In this case study, a housing system for rabbits (Oryctolagus cuniculus) was developed, complying with the new German Welfare Regulation, and evaluated on-farm with regard to the rabbits’ behaviour during four fattening periods. The housing system was characterised by the large group size of fatteners (maximum 65 animals per group, 12 animals per m2) due to the merging of six former single units for does and their litters, post-weaning. A large elevated platform, a box with a roof (small elevated platform), a tube and gnawing materials were made available per unit. The aim being to assess the suitability of the housing system for rabbits with regard to animal welfare, based on behavioural analyses. Therefore, the use of space by the rabbits (n = 247) was investigated by video analysis (instantaneous scan sampling) during daytime. Additionally, the individual behaviour of 20 focal rabbits in different locations was assessed by continuous sampling. Results showed that rabbits preferred to huddle together in the outer units in the first weeks post-weaning. The highest animal densities were found under and in front of the large and on the small platforms. The large platforms were visited increasingly from the 10th fattening day onwards. Elevated platforms supported resting and comfort behaviours. Non-elevated open-top areas enabled upright positions and locomotor behaviours. Aggression and stereotypic behaviours rarely occurred. We conclude that the housing system supported species-specific behaviour and seemed to cater for the needs of rabbits in terms of welfare. Nevertheless, further investigation is needed to ascertain the effects on animal health and performance.

The goal of this research was to study the effect of the substitution of wheat starch by potato starch (PS) on the performance, health and digestion of growing rabbits. Three experimental diets were formulated with 0%, 7% and 14% PS (PS0, PS7 and PS14, respectively) and similar starch contents (22% dry matter basis), proteins and fibre. The three diets were administered to three groups of 48 rabbits from weaning (28 days) to slaughter (70 days), and growth and health measurements were made. Another 10 rabbits per diet (30 rabbits at each age), reared under similar conditions, were slaughtered at 6 to 10 weeks of age, and the digesta were collected to analyse the caecal microbial activity (pH, volatile fatty acids (VFA) levels, fibrolytic activity) and the starch concentration in the ileal digesta. At the same ages, the whole tract digestibility coefficients were measured in 10 other rabbits for each treatment (30 rabbits). The feed intake between 28 and 42 days of age (days) increased by 11% (P < 0.05) in PS0 v. PS14. Over the whole growth period (28 to 70 days), weight gain was similar among diets (40.5 g/day), whereas the feed intake and feed conversion increased (8.5% and 5.2%, respectively; P < 0.05) with the PS14 diet. Mortality and morbidity were not affected by the diets. The starch concentration of the ileal contents increased (P < 0.01) with the addition of PS to the diet (0.39%, 0.77% and 1.08% for diets PS0, PS7 and PS14, respectively). Starch digestibility was 0.8 percentage units higher (99.8% v. 99.0%) with the PS0 diet than the PS14 diet (P = 0.04). The bacterial cellulolytic activity in the caecum tended to be higher with the PS14 diet (P = 0.07). The total VFA caecal concentration increased (P < 0.01) only in 6-week-old rabbits with PS7 compared with PS0 (54.7 v. 74.5 mmol/l). Protein digestibility and ileal starch concentration decreased (P < 0.05) with age (6 v. 10 weeks), and hemicelluloses digestibility increased (P < 0.05). At 10 weeks of age, rabbits showed a higher VFA pool (6.25 mol) and proportion of butyrate (15.9%) and a lower proportion of acetate (79.3%), ammonia level (7.5 mmol/l) and C3/C4 ratio (0.31) than at 6 weeks of age. The intake of potato starch had no effect on the performance, caecal microbial activity or digestive health of growing rabbits.

During growth (27 to 75 days of age), a total of 384 rabbits were kept in 72 individual cages, 48 bicellular cages (2 rabbits/cage) and 24 collective cages (9 rabbits/cage). To evaluate the effects of the housing system on the fear level and behavioural patterns of rabbits at the two ages (39 to 45 days and 66 to 73 days), a tonic immobility test and an open-field test were conducted and their behaviour was video recorded. In the tonic immobility test, the number of attempts to induce immobility (1.38) was lower, and the duration of immobility (47.8 s) was higher (0.05 < P < 0.01) in the rabbits housed in individual cages than in those kept in bicellular (1.72 attempts and 25.0 s of immobility) and collective cages (1.99 attempts and 25.0 s of immobility). During the open-field test, the rabbits from individual and bicellular cages showed higher latency (38.8 and 40.3 v. 27.0 s), a lower number of total (73.3 and 81.7 v. 91.9) and central displacements (3.6 and 2.8 v. 5.4) and a shorter running time (11.8 and 13.6 s v. 17.7 s) and the time biting the pen (5.5 and 9.1 s v. 28.2 s) compared with the rabbits kept in collective cages (0.05 < P < 0.001). During the 24-h video recording, the rabbits in individual and bicellular cages spent less time allogrooming (0.34% and 0.19% v. 1.44%), moving (0.74% and 0.60% v. 1.32%) and running (0.08% and 0.03% v. 0.21%) than the rabbits in the collective cages (0.01 < P < 0.001). The lowest numbers of alerts and hops were observed in the rabbits kept in bicellular cages. With increasing age, a lower number of rabbits were sensitive to the immobility test and more rabbits entered the pen spontaneously during the open-field test (P < 0.001). In conclusion, the rabbits in individual cages exhibited the highest fear level and incomplete behavioural patterns; the rabbits housed in collective cages showed the lowest fear levels and had the possibility of expressing a wider range of behaviour; and the rabbits in bicellular cages exhibited an inconsistent pattern of fear in the tonic immobility and open-field tests. Probably, these rabbits were in a less stressful condition compared with animals in individual cages because social contacts were allowed, even if freedom of movement was more limited.

The presence of the fermentable sugar d-mannitol in the diet improves nitrogen (N) utilization in rabbits. To clarify the mechanism by which d-mannitol improves N utilization, we studied the effect of d-mannitol on the fate of blood urea N in growing rabbits. Growing rabbits received a control diet or a diet containing d-mannitol, which were formulated by adding 80 g/kg glucose or d-mannitol to timothy hay. After 9 days of feeding of the experimental diets, 15N-urea was administrated intravenously under anesthesia 1 h before slaughter. The blood urea level (concentration of both urea N (43.6% of the control group (CG), P < 0.05) and 15N (95% of the CG, P < 0.05) in blood serum) was reduced in the mannitol group. The concentration and amount of N, and 15N atom % excess in the contents of the cecum and colon were higher (P < 0.05) in the rabbits fed the mannitol diet than in rabbits fed the control diet, especially in the cecum. The consumption of mannitol caused bacterial proliferation in the cecum characterized by marked short-chain fatty acid production (165% of the CG, P < 0.05), decreased cecal ammonia N (73% of the CG, P < 0.05) and elevated cecal bacterial N (150% of the CG, P < 0.05). On the other hand, addition of d-mannitol to the diet decreased N (80% of the CG, P < 0.05) and 15N (77% of the CG, P < 0.05) excretion in the urine. These results indicate that d-mannitol increases the transfer of blood urea N to the large intestine, where it is used for bacterial N synthesis.

The addition of platforms to rabbit cages increases their accessible area and provides rabbits greater freedom and mobility. Different types of platforms enable rabbits to situate themselves where they are most comfortable. The objective of this experiment was to analyse preference of growing rabbits between different areas of the pen depending on the elevated platforms’ floor-type. Pens with a basic area of 0.84 m2 were equipped with platforms of 0.42 m2. Three types of flooring of the elevated platforms were used as treatments: deep-litter floor and an open wire-net floor (Experiment 1), and a deep-litter floor and a wire-net floor with a manure tray beneath it (Experiment 2). Growing rabbits (n = 168; 42 per treatment) between the ages of 5 and 11 weeks were studied, based on 24 h video recordings from infra-red cameras (one recording per week) applying scan sampling method with a frequency of 30 min. When the platform was deep-litter, significantly (P < 0.001) more rabbits used the area under the platform (53.7% and 54.3% in Experiments 1 and 2, respectively) than stayed on the platform (16.7% and 7.6%). In treatments of wire-net platform with and without tray beneath the platform also significantly (P < 0.001) more rabbits stayed under the platform (43.7% and 34.7%, respectively) than on the platform (19.5% and 29.9%, respectively). The differences from the expected 33.3% staying on the platform or under the platform were significant at least at the level of P < 0.05. The results show that the wire-net platform with the manure tray provides the optimal environment as it leads to the rabbits spreading themselves more evenly in the pen (i.e. the platform expands available floor area) without the risk of soiling from above, and without adverse effects on heat dissipation, and with the possibility of seeking cover when desired.