World Rabbit Science

Study on novel vaccines and adjuvants for rabbit infectious diseases

2024-10-18T15:33:58+02:00

Epidemic diseases have seriously damaged the development of the global rabbit industry. Vaccination plays a vital role in improving the health and welfare of livestock and preventing animal-tohuman transmission, thereby constituting a major public health strategy. There is continued demand for effective and safe adjuvants capable of enhancing antigen-specific responses to a target pathogen of rabbits. Pathogens such as Rabbit Haemorrhagic Disease Virus type 2 (RHDV2), Pasteurella multocida and Eimeria sp. coccidia are lethal and highly contagious for rabbits worldwide. Scientists have been working on screening for immunogenic proteins and designing adjuvant systems for safer and more effective vaccines against these highly prevalent pathogens. With the rapid development of genetic engineering technology and biotechnology, recombinant vaccines, genetic engineering vector vaccines, nucleic acid vaccines and other new vaccines have gradually been developed. Novel adjuvants such as new oil adjuvants, herbal medicine adjuvants, cytokine adjuvants, nano-adjuvants and polysaccharide adjuvants have been applied in the new vaccines to enhance their immunogenicity of new vaccines. Researchers are committed to developing new vaccines with broad spectrum and high efficiency. This review will briefly overview the current research on vaccines and adjuvants against viral, bacterial and parasitic pathogens prevalent in rabbits.

Enhancing the sustainability of rabbit production from the perspective of animal genetics

2024-10-21T08:49:35+02:00

The concept of sustainability, originating from the late 1980s, emphasises the ability to maintain processes over time without compromising future generations’ needs. It encompasses social, environmental and economic dimensions, although controversies persist regarding the latter’s inclusion. In the case of rabbit production, the economic dimension is paramount to ensure the future sustainability of the sector, given the large number of threats, mainly economic, it is facing. The major challenge when considering social and environmental sustainability plans in breeding programmes is how to properly include these dimensions in the functions defining the relevance of the different traits to be considered during the development of specialised lines. Note however that the key drivers of the current economic sustainability of the sector: prolificacy, feed efficiency and some functional traits such as resilience and survivability, are also the most likely levers of the environmental and social components of sustainability. In this context, the development of specialised lines is the most valuable contribution to sustainability by animal geneticists, the maternal lines specialised in producing large amounts of healthy weaned kits and the terminal sire lines specialised in efficiently transforming feed into meat. Regarding feed efficiency, important milestones have been achieved in recent years, many of them related to the fact that kits are raised in collective cages, and under these rearing conditions, tools have been developed to measure feed intake at the individual level, as well as to explore the role that one individual imposes on their cage-mates. Despite the fact that genomic tools have been developed and used to explore the role of genomic regions of different traits of interest, this information is still far from being used in applied breeding programmes. In the near future, we could predict that breeding programmes for enhanced sustainability will still mainly rely on pedigree records and phenotypic information for prolificacy and feed efficiency; but enriching the list of available phenotypes with additional traits, most likely obtained under automatic recording systems, to explicitly account for the social and environmental sustainability plans. In this framework, omic tools will perform a valuable role for further investigation of the biological basis controlling the major drivers of rabbit production sustainability, and hopefully in the future this information could be directly incorporated into breeding programmes.

Exploring rabbit semen cryopreservation and the crucial role of cryobank: unveiling advantages and promising perspectives

2024-10-22T12:46:03+02:00

Over the years, efforts have been made to establish a reference protocol for the first Italian rabbit semen bank. Here, we will provide an overview of our group’s key discoveries, which have led us to identify an effective freezing protocol for rabbit semen. However, a drawback of our protocol involves diluting the semen with the freezing media at fixed dilution ratios, resulting in significant variability in the sperm number per straw. Addressing this limitation underscores the need to standardise the freezing protocol by investigating the effect of sperm concentrations within straws on the reproductive performances of cryopreserved rabbit semen. In this regard, in an in vivo trial, 192 multiparous receptive rabbit does were randomly assigned to six treatment groups, including a control group. The remaining groups were inseminated with doses containing 15, 25, 35, 55 and 75×10⁶ sperm, respectively. Sperm concentrations of 25, 35 and 55×10⁶/straw exhibited higher reproductive performances compared to other tested concentrations and were akin to fresh semen. Through the adoption of freezing protocols with standardised sperm concentrations, cryobanks can safely preserve rabbit population genetic resources, offering invaluable support for future breeding and research efforts.

Orally added black maca (Lepidium Meyenii Walp.) Nano-emulsion meliorates fresh semen quality, testosterone level and fertilising ability of chilled and cryopreserved rabbit buck spermatozoa

2024-12-02T11:26:47+01:00

Maca is an economic crop grown in the highlands of South America that serves as a food source and medication for humans and animals. The goal of this study was to determine the potential beneficial effects of administering the nano-emulsion of black maca (Lepidium meyenii) orally to improve fresh, chilled and frozen rabbit semen, as well as its promising effects on fertilising ability and testosterone levels. The study included forty New Zealand mature white rabbit bucks (8 to 10 mo old) and eighty non-lactating, sexually receptive New Zealand white rabbit does. Rabbit bucks were divided into a control group and treatment groups. The control group was given 0.0 mg maca (M0) nano-emulsion. Treatment groups M60, M120 and M180 were orally given 60 mg, 120 mg and 180 mg, respectively, of maca nano-emulsion. Maca was administered orally twice a week for 10 wk. Rabbit does were divided into four equal groups and prepared for insemination with chilled and frozen semen from the best concentration of the treatment (M60=980±69.65×10⁶/mL spermatozoa) and the control. Semen was collected and evaluated once weekly for 10 wk, and testosterone hormone was also analysed once at fortnightly intervals for the same period. Results revealed that maca significantly increased (P<0.05) ejaculate volume (0.41 vs. 0.56 mL for M0 vs. M60), sperm progressive motility (61.00 vs. 75.19% for M0 vs. M60), sperm count, the total number of sperm per ejaculate and testosterone levels (0.45 vs. 1.5 ng/mL for M0 vs. M60). It also improved sperm morphology compared to the control. M60 was the most effective concentration, so semen was collected from M60 rabbit bucks, chilled and frozen and used in the fertilising ability test. Finally, administering the nano-emulsion of black maca orally (60 mg/twice weekly/buck/10 wk) has been suggested for increasing rabbit buck semen quality, testosterone hormone levels and fertilising ability of chilled and cryopreserved rabbit buck spermatozoa. The pregnancy and kindling rates were 66.66 vs. 100% for M0 vs. M60 of chilled semen, as well as 33.33 vs. 83.33% for frozen/thawed sperm.

Alternative methods to animal experimentation in rabbit nutrition trials integrating the 3Rs principles

2024-10-28T14:42:57+01:00

Animal studies are essential to nutrition research, particularly in investigating the effects of dietary changes on animal growth, reproduction, health and metabolism. These studies provide quantitative data on feedstuffs’ nutritive value and animal response to diets, indispensable for building accurate nutrient databases and defining animal nutrient requirements, respectively. However, advancements in (bio)technologies have encouraged the development of non-animal alternatives in rabbit nutrition research. Moreover, Europe’s commitment to replacing animals for scientific purposes emphasises the need to regulate and harmonise animal experimentation according to the principles of the 3Rs (Replacement, Reduction and Refinement). While animal methods remain necessary in some cases, attention must be paid to their reliability and validity, alongside the adoption of alternative methods. Alternative approaches in rabbit nutrition include prediction equations to estimate the nutritional value of feedstuffs based on their chemical composition, in vitro models to simulate the digestibility and fermentability of diets and feedstuffs, and the use of near-infrared spectroscopy (NIRS) to calculate feed composition and nutritive value. Other non-animal-based approaches using mathematical modelling and cell/tissue/organ culture models are also rapidly evolving to test animal responses to dietary changes. Reduction can be achieved through extensive literature searches, careful experimental design, statistical methods and data sharing to avoid unnecessary duplication of experiments. Refinement includes appropriate housing, care and enrichment to minimise the suffering of animals used in research. Additionally, integrating precision livestock farming technology into research practices and omics tools through non-invasive procedures can also contribute to refining rabbit trials. The aim of this work was to critically review these approaches following Replacement, Reduction and Refinement principles for rabbit nutrition. We first examine already existing possibilities and practical methods and later discuss their adequacy. Recommendations for designing rabbit nutrition trials and further research needs, opportunities and challenges for the use of alternative methods that pursue any of the 3Rs will also be reviewed in the light of rabbit nutrition trials.

Nutritional evaluation of two composite linseed-based ingredients for growing rabbits

2024-07-29T14:29:48+02:00

The digestible energy and protein content of two novel linseed-based ingredients were measured in growing rabbits: a high-fat extruded linseed meal cooked (ELM) and a mixture (70:30) of high-fat linseed chaff and wheat flour (LCW). Digestible energy (DE, MJ/kg of dry matter - DM) and digestible protein (DP, g/kg DM) values were obtained from regression analysis with three dietary incorporation levels of ELM or LCW: a basal diet (0%) and two diets with 8 or 16% of ELM or LCW, respectively. The regression curves were obtained from data collected in a faecal digestibility trial (n=10 rabbits per diet, 1:1 sex ratio, 42 to 46 d old) fed at two levels of inclusion (80 or 160 g/kg DM) of each ingredient in a basal diet formulated for growing rabbits (substitution method). The regression coefficients for DE (DE=10.4+0.003×ELW) and DP (DP=145.4+0.103×ELW) obtained for the ELM were significant (P<0.001). The estimated DE and DP values for the ELM were: 13.7±0.81 MJ/kg DM and 248.6±11.4 g/kg DM. The regression coefficient for DE (DE=10.4+0.011×LCW) for the LCW was significant (P<0.001), for an estimated DE content of 20.8±0.9 MJ/kg DM. The regression coefficient for DP (DP=145.6+0.011×LCW) for the LCW was not different from zero (P=0.09), giving an estimated DP of 166.9±11.3 g/kg DM. The ELM seems to be an adequate protein source for growing rabbits. The LCW appear to be an interesting composite ingredient. It provides moderate amounts of fibre fractions in addition to energy. Moreover, both ingredients contain high levels of C18:3 omega-3 fatty acids (ELM: 34.5 and LCW: 52.9 g/kg DM). These ingredients should be included up to 10% in feed formula. Based on their characteristics, these novel ingredients may improve the feed quality of growing rabbits.

Mesobiliverdin IXα-enriched microalgal feed supplement promotes beneficial gut microbiota in rabbits

2024-07-21T23:41:56+02:00

Studies were conducted to determine if an antibiotic-free diet supplemented with mesobiliverdin IXα-enriched microalgae extract promotes beneficial gut microbiota in 4- to 6-wk-old New Zealand White rabbits. Mesobiliverdin IXα is a cytoprotective haem-derived bilin with anti-inflammatory and antioxidant properties. Rabbits given supplemented feed had body weight gains, lower serum cytokine IL-6 levels and similar blood chemistry profiles compared to rabbits provided control non-supplemented feed. Microbiota 16s genomic analyses of caecotropes revealed that supplemented feed elicited caecal microbiota relative abundance increases of genera Family_XIII_AD3011 and Papillibacter, Bacteriodes vulgatus and families Lachnospiraceae, Akkermansiaceae and Bacteriodaceae and lower abundance of genera Anaeroplasma, Monoglobus, Tyzerella, Eubacterium ventriosum group and Eubacterium rumenatium group compared to non-supplemented feed. The caecal microbiota profile of rabbits fed supplemented feed resembles that described for rabbits treated with the anti-inflammatory anthocyanin procyanidin B2 and the analgesic meloxicam and shows less resemblance to the previously reported profiles of rabbits provided feed supplemented with antibiotics.