Distribution of activity of hydrolytic enzymes in the digestive tract of rabbits

Effect of Diet Supplementation with Oat Hay and Whole Carrot on Rabbit Growth and Productive Efficiency

Is it possible to reduce feeding costs in rabbit meat production without compromising rabbit health and productive yield? The study tested four feeding strategies: Control group (CC) fed exclusively with concentrate feed; group CT supplemented with whole carrot; group OH supplemented with oat hay; and Group CO supplemented with oat hay and whole carrot. Each feeding strategy was tested in 20 rabbits, randomly allocated in five cages with four rabbits each. The average daily weight gain (ADG), feed conversion ratio (FCR), and the amount of concentrated feed consumed daily were estimated in all experimental groups. Group CC displayed the best ADG (37.1 g/rabbit/day), carrot had no significant influence on ADG (34.2 g/rabbit/day), but oat hay had a negative impact (p < 0.05), either used alone or in combination with carrot (33.0 and 32.6 g/rabbit/day, respectively). Supplementation with carrot, oat hay, or both increased the FCR (p < 0.001). Nevertheless, there were no significant differences in final live weight or carcass weight between the rabbits in the different experimental groups. In conclusion, supplementation with oat hay, carrot, or both can be a valid approach to reducing production costs by decreasing concentrate feed without affecting rabbit's health and meat yield. The combined supplementation with oat hay and carrot proved to be the best option in reducing the amount of concentrate feed ingested by rabbits (less than 1107 g/animal), but at current market values, supplementation exclusively with oat hay was the less expensive feeding strategy (less 14% than fed exclusively with concentrate feeding).

Effects of hemp seed and flaxseed on enzyme activity in the broiler chicken digestive tract

The activity of enzymes in the digestive tract is an important parameter for appropriate digestive tract function. Feed mixtures can be adjusted to support enzymatic activity in different parts of the digestive tract. Flaxseed and hemp seed are commodities and significant sources of nutrition, and their addition to feed could change enzymatic activity in the digestive tract and improve nutritional intake. The aim of this study was to determine the effects of flaxseed, hemp seed and a combination of both on basic enzymes in the polysaccharidase group, such as amylase, cellulase, pectinase, xylanase and inulinase; basic enzymes in the disaccharidase group, including maltase, invertase and lactase; proteinases and lipases in the digestive tract of broiler chickens. During the experiment, the control group was fed a diet without flaxseed or hemp seed. The diet of the second group contained 80 g/kg flaxseed, the diet of the third group contained 40 g/kg hemp seed, and the diets of the fourth to sixth groups contained 80 and 30 g/kg, 80 and 40 g/kg and 80 and 50 g/kg flaxseed and hemp seed, respectively. Enzyme activity was found to depend on the location in the digestive tract and the composition of the feed mixture (P < 0.05). Most enzymatic conversion occurs in the ileum, where the addition of flaxseed and hemp seed to the diet increased most enzyme activities, namely, amylase, cellulase, pectinase, xylanase, maltase, invertase, proteinase and lipase activities. The highest values of enzyme activity were found in groups IV-VI fed a combination of flaxseed and hempseed, especially in chickens fed diet VI (flaxseed and hemp seed at 80 and 50 g/kg). Growth performance results confirmed the enzyme activity results, as the weights of the chickens increased after the addition of flaxseed and/or hemp seed. The findings have economic implications, suggesting that feeding a diet with a combination of flaxseed and hemp seed is beneficial.

Dietary fumonisin may compromise the nutritive value of feed and distort copper and zinc digestibility and retention in weaned piglets

Fumonisins (FUM) have been reported to impede gut functioning in pigs. However, investigations into the possible effect on mineral metabolism are limited. Thus, the trial studied the apparent total tract digestibility (ATTD) and retention of dietary nitrogen and minerals, intestinal architecture, digestive enzymes activity and heat-shock protein 70 (Hsp70) activity. Eighteen weaned piglets of 7 weeks old were assigned to three groups and their feed either contained 0, 15 or 30 mg FUM/kg for 21 days. ATTD and retention of dietary N and minerals were measured in a 5- day long balance trial between Day 17 and Day 21. The digestible and metabolisable energy (DE and ME) content of the feeds were also determined. The body weights, cumulative feed intake, relative organ weights, digestive enzymes activity and intestinal morphology were not affected (p > 0.05) by dietary treatments. The DE content was significantly lower (p < 0.05) when the feed contained 15 mg/kg FUM, but no statistically reliable treatment effect was confirmed for ME content. Dietary FUM significantly lowered (p < 0.05) the ATTD of Ca and P but not (p > 0.05) N, K, Mg and Na. The relative retention rate of N, Ca, P, K, Mg and Na in all groups were not impacted (p > 0.05) by treatments. The ATTD and relative retention of Cu and Zn were remarkably (p < 0.05) lower in piglets fed FUM-contaminated feed. In addition, the expression of Hsp70 activity in the liver was significantly elevated (p < 0.05) in the highest treatment group. These findings suggest that a dietary dose of 15 or 30 mg FUM/kg diet distorts the nutritive value of the mixed feed, results in poor ATTD and retention rates of Zn and Cu, and elevate Hsp70 activity in the liver without altering intestinal architecture or digestive enzymes' activity in weaned piglets.

Effect of Diet Supplementation with Enterococcus Durans ED26E/7 and its Durancin ED26E/7 on Growth Performance, Caecal Enzymatic Activity, Jejunal Morphology and Meat Properties of Broiler Rabbits

The present study investigates the effects of Enterococcus durans ED26E/7 beneficial strain and its enterocin – durancin (Ent) ED26E/7 on selected parameters in rabbits: growth performance, caecal enzymatic activity, jejunal morphometry and meat physico-chemical characteristics. Seventytwo rabbits (aged five weeks, M91 meat line, both sexes) were divided into experimental groups E1 (E. durans ED26E/7 strain; dose 500 μL/animal/day, concentration 109 CFU/mL) and E2 (durancin EntED26E/7; dose 50 μL/animal/day, with activity 12 800 AU/mL) and control group (C). The additives were administered in drinking water for a period of 21 days. All animals remained in good health during the experiment. The highest body weight gain (increase by 1.5% compared to C) was noted in E1 group during ED26E/7 strain application (P<0.001). Both bioactive compounds positively influenced (reduced) the feed conversion ratio (P<0.001). The ED26E/7 strain and its EntED26E/7 application stimulated the activity of most enzymes tested in the caecum; only the amylolytic and inulolytic activity in E2 group decreased during durancin ED26E/7 addition. Both additives, but mainly the ED26E/7 strain, showed a tendency to improve the jejunal morhological parameters till the end of the experiment (day 42). The meat physico-chemical parameters were not negatively influenced by the application of E. durans ED26E/7 strain and its durancin ED26E/7. The diet supplementation with bacteriocinogenic and probiotic E. durans ED26E/7 strain and its EntED26E/7 may improve the growth performance, caecal enzymatic activity and jejunal morphometry of rabbits, without any negative effect on rabbit meat quality.

Enterocin M and Sage Supplementation in Post-weaning Rabbits: Effects on Growth Performance, Caecal Microbiota, Fermentation and Enzymatic Activity

The effects of enterocin (Ent) M and sage extract applied separately and in combination were investigated. EntM (E 50 μL/animal/day in water) and sage extract (S 10 μL/animal/day in water) were applied individually and in combination (E+S) to rabbits during 21 days of treatment. The rabbits' growth was not significantly influenced by the additives. Lower feed conversion (FC) was noted in the experimental groups compared with controls, with the lowest data detected in E. The antimicrobial activity of EntM was noted (in E+S: lactic acid bacteria-P < 0.01; in E, E+S: enterococci, enterobacteria-P > 0.05; in E: clostridia-P > 0.05). The most significant changes in fermentation between weaned and older rabbits were noted in amylolytic activity at day 21 (E P < 0.05; E + S P < 0.05); prolonged reduction effect of sage extract on amylolytic activity was observed. The activity of cellulase, pectinase and xylanase was higher in older than in younger animals. Decrease in lactic acid and volatile fatty acids was noted during EntM administration, with significant effect on propionic acid concentration (E P < 0.05; E+S P < 0.001). The sage extract reduced propionic acid (S P < 0.001) and butyric acid levels (S P < 0.05) and increased the concentrations of butyric, iso-valeric, valeric, caproic acids and lactic acid (P < 0.001). It seems to be that EntM and sage supplementation may improve the economy of rabbit farms (increased FC) and the health status of rabbits (reduction of spoilage microbiota, enhanced enzymatic activities in caecum).

Enterocins as Novel Feed Additives in Rabbit Diet: Enterocin Ent M and Durancin Ent ED26E/7, Their Combination, and Effects on Microbiota, Caecal Fermentation, and Enzymatic Activity

The present study investigates the effects of enterocin Ent M and durancin Ent ED26E/7 applied separately and in combination on the intestinal microbiota, caecal enzymatic activity, and fermentaion of rabbits. Eighty rabbits (M91 meatline, aged 5 weeks, both sexes) were divided into groups E (Ent M; 50 µL/animal/day), D (Ent ED26E/7; 50 µL/animal/day), E + D (Ent M + Ent ED26E/7), and control (C). The additives were administered in drinking water for 21 days. Antimicrobial activity of Ent M and Ent ED26E/7 on coliforms (E, E + D: P < 0.001) and pseudomonads (D: P < 0.05) in feces was noted, compared to C. Ent M and Ent ED26E/7 application stimulated caecal enzymatic activity in rabbits. Pectinolytic (E vs. D, E + D: P < 0.01), inulolytic (E vs. E + D: P < 0.01; E vs. C: P < 0.05), and amylolytic (E vs. D, E + D. P < 0.001; E vs. C: P < 0.01) activities were influenced by Ent M, while cellulolytic (D vs. E + D: P < 0.01) and inulolytic (D vs. E + D, C: P < 0.01) activities by Ent ED26E/7 treatment. The cellulolytic and pectinolytic acitivities changed with time. Treatment × time interaction was detected for cellulose and xylan degradation. During Ent M and Ent ED26E/7 treatment, increased ammonia, lactic, butyric and iso-valeric acid, and lower acetic, propionic, iso-butyric, valeric, and caproic acid concentrations were noted. It can be concluded that Ent M and Ent ED26E/7 application can improve rabbit health due to reduced spoilage microbiota and enhanced caecal enzymatic activity.

Untargeted Metabolomics Reveals Intestinal Pathogenesis and Self-Repair in Rabbits Fed an Antibiotic-Free Diet

The prohibition of the use of growth-promoting drug additives in feeds was implemented in China in 2020. However, rabbits can experience symptoms of intestinal disease, such as diarrhea and flatulence, when switching from standard normal diets with antibiotics to antibiotic-free diets. The molecular mechanisms related to the occurrence of these diseases as well as associated physiological and metabolic changes in the intestine are unclear. Thus, the objectives of this study were to study the pathogenesis of intestinal inflammation using untargeted metabolomics. This was done to identify differential metabolites between a group of antibiotic-free feed Hyplus rabbits (Dia) whose diet was abruptly changed from a standard normal diet with antibiotics to an antibiotic-free diet, and an antibiotic diet group Hyplus rabbits (Con) that was fed a standard normal diet with antibiotics. Morphological damage to the three intestinal tissues was determined through visual microscopic examination of intestinal Dia and Con tissue samples stained with hematoxylin and eosin (HE). A total of 1969 different metabolites were identified in the three intestinal tissues from Dia and Con rabbits. The level of 1280 metabolites was significantly higher and the level of 761 metabolites was significantly lower in the Dia than in the Con group. These differential metabolites were involved in five metabolic pathways associated with intestinal inflammation (tryptophan metabolism, pyrimidine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, lysine degradation, and bile secretion). Rabbits in the Dia group developed metabolic disorders that affected the intestinal microbiota and changed the permeability of the intestinal tract, thereby triggering intestinal inflammation, affecting feed utilization, reducing production performance, and activating the intestinal tract self-repair mechanism. Thus, the abrupt transition from a diet with antibiotics to an antibiotic-free diet affected the structure and metabolism of the intestinal tract in Hyplus rabbits. Consequently, to avoid these problems, the antibiotic content in a rabbit diet should be changed gradually or alternative antibiotics should be found.

In vitro digestion of polysaccharides: InfoGest protocol and use of small intestinal extract from rat

Starch, dextran, pectin and modified citrus pectin were subjected to intestinal digestion following InfoGest protocol and a rat small intestine extract (RSIE) treatment. Gastric stage did not show any modification in the structure of the carbohydrates, except for modified pectin. Regarding intestinal phases, starch was hydrolyzed by different ways, resulting in a complementary behavior between InfoGest and RSIE. Contrarily, digestion of dextran was only observed using RSIE. Similar situation occurred in the case of pectins with RSIE, obtaining a partial hydrolysis, especially in the modified citrus pectin. However, citrus pectin was the less prone to hydrolysis by enzymes. The results demonstrated that InfoGest method underestimates the significance of the carbohydrates hydrolysis at the small intestine, thus indicating that RSIE is a very reliable and useful method for a more realistic study of polysaccharides digestion.

Urea hydrolysis by gut bacteria in a hibernating frog: evidence for urea-nitrogen recycling in Amphibia

Gut bacteria that produce urease, the enzyme hydrolysing urea, contribute to nitrogen balance in diverse vertebrates, although the presence of this system of urea-nitrogen recycling in Amphibia is as yet unknown. Our studies of the wood frog (Rana sylvatica), a terrestrial species that accrues urea in winter, documented robust urease activity by enteric symbionts and hence potential to recoup nitrogen from the urea it produces. Ureolytic capacity in hibernating (non-feeding) frogs, whose guts hosted an approximately 33% smaller bacterial population, exceeded that of active (feeding) frogs, possibly due to an inductive effect of high urea on urease expression and/or remodelling of the microbial community. Furthermore, experimentally augmenting the host's plasma urea increased bacterial urease activity. Bacterial inventories constructed using 16S rRNA sequencing revealed that the assemblages hosted by hibernating and active frogs were equally diverse but markedly differed in community membership and structure. Hibernating frogs hosted a greater relative abundance and richer diversity of genera that possess urease-encoding genes and/or have member taxa that reportedly hydrolyse urea. Bacterial hydrolysis of host-synthesized urea probably permits conservation and repurposing of valuable nitrogen not only in hibernating R. sylvatica but, given urea's universal role in amphibian osmoregulation, also in virtually all Amphibia.

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>

The effect of cellobiose on the health status of growing rabbits depends on the dietary level of soluble fiber

The aim of this study was to examine whether the combination of dietary soluble fiber and cellobiose exerts a synergistic effect on growth performance, health status, fermentation traits, and immune response in rabbits. Six treatments in a 3 × 2 factorial arrangement were used: 3 cellobiose concentrations in drinking water (0.0, 7.5, and 15.0 g/L) × 2 dietary levels of soluble fiber (84.0 and 130 g/kg DM, for the low soluble fiber [LSF] and high soluble fiber [HSF] diets, respectively). A total of 318 young rabbits (53/treatment) were weaned at 34 d of age and had ad libitum access to feed and water. At 46 d of age, 9 rabbits/treatment were slaughtered and ileal and cecal digesta were collected to analyze VFA profile and the immune response in the cecal appendix mucosa. At 48 d of age, the cellobiose supplementation was withdrawn and the experimental diets were replaced by a standard commercial diet until 61 d of age. From 34 to 48 d of age, there was a linear increase of mortality with the level of cellobiose in the HSF group (0% vs. 17.1%; P = 0.017). In contrast, a quadratic effect of cellobiose level on mortality was observed in the LSF group, the rabbits offered 7.5-cellobiose showing the lowest mortality (5.7% vs. 21.4%; P = 0.030). Cellobiose level had a quadratic effect on ADFI, ADG, and G:F in this period (P ≤ 0.047), with the 7.5-cellobiose groups having the best growth performance. In contrast, only minor changes on these traits were observed from 48 d of age onwards. Cellobiose level influenced quadratically the ileal VFA concentrations (P = 0.014), showing the maximal value in the 7.5-cellobiose groups. In rabbits fed 7.5-cellobiose-LSF, a change of acetate to propionate, butyrate, and valerate was observed in the ileum. Increasing cellobiose levels reduced linearly cecal VFA concentrations in HSF fed rabbits, but no effect was detected in LSF groups (P = 0.046). The level of soluble fiber increased VFA concentrations in both the ileum (by 22%; P < 0.001), and the cecum (by 11%; P = 0.005). The relative gene expression of IL-6, IL-10, TNF-α, iNOS, MUC-1, and toll-like receptors (TLR-2 and TLR-4) in the cecal appendix increased linear and quadratically with increasing levels of cellobiose (P ≤ 0.063). In conclusion, in rabbits fed LSF diets, a dose of 7.5 g cellobiose/L drinking water would be recommended, whereas these levels of cellobiose supplementation should be avoided in rabbits fed HSF diets.

Ureases in the gastrointestinal tracts of ruminant and monogastric animals and their implication in urea-N/ammonia metabolism: A review

Urea in diets of ruminants has been investigated to substitute expensive animal and vegetable protein sources for more than a century, and has been widely incorporated in diets of ruminants for many years. Urea is also recycled to the fermentative parts of the gastrointestinal (GI) tracts through saliva or direct secretory flux from blood depending upon the dietary situations. Within the GI tracts, urea is hydrolyzed to ammonia by urease enzymes produced by GI microorganisms and subsequent ammonia utilization serves the synthesis of microbial protein. In ruminants, excessive urease activity in the rumen may lead to urea/ammonia toxicity when high amounts of urea are fed to animals; and in non-ruminants, ammonia concentrations in the GI content and milieu may cause damage to the GI mucosa, resulting in impaired nutrient absorption, futile energy and protein spillage and decreased growth performance. Relatively little attention has been directed to this area by researchers. Therefore, the present review intends to discuss current knowledge in ureolytic bacterial populations, urease activities and factors affecting them, urea metabolism by microorganisms, and the application of inhibitors of urease activity in livestock animals. The information related to the ureolytic bacteria and urease activity could be useful for improving protein utilization efficiency in ruminants and for the reduction of the ammonia concentration in GI tracts of monogastric animals. Application of recent molecular methods can be expected to provide rationales for improved strategies to modulate urease and urea dynamics in the GI tract. This would lead to improved GI health, production performance and environmental compatibility of livestock production.

Effect of weaning diet and weaning age on growth, body composition and caecal fermentation of young rabbits

Two weaning diets (C and S) and three weaning ages (21, 25, and 28 days) were compared in a two factorial arrangement to evaluate their effect on growth performance, body composition and caecal fermentation activity of young rabbits. One hundred litters born the same day from multiparous does were used. Sixty litters were early weaned at 21, 25 and 28 days of age (20 litters per weaning age), put in collective cages (nine kits per cage) (W21, W25, and W28 litters) and offered the control diet C (crude protein (CP) : 175 g/kg dry matter (DM); ether extract : 20 g/kg DM; starch : 157 g/kg DM; acid-detergent lignin (ADL) : 60 g/kg DM; digestible energy (DE) : 11·08 MJ/kg DM) or the starter diet S (CP : 173 g/kg DM; ether extract : 41 g/kg DM; starch : 112 g/kg DM; ADL : 51 g/kg DM; DE : 11·31 MJ/kg DM). At 32 days of age, 180 early weaned rabbits (three rabbits from each of the 60 litters above) were selected : 60 animals were slaughtered; 120 animals were placed into individual cages and offered a fattening diet (CP : 166 g/kg DM; ether extract : 23 g/kg DM; starch : 177 g/kg DM; ADL : 49 g/kg DM; DE : 11·26 MJ/kg DM) from 32 to 56 days of age. At 56 days of age, another 60 representative rabbits were slaughtered. The administration of diet S to the early weaned rabbits increased litter weight at 32 days (6160 v. 6027 g;P<005) and gain to food ratio from weaning to 32 days (752 v 666 g/kg;P<0001) compared with diet C. Moreover, empty bodies (EB) of S rabbits were fatter (fat : 45 v. 41 g/kg; P = 001) and had greater energy content (5·92 v 5·71 MJ/kg;P<001). At 56 days of age, no residual effect of the diet was recorded. Weaning age affected growth performance, body composition and caecal fermentation at 32 days of age : EB weight (P<005) and EB protein concentration increased (from 164 to 168 g/kg,P<0·01) while caecal volatile fatty acid concentration decreased (from 71·7 to 53·8 mmol/l;P<0·01) when weaning age was increased from 21 to 28 days. At 56 days of age, no effect (P > 0·05) of weaning age was recorded on growth performance or caecal fermentation traits, but EB protein remained lower in the earliest weaned rabbits (P<0·05). In conclusion, feeding a high-fat low-starch diet to early weaned rabbits stimulated growth and body fat and energy retention of kits at 32 days of age with no effect on caecal fermentation. The early weaning successfully performed at 21 days of age strongly stimulated caecal fermentation but reduced body protein reserves.

Feeding strategy for young rabbits around weaning: a review of digestive capacity and nutritional needs

The digestive maturation of the young rabbit is reviewed. It indicates that their nutritional needs and those of lactating females are antagonistic in many aspects. Energy requirements of lactating females are very high, whilst a low starch, high fibre diet around weaning improves the health of the young after weaning. To solve this problem, several feeding and management strategies are presented and discussed. If weaning occurs between 28 and 35 days of age, feeding the young with a specific diet, different from the female’s, seems an effective solution. Otherwise, it is necessary to find a compromise between the needs of the litter and of the doe. Early weaning (< 26 days) could be also a promising way to provide adequate feeding for the young as soon as they begin to eat solid food.

Effect of fibre source on ileal apparent digestibility of non-starch polysaccharides in rabbits

Sixteen New Zealand White ✕ Californian doe rabbits (four per diet) weighing 3397 (s.e. 378) g, and surgically fitted with a glass T-cannula at the terminal ileum were used to determine the apparent ileal digestibility of non-starch polysaccharides of four fibrous foods. Four diets were formulated to contain paprika meal, olive leaves, lucerne hay or soya-bean hulls as the sole source of fibre. Fibre sources were supplemented with different proportions of soya protein isolate, wheat flour, lard, sodium chloride, calcium carbonate, calcium phosphate, DL-methionine and a mineral/vitamin mix, to obtain diets containing at least 185 g crude protein and 50 g starch per kg. All diets included 2 g/kg of the respective fibre source marked with chromium. Diets were assigned to individually caged rabbits in a completely randomized design and were offered ad libitum throughout the experiment. Dry matter intake was not affected by type of diet. Fibre source affected (P< 0·05) corrected ileal apparent digestibility of total non-strach polysaccharides (NSP), xylose, galactose, glucose and uronic acids. Uronic acids were the best digested monomer at the ileum in all the foodstuffs studied, ranging from 0·195 to 0·522 for olive leaves and paprika meal, respectively. Corrected ileal apparent digestibility of uronic acids was correlated with the uronic acids insoluble in NDF solution, expressed as proportion of total uronic acid content (r=–0·74;P= 0·001), the proportion of large particles (> 1·25 mm;r= –0·71;P< 0·01) and the proportion of fine particles (< 0·315 mm;r= 0·65;P= 0·01). Other monomers (arabinose, mannose, rhamnose and galactose) usually related to pectic substances, also showed in general a greater ileal digestibility than that of total NSP. Taking into account the uronic acids content of the diet and their digestibility, digestible uronic acids accounted for 0·572, 0·528, 0·93 and 0·353 of the total ileal digestible NSP of paprika meal, olive leaves, lucerne hay and soya-bean hulls based diets, respectively. The sum of arabinose, mannose, rhamnose and galactose accounted for 0·15 of total NSP digested at the ileum on average, over the different fibre sources studied. Glucose and xylose were the monomers least digested at the ileum. Their corrected ileal apparent digestibilities were close to zero, except for the paprika meal (0·266 and 0·216) and soya-bean hulls (0·137 and 0·057) based diets. In conclusion, the results of this study indicate that a valuable amount of total NSP is hydrolysed before the caecum in rabbits. However, this hydrolysis affects mainly pectic and readily fermentable substances.

Enzymatic Formation of Novel Ginsenoside Rg1-α-Glucosides by Rat Intestinal Homogenates

The variation of linkage positions in ginsenosides leads to diverse pharmacological efficiencies. The hydrolysis and transglycosylation properties of glycosyl hydrolase family enzymes have a great impact on the synthesis of novel and structurally diversified compounds. In this study, six ginsenoside Rg1-α-glucosides were found to be synthesized from the reaction mixture of maltose as a donor and ginsenoside Rg1 as a sugar acceptor in the presence of rat small intestinal homogenates, which exhibit high α-glucosidase activities. The individual compounds were purified and were identified by spectroscopy (HPLC-MS, (1)H-NMR, and (13)C-NMR) as 6-O-[α-D-glcp-(1→4)-β-D-glcp]-20-O-(β-D-glcp)-20(S)-protopanaxatriol, 6-O-β-D-glcp-20-O-[α-D-glcp-(1→6)-(β-D-glcp)]-20(S)-protopanaxatriol, 6-O-β-D-glcp-20-O-[α-D-glcp-(1→4)-(β-D-glcp)]-20(S)-protopanaxatriol, 6-O-[α-D-glcp-(1→6)-β-D-glcp]-20-O-(β-glcp)-20(S)-protopanaxatriol, 6-O-[α-D-glcp-(1→3)-β-D-glcp]-20-O-(β-D-glcp)-20(S)-protopanaxatriol, and 6-O-β-D-glcp-20-O-[α-D-glcp-(1→3)-(β-D-glcp)]-20(S)-protopanaxatriol. Among these six, 6-O-β-D-glcp-20-O-α-D-glcp-(1→6)-(β-D-glcp)-20(S)-protopanaxatriol and 6-O-α-D-glcp-(1→6)-β-D-glcp-20-O-(β-D-glcp)-20(S)-protopanaxatriol are considered to be novel compounds of alpha-ginsenosidal saponins which pharmacological activities should be further characterized. This is the first report on the enzymatic elaboration of ginsenoside Rg1 derivatives using rat intestinal homogenates. To the best of our knowledge, it is also the first to reveal the sixth and 20th positions of an unusual α-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl sugar chain with 20(S)-protopanaxatriol saponins in Panax ginseng Mayer.

Dietary fibres in the nutrition of the growing rabbit and recommendations to preserve digestive health: a review

The importance of dietary fibre fractions in animal feeding is due to its influence on the rate of passage, mucosal functionality and its role as substrate for gut microbiota that relates to performance and digestive health. The complexity of the physical structure and chemical composition of polysaccharides in plant cell walls explains the wide and different physiological effects of this large range of fibre fractions. Our review will first briefly consider the definition and structure of the different classes of fibres and of cell wall constituents, followed by a description of some analytical methods employed for monogastric feeds. Second, the nutritional role and impact of fibre intake on digestive health will be described for the growing rabbit with an extensive analysis of previous studies performed without antibiotics. The fibres in rabbit feed are essential for reducing the risk of digestive trouble after weaning, and the requirements are defined in terms of the quantity and quality of the fibre fractions as follows: a minimal dietary level of lignocellulose 'ADF' (18%) and lignins (>5%), balanced with a maximum quantity of digestible fibres 'DgF' (ratio DgF/ADF below 1.3). Soluble fibres, defined as the difference between total dietary fibre and NDF, are quickly fermented and digested by the rabbit. However, their impact on digestive health is still questioned.

In vitro and in vivo digestion of octenyl succinic starch

This study aimed to understand effects of octenyl succinic anhydride (OSA) modification of normal corn (NCS) and high-amylose corn (HA7) starch on their enzymatic hydrolysis rates. After modification with 3% and 10% OSA, resistant starch (RS) contents of the cooked OS-NCS increased from 0.8% of the control starch to 6.8% and 13.2% (Englyst Method), respectively, whereas that of the cooked OS-HA7 decreased from 24.1% to 23.7% and 20.9%, respectively. When the cooked NCS, HA7 and OS (10%)-HA7 were used to prepare diets for rats at 55% (w/w) starch, RS contents of the diets were 1.1%, 13.2% and 14.6%, respectively. After feeding to the rats, 20.2-31.1% of the starch in the OS (10%)-HA7-diet was not utilized in vivo and was found in rat feces, which was substantially larger than that of the HA7-diet (≤4.9%) and NCS-diet (≤0.2%). The body weights of the rats, however, remained similar between different groups.

Effect of a starter diet supplementation with mannan-oligosaccharide or inulin on health status, caecal metabolism, digestibility of nutrients and growth of early weaned rabbits

The effect of a dietary supplementation with mannan-oligosaccharide (MOS, Bio-Mos, Alltech Inc.) and inulin (Frutafit® IQ) on growth, health, and caecal traits was studied on 348 rabbits (Hyplus®), weaned at 25 days of age. Three hundred and thirty rabbits (110 per group) were used for the health status and growth performance trial, while 18 rabbits (six per group) were used for caecal metabolism evaluation at the age of 42 days of age. Three diets were formulated: C (control), M (0.3% MOS) and I diet (4% inulin). Digestibility of the diets was measured in 10 rabbits per group between 36 and 40 days of age. The control diet was fed to rabbits of the C group from weaning to 74 days of age (slaughter). Diets M and I were fed to rabbits of the respective group from weaning to 46 days of age, then were fed with control diet till slaughter. From 25 to 46 days of age, the weight gain was slightly higher in control rabbits ( P = 0.11), while no differences were recorded for the whole period. No differences among groups in the mortality, which was high due to an enteropathy-infected environment, were significant. The lowest morbidity ( P = 0.05) as well as the health risk index were recorded in rabbits fed the diet with inulin ( P = 0.03). After change of diet, the health risk index increased in the rabbits previously fed the diet with additives, thereby no significant differences in the health status were recorded for the whole period. Total caecal volatile fatty acids concentration was higher ( P < 0.01) and the pH ( P < 0.01) and ammonia concentration ( P = 0.01) lower in rabbits fed the inulin diet than in other rabbits. In these animals, acetate molar proportion was higher ( P = 0.01) and that of propionate as well as the propionate/butyrate ratio significantly lower than in other rabbits. Butyrate molar proportion was higher in rabbits fed the diet with MOS ( P < 0.01). In rabbits fed the inulin diet a higher activity of inulinase was recorded ( P < 0.001) than in other rabbits. A significantly lower digestibility of cellulose was observed in rabbits fed the diet with MOS. The results of our study suggest the importance of using inulin-type fructans in the nutrition of young rabbits. The higher health risk index of rabbits after change of diets indicates that prebiotics should be given for a longer time during the fattening period.

Adaptability of the digestive function according to age at weaning in the rabbit: I. Effect on feed intake and digestive functionality

The functional adaptability of the digestive system to the level of feed intake was investigated in the young rabbits by comparing two groups of 12 litters each, weaned at 21 (W21) or 35 (W35) days of age. From 14 days onwards, rabbits were fed a pelleted feed (NDF: 332 g/kg, CP: 177 g/kg, starch: 98 g/kg, as-fed basis). Until 49 days of age, the profile of digestive enzymes was weekly determined in the small intestinal content and mucosa, as well as caecal fermentation traits and fibrolytic activities. In the W21 group, the solid feed intake was increased by 57% between 21 and 35 days (P < 0.01), while the daily body growth was lower from 21 till 42 days (-17%, P < 0.05) when compared with the W35 group. Activities of enzymes of pancreatic origin were only scarcely influenced by the weaning age. In the W21 group, amylase activity tended to be lower at 28 days of age (-36%, P = 0.064), and trypsin activity was decreased by 31% at 49 days of age (P < 0.01). Lipase activity was similar in both weaning groups. Duodenal and jejunal activities of maltase and aminopeptidase N (APN) were higher on day 28 in the W21 group as compared with the W35 group (×1.4 to ×2.4, respectively, P < 0.05). On day 35, duodenal APN activity was twice as higher in the W21 group than in the W35 group (P < 0.01). In caecum, major differences between both weaning groups were observed at 28 days of age with a decrease in ammonia concentration (-43%, P < 0.01) in W21 compared with W35 rabbits. Conversely, the acetate proportion was 5% higher in the W21 group (P < 0.01) on day 28. In conclusion, the digestive tract of early-weaned rabbits showed some adaptative properties in response to nutritional environment changes, but they were insufficient to maintain their growth rate.

The activity of some digestive enzymes in domestic rabbits before and after weaning

The activity ofamylase, maitase, lipase, pepsin, trypsin and chymotrypsin in suckling (15 days of age) and in 1-day weaned (43 days of age) domestic rabbits was assayed and compared with older (90 and 180 days) rabbits. It was found that amylase was active in the pancreas at 15 days (11 580 amylase units (AU) per mg protein) and increased during growth, reaching a maximum level (58 960 AU per mg protein) at 90 days of age. Specific activity (SA) of maitase from the small intestine mucosa varied depending on the intestinal segment and the age of the rabbits: activity in the duodenal mucosa decreased, while in the jejunal and Heal mucosa activity increased, during growth. Lipase SA reached a maximum level in suckling rabbits at the age of 15 days (in gastric mucosa 242 and in pancreas 608 mequiv. liberated oleic acid per mg protein per h, 37°C) and decreased sharply at weaning: in gastric mucosa down to 86 and in pancreas down to 89 mequiv. oleic acid per mg protein per h, 37°C. SA of pepsin remained relatively constant for all the studied categories of rabbits: 38 to 39 nmol tyrosine per mg protein per min, 25°C. Trypsin and chymotrypsin SA reached a peak at about weaning: 1·83 nmol benzoyl-arginyl-ethyl-ester per mg protein per min, 25°C and 40·1 nmol benzoyl-phenyl-naphtyl-ester per mg protein per min, 35·5°C respectively.

Influence of polymers on the bioavailability of microencapsulated celecoxib

Celecoxib, a selective COX-2 inhibitor, primarily used in treatment of osteoarthritis, rheumatoid arthritis and acute pain was encapsulated in microparticles composed of various polyesters, polymethacrylates or cellulose derivatives used alone or blended. The influence of polymers on microparticle mean diameter, encapsulation efficiency and in vitro and in vivo celecoxib release was investigated. Microparticles were in the size range 11-37 microm. Encapsulation efficiency was optimal due to poor aqueous solubility of celecoxib. Considering in vitro release, microparticles could be divided into drug delivery systems with fast and slow release profiles. Microparticles prepared with poly-epsilon-caprolactone, Eudragit RS and low viscosity ethylcellulose, together with physical mixture of celecoxib with lactose and Celebrex, were tested in vivo. Relative bioavailability of celecoxib was below 20% in all cases and was probably the consequence of a slow in vivo release of celecoxib from microparticles or low wettability in the case of Celebrex and physical mixture.

Maturation of the intestinal digestion and of microbial activity in the young rabbit: Impact of the dietary fibre:starch ratio

The developmental changes of intestinal digestive potential and caecal microbial activity were described in suckling and weaned rabbits according to two feeding programmes. Two groups of thirteen litters were fed from 18 to 42 days old a "High" or a "Medium" NDF:starch ratio diet (resp. 2.7 vs 2.0, groups HL and ML) with similar protein and lipid levels, and from 42 to 70 days old the two groups were fed a "Low" NDF:starch ratio diet (1.7). From 25 to 32 days (weaning), the milk and solid feed intake were 22% and 41% higher in ML group (P<0.05), and the mortality by diarrhoea was 4 units lower (P<0.01). The whole tract digestive efficiency increased by 10% before weaning, and remained steady (organic matter) or decreased (lipids, protein) after weaning. Energy digestibility was 0.623 and 0.686 for High and Medium diets respectively. From 25 to 42 days, total enzymatic activity in intestinal content increased for chymotrypsin (5-fold, P<0.001), lipase (10-fold, P<0.001), amylase (17-fold, P<0.01) and maltase (11-fold, P<0.001), while trypsin doubled after weaning. The feeding programme only affected the amylase and maltase activities, that were higher in HL group (P<0.05). The volatile fatty acids concentration in the caecum was not significantly different among the groups, but it increased by 44% 10 days after weaning. The bacterial fibrolytic enzymes, increased by 30% after weaning and were similar among the two groups. The study revealed that the intestinal digestive maturation and the caecal microbial activity of the rabbit evolved markedly between 3 and 5 weeks of age, and was weakly affected when the NDF:starch ratio decreased from 2.7 to 2.0.

Neutral detergent-soluble fiber improves gut barrier function in twenty-five-day-old weaned rabbits1

The effect of neutral detergent-soluble fiber level on gut barrier function and intestinal microbiota was examined in weaned rabbits. A control diet (AH) containing 103 g of neutral detergent-soluble fiber/ kg of DM included alfalfa hay as main source of fiber. Another diet (B-AP) was formulated by replacing half of the alfalfa hay with a mixture of beet and apple pulp resulting in 131 g of soluble fiber/kg of DM. A third diet (OH) was obtained by substituting half of the alfalfa hay with a mix of oat hulls and a soybean protein concentrate and contained 79 g of soluble fiber/kg of DM. Rabbits weaned at 25 d and slaughtered at 35 d were used to determine ileal digestibility, jejunal morphology, sucrase activity, lamina propria lymphocytes, and intestinal microbiota. Suckling 35-d-old rabbits were used to assess mucosa morphology. Mortality (from weaning to 63 d of age) was also determined. Villous height of the jejunal mucosa increased with soluble fiber (P = 0.001). Rabbits fed with the greatest level of soluble fiber (BA-P diet) showed the highest villous height/ crypt depth ratio (8.14; P = 0.001), sucrase specific activity (8,671 mumol of glucose/g of protein; P = 0.019), and the greatest ileal starch digestibility (96.8%; P = 0.002). The opposite effects were observed in rabbits fed decreased levels of soluble fiber (AH and OH diets; 4.70, 5,848 mumol of glucose/g of protein, as average, respectively). The lowest ileal starch digestibility was detected for animals fed OH diet (93.2%). Suckling rabbits of the same age showed a lower villous height/crypt depth ratio (6.70) compared with the B-AP diet group, but this ratio was higher than the AH or OH diet groups. Lower levels of soluble fiber tended (P = 0.074) to increase the cellular immune response (CD8+ lymphocytes). Diet affected IL-2 production (CD25+, P = 0.029; CD5+CD25+, P = 0.057), with no clear relationship between soluble fiber and IL-2. The intestinal microbiota biodiversity was not affected by diets (P >/= 0.38). Rabbits fed the B-AP and AH diets had a reduced cecal frequency of detection compatible with Campylobacter spp. (20.3 vs. 37.8, P = 0.074), and Clostridium perfringens (4.3 vs. 17.6%, P = 0.047), compared with the OH diet group. Moreover, the mortality rates decreased from 14.4 (OH diet) to 5.1% (B-AP diet) with the increased presence of soluble fiber in the diet. In conclusion, increased levels of dietary soluble fiber improve mucosal integrity and functionality.

Effect of a high fibre intake on the resistance of the growing rabbit to an experimental inoculation with an enteropathogenic strain ofEscherichia coli

Response to an experimental infection with an enteropathogenicE. coliO103 strain (EPEC) was assessed in growing rabbits given a high or a low dietary fibre diet (200 and 120 g acid-detergent fibre per kg respectively for high ‘HF’ or low ‘LF’ fibre diet). The two experimental diets, differing in fibre level but not fibre quality, were given ad libitum from 21 days of age to two groups of 12 litters of nine pups, weaned at 28 days (trial 1) and caged collectively. At 42 days of age, the two groups were divided in two subgroups (i.e. four groups of 18 animals), inoculated or not with an EPEC O103 strain. Two further groups of 48 rabbits (trial 2) were given LF and HF diets from 28 days (weaning) to 70 days, and were individually housed to control precisely the food intake. Reducing the fibre level led to a lower post-weaning food intake (64 v. 85 g/days in the period from 28 to 42 days of age,P< 0·001) and digestible energy intake (0·75v.. 0·86 MJ/day,P< 0·001), causing a lower growth (proportionately 0·088 lower,P< 0·001). At 42 days of age, only 17% of rabbits had a detectable caecal saprophyteE. coliflora (over 102colony-forming units (CFU) per g, trial 1). Inoculating 6-week-old rabbits with EPEC led to moderate levels of mortality (26%). Health risk index (mortality + morbidity) was numerically higher in LF compared with HF groups (P= 0·12). The acute phase of the colibacillosis was between 3 and 10 days post inoculation. From days 7 to 14 post inoculation, a significantly higher frequency of rabbits having a high faecal excretion ofE. coli(> 105CFU per g) was found in LF than in HF rabbits (respectively 65 v. 26·7%,P= 0·04). The caecal pectinolytic flora reached 108CFU per g at 42 and 65 days of age, and was not affected by diet or EPEC challenge. In 42-day-old rabbits the caecal volatile fatty acid concentration was higher in HF than in LF groups (respectively 79 v. 60 mmol/l,P< 0·05), while the caecal pH was slightly lower (respectively 5·93 v. 6·09,P< 0·01). At 65 days of age, rabbits resistant to the inoculation showed a similar fermentation pattern and fibrolytic flora level to non-inoculated animals. Caecal ammonia level was not affected either by age, diet orE. colichallenge (mean = 12·1 mmol/l). From these results, we conclude that a high fibre intake improved the resistance of the growing rabbit to a specific enteropathy, in association with a higher caecal fermentative activity and lower caecal pH.

Activity and cellular localization of amylases of rabbit cecal bacteria

Five 11-week-old rabbits, fed a commercial granulated feed, were slaughtered and cecal starch-degrading bacteria enumerated; total concentration of cultivable bacteria utilizing starch averaged 5.5 x 10(10) CFU/g. The activity and cellular localization of amylases was determined in 9 bacteria identified as Actinomyces israeli (strains AA2 and AD4), Bacteroides spp. (strain AA3), Dichelobacter nodosus (strain AA4), Mitsuokella multiacidus (strain AA6), Eubacterium spp. (strains AA7 and AB2), Clostridium spp. (strains AD1 and AA5). Four strains (AA3, AA4, AA5, AD4) produced extracellular amylases with an activity of 26-35 micromol of reducing sugars per h per mg of protein; in five strains (AA2, AA6, AA7, AB2, AD1) amylases were membrane-bound with an activity of 14-18 micromol of reducing sugars per h per mg of protein. All strains exhibited a low intracellular amylolytic activity. The pH optimum of amylases was 6.8-7.0. In strains producing extracellular amylases a substantial loss of viscosity was observed during incubations of cultivation supernatant with starch, similar to viscosity reduction in starch solutions treated with alpha-amylase; this indicates an endo-type (random cleavage) of extracellular amylase reaction in the bacteria under study. No strain possessed glucoamylase activity.

Nutritional and sanitary statuses alter postweaning development of caecal microbial activity in the rabbit

The postweaning development of caecal microbial activity was studied in the rabbit according to the sanitary status (conventional "C" vs. specified pathogen-free "SPF") and the nutritional status (standard-fibre "SF" vs. deficient-fibre "DF" diet). The two diets were distributed ad libitum from weaning (28 days) to 70 days of age, respectively, to 80 C and 72 SPF rabbits. From 28 to 42 days, the volatile fatty acids concentration in the caecum (tVFA) of C rabbits was 50 mM/L and increased by 46% between 42 and 56 days, without interactions with the diet effect. In parallel, the bacterial fibrolytic activity decreased for xylanase and CMCase (-32% and -60%, respectively, P<0.05), while pectinase activity decreased more regularly from 28 to 70 days (-28%, P<0.05). At weaning, tVFA was similar among C or SPF rabbits, while at 70 days, it decreased by 23% for SPF and increased in C group (+31%). Cellulasic and hemicellulasic activity of bacteria were two to three times lower, respectively, in SPF rabbits compared to conventional ones. No interaction was detected between sanitary and nutritional status at 70 days of age for the caecal fermentative activity. With the FD diet, tVFA decreased by 10%, while butyrate proportion increased by 37% (at 70 days), whatever the sanitary status. In 70-day-old rabbits (C or SPF group), pectinasic activity was reduced by 30% when rabbits were fed the FD compared to the SF one.

Digestive tract development in rabbit according to the dietary energetic source: correlation between whole tract digestion, pancreatic and intestinal enzymatic activities

The developmental changes of both pancreatic and intestinal enzymes and the influence of dietary composition on enzyme activities were followed in suckling and weaning rabbits. In addition, whole tract digestibility of nutrients was recorded in response to two dietary energetic sources. Rabbits were fed ad libitum either a low fat and high starch diet (group LF), or a high fat and high fibre diet (group HF) between d 32 and d 42, with both groups receiving a growing finishing diet thereafter. Before weaning (d 32) nutrient digestion was high (>75% for organic matter, protein or fat), and then decreased sharply, except for fat. Between d 32 and d 42, digestion in the HF group was 7.5 and 4.6% lower, respectively, for organic matter and protein, while fibre and fat digestion was higher (+14.0 and +5.0%, respectively). Between d 25 and d 42 of age, pancreatic-specific activities of trypsin and chymotrypsin did not change while those of amylase and lipase increased by 1.5- and 76- fold (P<0.05), respectively. However, total activities and relative activities expressed on a LW basis were increased after weaning as a main consequence of a specific increased organ weight and pancreatic protein content. Relative activities of trypsin and chymotrypsin increased by 63 and 56% (P<0.01) after weaning, respectively. Total activities of pancreatic enzymes measured in the total small intestinal contents increased during the same period, but the range of variations was lower than those measured in the pancreatic gland. Total activities of lipase, trypsin and chymotrypsin measured in the small intestine contents were significantly correlated with pancreas enzyme potentialities. Total small intestine activity of lipase was 58% higher (P<0.001) in HF than in LF group while the other pancreatic and intestinal enzyme activities measured were not influenced by the energetic sources of the diet. Decreased digestibility of organic matter and protein observed with the HF diet could not be related to changes in pancreatic or intestinal enzymatic profiles and may be more dependent on quality of dietary ingredients.

Isolation and characterization of rabbit caecal pectinolytic bacteria

Two hundred and thirty colonies from the caecal contents of six rabbits were picked up and, after a 2-d incubation, were microscopically characterized using Gram staining. Large Gram-negative (34%) and small Gram-negative (30%) irregular rods, Gram-negative (27%) and Gram-positive (8%) cocci were found. Eleven isolates (Bacteroides ovatus (6 strains), B. thetaiotamicron, B. caccae, B. stercoris, B. capillosus and Capnocytophaga ochracea) were identified using commercial tests for measuring their catalase activity, metabolite production, etc., and testing their growth in 20% bile. Bacteria belonging to the genus Bacteroides were demonstrated to be the principal pectinolytic organisms in the rabbit caecum.

Desempenho de coelhos em crescimento recebendo dietas com suplementação enzimática

Avaliou-se o crescimento de coelhos que receberam dietas com teores crescentes de um complexo enzimático (Vegpro®), com atividades protease e celulase. Foram utilizados 75 coelhos da raça Nova Zelândia Branco, desmamados aos 40 dias de idade e criados até aos 80 dias de idade, com peso médio de 931±34,85g, distribuídos em cinco tratamentos: A-0,00; B-0,05; C-0,10; D-0,15 e E-0,20% de suplementação enzimática. Não foram encontradas diferenças significativas (P>0,05) entre os tratamentos quanto ao consumo de ração e ao ganho de peso diário, no entanto, para a conversão alimentar o tratamento B (0,05%) foi significativamente diferente (P<0,05) do grupo controle e semelhante aos demais tratamentos. O peso da carcaça ao abate foi maior (P<0,05) nos coelhos que receberam a dieta suplementada com 0,05%, enquanto o rendimento de carcaça não foi afetado pela suplementação enzimática.

Age and incubation time effects on in vitro caecal fermentation pattern in rabbits before and after weaning

The caecal fermentation pattern was studied in four litters of rabbits. Rabbits were sequentially slaughtered at the age of 4 (before weaning), 6, 8 and 11 weeks. Their caecal contents were analyzed and incubated in vitro at 39 degrees C for 6 and 12 h. Net productions of short-chain fatty acids (SCFA), hydrogen and methane were determined. The average caecal weight increased three-times within two weeks after weaning, from 31.4 to 93.7 g. At the end of the experiment, the caecal weight was on average 134.4 g. A large variability of the SCFA concentration observed before weaning decreased after weaning. Measurements of caecal metabolite profiles and results of in vitro experiments indicated a certain decrease of propionate in favour of butyrate, associated with the weaning. The establishment of methanogens in rabbits was slow. Methanogenesis started in one out of four rabbits at the age of 6 weeks. Five weeks later, one of four rabbits still did not produce methane. The hydrogen recovery decreased between the 4th and the 6th week of age, due to the increase of the butyrate/propionate ratio. After the 6th week, the hydrogen recovery increased with age, apparently because of the increase in methane production. Hydrogen recovery tended to increase during incubation, suggesting a decrease of reductive acetogenesis. This increase was observed both in methanogenic and non-methanogenic rabbit caecal cultures. In former cultures, the ratio CH4/SCFA rose with time of incubation.