Soluble fibre, starch and protein level in diets for growing rabbits: Effects on digestive efficiency and productive traits

Effect of Dietary Level of Beet Pulp, with or without Molasses, on Health Status, Growth Performance, and Carcass and Digestive Tract Traits of Rabbits

To evaluate the effect of dietary level of beet pulp, with or without molasses, on growth performance, a total of 470 28-day-old rabbits were used (614 ± 6 g). Animals were randomly allocated into five dietary treatment groups: Control, without beet pulp; BP20, and BP40 with 20 and 40% of beet pulp without molasses, respectively; and BPM20 and BPM40, with 20 and 40% of beet pulp with molasses, respectively. Daily feed intake (DFI) and average daily gain (ADG) were controlled at 28, 49, and 59 days of age. Carcass and digestive tract traits were also determined at 59 days of age. Mortality and morbidity were controlled daily. Mortality during the growing period was higher in BPM than in BP groups (+9.2%; p < 0.05). The higher the inclusion of beet pulp, the lower the DFI and ADG of animals (5.5 and 4.6% for every 20% inclusion, respectively; p < 0.001), as well as the dressing out percentage, the liver proportion, and the dissectible fat percentage of their carcasses. However, the best feed efficiency during the last 10 days was obtained with the BPM40 group. The higher the inclusion of beet pulp, the higher the weight of the empty gastrointestinal tract and cecum (+2.4 and +3.0 percentage points for every 20% inclusion, respectively; p < 0.001). In fact, a higher inclusion of beet pulp decreased the pH and dry matter and decreased the total volatile fatty acids content of cecum richer in acetic acid but poorer in propionic, isobutiric, isovaleric, and valeric acids. Stomach weight was lower, and the capric acid content in the cecum was higher in the BPM than in the BP group. The inclusion of beet pulp in the feed reduced the growth performance and carcass yield of growing rabbits, and an even higher incidence of digestive disorders was observed when beet pulp included molasses.

Dietary Nutritional Level Affects Intestinal Microbiota and Health of Goats

The intestine is a complex micro-ecosystem, and its stability determines the health of animals. Different dietary nutritional levels affect the intestinal microbiota and health. In this study, the nutritional levels of energy and protein in the diet of goats were changed, and the body weight was measured every 15 days. In the late feeding period, 16 S rRNA sequencing technology was used to detect the content of microorganisms. A meteorological chromatograph was used to detect volatile fatty acids in the cecum and colon of goats. In the feeding stage, reducing the nutritional level of the diet significantly reduced the weight of the lamb (p < 0.05). In the cecum, the abundance of potentially harmful bacteria, such as Sphingomonas, Marvinbryantia, and Eisenbergiella, were significantly enriched in goats fed with the standard nutritional level diets (p < 0.05). Additionally, the contents of acetate (p = 0.037) and total VFAs (p = 0.041) increased. In the colon, the abundance of SCFAs-producing bacteria, such as Ruminococcaceae, Christensenellaceae, and Papillibacter, decreased as the nutritional level in the diet increased (p < 0.05). In conclusion, the increase in nutritional level could affect the growth performance and composition of intestinal microbiota.

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.

Marine Macroalgae in Rabbit Nutrition—A Valuable Feed in Sustainable Farming

Simple Summary

Commercial rabbit farming has faced critical challenges in the last few years, during which the ban on the prophylactic use of antibiotics in animal feed has added to the weakness of the production system and a decrease in consumption of rabbit meat. Considering the potential role of macroalgae as an alternative to the use of antibiotics in animal nutrition, this review paper aims to evaluate the use of macroalgae in rabbit farming. It specifically focuses on how macroalgae can be used sustainably to improve rabbit health as an economically viable alternative that could help guarantee the future of this high-value sector.

Abstract

The rabbit meat industry has faced critical challenges in the last few years, during which the ban on the prophylactic use of antibiotics in animal feed has added to the weakness of the production system and a decrease in consumption of rabbit meat. This review paper highlights the potential value of macroalgae in the rabbit farming sector as an alternative to the use of antibiotics to improve rabbit health. In line with sustainable agriculture programmes, the use of seaweed in rabbit nutrition may improve gut health according to the One Health approach, whereby consumers and the environment could receive tangible benefits. The inclusion of algae in animal feed has experimentally proven to help to reduce intestinal dysbiosis. However, further studies evaluating the prebiotic effects of algal components on gut health and also identifying the compounds directly responsible for the antimicrobial, antiviral, antioxidative and anti-inflammatory properties of algae are still needed. Furthermore, the inclusion of marine algae in rabbit food could potentially become a commercial marketing strategy that could attract new consumers who are concerned about environmental sustainability and who are looking for different, high-quality foods.

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.

The Health and Welfare of Rabbits as Indicated by Post-Mortem Findings at the Slaughterhouse

Simple Summary

Veterinary inspection at the slaughterhouse plays an important role in the surveillance system for animal health and welfare. The study focused on the quantification and identification of pathological findings in rabbits slaughtered at the slaughterhouses in the Czech Republic in the period from 2010 to 2019. The ratio of the number of pathological findings to the total number of rabbits slaughtered was 0.0214, i.e., for every hundred rabbits, 2.14 findings were made documenting the impairment of health and/or welfare to an extent leading to pathological changes detected during the post-mortem inspection of the rabbits at the slaughterhouse. The pathological findings that occurred most often were those on the limbs (0.84%), trunk (0.71%), kidneys (0.17%), and liver (0.05%), along with generalized changes (0.37%). The results show that findings on the limbs and trunk were dominated by findings of traumatic origin. Findings in the kidneys and liver were most often of a chronic nature. Findings of abscesses were most frequent among generalized findings.

Abstract

The aim of the study was to assess post-mortem findings according to their localization and the nature of damage and to assess the standard of health and welfare of farmed rabbits on the basis of these findings. A total of 40,206 pathological findings were recorded in 1,876,929 rabbits slaughtered at slaughterhouses in the Czech Republic in the period from 2010 to 2019. Pathological findings on the limbs (0.84%), the trunk (0.71%), the kidneys (0.17%), and the liver (0.05%), along with generalized changes (0.37%), occurred most frequently. Findings of traumatic origin dominated among findings on the limbs and trunk, which indicates the inappropriate housing and handling rabbits on farms and during transport. Findings in the kidneys and liver were most often of a chronic nature having an evident correlation with the diet of intensively fed rabbits, with shortcomings in the diet having an impact on the parenchyma with chronic manifestations in the liver and kidneys. Among the generalized findings, multiple abscesses, which were probably associated with the infection of injuries occurring during fattening, and emaciation resulting from current husbandry practices, leading to insufficient feed intake or the development of disease in some individuals, predominated.

Preliminary evaluation of fenugreek (Trigonella foenum-graecum) seed gum as a potential prebiotic for growing rabbits in Tunisia: effects on in vivo faecal digestibility and in vitro fermentation

<p>This study aims to determine the effect of dietary inclusion of fenugreek seed gum (FSG), rich in galactomannans, on nutrient apparent digestibility and caecal environment, as well as on <em>in vitro</em> caecal fermentation of Tunisian growing rabbits. Three experimental diets were formulated, including 0, 0.25 and 0.5% of FSG (FSG0, FSG0.25 and FSG0.5, respectively) for the <em>in vivo</em> trial and 0, 0.125, 0.25, 0.5 and 100% of FSG (FSG0, FSG0125, FSG0.25, FSG0.5 and FSG100, respectively) for the <em>in vitro</em> trial. In the <em>in vivo</em> trial, 45 weaned rabbits 31 d old (15 per treatment) were housed in individual cages until 94 d of age. Apparent digestibility coefficients were determined at two ages, from 38 to 41 and from 56 to 59 d old, and caecal traits were recorded after slaughtering. In the <em>in vitro</em> trial, the five experimental diets were incubated with a rabbit caecal inoculum. Gas production was measured and modelled until 72 h and the fermentation traits were measured. Apparent faecal digestibility coefficients of main nutrients and main caecal environment traits were not significantly affected by the dietary inclusion of FSG (<em>P</em>&gt;0.05). However, animals fed with FSG showed lower caecal pH (–0.15; <em>P</em>&lt;0.05) values. Regarding the in vitro fermentation, FSG100 increased asymptotic gas production (+11.25, <em>P</em>&lt;0.001), sharpness of the switching characteristic of the profile (+1.98, <em>P</em>&lt;0.001) and the maximum substrate degradation rate (RM) (+0.188, <em>P</em>&lt;0.001), but decreasing the time after incubation at which half of the asymptotic amount of gas has been formed (–5.86, <em>P</em>&lt;0.001) and at which RM occurs (–4.53, <em>P</em>&lt;0.01). Likewise, FSG100 significantly decreased caecal pH (–1.035, <em>P</em>&lt;0.001), lactic acid (–9.51, <em>P</em>&lt;0.069) and N-NH₃ concentrations (–12.81, <em>P</em>&lt;0.001). Meanwhile, it increased the total volatile fatty acids (VFA) production (+43.15, <em>P</em>&lt;0.001). Gradual dietary inclusion of FSG from 0 to 0.5% only significantly increased total VFA production in the caecum (+100 mmol/L per percentage point of FSG inclusion; <em>P</em>&lt;0.05). In conclusion, FSG is highly and rapidly in vitro fermented by rabbit caecal bacteria. However, dietary inclusion of FSG up to 0.5%, might be insufficient to affect the apparent digestibility and fermentation profile of growing rabbits to a great extent.</p>

Effect of Dietary Insoluble and Soluble Fibre on Growth Performance, Digestibility, and Nitrogen, Energy, and Mineral Retention Efficiency in Growing Rabbits

Simple Summary

Rabbits, like other herbivores, require a minimal level of insoluble fibre in the diet to warrant an adequate digestive function. Epizootic rabbit enteropathy (ERE) is the main digestive trouble in growing rabbits that increases the use of antibiotics. The increase of soluble fibre (once met insoluble fibre requirements) limits the incidence of ERE and improves nitrogen and energy balance, while high levels of insoluble fibre seem to favour ERE. This study evaluated whether the increase of soluble and insoluble fibre above the current requirements of insoluble fibre had a positive impact on mortality, growth performance, diet digestibility, and energy, nitrogen, and mineral balance. Treatments had no effect on mortality, which was low (1%). The increase of insoluble fibre reduced the dietary digestible energy, while soluble fibre only increased it when combined with a low insoluble fibre level. The group fed with the lowest insoluble and soluble fibre levels showed the best energy and mineral balance, while the increase of insoluble or soluble fibre did not improve any growth trait. We conclude that in healthy rabbits, and once the minimal insoluble fibre requirements are met, no increase of insoluble or soluble fibre is recommended.

Abstract

Dietary soluble fibre limits the incidence of epizootic rabbit enteropathy (ERE) and improves the energy and nitrogen balance in low-insoluble fibre diets, while high-insoluble fibre diets seem to favour ERE. This study assessed whether the positive effects of soluble fibre are influenced by the level of insoluble fibre. Four diets (2 × 2 factorial arrangement) were used with two levels of insoluble fibre (314 vs. 393 g/kg DM) and soluble fibre (87 vs. 128 g/kg DM), resulting in four diets with increasing total dietary fibre levels. Growth performance and chemical composition (body and carcass) (28–62 days of age), faecal digestibility (54–57 days of age), and jejunal morphometry functionality (39 days of age) were determined. Mortality was low (<1%) and treatments did not influence it. Insoluble and soluble fibre tended to reduce the growth rate (p ≤ 0.109), body protein, and fat accretion (p = 0.049 to 0.120), but only insoluble fibre impaired feed efficiency (p < 0.001). The efficiency of digestible energy used for growth was impaired with the increase of total dietary fibre (p = 0.027), while that of nitrogen remained majorly unaffected. In conclusion, in healthy rabbits, the increase of either insoluble or soluble fibre had no benefit.

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.

Molecular cloning, polymorphism, and expression analysis of the LKB1/STK11 gene and its association with non-specific digestive disorder in rabbits

Liver kinase B1 (LKB1, also called STK11) encodes a serine/threonine kinase mutated in Peutz-Jeghers cancer syndrome characterized by gastrointestinal polyposis. Although LKB1 plays an important role in regulating energy homeostasis, cell growth, and metabolism via activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), nothing is known about its molecular characteristics and possible involvement in non-specific digestive disorder (NSDD) of rabbits. In the present study, we first cloned the coding sequence (CDS) of rabbit LKB1, which consisted of 1317 bp encoding 438 amino acids (AAs) and contained a highly conserved S_TKc kinase domain. Its deduced AA sequence showed 87.93-91.10% similarities with that of other species. In order to determine its involvement in NSDD, a NSDD rabbit model was built by a dietary fiber deficiency. The polymorphic site of LKB1 was then investigated in both healthy and NSDD groups using directing sequencing. Our results suggested that a synonymous variant site (840 c. G > C, CCC→CCG) existed in its S_TKc domain, which was associated with susceptibility to NSDD. Furthermore, qPCR was utilized to examine the mRNA levels of LKB1 and its downstream targets (i.e., PRKAA2, mTOR and NF-kβ) in several intestinal-related tissues from both healthy and NSDD groups. Significant changes in their expression levels between two groups indicated that impaired LKB1 signaling contributed to the intestinal abnormality in NSDD rabbits. Taken together, it could be concluded that LKB1 might be a potential candidate gene affecting the occurrence of rabbit NSDD. This information may serve as a basis for further investigations on rabbit digestive diseases.