Effects of imidacloprid-contaminated feed exposure on spermatogenic cells and Leydig cells in testes of adult male rabbits (Oryctolagus cuniculus)

This research was undertaken to assess the results of repeated exposure to the insecticide; imidacloprid (IMI)-contaminated feed on testicular tissue, spermatogenic cell population, Leydig cell number, and sperm morphology in adult male rabbits (n = 24). The treatment groups received IMI (Bildor® 100 mg/L water spray on green grass)-contaminated green grass without wash (n = 8, not-washed-feed rabbit group) and after wash (n = 8, washed-feed rabbit group) once daily for two weeks on an alternate day basis. The rest of the rabbits, as control, received a normal pesticide-free standard feed. During the exposure time, there was no evident toxic symptom found on regular monitoring of IMI-treated rabbits. Histopathologically, the thickness of tunica albuginea of testes reduced significantly with loosely arranged connective tissues in IMI-treated rabbits. Within the testes, the bizarre-shaped seminiferous tubules were seen with increased lumen diameter in IMI-treated rabbits. The spermatogenic cells were disorganized and detached from the basement membrane in seminiferous tubules of IMI-exposed testes of rabbits. The spermatogenic cell population decreased significantly (P < 0.05) in IMI-treated rabbits compared to control rabbits. Leydig cell number decreased significantly (P < 0.05) in IMI-treated rabbits. A high percentage of morphologically abnormal spermatozoa was seen in IMI-treated rabbits. The degree of the histopathological changes was more prominent in the testes of IMI-exposed not-washed-feed rabbits. The results showed that insecticide-IMI has toxicological effects on testicular tissues, mainly spermatogenic and Leydig cell population of adult rabbits which may cause infertility.A short running title: Effect of imidacloprid on testicular tissue of rabbits.     

Preferential grazing of five varieties of spring barley by wild rabbits (Oryctolagus cuniculus)

Assessment of grazing damage to five varieties of spring barley (Hordeum vulgare L.) by wild rabbits in an enclosed site revealed varietal differences. The variety Atem was consistently least grazed and Triumph most grazed by rabbits. When variety effects were removed from the analysis significant negative correlations were observed between plant height and stem damage. Differences in sugar content of varieties did not fully explain varietal selection by grazing rabbits.     

Effects of oral administration of aflatoxin B1 and fumonisin B1 in rabbits (Oryctolagus cuniculus)

The effects of prolonged oral administration (21 days) of fumonisin B₁ (FB₁) and aflatoxin B₁ (AFB₁) were studied in male New Zealand rabbits by clinical, pathological, biochemical and sphingolipid analyses. Twenty-four animals were randomly divided into the following four experimental groups: (A) 0 mg FB₁ + 0 μg AFB₁/(kg body weight (bw) day) (control); (B) 0 mg FB₁ + 30 μg AFB₁/(kg bw day); (C) 1.5 mg FB₁/(kg bw day) + 30 μg AFB₁/(kg bw day); (D) 1.5 mg FB₁/(kg bw day) + 0 μg AFB₁. Animals from group B and principally from group C presented clinical signs of intoxication. Rabbits from group C presented a lower body weight gain than controls. Differences were observed between intoxicated rabbits and controls with respect to absolute and relative liver and kidney weight, hepatic function, serum urea and creatinine levels and Sa/So ratio. The most frequent hepatic and renal injuries were vacuolar degeneration of the liver and kidney as shown by the histopathological and serum biochemical results. Combined administration of AFB₁ and FB₁ resulted in synergistic toxic effects both in the liver and in the kidney, but hepatic injuries were more marked.     

Modeling the distribution of wild rabbits (Oryctolagus cuniculus) on a Mediterranean island

The European rabbit (Oryctolagus cuniculus) is a widely distributed mammal with an often contradictory ecological role, imposing the need for population management. Sound management requires an in-depth understanding of the complex species–habitat relationships. In this study, CART analysis was employed to identify the most important environmental and anthropogenic factors affecting the spatial distribution of wild rabbit on Lemnos Island, northeastern Aegean Sea in Greece. On Lemnos, this species is considered an agricultural pest due to its overabundance resulting from the long-term absence of viral diseases, limited predation pressure, and lack of effective management. The study was carried out during the summer of 2008 by surveying rabbit densities in 181 2 × 2-km squares. Seven environmental and 14 anthropogenic variables, measured at two spatial scales, were used as explanatory variables. Soil hardness was the most influential variable, dividing the island into two distinct areas, namely the rabbit-poor areas with hard rocky soils and the rabbit-rich areas where soft soils prevail. In the former, the presence of a sharp relief can lead to complete absence of the species, while a combination of gentle relief, low altitudes, and low presence of arable land can lead to moderate rabbit density. In the latter, human-caused disturbance can reduce the number of rabbits, while a high density of ecotones and streams and a high presence of riparian vegetation can increase population densities to its highest levels observed. Our findings can formulate a scientific basis for the development of an effective management strategy for its population control.     

The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth and yield of winter cereals

In 1986/1987 and 1987/1988 wild rabbits (Oryctolagus cuniculus) were trapped and enclosed in a 0.3 ha site in which two varieties of winter barley (Igri and Panda) and two of winter wheat (Norman and Mission) were grown in a split plot block design experiment. The level of rabbit population was varied to emulate natural variation in numbers throughout the growing season and was regulated to produce a peak density of 77 rabbits ha^-* in the first year, and 33 rabbits ha^-1! in the second year. Grazing was managed by the use of exclosure fences around plots to produce four treatment levels - protected, autumn grazed, spring grazed and totally grazed regimes. Rabbit damage was assessed using stem and leaf damage indices several times through the growth of the crops. Yields were measured in terms of head number, grain weight and total yield. There was no evidence of varietal preference among the four cereal varieties on the basis of damage assessments. In the first year the totally grazed treatment led to an increase in the number of unripe heads present at harvest which would indicate a delayed harvest date in a field crop. Winter wheat showed a trend towards higher yield loss in spring-damaged plots, possibly linked to the time of tillering in this crop. Yield losses overall were highest in those plots grazed in either the autumn or throughout the entire season. The level of peak rabbit population did not appear to influence the degree of loss in either year. The results indicate that there may be a threshold of rabbit damage early in the growth of the crop which contributes most to the yield loss. This emphasises the importance of protecting a winter cereal crop at its establishment phase.     

The effect of environmental enrichment on the behaviour of caged rabbits (Oryctolagus cuniculus)

Behaviour and use of the cage area were studied in 96 rabbits (Oryctolagus cuniculus) kept in an enriched cage system - with access to shelter and raised height at the back of the cage - and in a conventional cage system to estimate the effects of the environmental enrichment on the rabbits' welfare. The rabbits' behaviour and placement in the cage were observed, using continuous video recording through 24 h and direct scan sampling during the daytime. In addition, an open-field test was carried out with each rabbit, and after every single test, the rabbits' timidity of being captured was recorded. Rabbits kept in the conventional cage system, especially the females, showed more restlessness, excessive grooming, bar-gnawing and timidity than rabbits kept in the enriched cage system. This indicates increased stress in the rabbits kept in the conventional cage system. All the rabbits performed most of the active behavioural elements in the daytime and were resting mostly at night that shows that the rabbits in both cage systems were adapted to the daily activity in the animal unit; the enrichment had no effect on the daytime activity.Only a few rabbits, particularly the females, used the box as a shelter or resting-place. On the other hand, they more often used the roof of the box as a look-out or resting-place. Furthermore, the rabbits' behaviour showed that they utilised the raised height in the enriched cage system.These results indicate that rabbits kept in an enriched cage system, particularly the females, had better welfare than rabbits kept in a conventional cage system because they had access to shelter and a better chance of interacting with the environment.     

Hematology and serum chemistry values of adult, pregnant and newborn New Zealand rabbits (Oryctolagus cuniculus)

Hematological and serum chemistry values were determined in adult female and pregnant New Zealand rabbits (Oryctolagus cuniculus) and their newborn at delivery. No significant difference was found between adult and pregnant hematological profiles. In the newborn, RBC were significantly lower and WBC, MCV and MCH higher than in their mother and adults. A characteristic protein profile was observed for the serum of each animal group, as well as for amniotic fluid. Lipoprotein pattern of the newborn was close to that of the dam, which differed from the adult female rabbit profile. The serum biochemical patterns are close to those of humans, suggesting that the New Zealand rabbit could be a reliable animal model for studies in the perinatal field involving monitoring of selected variables.     

The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth, botanical composition and yield of a ryegrass re-seed

A perennial ryegrass sward was established in the autumn of 1989 in an enclosed 0.3 ha site and was exposed to captive wild rabbit (Oryctolagus cuniculus) grazing. Rabbit numbers were varied from 16 rabbits ha^-1 in winter to 55 rabbits ha^-1 corresponding to natural fluctuations in the field. The original sward was grown for three seasons (1989/1990 to 1990/1991) and a range of grazing regimes imposed. In 1989/1990 four grazing regimes were arranged in a replicated split block design in the experimental area. These were ungrazed, winter grazed, spring grazed and totally grazed. In the second year of the experiment all plots were exposed to grazing with the exception of the originally protected plots. This was to examine the effects of longer-term grazing damage on a ryegrass sward. In the final year half of all treatments were protected to study recovery of a sward which had been damaged previously. The remainder of the plots were exposed to grazing. Three cuts were harvested in each year and the productivity assessed in terms of yield and botanical composition. There was a significant reduction in ryegrass proportion in grazed swards following the first winter of grazing, while clover, other grasses and weeds were enhanced. The promotion of clover content in grazed swards was a feature throughout the 3 yr of the study. In the second year, protection of grazed swards led to a restoration of yields, although the botanical composition remained altered. The exposure of previously ungrazed plots in the final year of the experiment showed that these swards were particularly attractive to rabbits and they suffered the greatest yield losses relative to the protected plots at the first cut in 1991. In this year dry weather conditions were experienced following the first cut and demonstrated that yield losses are exacerbated when rabbit grazing is compounded with adverse growing conditions. The results overall indicate that protection of ryegrass swards at the establishment phase is important, but that a degree of recovery is possible by providing protection at a later stage, although the ryegrass component is still impaired in swards which suffer early damage.     

Ectoparasites of wild rabbits (Oryctolagus cuniculus) from the Juan Fernández archipelago

Cheyletiella parasitovorax, Haemodipsus sp. and Listrophorus sp. are described in 137 rabbits from Juan Fernández Islands examined during 1989. The occurrence of Haemodipsus sp. and Listrophorus sp. represents two new parasite records for Chile.     

The effect of single and concomitant pathogen infections on condition and fecundity of the wild rabbit (Oryctolagus cuniculus)

We assessed the effect of two pathogens (myxoma virus and Eimeria stiedae) and five macroparasites (gastrointestinal helminth species) of the wild rabbit (Oryctolagus cuniculus) upon total host body mass and abdominal fat level. Additionally, we assessed the effects of these organisms on the number of foetuses in adult females during the peak breeding period. Both mass of abdominal fat and total body mass of the rabbit were negatively associated with myxoma virus infection and increasing helminth species richness. Total body mass was also negatively associated with the protozoan parasite E. steidae. No relationship was found between any of the parasites/pathogens and the number of foetuses in adult females, although only relatively small sample sizes were available for this section of the analysis. Increasing host body mass was positively associated with number of foetuses and we propose that mass reduction caused by the pathogen and parasite species could also have the consequence of reducing foetal number.     

Haematological changes in rabbits (Oryctolagus cuniculus f. domesticus) in the course of pregnancy

The analysis of haematological parameters is an important element of the assessment of the physiological condition of animals. Haematological parameters may change both under the influence of various external factors, and in the course of normal pregnancy, which has been found in various species of mammals, including rabbits. Our study showed statistically significant (p<0.05) changes in basic haematological parameters: RBC (decrease; 5.87±0.48 at day 15 vs. 5.42±0.32 T/L at day 26), MCH (increase; 1.35±0.04 before matching vs. 1.41±0.03 fmol at day 26), RDW (decrease; 15.77±1.80 at day 15 vs. 14.27±1.57% at day 26) MPV (increase; 5.17±0.31 at day 15 vs. 5.92±0.70 fL at day 26), WBC (decrease; 8.60±2.57 at day 15 vs. 4.94±0.88 G/L at day 26) and PLT (decrease; 398.17±91.67 before matching vs. 271.67±61.72 G/L at day 26) in Termond White rabbits and RBC (decrease; 6.18±0.68 before matching vs. 5.68±0.54 T/L at day 26), Hb (decrease; 8.00±0.90 before matching vs. 7.32±0.71 mmol/L at day 26), MCH (decrease; 1.32±0.05 at day 15 vs. 1.29±0.04 fmol at day 26) and WBC (decrease; 9.62±1.81 before matching vs. 5.85±2.23 G/L at day 26 as well as 9.58±2.35 at day 15 vs. 5.85±2.23 G/L at day 26) in Popielno White rabbits. Moreover, in the Popielno White rabbits we recorded a significant (p<0.05) decrease in the percentage of irregular erythrocytes at the end of pregnancy (11.00±10.02 at day 15 vs. 3.00±4.94 at day 26). The changes appear to be physiological but should be considered in studies using rabbits as model organisms.     

Fine-scale genetic structuring in a natural population of European wild rabbits (Oryctolagus cuniculus)

The genetic structure of a free-living tagged population of European wild rabbits (Oryctolagus cuniculus) was investigated for two consecutive years (1990 and 1991) using 10 polymorphic microsatellite loci. A specific social behaviour, the formation of stable breeding groups, influenced the genetic structure of the population. These breeding groups were shown to constitute genetically differentiated units with low levels of gene flow between them. The average relatedness among members of a social group was higher than within the population as a whole. As a result of female philopatry coupled with male-biased natal dispersal, the relatedness of females was higher than that of males, both within social groups and in the whole population. Furthermore, the average relatedness of females within groups was twice the relatedness of females between groups. This study reveals marked fine-scale, intrapopulation genetic structure, which is attributable to the social behaviour of the European wild rabbit.     

Seroepidemiology of rabbit haemorrhagic disease (RHD) in wild rabbits (Oryctolagus cuniculus) in the United Kingdom

An extensive collection of blood samples from adult wild rabbits, from areas where Rabbit Haemorrhagic Disease (RHD) had not been recorded, was obtained from sites across the U.K. and parts of Eire over the winter of 1994/95. Sera from 946 animals were examined for antibodies to RHD. Antibody was found in all populations, varying between 20 and 100% depending on locality, and overall 64% of rabbits were seropositive in midwinter, supporting the view that non-pathogenic RHD or RHD-like caliciviruses, which are not producing clinical disease, circulate within rabbit populations. The serological response to these agents appears to confer significant immunity on rabbits subsequently exposed to the virulent RHD virus, so the disease will not be as devastating as myxomatosis was in the early 1950s (99% mortality) but at least one-third of the c. 40 million rabbits in the U.K. are susceptible.