Neutral Detergent Soluble Fibre Research Articles

Evaluation of different ratios of neutral detergent-soluble carbohydrate fractions on performance, ingestive behavior, and nitrogen balance in dairy goats.

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9kg and 60days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance.

Effect of neutral detergent-soluble carbohydrate profile on digestive parameters of dairy goats

ABSTRACTThe aim of the present study was to evaluate the effect of diets with high concentrations of different neutral detergent-soluble carbohydrates on the ruminal degradability and total digestibility, digestive parameters, and microbial efficiency of dairy goats. Five non-lactating goats and rumen and abomasum cannulas were arranged in a 5 × 5 Latin square design. The diets were the ratio between starch associated with soluble sugar (StSS) to NDSF (StSS:NDSF): 0.82; 1.3; 1.63; 2.94; and 5.35. Starch intake increased (P < 0.001) linearly with the increase of StSS:NDSF ratios in the diet. There was a linear decrease (P < 0.001) in the intake of soluble carbohydrates and neutral detergent soluble fiber (NDF). The ruminal degradability of dry matter (DM), crude protein, NDF, and NDSC decreased linearly (P < 0.05) with the increase of StSS:NDSF ratios in the diet. Total nitrogen flow, microbial nitrogen flow (MNF), and microbial efficiency increased (P < 0.05) with the increment of StSS:NDSF ratios in the diet. The increases in StSS:NDSF ratios in the diet affected only butyric (P < 0.001), valeric (P < 0.001), and isovaleric (P = 0.004) acids, as well as pH (P < 0.001). High StSS:NDSF ratio diets do not affect DM and NDF intake but reduce DM and NDF ruminal degradability, increasing MNF and, consequently, microbial efficiency in dairy goats.

Different proportions of starch and neutral detergent-soluble fiber in diets for feedlot lambs.

This study evaluated the replacement of starch (ST; cracked corn) by neutral detergent-soluble fiber (NDSF; citrus pulp) and its effects on feed intake, performance, digestibility, carcass traits, and nitrogen balance of lambs. In Experiment 1, male lambs (n = 24, 19.1 ± 1.9 kg body weight [BW]) received: Starch (ST) = 250 g starch/kg dry matter (DM); ST/NDSF = 180 g starch/kg DM + 180 g NDSF/kg DM; or NDSF = 250 g NDSF/kg DM. After 84 d, animals were slaughtered and carcasses were evaluated. In Experiment 2, male lambs (n = 15, 23.2 ± 2.3 kg BW) were used to assess digestibility and nitrogen balance. Final BW, average daily gain, gain to feed and feed intake decreased when animals were fed NDSF (P≤0.002), reflecting in lighter carcasses (P<0.0001). The NDSF decreased edible non-carcass components (P=0.0006), total usable products (P<0.0001), commercial cuts and intramuscular fat (P≤0.02). Except for NDSF and ST, the digestibility of nutrients was improved for NDSF diet (P≤0.04). The use of 250 g NDSF/kg DM as citrus pulp in finishing diets for lambs impairs performance, carcass, meat traits and nitrogen balance. However, the moderate replacement of corn by citrus pulp does not change productive variables.

Nutraceutical and preservative potential of Acacia mearnsii and Acacia dealbata leaves for ruminant production and product quality enhancement

AbstractSeasonality and species are key aspects of the abiotic and biotic environment, respectively, that influence nutrient, phytochemical and antioxidant profiles of invasive alien plants leaf-meals. The current study investigated the effects of season on nutrient, amino acid, fatty acid, mineral, bioactive polyphenolic composition and antioxidant activity of Acacia mearnsii and A. dealbata leaf-meals. Overall, A. mearnsii leaf-meal harvested in the hot-dry-season had greater crude protein, ether extract, neutral detergent soluble fibre, 24 and 48 h in vitro neutral detergent fibre digestibility, macro-mineral contents, individual polyphenols, C18:1n9 and C18:2n6 compared to other leaf-meals. Regardless of the season, A. mearnsii leaf-meals had greater amino acid concentrations than A. dealbata leaf-meals. Hot-dry-season leaf-meals had a greater concentration of total flavonoids than the leaf-meals in the cool-wet-season irrespective of species. Antioxidant potency composite of the Acacia leaf-meals was in the order of A. dealbata × hot-dry-season &gt; A. mearnsii × hot-dry-season &gt; A. mearnsii × cool-wet-season &gt; A. dealbata × cool-wet-season. The findings suggested that A. mearnsii leaf-meal harvested in the hot-dry-season has superior nutritional and polyphenolic profiles, which could support its use as a nutraceutical and preservative for the enhancement of ruminant production and product quality compared to other leaf meals.

Non-fiber Carbohydrates in Forages and Their Influence on Beef Production Systems

Forages can provide a complete diet for ruminant animals, increasing the sustainability of beef production systems worldwide while reducing competition with humans for agricultural land or grain crops. Much of the emphasis on the nutritional characteristics of forages has been on the fiber, sugars, starch, and protein they supply to the rumen, despite the fact that other less-explored constituents, i.e., neutral detergent soluble fiber (NDSF) and other non-structural or non-fiber carbohydrates (NFC) also play a key role in the nutrition of ruminants. This paper explores the less investigated potential of temperate legumes to accumulate levels of NFC comparable to corn silage or beet pulp in cool, dry environments under irrigation, and its implications for forage-based beef production systems. We conclude that genetic or managerial interventions (i.e., breeding programs, defoliation frequency) or ecological conditions (i.e., climate, elevation) that increase concentrations of NFC in legumes can enhance beef production, meat quality, and the efficiency of nitrogen utilization by ruminants while reducing environmental impacts.

Quantifying non-fibrous carbohydrates, acid detergent fiber and cellulose of forage through an in vitro gas production technique.

The in vitro gas production (GP) technique has been useful for evaluating the potential degradability of feedstuffs in ruminal environments; GP is related to the components of feedstuff ingredients. Linear models were generated and validated as alternatives of quantifying neutral detergent-soluble fiber, starch (St)/hemicellulose (Hem) and cellulose (Cel) through GP. Residuals of models obtained from the peaks of GP [0-8 h (GP-8), > 8-24 h (GP-24), > 24-48 h (GP-48) and > 24-81 h (GP-81)] of 0.02, 0.04, 0.08, 0.12 and 0.20 g of glucose (Glu), St and Cel respectively. The incubations were analyzed in mixtures of Glu, St and Cel. The best fitting models (r2 from 0.709 to 0.935) were tested on corn stover (CS) to quantify rapid fermentation fractions (RF; equivalent to Glu), medium fermentation fractions (MF; equivalent to St) and low fermentation fractions (LF48; equivalent to Cel); in CS, RF, MF and LF models had standardized residuals < 0.09. The analysis with Leucaena (Leucaena leucocephala Lam. de Wit) and star grass (Cynodon nlemfuensis Vanderyst) consider high-protein ingredients. The in vitro GP of RF, MF and LF48 fractions equivalent to Glu, St and Cel are affected by maturity and harvest time even when the chemical composition remains similar, and so RF, MF and LF48 should be considered during the design of ruminant diets. In vitro GP could be used to quantify the components of some forages, although further studies are necessary. © 2020 Society of Chemical Industry.

Characterization of Seed, Oil, and Fatty Acid Methyl Esters of an Ethyl Methanesulfonate Mutant of Camelina sativa with Reduced Seed‐Coat Mucilage

AbstractCamelina sativa L. Crantz (large‐seeded false flax) is a promising oilseed crop for the production of edible oil and biodiesel. An ethyl methanesulfonate (EMS) mutant of C. sativa was identified that lacked seed coat mucilage (SCM) using Ruthenium Red (RR) colorimetric staining. Compared with wild‐type (WT) plants, the mucilage‐defect mutant line (Cs98) had smaller seeds and seeds with significantly less SCM, but exhibited significantly taller plant height. The seed mass and oil content of the seeds of Cs98 were significantly lower than those of WT plants. However, the seeds of Cs98 had significantly higher crude protein and starch contents, but a significantly lower neutral detergent‐soluble fiber (NDSF) fraction (pectin) content. Although Cs98 seed contained significantly higher mineral contents for various macro‐ and microminerals (e.g., Mg, S, Al, Cu, Mn, Fe, and Zn), these large differences did not prevent the Cs98 seed biodiesel from passing all American Society for Testing and Materials (ASTM) standards for macro‐ and micromineral content and viscosity, pH, and turbidity. Notably, the oil and biodiesel derived from Cs98 had significantly reduced viscosity compared with WT. Water washes of oil derived from WT and Cs98 seed confirmed that the Cs98 contained only 57% of the mucilage content of the WT oil washes. These significantly lower pectic residues are expected to improve the flow characteristics of the resultant oil and require less washing during biodiesel production.

Consequences of Partial Substitution of Starch with Fibre on Growth, Carcass Traits, Nutrient Digestibility and Blood Parameters in Growing Rabbits

The study aimed to investigate the partial substitution of starch with fibre on the growth performance, nutrient digestibility and select blood indices of growing rabbits. One hundred-twenty 28 d-old male rabbits were equally distributed into four groups in a 2×2 factorial design. Four diets were formulated wherein starch was partially replaced with two different levels each of acid detergent fibre (ADF) at 23.6 and 29.2% and neutral detergent soluble fibre (NDSF) at 14.5 and 15.5%. At the end of the experiment (90 days of age), the weight gain and feed conversion increased in rabbits fed a high level of NDSF. However, rabbits fed low level of ADF showed a significant improvement in the digestibility of DM and CP. Feed intake was increased by 3.5% with lower level of ADF. Carcass traits and blood indices did not show significant differences among the treated groups. It may be concluded that partial substitution of starch with (15.5%) NDSF and (23.6) ADF had beneficial effects on the performance and nutrients digestibility without any adverse effects on health status of rabbits.

Milk Fat Depression: Etiology, Theories, and Soluble Carbohydrate Interactions

Milk fat depression is a metabolic disorder characterized by a sustained reduction in milk fat and has challenged producers and scientists for over a century. Nutritionists have incorporated supplemental fat in dairy rations for years as a means to increase the energy density of the diet, but often decreased fiber digestibility or milk fat depression was observed. The rumen microbial populations were thought to play a major part in why producers had difficulty using high levels of unsaturated fat. Many different theories evolved throughout the century into the causes of milk fat depression that often appears ex nihilo. Such theories involved concepts centered on substrate limitation, low rumen pH, and specific bioactive fatty acids. The biohydrogenation theory became one of the more widely accepted explanations for milk fat depression. Since the discovery of certain fatty acid isomers that induce milk fat depression more investigations have aimed at how different nutrients interact in the rumen and affect the production of these milk fat inhibiting isomers. Readily available carbohydrates such as sugar, starch, neutral detergent soluble fiber, and rumen availability of these carbohydrate fractions, all effect the microbial populations within the rumen that are involved in the process of biohydrogenation. This review summarizes the knowledge available on milk fat depression, microbial influences, how soluble carbohydrate fractions influence on biohydrogenation.

Nutritive value of distillers dried grains with solubles from barley, corn and wheat for growing rabbits

Due to their fibrous nature, distillers dried grains with solubles (DDGS) from the bioethanol industry could be considered an interesting feedstuff for rabbit nutrition. To characterize the DDGS available in the Iberian Peninsula the chemical, amino acid and fatty acid composition of eight DDGS batches (2, 2 and 4 from barley, corn and wheat grains, respectively) was performed. Five diets were formulated to determine the nutritive value of DDGS in growing rabbits by the substitution method: a control diet and four experimental diets containing 200g of the DDGS being evaluated kg−1 dry mater (DM) [DDGS from national barley, national corn, Brazilian corn and national wheat grains]. The digestibility trial was performed using 60 three-way crossbred fattening rabbits (12 per diet), aged 42days with average live weight of 1.49kg (S.E.: 0.033kg). DDGS can be characterized as a raw material really rich in fibre (neutral detergent fibre and neutral detergent soluble fibre) and crude protein (CP, on av. 352, 208 and 318gkg−1 DM, respectively). Barley DDGS had higher fibre and lower protein contents than wheat DDGS (+25g of acid detergent fibre and −91g of CPkg−1DM, respectively; P<0.05), as well as the highest ash content (on av. +16gkg−1DM; P<0.05). Corn DDGS had intermediate fibre and protein values between barley and wheat DDGS, but were the richest in ether extract (on av. +70gkg−1 DM). DDGS’ protein was richer in proline, phenylalanine, valine and arginine for barley DDGS (107, 55, 54 and 51gkg−1 CP, respectively), in leucine, alanine and histidine for corn DDGS (114, 75 and 27gkg−1 CP, respectively), and in glutamic acid for wheat DDGS (290gkg−1CP). Barley DDGS was richer in saturated (236gkg−1 total fatty acids), corn DDGS in monounsaturated (278gkg−1 total fatty acids) and wheat DDGS in polyunsaturated fatty acids (615gkg−1 total fatty acids). Barley DDGS was characterized by the lowest nutritive value traits of DDGS evaluated (11.9MJ digestible energy (DE) and 168g digestible protein (DP)kg−1DM). In spite of higher protein and lower fibre content of the Brazilian corn (+1.7gCP and −31g neutral detergent fibrekg−1DM), no significant differences for the nutritive value of both corn DDGS were observed (on av. 15.3MJ DE and 208gDPkg−1DM). Wheat DDGS might be considered as the DDGS with the highest nutritive value of those evaluated (15.7MJ DE and 263gDPkg−1DM).

Effects of nutrition on digestion efficiency and gaseous emissions from slurry in growing pigs: II. Effect of protein source in practical diets

This research aimed to investigate effects of protein source in practical diets on nutrient excretion and potential emissions of ammonia (NH3) and methane (CH4) in pigs. Three experimental feeds were designed to substitute a mixture of soybean meal and soybean hulls (SB diet) with sunflower meal (SFM) or wheat DDGS (WDDGS). The proportion of other ingredients was also modified in order to maintain similar nutrient contents across diets. Changes in protein source led to differences in dietary content of neutral detergent insoluble crude protein, soluble fibre (SF) and acid detergent lignin. Twenty-four pigs (8 per diet), weighing 52.3 or 60.8kg at the first and second batch, respectively, were housed individually in metabolic pens to determine during a 7-day period dry matter (DM) balance, coefficients of total tract apparent digestibility (CTTAD) of nutrients, and faecal and urine composition. Representative slurry samples from each animal were used to measure NH3 and CH4 emissions over an 11 and/or 100-day storage period, respectively. Neither DM intake, nor DM or energy CTTAD differed among experimental diets, but type of feed affected (P<0.001) crude protein (CP) digestibility, which was highest for SFM (0.846) than for SB (0.775) diet, with WDGGS-based diet giving an intermediate value (0.794). Faecal DM composition was influenced (P<0.001) accordingly, with the lowest CP concentration found for diet SFM and the highest for SB. The ratio of N excreted in urine or faeces decreased from SFM (1.63) to SB diet (0.650), as a consequence of both lower urine and higher faecal losses, with all the faecal N fractions increasing in parallel to total excretion. This result was parallel to a decrease of potential NH3 emission (g/kg slurry) in diet SB with respect to diet SFM (from 1.82 to 1.12, P<0.05), giving slurry from WDGGS-based diet an intermediate value (1.58). Otherwise, SF and insoluble neutral detergent fibre (aNDFom) CTTAD were affected (P<0.001 and P=0.002, respectively) by type of diet, being lower for SFM than in SB-diet; besides, a higher content of aNDFom (491 vs 361g/kg) on faecal DM was observed for SFM with respect to SB, with WDDGS-based diet being intermediate. Degree of lignification of aNDFom of faeces decreased in the order SFM>WDDGS>SB (from 0.171 to 0.109 and 0.086, respectively) in parallel to a decrease of potential CH4 emission per g of OM of slurry (from 301 to 269 and 256mL, respectively). When both gaseous emissions were expressed per animal and day, differences followed the same trend, but did not reach significant levels.

Effects of dietary fat on fertility of dairy cattle: A meta-analysis and meta-regression

Evidence is increasing of positive effects of feeding fats during transition on fertility and the adaptation to lactation. This study used meta-analytic methods to explore the effects of including fats in the transition diet on the risk of pregnancy to service (proportion pregnant) and calving to pregnancy interval. Meta-analysis was used to integrate smaller studies and increase the statistical power over that of any single study and explore new hypotheses. We explored the effect of fats and diet composition on fertility using meta-regression methods. Relatively few highly controlled studies are available providing detailed descriptions of the diets used that examined interactions between fat nutrition and reproductive outcomes. Only 17 studies containing 26 comparisons were suitable for inclusion in statistical evaluations. Reproductive variables evaluated were risk of pregnancy (proportion pregnant), primarily to first service, and calving to pregnancy interval. Production variables examined were milk yield, milk composition, and body weight. The sources of heterogeneity in these studies were also explored. A 27% overall increase in pregnancy to service was observed (relative risk=1.27; 95% confidence interval Knapp Hartung 1.09 to 1.45), and results were relatively consistent (I2=19.9%). A strong indication of a reduction in calving to pregnancy interval was also identified, which was consistent across studies (I2=0.0%), supporting a conclusion that, overall, the inclusion of fats does improve fertility. Further exploration of the factors contributing to proportion pregnant using bivariate meta-regression identified variables that reflected changes in diet composition or animal response resulting from inclusion of the fat interventions in the experimental diets fed. Increased fermentable neutral detergent fiber and soluble fiber intakes increased the proportion pregnant, whereas increased milk yield of the treatment group decreased this measure. Unexpectedly, the estimated energy costs of urea production also had a positive association with proportion pregnant. The limited number of suitable studies for the analysis highlights the need for more work to improve understanding of the critical nutritional factors affecting fertility. These factors include specific fatty acids in dietary interventions that contribute to increasing fertility of cows in dairy production systems.

Consumo, digestibilidade e balanço de nitrogênio de cordeiros alimentados com alto teor de amido ou fibra solúvel em detergente neutro associados ao óleo de girassol

The aim of this study was to evaluate the effect of different carbohydrate sources associated with sunflower oil on intake, digestibility of nutrients and nitrogen balance in diets of lambs. Twenty lambs were used, assigned in a completely randomized design with a 2 x 2 factorial arrangement of treatments with two sources of neutral detergent soluble carbohydrate, starch and neutral detergent soluble fiber, with and without the inclusion of 4.2% sunflower oil. The dry matter intake was not affected by carbohydrate sources and the inclusion of oil. Diets with a high percentage of starch provided higher digestibility of dry matter, starch and ether extract. The different sources of carbohydrates had no interference on digestibility of organic matter, crude protein, neutral detergent soluble fiber, nonfiber carbohydrates, neutral detergent fiber, hemicellulose and acid detergent fiber. The addition of oil in the diets increased the digestibility of ether extract. The combination of 4.2% oil in the diet high in soluble neutral detergent fiber had no influence on the nutrient digestibility, otherwise, the addition of oil at high starch diet caused a significant reduction in the digestibility of organic matter, neutral detergent fiber, hemicellulose and nonfiber carbohydrates. The quantities of nitrogen intake, absorbed and retained, did not differ as sources of carbohydrates and oil inclusion in the diet. The association of 4.2 % sunflower oil to the different sources of carbohydrates in the diet does not affect consumption and nitrogen metabolism in lambs. The addition of 4.2 % oil in the diet with high starch (28% of DM diet) promotes reduction in digestibility of organic matter, of fibrous and nonfibrous carbohydrate in the diet.

Response of early lactation Holstein cows to partial replacement of neutral detergent soluble fibre for starch in diets varying in forage particle size

This study investigated the effects of partial replacement of neutral detergent soluble fibre (NDSF) for starch in diets varying in particle size (PS) of alfalfa hay on chewing activities, ruminal fermentation, nutrient digestibility and performance of early lactation dairy cows. Eight multiparous Holstein cows (66±5d in milk; 42.9±3.1kg milk/d) were used in a replicated 4×4 Latin square design with four 22d periods with the last 8d used for data collection. The experiment was a 2×2 factorial arrangement with 2 levels of NDSF (low=84g/kg or high=118g/kg diet dry matter) each combined with 2 PS (short=20mm or long=40mm) of alfalfa hay. Feeding short PS in combination with low level of NDSF increased intake of DM and OM (P<0.05). Total chewing time was not affected, however, total eating time and eating times spent per kg of DM and NDF consumed decreased when forage particle size was reduced (P<0.05). High NDSF diets increased total eating time and eating times spent per kg DM and NDF ingested and increased apparent digestibility of NDF (P<0.05). However, feeding high NDSF diet increased the OM digestibility only in long PS diet (P<0.05). Treatments did not affect ruminal pH; however, feeding short PS tended to increase total volatile fatty acid concentration, decreased molar proportion of acetate and increased that of propionate. Inclusion of NDSF decreased molar proportion of propionate and increased that of butyrate and decreased ruminal ammonia concentration (P<0.05). Milk yield and composition and milk energy output were similar among treatments. Results show that partial replacement of NDSF for starch increases nutrient digestibility, most notably for NDF, and maintains milk yield and composition of early lactation cows fed diets varying in forage PS.

Effects of Neutral Detergent Soluble Fiber and Sucrose Supplementation on Ruminal Fermentation, Microbial Synthesis, and Populations of Ruminal Cellulolytic Bacteria Using the Rumen Simulation Technique (RUSITEC)

We evaluated the effects of neutral detergent soluble fiber (NDSF) and sucrose supplementation on ruminal fermentation, microbial synthesis, and populations of ruminal cellulolytic bacteria using the rumen simulation technique (RUSITEC). The experiment had a 2×2 factorial design with two dosages of sucrose, low (ca. 0.26 g d−1, low-sucrose) and high (ca. 1.01 g d−1, high-sucrose), and two dosages of supplied NDSF, low (1.95 g d−1, low-NDSF) and high (2.70 g d−1, high-NDSF). Interactions between NDSF and sucrose were detected for xylanase activity from solid fraction and apparent disappearance of neutral detergent fiber (NDF) and hemicellulose, with the lowest values observed for high-NDSF and high-sucrose treatment. Supplemental NDSF appeared to increase the molar proportion of acetate and reduce that of butyrate; however, the effects of supplemental sucrose on VFA profiles depended upon NDSF amount. There was a NDSF×sucrose interaction for the production of methane. High-NDSF fermenters had lower ammonia-N production, greater daily N flow of solid-associated microbial pellets and total microorganisms, and greater microbial synthesis efficiency compared with low-NDSF fermenters. Supplementation with NDSF resulted in an increase in 16S rDNA copies of Ruminococcus flavefaciens and a reduction in copies of Ruminococcus albus. Supplementation with sucrose tended to increase the 16S rDNA copies of R. albus from liquid fraction, but did not affect daily total microbial N flow and cellulolytic bacterium populations from solid fraction. These data indicate that the effects of the interaction between NDSF and sugars on ruminal fermentation and fiber digestion should be taken into account in diet formulation. Ruminal fermentation and metabolism of sugars warrant further investigation.

Partial replacement of starch with acid detergent fibre and/or neutral detergent soluble fibre at two protein levels: Effects on ileal apparent digestibility and caecal environment of growing rabbits

The effects of the composition of peri-weaning diets on apparent ileal digestibility of nutrients and caecal environment were studied in growing rabbits. Eight diets were formulated according to a 2×2×2 factorial design to increase acid detergent fibre (ADF) from 230 to 290gkg−1 dry matter (DM) at the expense of mainly starch, to increase neutral detergent soluble fibre (NDSF) from 145 to 185gkg−1 DM at the expense of mainly starch, and to reduce crude protein (CP) content from 175 to 145gkg−1 DM. A total of 32 litters of eight kits were randomly assigned to the diets at 17 days of age, weaned at 28 days of age and slaughtered at 35 days of age to collect samples of ileal and caecal contents. The substitution of ADF for starch reduced the coefficient of apparent ileal digestibility (CAID) of DM (0.292 vs. 0.229; P<0.01). The substitution of NDSF for starch increased the CAID of NDSF (−0.040 vs. 0.099; P<0.01). An interaction between dietary ADF and NDSF levels was found for the CAID of CP, higher in the low ADF-low NDSF diets than in the rest (+0.074; P<0.05). The reduction of dietary CP content decreased the CAID of CP (0.578 vs. 0.525; P<0.05) and NDSF (0.086 vs. −0.038; P<0.01). Interactions between dietary ADF and NDSF levels were found affecting full caecum weight as well as DM content and pH of caecal digesta. The increase of ADF in the high NDSF diets reduced full caecum weight (−9.1gkg−1 live weight; P<0.01), increased DM content of caecal digesta (+31gkg−1; P<0.001) and reduced caecal pH (−0.10; P<0.05). In the low NDSF diets, higher ADF increased DM content of caecal digesta to a lesser extent (+16gkg−1; P<0.001) and increased caecal pH (+0.08; P<0.05). The increase of NDSF in the high ADF diets increased full caecum weight (+8.5gkg−1 live weight; P<0.01) and reduced caecal pH (−0.14; P<0.001). In the low ADF diets, higher NDSF increased full caecum weight more extensively (+15.5gkg−1 live weight; P<0.001) and reduced DM content of caecal digesta (−16gkg−1; P<0.001). Both ADF and NDSF replacing starch increased total volatile fatty acid (VFA) concentration of caecal digesta (+11.5% and +13.9%, respectively; P<0.01). The replacement with NDSF increased molar proportion of butyrate (0.095 vs. 0.112; P<0.001) at the expense of mainly acetate (0.841 vs. 0.820; P<0.001) and reduced ammonia concentration of caecal digesta (−8.1%; P<0.05). The reduction of dietary CP content decreased total VFA (−14.4%; P<0.001) and ammonia (−23.5%; P<0.001) concentrations of caecal digesta and increased caecal pH (5.87 vs. 5.93; P<0.05). Overall, the three dietary changes under study led to changes in the caecal environment which might be effective in reducing mortality rate in a context of rabbit epizootic enteropathy.

Microbial ecosystem and fermentation traits in the caecum of growing rabbits given diets varying in neutral detergent soluble and insoluble fibre levels

The effect of the level of neutral detergent fibre (NDF: 0.35, LI and 0.42, HI) and neutral detergent soluble fibre (NDSF: 0.14, LS and 0.17, HS) in the caecal ecosystem was studied in 24 weaned (28 days of age) rabbits, weighing 630 ± 80.2 g in a 2 × 2 factorial design. After 22 days, rabbits were slaughtered and their caecal contents sampled. The caecal pH (on average 6.2) and molar volatile fatty acids (VFA) proportions were not affected by dietary treatments, but total VFA concentration tended to be lower with NDF (84.7 vs. 74.1 mmol/l; P = 0.095). The amount of total bacteria tended (P = 0.075) to increase with NDSF, but only in diets with 0.35 NDF. The caecal proportions of Ruminococcus albus and Fibrobacter succinogenes were not affected by type or level of fibre, but Butyrivibrio fibrisolvens decreased (P = 0.055) with the NDF proportion in LS diets. Denaturing gradient gel electrophoresis (DGGE) analysis showed that bacterial communities clustered according to each combination of NDF and NDSF, but did not greatly differ among diets (similarity indexes between 0.67 and 0.70), nor biodiversity was affected (average Shannon and richness indexes 3.50 and 33.1; P > 0.10). Archaeal population revealed changes in the amount and composition that were particularly evident in HS diets, decreasing in concentration (from 4.37 to 4.12 log10 gene copy number/g) and biodiversity (Shannon index from 3.14 to 2.52 and richness index from 23.7 to 13.9) compared to LS. The type and level of dietary fibre had a minor impact on caecal fermentation traits or caecal bacterial community. However, the increase in NDSF from 0.14 to 0.17 reduced concentration and diversity of methanogenic archaea.

Characterisation of caecal microbial diversity of lactating does and their offspring given diets with different neutral detergent soluble to insoluble fibre ratios

The effect of neutral detergent soluble fibre (NDSF) to neutral detergent fibre (NDF) dietary ratio (0.29, LR and 0.43, HR) on the caecal ecosystem of lactating does and their offspring was studied. From the 17th day of lactation, each diet was given to four does, allowing for free access to their litters. Does were sampled at 17 and 28 days of lactation, and also two pups per litter at 17 (milk-fed only), 28 (milk and solid fed) and 49 days of age. DGGE was used to study bacterial caecal biodiversity, and total bacterial concentration and relative proportions of Ruminococcus albus and Butyrivibrio fibrisolvens were quantified by real time PCR. In does, diet did not affect (P > 0.10) diversity indexes, total bacterial concentration or relative abundance of B. fibrisolvens, but at 28 days of lactation the proportion of R. albus was higher with LR (interaction Diet × Time, P = 0.037). Caecal communities of pups of 17 days were grouped by litter, but the influence of the mother was reduced at 28 days with solid feed intake, and at 49 days rabbits clustered by diet. Caecal biodiversity increased from 17 to 28 days, and was reduced at 49 days (Shannon index of 3.60, 3.71 and 3.57, respectively; P = 0.049). Total bacterial concentration and relative abundance of R. albus and B. fibrisolvens increased with solid feed intake from 17 to 28 days (P < 0.01), remaining unaffected thereafter. Access of pups to solid feed from 17 days of age modulates the development and composition of the caecal microbiota at weaning.

Effects of replacing dietary starch with neutral detergent–soluble fibre on ruminal fermentation, microbial synthesis and populations of ruminal cellulolytic bacteria using the rumen simulation technique (RUSITEC)

A rumen simulation technique (RUSITEC) apparatus with eight 800ml fermenters was used to investigate the effects of replacing dietary starch with neutral detergent-soluble fibre (NDSF) by inclusion of sugar beet pulp in diets on ruminal fermentation, microbial synthesis and populations of ruminal cellulolytic bacteria. Experimental diets contained 12.7, 16.4, 20.1 or 23.8% NDSF substituted for starch on a dry matter basis. The experiment was conducted over two independent 15-day incubation periods with the last 8days used for data collection. There was a tendency that 16.4% NDSF in the diet increased the apparent disappearance of organic matter (OM) and neutral detergent fibre (NDF). Increasing dietary NDSF level increased carboxymethylcellulase and xylanase activity in the solid fraction and apparent disappearance of acid detergent fibre (ADF) but reduced the 16S rDNA copy numbers of Ruminococcus albus in both liquid and solid fractions and R.flavefaciens in the solid fraction. The apparent disappearance of dietary nitrogen (N) was reduced by 29.6% with increased dietary NDSF. Substituting NDSF for starch appeared to increase the ratios of acetate/propionate and methane/volatile fatty acids (VFA) (mol/mol). Replacing dietary starch with NDSF reduced the daily production of ammonia-N and increased the growth of the solid-associated microbial pellets (SAM). Total microbial N flow and efficiency of microbial synthesis (EMS), expressed as g microbial N/kg OM fermented, tended to increase with increased dietary NDSF, but the numerical increase did not continue as dietary NDSF exceeded 20.1% of diet DM. Results suggested that substituting NDSF for starch up to 16.4% of diet DM increased digestion of nutrients (except for N) and microbial synthesis, and further increases (from 16.4% to 23.8%) in dietary NDSF did not repress microbial synthesis but did significantly reduce digestion of dietary N.

Bacterial profile from caecal contents and soft faeces in growing rabbits given diets differing in soluble and insoluble fibre levels

To verify if non-invasive collection of soft faeces (SF) from rabbits can be used as an index of bacterial biodiversity in caecal contents (CC), 24 weaned rabbits were given diets with low (LI) and high (HI) levels of insoluble fibre (neutral detergent fibre, NDF) and low (LS) and high (HS) levels of soluble fibre (neutral detergent soluble fibre, NDSF). After 21 days, animals were fitted with neck collars for SF collection. Two days later, animals were slaughtered and CC sampled. Total bacterial concentration quantified by real time PCR (log10 ng DNA/mg DM) was higher in SF than CC (2.615 vs. 2.383). Among diets, in CC it was (P = 0.059) lowest in LILS diet, whereas in SF it decreased (P = 0.025) with the NDF level. DGGE profiles showed that structure of bacterial communities of SF was close to that of CC; however, similarity was higher in LI than HI diets (0.82 vs. 0.74). Diversity indexes in CC decreased with NDSF (P < 0.05), whereas the effect of NDF (P < 0.05) was also appreciated in SF. Soft faeces can be an alternative to surgery or slaughter techniques to monitor changes in caecal bacterial community; however, high dietary NDF may decrease similarity between both communities.