Microbial activity in the caecum of the rabbit around weaning: impact of a dietary fibre deficiency and of intake level

Effects of JUNCAO Ganoderma lucidum polysaccharide peptide on slaughter performance and intestinal health of Minxinan black rabbits

This experiment was conducted to investigate the effects of JUNCAO Ganoderma lucidum polysaccharide peptide (JCGLPP) on slaughter performance and intestinal health of Minxinan black rabbits, which aimed to provide the basis for the application of JCGLPP in meat rabbits. One hundred male weaned Minxinan black rabbits of (33 ± 2) d [(initial body mass (655.65 ± 25.90) g] were randomly divided into four groups with five replicates per group and five rabbits per replicate. The diets were supplemented with 0 (control group), 50 (group I), 100 (group II) and 150 mg·kg-1 (group III) of JCGLPP, respectively. This experiment lasted for 56 days. The results are shown below: (1) The live weight before slaughter of groups I and III was significantly higher than that of control group (p < 0.05); The full net bore weight of group III was significantly higher than that of control group (p < 0.05). (2) pH value of group I was significantly higher than that of control group (p < 0.05); NH3-N content in experimental groups were significantly higher than that in control group(p < 0.05) while NH3-N content in group I was significantly higher than that in groups III and II (p < 0.05); The content of butyric acid in group II was significantly lower than that in control group (p < 0.05); There were no significant differences in acetic acid, isovaleric acid, isobutyric acid and propionic acid in experimental groups compared with control group (p > 0.05). (3) The Occludin content in duodenum, jejunum and ileum of groups I and II was significantly higher than that of control group (p < 0.05). (4) At the phylum level, Firmicutes and Bacteroidetes were the dominant phylum in each group. At the genus level, norank_f__norank_o__Clostridia_UCG-014 in group II were significantly higher than those in control group (p < 0.05). In conclusion, although dietary JCGLPP supplementation could not improve slaughter performance of Minxinan black rabbits, it could improve cecal fermentation parameters and intestinal flora structure and composition of Minxinan black rabbits to a certain extent. Our results revealed that 100 mg·kg-1 might be the optimal concentration obtained in dietary JCGLPP supplementation, which provided ideas and feasibility for drug combination.

Effects of alfalfa (Medicago sativa L.) supplementation in the diet on the growth, small intestinal histomorphology, and digestibility of hybrid ducks

Background and Aim:

Feed plays the most important role in supporting livestock productivity. There is a need for studies on the nutrient levels in feed absorbed by the body of livestock. The aim of this study was to investigate the effects of alfalfa (Medicago sativa L.) supplementation in feed on growth, small intestinal histomorphology, and digestibility in hybrid ducks.

Materials and Methods:

The study was conducted in vivo using 75 hybrid ducks, with three treatments and five replications. Each replication consisted of five ducks. The treatments were: T0=basal ration without any alfalfa supplementation; T1=basal ration+3% fresh alfalfa supplementation; and T2=basal ration+6% fresh alfalfa supplementation. Fresh alfalfa was quantified on the basis of dry matter content. Drinking water was provided ad libitum. The observed variables were growth performance, measured in terms of feed consumption, body weight gain, and feed conversion ratio; duodenum histomorphology, measured in terms of villus height, villus width, and crypt depth; digestibility, measured in terms of dry matter digestibility; and organic matter, crude protein, and crude fiber concentrations. The data were analyzed using variance analysis with a completely randomized design of one-way pattern with Statistical Product for Service Solution application of version 22. The data with significant differences were further analyzed using Duncan’s new multiple range rest.

Results:

The results of the study showed that 3% alfalfa supplementation increased feed consumption and body weight gain of the hybrid ducks at 35 days of age compared with 0% and 6% supplementation. Furthermore, 3% alfalfa supplementation presented the best result in terms of villus height and duodenal crypt depth. Meanwhile, 6% alfalfa supplementation decreased nutrient digestibility in the ducks.

Conclusion:

These findings show that supplementation of feed with fresh alfalfa could have a significant effect on hybrid ducks in terms of growth performance, small intestinal histomorphology, and digestibility.

Impact of feed restriction and fragmented feed distribution on performance, intake behaviour and digestion of the growing rabbit

Postweaning feed restriction preserves rabbit digestive health after weaning, but the underlying physiological mechanisms are not yet understood. To elucidate whether the feeding intake pattern modification related to feed restriction might be involved, we studied the effects of both feed intake quantity and intake frequency. Animals were allotted at weaning (28 d old) in a 2 × 2 factorial design: feed intake quantity (AL = ad libitum vs R = 75% of AL) and fragmented feed distribution (FFD) (1 vs 13 distributions), thus forming four groups (AL1, AL13, R1 and R13). New Zealand White growing rabbits were used from weaning to slaughter (70 d old), to analyse mortality, morbidity, performance, intake behaviour, digestion and microbial activity. Seven days after starting feed restriction (35 d old, group R1), rabbits consumed 44% of the feed within 2 h, 65% in 4 h and in 7 h over 95%. Over the 28-70 d period, mortality was low (5.3%) while morbidity averaged 18.5% and neither was affected by treatment. However, FFD tended to decrease the morbidity rate during the first 14 days after weaning (P = 0.06). Feed conversion (28-70 d) was improved by restriction (+15%, P < 0.001) and by FFD (+5%, P < 0.001). Nutrient digestibility was improved by restriction (+10% for energy, P < 0.01), but not by FFD. Fragmented feed distribution led to a lower stomachal pH, in the antrum (1.48 vs 2.13, P < 0.001) and in the fundus (1.52 vs 2.63, P < 0.001), while a higher pH was found in the caecum (6.07 vs 5.86, P < 0.001). Butyrate proportion in the caecum was reduced by four units for restricted groups. Fragmented feed distribution reduced the caecal VFA concentration by 23% within restricted rabbit groups only. A similar interaction between intake level and FFD was observed for fibrolytic activity (cellulase and xylanase). The diversity of caecal bacterial community was not modified by either of the two factors studied. Globally, fragmented meals have no major impacts on the caecal microbial activity, diversity, and thus would not be implicated in the better resistance of restricted rabbit to digestive troubles.

Ameliorative effects of oral ginger and/or thyme aqueous extracts on productive and reproductive performance of V-line male rabbits

The objective of this study was to determine the impact of ginger and/or thyme aqueous extracts administration on the growth rate, caecum activity, reproductive performance and semen quality of rabbits. A total of 24 V-line male rabbits at the age of 12 weeks were divided randomly into four equal groups (6/each) until 24 weeks of age. Treatments were as follows: drinking fresh water and served as control (G1); drinking water supplemented with 100 mg/kg b. wt. of ginger aqueous extract (G2); drinking water supplemented with 50 mg/kg b. wt. of thyme aqueous extract (G3); drinking water supplemented with 100 mg/kg b. wt. of ginger aqueous extract plus 50 mg/kg b. wt. of thyme aqueous extract (G4). Administration of aqueous thyme extract with 50 mg/kg b. wt. improved (p < 0.001) feed intake and growth performance compared to control. The highest average daily gain (p < 0.001) was found for G3 rabbits followed by G4, G2 and G1 respectively. While the most efficient feed conversion ratio was found in G4. Group 3 and group 4 had significant (p < 0.05) positive effect on caecum pH, ammonia and TVFAs concentration. Data indicated that treated groups had hastened the age with heavier body weight, larger testicular size and higher testosterone level. Also, most semen characteristics (volume, progressive motility, sperm concentration and normal spermatozoa) were higher in treated groups compared with the control group. Furthermore, gathering of the spermatozoa in the lumen of the seminiferous tubules, expanded epithelial cells stature of the epididymis with stuffed lumens with sperms in treated groups. In conclusion, aqueous extracts of ginger and/or thyme can be used as a growth promoter for improving reproductive performance of V-line male rabbits.

Effect of dietary fiber levels on bacterial composition with age in the cecum of meat rabbits

This study investigated the influence of dietary fiber levels on the growth performance, digestion, metabolism, and cecal microbial community of rabbits with different diets at different age. The different levels of dietary natural detergent fiber (NDF) were formulated accordingly: 400(A), 350(B), 300(C), 250(D) g/kg original matter basis, respectively; the different ages were 52, 62, and 72 days. With NDF increasing, the average daily feed intake (ADFI) and feed conversion rate (FCR) were increased, whereas average daily gain (ADG) and mortality were decreased (p < 0.05). The stomach relative weight, stomach content relative weight, cecal relative weight, and cecal content weight increased with increasing NDF (p < 0.05). The NH3 -N concentration of cecum dropped when the dietary NDF increased (p < 0.05). The diversity of the total microbiota increased significantly in Diets B, C (p = 0.011), and reached the lowest in 52 days for all diet groups. The richness index was decreased significantly in Diet A, D (p < 0.05) and in 62 days (p < 0.001), respectively. The phylum Firmicutes was higher (p < 0.01) in rabbits fed Diets B, C than Diets A, D and Bacteroidetes was highest in Diets C, D, and Proteobacteria was the highest in Diet A (p < 0.001). Among the classified genera, there were 14 that had levels of abundance of more than 1% and were commonly shared by all samples. Ruminococcus spp. that produced volatile fatty acid (VFA) abundance was highest from Diets B, C at 52 and 62 days. It is interesting to note that Bifidobacterium from Diet C was the most abundant genus during the entire experimental period (p < 0.01). The data from Venn diagrams, principal component analysis (PCA), and heat map plots of the bacterial communities showed that there were more groups of shared microbiota with aging. The above results indicate the cecal microbiota controlled by the 350 g/kg NDF diet can prevent gastrointestinal distress and exhibit good production performance.

Prebiotic effects of alfalfa (Medicago sativa) fiber on cecal bacterial composition, short-chain fatty acids, and diarrhea incidence in weaning piglets

Dietary alfalfa fiber (AF) is conceived to modulate gut microbial richness and diversity to improve the health and growth of weaning piglets. The objective of this study was to evaluate the prebiotic effects of AF on diarrhea incidence, the production of short-chain fatty acids (SCFAs), and microbiota composition in weaning piglets. This study utilized 100 crossbred piglets (Duroc × Landrace × Yorkshire) with a body weight of 8.42 ± 1.88 kg randomly assigned to the following treatments: 0.00% AF meal (A), 6.00% of AF meal (B), 12.00% AF meal (C), and 18.00% AF meal (D). The cecum samples were used to determine microbial community composition and diversity through high-throughput 16S rDNA sequencing. The results of this study show that the lowest average daily gain (ADG) was observed in treatment D, and the highest ADG was recorded in treatment C. However there was no significant difference between the treatment groups and the control. The average daily feed intake (ADFI) was significantly higher in treatment C compared to the other treatments. The feed conversion ratio was high in the control group compared to the AF treated groups. The highest diarrhea incidence was observed in treatment A and the lowest diarrhea incidence was observed in treatment C and D. The highest acetate and propionate levels were observed in treatment B, but there was no significant difference between the treatment groups and the control. The supplementation of AF significantly increased the butyrate level in treatment D compared with treatments A and B but was not significantly different from treatment C. The Observed_species richness and Simpson diversity values of the cecum bacterial composition in the AF fed piglets were higher than the control. In addition, the Chao 1 richness and Shannon diversity increased with an increase in AF supplementation, reaching a plateau at treatment B and C, then decreasing at treatment D. The Bacteroidetes, Firmicutes, Tenericutes, Proteobacteria, Cyanobacteria, Spirochaetae, Actinobacteria, Fibrobacteres, Saccharibacteria, Synergistetes, Chlamydiae, Elusimicrobia, Deferribacteres, Fusobacteria, and others were relatively abundant in all treatments. The Bacteroidetes and Firmicutes were the dominant phyla, accounting for 98% of all reads. AF treatment decreased the Bacteroidetes phylum and increased the Firmicutes phylum compared with treatment A. Therefore, the dietary inclusion of AF may decrease diarrhea incidence, increase cecal bacterial composition and richness, and consequently improve the growth performance of weaning piglets.

Effect of tropical green forage Pueraria phaseoloides addition to a pelleted complete feed on rabbit growth performance and digestion

<p>The aim of this work was to study the effect of tropical green forage on rabbit growth performance and apparent digestibility. Thirty rabbits weaned at 35 d of age were individually caged and allotted to 2 dietary treatments. From 35 to 90 d of age, the control group C was fed <em>ad libitum</em> with commercial pelleted diet C only, while the test group was fed the C diet and forage <em>Pueraria phaseoloides</em> (Pp) <em>ad libitum</em>. Individual water and feed intake, body weight gain, nutrient apparent digestibility, red and white blood cells were studied. Mean housing temperature was 27.7°C. Water intake (35-90 d) did not differ between the 2 groups (mean=128 mL/d), whereas feed intake (35-90 d) was twice as high, with Pp (114 vs. 56 g; P=0.02). Forage intake doubled every 2 wk, averaging 50% of the total intake from 35 to 90 d of age. The growth rate was higher (+30%) in the Pp group after weaning (35-49 d) but did not differ between groups thereafter. The feed conversion was higher for the Pp group after weaning only (+ 87%; P&lt;0;05). Weight of rabbits and feed efficiency were not affected by forage addition. Organic matter digestibility of diet C alone was roughly twofold higher compared to C+Pp (P=0.03). Red blood cells were not affected by treatments (4.1×10¹² cells/L). However, the white blood cell count was higher in Pp than in C group (7.4×10⁹ vs. 3.9×10⁹ cells/L; P&lt;0.01). <em>P. phaseoloides</em> may be used as a complement to a balanced pelleted feed, but further studies with a large number of rabbits are necessary to analyse the potential impact on health status.</p>

Effect of varying the energy density on growth performance, meat quality, caecum fermentation and microbiota of growing Rex rabbits

An experiment was conducted to determine the effects of varying the digestible energy (DE) density on growth performance, meat quality, caecum fermentation and microbiota in 3–5-month-old Rex rabbits. One-hundred and eighty 3-month-old Rex rabbits were allocated in individual cages to five treatments with diets having DE levels (MJ/kg as-fed basis) of 9.46, 9.97, 10.46, 10.94 and 11.43, respectively. The results showed as follows: with increasing DE concentration the average daily gain, muscle pH value of 45 min post-mortem, caecal pH value and NH3-N concentration increased (P < 0.05). Bacterial denaturing gradient gel electrophoresis (denaturing gradient gel electrophoresis) of partial 16S rRNA genes profiles were clearly different among different treatments, which suggests that the population of microorganism in the caecum was influenced by the dietary DE density.

Growth performance and meat quality of rabbits under different feeding regimes

This study evaluated the growth, carcass characteristics and meat quality of indigenous rabbits in northern Pakistan. Weaned rabbits (age 35 days, weight 323 g) of four distinct phenotypes (white, black and white, brown and black) were fed four experimental diets: alfalfa hay (AH), berseem fodder (BF), BF supplemented with low-level concentrate (50 %; LLC) and high-level concentrate (75 %; HLC). Each experimental diet was fed to 48 rabbits, 12 of each phenotype, in a randomized complete block design. The duration of the experiment was 55 days, including 1 week of adaptation. Rabbits fed the BF and AH diets had poor body weight gain (P < 0.05) compared to rabbits fed the LLC and HLC diets. Feed conversion efficiency was best in the LLC (4.47) and HLC (4.58) groups. Average carcass yield (743 g) and carcass dressing percentage (56.2) were higher (P < 0.05) in LLC. Growth rate was not improved significantly by feeding HLC. Fat deposition in animals was higher (P < 0.05) in the groups supplemented with concentrate. Cost per kilogram of rabbit meat was lowest (P < 0.05) for BF, followed by AH, LLC and HLC. Brown phenotypes had the best (P < 0.05) feed conversion efficiency, body weight gain, carcass yield and carcass dressing. It was concluded that local rabbits do not necessarily need high levels of concentrates but can be well fattened with low-level concentrates along with forages.

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 diets on growth, digestibility, carcass and meat quality characteristics of four rabbit breeds

The current study was conducted to evaluate three diets using four rabbit breeds. A total of 320 male weaned rabbits representing four breeds named V-line, Saudi-1, Saudi-2 and Saudi-3 were randomly distributed into three comparable dietary treatments. Three levels of indigenous feedstuffs (IFS) of 42.5%, 65% or 87.5% (alfalfa hay, barley and wheat bran) were substituted for the same levels of non-indigenous feedstuffs in the diet (corn grain, soybean, molasses, and limestone) to form three diets named D1, D2 and D3, respectively. These dietary treatments were used to evaluate post-weaning growth performance, feed intake, feed conversion, carcass and lean composition, and nutrients digestibility in four rabbit breeds. Partial replacement of IFS with non-indigenous feedstuffs attained significant increase in growth performance. The diet containing 87.5% IFS led to significant increase in daily weight gains by 8.4, 4.0, 8.1, 6.2 and 6.7 g at age intervals of 5-6, 7-8, 9-10, 10-11 and 11-12 weeks compared to the control diet, respectively. The diet containing 87.5% IFS showed a significant reduction in feed conversion ratio compared to control diet during the experimental periods. The diet containing 65% IFS showed significant increases in pre-slaughter weight (112 g) and hot carcass weight (89 g), while dressing percent, offal weight and percent, and non-carcass weights and percentages (head, fur, legs + tail, viscera) were not significantly different. The diet containing 87.5% IFS gave an increase of 1.1%, 6.4%, 8.8%, 17.9%, 7.4%, and 19.6% in digestibility coefficients of organic matter (OM), crude protein (CP), neutral detergent fibre (NFD), acid detergent fiber (ADF), hemi-cellulose (HC) and cellulose (C) compared to control diet, respectively. Feed intakes were moderate and ranged from 69 to 124 g for V-line, 77 to 128 g for Saudi-1, 79 to 130 g for Saudi-2, and 76 to 119 g for Saudi-3 along with moderate ratios of feed conversion ranging from 2.65 to 3.80, 2.45 to 3.90, 2.46 to 3.79 and 2.63 to 3.65, respectively. Pre-slaughter weight, hot carcass weight, and offal weight were in favour of Saudi-2 rabbits compared to the other groups. Both Saudi-1 and Saudi-2 rabbits were slightly higher than Saudi-3 in weights and percentages of head, fur, viscera and legs + tail. Lean and bone weights and percentages and meat to bone ratio in Saudi-2 carcasses were slightly higher than those recorded in the other groups, while moisture, DM, CP, EE and ash contents in the lean have shown little differences between groups. Rabbits of Saudi-1 were ranked the first in digestibility coefficients of OM, CP, NDF, ADF, HC, C and cell count compared to other groups. Rabbits of Saudi-2 fed diet containing 87.5% IFS recorded the heaviest body weights and gains since this class showed considerable deviations in body weights of 345, 341, 269, 307, 321, 345 and 347 g at 6, 7, 8, 9, 10, 11 and 12 weeks of age, respectively, in comparison with the lightest class. Both Saudi-2 and Saudi-3 rabbits fed the diet containing 87.5% IFS had favourable estimates of feed conversions ranging from 2.1 to 3.4, while rabbits of Saudi-1 fed the diet containing 87.5% IFS recorded the best digestibility coefficients.

The effect of rabbit age on in vitro caecal fermentation of starch, pectin, xylan, cellulose, compound feed and its fibre

In vitro gas production kinetics of six different substrates, pectin (PEC), xylan (XYL), starch (STA), cellulose (CEL), commercial compound feed (FEED; 201 g crude protein per kg, 155 g crude fibre per kg, 334 g neutral-detergent fibre (NDF) per kg and 190 g acid-detergent fibre (ADF) per kg) and an NDF prepared from commercial compound feed (NDFFEED) were determined using the caecum contents of weaned rabbits (36 days of age) and of rabbits at slaughter age (78 days of age) as inoculums. The cumulated gas production over 96 h of incubation was modelled with Gompertz model, and the kinetic parameters compared. The total potential gas production (parameter 'B' of the Gompertz model) was not affected (P>0.05) by the inoculum source, except with STA, where rabbits at slaughter weight had significantly higher total potential fermentability (314 ml/g dry matter (DM)) than those at weaning age (189 ml/g DM). Intensities of fermentation (maximum fermentation rate; MFR) of PEC (32.2 ml/h) and XYL (24.4 ml/h) were significantly greater in rabbits at weaning, while that of STA (45 ml/h) was significantly lower than at slaughter age (23.0, 14.3 and 14.0 ml/h for PEC, XYL and STA, respectively). The MFRs of CEL and NDFFEED were very similar between inoculum sources. In the first 10 h of fermentation which correspond to the normal retention time of the substrates in the caecum, the highest amount of gas was produced from PEC, followed by FEED and XYL. These substrates had a time of maximum fermentation rate (TMFR) at both rabbit ages short enough (8.0 and 9.5 h for PEC, 9.5 and 6.6 h for FEED, 13.7 and 14.2 h for XYL at weaning and at slaughter age, respectively) to be almost completely fermented in vivo.

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.

Effect of different weaning ages (21, 28 or 35 days) on production, growth and certain parameters of the digestive tract in rabbits

The effect of different weaning ages, that is, 21 (G21), 28 (G28) or 35 (G35) days, on growth and certain parameters of the digestive tract was examined in rabbits to assess the risk of early weaning attributable to the less-developed digestive system. On days 35 and 42, G35 rabbits had 10% to 14% and 10% higher BW, respectively (P < 0.05), than those weaned at days 21 and 28. In the 4th week of life, early weaned animals had 75% higher feed intake than G28 and G35 rabbits (P < 0.05). The relative weight of the liver increased by 62% between 21 and 28 days of age, and thereafter it decreased by 76% between 35 and 42 days of age (P < 0.05), with G21 rabbits having 29% higher weight compared with G35 animals on day 35 (P < 0.05). The relative weight of the whole gastrointestinal (GI) tract increased by 49% and 22% after weaning in G21 and G28 rabbits, respectively (P < 0.05). On day 28, the relative weight of the GI tract was 19% higher in G21 than in G28 rabbits, whereas on day 35 G21 and G28 animals had a 12% heavier GI tract compared with G35 rabbits (P < 0.05). Age influenced the ratio of stomach, small intestine and caecum within the GI tract; however, no effect of different weaning age was demonstrated. The pH value of the stomach and caecum decreased from 5.7 to 1.6 and from 7.1 to 6.3, respectively, whereas that of the small intestine increased from 6.8 to 8.4 (P < 0.05); the differences between groups were not statistically significant. Strictly anaerobic culturable bacteria were present in the caecum in high amounts (108), already at 14 days of age; no significant difference attributable to weaning age was demonstrable. The concentration of total volatile fatty acids (tVFA) was higher in G21 than in G28 and G35 throughout the experimental period (P < 0.05). The proportion of acetic and butyric acid within tVFA increased, whereas that of propionic acid decreased, resulting in a C3 : C4 ratio decreasing with age. Early weaning (G21) resulted in higher butyric acid and lower propionic acid proportions on day 28 (P < 0.05). No interaction between age and treatment was found, except in relative weight of the GI tract and caecal content. In conclusion, early weaning did not cause considerable changes in the digestive physiological parameters measured, but it resulted in 10% lower growth in rabbits.

Effect of dietary inclusion of sorghum milling waste on growth response, nutrient utilisation, gut characteristics and cecal microflora of weaner rabbits

Growth response, nutrient digestibility and cecal microflora of 80 male, mixed breed weaner rabbits fed with varying dietary inclusions of sorghum milling waste (SMW) was investigated. Four experimental diets were formulated such that SMW was included at 0 (control), 100, 200 and 300 g/kg, respectively. Each dietary treatment was performed on 20 rabbits. Feed intake increased (P < 0.05) while final live weight and feed conversion ratio of rabbits decreased (P < 0.05) following increased dietary inclusion of SMW. Rabbits fed with 100 and 200 g/kg SMW had similar feed conversion ratios, weight gain, crude fiber, dry matter and crude protein digestibility values. Rabbits fed with 300 g/kg SMW recorded the lowest (P < 0.05) hot carcass weight, dressing percentage and rack weight. Similar dressing percentage and rack weight were recorded for rabbits fed with control diet, 100 and 200 g/kg SMW. The weight of cecal content increased (P < 0.05) with increased dietary inclusion levels of SMW. Rabbits fed with 300 g/kg SMW recorded the lowest (P < 0.05) coliform and lactobaccillus counts. Dietary inclusion of up to 200 g/kg SMW supported improved growth response and carcass yield without imposing any detrimental effect on cecal microflora.

Molecular analysis of the bacterial community in digestive tract of rabbit

This work aimed to study the stability over time of the bacterial community in caecum and faeces of the rabbit (diversity index and structure) without experimental disturbance and to evaluate its relationships with environmental parameters. Soft and hard faeces of 14 rabbits were sampled for 5 weeks while caecal content was sampled on the 3rd week (by surgery) and the 5th week (at slaughter). Bacterial communities were assessed by studying CE-SSCP profiles of 16S rRNA genes fragments. Redox potential, pH, NH3-N concentration and volatile fatty acid concentrations were measured in the caecum. Data showed that bacterial communities of soft and hard faeces barely differed from that of the caecum (ANOSIM-R<0.25; p<0.05). Without disturbance, the bacterial communities of faeces were stable over time (ANOSIM-R<0.25; p<0.001). However, the bacterial communities of caecum and faeces were affected by the surgery (ANOSIM-R=0.22-0.33; p<0.001). The caecal content was an acidic (pH=6.03+/-0.33) and an anaerobic environment (redox potential=-160+/-43 mV). Only the redox potential was correlated with the diversity index of the bacterial community of the caecum (R(2)=0.35; p<0.05) and no environmental parameters were correlated to its structure.

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.

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.

Effects of dietary neutral detergent fibre on production performance, nutrient utilization, caecum fermentation and fibrolytic activity in 2- to 3-month-old New Zealand rabbits

An experiment was conducted to determine the effects of different dietary neutral detergent fibre (NDF) levels on growth performance, nutrient utilization, caecum development, caecal fermentation, slaughter performance, immune organ and fibrolytic activity in 2- to 3-month-old New Zealand meat rabbits. Eighty 2-month-old rabbits were allocated in individual cages for five treatments in which they were fed each diet with NDF at 240, 270, 300, 330 and 360 g/kg respectively. The results are as follows: the average daily gain of 300 g/kg NDF group was the highest (30.09 g/day) and higher than that of 240 g/kg NDF group (p < 0.05). The feed/gain ratio of 300 g/kg NDF group was the lowest (4.27) and lower than those of 240 and 360 g/kg NDF groups (p < 0.05). The coefficient of total tract apparent digestibility (CTTAD) of energy, crude protein, crude fibre and ether extract decreased when dietary NDF increased (p < 0.05); CTTAD of NDF increased when dietary NDF increased (p < 0.01). Digestible nitrogen and retained nitrogen of 240, 270, 300 and 330 g/kg NDF groups were higher than that of 360 g/kg NDF group (p < 0.05). The caecum weight, the proportion of caecum weight to body weight and the acetic acid ratio of volatile fatty acid rose when dietary NDF concentration increased (p < 0.05). The NH(3)-N concentration of caecum dropped when dietary NDF increased (p < 0.05). The fibrolytic activity increased when the dietary NDF increased (p < 0.01).

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.

Inter-relationship of microbial activity, digestion and gut health in the rabbit: effect of substituting fibre by starch in diets having a high proportion of rapidly fermentable polysaccharides

Caecal microbial activity, digestion and gut health were analysed in the young rabbit, in response to fibre substitution by starch, in diets with high proportions of rapidly fermentable polysaccharides (pectins+hemicelluloses:acid-detergent fibre (ADF) ratio of 1.7). A range of five diets corresponding to a 60 % linear reduction of the ADF level (230 to 92 g ADF/kg) without changes in the fibre quality, and to a corresponding linear increase in dietary starch, was given ad libitum to young rabbits from 18 d until 70 d of age. A one half reduction of the ADF level resulted in a sharp increase in energy digestibility (+25 units), associated with a lower feed intake (-35 %) and to an increase of the mean retention time (+6 h) in the whole digestive tract. Despite large variations in the fibre intake (20 to 59 g ADF/d), the fibre digestive efficiency remained similar among the five diets. Starch ileal concentrations were low after 4 weeks of age (<5 %), and variations with age were significant when the dietary starch level was over 19 %. A 65 % lower biomass production was measured when the ADF level progressed from 230 to 165 g/kg, and no precise relationship was found with fermentative activity. Reducing the fibre intake led to a linear decrease of caecal volatile fatty acids concentrations, and to higher pH and NH3 levels. An increased occurrence of mortality by diarrhoea was registered with the lowest fibre intake. It can be concluded that a sufficient supply of fibre, with high proportions in rapidly fermentable polysaccharides, stimulates the maturation of microbial activity and reduces the occurrence of diarrhoea.