Effect of cellobiose supplementation and dietary soluble fibre content on in vitro caecal fermentation of carbohydrate-rich substrates in rabbits

The in vitro caecal fermentation of five substrates low in starch and protein content [d-(+)-glucose (GLU), d-cellobiose (CEL), sugar beet pectin (PEC), sugar beet pulp (SBP) and wheat straw (WS)] was investigated using soft faeces from rabbits receiving different levels of cellobiose and soluble fibre as inoculum. A total of 24 rabbits were supplemented 3 levels of cellobiose in the drinking water (0.0, 7.5, 15.0 g/l) and fed two experimental diets containing either low soluble fibre (LSF) or high soluble fibre (HSF) levels (84.0 and 130 g/kg dry matter). All substrates were subjected to a two-step pepsin/pancreatin in vitro pre-digestion, and the whole residue was used as substrate for the in vitro incubations. Gas production was measured until 144 h, and volatile fatty acid (VFA) production was determined at 24 h incubation. Experimental treatments did not affect SBP fermentation and had only a subtle influence on fermentation of WS and GLU. In contrast, cellobiose supplementation × donors’ diet interactions were detected for most gas production parameters for CEL. Both the fractional gas production (k) and maximal gas production rates were linearly increased (p ≤ 0.042) and the initial delay in the onset of gas production (Lag) linearly decreased (p < 0.001) by cellobiose supplementation with the HSF inoculum, with no differences between the 7.5 and 15.0 doses. In contrast, with the LSF inoculum cellobiose supplementation only affected k values, which were quadratically increased (p = 0.043) and had maximal values for the 7.5 dose. A quadratic effect (p ≤ 0.018) of cellobiose supplementation was observed for total VFA production at 24 h when CEL and PEC were fermented, obtaining the maximal VFA production for the 7.5 dose of cellobiose. Total VFA production for CEL was greater with LSF than with HSF inoculum (20.7 vs. 12.9 mmol/l; p = 0.014), but the opposite was found for WS (3.97 vs. 6.21 mmol/l; p = 0.005). The use of LSF inoculum for CEL fermentation sharply reduced acetate (p = 0.001) and increased butyrate proportions (p ≤ 0.001) compared with the HSF inoculum. A positive relationship between total VFA caecal concentrations in rabbits receiving the same experimental treatments and in vitro values was only observed when WS was used as substrate (r = 0.90; p = 0.015; n = 6). The results suggest that experimental factors influenced the fermentative activity of caecal digesta, but the observed response differed with the incubated substrate, being the CEL the most affected.     

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.     

Effects of fibre level and dietary mannanoligosaccharides on digestibility,caecal volatile fatty acids and performances of growing rabbits

The current experiment with 3 trials aimed to study the effect of two levels of dietary fibre – high fibre (HF; 323 g aNDFom/kg) and low fibre (LF; 248 g aNDFom/kg) – and the effect of mannanoligosaccharides (MOS) addition (1 g/kg) to the LF diet (LFM) on the performances and health status of growing rabbits, digestibility and caecal fermentative characteristics. In the growth trial 132 rabbits of both sexes were used (11 cages with 4 rabbits per treatment) from weaning (32 days of age) to slaughter (67 days of age). Rabbits fed HF diet showed a significantly higher weight gain and live weight at 67 days than rabbits fed LF diet (2032 g vs. 1935 g) (P<0.05). Feed and digestible energy intake increased with dietary fibre level (P<0.05). During the growing period rabbits fed HF diet had a feed intake 26% higher than those fed LF diet. Feed efficiency ratio was worse in HF animals (0.334 vs. 0.385; P<0.05). Addition of MOS to LF diet did not affect growth performance parameters (P>0.05). Mortality and morbidity rate were not affected by treatments. In the digestibility 24 rabbits from 46 to 51 days of age trial were used. The HF diet resulted in a significant (P<0.05) decrease in digestibility of dry matter, organic matter and protein while the aNDFom digestibility was not significantly different between diets (P>0.05). Supplementation with MOS had no effects on digestibility (P>0.05). In the 3rd trial the caecal traits were measured in 30 rabbits with 46 days of age that received the experimental diets in the previous 14 days. Caecal production of total volatile fatty acids (VFA), acetate and propionate were significantly higher (P>0.05) on rabbits fed HF diets than on rabbits fed LF diets. The total VFA concentration increased 64% (from 5.01 to 8.20 mmol/100 ml) and acetate increased 73% (from 3.73 to 6.44 mmol/100 ml). Butyrate production was not different between diets (P>0.05). Fibre level did not affect proportions of VFA and caecal contents and caecal weights. Addition of MOS to LF diet did not affect any caecal trait (P>0.05). It was concluded that the reduction of dietary fibre level increases feed digestibility but worsens rabbit growth performances. Supplementation of low fibre diet with 1 g MOS/kg is not enough to reduce its negative effects on growth performances.     

Biodiversity and fermentative activity of caecal microbial communities in wild and farm rabbits from Spain

In order to study the microbial caecal ecosystem of wild and domestic rabbits through the fermentation characteristics and concentration and diversity of bacterial and archaeal communities, caecal samples from sixteen wild rabbits (WR) were contrasted with two groups (n = 4) of farm rabbits receiving low (LSF) or high (HSF) soluble fibre diets from 28 (weaning) to 51 days of age. DNA was extracted for quantifying bacteria and Archaea by qPCR and for biodiversity analysis of microbial communities by DGGE. Samples from WR had lower caecal pH and ammonia and higher volatile fatty acids concentration than farm animals. Lower acetate and higher butyrate proportions were detected in WR. Bacterial and archaeal DGGE profiles were clearly different between wild and farm rabbits, and diet-affected population of farm rabbits. Similarity index of bacteria was lower than 0.40 among WR, and 0.52 among farm rabbits. In conclusion, caecal fermentation characteristics differ between wild and farm rabbits, which harbour clearly different bacterial and archaeal communities. In farm rabbits, diversity is influenced by the dietary level of soluble fibre.     

Effects of age and mannanoligosaccharides supplementation on production of volatile fatty acids in the caecum of rabbits

This trial studied the effect of including mannanoligosaccharides (MOS, Bio-Mos^®, Alltech Inc., USA) in the diet on the caecal volatile fatty acids (VFA) and pH of rabbits from 34 to 90 days of age. Three experimental diets were compared: control diet, zinc bacitracin (ZnBac) diet (control diet with 0.1 g ZnBac/kg feed) and MOS diet (control diet with 2.0 g MOS/kg feed). Rabbits were slaughtered at 34, 48, 69 and 90 days of age and caecal contents were collected and analyzed for dry matter, pH and VFA concentration. The empty caecum and caecal contents weights relative to live weight were also determined.Age affected (P<0.0001) VFA concentration and pH values in the caecum. The pH decreased with age whereas VFA concentration increased. Rabbits fed MOS had higher (P<0.05) VFA and tended (P=0.098) to had lower pH in the caecum than rabbits fed ZnBac and control diets. Acetic, propionic and butyric acids concentrations in the caecum increased with MOS but its molar proportions were similar among diets. Diet had no effect on empty caecum weight and caecal contents weight and dry matter concentration. There was no interaction effect between diet and age. From 34 to 90 days of age, VFA production was higher (P<0.05) in the caecum of rabbits fed MOS than in those fed ZnBac diet and control diet.The addition of MOS to the diet increased the VFA concentration in the caecum of growing rabbits from 34 to 90 days of age.     

Comparative in vitro study of caecal microbial activity in brown hares and domestic rabbits which were offered the same diet

The products of the microbial activity in the large intestine are an important source of energy for herbivores. A previous study showed differences in caecal methanogenesis and short-chain fatty acid (SCFA) profiles between brown hares and domestic rabbits. The present study was performed on animals which were offered the same diet to eliminate the impact of diet on the comparative analyses of microbial metabolites. Caecal samples of hares and rabbits were incubated in triplicate, i.e. without any supplementary substrate (control) or with the addition of wheat bran or oat bran. Calculated as percentage of body weight, the stomachs of the rabbits were heavier than those of the hares, but caeca of the hares weighed more than those of the rabbits. The total SCFA concentration in caecal samples was higher in rabbits than in hares, and it increased in both species when the supplementary fermentation substrates were added. In hares, the molar proportion of propionate was higher and that of butyrate was lower compared to rabbits. The addition of substrate decreased acetate and propionate but increased the molar proportion of butyrate. Microbial fermentation resulted in greater gas release in rabbit caecal samples compared to those of hares. Methanogenesis tended to be lower in hares than in rabbits, but high individual variability was observed, especially in hares. Our study stated lower microbial activity in the caeca of brown hares compared to domestic rabbits. The presented results might lead to assumption that differences between fermentation patterns were not caused by diet but resulted from the peculiarities of both species.     

高功率微波急性辐照对家兔视网膜睫状神经营养因子表达的影响

目的:探讨高功率微波(HPM)急性辐照后家兔视网膜组织睫状神经营养因子(CNTF)表达量在不同时间的变化规律。方法:采用RT-PCR的方法检测90 W/cm2×15 min辐照后0,3,6,12,24和72 h不同时相点家兔视网膜组织CNTF mRNA表达的情况。结果:微波辐照后即刻,家兔视网膜CNTF mRNA表达含量极显著升高(P<0.01),并达最高峰值;3 h后家兔视网膜CNTF mRNA表达含量开始下降;微波辐照后6 h、12 h家兔视网膜CNTF mRNA含量继续下降,但均仍显著高于对照组水平(P<0.05);24 h、72 h时的家兔视网膜CNTF mRNA表达含量与对照组的CNTF mRNA含量相比基本持平。结论:HPM急性辐照能即刻显著性的增强家兔视网膜CNTF mRNA的表达,其表达量与损伤时间之间存在时效关系。HPM辐照引起的CNTF mRNA表达上调可能参与了微波辐照所致的家兔视网膜组织损伤,为利用外源型CNTF治疗微波辐照所致的家兔视网膜组织损伤提供理论依据。     

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.     

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

The presence of the fermentable sugar d-mannitol in the diet improves nitrogen (N) utilization in rabbits. To clarify the mechanism by which d-mannitol improves N utilization, we studied the effect of d-mannitol on the fate of blood urea N in growing rabbits. Growing rabbits received a control diet or a diet containing d-mannitol, which were formulated by adding 80 g/kg glucose or d-mannitol to timothy hay. After 9 days of feeding of the experimental diets, ¹⁵N-urea was administrated intravenously under anesthesia 1 h before slaughter. The blood urea level (concentration of both urea N (43.6% of the control group (CG), P < 0.05) and ¹⁵N (95% of the CG, P < 0.05) in blood serum) was reduced in the mannitol group. The concentration and amount of N, and ¹⁵N atom % excess in the contents of the cecum and colon were higher (P < 0.05) in the rabbits fed the mannitol diet than in rabbits fed the control diet, especially in the cecum. The consumption of mannitol caused bacterial proliferation in the cecum characterized by marked short-chain fatty acid production (165% of the CG, P < 0.05), decreased cecal ammonia N (73% of the CG, P < 0.05) and elevated cecal bacterial N (150% of the CG, P < 0.05). On the other hand, addition of d-mannitol to the diet decreased N (80% of the CG, P < 0.05) and ¹⁵N (77% of the CG, P < 0.05) excretion in the urine. These results indicate that d-mannitol increases the transfer of blood urea N to the large intestine, where it is used for bacterial N synthesis.     

Stress-induced inhibition of the ileal, caecal, and colonic contractile activity in rabbits]

In alert rabbits, immobilisation stress decreased the spike burst rate and amplitude in ileum, caecum, and colon for 20 min. Following beta-adrenoceptor blockade, the contractile activity suppression was aggravated. The stress seems to lead to suppression of the ileal, caecal, and colonic contractile activity for up to 40 min which is unrelated to adrenergic inhibition of the smooth muscle activity mediated by beta-adrenoceptors.     

Effect of Kepone on estuarine microbial activity

In situ heterotrophic uptake of mixed¹⁴C-amino acids and direct viable cell (DVC) count of Chesapeake Bay water samples were not significantly affected by the insecticide Kepone at concentrations 0.01 mg/1. Maximum inhibition of heterotrophic uptake,ca. 85–90%, and DVC count, 45–97%, was evident at concentrations of Kepone exceeding 0.2 mg/1. A specific activity index (Metabolic Activity/DVC or Kepone-resistant DVC), heterotrophic uptake, and DVC count were found to be statistically correlated (a=0.05) to one another, but negatively correlated with concentration of Kepone. The direct viable cell count proved to be a rapid, simple method for estimating the effect of Kepone on in situ estuarine microbial activity.     

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 (NDF_FEED) 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 NDF_FEED 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.     

The effect of medicated diets and level of feeding on caecal microbiota of lactating rabbit does

AIMS: To study the effect of the type of antibiotic used in medicated diets against pathogens and the feeding level on the microbial biodiversity in the rabbit caecum. METHODS AND RESULTS: Three groups of eight does were given a diet unsupplemented (NAB) or with 100 ppm of bacitracin (BAC) or tiamulin (TIA). Litter sizes of four does in each group were adjusted to five (LS5) or to nine (LS9), to manipulate their levels of feed intake. The feeding level strongly affected caecal microbiota in does fed on NAB and BAC diet, whereas the effect of the antibiotic was higher in TIA-supplemented animals, even prevailing over the effect of feeding level. Daily food intake and milk yield (P<0.05) and caecum weight (P<0.10) were higher in feeding of LS9 does. The total volatile fatty acid concentration was lower with BAC (P<0.05). CONCLUSIONS: The feeding level strongly affects caecal biodiversity in lactating does. The extent of the antibiotic effect depends on its nature, being significant with TIA but not with BAC. SIGNIFICANCE AND IMPACT OF THE STUDY: Changes in the feeding level promote different profiles of caecal microbiota. Therapeutic doses of TIA may affect caecal microbiota, whereas BAC would not reduce diversity.     

Effect of garlic supplementation to cholesterol-rich diet on development of atherosclerosis in rabbits

Feeding of cholesterol-rich diet in male rabbits resulted in increased levels of cholesterol in plasma, aorta and liver and total lipids, phospholipids, free fatty acids in aorta and liver. Garlic supplementation to this diet suppressed these effects but their levels were still higher as compared to control rabbits. The plasma fibrinolytic activity which was decreased on cholesterol feeding was considerably increased when this diet was supplemented with garlic. There was increase in the activity of phospholipase in the cell-free supernatant of aorta and liver and decrease in the activity of cell-free supernatant NADH dehydrogenase of aorta when atherogenic diet was supplemented with garlic. Histopathological studies of aorta, liver and heart supported biochemical studies and indicated retardative effect of garlic on the development of atherosclerosis.     

Effect of microbial phytase supplementation on P digestibility in pigs: a meta-analysis

ABSTRACT

The objectives of this meta-analysis were to determine to which extent phosphorus (P) digestibility and digestible P concentration in pig diets were increased by phytase supplementation and to quantify factors that potentially influence effects of phytase supplementation. A data set with a total of 547 data lines was compiled from 88 experiments published in 74 peer-reviewed papers between 2007 and April 2019. An exponential model was determined as more suitable to describe the response of P digestibility to phytase supplementation than a polynomial model. Phytase supplementation increased P digestibility by 25.6 percentage points (standard error (SE) = 1.54) to a plateau at 64.9% (SE = 1.82). The digestible P concentration was increased by phytase supplementation in the order of 1.01 g/kg (SE = 0.102) to a plateau at 2.62 g/kg (SE = 0.122). Goodness-of-fit criteria were R² = 0.780 and root mean square error = 7.55% for P digestibility, and R² = 0.691 and root mean square error = 0.48 g/kg for digestible P concentration. Consideration of further factors such as mineral P supplementation (yes or no), ad libitum vs. restrictive feeding, mixed diets vs. single feed ingredients, sex and age of pigs did not increase the accuracy of prediction in this data set. Some of these traits exhibited responses, but they likely are artefacts generated through the imbalanced structure of the data set. Effects of dietary total P, phytate (InsP₆), InsP₆-P to total P ratio, and Ca on the effect of supplemented phytase were not quantifiable. The present meta-analysis showed that responses to phytase supplementation can be well predicted although variation in P digestibility and digestible P concentration in the data set was high. Overall, predicted effects of phytase on P digestibility well corresponded to predictions made 25 years ago.     

Efficacy of Antibiotics A204 Sodium, A28695A, and A204np against Coccidia of Rabbits

SYNOPSIS. Three polycyclic, polyether, monocarboxylic acid antibiotics produced by and extracted from a strain of Streptomyces albus and designated A204 sodium, A28695A, or A204np, were specifically tested for activity against hepatic and incidentally against intestinal coccidia of rabbits. All were effective in preventing infections and acceptable to young rabbits when prepared in pelleted feed. Weight gain, however, was not as good in inoculated, medicated rabbits as in noninoculated, nonmedicated controls.
No gross pathologic changes were detected except in the livers of inoculated, nonmedicated controls which were severely infected and greatly enlarged. Livers of medicated rabbits were uninfected and normal in appearance and size.