Behaviour of growing rabbits under various housing conditions

Applied Animal Behaviour Science 111 (2008) 342–356 www.elsevier.com/locate/applanim

Behaviour of growing rabbits under various housing conditions Zolta´n Princz a, Antonella Dalle Zotte b, Istva´n Radnai a, Edit Bı´ro´-Ne´meth a, Zsolt Matics a, Zsolt Gerencse´r a, Istva´n Nagy a, Zsolt Szendro˝ a,* b

a Faculty of Animal Science, University of Kaposva´r, H-7400 Kaposva´r, Guba Sa´ndor Str. 40, Hungary Department of Animal Science, University of Padova, Agripolis, Viale dell’Universita`, 16-35020 Legnaro, Italy

Accepted 20 June 2007 Available online 1 August 2007

Abstract The aim of this research was to assess the effects of environmental variables (group size, stocking density, floor type, environmental enrichment) on behaviour – as a welfare indicator – of growing rabbits. Two experiments were carried out with Pannon White rabbits. In experiment 1, 5-week-old rabbits (n = 112) were placed in cage blocks (2 m2) with a stocking density of 16 or 12 rabbits/m2. The cages (0.5 m2) differed in the floor type (wire or plastic net) and in the presence or absence of gnawing sticks (white locust). The animals could move freely among the four cages through swing doors. Infrared video recording was performed once a week, the number of rabbits in each cage was counted every half an hour (48 times/day) during the 24 h video recording. Between ages 5 and 11 weeks the rabbits showed a preference towards the plastic net floor (16 rabbits/m2, 62.5%; 12 rabbits/m2, 76.5%; P < 0.001). Gnawing stick application significantly affected cage preference: 54.1% (16 rabbits/m2) or 53.1% (12 rabbits/m2) of the rabbits choose the enriched cages (P < 0.001). In experiment 2, the 5-week-old rabbits were placed either in cages (2 rabbits/0.12 m2, n = 72) or pens (13 rabbits/0.86 m2, n = 104) with 16 rabbits/m2. The floor types were wire or plastic net, with the presence or absence of gnawing sticks on the walls. Video recordings were made at 6.5 and 10.5 weeks of age between 11:00 a.m. and 5:00 p.m. and between 11:00 p.m. and 05:00 a.m. Compared to cages, the rabbits housed in pens spent less time with resting (58% versus 67%) and more time with locomotion (6.7% versus 3.8%) but the frequency of aggressive behaviour (measured by the number of ear lesions) was also higher (0.14% versus 0.01%). In pens the application of gnawing sticks significantly decreased the frequency of ear injuries (0.05% versus 0.22%). The floor type did not affect any behavioural pattern (eating, drinking, movement, resting, comfort, social, investigatory) significantly. The main results showed that growing rabbits have a preference for plastic net floor and cages provided with gnawing sticks.

* Corresponding author. Tel.: +36 82 505800; fax: +36 28 320175. E-mail address: [email protected] (Z. Szendro˝). 0168-1591/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2007.06.013

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The resting, locomotive and aggressive behaviour was modified by the housing system and the presence of gnawing sticks decreased the frequency of physical injuries. # 2007 Elsevier B.V. All rights reserved. Keywords: Rabbit; Behaviour; Group size; Stocking density; Floor type; Gnawing stick

1. Introduction The ancestor of the domesticated rabbit, the European wild rabbit (Oryctolagus cuniculus), is a crepuscular animal and is mainly active during the dusk, night and dawn (Jilge, 1991). During the night the European wild rabbit stays mostly outside of the rabbit hole. Being a prey-animal its chances to escape from predators is higher during the night. The domesticated rabbit shows similar behaviour if kept similarly to its ancestor. However, if the rabbits are kept in cages their behavioural patterns change considerably primarily from the viewpoint of their activity, as consequence of the limited available space (Lehmann, 1987; Drescher, 1992; Stauffacher, 1992; Morisse and Maurice, 1997; Xiccato et al., 1999; Martrenchar et al., 2001). Nowadays animal welfare raises interest world-wide. Housing the animals in large groups is believed to be one of the most important factors of well-being. Wild rabbits live in colonies including several adults and a lot of young rabbits together. In most intensive rabbit farms two or three growing rabbits are housed per cage. Searching for a better housing condition fitting the animal welfare aspects several authors compared the behaviour and production of rabbits in small cage and pens (larger groups) (Verga et al., 2006; Jordan et al., 2006; Szendro˝ and Luzi, 2006). In a preference test Matics et al. (2004) demonstrated that young (3–4-week-old) rabbits like to huddle together regardless of the cage size. Comparing the behaviour of growing rabbits in smaller and larger groups (cage versus pen) Mirabito et al. (1999) observed that rabbits in smaller groups spent more time resting but the frequency of locomotion, exploration and social behaviour were higher in pens. Similar results were found by Martrenchar et al. (2001) in respect to resting, eating and interacting socially but the locomotory and abnormal behaviours were not connected with the housing system. In larger groups (60 rabbits) more running and hopping were observed by Postollec et al. (2003) than in smaller group (6 or 10 animals). In spite of the several advantages of group housing some counter-arguments can be brought up: higher risk of infection and almost importantly the higher incidence of aggressive behaviour with the increasing age (beginning at sexual maturity at the end of growing period). Bigler and Oester (1996), Maertens and Van Herck (2000) and Princz et al. (2005a) reported higher incidence of aggressive behaviour and injuries on the rabbits in larger groups. Based on these findings Rommers and Meijerhof (1998) suggested slaughtering growing rabbits before the age of 80 days. The effect of stocking density on behaviour of growing rabbits was examined in some experiments but there was a large range of group sizes. Morisse and Maurice (1997) compared groups of 6, 7, 8 and 9 rabbits/cage (15.3, 17.8, 20.4 and 23.0 rabbits/m2) and observed that behavioural patterns of rabbits at 6 weeks were only slightly affected by stocking density. At 10 weeks of age, social interactions, feeding and locomotory behaviour were reduced while an increase in resting, comfort and investigatory behaviour were noted when the stocking density was higher than 15.3 rabbits/m2. If rabbits were housed two, three or four per cage (9.6, 14.3 or 19.2 animals/m2), the frequency of resting was lower and of hopping was higher in groups of 2 than 3 or 4 rabbits/cage because lower number of

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animals allow higher locomotor activity (Verga et al., 2004). Mormerde (1988) found that high density may be related to lower movement frequency. Ferrante et al. (1997) showed a slight effect of density (12 or 16 animals/m2, 3 rabbits/cage) on the expression of the behavioural patterns. In the study of Trocino et al. (2004) a reduction from 16 to 12 animals/m2 had only a small effect on behaviour of growing rabbits (8 animals/ cage). The experimental results indicate that 15–16 rabbits/m2 (38–40 kg/m2 at the end of growing period) may be considered the threshold for the compatible expression of behaviours of caged rabbits (Trocino et al., 2004; Verga et al., 2006). In spite of this statement more experiments are needed to examine the effect of stocking density depending on the group size. One of the main objections to the caged rabbit housing is the barren environment. To avoid this problem several enrichment forms were studied with regard to productive performance, and the behaviour and welfare of growing rabbits. One of the most common enrichments is the placement of wooden sticks of different species, size and position in the cages. There were only a few experiments when the gnawing stick had a significant effect on the behavioural patterns but some more cases the same tendency was observed (Jordan et al., 2006). Princz et al. (2005a,b) observed a decrease in aggressiveness. Jordan et al. (2003) and Luzi et al. (2003) found reduction in bar, wire or feeder biting. The frequency of self-grooming decreased whereas that of alo-grooming increased. In the experiment of Luzi et al. (2003) feeding and coecotrophy increased. Verga et al. (2004) demonstrated higher frequency of hopping and sniffing another rabbits. Some of the opposite or non-significant results could be connected with the size of group, the species of the tree, the size of the gnawing stick and its position in the cage. Most of the results indicated that the environmental enrichment with gnawing sticks allowed rabbits to perform a wider range of behaviours in the ethogram (Stauffacher, 1992; Verga, 2000; Jordan et al., 2006). The most important advantage of using wooden sticks seems to be the reduction of aggressiveness and related injuries on the bodies of the rabbits. To get more accurate information about the effectiveness of gnawing sticks on the behaviour and welfare of rabbits’ evaluation of more experiments is needed. In large rabbit farms, cages are made almost exclusively from wire net. The wire net floor is cheap, easy to clean and it also meets hygienic requirements. However, some authors consider the wire net floors unfavourable from the animal welfare viewpoint. Drescher (1992) stated that the rabbits could spend less time with resting on wire net compared to other floor types. Behavioural pattern data in the experiment of Trocino et al. (2004) demonstrated that there was no difference between floors of wire net or slats with galvanized steel bars, thus indicating a similar degree of comfort on both type of floors. Preference tests showed that more growing rabbits choose the plastic net but with the increasing age or/and weight they accept the wire net and plastic slat floor as well (Matics et al., 2003). One of the wire net alternatives is the deep litter that is often recommended for the organic production (AIAB: www.aiab.it/home/). On deep litter, the frequency of coccidiosis increased because the rabbits have a permanent connection with the litter. The rabbits consume the bedding material (Dal Bosco et al., 2002) which further increases the possibility of infection and negatively affects the rabbits’ production. Morisse et al. (1999) and Orova et al. (2004) found that under free choice the majority of the rabbits choose wire net rather than deep litter. Thus, the analysis of the effect of the floor types on the rabbits’ welfare is justified. Trocino and Xiccato (2006) noted that the information gathered so far is not sufficient to make adequate suggestions for the optimal housing conditions for growing rabbits. A similar conclusion was expressed by the EFSA (2005). In the literature the effects of group size, floor

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type and gnawing stick were mostly studied separately. In our experiment these elements of housing conditions are examined together using preference tests and time budgets. The objective of the present study was to examine the effects of group size (cage or pen), stocking density, floor type (wire or plastic net) and presence or absence of environmental enrichment (gnawing stick) on the behaviour of growing rabbits. Understanding the way housing conditions can modify the growing rabbit’s behaviour could help us to adapt the rearing environment in order to improve the animal welfare. 2. Materials and methods 2.1. Animals, environmental conditions and diets Pannon White rabbits were housed in a closed climatized rabbitry at the Kaposva´r University. The lighting period was 16L/8D. The temperature of the rabbitry was constantly 18 8C. Between the ages 5–9 and 9–11 weeks the rabbits were fed ad libitum a commercial pellet (14.5% crude protein, 17.5% crude fibre, 2.0% ether extract, 10.3 MJ DE/kg, 50 ppm tiamulin, 500 ppm oxitetracycline, 1 ppm Diclazuril; and 16.0% crude protein, 16.0% crude fibre, 3.0% ether extract and 10.6 MJ DE/kg, respectively). Water was available ad libitum from nipple drinkers. Before weaning all rabbits were kept in the cages of does on wire net floor. 2.2. Experiment 1 (preference test) Five-week-old rabbits (n = 112) were housed in cage blocks having a basic area of 2 m2 with a stocking density of 16 or 12 rabbits/m2 (2 repetitions with 32 and 24 animals, respectively). The size of each cage within a block was 0.5 m2 and animals could move freely among the four cages through swing doors. The cages only differed in the floor type (wire or plastic net) and in the presence or absence of environmental enrichment (gnawing sticks) (Fig. 1). The wire net floor made from galvanized wire (2 mm in diameter) with

Fig. 1. Design of block with four cages for preference test (experiment 1).

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grid size of 10 mm  50 mm, the width of the plastic net element was 4 mm and the parallelogram shaped holes were 15 mm  25 mm, in size. The 25 cm long gnawing sticks were made from fresh barked white locust (Robinia pseudoacacia) which, after barking, were 3 cm in diameter. The gnawing sticks were placed horizontally 15 cm above the floor on the wall of the adjacent cage-blocks. A 24 h video recording was performed once a week using infrared cameras. On the days of recording nobody was allowed to enter the rabbitry. Using the recordings, the number of rabbits in each cage (within the cage blocks) was counted using a scan sampling method with a frequency of 30 min (48 times a day). The feed consumption of the four cages in a block was measured weekly. The duration of the trial was 6 weeks (i.e. between the ages of 5–11 weeks). 2.3. Experiment 2 (behavioural patterns) The rabbits were housed in either cages (n = 72; 2 rabbits/0.122 m2) or pens (n = 104; 13 rabbits/ 0.86 m2) using the same stocking density (16 rabbits/m2). In every second cage and pen the floor was wire or plastic net (structure of experiment 2 is given in Fig. 2). The parameters of the plastic and wire net were the same as described in experiment 1. Every second cage and pen (with wire or plastic net floor) was enriched with gnawing sticks made from fresh barked white locust. The length and diameter of the gnawing sticks that were placed to the cages were 10 and 3 cm, respectively. Because a larger number of rabbits were housed in the pens (compared to cages) the length of the gnawing sticks in the pens was 33 cm. Using infrared cameras 24 h video recordings were performed at the ages of 6.5 and 10.5 weeks. On the days of recording nobody entered the rabbitry avoiding any disturbance to the rabbits’ behaviour. Recordings were made during the middle parts of the dark and light periods (11:00 a.m.–5:00 p.m., resting period; 11:00 p.m.–05:00 a.m., active period) and were evaluated by recording the behavioural patterns of the rabbits with a frequency of 5 min using scan sampling methods. The examined period of the day was chosen on the basis of our former experiment representing the period of resting and active behaviour (Princz et al., 2005b). The behavioural patterns and their definitions are summarized in Table 1. The productive performances were also examined but the results will be published separately. 2.4. Statistical analysis The rabbits’ presence (in frequency, %) in the various cages and the behaviour frequencies were evaluated by performing an analysis of variance with multiple factors. The feed consumption of the cages was analyzed by one-factor analysis of variance. Statistical analysis was performed by means of the SPSS 11.5 software package. The ANOVA model included the following effects: Experiment 1 : Y i j ¼ m þ Sdi þ Ft j þ Gsk þ ðSd  Fti j Þ þ ðSd  Gsik Þ þ ðFt  Gs jk Þ þ ei jk

Fig. 2. Design of experiment 2 (n = number of rabbits).

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Table 1 Definition of behavioural patterns according to Gunn and Morton (1995) and Morisse and Maurice (1996) Behavioural patterns

Definition

Eat Drink Resting Locomotory behaviours Comfort behaviours

Consumption of feed from the feeder, gnawing the pellet Drinking water from nipple drinkers Sleeping, lying at any position (unsleeping, stretched), sitting Any voluntary change of position (treading, running, hopping, prancing) Any behaviour form connected with the own body of the animal (washing, licking, starching) The behaviour forms described at the comfort behaviours conducted on other rabbits (marking each other with the chin) Behaviour forms connected to the cage or to its equipments (rubbing, licking, gnawing, smelling, marking with the chin) Biting, picking, scraping, chasing other rabbits, fighting

Social and marking behaviours Investigatory behaviours Agonistic behaviours

where m is the general mean, Sdi the effect of the stocking density (i = 1–2), Ftj the effect of the floor type (j = 1–2), Gsk the effect of the gnawing stick (k = 1–2) and eijk is the random error. Experiment 2 : Y i j ¼ m þ Gi þ Ft j þ Gsk þ ðG  Fti j Þ þ ðG  Gsik Þ þ ðFt  Gs jk Þ þ ei jk where m is the general mean, Gi the effect of the group size (i = 1–2), Ftj the effect of the floor type (j = 1–2), Gsk the effect of the gnawing stick (k = 1–2) and eijk is the random error.

3. Results 3.1. Preference test (experiment 1) 3.1.1. Floor type The results connected with the preference of the growing rabbits between the different floor types are presented in Tables 2 and 3. Throughout the entire rearing period the rabbits showed preference towards plastic net floor in both stocking densities (Table 2). Nevertheless, increasing the stocking density resulted in an increased proportion of rabbits found on the wire net floor (62.5% versus 76.5%, P < 0.001). With increasing age, the rabbits’ preference towards wire net floor increased. In the group with higher stocking density (16 rabbits/m2) the proportions of rabbits that preferred plastic net floor decreased from 77.1 to 55.2%, while in the other group (12 rabbits/m2) it decreased from 85.8 to Table 2 Rabbits’ choice (frequencies, %) between floor types, at the stocking density of 16 and 12 rabbits/m2 and in the age range of 5–11 weeks (experiment 1) Age (weeks)

16 rabbits/m2

12 rabbits/m2

Wire net

Plastic net

S.E.

P-value

Wire net

Plastic net

S.E.

P-value

5.5 6.5 7.5 8.5 9.5 10.5

22.9 33.9 30.8 45.2 47.4 44.8

77.1 66.1 69.2 54.8 52.6 55.2

1.94 1.11 1.23 0.56 0.49 0.82

<0.001 <0.001 <0.001 <0.001 0.001 <0.001

14.2 15.2 22.7 28.0 29.5 31.3

85.8 84.8 77.3 72.0 70.5 68.7

2.28 2.32 1.84 1.57 1.36 1.29

<0.001 <0.001 <0.001 <0.001 <0.001 <0.001

Total

37.5

62.5

0.46

<0.001

23.5

76.5

0.74

<0.001

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Table 3 Rabbits’ choice (frequencies, %) between floor types, at the stocking density of 16 and 12 rabbits/m2 and depending on the part of the day (experiment 1) 16 rabbits/m2

Part of the day

11:00 05:00 11:00 05:00

p.m.–05:00 a.m.; active period a.m.–10:30 a.m. a.m.–05:00 p.m.; resting period p.m.–10:30 p.m.

12 rabbits/m2

Wire net

Plastic net

S.E.

P-value

Wire net

Plastic net

S.E.

P-value

37.1a 38.8a 36.5a 37.8a

62.9b 61.2b 63.5b 62.2b

1.05 0.90 0.88 0.86

<0.001 <0.001 <0.001 <0.001

23.7aY 27.4a 17.0aX 25.8a

76.3bX 72.6bX 83.0bY 74.2bX

1.49 1.42 1.65 1.38

<0.001 <0.001 <0.001 <0.001

Means in a row with different superscripts (a, b) were significantly different (P  0.001). Means in a column with different superscripts (X, Y) were significantly different (P  0.001).

68.7%, from 5.5 to 10.5 weeks of age. Thus, the difference between the chosen floor types gradually decreased between the ages of 5.5–10.5 weeks from 54.2 to 10.4% (16 rabbits/m2) and from 71.6 to 37.4% (12 rabbits/m2), respectively. The growing rabbits more frequently chose the plastic net than the wire net both in the active (11:00 p.m.–05:00 a.m.) and resting (11:00 a.m.–05:00 p.m.) periods (Table 3). In the rabbit group of higher stocking density (16 rabbits/m2) the choice between the floor types was independent of the light and dark periods. However, in the other group (12 rabbits/m2) higher proportion of rabbits (83.0%) were found on plastic net floor in the resting period compared to the active period (76.3%) (P < 0.01). Feed consumption was larger by 15.6% (P < 0.05) in the cages having plastic net floors than wire net floors during the period after weaning (5–7 weeks of age). On the contrary, at the ages of 8–9 weeks feed consumption in cages with wire net floors was larger by 7.2% (P < 0.05). 3.1.2. Gnawing stick The results connected to the application of gnawing sticks are provided in Tables 4 and 5. During the whole rearing period the rabbits showed preference for cages with gnawing sticks, independently of their stocking density (Table 4). The difference between the groups (8.2% versus 6.2%) was significant at both stocking densities (16 and 12 rabbits/m2). Table 4 Rabbits’ preference (frequencies, %) for the application of gnawing sticks, at 16 and 12 rabbits/m2 and in the age range of 5–11 weeks (experiment 1) Age (weeks)

16 rabbits/m2 Gnawing stick

12 rabbits/m2 P-value

No

Yes

5.5 6.5 7.5 8.5 9.5 10.5

40.0 43.7 48.9 47.0 48.6 47.2

60.0 56.3 51.1 53.0 51.4 52.8

<0.001 <0.001 0.385 0.001 0.003 0.001

Total

45.9

54.1

<0.001

S.E.

Gnawing stick

P-value

S.E.

No

Yes

1.94 1.10 1.23 0.56 0.50 0.82

52.1 44.4 44.6 47.4 46.7 46.3

47.9 55.6 55.4 52.6 53.3 53.7

0.353 0.017 0.003 0.106 0.013 0.003

2.29 2.32 1.84 1.57 1.36 1.29

0.46

46.9

53.1

<0.001

0.74

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Table 5 Rabbits’ preference (frequencies, %) for the application of gnawing sticks at 16 and 12 rabbits/m2 in relation to of the part of the day (experiment 1) Part of the day

16 rabbits/m2

12 rabbits/m2

Gnawing stick No 11:00 05:00 11:00 05:00

p.m.–05:00 a.m.; active period a.m.–10:30 a.m. a.m.–05:00 p.m.; resting period p.m.–10:30 p.m.

P-value

S.E.

Yes aX

44.0 45.4a 48.1aY 46.0a

Gnawing stick No

bY

56.0 54.6b 51.9bX 54.0b

<0.001 <0.001 0.033 <0.001

1.05 0.90 0.88 0.86

P-value

S.E.

<0.001 0.805 0.027 <0.001

1.49 1.42 1.65 1.37

Yes aX

44.1 49.7 48.2aY 45.6a

55.9bY 50.3 51.8bX 54.4b

Means in a row with different superscripts (a, b) were significantly different (P  0.05). Means in a column with different superscripts (X, Y) were significantly different (P  0.001).

The preference for cages provided with gnawing sticks was higher compared to the cages without environmental enrichment both in the active and resting periods independently of the stocking densities (Table 5). However, the part of the day significantly influenced the cage choice (with or without gnawing sticks) of the growing rabbits. The difference between the choice of cages with or without gnawing sticks was 12% in the active and 3.7% in the resting periods, independently of the stocking density. In both stocking density groups a higher proportion of rabbits (+4.1%) stayed in cages applied with gnawing sticks between 11:00 p.m. and 05:00 a.m. than between 11:00 a.m. and 05:00 p.m. Feed consumption (in percentage) was significantly higher in the cages applied with gnawing sticks between weeks 5–7 (54.5%) and 9–11 (53.0%). It was similar between the ages of 7–9 weeks. The feed consumption difference between the two cage types was 4% for the whole growing period. 3.1.3. Interactions Stocking density  floor type significantly affected (P < 0.001) the rabbits preference (see the last row of Table 2). The effects of stocking density  gnawing stick (P = 0.100) and the floor type  gnawing stick were not significant (P = 0.348). 3.2. Behavioural patterns (experiment 2) The effects of group size (cage or pen), floor type (wire or plastic net) and environmental enrichment (gnawing sticks) on the growing rabbits’ behaviour are presented in Table 6. Housing of growing rabbits in cages or in pens affected the majority of the behavioural patterns. In larger groups (pen) the rabbits spent less time resting and more time with various forms of movements. In the pens the proportion of time spent eating and drinking also increased. The rabbits spent more time investigating the pen and each other and the occurrence of aggressive behaviour increased. The floor type (plastic or wire net) did not affect any behaviour form. The environmental enrichment significantly affected only some behaviour patterns of the growing rabbits. In cages and pens provided with gnawing sticks the rabbits spent more time with movement than in the cages and pens without environmental enrichment. The gnawing stick application significantly increased the comfort behaviour and decreased the aggressive behaviour. The aggressive behaviour of the rabbits kept in pens significantly reduced with gnawing stick application. In cages, the environmental enrichment did not decrease the

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Table 6 Effects of group size, floor type and environmental enrichment on the growing rabbits’ behaviour (experiment 2) Behavioural patterns (%)

Eating Drinking Resting Movement Comfort behaviours Social behaviours Investigatory behaviours Aggressive behaviour

Group size Cage

Pen

9.49 1.55 66.9 3.79 14.9 1.15 2.21 0.01

10.5 2.10 58.0 6.71 14.6 4.38 3.53 0.14

P-value

0.012 <0.001 <0.001 <0.001 0.525 <0.001 <0.001 0.004

Floor type Wire net

Plastic net

10.1 1.88 61.0 5.82 14.7 3.20 3.16 0.12

10.5 2.00 61.4 5.39 14.0 3.37 2.98 0.16

P-value

9.88 1.84 60.5 6.09 15.4 3.23 3.20 0.04

Gnawing stick No

Yes

10.5 2.00 61.4 5.39 14.0 3.37 2.98 0.16

9.88 1.84 60.5 6.09 15.4 3.23 3.20 0.04

P-value

S.E.

0.144 0.305 0.304 0.007 0.014 0.324 0.462 0.020

0.21 0.10 0.53 0.19 0.25 0.15 0.12 0.02

aggressive behaviour significantly although its frequency was already very low without gnawing stick application (Fig. 3). With the increasing age the rabbits spent more time resting and less time eating, drinking, moving, comfort, social and investigatory behaviours (Table 7). By the time they reached 10.5 weeks of age the frequency of aggressive behaviour increased. The rabbits’ behaviour was significantly affected by the part of the day; 30.7% higher resting was recorded between 11:00 a.m. and 05:00 p.m. (resting period in rabbits). The other behavioural patterns showed higher frequency in the active period (11:00 p.m.–05:00 a.m.). Eating, drinking, moving, comfort, social and investigatory behaviours were 2.4, 3.4, 4.7, 1.4, 4.4 and 2.8 times higher, respectively, in the active than in the resting period. Aggressive behaviour was observed only during the active period (11:00 p.m.–05:00 a.m.). 4. Discussion 4.1. Floor type The well being of the rabbits is affected by the floor type of their cage. Because the rabbits experience a permanent connection with the cage floor, it is one of the most important factors determining animal welfare (Verga et al., 2006; Szendro˝ and Luzi, 2006). Table 7 Effects of the age and the part of the day on the growing rabbits’ behaviour (experiment 2) Behavioural patterns (%)

Eating Drinking Resting Movement Comfort behaviour Social behaviour Investigatory behaviour Aggressive behaviour

Age (weeks) 6.5

10.5

12.1 2.32 53.6 7.19 17.0 4.56 3.21 0.03

9.35 1.97 65.8 4.48 12.5 2.95 2.73 0.26

P-value

<0.001 0.045 <0.001 <0.001 <0.001 <0.001 0.363 <0.001

Part of the day 11:00 p.m.–05:00 a.m. (active)

11:00 a.m.–05:00 p.m. (resting)

14.4 3.04 45.6 9.45 17.4 5.37 4.61 0.20

5.99 0.79 76.3 2.02 12.1 1.23 1.57 0.00

P-value

S.E.

<0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

0.21 0.10 0.53 0.19 0.25 0.15 0.12 0.02

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Fig. 3. Effect of group size and gnawing stick application on the frequency of aggressive behaviour. Differences marked with a, b are significantly different (P  0.05).

The results of our experiment are in agreement with Matics et al. (2003) in that growing rabbits preferred plastic net compared to wire net. Matics et al. (2003) compared wire net, plastic net, plastic slats and solid floors and found that the plastic net was chosen most frequently by the young rabbits. By the end of the growing period the frequency of rabbits on the different floor types was similar (except for the wet solid floor which was refused). The floor type choice of the growing rabbits was possibly determined by the total body weight per m2 basic area. Maertens and De Groote (1984) and Aubret and Duperray (1992) found that the production of the fattening rabbits is determined mainly by the total body weight/m2 instead of by the stocking density. This could be the reason that with increasing age (from 5.5 to 10.5 weeks) the difference between proportions of rabbits on the two floor types decreased: and in the case of 16 rabbits/m2 more rabbits stayed on wire net than with 12 rabbits/m2. These results indicate that the rabbits would rather accept the less preferable floor type than tolerate higher stocking density. According to the preference test the choice between the two floor types depends on the part of the day (activity). With the stocking density of 12 rabbits/m2, during the active period more rabbits stayed on the wire net than in the resting period. This finding shows that during resting the rabbits tolerated the floor type less than in the active period. Orova et al. (2004) examined the preference between deep litter and wire net. In their experiment 85% of rabbits choose wire net independently of their age and stocking density. Thus, it can be concluded that wire net cannot be considered as an unfavourable environment and it is not necessarily true that this floor type violates the welfare of rabbits. In the present work the proportion of time spent with resting and moving was the same with the plastic and wire net floor. Trocino et al. (2004) compared the behaviour of rabbits kept in cages of wire net and wire slat. They found that the behaviour of rabbits was not affected by the floor types and both types of floor provided appropriate places for the growing rabbits. The results, seen as a whole, strengthen the opinion that neither wire nor plastic net floor seems to affect the welfare of growing rabbits. 4.2. Gnawing stick In environments of low stimuli several forms of environmental enrichment were tested to avoid abnormal and aggressive behaviour forms. In most cases gnawing sticks were placed to the

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rabbit cages (Luzi et al., 2003; Verga et al., 2004; Princz et al., 2005a,b) and their effect on the production and behaviour of growing rabbits was monitored. Our experiment proved that rabbits spent more time in cages supplied with gnawing sticks and this finding was in accordance with the observation of Luzi et al. (2003) who concluded that the gnawing stick application had a favourable effect on the rabbits’ welfare. However, in our experiment the difference was smaller than that found for the two floor types. The part of the day significantly affected the cage choice by the rabbits as more rabbits choose the cages supplied with gnawing sticks during the active period. Based on the small difference found in this study it can be supposed that the rabbits mainly enter the cages with wooden sticks only for gnawing then they return to their original location. During the resting period only a slight difference was found in the cage choice. Similar to other studies (Verga et al., 2004), gnawing stick application affected some of the behavioural patterns. In the cages or pens enriched with gnawing sticks, the rabbits spent less time eating. The time spent resting also decreased and the proportion of locomotion and comfort behaviour increased. In accordance with the literature, the gnawing stick application decreased aggressive behaviour. Verga et al. (2004) found that in cages enriched with gnawing sticks the rabbits were more active and spent more time with investigatory behaviour and less time resting (especially with lying) and they showed lower level of aggressiveness. This finding helps to understand the effect of gnawing sticks on the aggressive and abnormal behaviours. Most authors agree that in an environment enriched with gnawing sticks the rabbits exhibit abnormal (Johnson et al., 2003; Jordan et al., 2003; Luzi et al., 2003; Verga et al., 2004) and aggressive (Princz et al., 2005a,b, 2007) behaviour forms at lower frequencies. In natural circumstances the rabbits spend most of the time with race-preserving (eating, drinking, reproduction and defence as attention) activities while under farm conditions the rabbits spend less time with these activities. During the active period the rabbits are mainly bored and if gnawing sticks are not available, they gnaw the cage, the feeder or even each other. This is confirmed by our recent results (Princz et al., 2006b) in which if the gnawing sticks were made of soft trees (linden, willow) their consumption was higher compared to hard gnawing sticks (locust) leading to the conclusion that the former can be better to use as environmental enrichment. With an adequate gnawing stick, the level of aggressive behaviour and consequently the resulting injuries can be reduced to a minimum. Results of former experiments (Jordan et al., 2003; Verga et al., 2004) were not completely concordant with the effect of gnawing sticks on the rabbits’ production. On the contrary, Princz et al. (2005a) found higher slaughter weight, and Luzi et al. (2003) observed greater average daily gain in groups of rabbits that had access to gnawing sticks. In case of free choice, as reported in the present experiment, feed consumption in cages with gnawing sticks was significantly higher between the ages of 5–7 and 9–11 weeks. The explanation for the increased consumption might be that as the rabbits entered the cages with gnawing sticks they also consumed feed in the same cages. 4.3. Group size Some authors (Dal Bosco et al., 2002) recommend rearing growing rabbits in larger groups which could be a possible alternative housing system. In this case animals move more, they can run, hop and jump (Lehmann, 1987; Maertens and van Oeckel, 2001). On the other hand the aggressive behaviour and injuries are more frequent. By using gnawing stick, the injuries can be decreased (Princz et al., 2007).

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Similarly to our results, Mirabito et al. (1999), Dal Bosco et al. (2002) and Postollec et al. (2003) observed that the rabbits kept in cages spent more time resting and less time with locomotion compared with groups of rabbits reared in pens. The lower time spent for locomotion is connected with the cage size (Drescher, 1992; Xiccato et al., 1999; Martrenchar et al., 2001). Our results related to eating and drinking do not coincide with the observations of Dal Bosco et al. (2002) who reported that the rabbits kept in cages spent more time eating and drinking. However, they monitored the rabbits’ behaviour only during the light period (in the morning and in the afternoon) while the frequency of eating and drinking is much higher in the dark (active) period (Prud’hon et al., 1975). Mirabito et al. (1999) and Dal Bosco et al. (2002) observed that the rabbits in cages showed lower frequencies of investigatory, comfort and social behaviours than in larger groups. On the contrary, according to Martrenchar et al. (2001), the occurrence of social behaviour was more frequent in smaller groups. We have not found significant effects of group size on comfort behaviours but the social and investigatory behaviours were more frequent in pens. Age affected the aggressive behaviour. In accordance with our results, most authors (Rommers and Meijerhof, 1998; Maertens and Van Herck, 2000; Princz et al., 2006a) found that with ageing, aggressive behaviour and injuries could be observed more frequently. Aggressive behaviour may have a connection with sexual maturity. Our results are in accordance with those of several authors who found that with increasing group size the aggressive behaviour also increases (Bigler and Oester, 1996; Princz et al., 2005a,b, 2006a). From the behavioural point of view Drescher and Reiter (1996) established that the group size of 16 rabbits was the most advantageous because the frequency of aggressive behaviour (and injuries) was the lowest. Martrenchar et al. (2001) found that in the cages the ear injuries were more frequent than in the pens, and related this phenomenon to the lack of available space. However, Morisse and Maurice (1997) and Rommers and Meijerhof (1998) did not detect any harmful effect of the larger group size on aggressive behaviours. Our former experiment (Princz et al., 2006a) showed that in larger groups the percentage of aggressive rabbits remains the same but the aggressive individuals can injure more animals. According to the majority of the authors, in larger groups aggressive behaviour occurs more frequently and frequency of locomotion also increases. Based on the previous findings it could be interesting to analyze whether the increased locomotion is the consequence of the attempted escape by individuals caused by aggression within the group. 4.4. Part of the day In our experiment the rabbits spent more time moving, drinking and investigating both the cage and each other during the dark (active period). Prud’hon et al. (1975) found that the major feed and water consumption by 12-week-old rabbits occurs between 09:00 p.m. and 6:00 a.m. It is important to point out that, similarly to observations made by Prud’hon et al. (1975) in our experiment the rabbitry was closed at the time of recording thus the rabbits’ behaviour could not be disturbed. The day was divided by 6 h intervals and the most characteristic active and resting periods were compared. Aggressive behaviour was seen only during the active period (11:00 p.m.–05:00 a.m.). This phenomenon can explain the peaceful cohabitation of the European wild rabbit colonies. During the day they huddle together in the rabbit hole and during this period the aggressive behaviour is not frequent. This is necessary for the peaceful cohabitation of wild rabbits. During the active

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period the rabbits stay appropriate distances from each other but, in order to obtain territory or food, conflicts can occur. Hoy and Schuh (2004) observed that when 3 does were kept in 150 m2, fighting occurred at the feeder. In the open air the rabbits have the possibility to escape. Domesticated rabbits consume the feed too quickly, they are bored and too close to each other. Thus, from the time of sexual maturity, aggressive behaviour becomes more and more frequent. The dominant individual attacks the inferior ones but they do not have the possibility to escape. Our results suggest that a gnawing stick is suitable to engage their attention. As a result of the free choice during the active period (using a stocking density of 12 rabbits/ m2) more rabbits were found on the wire net floor than during the resting period showing that if more space is needed then they will accept the less preferred floor types. However, during the resting period, when less space is required they more frequently chose the preferred plastic floor. The environmental circumstances of the previous experiments are not always specified which makes comparison of our results with those reported in the literature more difficult. Prud’hon et al. (1975) used ‘laboratory’ conditions. In our experiment, the rabbit house was closed on days of recording thus human attendance did not disturb the rabbits’ behaviour. On the other hand if the observations are carried out in an open rabbitry, the presence of the workers can modify the daily rhythm, especially that of the morning (feeding and control of the animals). 5. Conclusions The main results showed that growing rabbits have a preference for plastic net floor and cages/ pens provided with gnawing sticks. Moreover, the resting, locomotive and aggressive behaviours were modified by the housing system (cage versus pen), and the presence of gnawing sticks decreased the frequency of physical injuries. Acknowledgements We thank Prof. James I. McNitt for valuable comments and suggestions that improved the manuscript. The financial support of the GAK OMFB-01335/ALAP-00121, Hungarian-Italian Intergovern¨ veges scholarship is gratefully acknowledged. mental S&T Program (I-32/03) and the O References Aubret, J.M., Duperray, J., 1992. Effect of cage density on the performance and health of the growing rabbit. J. Appl. Rabbit Res. 15, 656–660. Bigler, L., Oester, H., 1996. Group housing for male rabbits. In: Proceedings of the 6th World Rabbit Congress, Toulouse, France, pp. 411–415. Dal Bosco, A., Castellini, C., Mugnai, C., 2002. Rearing rabbits on a wire net floor or straw litter: behaviour, growth and meat qualitative traits. Livest. Prod. Sci. 75, 149–156. Drescher, B., 1992. Housing of rabbits with respect to animal welfare. J. Appl. Rabbit Res. 15, 678–683. Drescher, B., Reiter, J., 1996. Investigations about the group size of fattening rabbits kept in the Hohenheimer group housing system on slatted plastic floor. Berliner und Mu¨nchener Tierarztliche Wochenschrift 109 (8), 304–308. EFSA (European Food and Safety Authority), 2005. Scientific Report ‘‘The Impact of the Current Housing and Husbandry Systems on the Health and Welfare of Farmed Domestic Rabbit’’, EFSA-Q-2004-023, pp. 1–137 (Annex to EFSA J. 267, 1–31). Ferrante, V., Canali, E., Mattiello, S., Verga, M., 1997. Allevamento del coniglio a terrai effetto della densita. In: Proceedings of XII Congresso Nazionale ASPA, Pisa, pp. 385–386.

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