The aim of this study was to compare the carcass traits and meat quality of growing rabbits reared in four types of commercially available housing systems (i.e. bicellular cages, dual-purpose cages, enriched cages and elevated pens) across three production cycles covering different seasons (i.e. autumn, winter and summer) under field conditions. The rabbits originated from 12 commercial farms (three farms per housing system) located in the Northeast of Italy and were slaughtered in five commercial slaughterhouses at a slaughter age from 71 to 90 d. Twenty carcasses per farm and cycle were randomly selected at the slaughterhouse and carcass and meat quality traits were evaluated 24 h post-mortem. The heaviest carcass weights were found in rabbits reared in enriched cages, followed by those in parks, while the lightest carcasses were found in rabbits from bicellular cages. Carcass fat and longissimus lumborum proportions were higher and hind legs proportion lower in carcasses of rabbits kept in enriched cages compared to those from the other systems. Based on significant differences for meat quality traits (i.e. pH, L*, thawing losses and shear force) among housing systems, ante-mortem stress was likely lower in rabbits from enriched cages and parks than in those from bicellular and dual-purpose cages. Nevertheless, these differences were not translated into noticeable changes in meat quality because of the small variations among housing systems. Overall, the observed differences could not be strictly and exclusively related to the enclosure in which the animals were housed, but also to other production and ante-mortem factors. The rearing season significantly affected slaughter traits, with lower slaughter and carcass weights in summer compared to winter and autumn. Despite the limit in the sample size of investigated farms, this study highlighted that under field conditions the final product quality of rabbits is not clearly distinguishable based on the housing system per se. 

To explore the mechanism of the FRZB gene in hair follicle development by regulating the Wnt/β-catenin signalling pathway, Angora rabbits were selected to collect back skin samples for the experiment. The action mechanism is understood by cell culture and transfection, apoptosis and proliferation assays and TOP/FOP Flash Wnt Reporting System methods. The results showed that the interference and overexpression of the FRZB gene in rabbit dermal papilla cells indicated that overexpression could inhibit the expression of SFRP2, BMP4, and WNT2 genes (P<0.05). On the contrary, the expression of Wnt signalling pathway-related genes LEF1, CCND1, DKK1, and TCF7 was significantly up-regulated (P < 0.05). Further examination of the luciferase reporter system TOP/FOP revealed that pcDNA3.1-FRZB inhibits Wnt activity. PcDNA3.1-FRZB was found to promote the level of apoptosis in DP cells, whereas si-FRZB inhibited DP cell proliferation. Therefore, it is concluded that FRZB inhibits hair follicle development in long-haired rabbits by regulating the Wnt/β-catenin signalling pathway.

In this study, we focused on the occurrence of respiratory disorders in rabbit farms, as well as several risk factors. We based the assessment on 11 217 visits to 1288 commercial farms in Spain and Portugal from 1996 to 2020. There was a sub-set of 307 visits due to respiratory system issues on 172 farms; the main causes were high prevalence of rhinitis in does and high mortality risk in weaned rabbits. During the 25-yr observational study, we physically examined 29 000 males and 200 000 lactating does to monitor their sanitary status on 894 farms. The mean annual prevalence of clinical rhinitis (CR) and 95% binomial confidence interval (CI) in does was 19.9% (95% CI [19.7-20.1%]). We observed an improvement as prevalence of annual CR fell from 29.6% in 1996 to 15.2% in 2020. The main risk factor for rhinitis was the rabbit line, followed by gender (males become sick more than females) and age of females. The median age of farmed does was 5 parities (minimum to maximum: 1-39). The enabling risk factors were year, season (more often affected in summer) and service timing (lowest prevalence when does were served ≥32 d postpartum). In a sub-set of 208 farms, we determined the prevalence of apparent atrophic rhinitis, which was 0.04% in females and 0.11% in males. Concerning bacteriological studies with 444 samples from 153 farms, Pasteurella multocida and Staphylococcus aureus were the main agents isolated from cases of pneumonia, rhinitis and other issues. We may infer that much work is required to determine in greater detail the factors linked to the farm environment and apply this knowledge in practice.

Starter cultures can help improve the quality and safety of traditional fermented meat products. This work was conducted to evaluate the effects of the inoculum of Staphylococcus xylosus on the quality characteristics of a Sichuan cured rabbit product (Chan Si Tu). Physicochemical analyses showed that meats inoculated with S. xylosus had a significant increase in lightness, redness, cohesiveness and chewiness (P<0.05). In addition, a lower content of nitrite, diethylnitrosamine and histamine, was observed in the inoculated samples (P<0.05). The thiobarbituric acid reactive substances (TBARS) value in the S. xylosus incubation group was 0.108±0.004 mg/kg, which was significantly lower than that in the control group (P<0.01). Interestingly, a lower TBARS value was observed in the incubation samples through storage. Furthermore, solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS) analysis identified a total of 73 volatiles, and the species and abundance of theses volatile compounds were higher in the samples with added S. xylosus, and 12 with odour activity value>1 were proposed as the most odouractive compounds that enhanced the complexity of the product. Thus, inoculation with S. xylosus in the cured rabbit meat product (Chan Si Tu) can effectively enhance the product quality.

Feed efficiency is a major production trait in animal genetic breeding schemes. To further investigate the genetic control of feed efficiency in rabbits, we performed a genome-wide association study (GWAS) for growth and feed efficiency on 679 rabbits genotyped with the Affimetrix Axiom Rabbit 200K Genotyping Array. After quality control, 127 847 single-nucleotide polymorphisms (SNP) were retained for association analyses. The GWAS were performed using GEMMA software, applying a mixed univariate animal model with a linear regression on each SNP allele. The traits analysed were weight at weaning and at 63 days of age, average daily gain, total individual feed intake, feed conversion ratio and residual feed intake. No significant SNP was found for growth traits or feed intake. Fifteen genome-wide significant SNPs were detected for feed conversion ratio on OCU7, spanning from 124.8 Mbp to 126.3 Mbp, plus two isolated SNP on OCU2 (77.3 Mbp) and OCU8 (16.5 Mbp). For residual feed intake, a region on OCU18 (46.1-53.0 Mbp) was detected, which contained a putative functional candidate gene, GOT1.

The development of reproductive technologies in this species is contributing decisively to the development of rabbit farming and the preservation of genetic resources. Obtaining embryos is an essential step to both genetic diffusion and the preservation of genetic resources from genetic erosion or natural disasters. In rabbits, it is common for embryos to be recovered post-mortem after ovarian hyperstimulation with gonadotrophins, although the quality and number of embryos are variable, affecting the embryo viability and offspring rate by the donor. In vivo embryo production within a conservation programme aims not only to obtain a large number of embryos, but also that they come from a greater number of male and female origins, in order to ensure an adequate representation of the original population. This is why both the quality and quantity of embryos obtained per donor rabbit and the rate of donors with offspring after embryo cryopreservation must be considered, as well as the response of the embryos to the chemical, physical and physiological stress to which they are subjected in the rederivation process and its postnatal repercussions on those that survive. Rederived rabbits from cryopreserved and transferred embryos showed phenotypic growth changes, which calls into question the neutrality of the technique and its usefulness in those cases in which a control population is required.

In the present study, we evaluated the effect of various concentrations of date palm pollen (DPP) aqueous extract on rabbit sperm during storage at 4°C for 48 h. Semen was collected from old and young rabbit bucks using an artificial vagina and initially evaluated for sperm quality. The sperm were diluted in Tris buffer supplemented with (20, 40, 80 mg/mL) of DPP aqueous extract. The extended samples were stored at 4°C for 48 h. Sperm motility and motion kinetics were assessed after 2, 4, 24 and 48 h of storage. At each time, an aliquot was frozen for the analytical evaluation of thiobarbituric acid reactive substances (TBARS) (lipid peroxidation) and tocols (vitamin E). Proximate composition, antioxidant and sugar content were evaluated in DPP. The results showed that DPP was characterised by a high proportion of protein (27.10%) and ash (18.43%), whereas the lipid fraction was very low (0.51%) and total sugar was also high (16.25 g/100 g of fresh matter, f.m.). Regarding the antioxidants content, the sum of tocols showed a total value of 26.48 mg/g f.m. The total polyphenols content was 5.01 mg gallic acid equivalents/g f.m, and polyunsaturated fatty acids was around 30%. Date palm pollen extract had a dose-dependent effect on sperm parameters (curvilinear velocity [VCL] mainly) of old rabbit, although a null or negative effect was recorded at doses >DPP40. Conversely, in optimal conditions (i.e. young rabbit semen), the addition of pollen had no effect on sperm traits (motility and VCL). The progressive increase in DPP, despite providing sperm with an additional amount of tocols, also caused higher tocol consumption and an increase in lipid oxidation. In particular, DPP80 increased the TBARS level in sperm of both rabbit ages. The better trend was found in DPP20, where the tocol consumption figures were 10.46 % and 15.28 %, respectively, in old and young bucks, and the lipid oxidation was lower compared to the higher doses of DPP. In conclusion, the findings of this study demonstrated that supplementation of DPP extract to Tris buffer extender enhanced chilled rabbit semen traits only if administered in old rabbit semen at concentration lower than 40 mg/mL.

The commercial use of artificial insemination (AI) in rabbit farming is relatively recent, especially when compared to other species such as cattle or swine, in which AI has been used for more than 60 years. The large-scale use of AI in rabbit farming dates back to the late 80s. However, despite its short journey, it has not stopped evolving. Although there have been numerous changes, in this review article we aim to highlight two important milestones in optimisation of this technique: the introduction of biostimulation and the addition of Gonadotropin-releasing hormone (GnRH) analogues to the seminal dose to induce ovulation. In the former case, by means of different methods of biostimulation, such as feed and light flushing and/or separation of the litter in the days prior to AI, the use of hormones to synchronise heat with the moment of AI was practically eliminated. Nowadays, the possibility of using pheromones with the same objective is under research, even to increase ovulation rate or improve semen production. Although there are pheromones on the market labelled for use in other species, in the case of rabbit the knowledge of them is limited. Nevertheless, given the verified effects that pheromones produce in other animals, expectations are high. In the latter case, after several attempts by using other methods, the technique commonly used to induce ovulation was the intramuscular administration of GnRH or its synthetic analogues. However, in recent years, it has been proven that administration of GnRH through the vagina is possible, added to the seminal dose, which offers numerous advantages regarding health, animal welfare and the workforce needed. Recently, the European Medicines Agency (EMA) approved this practice, so in the near future it will probably become the most widely used method. Even so, there is still room for improvement, as the dosage of GnRH needed is higher than the one administered intramuscularly. Research on this topic allows us to predict that this problem should be solved in the coming years. Other alternatives such as the β-Nerve Growth Factor need further research to become a feasible option.

The sexual receptivity and ovulation induction of the reproductive rabbit are key points determining their success in productive life. Adequate synchronisation of the sexual receptivity methods of inseminated rabbit does unquestionably favours fertility and prolificacy outcomes. This review aims to bring together the different methods applied in synchronising primiparous rabbits and the consequences at metabolic, endocrine and ovarian levels, as well as in the embryonic, foetal and post-natal development that our research group has studied over the years. Likewise, the latest advances regarding ovulation induction in the rabbit are described, as well as the search for alternatives to the intramuscular injection of synthetic analogues of gonadotropins and seminal plasma components that could be involved in this process. Different experiments performed with a physiological basis confirm that nerve stimulation during artificial insemination or coitus is especially important in the ovulation induction reflex in rabbit females.

Artificial insemination (AI) has become a popular technique in rabbit farms worldwide. This report discusses the progress made on semen extenders used in rabbit AI, setting out the latest innovations. Fresh and frozen semen have different requirements, so the extender composition will vary depending on the type of semen used. We discuss the endocrine supplementation of extenders for ovulation induction, the use of active molecules as an alternative to conventional antibiotics and the extenders developed for rabbit sperm cryopreservation.