Browsing by Subject "Particle size"

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Effects of pretreatment with a ball mill on methane yield of horse manure
(2023) Heller, René; Roth, Peter; Hülsemann, Benedikt; Böttinger, Stefan; Lemmer, Andreas; Oechsner, Hans
Lignocellulosic biomass is an abundant organic material, which can be utilised in biogas plants for sustainable production of biogas. Since these substrates usually have high lignin contents and consist of rather elongated particles, a special pretreatment is required for an economical and process-stable utilisation in the biogas plant. The mechanical pretreatment of horse manure was carried out with the prototype of a ball mill at different speeds. The aim of ball milling is to comminute the substrate and disintegrate the lignocellulosic bond. Mechanical pretreatment in the ball mill resulted in a significant increase in specific methane yield of more than 37% in anaerobic batch digestion (up to 243 LCH4 kgVS−1) of horse manure. The kinetics of the methane gas formation process was analysed by a modified Gompertz model fitting and showed a higher methane production potential and maximum daily methane production rate as well as a lower duration of the lag phase after pretreatment at 6 rpm. This was further confirmed by sieve analyses, which showed a significant reduction of particle size compared to the untreated variant. Thus, the use of the ball mill increases the specific methane yield and improves the fermentation of lignocellulosic substrates such as horse manure.
Growth performance, phytate degradation, and tibia characteristics of broiler chickens fed pelleted diets with varying feed particle sizes and phytase levels
(2025) Wolfrum, Stephanie; Francesch, Maria; Jimenez-Moya, Beatriz; Feuerstein, Dieter; Rodehutscord, Markus
The objective was to investigate the effects of feed particle size and microbial phytase supplementation of pelleted diets on growth performance, myo-inositol hexakisphosphate (InsP6) degradation, and tibia characteristics in broiler chickens. Ross 308 broilers were housed in 56 floor pens in groups of 42, and seven pens were allocated to one of eight dietary treatments to measure the performance data on day 38 of age. From day 21 to 26, six birds from each floor pen were moved to metabolism units with the same distribution of treatments for digestibility and bone measurements. For the starter phase, two diets with fine or coarse particle size (429 or 657 µm mean particle size, determined after feed processing by wet sieving) were formulated and added with 500 FTU phytase/kg. For the grower and finisher phase, diets were arranged with two particle sizes (fine and coarse, 434 or 729 µm) and four phytase levels (0, 300, 600, and 1,200 FTU/kg). No significant interactions between particle size and phytase were determined. Prececal InsP6 disappearance and P digestibility were higher with fine than coarse particles, indicating that coarse grinding of rapeseed meal may not benefit birds. Increasing phytase supplementation increased ADG, ADFI, prececal InsP6 disappearance and P digestibility, tibia ash, and tibia breaking strength. Under the conditions of this study, birds were sufficiently supplied with P at a total P level of 4.0 g/kg and phytase supplementation of 1,200 FTU/kg. Renouncement of feed phosphate in the grower and finisher phase was possible without impaired performance.
Homogenization improves foaming properties of insoluble pea proteins
(2022) Moll, Pascal; Salminen, Hanna; Griesshaber, Elena; Schmitt, Christophe; Weiss, Jochen
Foams are essential in many food applications and require surface-active ingredients such as proteins for formation and stabilization. We investigated the influence of high-pressure homogenization on foaming properties of insoluble pea protein dispersions (5% w/w) at pH 3 and 5. Unhomogenized insoluble pea protein dispersions did not foam at either pH 3 or 5, as they consisted of large insoluble pea protein aggregates with limited surface activity. At pH 3, the homogenized pea protein dispersions generated foams due to higher protein solubility and surface activity through disruption of large protein aggregates into smaller particles. The foam stability decreased with increasing homogenization pressure and number of cycles due to a reduction in continuous phase viscosity. At pH 5, the insoluble pea proteins foamed when the homogenization resulted in formation of aggregates made of smaller protein entities, which was the case for homogenization ≥ 100 MPa and three cycles. In general, the foam capacity (amount of formed foam) was higher at pH 3 due to improved protein solubility and surface activity that facilitated incorporation of air, while the foam stability (resistance against foam collapse) was better at pH 5 because of the presence of larger protein aggregates that formed thicker and more viscous films around the air bubbles benefitting retention of gas bubbles. Overall, homogenization improved the foaming properties of insoluble pea proteins at pH 3 and 5.
Hydrostatic high pressure treatment of casein to generate defined particle and gel structures
(2006) Merel-Rausch, Eva; Hinrichs, Jörg
The focus of the work was to study the influence of pressure treatment conditions on pressure-induced casein structures in detail. The influence of process parameters like pressure build-up, pressure level, holding time and release rate but also temperature, ionic strength and casein concentration were determined. This work showed that the structure formation of casein under high pressure treatment depends on numerous factors. Sols but also gels can be formed and could be used for different applications particularly with the choice of the release rate and the milieu conditions, even if pressure conditions and casein concentration are kept constant.
Impact of particle size reduction on high gravity enzymatic hydrolysis of steam-exploded wheat straw
(2021) Hoppert, Luis; Einfalt, Daniel
Economically feasible bioethanol production from lignocellulosic biomass requires solid loadings ≥ 15% dry matter (DM, w/w). However, increased solid loadings can lead to process difficulties, which are characterized by high apparent slurry viscosity, insufficient substrate mixing and limited water availability, resulting in reduced final glucose yields. To overcome these limitations, this study focused on enzymatic hydrolysis of 10–35% DM solid loadings with steam-exploded wheat straw in two different particle sizes. At solid loadings of 20 and 25% DM small particle size of ≤ 2.5 mm yielded 16.9 ± 1.1% and 10.2 ± 1.4% increased final glucose concentrations compared to large particle size of 30 ± 20 mm. Small particle size also positively influenced slurry viscosity and, therefore, miscibility. As a key finding of this investigation, high gravity enzymatic hydrolysis with solid loadings of 30–35% DM was indeed successfully employed when wheat straw was applied in small particle size. Here, the highest final glucose yield was achieved with 127.9 ± 4.9 g L⁻¹ at 35% DM solid loading. An increase in the solid loading from 10 to 35% DM in small particle size experiments resulted in a 460% increase in the final glucose concentration.
Interactive effects of feed particle size, calcium, and exogenous phytase on gastrointestinal phytate degradation and related traits in broiler chickens
(2025) Wolfrum, Stephanie; Rodehutscord, Markus
Phosphorus (P) is an essential element in maintaining the physiological mechanisms of poultry, making an adequate dietary P supply crucial. In plant-based feed ingredients commonly used in poultry nutrition, the primary form of P is phytate, any salt of phytic acid (InsP6). Enzymes that hydrolyze InsP6, such as phytases and phosphatases, are needed to release P from InsP6 for digestion and absorption. The extent to which P is released depends on the limited and variable endogenous enzyme capacity of poultry. Consequently, diets are often supplemented with costly mineral P sources derived from finite global rock phosphates to meet P requirements. Any unabsorbed P is excreted and contributes to environmental impacts. Incorporating exogenous phytases into poultry diets enhances the P release from InsP6, thereby enabling reduced use of mineral P supplements. To further improve P utilization and completely replace supplemental mineral P, it is essential to understand the effects on phytase efficacy, both single and interactive. Therefore, three studies were conducted to gain deeper insight into the InsP6 degradation and related characteristics along the digestive tract of broiler chickens, as influenced by dietary ingredients and their physical properties. Using coarsely ground feed particles in broiler diets improves digestive tract development and nutrient utilization. Coarse particles may therefore be beneficial for InsP6 degradation. Moreover, dietary coarse particles might mitigate the inhibitory effects of high dietary calcium (Ca) concentrations by lowering the pH in the digestive tract. The first study aimed to investigate the single and interactive effects of feed particle size and Ca concentration in the absence and presence of exogenous phytase on InsP6 degradation, prececal digestibility of P, Ca, and amino acids (AA), and retention of P, Ca, and nitrogen (N). Ross 308 broiler chickens received experimental diets from day 7 to 22/23 of life. Experimental diets differed in feed particle size (fine and coarse; 222 and 309 μm), Ca concentration (low and high; 4.9 and 7.2 g/kg), and phytase supplementation (0 and 1,000 FTU/kg). Prececal InsP6 disappearance increased with coarse particle size without phytase supplementation. Supplemented phytase removed such differences. Coarse particles were associated with higher gizzard weights and lower gizzard content pH compared to fine particles, whereas high dietary Ca concentration increased the pH of the gizzard content. Thus, the antinutritive effects of the higher dietary Ca concentration were not mitigated by using coarse feed particles, resulting in a reduction in prececal InsP6 disappearance and digestibility of P and most of the AA. Prececal AA digestibility increased with dietary coarse particles compared to fine particles. In the presence of phytase, high dietary Ca enhanced InsP6 disappearance in the crop. The first study found that dietary coarsely ground feed particles without supplemented phytase increased prececal InsP6 disappearance, but phytase supplementation compensated for this particle size effect. Accordingly, the objective of the second study was to determine the single and interactive effects of feed particle size and phytase level. Effects on growth performance, prececal InsP6 disappearance, prececal digestibility of P and Ca, and tibia characteristics were examined. From day 10 to 38 of life, Ross 308 broilers were fed experimental diets containing fine and coarse feed particles (434 and 729 μm) and without and with phytase supplementation (300, 600, and 1,200 FTU/kg). Particle size and phytase did not interact significantly concerning any measured trait. Contrary to expectations, finely ground feed particles increased prececal InsP6 disappearance and P digestibility, suggesting coarse grinding of rapeseed meal may not benefit birds. Growth performance, prececal InsP6 disappearance and related P digestibility, as well as tibia ash and breaking strength, were increased by phytase supplementation. This indicated that diets met the bird’s P requirement at the given total P level and 1,200 FTU phytase/kg, allowing the renouncement of feed phosphate in the grower and finisher phases without adverse effects on performance and bones. Based on a previous study that found a linear relationship between the dietary InsP6 concentration and the prececal InsP6 disappearance caused by supplemented phytase, the third study aimed to verify this indication of a constant prececal InsP6 disappearance per unit of supplemented phytase. This suggested that the efficiency of supplemented phytase was not affected by dietary InsP6 concentration. The study investigated the effects of dietary InsP6 concentration and phytase supplementation on gastrointestinal InsP6 degradation, prececal digestibility of P, AA, and Ca, and N-corrected metabolizable energy (MEN) in broiler chickens. Ross 308 broilers were provided with diets from day 14 to 22/23 of life. Dietary InsP6 was increased by substituting corn starch with a mixture of 50 % soybean meal, 20 % rapeseed meal, 20 % sunflower meal, and 10 % rice bran (oilseed meal-rice bran levels (ORL)). Experimental diets included four dietary InsP6-P concentrations (ORL1, ORL2, ORL3, and ORL4) and three phytase levels (500, 1,500, and 3,000 FTU/kg). Feed ingredient exchange led to additional diet alterations beyond changes in InsP6 concentration, including variations in P, crude protein, Ca, and fiber concentrations. Increasing ORL decreased the InsP6 disappearance in the crop. Prececal InsP6 disappearance and P digestibility decreased linearly with increasing ORL at 500 FTU/kg, whereas ileal myo-inositol concentration was unaffected. This indicated that the supplemented phytase was the limiting factor for the complete dephosphorylation of InsP6 to myo-inositol. At 1,500 and 3,000 FTU/kg, prececal InsP6 disappearance and P digestibility differed hardly among ORL but decreased with increasing ORL. A non-linear relationship was found at 500 FTU/kg when prececal InsP6 disappearance or ileal myo-inositol concentration relative to FTU was regressed against dietary InsP6. Such relationships were linear at 1,500 and 3,000 FTU/kg, suggesting that the efficiency of supplemented phytase to fully hydrolyze InsP6 to myo-inositol at 1,500 FTU/kg or higher was impaired by phytase level but not ORL. The cecal InsP6 concentration increased with ORL and decreased with phytase. Increasing ORL decreased the prececal digestibility of all AA (except cysteine) and MEN. In conclusion, conflicting effects on InsP6 degradation concerning feed particle size and its effects on endogenous and supplemented enzymes were found. This suggests that using coarsely ground particles in the feed may not be equally effective for all ingredients. Rapeseed meal is potentially less suitable than wheat or corn in coarsely ground form. Regardless of phytase level, coarse feed particles increased prececal AA digestibility. Due to the inconsistent results and a lack of studies regarding feed particle size effects on InsP6 degradation and prececal AA digestibility, further research is needed. The antinutritive effects of dietary Ca on InsP6 degradation and prececal AA digestibility could not be compensated for by using coarse feed particles. To maximize nutrient utilization, feed particle size should be adapted to the respective raw material, and dietary Ca should be as low as possible without risking a deficit, combined with phytase. Supplemented phytase at 1,500 FTU/kg or higher does not impair InsP6 degradation and prececal AA digestibility in response to increasing ORL. Thus, adjusting the phytase level to increased dietary InsP6 concentrations was not necessary under the conditions of this study, and further research is necessary.
Investigations on the effects of forage source and feed particle size on ruminal fermentation and microbial protein synthesis in vitro
(2012) Hildebrand, Bastian; Rodehutscord, Markus
The synthesis of microbial protein in the rumen has a major impact on protein- and amino acid supply in ruminants. The amount and amino acid composition of the protein that enters the small intestine primarily depends on diet formulation. In the present studies the effects of maize silage (MS) and grass silage (GS) on ruminal fermentation and microbial protein synthesis were investigated, considering methodical aspects of in vitro studies, particularly grinding of feed samples. In the first experimental series five mixed diets with different proportions of MS and GS (100:0, 79:21, 52:48, 24:76 and 0:100) and a constant proportion of soybean meal (11%) were used. The content of crude protein (CP) and fibre fractions increased, whereas the content of organic matter (OM) and starch decreased with increasing proportion of GS in the diet. It was hypothesised that a combination of MS and GS can benefit microbial growth and thus fermentation of nutrient fractions to a higher extent than using only one forage source separately. It was also to be investigated how changes in diet composition affect the amino acid profile of microbial protein. A well standardised semi-continuous rumen simulation technique (RUSITEC) was used, which is a commonly accepted experimental model in investigations on ruminal fermentation. Changes in fermentation characteristics, as a result of changing the MS-to-GS ratio, were tested for linear and quadratic effects in order to identify possible associative effects. Prior to the in vitro incubation, feedstuffs were dried and ground. It was aimed to investigate in which way fermentation in the RUSITEC system is influenced by mean feed particle size. Therefore two milling screen sizes (MSS; 1 vs. 4 mm) were used in all diets and results on fermentation characteristic were tested for possible interactions of forage source and MSS. One incubation period lasted for 13 days (6 days adaption period, 7 days sampling period), and each treatment was tested in at least three replicates. Ruminal digesta, obtained from rumen-fistulated wether sheep, was used as the inoculum for starting the incubation. Diets were fed once daily to the RUSITEC system, and nylon feed bags remained for 48 h inside the fermentation vessel. A buffer solution, containing 15NH4Cl, was infused continuously into the vessel and the respective effluent was analysed for short chain fatty acids (SCFA) and NH3-N. Solid- and liquid- associated microbial fractions were isolated from the feed residues, the liquid inside the vessel and the effluent by differential centrifugation. The flow of microbial CP was quantified on the basis of N and 15N balances. The feed residues were analysed for crude nutrients and detergent fibre fractions and the respective degradation rates were calculated. OS and CP in the feed residues were corrected for the contribution of solid-associated microbes. The degradation of OM and fibre fractions, as well as amounts of NH3-N increased linearly with stepwise replacement of MS by GS. Degradation of CP was unaffected by diet composition, as well as total SCFA production. The degradation of OM and CP was higher in coarse milled (4 mm-MSS) than in fine milled (1 mm-MSS) treatments, accompanied by higher amounts of NH3-N and total SCFA. An improvement of growth conditions for some microbial groups, e.g. anaerobe fungi, was discussed. The amount of microbial CP increased linearly by the stepwise replacement of MS by GS, and was higher at 4 mm-MSS than at 1 mm-MSS. The amount of available N was assumed to advance microbial growth in the RUSITEC system. Efficiency of microbial CP synthesis was improved from 29 to 43 mg microbial N per g degraded OM by increasing the proportion of GS in the diet, but was unaffected by MSS. The N content and the profiles of amino acids of the three microbial fractions, as well as the ratio of solid- to liquid-associated microbes were affected by diet composition and MSS. Interactions of forage source and MSS were rare. However, the results indicated interactions between dietary factors and origin of microbial isolate on characteristics of microbial protein synthesis. In order to provide additional information on the nutritional value, the mixed diets were evaluated by two further methods. The total tract digestibility of crude nutrients was determined in wether sheep. The content of metabolisable energy was similar between diets and averaged 11.5 MJ per kg dry matter. The in vitro gas production was measured within 93 h by using a modified Hohenheim gas production test, providing information on kinetics and extent of ruminal fermentation. Cumulative gas production decreased with increasing proportion of GS in the diet. A negative effect of coarse milling on fermentation in the Hohenheim gas production test was confirmed. Across all diets gas production was delayed at 4 mm-MSS compared to 1 mm-MSS. The results from both approaches supported the findings of the RUSITEC study that a stepwise replacement of MS by GS led to a linear response in degradation of nutrients. As indicated by the gas production data, positive associative effects might only occur in the first hours after starting an incubation. When mixed diets are used effects cannot be clearly related to individual diet ingredients. Moreover, in the mixed diets interactions between soybean meal inclusion and forage source or feed particle size cannot be excluded. Therefore pure silages were incubated separately in the RUSITEC system in the second experimental series and three milling screens of different size were used (1, 4 and 9 mm). In accordance with the first experimental series, degradation of OM, fibre fractions and non-structural carbohydrates, production of NH3-N, as well as microbial CP flow and efficiency of microbial CP synthesis were higher in GS than in MS. A higher degradation of CP was found for MS than for GS, indicating interactions between forage source and soybean meal inclusion. An increase in MSS from 1 mm to 9 mm led to an improvement in the degradation of OM, CP and non-structural carbohydrates, particularly of starch in MS, as well as in the microbial CP flow for both silages. But the efficiency of microbial CP synthesis and microbial amino acid profile were less affected by MSS. In the second experimental series additionally the effect of available N on fermentation of MS was investigated. The supplementation of urea-N improved the degradation of non-structural carbohydrates, especially starch, but not that of fibre fractions in MS. The efficiency of microbial CP synthesis was increased from 26 to 35 mg microbial N per g degraded OM by urea-N supplementation to MS. The way of urea administration, either supplied together with the feed once daily or infused continuously by buffer solution, had only marginal effects on fermentation characteristics. It was concluded that microbial growth is improved by degradation of OM from GS compared to MS and by an increasing availability of N in the RUSITEC system. Meaningful associative effects of mixtures of MS and GS on ruminal fermentation characteristics are not likely to occur. However, transferability of results to other batches of MS and GS is limited, as high variations in chemical composition are known for both types of silage. Fermentation of MS- and GS-based diets in the RUSITEC system benefits more by coarse milling at MSS up to 9 mm than by fine milling at 1 mm-MSS. Consequently, variations in MSS and feed particle size distribution have to be taken into account when evaluating feeds by rumen simulation systems. The changes in composition and contribution of microbial fractions give indications to a shift in the microbial community as a result of variation of silage type and feed particle size, but further research on this aspect is needed. Moreover, the present results stated that the origin of the microbial samples is very important for measurements on microbial protein synthesis.
Microbiota responses to feed particle size, calcium concentration, and phytase supplementation in broiler chickens
(2026) Rubio-Cervantes, Ismael; Wolfrum, Stephanie; Siegert, Wolfgang; Rodehutscord, Markus; Camarinha-Silva, Amélia
This research aimed to investigate the modulation of broiler-chickens gut microbiota by dietary particle size (PS), exogenous phytase, and calcium (Ca) concentration. Eight experimental diets varied in PS (fine 222 µm (PF) and coarse 309 µm (PC)), Ca concentration (4.9 and 7.2 g/kg), and exogenous phytase (0 and 1000 FTU/kg). A total of 560 Ross 308 broiler chickens were allocated to 56 metabolism units at 7 days of age and randomly assigned to each diet (7 replicates per treatment). On days 22 and 23, the birds were slaughtered, and the digesta from the gizzard, ileum, and ceca were sampled and pooled on a metabolism unit basis. DNA extraction was followed by 16S rRNA gene amplicon sequencing. Thirteen amplicon sequence variants (ASV) were present across the gizzard, ileum, and ceca, most of which were assigned to Limosilactobacillus and represented a substantial share of the total relative abundance in each section, 86 % in the gizzard, 88 % in the ileum, and 30 % in the ceca. Six of these L. reuteri ASVs were significantly enriched by coarse particle feeding, suggesting strain-specific adaptation to enhanced phosphorus availability. In the ileum, Candidatus arthromitus (p < 0.001) and Rombustia (p < 0.05) showed a significant increase in relative abundance in PC compared to PF. Phytase supplementation reduced the relative abundance of Lactobacillus and Streptococcus (p < 0.05), while higher Ca concentration decreased that of C. arthromitus (p < 0.05). In the ceca, increases in the relative abundance of Anaerostipes (p < 0.05) and Clostridia vadin BB60 were found for PC diets compared to PF (p < 0.001). The addition of phytase and Ca also significantly affected several genera, albeit the variations were less than 1 %. Dietary PS, exogenous phytase, and Ca concentration modulated the gut microbiota, specifically influencing the abundance of key microorganisms like Candidatus arthromitus, Anaerostipes, and Clostridia vadin BB60, involved in phosphorus metabolism and overall broiler chickens' health.