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

Effect of Using Prickly Pear Seed Cake (Opuntia ficus indica L.) on Growth Performance, Digestibility, Physiological and Histometric Parameters in Rabbits

Prickly pear (Opuntia ficus indica L.) could be used in rabbit nutrition in compliance with circular economy principles, global warming issues, and reduction of production costs. This study aims to evaluate the effects of dietary incorporation of prickly pear seed cake (PPSC) on growth, physiological, and histometric parameters in rabbits. A total of 105 rabbits were divided into three experimental groups (n = 35) and fed different diets: a commercial feed (C group), the same feed with alfalfa replaced by PPSC at 10% (10PP group), and at 20% (20PP group). They were group-housed in cages with 5 animals per cage from weaning until slaughtering. While body weights and weight gains were similar in all groups, the coefficients of nutrient digestibility of dry matter, fibers, and ashes, as well as the characteristics of intestinal villi, were improved in the 10PP group compared to the others (p < 0.05). The 20PP group showed a reduction in perirenal and interscapular fat (p < 0.05), as well as lower plasma concentrations of triglycerides and cholesterol compared to the C group (p < 0.001). In conclusion, PPSC can be incorporated into the diets of growing rabbits up to 20% as a partial substitute for alfalfa without the impairment of growth performance. Additionally, the inclusion of PPSC enhanced nutrient digestibility and increased the intestinal absorption surface area.

Effect of Adding the Antimicrobial L-Carnitine to Growing Rabbits' Drinking Water on Growth Efficiency, Hematological, Biochemical, and Carcass Aspects

The current study was designed to assess the impact of L-carnitine (LC) supplementation in the drinking water of growing Alexandria-line rabbits on performance and physiological parameters. Two hundred eighty-eight 35-day-old rabbits were divided into four groups of twenty-four replicates each (seventy-two rabbits/treatment). The treatment groups were a control group without LC and three groups receiving 0.5, 1, and 1.5 g/L LC in the drinking water intermittently. The results showed that the group receiving 0.5 g LC/L exhibited significant improvements in final body weight, body weight gain, feed conversion ratio, and performance index compared to the other groups. The feed intake remained unaffected except for the 1.5 g LC/L group, which had significantly decreased intake. Hematological parameters improved in all supplemented groups. Compared with those in the control group, the 0.5 g LC/L group showed significant increases in serum total protein and high-density lipoprotein, along with decreased cholesterol and low-density lipoprotein. Compared to other supplemented groups, this group also demonstrated superior carcass traits (carcass, dressing, giblets, and percentage of nonedible parts). In conclusion, intermittent supplementation of LC in the drinking water, particularly at 0.5 g/L twice a week, positively influenced the productivity, hematology, serum lipid profile, and carcass traits of Alexandria-line growing rabbits at 84 days of age.

Valorisation of grape stem as an alternative ingredient in rabbit feed

Grape stem is a winery by-product that it is currently disposed as waste or at best as soil conditioner. However, it is rich in fibres and polyphenols which makes it interesting for animal feeding. In this regard, rabbit farming emerges as a target livestock farming since fibre content is essential in rabbit's diets for preventing digestive troubles and polyphenols are associated with improved performances in animals due to their antimicrobial and antioxidant activities. This study aims to assess the suitability of a grape stem-based ingredient for rabbit feeding. The stem was dried using flash drying technology to prevent rapid spoilage and stabilise the ingredient. Then, its nutritional value was evaluated resulting in a high fibre (>40%) and polyphenol (>6%) content ingredient with antioxidant and antimicrobial activity against Staphylococcus aureus. A feed efficiency trial was conducted and inclusion rates of up to 10% of grape stem-based ingredient did not affect animals' mortality, average daily feed intake, daily gain or feed conversion ratio. In conclusion, grape stem-based ingredient arises as a secondary feedstuff for cuniculture reducing the dependence on other fibre sources, such as cereals or sunflower hulls. This could also contribute to reduce the environmental footprint of the wine sector by giving a second life to an existing waste, while generating a new activity based on circular economy.

Social, ethical, environmental, economic and technological aspects of rabbit meat production - A critical review

Rabbit (RM) has become a valuable source of nutrients since the 1970s, helping to transform the European food industry into the largest RM producer in the world. However, the RM industry is experiencing a critical period of ethical imbalance. This trend, described as feed conversion ratio, impacts the environmental and financial performance of RM farms, which could lead to an increase production of industrial waste. In addition, the loss of corporate ethical responsibility and sustainable development by RM-oriented companies has further exacerbated the situation. Our objective was to summarize current trends in the RM industry and markets, highlighting possible strengths and weaknesses. This review shows current approaches in sustainable techniques in RM production processes, ethical issue, environmental and processing responsibility of RM producers, as well as social responsibilities and ethical practices of slaughterhouses and RM producers, sustainable environmental practices of slaughterhouses, technological aspects and safety of RM and social drivers in RM market. The analysis of reviewed literature revealed the potential strategies for sustainable RM production.

Digestive problems in rabbit production: moving in the wrong direction?

Digestive problems, both those with a clear pathogenic origin (e.g., Escherichia coli) and those without obvious pathogen involvement [e.g., syndromes like epizootic rabbit enteropathy (ERE)], are common in production rabbits and account for the majority of losses in meat rabbit production. A multitude of nutritional, genetic and housing factors have been found to play a role in the occurrence of digestive problems. However, the exact early pathophysiological mechanism, including the links between aforementioned risk factors and subsequent development and expression of gastrointestinal disease, is less clear, especially in non-specific enteropathies without obvious pathogen involvement. In this review, we aim to shed more light on the derailment of the normal gastrointestinal functioning in rabbits. We discuss a conceptual integrated view of this derailment, based on an "overload" pathway and a "chymus jam" pathway, which may occur simultaneously and interact. The "overload" pathway centers around exposure to excess amounts of easily fermentable substrate (e.g., starch and protein) that might be incompletely digested prior to entering the caecum. Once there, hyperfermentation may result in changes in caecal pH and inhibition of the normal microflora. The second pathway centers around a chymus jam resulting from a compromised passage rate. Here, reduced hindgut motility (e.g., resulting from stress or limited fiber supply) leads to reduced flow of digesta and increased caecal retention times, which might lead to the production of abnormal caecal fermentation products and subsequent inhibition of the normal microflora. A central role in the presumed mechanism is attributed to the fusus coli. We discuss the suggested mechanisms behind both pathways, as well as the empirical substantiation and alignment between theoretical concepts and observations in practice. The proposed hypotheses may explain the effect of time-based restriction to prevent ERE, which is widely applied in practice but to date not really understood, and suggest that the particle size of fiber may be a key point in the normal functioning of the colon and fusus coli. Further insight into the circumstances leading to the derailment of physiological processes in the rabbit hindgut could provide a meaningful starting point to help improve their gastrointestinal resilience.

Growth performance, digestive function, thyroid activity, and immunity of growing rabbits fed olive cake with or without Saccharomyces cerevisiae or citric acid

The present study investigated the impact of dietary inclusion of olive cakes (OC) with or without Saccharomyces cerevisiae (SC) and citric acid (CA) on growth, digestive function, thyroid activity, antioxidant status, immunity, and intestinal architecture of growing rabbits. One hundred forty 35-day-old male New Zealand white rabbits were randomly assigned into seven experimental groups with five replicates each, as follows: control (CN), fed the basal diet; OC20 and OC25, fed diets with 20 and 25% OC; OS20 and OS25, fed diets containing 20 and 25% OC with S. cerevisiae at 5 g/kg diet; OA20 and OA25, fed diets supplemented with 20 and 25% OC with 1.0% citric acid. No differences in live body weight, feed intake, feed conversion ratio, and carcass traits were noticed among experimental groups, while body weight gain and carcass (%) were increased (P < 0.05) in OS20 compared to the control. Digestibility coefficients of all nutrients and activities of amylase, cellulose, and trypsin did not differ in treated groups compared to the control except for OS20, which recorded enhancement in nutrient digestibility. Plasma triiodothyronine and thyroxine were elevated (P < 0.05), while triglycerides and cholesterol were reduced (P < 0.05) in OS20 compared to CN. Plasma concentrations of immunoglobulin M and G and superoxide dismutase were increased in treated groups compared to the control. Dietary inclusion of SC and CA improved rabbits' intestinal health, as the cecal Lactobacillus count was increased, E. coli count was decreased, and villus height was elevated in SC- and CA-treated groups. In conclusion, dietary incorporation of SC or CA enhanced the nutritional value of OC and improved growth performance, nutrient digestibility, thyroid activity, antioxidative status, and gut health of growing rabbits.

Impact of different dietary fibre sources on production performance, bacterial composition and metabolites in the caecal contents of rabbits

This study was conducted to investigate the effects of different dietary fibre sources on growth performance, gastrointestinal tract development, caecal fermentation and bacterial composition in the caecal contents of rabbits. A total of 120 35-day-old weaned Minxinan black rabbits were divided into three groups and fed a diet composed of peanut straw powder (Group A), alfalfa powder (Group B) and soybean straw powder (Group C) as the main fibre source. The final body weight and average daily gain in Group B were higher than those in Group C, and the average daily feed intake and feed conversion ratio in Group A were lower than those in Group C (p < 0.05). The relative weights of the stomach, small intestine and caecum of rabbits in Group C were higher than those in Groups of B and A, and the relative weights of the caecal contents in Group C were lower than those in Groups A or B (p < 0.05). The pH value and propionic acid, butyric acid and valeric acid concentrations in the caecum of Group C were lower than those in the caecum of Groups A or B, and the concentration of acetic acid in the caecum was lower (p < 0.05). The dominant microbes in the caecal contents of Minxinan black rabbits were Firmicutes, Bacteroidetes and Proteobacteria at the phylum level, and the number of species, Chao1 index and ACE index measured was different between the B-C and A-C groups (p < 0.05). Different dietary fibre sources could affect the growth performance, gastrointestinal tract development and intestinal microbiota of rabbits, and the nutritional value of alfalfa powder was better than that of peanut straw and soybean straw.

Use of Moringa oleifera leaves (sole or combined with concentrate) in rabbit feeding: Effects on performance, carcass characteristics and meat quality attributes

Sixty Chinchilla rabbits (28 days old) were divided into three equal groups (n = 20). Rabbits in MOL0 (control) were fed pellets containing 700 g cowpea hay/kg pellet as forage source, whereas rabbits in MOL700 and MOL950 were fed pellets containing 700 and 950 g moringa leaves/kg feed pellets, respectively. Average daily gain and feed conversion ratio was comparable in MOL700 and MOL0, however, it was higher in MOL950. Among the carcass traits, dressing percent was higher while, chilling loss was lower in MOL700 treatment. The Longissimus thoracis muscle of rabbits fed moringa leaves containing pellets (MOL700 and MOL950) had lower saturated fatty acid content, higher C18:3n-3 and total n-3 fatty acids along with lower thrombogenic index value. Hence, incorporating moringa leaves at 70% level is beneficial in terms of improved growth performance and functional attributes of meat than diet- containing sole moringa leaves.

Inclusion of Soybean Hulls (Glycine max) and Pupunha Peach Palm (Bactris gasipaes) Nanofibers in the Diet of Growing Rabbits: Effects on Zootechnical Performance and Intestinal Health

This study evaluated the inclusion of nanofibers from soybean hulls and pupunha peach palm heart sheaths in the diet of growing rabbits. Twenty-four New Zealand White rabbits (male and female) were allocated in three experimental groups: control, fed a basal diet; Nanosoy, fed a diet containing 7% soybean-hull nanofibers; and Nanopupunha, fed a diet containing 7% pupunha palm heart-sheath nanofibers. The Nanosoy-group rabbits showed poorer final weight, daily feed intake, and daily weight gain than those in other groups. In the duodenum, villus height, total mucosal thickness, and villus width were higher in rabbits that received nanofiber-supplemented diets than in the controls. Higher villus density and wall thickness were observed in Nanopupunha-fed rabbits than in the controls. In the jejunum, although the crypt depth was higher in Nanosoy-fed rabbits, the villus height:crypt depth ratio was higher in the Nanopupunha-fed group. Nanosoy-fed animals exhibited increased count Enterobacteriaceae populations. Rabbits in both nanofiber-fed groups exhibited higher lactic-acid bacterial counts than those in the control-diet group. Therefore, although the inclusion of 7% Nanopupunha in the diet of rabbits did not alter the performance, it improved intestinal health and increased the lactic-acid bacterial count in the cecum of growing rabbits.

The ratios of dietary non-fibrous carbohydrate (NFC) to neutral detergent fiber (NDF) influence intestinal immunity of rabbits by regulating gut microbiota composition and metabolites

Carbohydrate is the most common macronutrient consumed across all phases of the diet and acts as a potential regulator in modulating the gut microbiota in animals. However, the influences of dietary non-fibrous carbohydrate (NFC) to neutral detergent fiber (NDF) in different ratios on gut microbiota, metabolites, intestinal immunity, and growth performance have not been fully explored. A total of 135 healthy weaned rabbits (45.1 ± 0.7 d of age) with an average body weight of 1.08 ± 0.07 kg were randomly divided into five groups. Under the same other nutrient levels, rabbits were fed diets with NFC/NDF ratios of 0.7 (T1), 1.0 (T2), 1.3 (T3), 1.6 (T4), and 1.9 (T5). During the 28-day experiment, T3 rabbits showed the highest final body weight and the lowest feed-to-weight ratio than T5 rabbits (P < 0.05) but no significant difference with T1 or T2 rabbits. The expression of cecal pro-inflammatory factors IL-1β and TNF-α was increased in the T4 and T5 than in those of other groups (P < 0.05). Conversely, the tight junction proteins (ZO-1, Claudin-1, and Occludin) were decreased to varying degrees in the T4 and T5 groups. The pH value in the cecal digesta of T5 rabbits was lower than that of T1, T2, and T3 (P < 0.05), while the concentration of volatile fatty acids and propionate was higher than those of T1, T2, and T3 rabbits (P < 0.05). In terms of gut microbiota, at the phylum level, the relative burden of Firmicutes and Actinobacteria in T2 rabbits was the highest (P < 0.05), and the relative burden of Proteobacteria in T5 rabbits was higher than that of other groups (P < 0.05). At the genus level, the relative burden of Ruminococcus was higher in T2 and T3 rabbits than that of other groups, and T5 rabbits have the lowest relative burden of Ruminococcus. Combination analysis showed that cecal metabolites were positively associated with fermentation-related phenotypes and the burden of Firmicutes (P < 0.05). In conclusion, different dietary NFC/NDF ratios can affect the intestinal immune response and growth performance of rabbits, and there was a positive effect when dietary NFC/NDF = 1.0-1.3.

Dietary inclusion of fermented ginger straw effect on the growth performance, gastrointestinal tract development and caecal fermentation of fattening rabbits

This experiment was conducted to evaluate the effects of dietary inclusion of fermented ginger straw on the growth performance, gastrointestinal tract development and caecal fermentation of fattening rabbits. A total of 160 45-d-old Laiwu black rabbits were randomly divided into 4 groups and fed 0% (Control), 5, 10 or 15% fermented ginger straw in their diet as a replacement for peanut straw powder. The trial lasted for 7 d of adaptation and 43 d for testing. Growth performance was recorded from 52 to 95 d of age (n=5 per treatment with 30 rabbits, 3 males and 3 females per replicate), TTAD of nutrients from 91 to 95 d of age, and gastrointestinal tract development, caecum fermentation and carcass traits were determined at 95 d of age (n=5 per treatment with 10 rabbits, 1 males and 1 females in per replicate).The results showed that the average daily gain and final body weight in the experimental groups (5, 10 and 15% fermented ginger straw) were higher than in the control group (P<0.05). However, the average daily feed intake in the 15% group was higher than in the other groups, while the total tract apparent digestibility of crude protein, ether extract, neutral detergent fibre and acid detergent fibre were lower than in the control group (P<0.05), and the relative weights of the stomach, small intestine and caecum content in the 15% substitution group were higher than those in the control group (P<0.05). In addition, the thickness of the muscle layer in the 15% substitution group was higher than that in the other groups (P<0.05). Moreover, pH and total volatile fatty acids concentration in the caecal content were similar among the 4 groups (P>0.05). The current work shows that fermented ginger straw could be used as roughage material in fattening rabbit production up to a dietary dose of 10%.

Effect of a Diet Based on Biotransformed Sorghum on Rabbit Intestinal Morphology and Fecal Fiber Composition

Some of the goals of meat production systems are to improve feed efficiency, reduce costs, provide proper nutrition and avoid metabolic disorders. Hence, the aim of this work was to compare a rabbit diet based on untreated sorghum (T1) with a second one that included the cereal biotransformed by the co-cultivation of two basidiomycetes (T2). Their effects on the cereal, diets, and fecal structural fiber composition, as well as on rabbit intestinal morphology, were evaluated. A completely randomized design was applied, employing 24 New Zealand rabbits (21 days old). The fiber chemical composition results indicated that the sorghum treated with the co-culture had lower amounts of neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, hemicellulose and cellulose, as did rabbits fed the T2 diet. Decreases in the NDF, ADF and cellulose contents were detected in T2-nourished rabbit excrements at day 21 (p ≤ 0.05), while lignin percentages diminished at days 35 and 49 (p ≤ 0.05). These rabbits also showed longer jejunal and cecal villi (p ≤ 0.05). The results obtained suggest a positive effect on the bioavailability of structural fibers after sorghum fungal co-fermentation, as their content decreased in rabbit fecal matter without damaging the intestinal morphology.

Growth Performance, Digestive Efficiency, and Meat Quality of Two Commercial Crossbred Rabbits Fed Diets Differing in Energy and Protein Levels

The present study evaluated the effect of digestible energy (DE) and crude protein (CP) levels on growth, digestive efficiency, slaughter yield and meat quality in growing rabbits of two genotypes (Grimaud, G vs. Hyla, H). A total of 384 crossbred rabbits (192 G and 192 H), half males and half females, were divided into eight experimental groups according to a bi-factorial arrangement (2 genotypes × 4 diets; 48 animals/group) and reared in individual cages. From 33 to 64 days of age, rabbits were fed four diets obtained by combining two DE levels (high, HE—10.9 MJ/kg vs. low, LE—9.2 MJ/kg, on average) and two CP levels (high, HP—159 g/kg vs. low, LP—144 g/kg, on average). Then, all rabbits received the same fattening diet (10.7 MJ DE/kg; 156 g CP/kg) until slaughtering (77 days of age). Growth performance did not differ between genotypes for the entire trial (on average final live weight 3010 g; daily weight gain 50.5 g/d), but H rabbits showed a faster growth during the post-weaning period (p ≤ 0.01) compared to G rabbits, while exhibiting lower slaughter yield and lower carcass fatness (p ≤ 0.01). As DE level increased, feed intake decreased and feed conversion improved (p < 0.001), while caecal volatile fatty acid concentration increased and caecal pH and N-ammonia decreased (p ≤ 0.01). The reduction in the CP level did not affect performance and carcass traits. No significant interaction was detected between genotype and diet. In conclusion, G rabbits may have an advantage over H rabbits because of the higher slaughter yield. As for the nutritional characteristics of diets for high-producing crossbred rabbits, high energy levels are confirmed to enhance feed efficiency, whereas dietary CP can be reduced to 144 g/kg without negative effects on performance and carcass traits.

Early Introduction of Plant Polysaccharides Drives the Establishment of Rabbit Gut Bacterial Ecosystems and the Acquisition of Microbial Functions

In mammals, the introduction of solid food is pivotal for the establishment of the gut microbiota. However, the effects of the first food consumed on long-term microbiota trajectory and host response are still largely unknown. This study aimed to investigate the influences of (i) the timing of first solid food ingestion and (ii) the consumption of plant polysaccharides on bacterial community dynamics and host physiology using a rabbit model. To modulate the first exposure to solid nutrients, solid food was provided to suckling rabbits from two different time points (3 or 15 days of age). In parallel, food type was modulated with the provision of diets differing in carbohydrate content throughout life: the food either was formulated with a high proportion of rapidly fermentable fibers (RFF) or was starch-enriched. We found that access to solid food as of 3 days of age accelerated the gut microbiota maturation. Our data revealed differential effects according to the digestive segment: precocious solid food ingestion influenced to a greater extent the development of bacterial communities of the appendix vermiformis, whereas life course polysaccharides ingestion had marked effects on the cecal microbiota. Greater ingestion of RFF was assumed to promote pectin degradation as revealed by metabolomics analysis. However, transcriptomic and phenotypic host responses remained moderately affected by experimental treatments, suggesting little outcomes of the observed microbiome modulations on healthy subjects. In conclusion, our work highlighted the timing of solid food introduction and plant polysaccharides ingestion as two different tools to modulate microbiota implantation and functionality.

IMPORTANCE Our study was designed to gain a better understanding of how different feeding patterns affect the dynamics of gut microbiomes and microbe–host interactions. This research showed that the timing of solid food introduction is a key component of the gut microbiota shaping in early developmental stages, though with lower impact on settled gut microbiota profiles in older individuals. This study also provided in-depth analysis of dietary polysaccharide effects on intestinal microbiota. The type of plant polysaccharides reaching the gut through the lifetime was described as an important modulator of the cecal microbiome and its activity. These findings will contribute to better define the interventions that can be employed for modulating the ecological succession of young mammal gut microbiota.

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

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

Gut Microbiota Modulate Rabbit Meat Quality in Response to Dietary Fiber

Antibiotics are widely used in gastrointestinal diseases in meat rabbit breeding, which causes safety problems for meat products. Dietary fiber can regulate the gut microbiota of meat rabbits, but the mechanism of improving meat quality is largely unknown. The objective of this study was to evaluate the effects of adding different fiber sources to rabbit diets on the growth performance, gut microbiota composition, and muscle metabolite composition of meat rabbits. A total of 18 New Zealand white rabbits of similar weight (40 ± 1 day old) were randomly assigned to beet pulp treatment (BP), alfalfa meal treatment (AM), and peanut vine treatment (PV). There were 6 repeats in each treatment and all were raised in a single cage. The predictive period was 7 days and the experimental period was 40 days. The results revealed that AM and PV supplementation increased growth performance, slaughter performance, and intestinal development of meat rabbits compared with the BP treatment, and especially the effect of AM treatment was better. The content of butyric acid was increased in PV and AM treatments compared with the BP treatment. The expression of mitochondrial biosynthesis genes of liver, cecum, and muscle showed that AM treatment increased gene expression of CPT1b compared to the BP treatment. In addition, AM and PV treatments significantly increased the microbial diversity and richness compared with BP treatment, and their bacterial community composition was similar, and there were some differences between AM and PV treatments and BP treatment. Metabonomics analysis of muscle showed that AM treatment significantly increased amino acid and fatty acid metabolites compared with BP treatment, which were mainly concentrated in energy metabolism, amino acid metabolism, and fatty acid regulation pathways. Furthermore, through correlation analysis, it was found that there was a significant correlation between rumenococci in the cecum and amino acid metabolites in the muscle. Overall, these findings indicate that AM may affect the body's health by changing its gut microbiota, and then improving meat quality, and the intestinal–muscle axis provides a theoretical basis.

Prophylaxis of microelementosis in rabbits using a mixture of glauconite, succinic, humic and fulvic acids and minerals

Impaired metabolism of mineral substances in the conditions of industrial rabbit breeding may cause decrease in increment of live mass, reduction of immunity, mass morbidity and death of animals. In our experiment, we studied the efficiency of using a mineral mixture to prevent the disorders in the metabolism of rabbits according to changes in morphologic, biochemical parameters and antioxidant status of blood, chemical composition of blood plasma and increments in body weight compared to the control group of animals. For the studies, we formed four groups of white New Zealand rabbits, each comprising six individuals aged 70 days with mean body weight equaling 1.99 kg. In group I, the rabbits received an aqueous form of a mixture of glauconite, succinic acid, humic and fulvic acids and lactates of zinc, manganese, cuprum, cobalt and iron with water, rabbits of group II were given a dry form of a mixture of glauconite, succinic acid, humic and fulvic acids and lactates of zinc, manganese, cuprum, cobalt and iron with fodder, and the rabbits of group III were intramuscularly injected with butanol fraction of humic acids. The experiment lasted for 21 days. The results of the experiment indicate that the most effective prophylaxis of malfunctions of mineral metabolism in white New Zealand rabbits aged 70–95 was dry mixture of glauconite, succinic acid, humic and fulvic acids and lactates of zinc, manganese, cuprum, cobalt and iron with fodder (group II), which was given once a day for 21-day period. We determined a positive effect of biologically active supplement on the parameters of hematopoiesis(1.25 times significantly higher level of hemoglobin and 1.14 times higher number of erythrocytes), metabolism of proteins (1.54 times significantly higher content of albumins), mineral substances (significantly higher content of inorganic phosphorus – by 1.17 times, calcium by 2.18 times, manganese by 1.39 times, zinc by 1.50 times, iron by 1.39 times and cuprum by 1.49 times), functional condition of the liver (2.04 times lower activity of gamma-glutamyltransferase), the state of the antioxidant system (lowest catalase activity) and energy of rabbits’ growth (1.20-fold increment in body weight). The results of our study indicate that using a dry form of the mixture of glauconite, succinic acid, humic and fulvic acids and lactates of zinc, manganese, cuprum, cobalt and iron with fodder is an efficient method of preventing malfunctioning of mineral metabolism in rabbits.

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.

Agronomic and In Vitro Quality Evaluation of Dual-Purpose Cereals Clipped at Variable Ages and Their Utilization in Rabbit Feeding

The present study included two experiments; the first one investigated the forage productivity and in vitro quality of a single cut taken at different plant ages (45, 60, and 75 days after sowing—DAS) from four prominent cereal crops, namely, barley, oat, triticale, and ryegrass, grown during two successive winter seasons in Northern Egypt. In addition, the effect of plant age at forage removal on the crop’s regrowth ability and final grain yield was quantified. The second experiment studied the biological in vivo effects of the four crops’ hay cut at the optimum plant age on growth performance, feed utilization, and apparent nutrients’ digestibility of growing rabbits. Despite the progressive increase in the fresh and dry matter yields produced from the four crops with later forage removal and the relatively high quality of the forage removed at 45 DAS, 1st experiment concluded that forage removal at 60 DAS produced a reasonable amount of fresh and dry matter yields with appropriate in vitro quality. Meanwhile, the gain in forage yield, when forage was removed at 60 DAS, was enough to compensate for the consequent reduction in grain yield of the four evaluated crops. The inclusion of variable percentages (0, 10, and 20%) of the four tested crops’ hay, when cut at 60 DAS, in the rabbit’s diet (2nd experiment), resulted in non-significant variations in the rabbit’s final body weight. Meanwhile, regardless of the percentage, the rabbits that were fed on diets including ryegrass hay and barley hay had the highest significant daily weight gain. The best feed conversion ratios were obtained by the rabbits that were fed on diets containing 10 and 20% ryegrass hay as well as 20% triticale hay. The highest dry matter, organic matter, and crude protein digestibility coefficients were obtained by both groups of rabbits that were fed on diets containing 20% ryegrass hay and barley hay. The inclusion of any of the four crops’ hay in the rabbits’ diet resulted in significantly higher digestibility coefficients for all nutrients compared to the control rabbits except for ether extract digestibility. Among the four evaluated crops’ hay, ryegrass hay was found to have an outstanding impact on the productive performance and digestibility of growing rabbits. In growing dual-purpose cereals, it is recommended to cut the crops at 60 DAS to achieve the optimum balance between forage yield and quality on the one hand and final grain yield on the other hand. Moreover, when cut at 60 DAS, the evaluated hay of the four crops was adequate to be included in the rabbits’ diet up to 20% substitution of the commercial fiber sources.

Nutrition for Pocket Pets (Ferrets, Rabbits, and Rodents)

Although the companion animal population is predominantly canine and feline, the popularity of domesticated small mammals (or pocket pets) has been steadily increasing. As a result, ferrets, rabbits, and rodents can be expected to present for veterinary evaluation. Many common medical problems in pocket pets are often associated with poor husbandry and/or inappropriate nutrition and are thus responsive to nutritional therapies. Although this article touches on minor background information and husbandry, the primary foci are the basic nutritional needs of, and common nutrition-responsive diseases in, pocket pets. Detailed husbandry needs are beyond the scope of this article.

Characterisation and In Vitro Evaluation of Fenugreek (Trigonella foenum-graecum) Seed Gum as a Potential Prebiotic in Growing Rabbit Nutrition

Simple Summary

A fenugreek seed gum, extracted from Trigonella foenum-graecum seeds and rich in galactomannan, was chemically and physically characterised and its prebiotic potential for young rabbits was evaluated in vitro, both as pure fenugreek seed gum and when included up to 20 g/kg in rabbit diets rich in soluble and insoluble fibre. Fenugreek seed gum was resistant to pepsin and pancreatin digestion but was totally fermented by rabbit caecal bacteria. Fenugreek seed gum linear inclusion up to 20 g/kg in diets rich in soluble fibre has led to a reduction in the solubility of some nutrients during in vitro enzymatic phase and an increase in the fermented fraction. Fenugreek seed gum satisfies two essential conditions of a prebiotic: resistance to enzymatic digestion and being totally fermented by caecal bacteria.

Abstract

Some components of soluble fibre appear to have prebiotic effects that can contribute to improving digestive health in post-weaning rabbits. In this work, a fenugreek seed gum (FGS), extracted from Trigonella foenum-graecum seeds and rich in galactomannan, was characterised. Both the pure FSG and ten substrates obtained by the inclusion of 0, 5, 10, 15 and 20 g/kg of FSG in diets rich in soluble (SF) and insoluble (IF) fibre were evaluated in vitro to determine FSG prebiotic potential for rabbit diets. FSG was rich in total sugars (630 g/kg dry matter), consisting entirely of galactose and mannose in a 1:1 ratio, and a moderate protein content (223 g/kg dry matter). Pure FSG was affected very little by in vitro digestion, as only 145 g/kg of the FSG was dissolved during the enzymatic phase. However, the linear inclusion of FSG up to 20 g/kg in growing rabbit feeds has led to a reduction in the solubility of some nutrients during in vitro enzymatic phase, especially in SF diets. Pure FSG not digested during the enzymatic phase almost completely disappeared during the in vitro fermentation phase, 984 g/kg of this indigestible fraction. However, although linear inclusion of FSG up to 20 g/kg in SF diets increased the fermented fraction, no relevant changes in the fermentation profile were observed. In conclusion, FSG satisfies two essential conditions of the prebiotic effect, showing resistance to in vitro enzymatic digestion and being totally fermented in vitro by caecal bacteria, although in vivo studies will be necessary to determine its prebiotic potential.

Effects of the dietary digestible fiber-to-starch ratio on pellet quality, growth and cecal microbiota of Angora rabbits

OBJECTIVE

Substituting starch with digestible fiber (dF) can improve digestive health of rabbits and reduce costs. Therefore, it is necessary to develop a criterion for dF and starch supply. Effects of the dietary dF-to-starch ratio on pellet quality, growth and cecal microbiota of Angora rabbits were evaluated.

METHODS

Five isoenergetic and isoproteic diets with increasing dF/starch ratios (0.59, 0.66, 0.71, 1.05, and 1.44) were formulated. A total of 120 Angora rabbits with an average live weight of 2.19 kg were randomly divided into five groups with four replicates. At the end of 40 day feeding trial, cecal digesta were collected to analyse microbiota.

RESULTS

The results showed that the dF/starch ratio had linear effects on pellet variables (p<0.01). When the dF/starch ratio was 1.44, the pellets had the lowest powder and highest durability. The dF/starch ratio had unfavorable linear effects on growth variables (p<0.001). When analyzed by quadratic regression, the optimal dF/starch ratios for average weight gain and feed/gain were 0.59 and 0.74, respectively. There were differences in wool yield, fiber length and fiber diameter caused by the dF/starch ratio (p<0.05), and the dF/starch ratios that ranged from 0.66 to 1.06 were appropriate for good results. The cecal microbiota operational taxonomic unit (OTU) number index in the 1.05 dF/starch treatment was higher than that in the 0.66 and 0.71 dF/starch treatments. The higher dF/starch ratio resulted in a higher cecal microbiota OTU number index (p<0.05). The proportion of Ruminococcus in the 0.71 dF/starch treatment was higher than that in the 0.59 dF/starch treatment (p<0.05).

CONCLUSION

The most suitable dF/starch ratio for feed pellet quality is 1.44, and for rabbit growth the optimal range of ratios is from 0.59 to 0.74. With combination of the wool growth, output cost, and cecal microbiota, we suggest that a dietary dF/starch ratio ranging from 0.74 to 1.06 is optimal.

Reliability of acid-insoluble ash as internal marker for the measurement of digestibility in rabbits

<p>The present study aimed to evaluate acid-insoluble ash (AIA) as an internal marker for the measurement the coefficient of total tract apparent digestibility (CTTAD) in rabbits through two experiments (E1 and E2). In E1, 48 rabbits were used to calculate the CTTAD of the same basal diet according to the European reference method (ERM), the AIA and the titanium dioxide (TiO₂ with 1 g of TiO₂/kg diet) techniques (n=16 rabbits/method). The effect of feed sample quantity on dietary AIA content was investigated and total collection of faeces was carried out to calculate marker recovery. In E2, 48 rabbits were allotted to three groups fed diets with no sugar beet pulp (SBP0) or with 100 (SBP100) and 200 (SBP200) g sugar beet pulp/kg (n=16 rabbits/group). Each group was divided into two subgroups, ERM and AIA (n=8 rabbits/subgroup), in which CTTAD was measured using the European reference and AIA method, respectively. In AIA subgroups, only 10% of the total daily faecal output was sampled from 9:00 to 9:30 am. Feed analysis in E1 showed that increasing sample quantity from 5 to 9 g did not affect the dietary AIA content; however, the analytical error was 7 and 5 times lower (<em>P</em>&lt;0.05) for 9 g, when compared to 5 and 7 g samples. Feed analysis also showed 1.030±0.003 g TiO₂/kg diet. Faecal marker recovery was 99.80±0.03 and 96.89±0.16% for AIA and TiO₂, respectively. The CTTAD of dry matter (DM), did not differ between methods in E1, but a 5-fold higher variability (<em>P</em>&lt;0.05) was observed for the TiO₂ technique in comparison with the ERM and AIA methods. Also, no differences in the CTTAD of DM between the ERM and AIA methods were found in E2. In conclusion, AIA is a reliable internal marker in rabbits and offers the possibility of measuring the CTTAD of diets with precision, when complete faecal collection or feed intake measurement is not possible.</p>

Faecal microbiota and functional capacity associated with weaning weight in meat rabbits

Weaning weight is an important economic trait in the meat rabbit industry. Evidence has linked the gut microbiota to health and production performance in rabbits. However, the effect of gut microbiota on meat rabbit weaning weight remains unclear. In this study, we performed 16S rRNA gene sequencing analysis of 135 faecal samples from commercial Ira rabbits. We detected 50 OTUs significantly associated with weaning weight. OTUs that showed positive associations with weaning weight were mostly members of the family Ruminococcaceae which are important in degrading dietary fibres and producing butyrate. On the contrary, OTUs annotated to genera Blautia, Lachnoclostridium and Butyricicoccus correlated with fat deposition were negatively associated with weaning weight. Predicted functional capacity analysis revealed that 91 KOs and 26 KEGG pathways exhibited potential correlations with weaning weight. We found that gut microbiota involved in the metabolism of amino acids, butanoate, energy and monosaccharides affected weaning weight. Additionally, cross-validation analysis indicated that 16.16% of the variation in weaning weight was explained by the gut microbiome. Our findings provide important information to improve weaning weight of meat rabbits by modulating their gut microbiome.

Dynamic role of single-celled fungi in ruminal microbial ecology and activities

In ruminants, high fermentation capacity is necessary to develop more efficient ruminant production systems. Greater level of production depends on the ability of the microbial ecosystem to convert organic matter into precursors of milk and meat. This has led to increased interest by animal nutritionists, biochemists and microbiologists in evaluating different strategies to manipulate the rumen biota to improve animal performance, production efficiency and animal health. One of such strategies is the use of natural feed additives such as single-celled fungi yeast. The main objectives of using yeasts as natural additives in ruminant diets include; (i) to prevent rumen microflora disorders, (ii) to improve and sustain higher production of milk and meat, (iii) to reduce rumen acidosis and bloat which adversely affect animal health and performance, (iv) to decrease the risk of ruminant-associated human pathogens and (v) to reduce the excretion of nitrogenous-based compounds, carbon dioxide and methane. Yeast, a natural feed additive, has the potential to enhance feed degradation by increasing the concentration of volatile fatty acids during fermentation processes. In addition, microbial growth in the rumen is enhanced in the presence of yeast leading to the delivery of a greater amount of microbial protein to the duodenum and high nitrogen retention. Single-celled fungi yeast has demonstrated its ability to increase fibre digestibility and lower faecal output of organic matter due to improved digestion of organic matter, which subsequently improves animal productivity. Yeast also has the ability to alter the fermentation process in the rumen in a way that reduces methane formation. Furthermore, yeast inclusion in ruminant diets has been reported to decrease toxins absorption such as mycotoxins and promote epithelial cell integrity. This review article provides information on the impact of single-celled fungi yeast as a feed supplement on ruminal microbiota and its function to improve the health and productive longevity of ruminants.

Nutritive value of two types of olive cake (Olea europaea l.) for growing rabbit

<p>The nutritive value of 2 types of sun-dried olive cake (OC), extracted traditionally (COC) or with a 3-phase olive cake (TPOC), was studied for the growing rabbit. Four diets containing 10 or 20% of COC (COC10 and COC20) or of TPOC (TPOC10 and TPOC20) in substitution for a basal diet were compared to a control diet without OC (OC0). Five groups of 12 rabbits were fed one of the 5 diets ad libitum from weaning (35 d) to 46 d of age. The faecal digestibility was individually measured between 42 and 46 d of age. COC and TPOC are high fibre and lignin sources, with 707 and 787 g/kg dry matter (DM) of neutral detergent fibre, 530 and 554 g/kg DM of acid detergent fibre, 242 and 243 g/kg DM of acid detergent lignin, respectively. Replacing 20% of basal diet by COC sharply reduced (<em>P</em>&lt;0.001) the digestibility of energy and crude protein from 0.67 to 0.54, but that of protein only moderately (from 0.80 to 0.76). The same effect was observed with the incorporation of 20% of TPOC. The digestible energy (DE) content of COC and TPOC were calculated by regression and were 3.24±0.41 and 2.94±0.52 MJ DE/kg DM respectively, corresponding to an apparent faecal digestibility of the gross energy of 0.14 (COC) and 0.13 (TPOC). The apparent faecal digestibility of the crude protein of COC was 7 units higher than TPOC (0.44 vs. 0.37) and the digestible protein (DP) content was 20% higher (27.9±4.2 g vs.22.4±6 g DP/kg DM). Olive cake could be considered as a high fibre source with a low protein and energy content for the growing rabbit.</p>

Diversity and Co-occurrence Pattern Analysis of Cecal Microbiota Establishment at the Onset of Solid Feeding in Young Rabbits

This study aimed to evaluate how the feeding strategy of rabbit kits at the onset of solid feed intake could affect ecological diversity and co-occurrence patterns of the cecal bacterial community. From birth to 18 days of age kits were exclusively milk-fed, and between 18 and 35 days the young rabbits also had access to solid feed. After weaning at (35 days), young rabbits were exclusively fed solid feed. Three experimental feeds were used: a high concentrate diet [H: 10.16 MJ digestible energy (DE)/kg and 15.3% crude protein (CP)], a low concentrate diet (L: 9.33 MJ DE/kg and 14.7% CP) and a reproductive female diet (R: 10.57 MJ DE/kg and 17.3% CP). The rabbit kits (n = 357) were divided into three groups, differing by the diet received during two periods: from 18 to 28 and from 28 to 49 days of age. In the groups LL and HH, rabbit kits were fed L or H diets, respectively, during both periods. Kits in the group RL received feeds R and L from 18 to 28 and 28 to 49 days of age, respectively. Cecal bacterial communities of 10 rabbits per group were carried out at 18, 28, 35, 43 and 49 days of age by MiSeq Illumina sequencing 16S rRNA encoding genes. Between 18 and 28 days of age, solid feed intake was higher in the group RL compared to the other two groups (+24%; P < 0.01). Overall, 13.4% of the OTUs detected were present in the cecal ecosystem from 18 to 49 days old, whereas 17.4% were acquired with the onset of solid feeding and kept from 28 days on. Exclusive milk consumption constrains the bacterial community toward a similar structure but high phylogenetic beta-diversity. Introduction of solid feed induced a sharp change of microbial community structure and decreased phylogenetic diversity. A strong relationship in bacterial community network occurred only from 43 days on. Our feeding strategy at the onset of solid feed ingestion exhibited only a moderate effect on the microbial community structure (P = 0.072), although the LL group seemed to reach faster maturity compared to the two other groups.

Gut microbiota profiling with differential tolerance against the reduced dietary fibre level in rabbit

Dietary fibre is well acknowledged to be critical in maintaining the gut homeostasis in human and other monogastric animals. As a small monogastric herbivorous animal, rabbit is much sensitive to the reduced intake of dietary fibre and more interestingly shows individual difference in clinical tolerance. In the present study, we fed rabbits with fibre-deficiency diet for two weeks and successfully distinguished the individual tolerances according to clinical signs and gastrointestinal gross lesions. A total of 40 treatments were classified into three groups of the full health (N = 10), moderate intestinal disorder (N = 11) and severe intestinal disorder (N = 19). Together with three controls, 43 individuals were subjected to gut microbiota profiling by 16S rRNA gene sequencing. It was revealed that the Firmicutes/Bacteroidetes ratio steadily decreased from 1.74 in healthy group to 1.03 in severe group. However, the healthy individuals that showed complete tolerance still remained a comparable Firmicutes/Bacteroidetes ratio with controls. Notably, the class Alphaproteobacteria was found to be higher abundance in healthy group than controls and other treatment groups. The results would improve our understanding of the relationship among dietary fibre, gut microbiota and host health.

Stress-strain analysis of duodenal contractility in response to flow and ramp distension in rabbits fed low-fiber diet

BACKGROUND

Previously we demonstrated that low-fiber diet in rabbits affects the passive mechanomorphological properties in the small intestine, resulting in reduced intestinal wall thickness and collagen content, as well as intestinal wall softening. The aim of the present study was to evaluate the contractility in rabbits on long-term low-fiber diet and specifically to compare the contraction threshold, the frequency, and the amplitude of flow-induced and distension-induced contractions in the duodenum between rabbits on normal diet and on long-term low-fiber diet.

METHODS

Ten rabbits were fed a low-fiber diet for 5 months (Intervention group), and five rabbits were fed normal diet (Control group). The duodenal segments were used for determination of mechanical parameters for analyses of contractility. The duodenal experiments were carried out in organ baths containing physiological Krebs solution. Pressure and diameter changes induced by contractions in response to flow and ramp distension were measured. The frequencies and amplitude of contractions were analyzed. Distension-induced contraction thresholds and maximum contraction amplitude of flow-induced contractions were calculated in terms of mechanical stress and strain. Multiple linear regression analyses were applied to study dependencies between contractility parameters and wall thickness, wall area, and muscle layer thickness.

KEY RESULTS

During distension, the pressure, stress, and strain thresholds for induction of phasic contraction were biggest in the Intervention Group (P < 0.05). In addition, the contraction frequencies during flow-induced contraction were highest in the Intervention Group (P < 0.05), whereas the maximum contraction amplitudes in terms of pressure, diameter, stress, and strain were lowest in the Intervention Group (P < 0.05). The contraction thresholds and contraction frequencies were negatively associated with the wall thickness, wall area, and muscle layer thickness, whereas maximum contraction amplitudes were positively associated with the wall thickness, wall area, and muscle layer thickness.

CONCLUSIONS AND INFERENCES

Duodenal contractility in rabbits fed with long-term low-fiber diet exhibited low contraction amplitudes and high contraction thresholds and frequencies. The changes were associated with the low-fiber diet-induced histomorphological remodeling. Studies on detailed structural and functional diet-induced changes in smooth muscle and intestinal nerves are needed for better understanding the remodeling mechanisms.

Effect of substituting guinea grass with sunflower hulls on production performance and digestion traits in fattening rabbits

The objective of this study was to evaluate the use of sunflower hulls (SH) to substitute guinea grass (GG), traditionally used as a fibre source in the diets of fattening rabbits, on production performance, coefficients of total tract apparent digestibility (CTTAD) of nutrients, gastrointestinal tract development and caecal fermentation. A total of 160 mixed sex Hyla commercial meat rabbits were allocated to 4 experimental groups (40 per treatment) differing in the SH level inclusion in the diet offered to rabbits from 40 to 90 d of age: 0, 30, 60 and 90 g/kg on as-fed basis: SH0, SH30, SH60 and SH90 groups, respectively. Growth performance was recorded from 47 to 90 d of age, CTTAD of nutrients from 86 to 90 d of age, and gastrointestinal tract development, caecal fermentation and carcass traits were determined at 90 d of age. Increasing substitutions of SH in the diet indicated effects on growth performance, as higher feed intake and lower feed efficiency were observed in SH90 compared with SH0 (<em>P</em>-linear&lt;0.05). Moreover, the higher SH substitution diet (SH60 and SH90) increased the relative caecum weight (<em>P</em>-linear&lt;0.05). A linear negative effect of SH inclusion was observed for the digestibility of neutral detergent fibre (CTTAD from 0.294 to 0.232) and acid detergent fibre (CTTAD from 0.182 to 0.136; <em>P</em>-linear&lt;0.05). Dietary SH substitution level had a quadratic effect on the villus height of the duodenum, jejunum and ileum obtained (<em>P</em>-quadratic&lt;0.05), and the highest were observed in the SH60 group. There was a quadratic effect on the pH of caecum content (<em>P</em>-quadratic&lt;0.05), and the lowest was 6.08 in SH30 group. The total volatil fatty acids increased linearly with increasing SH in diets (from 71.11 to 76.98 mmol/L; <em>P</em>-linear&lt;0.05), and when dietary SH increased, the proportion of acetate tended to increase (<em>P</em>-linear&lt;0.05), and the proportions of propionic and butyric were decreased (<em>P</em>-linear&lt;0.05, respectively). Substitution of GG with SH had no effect on carcass characteristics and meat quality. The current work shows that SH can replace up to 60 g/kg in diets for fattening rabbits, with no adverse impact on aspects of production performance or digestion traits.

Effects of the particle of ground alfalfa hay on the growth performance, methane production and archaeal populations of rabbits

The world's annual output of rabbits is over 1.2 billion, therefore this sector is also one of the sources of greenhouse gases in livestock production. One hundred-twenty New Zealand rabbits were allocated into four treatments, five replicates in each treatment and six rabbits in each replicate to examine the effect of grinding alfalfa hay to different sizes on growth performance, methane production and cecal archaeal populations. The particle sizes of the alfalfa meal in the four treatment diets were 2500, 1000, 100 and 10 μm, while the other ingredients were ground through a 2.5 mm sieve. The average daily gain (ADG) and average daily feed intake (ADFI) increased (P<0.001) as the particle size decreased, but the feed conversion ratio (FCR) was not affected (P = 0.305). The digestibility of neutral detergent fiber (NDF) (P = 0.006) and acid detergent fiber (ADF) (P<0.006) increased while the greatest digestibility of crude protein (CP) was obtained in 1000 um group (P = 0.015). The rabbits produced more methane (CH4, L/kgBM0.75/d) with decreasing alfalfa particle size (P<0.001). The molar proportion of acetic acid and propionic acid decreased (P<0.001) at the cost of butyric acid (P<0.001). The greatest villus height:crypt depth ratio were obtained in 1000 μm group, and the decrease in the alfalfa hay particle size decreased the jejunum and ilem villus height:crypt depth ratio (P<0.05). The gastric muscular and mucosal thickness decreased with decreasing alfalfa particle size (P<0.05). Archaea diversity decreased with decreasing alfalfa particle size, and the relative abundance of genus Methanobrevibacter increased (P<0.001) while the genus Methanosphaera decreased (P<0.001). It is concluded that a finer particle size favors the growth of genus Methanobrevibacter, which produces more methane but promotes the growth performance of rabbits.

White lupin bran and its effects on the growth performance, carcass characteristics and digestibility of nutrients in fattening rabbits

<p>The purpose of the present study was to evaluate the effects of including white lupin bran (WLB) in a fattening rabbit diet on growth, carcass traits and nutrient digestibility. The C diet (control) based on alfalfa meal, whereas the WLB 5 and WLB 15 diets were based on white lupin bran (crude protein 152 g/kg, neutral detergent fibre 524 g/kg as-fed basis). The WLB 5 diet contained 50 g of white lupin bran/kg instead of 50 g of alfalfa meal/kg, whereas the WLB 15 diet contained 150 g of white lupin bran/kg, 5 g of soybean meal/kg and 10 g of sugar beet pulp/kg instead of 165 g of alfalfa meal/kg. The diets had similar digestible protein/digestible energy ratios. A total of 150 Hyplus rabbits between the ages of 30 to 73 d were randomly allocated into one of 3 groups and fed one of the 3 experimental diets. Additionally, another 30 Hyplus rabbits (10 per dietary treatment) at the age of 30 d were selected to determine coefficients of total tract apparent digestibility (CTTAD) of diets between 63 and 67 d of age. The dietary treatments did not affect the final live weight of rabbits (mean=2969 g). There was a higher feed intake (+30 g/d; P&lt;0.001) in both groups of rabbits fed the WLB 5 and WLB 15 diets compared to rabbits fed the C diet, which led to impaired feed conversion ratios (P&lt;0.001). Sanitary risk index was not affected by dietary treatment. The rabbits fed the WLB 15 diet exhibited a higher drip loss percentage (+0.65%; P&lt;0.001) than the rabbits fed the other diets, as well as a lower dressing-out percentage (by 1.6%; P=0.024). The CTTAD of the lignocellulose fraction (acid detergent fibre) was significantly higher in rabbits fed the WLB 5 and WLB 15 diets than in those fed the C diet. White lupin bran may be used as a dietary fibrous by-product without significant impairment of the nutritive value of the diet. This lupin by-product can be included in diets for fattening rabbits up to 15% as a partial replacement of alfalfa meal.</p>

Effect of simplified feeding based only on wheat bran and brewer’s grain on rabbit performance and economic efficiency

<p>Simplified diets are based on maximum incorporation of fodder and/or by-products into animal feed, thus minimizing the formulation and the costs. This study aimed to evaluate the possibility of feeding fattening rabbits with a simplified diet composed of only two agro-industrial by-products inexpensive and locally available: brewer’s grain and wheat bran. At weaning (35 days), 68 rabbits were divided into two identical groups (mean weight = 833 g) and housed in individual cages until slaughter (77 days). Each of the two groups (B0 and SF) was fed <em>ad libitum</em> either a commercial pelleted feed (control), or a simplified pelleted  experimental diet "SF" containing 72% wheat bran and 27% brewer’s grain. The feed conversion was within the standards and similar in the two groups (3.55 on average). The growth rate and feed intake of B0 group were 12% higher (P &lt;0.001) than that of the SF group (35.2g <em>vs</em> 31.2 and 128.3 <em>vs </em>113 g/d). The cold carcass yield and the carcass weight were respectively higher (P &lt;0.001) by 4 units and by 9% in the control group. The carcass of SF group was less fatty (perirenal fat: -23%, inguinal fat: -41% and scapular fat:-14%). The economic efficiency was 40% better for SF diet with almost 50 Algerian Dinar more benefit (/kg of meat).</p><p> </p>

Nutritive value of citrus co-products in rabbit feeding

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

Evidence-Based Rabbit Housing and Nutrition

Because most research on rabbit husbandry, welfare, and nutrition was performed on production animals, evidence for best practices in pet rabbits is scarce, and guidelines must be based on transfer of results, deduction, and common sense. Rabbits benefit from being kept with at least one conspecific; from large enclosures and multistory hutches; from drinking water offered ad libitum in open dish drinker systems; and from receiving hay ad libitum, with restricted amounts of fresh grass, herbs, or green leafy vegetables, and a high-fiber complete diet. Offering hay ad libitum bears several advantages and should be considered a matter of course.

Effect of feed restriction and feeding plans on performance, slaughter traits and body composition of growing rabbits

Two feeding systems (L, <em>ad libitum vs. </em>R, feed restriction) were combined with 3 feeding plans (MM, MH, HH) to evaluate the effects on performance, slaughter results, body composition and nitrogen balance of 300 commercial crossbred rabbits kept individually from weaning to slaughter (34-70 d of age). The R rabbits were fed from 80% (first days on trial) to 100% (end of 3rd wk) of <em>ad libitum </em>intake, whereafter R rabbits had free access to feed. The 3 feeding plans were: MM plan, M diet with moderate digestible energy (DE) content, 10.6 MJ/kg, throughout the trial; HH plan, H diet with high DE content, 11.1 MJ/kg, throughout the trial; MH plan, M diet for the first 3 wk and H diet for the last 2 wk. Feed restriction did not affect nutrient digestibility, growth rate on the whole trial and slaughter results, but improved feed conversion (2.96 <em>vs. </em>2.89 in L and R rabbits, respectively; <em>P</em>&lt;0.01) and reduced N excretion (2.16 <em>vs. </em>2.07 g excreted N/d, in L and R rabbits; <em>P</em>&lt;0.05). At the end of the first period (55 d), R rabbits showed lower empty body protein, lipid, and gross energy gains than L rabbits, but differences disappeared within the end of the trial. The HH plan improved feed conversion (2.97 <em>vs. </em>2.89 for MM <em>vs. </em>HH; <em>P</em>&lt;0.05), but increased excreted N (2.03 <em>vs. </em>2.17 g/d; <em>P</em>&lt;0.001) in comparison with the MM plan due to the higher digestible protein/DE ratio of H diet, whereas the MH plan showed intermediate results. In conclusion, a moderate feed restriction during post weaning improved feed conversion and reduced N excretion without negative effects on growth or slaughter results. Moreover, N excretion was confirmed to depend largely on dietary nitrogen content.

Low-residue diet fed to rabbits induces histomorphological and biomechanical remodeling of small intestine

BACKGROUND

The composition of ingested food is important for the gut microbiome and intestinal homeostasis. We have previously demonstrated that the structure and mechanical properties in the small intestine remodel significantly during fasting. However, it is not clear to what extent the intestinal mechanical properties changes when the composition of food is changed. This study aimed to investigate the passive biomechanical properties and intestinal tissue remodeling in rabbits fed a low-residue diet.

METHODS

New Zealand rabbits (control group n=6, intervention group n=7) were studied. Segments from duodenum, jejunum and ileum were excised. The intestinal diameter and length were obtained from digitized images of the segments at preselected luminal pressure levels and at no-load and zero-stress states. Circumferential and longitudinal stresses (force per area) and strains (deformation) were computed from the length, diameter and pressure data referenced to the zero-stress state geometry. Histomorphometric data were also obtained.

KEY RESULTS

The wet weight-per-unit length, wall thickness and wall area decreased in the intervention group (P<.05, P<.01). Histological measurement confirmed that the wall thickness decreased in all three segments, which was primarily due to mucosal thinning (P<.05). The opening angle tended to increase in all segments in the intervention group. Significant difference between the two groups was found for the jejunum (P<.05). Feeding the low-residue diet shifted the circumferential stress-strain curves in the intervention group to the right, indicating intestinal wall softening.

CONCLUSIONS & INFERENCES

Low-residue diet in rabbits for 1 month induces location-dependent histomorphometric and biomechanical remodeling of the intestine.

Intake of different hays with presence of Colchicum autumnale by rabbits

<p>The ingestion of 3 hay types by growing rabbits and the consequences on animal performance were studied in a first part. Two kinds of hay from high nature value grasslands [CFP (<em>Colchico-Festucetum pratensis</em>) and SBR (<em>Senecioni-Brometum racemosi</em>)] differentiated by their botanical composition were compared to a classical agricultural hay (control). The 3 hays, offered <em>ad libitum</em>, were ingested at 30.6, 34.8 and 36.1 g/kg body weight (BW) respectively for SBR, CFP and the control, where the consumption of SBR hay was significantly lower. (P&lt;0.01). The type of hay distributed did not affect the consumption of commercial feed or growth (44 g/kg BW and 36 g/d, respectively). The effect of meadow saffron concentration (<em>Colchicum autumnale</em>) in CFP hay was tested at 3 doses (absence, 2.75 and 15% of the distributed hay mass) with respect to their effect on ingestion and animal health. Again, no effect of the presence of meadow saffron (MeS) in the hay on these parameters was observed, even at the highest dose. However, during this second part, rabbits preferred to consume meadow saffron instead of the rest of the distributed hay (hardly any MeS was refused by rabbits at the representative dose, whereas 12% of the rest of the hay was refused, and 3.4 and 20% respectively at the maximal dose). The intake of the toxic alkaloid colchicine corresponded to 30 to 44% of the median lethal doses (LD₅₀) at the representative and maximal doses respectively. The real exposure of the rabbits was probably lower, as the absorption of ingested colchicine is reported to be around 50% of the LD₅₀ values which are established after an intravenous injection. Nevertheless, the absence of any effect should be interpreted with caution. The colchicine content of MeS varied greatly depending on the time of harvest and the parts of the plant taken into consideration. A late harvest (mid-June or later) would ensure (very) low concentrations of colchicine in the aerial parts of MeS. The presence of cloves on this plant should be completely avoided, due to the very high concentration of colchicine in the seeds. Moreover, long term exposure of the animals to this toxic plant may increase the risk of adverse effects. The study shows that hay distribution can aid digestion without altering the animal’s performance. Moreover, the valorisation of hay from high nature value grasslands would not only add real value to the commercialisation of rabbit meat by commercial breeders, but also to pet owners on the condition that hay quality would be guaranteed.</p>

Performance of growing rabbits fed increasing levels of discarded Salvia hispanica L. (chia) seed

This experiment was carried out to evaluate the effect of including five levels of discarded chia seed (DCS) on growth, energy, and economic efficiency in rabbits. Fifty crossbred (New Zealand × Californian) weaning rabbits, weighing 798 ± 170 g, were randomly assigned to the following treatments: 0 % (control), 10 % (Ch10), 20 % (Ch20), 30 % (Ch30), and 40 % (Ch40) of DCS. Ten unsexed rabbits were allocated to each treatment and housed individually in cages; the experimental period was 6 weeks. There were no statistically significant differences between treatments in final body weight (2050 g), body weight gain (30 g/rabbit/day), and carcass weight (1010 g); however, feed intake (91 g/rabbit/day in Ch20 vs. 80 g/rabbit/day in Ch40), feed conversion ratio (2.77 in control and Ch40 vs. 2.95 in Ch10, Ch20, and Ch30), energy conversion ratio (32 MJ/kg in Ch20 vs. 29 MJ/kg on average in control, Ch10, Ch20, Ch30, and Ch40), and economic efficiency (358 % in control vs. 433 % in Ch40) showed differences (P < 0.05) between treatments. Discarded chia seed can be included up to 40 % in growing rabbit diets without any adverse effects on growth and carcass weight, and increased economic efficiency.