The present invention generally relates to enteric-coated particles containing lactoferrin. More specifically, the present invention provides an enteric-coated particle comprising (or consisting essentially of): a) a core comprising (or consisting essentially of) an inert core-forming material selected from cellulose polymer, sugar, sugar alcohol, starch and carnauba wax; b) a first coating layer substantially covering the core and comprising (or consisting essentially of) b-1) lactoferrin, b-2) a pharmaceutically acceptable binder and optionally b-3) one or more other suitable excipients, such as a plasticizer; and c) a second coating layer substantially covering the first coating layer and comprising (or consisting essentially of) c-1) an enteric coating material, and optionally c-2) one or more suitable excipients, such as a plasticizer and/or an anti-tacking agent. The present invention further provides pharmaceutical compositions and oral dosage forms comprising one or more particles according to the present invention. [1]
Enteric-coated particles with CELLETS® and other starter beads
This formulations is based on starter beads, exemplary such as sugar, wax or microcrystalline cellulose (MCC). For the latter material MCC, specifically such as CELLETS® 100, CELLETS® 200, CELLETS® 350, CELLETS® 500, CELLETS® 700, or CELLETS® 1000 are mentioned. Through coating and layering of CELLETS® with excipients and the active, a modified release is obtained wherein at most 10% of lactoferrin is released from the particle within 120 minutes.
Document information
Document Type and Number: (“enteric-coated particles containing lactoferrin”)
Paulien Vanderghinste, An Bautil, Michael R. Bedford, Gemma González-Ortiz, Chris Lamberigts, Imran Aslam, Maarten Roeffaers, Christophe M. Courtin
Abstract
A promising strategy to support broiler health and performance in a sustainable way is the enhancement of microbial fibre fermentation in broilers. This fermentation mainly occurs in the caeca, but the actual particle size range that allows caecal influx has not yet been described. This study aimed to understand the physical limitations of caecal influx as a function of broiler age by using both solid and soluble markers. In the first trial, the caecal filter mechanism was studied by microscopically visualising the caecal entrance and measuring caecal lobe development and digesta particle size as a function of age (d 8 to 36) for 44 broilers (Ross 308) receiving a conventional wheat-based diet. In two consecutive trials, microcrystalline cellulose beads (100 to 700 μm) and a combination of fluorescent polystyrene beads (5 to 30 μm) and chromium-ethylenediamine tetraacetic acid (Cr-EDTA) were administered to 176 and 189 broilers, respectively, at different ages (d 8 to 36). Results showed that the actual caecal entrance diameter is significantly reduced due to a dense villi network acting as a filter for digesta inflow. This explains the size gap between the average digesta particle size (D50) of the ileum (451 to 322 μm), caeca (5 to 19 μm) and the outer diameter of the caecal entrance (2000 to 4000 μm) on d 8 to 36. In contrast to the caecal D50, cellulose beads of 700 μm already entered the caeca at 8 d of age, even though the general caecal influx of digesta particles larger than 100 μm seemed very limited. The caecal influx of the markers further exhibited large individual variation among birds. A maximum of 13.2% (d 9) and 4.3% (d 29) of the total administered soluble marker (Cr-EDTA) was detected in the caeca, 5 h after bolus administration. Both solid and soluble markers showed a larger concentration in the caeca at a young age compared to older ages (P < 0.01), possibly related to the limited caecal functioning early in life. These findings highlight the importance of carefully selecting the physical properties of fibres to be added as a function of age to further improve caecal fibre fermentation in broilers.
1. Introduction
Broiler production is in need of sustainable and cost-effective solutions to maintain the high performance and health status of broilers without the use of in-feed antibiotics. A promising strategy to improve gut health and performance is enhancing dietary fibre (DF) fermentation. Although DF is mainly known for its adverse effects on broiler performance due to its undigestible and antinutritional characteristics, more recent studies also show the potential beneficial effects of DF on health and performance (Kheravii et al., 2017; Pourazadi et al., 2020; Vermeulen et al., 2017). Even though these effects are still not completely understood, they seem to depend on the particle size and solubility of the DF addition. Coarse insoluble DF inclusions (> 1000 μm) can act as structural components in broiler diets, which can enhance gizzard functionality and retention time in the upper part of the gastrointestinal tract (GIT). As a result, increased nutrient utilisation and performance can be observed (Donadelli et al., 2019; Kheravii et al., 2017, 2018; Lentle et al., 2006, Pourazadi et al., 2020). In addition, DF fractions can be solubilised and subsequently fermented by microbiota in the broiler’s hindgut, resulting in the production of short-chain fatty acids. These short-chain fatty acids can act as an additional energy source for the broiler and can stimulate the growth of beneficial microbiota, as well as control the growth and expression of invasive genes of pathogenic bacteria. Providing more substrate suitable for beneficial fibre-fermenting bacteria by increasing the fermentable DF content in broiler diets can result in an additional decrease of pathogenic bacteria in the GIT by competitive exclusion (Singh & Kim, 2021; Vermeulen et al., 2017).
Most microbial fermentation of DF in poultry occurs in the caecal lobes, which are two blind sacs located at the junction of the ileum and colon. It is hypothesised that the digesta inflow into these lobes is restricted to very small particles, solutes and fluids, although no exact cut-off in particle size has been described (Svihus et al., 2013). The marked restriction of material that enters the caeca was illustrated by Son et al. (2002), who showed that only 18% of the total excreted dry matter and 17% of the total excreted water passed through the caeca. Several studies using digestibility and transit time markers provide an indication of the physical limitations of caecal influx and illustrate the vast difference between the influx of solid and soluble markers. Ferrando et al. (1987) observed that 500 to 2000 μm fibre particles could not enter the caeca in 8- to 10-week-old broilers, but 9% to 26% of the soluble marker chromium-ethylenediamine tetraacetic acid (Cr-EDTA) did enter the caeca in 1- to 3-week-old broilers in a separate experiment by this research group (Vergara et al., 1989). Similarly, Garçon et al. (2023) described a caecal inflow from 30% to 35% of the soluble digesta fraction in 25-day-old broilers based on the use of the soluble marker cobalt (Co)-EDTA. De Vries et al. (2014) further observed a minimal caecal influx of CrO3, linked to the solid phase of the diet, in contrast to the abundant presence of the soluble marker Co-EDTA in the caeca in 4-week-old broilers.
Although it has been hypothesised that only small particles and fluids can enter the caeca, it has also been shown that the addition of both coarse and fine fibre particles can alter caecal microbiota composition. The increase in beneficial fibre-fermenting species and the decrease in pathogenic species in the caeca after the inclusion of fine fibre particles (80 to 300 μm) has been described by Boguslawska-Tryk et al. (2015), De Maesschalck et al. (2019) and Vermeulen et al. (2017). The modification of caecal microbiota by including coarse (fibre) particles (557 to 3000 μm) has also been demonstrated by Pourazadi et al. (2020) and Jacobs et al. (2010). It is still unclear whether these fibre particles as such can truly enter, or that only the solubles originating from the DF fraction end up in the caeca and alter the microbiota composition.
A promising strategy to increase the beneficial effects of DF on broiler health and performance is to enhance the microbial fermentation of DF in the caeca. Due to the observed physical limitations of caecal influx and the lack of a known threshold in particle size for caecal entry, a better understanding of the mechanisms of caecal influx is required. It is hypothesised that the marked restriction of the caecal influx of digesta is mainly due to the extensive network of villi present at the caecal entrance (Svihus et al., 2013). Histological research on the caecal lobes in broilers, layers, geese and quail has shown important differences in microstructures, such as villi, between the different sections (proximal, middle and distal). Well-developed villous structures are abundantly present in the proximal part of the caecal lobes, whereas more fold-like structures can be seen in the middle part and little to no folds are present in the distal part (Chen et al., 2002; Majeed et al., 2009; Pandit et al., 2018; Svihus et al., 2013). Based on this trend of extensive villi development towards the opening of the caecal lobes, a dense network of villous structures can be expected at its entrance. This network could be partly responsible for the filtering mechanism at the caecal entrance by acting as a sieve for the ileal digesta (Clench & Mathias, 1999; Fenna & Boag, 1973; Svihus et al., 2013). In our research group, it was observed that caecal lobe weight and the size of the opening increases with broiler age, which could indicate that the particle size threshold for caecal entry also increases with age (Bautil et al., 2021). Research on the effect of age on the mode of action of this caecal filter mechanism and its histological structure in broilers is still very limited.
As outlined above, the actual size range of particles that can enter the caeca has not yet been described. In addition, multiple studies have already shown that both fine (< 300 μm) and coarse (> 1000 μm) fibre additions can affect the composition and metabolic functioning of the caecal microbiota and the resulting fermentation (Boguslawska-Tryk et al., 2015; De Maesschalck et al., 2019; Jacobs et al., 2010; Pourazadi et al., 2020; Vermeulen et al., 2017). It remains, however, unclear if these fibre additions enter the caeca maintaining their initial particle size, or that they affect the caecal functioning through other mechanisms. Hence, the aim of the current study is to acquire a deeper understanding of the physical limitations of caecal influx. This can enable valuable insights to explore new strategies to further increase DF fermentation in poultry.
2. Materials and methods
2.1. Animal ethics statement
The broiler trials were approved by the Ethical Committee for the experimental use of animals of the KU Leuven under accession number P140/2020.
2.2. Broiler Housing, Diets and Sampling
Three consecutive broiler trials were conducted to study the physical limitations of caecal entrance by means of particle size in broilers. In the first part of this research, the size of the digesta particles present in the caeca was quantified for broilers fed a conventional wheat-based diet (control trial). In the second part, solid and soluble inert markers were administered to broilers in two trials to explore the particle size that allows caecal influx as a function of age.
For all three trials, conventional heating, ventilation and lighting conditions for broiler housing were applied (Aviagen, 2018). The housing temperature was set at 34 °C on d 1, gradually decreased to 21 °C at d 27 and thereafter kept constant at this temperature. The light schedule consisted of 23 h light and 1 h darkness (23:00 to 00:00) from d 1 to d 7, followed by a schedule of 18 h light and 6 h darkness (23:00 to 05:00) until the end of the trial. All broilers were kept in floor pens with fresh wood shavings and received water and feed ad libitum. Inspection of the supply of water and feed, housing conditions, health status of the broilers and mortality was carried out daily. The same basal wheat-based diet was used for the three trials (Table S1). This diet did not contain fibre-degrading enzymes but did include phytase.
2.2.1. Control trial: caecal development and digesta particle size as a function of age
For the first trial, 44 broilers (Ross 308) at one day old were purchased from a commercial hatchery (Belgabroed NV, Merksplas, Belgium) and raised in one floor pen. At d 8, 15 and 36, a total of 18, 12 and 6 broilers, respectively, were sacrificed by electronarcosis followed by decapitation. The chyme and digesta of the gizzard, duodenum-jejunum, ileum (the section between Meckel’s diverticulum and ileocaecal intersect) and caeca were collected by gentle finger stripping of the segments and pooled per 3, 2 and 1 broilers on d 8, 15 and 36, respectively to obtain 6 replicate pools of digesta at each sampling age for further analysis. The caecal lobes and the ileocaecal intersect of each broiler were also collected. Digesta samples and caecal lobes were stored at -20 °C and the intersect at -80 °C until further analysis. The weight and length of the caecal lobes and the circumference of the caecal entrance (using a ruler) were measured during sampling.
2.2.2. Cellulose bead trial (large solid marker)
For the second trial, 176 male broilers (Ross 308) at one day old were purchased from a commercial hatchery (Belgabroed NV, Merksplas, Belgium) and randomly divided over 4 floor pens. Each pen was assigned to one dietary treatment and contained 44 broilers. The dietary treatments consisted of the basal wheat-based diet (Table S1) supplemented with 1% microcrystalline cellulose beads (Cellets®, Ingredientpharm, Pratteln, Switzerland) of one of 4 different particle sizes: 100, 200, 300, and 700 μm. At d 8, 15, 25 and 36, a total of 18, 12, 6 and 6 broilers, respectively, per dietary treatment were sacrificed by electronarcosis followed by decapitation. Digesta was pooled per 3, 2, 1 and 1 broilers on d 8, 15, 25 and 36 respectively to obtain 6 replicate pools of sufficient digesta at each sampling age for further analysis. Digesta collection and measurement on the caecal lobes were executed as described for the control trial (2.2.1).
For the third consecutive trial, a total of 105 male broilers (Ross 308) at one day old were purchased from a commercial hatchery (Belgabroed NV, Merksplas, Belgium) and randomly divided over floor pens. On d 9 and d 29, a marker bolus of 1 mL was administered through oral gavage to 70 and 35 broilers, respectively. The bolus administration started in the morning, resulting in an administration starting time 9 or 4 h after the dark period at d 9 or d 29, respectively. No fasting period was applied beforehand to ensure conventional bowel movements, caecal filling and transit time. The bolus contained the soluble marker Cr-EDTA (954 μL/mL) and three types of solid fluorescent polystyrene microbeads (Spherotech™, Gentaur, Kampenhout, Belgium) with average particle sizes (D50) of 5 μm (1%, wt/vol), 15 μm (0.2%, wt/vol) and 30 μm (1%, wt/vol) with a concentration of respectively 9, 9 and 26 μL/mL in the bolus. On d 9 and d 29, respectively, 14 and 7 broilers per time point were sacrificed by electronarcosis followed by decapitation at 1, 3, 5, 10 and 24 h after the bolus administration to collect 7 replicate digesta pools per time point. At d 9, digesta was pooled per two broilers to obtain a sufficient amount for further analysis. Chyme and digesta of the gizzard, duodenum-jejunum, ileum (the section between Meckel’s diverticulum and ileocaecal intersect) and caeca were collected by gentle finger stripping the segments. The digesta and the emptied parts of the GIT were stored at -20 °C until further analysis.
2.3. Measurements on intestinal and digesta samples of the control trial
2.3.1. Microscopic visualisation of the caecal entrance
The tissue of the caecal entrance was embedded according to an adjusted method of Chen et al. (2002). Sections of the caecal entrance of each sampling age (d 8, 15, 36) were fixed in a 3.0% paraformaldehyde-1.0% glutaraldehyde solution for 16 h, after which they were washed with saline solution (0.9%) and cut into 5-mm tissue slices with a scalpel to obtain minimally 2 slices per caecal entrance. The tissue slices were dehydrated in ethanol series with increasing concentration (70% to 100%), cleared with toluene (99.8%), and then embedded in paraffin. These paraffin blocks were cut into 8-μm thick sections with a Leica RM2255 microtome (Leica Biosystems Nussloch GmbH, Nussloch, Germany). Sections were subsequently stained with hematoxylin (6 min) and eosin (30 s) for histological analysis. Dimensions of the caecal opening were measured using light microscopy (Nikon Eclipse 80i microscope, Nikon Inc., New York, USA) and ImageJ.
2.3.2. Determination of diet, ileal and caecal digesta particle size distribution
The particle size distribution of the diets (starter, grower, finisher) and of the ileal and caecal digesta at each sampled age (d 8, 15, 36) was measured with a Laser Diffraction Particle Size Analyzer LS 13 320 (Beckman Coulter Inc, Indianapolis, IN, USA). This device can measure particle sizes ranging from 0.375 to 2000 μm and assumes that all particles are spherical to generate a volumetric particle size distribution. Diets and ileal digesta were sieved through a 1000-μm mesh prior to this analysis due to technical restrictions (i.e. limit in particle size range) of the device. The volumetric D50 was also calculated for each measurement.
2.4. Detection and quantification of markers in digesta samples
2.4.1. Quantification of cellulose beads (large solid marker)
Ileal and caecal digesta samples of d 8, 15, 25 and 36 of broilers fed the diets enriched with cellulose beads were microscopically screened for the presence of the beads. Prior to bead screening, digesta samples were diluted as follows: 0.2 mL of caecal digesta (50.0 mg) of each replicate pool was diluted in 2.0-mL demineralised water in triplicate. Then, 0.2 mL of these solutions was placed on a microscopy glass to screen for cellulose beads. This microscopic screening was performed in triplicate for each solution to determine the presence of 100, 200 and 300 μm beads (10× magnitude, Nikon Eclipse 80i microscope, Nikon Inc., New York, USA). Due to the large size of the 700 μm beads, their presence was determined by visually screening the diluted digesta samples.
2.4.2. Detection of fluorescent polystyrene beads (small solid marker)
The collected digesta samples were screened for the presence of fluorescent polystyrene beads in collaboration with the Roeffaers Lab (KU Leuven, Belgium). After lyophilisation and grinding of ileal and caecal digesta samples of broilers that received the marker bolus, 50 mg digesta of each sample was suspended in 1 mL demineralised water. 250 μL of this solution was mixed with 250 μL agar and poured into a 9.4 mm × 10.7 mm × 9.3 mm well of an Ibidi μ-Slide 8 well for visualisation with a Leica TCS SP8X (Leica Microsystems GmbH, Germany). Three excitation and emission wavelength combinations were used simultaneously to detect the fluorescent polystyrene beads based on the optimal excitation and emission wavelength ranges of each bead type (wavelengths provided in Supplementary Table S2). Tile scans of the complete wells were made by capturing images of 517μm × 517 μm and a z-section depth of 1.2 μm (405 nm excitation) or a z-section depth of 1.7 μm (590 nm excitation) with a 10x magnification objective lens using Leica Application Suite X software (LAS X, Leica Microsystems GmbH, Germany). Image processing and bead counting was done through LAS X software and ImageJ, after which the number of beads on each image was summed to obtain a total bead count per tile scan and digesta replicate pool. Seven replicate pools of ileal and caecal digesta samples of d 8 and 25 of the control trial (2.1.1) were utilised in this analysis as control samples to validate the described bead detection method.
2.4.3. Quantification of Cr-EDTA (soluble marker)
Ileal and caecal digesta samples of broilers that received the marker bolus were lyophilised, ground, and subjected to an acid closed vessel digestion. Two reference samples of 100 mg Beech BR100 and three negative controls were included in each analysis. Eight milliters HNO3 (69%) was added to digesta samples (100 mg) of each replicate pool of both ages (d 9 and d 29). After a predigestion of 30 min, the samples were digested in a MARS 6 microwave (CEM, Matthews, North Carolina, United States) in closed MARSXpress Teflon tubes for 70 min at 180 °C (including 25 min warm-up and 25 min cool-down time). Next, 42-mL Milli-Q water was added to each digested sample. The samples were further diluted 4-fold with Milli-Q water, after which the solubilised Cr was measured through inductively coupled plasma spectrometry (ICP-MS, Agilent 7700x, Agilent Technologies, Santa Clara, California, United States). This resulted in an ileal and caecal Cr concentration (mg Cr/kg dry digesta) per replicate, which was converted to the total Cr content in the ileum and caeca based on the total digesta dry weight collected per replicate during sampling. The percentage of Cr found in the caeca compared to the total administered Cr in the bolus was also calculated.
2.5. Statistical analysis
Statistical analyses were performed using JMP Pro 16 Software and R Statistical Software (v4.0.5; R Core Team 2021). The normality of all datasets was evaluated through a density plot and quantile-quantile plot. The means of full caecal lobe weight, lobe length and caecal entrance diameter were calculated using sample sizes of 18, 12 and 6 broilers, respectively, at d 8, 15 and 36, due to the limited digesta sample size available from the younger birds. Broilers that showed signs of intestinal disease were excluded from this dataset. Significant differences in the mean full caecal lobe weight, lobe length and D50 of caecal digesta (n = 6) between age groups were identified by performing a one-way ANOVA and significantly different means were further identified using a Tukey’s test. Differences between mean caecal entrance diameter and cellulose bead counts in digesta (n = 6) were identified using a Wilcoxon Rank Sum test due to the non-normality of the data. Significant differences between mean total fluorescent bead counts in ileal and caecal digesta of the treated broilers compared to the control broilers (n = 7) were identified by performing a one-way ANOVA and significantly different means were further identified using a Student’s t-test. Significant differences in mean ileal and caecal Cr concentrations between the measured time points and in ranges of caecal influx ratio of Cr at different broiler ages (n = 7) were identified using the Wilcoxon Rank Sum test. Differences between means were considered significant at P < 0.05 and interpreted as a trend at 0.05 ≤ P ≤ 0.10.
3. Results
3.1. Control trial: caecal development and digesta particle size as a function of age
3.1.1. Development of caecal lobes and entrance as a function of age
The evolution of caecal lobe weight, length and circumference of the caecal entrance measured on fresh caecal lobes are shown in Fig. 1. The average weight of both full caecal lobes increased with age from 1.58 g (± 0.40) on d 8 to 12.18 g (± 5.25) on d 36 (P < 0.001). This corresponded to a relative weight of 0.87 g/100 g (± 0.30) BW on d 8 and 0.46 g/100 g (± 0.20) BW on d 36. The average length of the caecal lobe increased from 7.1 cm (± 0.7) on d 8 to 17.6 cm (± 2) on d 36 (P < 0.001). The average diameter of the caecal entrance measured on fresh samples increased from 0.2 cm (± 0.04) on d 8 to 0.4 cm (± 0.05) on d 36 (P < 0.001). Fig. 2 shows the stained sections of the embedded caecal entrances at d 8, 15 and 36. The visualisation of the caecal entrance showed that the true inner diameter of the entrance is markedly reduced due to additional tissue layers inside this entrance at all studied ages. These tissue layers consist of a submucosa layer with protrusions towards the inside of the caeca, on which a villi layer is attached. The average of the geometric mean diameters of the embedded caecal entrances measured 0.1133 cm (± 0.0224), 0.1943 cm (± 0.0457) and 0.2143 cm (± 0.0679) on d 8, 15 and 36, respectively.
Fig. 1. Violin plots of the length (A), entrance diameter (B) and full weight (C) of fresh caecal lobes of the control trial measured during sampling at d 8 (n = 18), d 15 (n = 12) and d 36 (n = 6). Dots represent the mean value per age, vertical lines represent the Q1 to Q3 boxplot quantiles. Different letters indicate a significant difference between mean values of age groups (P < 0.05).
Fig. 2. Microscopic images of 8-μm thick sections of caecal entrance tissue embedded in paraffin and stained with hematoxylin and eosin, from caecal lobes of the control trial collected at d 8 (A, B, C), d 15 (D, E, F) and d 36 (G, H, J). The muscular outer layers are stained in light pink, the inner submucosa and villi network are dark purple.
3.1.2. Ileal and caecal digesta particle size distribution as a function of age
The average diet, ileal and caecal particle size distribution of broilers fed a wheat-based diet as a function of age is shown in Fig. 3. There was a significant reduction in particle size as digesta moved from the ileum to the caeca at all studied ages. The D50 of the ileal digesta on d 8, 15 and 36 was 451 μm (± 49), 322 μm (± 25) and 409 μm (± 24), respectively, in comparison to the diameters of the caecal digesta of 5 μm (± 3), 9 μm (± 2) and 19 μm (± 8) at the same age. The D50 of the caecal digesta on d 8 was smaller than on d 36 (P < 0.001). On d 8 and d 15, 70% of the caecal digesta particles were smaller than 10 μm. On d 36, this upper limit for 70% of the particles increased to 30 μm. However, particles up to 400 μm were also present in caecal digesta of d 8. The geometric mean diameters of the caecal entrance (1133 to 2143 μm) vastly exceeded the caecal digesta D50 (5 to 19 μm) at every studied age.
Fig. 3. Average volumetric particle size distribution of the diets, ileal and caecal digesta of the control group collected at d 8, 15 and 36 (n = 3 for each diet, n = 6 per age group for digesta), expressed as volume percentage. Orange lines represent the diets, blue lines the ileal digesta and green lines the caecal digesta. Dotted, dashed and solid lines represent the particle size distribution at an age of respectively 8, 15 and 36 d.
3.2. Detection and quantification of markers
3.2.1. Detection and quantification of cellulose beads (large solid marker)
All sizes of cellulose beads were found intact in the feed, along the GIT and in the excreta, demonstrating their inertness and suitability as particle size markers in broilers (Fig. S1). Individual body weight and gut development parameters were also not significantly affected by the inclusion of the cellulose beads. Fig. 4 shows the cellulose bead concentration in the caecal digesta for each screened replicate pool per age and per bead size. All sizes of cellulose beads (100 to 700 μm) were detected in at least one replicate pool at all studied ages (d 8 to 36), although the bead concentration in the caeca markedly varied between the replicate pools. A tendency towards higher bead concentrations at d 8 compared to d 36 could be observed irrespective of bead size, and this age effect was significant for the 100 μm and 300 μm beads (P < 0.001). As the bead count per gram of beads differed for each bead size (Table S2), the bead concentrations in digesta could not be compared directly between the different bead sizes. The ratio of the bead concentration in the caeca over that in the ileum is also shown in Fig. 4 per age group and bead size. This ratio indicates the caecal influx of the beads and ranged from 0.6% to 55.9% over all treatments and ages, showing large variability between biological replicates. The ratio was not affected by bead size or broiler age.
Fig. 4. Beeswarm plots showing the effect of bead size (A: 100 μm [1739 beads per g feed], B: 200 μm [1089 beads per g feed], C: 300 μm [556 beads per g feed], D: 700 μm [55 beads per g feed]) on bead concentration in caecal digesta of broilers at different ages (d 8, 15, 25 and 36, n = 6 per age group). Points represent the bead count per g digesta of each biological replicate and a horizontal line indicates the average bead count per g digesta per age. Different letters indicate a significant difference in mean bead concentration between age groups (P < 0.05). Above each beeswarm, the ratio of bead concentration in the caeca compared to the ileum is given per bead size and age.
3.2.2. Detection and quantification of fluorescent polystyrene beads (small solid marker)
The total count of fluorescent polystyrene beads of 5 μm in digesta of the treated broilers 1 h after bolus administration only differed from the control broilers for the ileal digesta samples at the youngest age (d 9) (P < 0.001), as shown in Fig. 5. No significant differences in ileal (d 29) and caecal (d 9 and d 29) counts of 5 μm beads between the treated broilers and the control were detected. The low concentrations of the beads in the administered bolus, especially of the 15 μm and 30 μm beads due to their larger particle size, hindered their detection in all types of digesta samples. Strong autofluorescence signals of other digesta particles were observed in both the control and bead-treated ileal and caecal digesta samples, which further complicated the detection of the beads (Fig. S2 and Fig. S3).
Fig. 5. Boxplots of total counts of 5-μm fluorescent polystyrene beads per tile scan by ImageJ for ileal digesta on d 9 (A), ileal digesta on d 29 (B), caecal digesta on d 9 (C) and caecal digesta on d 29 (D) of broilers 1 h after bolus administration compared to control broilers (n = 7 per age group). Different letters indicate a significant difference in mean bead count between treatments (P < 0.05).
3.2.3. Detection and quantification of Cr-EDTA (soluble marker)
Fig. 6 shows the total Cr content in the ileal and caecal digesta over time at d 9 and d 29 for each replicate pool and the average per age and time point, starting 1 h after bolus administration. The first presence of Cr in the ileum and caeca was already observed 1 h after bolus administration on both d 9 and d 29. The ileal Cr content at this first time point was higher at d 9 compared to d 29 (P = 0.022), but this age effect disappeared at later time points in the ileum. In contrast, the caecal Cr content remained higher at d 9 compared to d 29 at time points 3 h (P = 0.001) and 5 h (P = 0.004). The maximal Cr content was observed 3 h after bolus administration in the ileum at both ages, while a first maximal caecal Cr content was observed at the 5 h time point for both ages. The Cr content in the caeca compared to the total administered Cr in the bolus ranged from 3.5% to 13.2% (d 9) and from 1.7% to 4.3% (d 29) at the 5 h time point, with higher values at a younger age (P = 0.004). Relatively large amounts of Cr were retained in the caeca for up to 24 h at both ages, with a large variation between biological replicate pools. The total Cr content in the ileal and caecal digesta 1 h and 3 h after bolus administration and the calculated caecal influx ratio are shown in Fig. 7. Due to the high variation in both ileal and caecal Cr content, the results are shown per replicate pool. The unexpected mortality of three broilers between the period of bolus administration and sampling resulted in 6, 5 and 6 replicate pools instead of 7 in Fig.7 for the time points 1 h and 3 h (d 9) and 1 h (d 29), respectively. The ratio of the Cr content in the caeca compared to the ileum at the 1 h time point can indicate the caecal influx of Cr or the flow of Cr from the ileum into the caeca. This ratio varied greatly between replicate pools due to variations in both the ileal and caecal Cr content. The caecal influx ratio tended to increase with age from 0.3% to 4% on d 9 to 0.8% to 75% on d 29 (P = 0.055). One replicate pool on d 29 already had a higher Cr content in the caeca compared to the ileum at the 1 h time point, resulting in a caecal influx ratio above 100% (430%). At the 3 h time point, two replicate pools showed a caecal influx ratio above 100%.
Fig. 6. Beeswarm plots of the total Cr content in ileal (A: d 9, B: d 29) and caecal (C: d 9, D: d 29) digesta collected at 1, 3, 5, 10 and 24 h after bolus administration at d 9 and d 29 (n = 7 per time point and per age group). Points represent the total Cr content (mg) per biological replicate and a horizontal line indicates the average per time point.
Fig. 7. Dumbbell plots of the Cr content (mg) in caecal (black dots) and ileal (grey squares) digesta collected 1 and 3 h after bolus administration at d 9 (A, B) and d 29 (C, D) of each biological replicate, corrected for digesta dry weights (n = 5 to 7 per age group). The ratio of the Cr content in the caeca compared to the ileum per biological replicate is given as percentage above each measurement.
4. Discussion
The evolution of the broiler’s caeca and the caecal digesta particle size distribution with age were studied as a first step to reveal the physical restrictions of caecal influx. An overall increase in caecal dimensions with age was observed, such as the enlargement in caecal diameter, lobe length and full lobe weight from d 8 to d 36. This illustrates the rapid development of the caeca with age and can also indicate an increase in caecal influx of digesta and fermentation capacity with age (Svihus et al., 2013). The relative full caecal lobe weights and dimensions measured in this study correspond to previous findings in literature when broilers were offered a wheat-based diet (Bautil et al., 2021). The observed increase in caecal weights and dimensions could also be expected based on other studies that recorded caecal development with age in broilers and other young poultry species (AbuAli et al., 2019; Martínez et al., 2021). The sections of the embedded caecal entrances displayed a similar increase in diameter with age, but more importantly, showed that the actual inner diameter of the caecal entrance, relevant for digesta influx, is markedly reduced due to a network of submucosa protrusions and villi. Additional mucus layers can also be expected to be part of this network but were probably lost during the embedding procedure. The visualisation of this network supports the hypothesis that the numerous villi at the caecal entrance act as a filter for incoming digesta particles, as described by Clench & Mathias (1999), Fenna & Boag (1973) and Svihus et al. (2013). This filtering effect was further confirmed by the large shift in D50 from the ileal digesta (409 to 451 μm) to the caecal digesta (5 to 19 μm). The lack of difference between the diet and ileal digesta particle size is mainly due to the required pre-sieving step before laser diffraction analysis. The presence of the villous network at the caecal entrance also explains the large size gap between the measured outer diameter of the caecal entrance (0.2 to 0.4 cm) and the actual D50 of the digesta inside the caeca at all studied ages. The villous network already seemed to be developed in the first week after hatch, but its firmness could however greatly vary with age. It appeared to be more brittle and was harder to visualise in detail at d 8 compared to d 15 and d 36, which can indicate a decreased filtering capacity of the villous network at a younger age. However, the smaller size of the caecal entrance tissue on d 8 compared to d 15 and d 36 could also have increased the difficulty of the visualisation procedure in general. Nonetheless, it is clear that this villous network at the caecal entrance restricts digesta inflow at all studied ages.
Based on the increase in the caecal physiological parameters and the caecal digesta D50 with age, the size of digesta particles that can pass through the caecal filter can also be expected to increase with age. The actual particle size range that allows caecal influx as a function of age was assessed by means of solid and soluble markers in two consecutive broiler trials. The microcrystalline cellulose beads that were used as the large solid marker in this study seemed to be a suitable marker in the broiler’s GIT due to their inertness along the GIT and the absence of an effect on individual body weights and gut development parameters. As previously confirmed in other studies, the soluble marker Cr-EDTA also seemed to be a suitable marker due to its inertness and accurate detection in the digesta (Iji, 2007; Vergara et al., 1989). The first appearance of Cr in the ileum and the caeca in this study was already detected within 1 h after bolus administration. This fast transit of liquid markers to the small intestine corresponds to the report regarding early marker appearance in broilers and quail by Fenna & Boag (1973) and Vergara et al. (1989). The direct administration of the bolus into the crop through the oral gavage technique used in the current study may have additionally accelerated the passage of the markers to the other GIT parts compared to marker intake through regular feeding. The major fraction of Cr was found after 3 and 5 h respectively in the ileum and caeca, corresponding to the expected digesta transit times in these GIT parts (Svihus & Itani, 2019). However, at these later time points, which correspond to the expected time for digesta to reach the caeca, the caecal Cr content already exceeded the ileal Cr content in multiple broilers at d 9, indicating an accumulation of Cr in the caeca and an evacuation of ileal content. The frequency of caecal emptying in broilers is estimated to be every 2 to 8 h based on previous own research (data not shown). Based on these findings, the data from the 1 h time point seemed the most reliable in estimating the flow of markers from the ileum to the caeca, with a minimal effect of caecal accumulation or retention of the markers at d 9. The same time point was used at d 29 to allow a correct comparison between both ages. The caecal influx ratios at the 3 h time point are also shown in Fig. 7, but may already be affected by caecal emptying and accumulation that are still poorly understood. To study caecal marker retention, all time points were taken into account (Fig. 6). Following this reasoning, the detection of the fluorescent polystyrene beads was also performed on the digesta collected 1 h after bolus administration for the estimation of their caecal influx. These fluorescent polystyrene beads were used as small solid markers but seemed less suitable for this study, as only the 5 μm beads were detected in the ileal digesta on d 9 and no beads were detected in the caecal digesta. This mainly seems due to the low administered concentration of the beads (9 to 26 vol % of bead solutions in the bolus), regarding the limited amount of caecal influx of small particles and fluids measured in this paper and previous studies (Garçon et al., 2023; Vergara et al., 1989). In addition, the beads were difficult to detect in the digesta matrix due to their similar size to digesta particles and the interference of the autofluorescence of feed and digesta compared to the relatively low administered bead concentrations. Using higher bead concentrations in the oral bolus and fluorescent coatings that do not overlap with the autofluorescent signal of feed and digesta could improve their suitability as a marker for studies on the broiler’s caeca. Preliminary screening of the samples obtained at later time points than 1 h did not show a better detection of fluorescent beads and were hence not analysed for this marker type.
An overall low caecal influx ratio was observed for both the solid and soluble markers, although this ratio varied between replicate pools. The average caecal influx ratio of the cellulose beads was only 5%, with no significant effect of age or bead size. Despite this low influx, the presence of cellulose beads with particle sizes up to 700 μm in the broiler’s caeca is remarkable, given that only 1% to 15% of the caecal digesta particles of the unsupplemented broilers were larger than 100 μm, and no particles larger than 500 μm were detected. The cellulose beads, however, differ from other digesta particles and from the native cellulose already present in the feed due to their dense microcrystalline structure, spherical shape and smooth surface. This might have facilitated their caecal entry, for example, by pushing through the villous network instead of being withheld as expected for light, non-spherical digesta particles such as wheat bran. The wide range of the caecal influx ratio of the cellulose beads (2% to 56%) over the different replicate pools shows that a high caecal marker concentration of these beads could also be achieved. A similar broad caecal influx range with a high maximum was observed for the soluble marker (0.3% to 75%) 1 h after bolus administration. It is important to note that the reported influx ratios of the cellulose beads, administered through continuous feeding, can be an overestimation if the potential accumulation of markers in the caeca over time is considered (Svihus et al., 2013; Vergara et al., 1989). On the other hand, the caecal influx ratios of the soluble marker can be an underestimation as these were calculated based on marker contents measured 1 h after marker administration. Although using this 1 h data minimizes the effect of caecal emptying and accumulation, later time points are considered more biologically relevant regarding caecal transit time (Svihus & Itani, 2019). These later time points were taken into account when studying caecal retention of the markers, but were not suitable for the calculation of the caecal influx ratio as outlined above. Aside from the infrequent caecal emptying and the possible accumulation of material in the caeca, the inflow of material into the caeca is assumed to be non-continuous and can additionally complicate the measurement and interpretation of caecal influx. A vastly higher caecal influx ratio of the soluble marker compared to the solid marker could have been expected based on the reports by De Vries et al. (2014), Svihus et al. (2013) and Vergara et al. (1989), but was not observed in this study. The absence of this difference may be caused by a greater accumulation of the cellulose beads in the caeca due to their larger size which may facilitate their retention in the caeca once they have entered, and their administration through continuous feeding instead of through a single bolus as used for the soluble marker. Aside from the caecal influx ratio, the maximal Cr content found in the caeca compared to the total amount of administered Cr can indicate the extent to which the soluble digesta fraction can enter the caeca, which ranged from 1.7% to 13.2% in this study, 5 h after bolus administration. Although these values align with the few other studies that quantified caecal influx in broilers, the possible accumulation and infrequent filling and emptying of the caeca should be taken into account for a correct interpretation. It is described that caecal digesta dry matter accounts for 18% of the total excreted dry matter in broilers and that 9% to 35% of the orally administered soluble marker Co-EDTA was found in the caeca, depending on broiler age (Garçon et al., 2023; Son et al., 2002; Vergara et al., 1989). So, despite the non-continuous caecal inflow and outflow dynamics complicating the interpretation of the obtained marker data, this paper confirms that even the caecal influx of the liquid fraction seems very limited. Together with the results on caecal digesta particle size distribution, the current results suggest that a particle size of less than 100 μm is required to achieve maximal caecal access. Although larger particles have also been demonstrated to affect caecal fermentation and microbiota (Boguslawska-Tryk et al., 2015; De Maesschalck et al., 2019; Pourazadi et al., 2020; Vermeulen et al., 2017), these results indicate that they will only enter the caeca in very limited quantities. Hence, despite the use of different marker types and time points in this study, the exact quantification of the fraction of ileal digesta particles that can actually pass the caecal filter to enter the caeca is still hindered by the complex caecal filling and emptying mechanisms and the important role of broiler age. Aside from particle size, other physicochemical characteristics such as solubility, viscosity and molecular weight are also expected to affect the caecal entrance of digesta (Svihus et al., 2013). However, this study did highlight the importance of particle size for caecal influx and provides an indication of the particle size range allowing this caecal influx, within the studied size ranges of the used solid (100 to 700 μm) and soluble markers. These new insights can be of use to further improve the maximal fibre fermentation capacity in the caeca.
In addition to particle size, broiler age also seemed to be an important factor when studying the physical aspects of digesta influx into the caeca. The caecal concentration of 100-μm and 300-μm beads, the total caecal Cr content at time points 3 and 5 h and the maximal percentage of Cr in the caeca compared to the total administered Cr were all higher at a younger age (d 8 to 9) compared to an older age (d 29 to 36). This contradicts the observed increase in caecal dimensions and caecal digesta D50 with age, as well as the increase in the caecal influx of Cr with age as observed by Vergara et al. (1989). The ileal and caecal Cr contents as a function of time (Fig. 6) can indicate a two-sided effect of age on the transit time and retention time of this marker in the GIT. Firstly, the higher ileal Cr content at d 9 compared to d 29 1 h after bolus administration may imply that the precaecal transit time of this marker is shorter at d 9 compared to d 29. Secondly, the increased caecal Cr concentrations at a younger age can be due to the faster passage of liquid digesta material at a younger age as confirmed for the ileal data above, which was also seen by Vergara et al. (1989) for the total tract transit time of Cr-EDTA. However, these authors assigned this age effect to the increase of caecal influx with age, while the current study shows that the passage is already faster in the GIT parts prior to the caeca. Similar to the liquid Cr marker, the results of the cellulose beads show a tendency towards a higher caecal marker concentration at a young age compared to an older age. These higher caecal marker concentrations at a younger age compared to an older age could also be the result of a greater caecal retention of the marker in younger birds. Other studies have shown that digesta can remain in the caeca for longer than 12 or 24 h, leading to increased retention times of certain markers (Garçon et al., 2023; Hinton et al., 2000; Vergara et al., 1989; Warriss et al., 2004). This aligns with the high caecal Cr concentrations observed 24 h after bolus administration. In addition, a longer transit time of the cellulose beads in the GIT at a young age compared to an older age was observed in an extra transit time experiment (data not shown), which may also be attributed to greater caecal retention of this relatively large solid marker. This means that the increased marker concentrations at a young age compared to an older age can reflect their accumulation in the caeca and may indicate a more restricted caecal outflow early in life rather than a more restricted inflow at an older age. This more restricted outflow may result from less contractile activity of the caeca lobes in young birds, which can be related to the previously reported limited functioning of the caeca at a very young age. For example, Svihus et al. (2013) expect that the full fermentation capacity of the caeca is not reached before d 28, which is supported by observations of increased levels of fermentation products formed in the caeca with increasing broiler age (Fischer, 2003; Lee et al., 2017). The increase in fibre fermentation capacity with broiler age is also reported by Bautil et al. (2019), where increased solubilisation and fermentation of arabinoxylan was measured in broilers at 21 d compared to 10 and 5 d. In addition, the bacterial density in the caeca has been observed to increase rapidly from hatch until 7 d, after which the density remains the same up to 30 d (Apajalahti et al., 2004). Similarly, the caecal microbial composition was observed to vary significantly in the first weeks of life (d 1 to d 10) but stabilised from 11 days on (Van Der Wielen et al., 2002). So, the seemingly longer retention of substrates in the caeca of younger birds is possibly a physiological adaptation to the underdeveloped caecal fermentation capacity early in life. Despite the higher Cr content in the caeca at a younger age compared to an older age at time points 3 and 5 h, the caecal influx ratio of Cr calculated 1 h after bolus administration did increase with age from 0.3% to 4% on d 9 to 0.8% to 75% on d 29. This indicates a higher influx of the liquid fraction from the ileum into the caeca at an older age, if caecal accumulation of the marker can be neglected at the 1 h time point. This age effect correspond to the trend observed by Vergara et al. (1989) using the same marker. The caecal influx ratio of the cellulose beads was not affected by age, possibly due to the large biological variation, caecal accumulation of the beads over time or the different physiochemical characteristics of the beads compared to digesta particles as described above. In conclusion, the results indicate that caecal influx of the soluble fraction can increase with age, whereas the accumulation of both the solid and soluble fraction in the caeca seems greater at a young age (d 8 or 9) compared to an older age (d 29 or 36). This accumulation effect might be attributed to the underdeveloped caecal fermentation capacity very early in life. The addition of more accessible fibre adapted to the age-specific caecal fermentation capacity, especially at very young ages, might further improve the nutritious value of broiler feeds as the increased caecal retention time of substrates at this young age provides a longer period for potential microbial fermentation and thus enables a potentially beneficial evolution of the caecal microbiome.
The wide ranges of the caecal content and the caecal influx of both the solid and soluble markers demonstrate the high biological variation that seems to be inherent to studying the caecal influx mechanism in broilers. A possible cause is the complex caecal filling and emptying mechanism, which is still not fully understood. As the caeca are expected to fill and empty in cycles, it is possible that the asynchronisation of these cycles between broilers contributed to the biological variation measured during these types of marker studies despite the synchronised light regimes that were applied for all broilers in the current study (Clench & Mathias, 1999; Fenna & Boag, 1973). As the main objective of this research was to study the caecal influx mechanisms, no fasting was applied prior to the marker administration in the current trials, as this may introduce a caecal filling and emptying behaviour that is atypical of the normal circumstances in which broilers are commercially raised. However, fasting the broilers before marker administration may contribute to the synchronisation of the marker movements along the GIT. This is common practice when using (fluorescent) markers in animals and would also decrease the issue caused by digesta autofluorescence, improving the detection of the fluorescence polystyrene beads (Li et al., 2018; van der Sluis et al., 2009). Another strategy to increase the synchrony in feeding patterns and, thus, caecal cycles between broilers is the use of a restricted feeding regime instead of continuous feeding or the adjustment of the sampling time points to the light regime. Both fasting and restricted feeding can provoke important changes in bowel motility, which is believed to also affect caecal filling, emptying and transit time, and were therefore not applied in the current study (Son et al., 2002).
5. Conclusion
This study showed that the caecal dimensions and digesta D50 increase with broiler age, suggesting that the digesta particle size allowing caecal influx also increases with age. A dense villous network at the entrance of the caeca restricts the inflow of digesta coming from the ileum, which explains the strong decrease in D50 of caecal digesta compared to ileal digesta. The effect of broiler age on the caecal filtering mechanism could be seen in the increased caecal diameter and digesta D50 with age on the one hand, but also in the increased caecal retention of markers at a young age compared to an older age on the other hand. The studied caecal digesta particle size distribution and influx of solid and soluble markers suggest that the caecal influx of particles larger than 100 μm is very limited. The content of the soluble marker Cr-EDTA in the caeca was maximally 13.2% of the initial orally administered dose in this study, illustrating the strong restriction of caecal influx for both solubles and solids. The caecal concentration of all three marker types showed considerable biological variation, which can be due to asynchronised caecal cycles between broilers. The study of caecal influx of markers was further complicated by the infrequent caecal filling and emptying dynamics which are still not fully understood, and by the possible accumulation of the used markers in the caeca. The results of this study highlight the physical limitations of caecal influx dictated by initial particle size and broiler age. Hence, carefully selecting the physical properties of fermentable fibre in function of age might aid in further improving caecal fibre fermentation in broilers.
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, and there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the content of this paper.
Acknowledgements
Colleagues of the Laboratory of Food Chemistry and Biochemistry, the Nutrition & Animal Microbiota EcoSystems Laboratory and the Laboratory of Livestock Physiology are thanked for their helping hands during the broiler trials. Marie Huyskens is thanked for performing the ICP-MS measurements. Quinten Wouters is thanked for assistance with the Leica TCS SP8X microscope. Paulien Vanderghinste acknowledges the Research Foundation Flanders for a position as PhD fellow (SB3423N).
AbuAli A.M., Mokhtar D.M., Ali R.A., Wassif E.T., Abdalla K.E.H.
Cellular elements in the developing caecum of Japanese quail (Coturnix coturnix japonica): morphological, morphometrical, immunohistochemical and electron-microscopic studies
Separation of digesta fractions complicates estimation of ileal digestibility using marker methods with Cr2O3 and cobalt-ethylenediamine tetraacetic acid in broiler chickens
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Hinton, A., Buhr, R. J., & Ingram, K. D. Physical, chemical, and microbiological changes in the ceca of broiler chickens subjected to incremental feed withdrawal. Poultry Science 200;79(4):483–488. https://doi.org/10.1093/ps/79.4.483.
Lee S.A., Apajalahti J., Vienola K., González-Ortiz G., Fontes C.M.G.A., Bedford M.R.
Age and dietary xylanase supplementation affects ileal sugar residues and short chain fatty acid concentration in the ileum and caecum of broiler chickens
Effect of particle size of insoluble fibre on growth performance, apparent ileal digestibility and caecal microbial population in broiler chickens fed barley containing diets
R Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. 2021. https://www.R-project.org/
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Please, find scientific literature on MCC pellets (CELLETS®), MCC spheres. This list is constantly updated and does not claim to be complete. If you are author, scientist or R&D specialist, please submit your present publication to us for improving the visibility.
Research article Optimising the in vitro and in vivo performance of oral cocrystal formulations via spray coating European Journal of Pharmaceutics and Biopharmaceutics, Volume 124, March 2018, Pages 13-27
Dolores R. Serrano, David Walsh, Peter O’Connell, Naila A. Mugheirbi, Zelalem Ayenew Worku, Francisco Bolas-Fernandez, Carolina Galiana, Maria Auxiliadora Dea-Ayuela, Anne Marie Healy
Conference abstract Multiple-unit orodispersible mini-tablets International Journal of Pharmaceutics, Volume 511, Issue 2, 25 September 2016, Page 1128
Anna Kira Adam, Christian Zimmer, Stefan Rauscher, Jörg Breitkreutz
Research article Asymmetric distribution in twin screw granulation European Journal of Pharmaceutics and Biopharmaceutics, Volume 106, September 2016, Pages 50-58
Tim Chan Seem, Neil A. Rowson, Ian Gabbott, Marcelde Matas, Gavin K. Reynolds, AndyIngram
Research article Physical properties of pharmaceutical pellets Chemical Engineering Science, Volume 86, 4 February 2013, Pages 50-60
Rok Šibanc, Teja Kitak, Biljana Govedarica, StankoSrčič Rok Dreu
Research article Labscale fluidized bed granulator instrumented with non-invasive process monitoring devices Chemical Engineering Journal, Volume 164, Issues 2–3, 1 November 2010, Pages 268-274
Jari T. T. Leskinen, Matti-Antero H. Okkonen, Maunu M. Toiviainen, Sami Poutiainen, Mari Tenhunen, Pekka Teppola, Reijo Lappalainen, Jarkko Ketolainen, Kristiina Järvinen
Research article Granule size distribution of tablets Journal of Pharmaceutical Sciences, Volume 99, Issue 4, April 2010, Pages 2061-2069
Satu Virtanen, Osmo Antikainen, Heikki Räikkönen, Jouko Yliruusi
Research article New insights into segregation during tabletting International Journal of Pharmaceutics, Volume 397, Issues 1–2, 15 September 2010, Pages 19-26
S. Lakio, S. Siiriä, H. Räikkönen, S. Airaksinen, T. Närvänen, O. Antikainen, J.Yliruusi
Research article In vivo evaluation of the vaginal distribution and retention of a multi-particulate pellet formulation European Journal of Pharmaceutics and Biopharmaceutics, Volume 73, Issue 2, October 2009, Pages 280-284
Nele Poelvoorde, Hans Verstraelen, Rita Verhelst, Bart Saerens, Ellen De Backer, Guido Lopes dos Santos Santiago, Chris Vervaet, Mario Vaneechoutte, Fabienne De Boeck, Luc Van Borteld, Marleen Temmerman, Jean-Paul Remon
List – Publications with MCC spheres, 2008 and earlier
Research article Attrition strength of different coated agglomerates Chemical Engineering Science, Volume 63, Issue 5, March 2008, Pages 1361-1369
B. van Laarhoven, S.C.A. Wiers, S.H. Schaafsma, G.M.H. Meesters
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This article on homogeneity and mechanical properties of orodispersible films loaded with pellets was published on Oct 20 2024 on ScienceDirect.
Abstract
Orodispersible films (ODFs) have served as an emerging platform for the delivery of drugs in a convenient way. The production of ODFs with incorporated pellets may still be a challenging process due to problems to obtain proper homogeneity and deteriorating mechanical properties of the films with incorporated relatively big particles in high concentration. The goal of this work was to evaluate the possibility to achieve fast disintegrating ODFs with homogenously incorporated spherical granules without loss of required mechanical properties. Hypromellose films with incorporated placebo pellets (size 200 µm or 100 µm) in a content range of 20–45 % w/w were prepared by a solvent casting method. Planetary mixer (Thinky) was successfully applied for preparation of a homogeneous mass for casting. The suspended spherical solid particles caused dose and size dependent changes in the mechanical properties and disintegration behaviour of ODFs films, but only 100 µm pellets in concentration higher than 40 % reduced significantly the tear resistance. The films with the pellets disintegrated faster and the larger particles reduced the disintegration time by 60 %. Good homogeneity of pellets distribution, expressed as a number of the particles per unit area, was confirmed for films obtained with a gap height 500 or 800 µm.
Document information
Pellet materials
Pellets in two different sizes: CELLETS® 100 and CELLETS® 200, composed of 100% microcrystalline cellulose, were used as model spherical granules.
Authors
Katarzyna Centkowska, Martyna Szadkowska, Marta Basztura, Małgorzata Sznitowska
Source
published on Oct 20 2024 on ScienceDirect under CC BY 4.0 license.
https://cellets.com/wp-content/uploads/2024/10/1-s2.0-S0939641124003631-ga1_lrg.jpg8861546Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2024-10-24 09:25:532024-10-24 09:25:53Homogeneity and mechanical properties of orodispersible films loaded with pellets
Mini-tablets made into hard capsules or administered using special dosing units, as well as pellets in hard capsules or compressed into tablets, offer the advantages of multiparticulate drug delivery systems and are suitable for controlled drug release using polymer coatings. Four different kinds of solid drug preparations were manufactured and investigated concerning drug release. Inert pellets were coated with the model drug sodium benzoate and, in a second step, with the insoluble polymer ethylcellulose. The coated pellets were compressed into mini-tablets and into normal tablets. Another kind of mini-tablet was compressed from a sodium benzoate compression mixture and finally coated with ethylcellulose. The coating of the tablets was performed using fluidized bed technology. The sodium benzoate release plots of the coated pellets show a lag time and retarded release according first-order kinetics. The mini-tablets and normal tablets compressed from pellets release sodium benzoate according to first-order kinetics as well, but without the lag time due to distinct ethylcellulose layer destruction during tableting. The release is retarded with increasing ethylcellulose layer thickness on directly compressed mini-tablets. The different formulations of coated pellets, mini-tablets, and normal tablets offer a broad choice for variable drug release kinetics depending on the biopharmaceutical and pharmacological requirements.
Conclusion
Drug- and polymer-coated pellets may be compressed into mini-tablets as well as into normal tablets. Pellets and mini-tablets compressed into tablets as a multiparticulate drug delivery system offer the advantage of being widely spread in the small intestine for improved drug absorption and increased bioavailability compared to normal tablets. With both tablet types (normal and mini), the sodium benzoate release is delayed depending on the thickness and properties of the ethylcellulose film on the pellets.
Ethylcellulose-coated mini-tablets obtained through the direct compression of sodium benzoate and excipients are an alternative method for multiparticulate drug delivery system preparation. The product is characterized by a slow release rate depending on the ethylcellulose film thickness that may be suitable when prolonged release is required. The variation in release is increased compared to pellets and normal multiple-unit tablets with pellets. Sodium benzoate layering on pellets in the fluidized bed and the subsequent tableting process are feasible for both mini-tablets and normal tablets, representing an interesting option when a variation in the final pharmaceutical form is required for marketing/patenting reasons.
Authors
F. Priese, D. Wiegel, C. Funaro, G. Mondelli, and B. Wolf
https://cellets.com/wp-content/uploads/2023/11/titelbild_Comparison-of-Mini-Tablets-and-Pellets-as-Multiparticulate-Drug-Delivery-Systems-for-Controlled-Drug-Release.jpg5881125Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2023-11-07 10:15:362023-11-07 10:15:36Comparison of Mini-Tablets and Pellets as Multiparticulate Drug Delivery Systems for Controlled Drug Release
https://cellets.com/wp-content/uploads/2022/09/parameter-titelbild.png6271200Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2023-08-22 09:15:152023-08-23 08:21:33Critical aspects of starter spheres in oral pellet formulations one should consider
Multiparticulates made of pellets are ideal dosage forms to be used in pediatrics. Having the suitability of paediatric consumers in mind, formulations of small-sized pellets offer a valuable base for increased compliance and improved age-appropriately dosage form. Due to their round shape of pellets, smooth surface area and narrow particle size distribution they can easily be functionally coated [1] to achieve e. g. a taste masking, enteric protection or the controlled release of the active pharmaceutical ingredient (API) in defined parts of the gastro-intestinal (GI) tract. The release profile then often depends on the coating weight gain (thickness) and composition of the functional coating.
Coating weight gain, manufacture and analysis of pellets
A well soluble drug was used as model API. In a first approach, pellets were produced applying the ProCell technology, a direct pelletization process allowing the production of highly drug loaded matrix pellets (here 95%) in a spouted bed. Two types of pellets were produced: A) with a poly amino saccharide-based binder, followed by a cellulose based seal coating and B) with a polyacrylic acid-based binder, followed by a pH-depending coating. In a second approach the API was layered onto inert starter cores (MCC, CELLETS® 200) by the aid of a cellulose based binder and antitacking agent applying the Wurster technology targeting a drug load of 50 %, followed by a pH-depending coating (C). All three pellets-based populations were functionally coated by a pH-independent sustained release polymer. Samples were taken at pre-defined coating levels for dissolution testing. For API layering and coating a GPCG 1.1 with a 6” Wurster insert was used. Direct pelletization was performed in a ProCell 5. Particle size distribution (PSD) analysis was performed by Eyecon2TM. The particle size is given as numeric or volumetric distribution (e.g. Dn50 or Dv50). The specific surface area is calculated by measuring the true density by gas pycnometry and the Sauter diameter by Laser diffraction. Dissolution was measured in the acid stage (0.1 M HCl), in buffer pH 5.5 and in buffer pH 7.2 over 300 min. The API should not be released in the first 180 min. Between 210 min and 240 min an increased drug release is expected. The dissolution rates at 225 min were compared for the coating levels at 10, 15 and 20 %.
Results
With increasing coating weight gains decreasing dissolution rates at 225 min were measured for the sustained release coating with a good linearity. Matrix PEL (A) show higher dissolution rates comparing the same coating levels than Matrix PEL (B), Wurster pellets showed the strongest decrease with increasing CWG, table 1, figure 1. This correlation was not observed for pH-depending coating (data not shown).
Dv 50 [µm]
Dn 50 [µm]
PSD mean [µm]
Specific surface area [m2/g]
A
Matrix PEL
496
475
481
0,00980
B
Matrix PEL
461
427
425
0,01210
C
Wurster PEL
414
396
401
0,01100
Table 1. PSD data and specific surface area of starter beads before functional coating.
Figure 1. Dissolution at 225 min vs. coating weight gain (CWG)
Summary
Drug loaded pellets were prepared either as matrix pellets applying the ProCell technology, or by layering of starter cores applying the Wurster technology. Both populations were coated with different coating levels of a sustained release functional coating, resulting in decreasing dissolution rates with increasing coating weight gain. Due to the good correlation between coating weight gain and dissolution profile a prediction of the dissolution rate might be possible for pre-defined coating levels. These findings are a crucial step towards novel paediatric formulations with improved dissolution profiles and dosage safety.
References
[1] Palugan, L.; Cerea, M.; Zema, L.; Gazzaniga, A.; Maroni, A. Coated pellets for oral colon delivery, Journal of Drug Delivery Science and Technology 25, 1 – 15 (2015).
https://cellets.com/wp-content/uploads/2022/07/muliparticulates-title.png6271200Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2022-09-30 15:09:262022-09-30 15:09:26Coating weight gain and API release in multiparticulates
This case study on Atomoxetine HCl pellets is a short abstract of the publication by Y.D. Priya et al. [1].
Atomoxetine is a medication used to treat attention deficit hyperactivity disorder (ADHD) [2]. The API is marketed under the trade names Atomoxetine, Atomoxe, Agakalin, and Strattera (initially launched) [3]. Atomoxetine is an extremely bitter API. As being initially launched for children as capsules or tablets, the paediatric compliance by improved taste-masking and the simplified administration to paediatrics are in focus of this study.
A multi-unit particulate pellet coating (MUPS) was selected as oral dosage form. The fluidized bed technology (with Wurster column) was employed for coating and layering processes. This is a well-known technology, which Is for instance offered by Glatt. Starter cores were coated with the API, followed by layering with a polymeric coating for which realized the taste-masking.
Atomoxetine layering
Starter cores are made of Microcrystalline Cellulose (MCC) in sizes comparable to CELLETS® 200, while a fair efficiency of drug layering was observed with the combination of HPMC (Hydroxypropyl methyl cellulose) and HPC (Hydroxypropyl cellulose) as binders. The composition of API layering is presented in Table 1. The drug dispersion was sprayed onto the MCC pellets with an inlet temperature between 50 °C and 55 °C and a fluidized bed temperature between 35 °C and 40 °C.
API layering material
Composition
Starter core
MCC pellets
58.00
API layering
Atomoxetine HCl
25.00
Hydroxypropyl methylcellulose
3.50
Hydroxypropyl Cellulose
3.50
Low-Substituted Hydroxypropyl Cellulose
5.00
Talc
5.00
Purified Water
Qs
Total weight (mg)
100.00
Table 1: Formulation of API layered pellets.
Taste-masking coating
The polymeric taste-masking layer is made of a methacrylate co-polymer (Eudragit EPO) providing an excellent coating with taste masking properties for fine particles and tablets. The composition of the taste-masking suspension is shown in Table 2. The inlet temperature is between 40 °C and 45 °C, and fluidized bed temperature is between 25 °C and 30 °C.
Polymeric coating material
Composition
Drug Layered pellets
100.00
Eudragit EPO
25.00
Sodium Lauryl Sulfate
2.500
Stearic acid
3.750
Talc
6.25
FD&C Yellow No. 6
0.50
FD&C Red No. 3
0.05
Purified Water
Qs
Total weight (mg)
138.050
Table 2: Formulation of polymeric coating suspension.
The efficiency of taste-masking was benchmarked by a bitterness rating on human volunteers. Figure 1 shows, that the taste sensitivity identifies a bitterness at 6 µg/ml API concentration and an extreme bitterness at 7 µg/ml API and higher concentration. Thus, the threshold bitterness of Atomoxetine HCl is 6 µg/ml.
Figure 1: Concentration of drug solution (µg/ ml). Bitter intensity ratings from no bitterness (green), bitterness (blue), extremely bitter (red).
All the volunteers felt bitter taste when the drug layered pellets were coated with 6.25 mg of Eudragit EPO. Whereas in the pellets coated with 12.5 mg and 18.75 mg of Eudragit EPO, bitter taste was masked up to 15 seconds after keeping the tablet in the mouth, and later all the human volunteers felt bitter taste. When the concentration of Eudragit EPO was increased to 25 mg, the bitter taste of Atomoxetine HCl was completely taste-masked and no volunteer was felt bitter taste.
Figure 2: In-Vivo Taste evaluation in healthy human volunteers.
Figure 3 depicts the entire particle size of a taste-masked MCC pellet coated with the Atomoxetine drug layer and 25 mg of Eudragit EPO. The average particle size of the taste-masked pellets is between 180 µm and 250 µm, assuming, that no gritty feeling of particles in patient’s mouth will appear. It should be said, that a micronization of Atomoxetine HCl was deemed to be necessary for the drug layering process. Micronization minimized the surface roughness of the API layered pellet so that an efficient taste-masking coating can be applied.
Figure 3: SEM picture of cross section of a Taste masked pellets coated with 25 mg Eudragit EPO.
Summary
MCC pellets in the size of about 200 µm were layered with Atomoxetine. HPMC and HPC were used as binders, realizing a precise surface definition for a subsequent taste-masking coating. The taste-masking was most efficient at a polymeric concentration of 25 mg. Keeping the size of the coated pellets below 300 µm avoids a gritty feeling and thus increase the patient’s compliance.
This study by Priya et al. indicated that the fluidized bed process produced the most appropriate taste masked pellets of Atomoxetine HCl for oral disintegrating tablets.
[2] “Atomoxetine Hydrochloride Monograph for Professionals”. Drugs.com. American Society of Health-System Pharmacists. Archived from the original on 4 April 2019. Retrieved 22 March 2019.
[3] ROTE LISTE 2017, Verlag Rote Liste Service GmbH, Frankfurt am Main, ISBN 978-3-946057-10-9, (2017) 162.
https://cellets.com/wp-content/uploads/2022/02/Cellets_BCS_class_I.png6621394Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2022-02-17 15:10:072022-07-19 11:27:16BSC Class I APIs in oral formulations
This application note is based on content from Pohlen et al. [1]. Simvastatin (CAS number 79902-63-9) is a cholesterol-lowering agent with a low bioavailability of 5% [2,3]. This API is formulated as a lipid based drug delivery system for oral uptake. Two technologies, which are spray drying and fluidized bed layering technologies were compared with respect to the process and product characteristics of otherwise similar Simvastatin loaded dry emulsion systems. Investigated parameters are the process yield, encapsulation efficiency, relative product stability, particle morphology, drug content, and the relative increase in bioavailability.
Enhancing bioavailability
Some of the recently discovered new chemical entities (NCE) show a low solubility and high permeability (BCS class II), or even low permeability in the case of very high lipophilicity (BCS class IV).
This means a major challenge for formulation development in terms of assuring drug bioavailability [4,5]. A strategy for increasing the solubility are lipid based drug delivery systems (LBDDS). As main advantage, they are likely to solubilize the API and make it available for the absorption into the bloodstream [6]. Additionally, converting the liquid or semi-solid LBDDS into solid dosage forms eliminates undesired characteristics such as a lack of chemical stability and product portability, susceptibility for drug recrystallization and costly manufacturing [7]. Furthermore, solid dosage form solutions allow benefits, such as easy powder processing, flow and compression behavior, controlled drug release, improved patient safety. Among others, dry emulsions are a type of solidified LBDDS and allow carrying and releasing the encapsulated lipophilic API. In the following, some solidification process technologies are introduced. The required parameter for Wurster fluidized bed and spray drying are displayed in Table 2 and Table 3, respectively.
Opposite to the spray drying process, the fluidized bed process employs CELLETS® 200 as starter beads for layering. Several formulations are composed by Pohlen et al., the materials are listed in Table 1.
Table 2: Parameters and values for Fluidized bed layering.
Parameter
Value
Setup
Mini Spray Dryer B-290 (Büchi, CH)
Two-fluid
nozzle
1.4 mm
cap opening diameter
2.20 mm
Inlet airflow rate
28 m3/h
Inlet air temperature
145°C to 175 °C
outlet air / product temperature
75 °C to 80 °C
spraying rate
6 g/min
Drying time
180 s @ 80 °C
Starter pellets
200 g
starting
emulsion
1000 g
Table 3: Parameters and values for spray drying.
Process yield
Spray drying results on average in lower process yield than the fluidized bed results. The process yield for spray drying experiments is in average value of 71.5 %, and of 83.3 % for fluidized bed layering experiments. It is assumed, that in spray drying process adhesion of the smallest particles to the cyclone walls or outtake through the air stream occur.
Drug content
An averaged API content at 9.34 mg/g in fluidized bed experiments, and at 22.2 mg/g for spray dried dry emulsions is reached. Although spray drying offers a much higher drug content and more flexible formulations, the content variation between replicates is increased. The use a swirl air generator in the fluidized bed equipment increases process stability and allows an even larger amount of oil to be incorporated. It is possible increase the maximum amount of API to 22 mg/g onto the starter pellets. Anyhow, the fluidized bed technology suffers from sticky effects of oil phases which is not a big deal in spray drying processes.
Encapsulation efficiency
A low encapsulation efficiency shall be avoided as it causes drug losses during processing and increased production costs. The encapsulation efficiency in fluidized bed experiments is at 80.0 %, compared to spray drying experiments being at 68.4 %. A main issue of the spray drying technology might be higher process temperature leading to a higher risk of API degradation. Spray drying also suffers from a larger surface-to-volume area which might induce an increased risk of oxidation during the drying process.
Morphology and particle size
The main advantage of fluidized bed technology is the use of starter pellets, which are perfectly spherical starter beads. Following, API coating results in highly spherical coated particles with a high level of monodispersity and an average particle size around 336 µm (D50 value). Not mentionable, that spray drying technology results in smaller average particle sizes at 56 µm (D50 value), but the morphology shows a coarse, rough and undefined surface. In turn, dry emulsion layered pellets have better flow properties [8].
Redispersibility and oil droplet size
All re-dispersed oil droplets have a size of a few micrometers between less than 1 µm and less than 7 µm. Fluidized bed layering technology generally leads to larger droplets. Considering also the probable bimodal nature of the droplet size distribution, fluidized bed layering provides a narrower size distribution and thus better results. In turn, the fluidized bed technology might provide slightly better bioavailability.
Product stability
Stability is measured by means of the one-month relative drug content stability. The particles produced in the fluidized bed technology show a better one-month relative drug content stability than particles produced by spray drying. This might be caused by the higher monodispersity, larger particles and smoother surfaces. All properties minimize the risk of API gradation, treatment failure, or toxicity.
Dissolution
Both technologies show a superior dissolution behavior compared to the dissolution of pure crystalline API (less than 3 %) or a generic API tablet (less than 10 %). It has to be stated, that both technologies allow dissolution rates of more than 80 % within the first 30 minutes, wherein the Spray drying products show a slightly better and faster dissolution rate.
Bioavailability
Bioavailability of formulations from fluidized bed layered dry emulsion pellets provide the highest increase in relative bioavailability within the examined formulations, confirming that fluidized bed technology is superior to spray drying technology for potent or low dose APIs.
Summary
Fluidized bed layering and spray drying technology have been selected for analyzing the properties of dry emulsions. Simvastatin was selected as API, encapsulated in the dry emulsion.
Fluidized bed layering technology uses starter cores, such as CELLETS® as a dry emulsion carrier system, while spray drying does not.
The main advantage of the fluidized bed technology is the higher process yield, the better encapsulation efficiency and redispersibility, the defined morphology of the product causing better process handling and product stability.
Spray drying technology allows a higher drug content with better chances of formulation variation, and an even faster and more complete dissolution (Figure 1).
Figure 1: Advantages of technological methods compared to a pure API usage.
References
[1] M. Pohlen, J. Aguiar Zdovc, J. Trontelj, J. Mravljak, M. G. Matjaž, I. Grabnar, T. Snoj and R. Dreu, Eur J Pharm Biopharm (2021), S0939-6411(21)00353-2, doi:10.1016/j.ejpb.2021.12.004
[2] S. Geboers, J. Stappaerts, J. Tack, P. Annaert and P. Augustijns, Int. J. Pharm. 510 (2016) 296-303, doi:10.1016/j.ijpharm.2016.06.048
https://cellets.com/wp-content/uploads/2022/01/FB-SP-pureAPI.png6811201Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2022-01-04 18:02:182022-01-13 10:04:00Technologies for enhancing bioavailability of Simvastatin
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