Performance response of lactating and growing rabbits to dietary lignin content

Nutritional ecology of European rabbit (Oryctolagus cuniculus): Factors affecting chemical composition of gastric content

Nutritional ecology seeks to unravel the extensive web of nutritional links that directs animals in their interactions with their ecological and social environments. European rabbit (Oryctolagus cuniculus) populations its endemic locations are declining and it is considered a keystone species of the Mediterranean ecosystem prompteing the interest in its conservation. The main aim of this study was to determine the nutritional composition of the diet of European rabbits through the relative and absolute chemical composition of the gastric content. To address this objective, gastric content was collected from 80 European rabbits in a Mediterranean area for the analysis of its chemical composition. To this end, gastric content was analyzed for dry matter (DM), organic matter (OM), ash, crude protein (CP), highly digestible nonnitrogenous nutrients (HDNN), neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin. The rabbits were divided into two groups: EMPTY and FULL, depending on the level of stomach filling, directly related to food intake. Our results revealed a positive correlation between the rabbits weight with DM in the gastric content, total gastric content with DM in the gastric content, and DM in gastric content with all chemical parameters analysed. The mean relative values obtained were 8.8%, 25.5%, 40.4% and 25.4%, for ash, CP, NDF and HDNN, respectively. Moreover, EMPTY rabbits had both a proportional (+19%, p = 0.002 and -40%; p = 0.004, on NDF and HDNN, respectively) and absolute (-38%, p = 0.014, -52%; p = 0.012, -52%; p = 0.011 and +83%; p = 0.008 for OM, ash, HDNN, and lignin, respectively) different proportion of nutrients in gastric contents than FULL animals. Since there is a connection between this availability and the fitness of this species, understanding the chemical composition of the rabbit's diet can be utilised to delve into its biology. Our study provides information that will help elucidate the factors affecting the chemical composition of the gastric content of European rabbits to assist land use planners and conservationists in identifying sites for conservation in Mediterranean ecosystems.

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.

Challenges in rabbit doe feeding, including the young doe

In this review is summarized the last knowledge on rabbit doe nutrition, to complement the current nutritional requirements and strategies for the young and adult rabbit does, considering the production, health, and welfare issues. The rabbit doe must reach an adequate maturity level (body condition) at first artificial insemination (AI) to face its productive life with minimal guarantees (around 7.0 mm of perirenal fat thickness, 2.8 ng/mL of plasma leptin concentration and around 18% and 15-20% of body protein and fat, respectively). This goal can be achieved by restricting feed intake from 12 weeks of age until first AI or feeding ad libitum with a fibrous diet (<10.5 MJ digestible energy/kg) from 60 d of age to first parturition. Once the doe is reproducing, the increase of the n-3 fatty acids (or reduction of the n-6/n-3 ratio), soluble fibre (under epizootic enteropathy) and the Arg/Lys and Gln/Lys ratios may help to improve the reproductive traits of rabbit does, although their optimal level of inclusion remain to be identified. It is recommended to limit an excessive negative energy balance before parturition, and the supplementation of glucose precursors to reduce the ketosis incidence could be useful. The formulation of different diets for the doe and the litter to fit better their requirements and assuring their health would be an option to consider when it would be applicable in the farm. The influence of the mother on the litter microbiota and immune status and its potential modulation through the diet open a new research area that will deserve more studies in the next future.

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.

Nutritive value of sun-dried common reed (Phragmites australis) leaves and its effect on performance and carcass characteristics of the growing rabbit

The nutritive value and potential use of sun-dried common reed (<em>Phragmites australis</em>) leaves (CRL), for growing rabbits was studied by comparing 3 diets (regression method) containing an increasing incorporation rate of CRL: 0% (control, CRL0), 15% (CRL15) and 30% (CRL30) in substitution for the control diet (356 g neutral detergent fibre (NDF) and 197 g crude protein (CP)/kg). Three groups of 37 rabbits (individually caged) were fed the 3 diets <em>ad libitum</em> from weaning (35 d, mean weight: 722±142 g) to 77 d of age. The faecal digestibility of the diets was measured between 42 and 46 d of age in 10 rabbits per group. CRL can be considered high-fibre roughage, as it contained 64% of NDF (38% of ADF and 10% ADL) and 10.2% of CP. The digestible energy (DE) content of CRL calculated by regression was null (–1.8±0.29 MJ/kg as fed). CP digestibility reached 29%, corresponding to a digestible crude protein concentration of 29.0±5.6 g/kg as fed basis. The fibre digestibility was reduced with CRL incorporation. Dietary incorporation of CRL impaired the rabbit growth (34.2 vs. 31.5 g/d during the period 35-77 d without CRL or with CRL (CRL15 and CRL30), respectively; P=0.002). Consequently, feed conversion was impaired with the high incorporation rate in feed (30%). Health status or main slaughter traits were not affected by CRL incorporation rate. Thus, the sun-dried common reed leaves had a poor nutritive value for growing rabbits and it can be considered a high-fibre feedstuff, interesting to supply low digested fibres (cellulose) and lignin.

Effects of animal type (wild vs. domestic) and diet alfalfa level on intake and digestibility of European adult rabbits (Oryctolagus cuniculus)

The aim of this study was to evaluate the effect of the level of alfalfa in the diet on feed intake and digestibility of two types of rabbits, wild (Oryctolagus cuniculus algirus) vs. domestic (O. cuniculus cuniculus). Ten wild (W; mean LW = 927 g) and 10 domestic (D; mean LW = 4,645 g) adult rabbit does were fed ad libitum two pelleted diets: a control diet (C) with 15% of dehydrated alfalfa hay (as feed basis) and a test diet (A) with 36% of dehydrated alfalfa hay (as feed basis), according to a change-over design. Wild does dry matter (DM) intake per kg live weight (BW) was 55% higher (p < .001) than the intake of the D ones (58 g vs. 37 g DM per kg BW respectively). However, no difference (p > .05) was found when intake was expressed per kg^0.75 BW (ca. 56 g DM) and tended to be higher (p = .07) in D does when expressed per kg^0.67 BW (62 g vs. 55 g DM). Domestic does showed a higher (p < .05) DM, organic matter, crude energy and neutral detergent fibre digestibility (3; 2; 3; 3 percentage points respectively) than W does. The amount of nutrients and energy digested by D does was lower per kg BW (p < .001), similar per kg^0.75 BW (p > .05) and tended to be higher per kg^0.67 BW (p < .1) than in W does. The diet content of alfalfa did not affect (p > .05) the feed intake nor the diet digestibility. This study suggests that W rabbits exhibit a higher intake per kg BW and a lower digestibility than their D counterparts, which results in similar digestible nutrient and energy intake per kg BW powered to 0.75. The nutritive value of dehydrated alfalfa for rabbits, evaluated through intake and digestibility, seems to be equivalent to their base diets (forage plus concentrate).

Effect of inclusion of sunflower hulls in the diet on performance, disaccharidase activity in the small intestine and caecal traits of growing rabbits

A basal diet was formulated to meet the nutrient requirements of growing rabbits. Another diet was formulated by substituting 152 g/kg of the basal diet with sunflower hulls (SH diet). One hundred and sixty-eight weaned 30-day-old rabbits were given these diets and finishing performance was recorded. Eighty animals were used to study the effect of SH inclusion on caecal fermentation traits at two ages (5 and 35 days after weaning) and disaccharidase activity in the small intestine at 35 days after weaning. Inclusion of SH in the diet reduced growth rate by proportionately 0·056 in the first 2 weeks after weaning (P 0 ×001), but had no effect from 14 to 65 days after weaning. Accordingly, daily gain was lower by a factor of 0·035 over the whole finishing period (P 0×01). There was no effect of treatment on food intake during the 14 days after weaning, but SH inclusion tended to increase it from this time onwards ( +0·026; P = 0 ×06) and over the whole finishing period ( + 0·018; P = 0 ×09). This effect was parallel to a 0·09 proportional decrease in the weight of caecal contents (P 0 ×01) observed in animals of 2 kg live weight. Food efficiency was lower by a factor of 0·05 (P 0×001) in all the periods considered when SH was included in the diet. Mortality rate (6%) was not affected by treatment nor was caecal pH or caecal concentrations of volatile fatty acids and ammonia nitrogen either at 5 days (5×75, 72×7 mmol/l and 16×6 mmol/l, respectively) or at 35 days after weaning (5×70, 74×3 mmol/l and 9 ×7 5 mmol/l, respectively). Inclusion of SH increased sucrase specific activity at the ileum by a factor of 0·47 (P 0×01) but had no effect on maltase specific activity at the jejunum or ileum or on sucrase specific activity at the jejunum. In conclusion, SH included at moderate levels (150 g/kg) in the diet reduced accumulation of digesta in the caecum, which increased voluntary food intake but impaired growth rate and food efficiency. Inclusion of SH did not affect caecal fermentation or mortality.

The effect of the quality of dietary lignocellulose on digestion, zootechnical performance and health of the growing rabbit

The aim of this study was to evaluate the performance and digestive response of the growing rabbit according to a change in the nature of the lignocellulose (ADF), without a change in the ADF level. Three diets with a linearly decreasing lignin/cellulose ratio (ADL/cellulose = 0·8; 0·4; 0·2; respectively LC8, LC4, LC2) were given to a total of 162 rabbits per diet, from weaning till slaughter weight. A reduction of the ADL/cellulose ratio led to a lower food intake (LC8 v LC2: -11%), associated with a lower daily weight gain (-6% for LC2). Mortality and morbidity rate was significantly greater (+50%) for LC2 and LC4 diets compared with the LC8. Thus, the health risk index (morbidity + mortality) increased by 20 units for LC4 and LC2 compared with LC8 diet. In parallel, rate of passage was slower (mean retention time 4·5 h greater,P= 0045) with LC4 and LC2 diets. Dry-matter digestibility was slightly affected, whereas protein digestion was favoured with low ADL/cellulose ratio. It is recommended that a minimum lignin supply (about 6 g/day) is adopted as well as a minimum dietary lignocellulose to ensure growth performance and health of the growing rabbit.

Nutritive value of co-products derived from olivecake in rabbit feeding

<p>Olive cake is one of the main agro-industrial co-products in the Mediterranean area of Spain, with high availability almost all year round. In addition, most of the product is dehydrated, which increases its interest in monogastric species such as rabbits. Nineteen samples from various Spanish oil mills using different processing methods were analysed for their chemical composition and in vitro digestibility. The average composition was [in dry matter (DM) basis]: ash (9.64%), neutral detergent fibre (52.0%), acid detergent fibre (36.8%), acid detergent lignin (19.1%), crude protein (CP) (11.3%), insoluble neutral (8.0%) and acid detergent crude protein (5.15%), ether extract (10.9%) and gross energy (21.9 MJ/kg). DM and CP in vitro digestibility were, on av., 53.4 and 41.4% respectively. High variability was observed among the samples for most of the traits studied. Fibrous fractions were highly correlated among them and negatively with ether extract content, whereas CP was little related to other feed components. A stepwise regression analysis allowed us to determine regression equations to predict DM and CP in vitro digestibilities from chemical composition (R2=0.80 and 0.91, respectively). As regards the current results, olive cake has potential use for rabbits as a source of insoluble fibre and lignin. Crude samples (not oil extracted) combined with sieving to retain the smaller particles have an additional interest, because of their higher energy value and significant supply of high quality fat.</p>

Reproductive and nutritional management on ovarian response and embryo quality on rabbit does

Rabbit does in modern rabbitries are under intensive reproductive rhythms. Females are high milk producers with high energetic expenses due to the extensive overlap between lactation and gestation. This situation leads to a negative energy balance with a mobilization of body fat especially in primiparous rabbit does. Poor body condition and poor health status severely affect the reproductive features (fertility rate and lifespan of the doe as well as ovarian physiology). This paper reviews some reproductive and nutritional approaches used in the last years to improve the reproductive performance of rabbit females, mainly focusing on the influence on ovarian response and embryo quality and with emphasis on epigenetic modifications in pre-implantation embryos and offspring consequences.

Follicular, oocyte and embryo features related to metabolic status in primiparous lactating does fed with high-fibre rearing diets

Fertility of primiparous lactating does in the early postpartum (pp) period is very low mainly due to pronounced deficient energy intake, influencing oocyte and embryo developmental competence. The hypothesis used in this work was that high-lignin fibre diet supplied during the rearing period could increase feed intake and, consequently, improve the reproductive physiology and metabolic status of primiparous does in the early pp period. Diets with high-lignin [HL: 15.8% dry matter (DM)] or standard-lignin content (SL: 4.9% DM) were supplied until parturition time. No diet effects in serum oestradiol, progesterone concentrations and follicle categories were found in the histological study. Metaphase II rate of in vitro-matured oocytes was significantly higher in the SL vs the HL group (p < 0.001). Cytoplasmically degenerated oocytes (in terms of abnormal distribution of cortical granules) and follicular atresia rate were significantly lower in the SL group than in the HL group (p < 0.05 and p < 0.005 respectively). In addition, HL-fed does showed lower number of viable embryos and higher rate of retarded in vivo-recovered embryos compared with the SL group (p < 0.05). Neither in vitro embryo development of viable embryos nor conception rate was significantly different between groups. Feed intake increased during the first pregnancy in the HL group (p < 0.05), but not during early lactation. Serum protein, non-esterified fatty acid and leptin concentrations, as well as estimated body composition were similar in does fed with both diets. In conclusion, the enhancement of reproductive management by using highly lignified products in rearing diets does not seem to report physiological reproductive benefits affecting oocyte maturation rate and embryo viability in primiparous lactating does.

Effect of substitution of a soybean hull and grape seed meal mixture for traditional fiber sources on digestion and performance of growing rabbits and lactating does

The aim of this work was to determine what concentration of a mixture of soybean hulls and defatted grape seed meal (SHDG) could be included in diets that meet or exceed ADL and particle size requirements for rabbits. Four isonitrogenous and isofibrous pelleted diets were formulated, with similar ADL concentration and particle size (18.3% CP, 42.6% NDF, 7.1% ADL, and 34.9% of particles larger than 0.315 mm, on a DM basis). Diets contained a constant ratio of soybean hulls:defatted grape seed meal (81:19) provided at 0, 13.3, 26.7, or 40% SHDG, which was substituted for a 35:35:30 mixture of alfalfa hay, sunflower hulls, and wheat straw. Thirty-six rabbits were used to determine nutrient digestibility and cecotrophy traits. A feeding trial was carried out using 160 weanling rabbits (30 d of age; 536 +/- 7.1 g). Milk production was measured in 56 rabbit does. Increasing concentrations of SHDG in the diet did not affect digestibilities of DM, GE, or NDF or DE that were on average 54.7, 55.2, and 21.6% and 10.2 MJ/kg of DM, respectively. Digestibility of CP decreased in diets containing 40% (P = 0.002) and 26.7% (P = 0.054) SHDG compared with diets containing a lower percent of SHDG. Daily recycling of CP through cecotrophy, an indicator of microbial protein production, was not affected by SHDG inclusion. Growing rabbits fed 40% SHDG had reduced ADFI and ADG compared with rabbits fed 26.7% SHDG or less (106 vs. 113, 111, or 111 g/d, and 35.8 vs. 37.8, 36.6, or 37.6 g/d, respectively). There was no effect on G:F from adding SHDG to the diets. In the 2-wk period after weaning, ADG decreased (P = 0.031) for rabbits fed 40% SHDG compared with rabbits fed 26.7% SHDG or less (28.4 vs. 32.2, 30.8, of 32.2 g/d), with no effect on ADFI or G:F. Type of diet did not influence mortality during the fattening period, which averaged 6.25%. Rabbit does fed 40% SHDG had reduced ADFI (411 vs. 430 g/d; P = 0.023) compared with rabbits fed 26.7% SHDG or less, with no effect (P > 0.11) on milk production, weight of the litter at 21 d and at weaning (30 d), or parturition-effective mating interval. In conclusion, SHDG can be included up to 26.7% in diets for fattening rabbits and lactating does that meet ADL and particle size requirements.