World Rabbit Science

Association analysis of nucleotide polymorphisms in growth hormone (GH) and its receptor (GHR) with body weight in Californian rabbits

2021-11-18T15:51:17+01:00

The objective of the present study was to evaluate the influence of the genotypes of two single nucleotide polymorphisms (SNPs) – c.78C>T located in the growth hormone gene (GH) and c.106C>G in the growth hormone receptor gene (GHR) on individual body weight (IBW) during the growing period at 35, 70 and 90 d of age on a total of 107 weaned Californian breed rabbits. The restriction fragments obtained revealed that 74.8% of the rabbits carrying c.78C>T SNP and 52.3% of the rabbits carrying c.106C>G SNP were heterozygous, which indicated a moderate level of genetic diversity in this Californian population. Association analysis based on a single-gene approach revealed that c.78C>T polymorphism in the GH gene had a significant effect (P<0.05) on the weight at 70 and 90 d of age. The highest IBW (2530.4±66.6 g) was observed in rabbits carrying the c.78C>T TT genotype, and detected individuals were significantly affected by the dominance effect. Significant differences were observed between individuals with homozygous c.106C>G CC genotype and those with heterozygous CG genotype. The highest IBW (2462.0±198.3 g) was observed in rabbits carrying the c.106C>G CC genotype and detected individuals were significantly affected by the additive effect. A total of nine combined genotypes of c.78C>T and c.106C>G SNPs was found in the study, of which only four major groups (CT/CC, CC/CG, CT/CG, and CT/GG) were concerned in the diplotype analysis. Significant differences were observed between individuals with CT/CC and CC/CG genotype combinations, and between those with the CC/CG and CT/GG diplotypes. However, the highest IBW at 90 d of age (2447.2±213.8 g) was observed in rabbits carrying the CT/CC genotype combinations. The highest coefficient of determination found for individual body weight at 90 d of age (R2=10.8%) indicated a high effect of genotype combinations. In conclusion, the results obtained suggested that c.78C>T of GH gene and c.106C>G of GHR gene could be useful candidate genes to improve growth performance in Californian rabbits with potential application in rabbit breeding programmes.

Challenges in rabbit doe feeding, including the young doe

2022-02-17T14:40:56+01:00

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.

Performance, haemato-biochemical and reproductive potential indices of New Zealand White and Dutch Belted rabbit bucks fed diets containing monosodium glutamate

2021-11-16T11:41:31+01:00

The study aimed to assess the growth performance, haematology, serum biochemistry, gonadal and extragonadal sperm reserves of two breeds of rabbit bucks fed dietary monosodium glutamate (MSG) at varying inclusion levels (0.00, 0.25, 0.50 and 0.75 g/kg diet). A total of 320 sexually mature New Zealand White Bucks and Dutch Belted Bucks aged 8 to 10 mo with average weight ranging from 1.34 to 1.96 kg were used for the study, which lasted 8 wk. The bucks were weighed and distributed to the four treatment diets. Each treatment was replicated 10 times with four bucks per replicate in a 2×4 factorial experiment. At the end of the feeding trial, 2 bucks per replicate were euthanised. Blood samples were collected from the jugular veins for haematological and serum analyses and their reproductive tracts were dissected. The testes and epididymides were carefully sampled, weighed and processed. The results showed that the bucks fed the diet containing 0.25 g MSG/kg had the best (P<0.05) feed conversion ratio and daily weight gain, daily sperm production and sperm production efficiency. The inclusions of up to 0.75 g MSG/kg diet did not compromise the bucks’ health status, performance and reproductive potential, irrespective of their breeds. However, optimum performance and sperm production were recorded at 0.25 g MSG/kg diet. This study suggests that dietary MSG at 0.25 g/kg in diet can significantly improve rabbit feed palatability, thereby bringing about optimum growth performance, sperm production, and efficiency without causing any physiological imbalance ino the bucks.

Aspects of social behaviour and reproduction in the wild rabbit – Implications for rabbit breeding?

2022-02-07T17:16:18+01:00

Further knowledge on aspects of social behaviour in the wild rabbit (Oryctolagus cuniculus), including the link to reproduction, could possibly point to new ways to improve housing and breeding conditions in rabbit farming. In this review, I present some results of our long-term study on a 2-hectare field enclosure population of wild rabbits (University of Bayreuth, Germany), exploring group-level and individual-level differences in agonistic behaviour of females and their potential associations with reproductive traits, including offspring survival. The frequency of agonistic behaviour in which females were involved, increased with increasing group size, and was lower in groups with a more heterogeneous age structure. At the individual level, reproducing females were involved in more agonistic interactions when groupmates gave birth and thus built their burrows and nests at around the same time, and higher-ranking mothers were particularly aggressive when other females approached close to their nursery burrows. Associations between females’ social environment and reproduction were evident, as the numbers of litters and offspring per female were lower at higher female densities, high-ranking females produced more offspring and had a lower offspring mortality than low-ranking ones, and cases of infanticide were lower in more stable groups, which we quantified by the more heterogeneous age structure of the females’ rank hierarchy in such groups. Furthermore, perinatal offspring mortality was increased in females with a delayed burrow and nest building activity, i.e. does that dug their nursery burrow and built their nest only during the last 24 h pre-partum, possibly driven by the more unfavourable social environment experienced by such females. Most importantly, our studies highlight the importance of the presence of litter siblings in improving an individual’s social environment, which resulted in an earlier onset of breeding in such females. Higher levels of positive social interactions with litter siblings were also associated with lower stress hormone (corticosterone) levels and with a better health status in terms of lower loads with an intestinal nematode. These findings on ameliorating effects of litter sibling presence in growing rabbits as well as in reproducing females may be a promising starting point worth further exploration in the context of group housing of domestic rabbits.

What landscape aspects may have been important to Eastern cottontail (Sylvilagus spp.) game farms during the Mid-20th Century in the United States?

2021-11-30T07:53:41+01:00

The Eastern cottontail (Sylvilagus floridanus) was an iconic game species during the mid-20^thcentury in the United States. Game farms were set up to produce additional cottontail numbers for hunting purposes; however, for various reasons, many game farms were unable to propagate the necessary additional numbers of cottontails needed. The purpose of this paper is to review the landscape factors involved and offer recommendations on the importance of a landscape perspective with the use of game farms under a historical mid-20^th century perspective. The results of this paper show that areas with more regional spatial scales and more than one game farm reared more cottontails and harvested than the single county, single game farm scenarios and soil for plant growth, topography and relief, and edges and boundaries of landscapes were some of the main landscape attributes that could have been important for the historical cottontail game farms. Further research could examine the number of game farms, suggestions for plot number and size, and landscape barriers to disturbance in order to help mitigate threats to cottontail game populations.

Rabbit meat trade of major countries: regional pattern and driving forces

2021-10-28T14:45:54+02:00

In in the last 60 or so years, the global rabbit industry has been growing steadily. This paper studies the global rabbit meat trade by focusing on trade growth and regional pattern. First, rabbit meat production
and regional structure are introduced, as the basis of trade. Then, the global rabbit meat trade is studied in detail, including trade growth, regional structural changes, comparative advantages and competitiveness of major countries. Finally, a gravity model is built to test major factors affecting the rabbit meat trade and
explore the driving forces behind the trade. The data come from different channels, including the Food and Agriculture Organization of the United Nations, World Bank, the World Trade Organization and related government statistics. The results show that: (1) Over the past 60 yr, the global rabbit industry has achieved great progress. In the first half of the period, rabbit meat was mainly produced in Europe; then, rabbit meat production in Asia increased steadily and rapidly in the second half period, while European production decreased continuously. (2) The rabbit meat trade had been increasing for about 20 yr from 1961 to 1979, after which it fluctuated for another 20 yr. However, since 2001 it has been stable around an average level of 37 thousand tonnes, with only minor fluctuation. The trade pattern is currently from Asia (mainly China) and South America (mainly Argentina) to European countries. In 2018, the top 5 export destinations were Germany, Belgium, Italy, Portugal and France (3). Hungary and Argentina have been two strong competitors
in the last two decades, while Spain and Belgium are two new and promising countries in the rabbit meat trade. Now China no longer has comparative advantages in the rabbit meat trade (4). The gravity model results show that rabbit meat trade is mainly driven by demand. Countries with a high Gross Domestic Product tend to increase their imports more, but decrease their exports. Countries with higher populations export more rabbit meat but import less. Common language and contiguity of two countries have significant impacts on rabbit meat trade. Based on the above results, some suggestions and policy implications are provided. Rabbit farmers or processing companies should pay more attention to domestic consumers or neighbouring countries to survey potential markets; traders should explore more markets in order to reduce the degree of trade concentration and lower risks. Governments should popularise the nutritional knowledge of rabbit meat to encourage people (especially young people) to consume more healthy rabbit meat instead of pork, with a view to reducing obesity or other heart diseases, etc.

Production and characterization of gelatin from rabbit bone as bioplastics material by acid pre-treatment

2021-12-27T17:34:18+01:00

This study aims to find out the effect of hydrochloric acid curing concentration on the characteristics of rabbit bone gelatin and determine the level of hydrochloric acid concentration for the soaking process to produce the best characteristics of rabbit bone gelatin. The material used was 50 kg of Rex rabbit bones obtained from rabbit farms, HCl 4, 5 and 6% and distilled water. The rabbit skin was soaked in hydrochloric
acid (4, 5 and 6%) for 4 d as treatment and replicated three times. Gelatin extraction was performed three times at temperatures of 65, 75 and 85°C for 4 h each time and the results obtained were filtered through filter paper. The filtrate was concentrated at 50°C for 5 h. The concentrated filtrate was then poured into a tray before drying in an oven at 50°C until dry. Milling was carried out until it became gelatin powder. This study used a completely randomised design with a unidirectional pattern, and if there was a significant difference, continued with Duncan’s multiple range test. The results showed that the rabbit bone gelatin yield was between 6.18-8.52%, moisture 8.08-8.45%, ash content 8.15-10.93%, pH 3.85-4, protein content 57.09-62.84%, fat content 0.04-0.27%, gel strength 74.47-129.09 bloom, viscosity 3.06-4.26 cP, thick point 10-12°C, melting point 33-35°C and the molecular weights were 85, 120, and 212.5 kDa. The characteristics of rabbit bone gelatin still meet the Standar Nasional Indonesia gelatin range. Curing treatment with 6% HCl gave the best gelatin characteristics.

Viral haemorrhagic disease: RHDV type 2 ten years later

2021-10-21T08:47:48+02:00

Until the early 1980s, it was totally unknown that lagomorphs were the hosts of several caliciviruses, which were included in the genus Lagovirus by the International Committee on Taxonomy of Viruses (ICTV) in 2000. In those years, two new diseases appeared, with very similar clinical and pathological profiles and associated high mortality rates: rabbit haemorrhagic disease (RHD) in rabbits and European Brown Hare Syndrome (EBHS) in European brown hares. It took a few years to ascertain that both diseases, actually acute and fatal forms of hepatitis, were caused by two genetically related caliciviruses, but they were finally classified by ICTV into two distinct viral species on the basis of their molecular characterisation and epidemiological data: RHDV in rabbit and EBHSV in brown hare. RHD has had a devastating effect on rabbit farms, causing great economic damage, especially in China, where RHD was first noticed around 1982, and in Europe. RHD has also severely affected wild rabbit populations, whose drastic decline has caused serious ecological imbalances in territories such as Spain, where rabbits are a central link in the wildlife food chain. Since the early 1990s, with the increased availability on the market of RHDV vaccines effective in protecting rabbits from RHD, the impact of the disease on rabbit farms has been significantly reduced. In the following years, also considering that RHDV is an endemic virus that cannot be eradicated, farmers learned how to manage the continuous use of RHDV vaccine in relation to the epidemiological situation, the type of breeding farm and the costs of vaccination prophylaxis. Although precarious, management of the RHD risk for rabbit farmers reached an acceptable equilibrium, which was, however, completely upset starting from 2010 by the emergence of another lagovirus also causing RHD. The genome of the newly emerged virus shows limited differences from that of RHDV, but the phenotypic traits of the two viruses are distinctive in at least three main respects: 1) The antigenic profile of the virus (the “face” of the virus recognised by the antibodies) is largely different from that of RHDV. 2) Newborn rabbits only a couple of weeks old die of RHD when infected with the new virus, while RHDV infections run asymptomatic until 7-8 wk of age. 3) The new virus, which started in Europe, has spread over the years to several continents, affecting wild and/or domestic rabbit populations. During this worldwide distribution, the new virus infected several lagomorph species and was shown to cause RHD in most of them. Considering these marked differences and the fact that the new virus is not a variant of RHDV, we proposed the name RHDV type 2 (RHDV2). All these main distinctive traits that differentiate RHDV from RHDV2 have the following consequences in practice: 1) The antigenic difference between RHDV and RHDV2 (their ‘faces’) is so great that we need “new” specific vaccines to control RHDV2 (i.e. RHDV2 is a new serotype). 2) In the event of an RHDV2 infection in suckling rabbits, the presence of maternal antibodies to RHDV2 in the blood is the only way to prevent RHD. In contrast, newborns are naturally resistant to RHD if infected with RHDV and therefore, in terms of protection, the presence of maternal antibodies is useless. 3) When RHD outbreaks occur in territories where rabbits live in sympatry with populations of other lagomorphs, viral contamination in the environment reaches sufficiently high levels to facilitate the transmission of RHDV2 to other lagomorphs, including those with a lower susceptibility to infection than the rabbit. Taken together, these phenotypic traits characteristic of RHDV2 are the reason for its rapid spread across the territory and the concomitant disappearance of RHDV. Probably the most striking example of the epidemiological consequences related to the peculiar features of RHDV2 is its rapid spread in the USA and Mexico, where it is now practically endemic. There, despite repeated isolated outbreaks of RHD caused by RHDV from 2000 onwards in small rabbit farms, RHDV has never been able to become endemic.