter, and blood samples were taken for AA analysis 0.5 h before feeding and at 1, 2, 3, 4, 5 and 6 h after feeding. In experiment 1, Bacillus subtilis mutant 1 tended (P<0.10) to increase the plasma levels of Val at 2 and 3 h post-feeding, but this was not confirmed in Experiment 2. In Experiment 2, Bacillus subtilis mutant 2 and the wild type did not result in a growth performance different from the negative and positive controls. In conclusion, results obtained with the mutant strains of Bacillus subtilis were not better than results obtained with the wild-type strain, and for both strains, the results were not different than the negative control.
Microbial phytase addition resulted in a greater increase in phosphorus digestibility in dry-fed compared with liquid-fed non-heat-treated wheat–barley–maize diets for pigs
- K. Blaabjerg, A.-M. Thomassen, H. D. Poulsen
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The objective was to evaluate the effect of microbial phytase (1250 FTU/kg diet with 88% dry matter (DM)) on apparent total tract digestibility (ATTD) of phosphorus (P) in pigs fed a dry or soaked diet. Twenty-four pigs (65±3 kg) from six litters were used. Pigs were housed in metabolism crates and fed one of four diets for 12 days; 5 days for adaptation and 7 days for total, but separate collection of feces and urine. The basal diet was composed of wheat, barley, maize, soybean meal and no mineral phosphate. Dietary treatments were: basal dry-fed diet (BDD), BDD with microbial phytase (BDD+phy), BDD soaked for 24 h at 20°C before feeding (BDS) and BDS with microbial phytase (BDS+phy). Supplementation of microbial phytase increased ATTD of DM and crude protein (N×6.25) by 2 and 3 percentage units (P<0.0001; P<0.001), respectively. The ATTD of P was affected by the interaction between microbial phytase and soaking (P=0.02). This was due to a greater increase in ATTD of P by soaking of the diet containing solely plant phytase compared with the diet supplemented with microbial phytase: 35%, 65%, 44% and 68% for BDD, BDD+phy, BSD and BSD+phy, respectively. As such, supplementation of microbial phytase increased ATTD of P in the dry-fed diet, but not in the soaked diet. The higher ATTD of P for BDS compared with BDD resulted from the degradation of 54% of the phytate in BDS by wheat and barley phytases during soaking. On the other hand, soaking of BDS+phy did not increase ATTD of P significantly compared with BDD+phy despite that 76% of the phytate in BDS+phy was degraded before feeding. In conclusion, soaking of BDS containing solely plant phytase provided a great potential for increasing ATTD of P. However, this potential was not present when microbial phytase (1250 FTU/kg diet) was supplemented, most likely because soaking of BDS+phy for 24 h at 20°C did not result in a complete degradation of phytate before feeding.
Effect of particle size and microbial phytase on phytate degradation in incubated maize and soybean meal
- M. A. Ton Nu, K. Blaabjerg, H. D. Poulsen
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The objective of the study was to evaluate the effect of screen size (1, 2 and 3 mm) and microbial phytase (0 and 1000 FTU/kg as-fed) on phytate degradation in maize (100% maize), soybean meal (100% SBM) and maize–SBM (75% maize and 25% SBM) incubated in water for 0, 2, 4, 8 and 24 h at 38°C. Samples were analysed for pH, dry matter and phytate phosphorus (P). Particle size distribution (PSD) and average particle size (APS) of samples were measured by the Laser Diffraction and Bygholm method. PSD differed between the two methods, whereas APS was similar. Decreasing screen size from 3 to 1 mm reduced APS by 48% in maize, 30% in SBM and 26% in maize–SBM. No interaction between screen size and microbial phytase on phytate degradation was observed, but the interaction between microbial phytase and incubation time was significant (P<0.001). This was because microbial phytase reduced phytate P by 88% in maize, 84% in maize–SBM and 75% in SBM after 2 h of incubation (P<0.05), whereas the reduction of phytate P was limited (<50%) in the feeds, even after 24 h when no microbial phytase was added. The exponential decay model was fitted to the feeds with microbial phytase to analyse the effect of screen size and feed on microbial phytase efficacy on phytate degradation. The interaction between screen size and feed affected the relative phytate degradation rate (Rd) of microbial phytase as well as the time to decrease 50% of the phytate P (t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ ) (P<0.001). Thus, changing from 3 to 1 mm screen size increased Rd by 22 and 10%/h and shortened t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ by 0.4 and 0.2 h in maize and maize–SBM, respectively (P<0.05), but not in SBM. Moreover, the screen size effect was more pronounced in maize and maize–SBM compared with SBM as a higher phytate degradation rate constant (Kd) and Rd, and a shorter t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ was observed in maize compared with SBM in all screen sizes (P<0.05). However, a higher amount of degraded phytate was achieved in SBM than in maize because of the higher initial phytate P content in SBM. In conclusion, reducing screen size from 3 to 1 mm increased Kd and Rd and decreased t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ in maize and maize–SBM with microbial phytase. The positive effect of grinding on improving microbial phytase efficacy, which was expressed as Kd, Rd and t $\scale70%{\vskip3pt{{\scale60%{\vskip-7pt1}{\hskip-3pt\vskip-5.6pt\rot160/}{\scale60%{\hskip-4pt\vskip0pt2}$ , was greater in maize than in SBM.
Heat-treatment, phytase and fermented liquid feeding affect the presence of inositol phosphates in ileal digesta and phosphorus digestibility in pigs fed a wheat and barley diet
- K. Blaabjerg, H. Jørgensen, A.-H. Tauson, H. D. Poulsen
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The aim was to evaluate the effect of heat-treatment, microbial phytase addition and feeding strategy (dry feeding v. fermented liquid feeding) on degradation of phytate (myo-inositol hexakisphosphate, InsP6) and formation and further degradation of lower inositol phosphates (myo-inositol pentakisphosphate–myo-inositol bisphosphate, InsP5–InsP2) at the distal ileum of pigs. Furthermore, the apparent ileal digestibility/degradability (AID) of phosphorus (P), InsP6–P and calcium (Ca) and the apparent total tract digestibility (ATTD) of P and Ca were studied. Pigs were fitted with a T-shaped ileal cannula for total collection of digesta at 2 h intervals during an 8 h sampling period after feeding the morning meal. Each period lasted for 2 weeks: 8 days of adaptation followed by 3 days of total collection of faeces and 3 days of total collection of ileal digesta. The experiment was designed as a 4 × 4 Latin square with four pigs fed four diets. A basal wheat/barley-based diet was fed either as non-heat-treated or heat-treated (steam-pelleted at 90°C). The heat-treatment resulted in an inactivation of plant phytase below detectable level. Diet 1 (non-heat-treated basal diet fed dry); diet 2 (heat-treated basal diet fed dry); diet 3 (as diet 2 but with microbial phytase (750 FTU/kg as fed) fed dry); diet 4 (as diet 3 fed liquid (fermented for 17.5 h nighttime and 6.5 h daytime at 20°C with 50% residue in the tank)). Chromic oxide (Cr2O3) was included as marker and ATTD was determined both by total collection of faeces (ATTDTotal) and Cr2O3 (ATTDCr). InsP6 was completely degraded in diet 4 before feeding resulting in no InsP6–P being present in ileal digesta. InsP6–P concentration in ileal digesta decreased with increasing dietary levels of plant or microbial phytase in pigs fed the dry diets. Consequently, AID and ATTD of P and Ca were greatest for pigs fed diet 4 followed by diets 3, 1 and 2. The ATTD of P depended on the used method as ATTDTotal of P was 72%, 61%, 44% and 34%, whereas ATTDCr of P was 65%, 52%, 38% and 23% for diets 4, 3, 1 and 2, respectively. In all pigs the ileal concentration of InsP5–InsP2–P was extremely small, and thus unimportant for maximisation of ATTD of plant P. In conclusion, fermented liquid feeding with microbial phytase seems to be an efficient approach to improve ATTD of plant P compared with dry feeding. This opens up for further reductions in P excretion.