Quantification of soluble fibre in feedstuffs for rabbits and evaluation of the interference between the determinations of soluble fibre and intestinal mucin

Performance, health, bacterial metabolites and intestinal histomorphology in does and growing rabbits fed diets with increasing lignocellulose-to-cellulose proportions

Adequate levels of dietary fibre can reduce the risk of intestinal health disorders in rabbits after weaning. Therefore, it was the aim of the study to investigate the impact of different lignocellulose and cellulose addition to rabbits' diets on performance and intestinal traits in lactating does and weaned rabbits. A total of 60 rabbit does (4.41 ± 0.45 kg body weight) were fed isonitrogenous diets with lignocellulose and cellulose inclusion rates [%] of 0/8, 2/6, 4/4, 6/2 and 8/0, resulting in dietary lignin-to-cellulose ratios of 0.26, 0.30, 0.32, 0.34 and 0.40, respectively. The diets were fed from 4 d ante partum (a.p.) until day 28 post partum (p.p. weaning). After weaning, 40 young rabbits from each feeding group were fed the same diets for 12 d, when 10 rabbits per group were sacrificed. Body weight gain (BWG), feed intake and feed conversion ratio were obtained. Gastrointestinal content and gut tissue were obtained from the growing rabbits and pH, short-chain fatty acids (SCFA) concentration and gut morphology were investigated. Digestive disorders were scored, and the sanitary risk index was calculated. Does fed the highest lignocellulose addition increased their feed intake [g · kg BW^-1 · d^-1] in the first two weeks p.p. (p < 0.001) and increased BWG (p < 0.001) but without impact on their offsprings' performance. Weaned rabbits fed the highest lignocellulose inclusion showed a reduced feed intake and increased sanitary risk index. Additionally, a higher number of rabbits showed intestinal disorders for a short time (1-2 d, p < 0.001). In the colon content, a higher pH and a lower dry matter content were observed in this group. Caecal contents of 40-d old rabbits showed lower total SCFA, acetate and propionate and higher i-valerate and L-lactate concentrations after feeding diets with high lignocellulose contents. The diet did not influence the acetate-to-propionate ratio. No histomorphological changes were observed in the jejunum, while crypt depth and width were reduced in the caecum of weaned rabbits fed diets with lignocellulose addition. It can be concluded that different proportions of lignocellulose to cellulose addition to rabbits' diets have an impact on health and performance with differences between does and weaned rabbits. While a high lignocellulose inclusion proved beneficial for does, for weaned rabbits, a lower addition should be preferred.

Comparison of In Vivo and In Vitro Digestibility in Rabbits

The apparent dry matter digestibility of diets for rabbits was measured in vivo (ADMDvv) and in vitro with the Ankom DaisyII Incubator. Four diets were tested: low fiber (LF), LF + 5% of pregerminated fenugreek seeds (PGFS) (LF5), LF + 10% PGFS (LF10), and high fiber (HF). For the ADMDvv, feces samples were collected from 56 White New-Zealand × Californian rabbits fed the 4 diets; animals were randomly allocated into 4 groups and housed in individual cages. For the in vitro trial, 3 methods were tested: fecal inoculum (FA) with Kansans State buffer; fecal inoculum with artificial saliva (FB); and multienzyme (ENZ). Fecal inocula were collected at slaughtering from the distal colon of rabbits fed ad libitum the LF diet. For FA and FB methods, the digestibility was measured at 36 and 48 h. The in vitro methods ranked the apparent dry matter digestibility of diets in the same order as in vivo, but ENZ values were always higher than FA and FB at 36 and 48 h. The prediction equations of in vivo digestibility with the ENZ method showed higher coefficient of determination (R2 = 0.69) and lower SE (0.190) than FA and FB; also, reproducibility was higher with ENZ (CV = 3.1%). In conclusion, different methods can be applied to the Ankom DaisyII Incubator to study the digestibility in rabbits. In our trial, the better reproducibility was observed with the multienzyme method than FA and FB were probably related to the variability of inocula.

Lignocellulose as an insoluble fiber source in poultry nutrition: a review

Extensive research in recent years into the use of various fiber sources in poultry nutrition has led to the perception that dietary fiber is more than a simple diet diluent. Several studies showed that the feeding of insoluble fiber sources such as oat hulls, sunflower hulls or wood shavings may affect digestive physiology and function improving chickens health and growth performance. In this context, the effect of lignocellulose as an insoluble dietary fiber source is increasingly being investigated. Lignocellulose is a component of plant cell walls and consists mainly of the insoluble carbohydrate polymers cellulose and hemicelluloses as well as the phenolic polymer lignin. Lignocellulose is chemically and physicochemically different from other insoluble fiber sources and thus possibly has different effects on poultry compared to traditional fiber sources. Several studies investigated the effect of dietary lignocellulose on growth performance, nutrient digestibility, gastrointestinal tract development and intestinal microbiota in broilers and laying hens. Studies differed in terms of feed formulation and lignocellulose inclusion level as well as products of different suppliers were used. The results obtained are inconsistent; beneficial, indifferent or detrimental effects of feeding lignocellulose were observed, so that a final assessment of lignocellulose as a “novel” insoluble fiber source is difficult. This review article summarizes the results of studies in connection with the feeding of lignocellulose to poultry, compares them with those that have used other insoluble fiber sources and illuminates the possible mechanisms of action.

Effect of feeding different levels of lignocellulose on performance, nutrient digestibility, excreta dry matter, and intestinal microbiota in slow growing broilers

Lignocellulose is a constituent of plant cell walls and might be used as a fiber source in poultry nutrition. The current study investigated the impact of increasing dietary levels of lignocellulose on performance, nutrient digestibility, excreta DM, intestinal microbiota, and bacterial metabolites in slow growing broilers. At an age of 10 wk, 60 male broilers of an intercross line (New Hampshire × White Leghorn) were allocated to cages and fed isoenergetic and isonitrogenous diets containing 0.8% (LC1), 5% (LC2), or 10% (LC3) lignocellulose. After 23 D of feeding, broilers were killed and digesta samples of ileum and excreta analyzed for nutrient digestibility and DM. Cecal contents were analyzed for microbial composition and metabolites. Broiler performance was not affected by feeding dietary lignocellulose. LC3 fed broilers showed reduced ileal digestibility of protein compared to chickens fed LC1 (P = 0.003). Moreover, increasing levels of dietary lignocellulose reduced apparent digestibility of organic matter and gross energy (P < 0.001). Feeding of lignocellulose had no impact on the excreta DM of broilers. Increasing levels of dietary lignocellulose lowered cecal counts of Escherichia/Hafnia/Shigella (P = 0.029) and reduced the total concentration of short-chain fatty acids (P < 0.001), lactate (P < 0.05), and ammonia (P = 0.009). The molar ratio of cecal acetic acid was higher in LC3 fed broilers (P < 0.001), while the proportions of cecal propionic acid and n-butyric acid were higher in LC1 and LC2 fed chickens (P < 0.001). Correlation analyses indicated that dietary lignocellulose was negatively related to the total concentration of cecal bacterial metabolites (P < 0.001). In conclusion, the feeding of lignocellulose did not affect growth performance, but impaired nutrient digestibility of slow growing broilers. While minor changes in cecal microbial composition were detected, cecal bacterial metabolite concentrations were significantly reduced with increasing levels of dietary lignocellulose. These findings suggest that lignocellulose is not extensively degraded by bacteria residing in the large intestine of broilers.

In Vitro Techniques Using the DaisyII Incubator for the Assessment of Digestibility: A Review

Simple Summary

The Ankom Daisy^II incubator (AD^II; Ankom Technology Corporation Fairport, NY, USA) has gained acceptance as an alternative to traditional in vitro procedures. It reduces the labour requirement and increases the number of determinations that can be completed by a single operator. The apparatus allows for the simultaneous incubation of several feedstuffs in sealed polyester bags in the same incubation vessel, which is rotated continuously at 39.5 °C. With this method, the material that disappears from the bag during incubation is considered digestible. The method, which was first developed to predict the digestibility of feedstuffs for ruminants, has been modified and adapted to improve its accuracy and prediction capacity. Modifications used by various researchers include the use of different inocula, buffer solutions, and sample weights. Recently, attempts have been made to adapt the method to determine nutrient digestibility of feedstuff in non-ruminant animals, including pets.

Abstract

This review summarises the use of the Ankom Daisy^II incubator (AD^II; Ankom Technology Corporation Fairport, NY, USA), as presented in studies on digestibility, and its extension to other species apart from ruminants, from its introduction until today. This technique has been modified and adapted to allow for different types of investigations to be conducted. Researchers have studied and tested different procedures, and the main sources of variation have been found to be: the inoculum source, sample size, sample preparation, and bag type. In vitro digestibility methods, applied to the AD^II incubator, have been reviewed, the precision and accuracy of the method using the AD^II incubator have been dealt with, and comparisons with other methods have been made. Moreover, some hypotheses on the possible evolutions of this technology in non-ruminants, including pets, have been described. To date, there are no standardised protocols for the collection, storage, and transportation of rumen fluid or faeces. There is also still a need to standardise the procedures for washing the bags after digestion. Moreover, some performance metrics of the instrument (such as the reliability of the rotation mechanism of the jars) still require improvement.

Influence of inoculum type (ileal, caecal and faecal) on the in vitro fermentation of different sources of carbohydrates in rabbits

<p>Two <em>in vitro</em> experiments were performed to analyse the fermentative potential of ileal content, caecal content, soft faeces and hard faeces from adult rabbits. Experiment 1 evaluated 3 doses (0.5, 1.0 and 2.0 g fresh digesta/g substrate dry matter [DM]) of ileal and caecal digesta as inoculum in 28 h-incubations. Two ileal and 2 caecal inocula were obtained, each by pooling the ileal or caecal digesta of 2 adult rabbits. Pectin from sugar beet pulp (SBP) and the insoluble residue obtained after a 2-step <em>in vitro</em> pre-digestion of SBP and wheat straw were used as substrates. The 0.5 dose produced the lowest (<em>P</em>&lt;0.05) amount of gas at 28 h, with no differences (<em>P</em>&gt;0.05) between the 1.0 and 2.0 doses (44.9, 51.6 and 53.8 mL/g substrate DM, respectively; values averaged across inocula and substrates). Experiment 2 evaluated two doses of ileal inoculum (1 and 1.5 g fresh digesta/g substrate DM) and compared ileal digesta, caecal digesta, soft faeces and hard faeces as inoculum for determining <em>in vitro</em> gas production (144-h incubations) of the 3 substrates used in Experiment 1 and wheat starch. Three inocula of each type were obtained, each by pooling either digesta or faeces from 3 rabbits. There were no differences (<em>P</em>&gt;0.05) between the 2 ileal doses tested in gas production parameters, and therefore the 1.0 dose was selected for further ileal fermentations. Starch and pectin showed similar (<em>P</em>&gt;0.05) values of gas production rate and maximal gas production rate when they were fermented with caecal digesta (0.038 vs. 0.043%/h, and 13.7 vs. 15.2 mL/h, respectively), soft (0.022 vs. 0.031%/h, and 9.97 vs. 9.33 mL/h) and hard faeces (0.031 vs. 0.038%/h, and 13.6 vs. 10.8 mL/h), and values were higher than those for SBP and wheat straw; in contrast, values for starch and pectin differed with the ileal inoculum (0.046 vs. 0.024%/h, and 18.4 vs. 6.60 mL/h). Both ileal and caecal gas production parameters were well correlated with those for hard and soft faeces inocula, respectively (r≥0.77; <em>P</em>≤0.040). The ileal inoculum showed a relevant fermentative potential, but lower than that of caecal digesta and soft and hard faeces for all substrates except wheat starch.</p>

In vitro caecal fermentation of carbohydrate-rich feedstuffs in rabbits as affected by substrate pre-digestion and donors' diet

The influence of substrate pre-digestion and donors’ diet on <em>in vitro</em> caecal fermentation of different substrates in rabbits was investigated. Eight crossbreed rabbits were fed 2 experimental diets containing either low (LSF; 84.0 g/kg dry matter [DM]) or high soluble fibre (HSF; 130 g/kg DM) levels. <em>In vitro</em> incubations were conducted using batch cultures with soft faeces as inoculum and four fibrous or fibre-derived, low-starch and low-protein substrates: D-cellobiose (CEL), sugar beet pectin (PEC), sugar beet pulp (SBP) and wheat straw (WS). Substrates in half of the cultures were subjected to a 2-step pepsin/pancreatin in vitro digestion without filtration, and the whole residue (soluble, insoluble and added enzymes) was incubated at 39°C. Gas production was measured until 144 h, and volatile fatty acid (VFA) production at 24 h incubation was determined. Cultures without substrate (blanks) were included to correct gas production values for gas released from endogenous substrates and added enzymes. Pre-digestion had no influence on <em>in vitro</em> gas production kinetic of WS, and only reduced the time before gas production begins (lag time; by 31%; P=0.042) for SBP, but for both substrates the pre-digestion decreased the molar proportion of acetate (by 9%; P≤0.003) and increased those of propionate and butyrate (P≤0.014). For CEL, the pre-digestion increased the gas and total VFA production (by 30 and 114%), shortened the lag time (by 32%), and only when it was combined with LSF inoculum 38 percentage units of acetate were replaced by butyrate (P≤0.039). Treatments had a minor influence on in vitro fermentation traits of SBP pectin. The results showed that the pre-digestion process influenced the in vitro caecal fermentation in rabbits, but the effects were influenced by donors’ diet and the incubated substrate. Pre-digestion of substrate is recommended before conducting <em>in vitro</em> caecal fermentations. The level of soluble fibre in the donors’ diet also influenced the <em>in vitro</em> caecal fermentation, but its effect depended on the type of substrate.

Nutritive value of citrus co-products in rabbit feeding

Pulps from different citrus fruits are relevant agro-industrial co-products in the Mediterranean area in terms of amounts produced and availability. Moreover, part of the product is dehydrated, which increases its interest in monogastric species such as rabbits. Seventy eight samples from various Spanish producers using several types of fresh fruits (orange, tangerine, lemon and pomelo) and different processing methods of orange and tangerine samples (either fresh or dried after adding Ca(OH)₂) were analysed for their chemical composition and <em>in vitro</em> digestibility. Average dry matter (DM) contents of ash, neutral detergent fibre, acid detergent fibre, acid detergent lignin (ADL), soluble fibre, crude protein (CP), insoluble neutral and acid detergent CP, ether extract and gross energy were 49.0, 226, 139, 12.1, 213, 71.2, 13.1, 4.2, 30.5 g and 17.8 MJ/kg DM, respectively. Mean DM and CP <em>in vitro</em> digestibility were 86.7 and 95.6%, respectively. Digestible energy was estimated to be 15.1 MJ/kg DM. A high variability (coefficient of variation from 17% for CP to 60% for ADL) was observed among the samples for most of the traits studied, which was partially explained by the effects of type of fruit and processing. Lemon pulps had on average higher ash and fibre but lower sugar contents than the other pulps. Dehydration processes increased ash content (almost double than for fresh pulp) due to lime addition. As regards the current results, citrus pulp has potential for use in rabbit diets as a source of energy and soluble fibre.

Effects of dietary inclusion of macaúba seed cake meal on performance, caecotrophy traits and in vitro evaluations for growing rabbits

The objective was to evaluate the inclusion of macaúba seed cake (MSC) meal in diets for growing rabbits by assessing their growth and slaughtering performance, haematological traits, nutritional contribution of caecotrophs, in vitro digestibility, degradability and fermentation parameters. A total of 88 rabbits were distributed to four groups with 22 animals each and fed diets containing 0, 50, 100 and 150 g/kg of MSC, respectively. The in vitro assays were conducted employing cecum inoculum on the same dietary treatments. The inclusion of MSC yielded a quadratic effect on in vitro dry matter digestibility (p < 0.001). The maximum amount of produced gas was raised linearly with the inclusion of MSC (p = 0.016). MSC linearly reduced several variables as the nutritional contribution of caecotrophs in dry matter (p = 0.017) and crude protein (p = 0.014), live weight at 51 d (p = 0.024), body weight gain (p = 0.039), average daily feed intake (ADFI) (p = 0.001) and feed conversion ratio (FCR) (p = 0.007) in the first period evaluated (30-50 d); furthermore the ADFI and FCR the second (51-72 d) and whole period (30-72 d) (p < 0.001). MSC addition caused a quadratic effect on white blood cells count (p = 0.026) and a linear decrease of eosinophils (p = 0.045). In conclusion, the inclusion of up to 150 g/kg of MSC improves the in vitro digestibility and fermentation potential of the diets, reflecting on the ADFI and FCR of the animals, although adverse effects are observed on the weight of the commercial carcass and nutritive contribution of the caecotrophs.

Ruminal degradation of cell wall associated nitrogenous compounds of several (15) N-labelled feeds

BACKGROUND

Ruminal in situ effective degradability (ED) of dry matter (DM), neutral (NDF) and acid (ADF) detergent fibres, total-N and NDF (NDIN) and ADF (ADIN) bound-N in sunflower seed (SS), wheat grain (WG) and wheat straw (WS) were measured in three ruminally cannulated sheep, correcting microbial N-contamination using the (15) N dilution technique modified to consider the (15) N supply to adherent bacteria.

RESULTS

The lack of correction for N-contamination under-evaluated ED estimates in 1.52% (total-N), 28.0% (NDIN) and 33.3% (ADIN) in SS and in 1.02% (total-N) and 4.43% (NDIN) in WG. In the remaining cases, this contamination prevented establishing apparent degradation kinetics and, therefore, errors were not measured. Microbial corrected ED estimates in SS were higher in total-N (0.917) than in NDIN (0.559) and ADIN (0.520), which showed similar values. This behaviour was also shown in WS (0.670, 0.386 and 0.426, respectively), whereas decreasing values were shown from total-N (0.917) to NDIN (0.830) and ADIN (0.482) in WG.

CONCLUSION

Results confirm that NDF and ADF procedures failed to remove large fractions of particle adherent microorganisms, under-evaluating the ED of NDIN and ADIN. Degradation of NDIN represented a significant part of the degraded N, whereas ADIN contribution was only negligible in WG. © 2015 Society of Chemical Industry.

Nutritive value of co-products derived from olivecake in rabbit feeding

<p>Olive cake is one of the main agro-industrial co-products in the Mediterranean area of Spain, with high availability almost all year round. In addition, most of the product is dehydrated, which increases its interest in monogastric species such as rabbits. Nineteen samples from various Spanish oil mills using different processing methods were analysed for their chemical composition and in vitro digestibility. The average composition was [in dry matter (DM) basis]: ash (9.64%), neutral detergent fibre (52.0%), acid detergent fibre (36.8%), acid detergent lignin (19.1%), crude protein (CP) (11.3%), insoluble neutral (8.0%) and acid detergent crude protein (5.15%), ether extract (10.9%) and gross energy (21.9 MJ/kg). DM and CP in vitro digestibility were, on av., 53.4 and 41.4% respectively. High variability was observed among the samples for most of the traits studied. Fibrous fractions were highly correlated among them and negatively with ether extract content, whereas CP was little related to other feed components. A stepwise regression analysis allowed us to determine regression equations to predict DM and CP in vitro digestibilities from chemical composition (R2=0.80 and 0.91, respectively). As regards the current results, olive cake has potential use for rabbits as a source of insoluble fibre and lignin. Crude samples (not oil extracted) combined with sieving to retain the smaller particles have an additional interest, because of their higher energy value and significant supply of high quality fat.</p>

Comparative digestibility of energy and nutrients and fermentability of dietary fiber in eight cereal grains fed to pigs

BACKGROUND

Cereal grains provide a large portion of caloric intake in diets for humans, but not all cereal grains provide the same amount of energy. Therefore, an experiment was conducted to determine and compare the metabolizable energy (ME), the apparent ileal digestibility (AID), and the apparent total tract digestibility (ATTD) of gross energy (GE) and nutrients in eight cereal grains when fed to pigs.

RESULTS

Rice had greater (P < 0.05) AID of GE than other cereal grains, greater (P < 0.05) AID of starch than yellow dent corn, dehulled barley, rye, and wheat, and greater (P < 0.05) ATTD of GE than yellow dent corn, rye, sorghum, and wheat. Dehulled barley, rye, and sorghum had less (P < 0.05) AID of starch than other cereal grains. Dehulled barley had greater (P < 0.05) ATTD of GE than rye. Dehulled oats had the greatest (P < 0.05) ME compared with other cereal grains, whereas rye had the least (P < 0.05) ME.

CONCLUSION

Dehulled oats provide more energy to diets and should be used if the goal is to increase caloric intake. In contrast, sorghum and rye may be more suitable to control diabetes and manage body weight of humans.