Acta agriculturae slovenica, suplement 1(avgust 2004), 81–86. 
12th Int. Symp. “Animal Science Days”, Bled, Slovenia, Sept. 2–4, 2004. 
Original scientific article 
Izvirni znanstveni prispevek 
THE INFLUENCE OF ENVIRONMENTAL ENRICHMENT WITH DIFFERENT KIND 
OF WOOD ON CARCASS QUALITY OF INDIVIDUALLY CAGED RABBITS 
Ajda KERMAUNER a), Silvester ŽGUR b), Dušanka JORDAN c) and Ivan ŠTUHEC d) 
a) Univ. of Ljubljana, Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenija, M. Sc. 
b) Same address as a), Assist.Prof., Ph. D. 
c) Same address as a) 
d) Same address as a), Prof., Ph. D. 
ABSTRACT 
The influence of addition of different types of wooden sticks as gnawing material for 
environmental enrichment on the carcass traits was studied on 48 male New Zealand White 
rabbits of Slovenian male line SIKA. Animals were housed individually in wire cages equipped 
with feeder and nipple drinkers. Feed and water were available ad libitum, the duration of 
lighting was 12 hours. According to the type of wood placed in the cage, rabbits were equally 
allotted to four groups: control, oak, lime and Norway spruce. The experiment lasted from 38th 
day of age to 103rd day, when rabbits were slaughtered and carcass traits were measured. 
Twenty-four hours after slaughter the pH value and colour of meat were recorded. The addition 
of wooden stick to wire cages had no important influence on carcass characteristics. Among 
three enriched groups with different kind of wood only meat of rabbits with spruce stick partly 
exhibited different colour: meat from SPRUCE group had darker colour (CIE L*: 57.05) than 
from OAK (59.40) and LIME (59.71) groups and less red (a*: 3.73) and in tendency less yellow 
colour (b*: 1.10) than meat from OAK group (a*: 4.66, b* 1.96). 
Key words: rabbits / environmental enrichment / wood / carcass quality / meat quality 
VPLIV OBOGATITVE OKOLJA Z RAZLIČNIMI VRSTAMI LESA NA KLAVNO 
KAKOVOST INDIVIDUALNO UHLEVLJENIH KUNCEV 
IZVLEČEK 
Proučevali smo vpliv obogatitve okolja z letvami za glodanje iz različnih vrst lesa na klavne 
lastnosti kuncev pitancev. V poskusu je bilo 48 samcev pasme beli novozelandec slovenske 
mesne linije SIKA (očetovska linija). Živali so bile uhlevljene individualno v žične kletke, 
opremljene s krmilnikom na zalogo in kapljičnim napajalnikom. Krmo in vodo so imele na 
razpolago po volji, trajanje osvetlitve je bilo 12 ur. Glede na vrsto lesa, iz katere je bila letev, ki 
smo jo namestili v kletko, so bili kunci razporejeni v štiri enako velike skupine: kontrola, hrast, 
lipa in smreka. Poskus je trajal od 38. do 103. dne starosti, ko smo kunce zaklali in izmerili 
klavne kazalce. Štiriindvajset ur po zakolu smo merili še barvo in pH vrednost mesa. Obogatitev 
okolja na klavne kazalce ni vplivala. Med skupinami z različnimi vrstami lesa je najbolj 
odstopala barva mesa kuncev, ki so imeli letve iz smrekovega lesa: meso skupine SMREKA je 
bilo bolj temno (CIE L*: 57,05) od skupin HRAST (59,40) in LIPA (59,71), manj rdeče (a*: 
3,73) in v tendenci manj rumeno (b*: 1,10) od skupine HRAST (a*: 4,66, b* 1,96). 
Ključne besede: kunci / obogatitev okolja / les / klavna kakovost / kakovost mesa 
http://www.bfro.uni-lj.si/zoo/publikacije/zbornik/suplementi/index.htm
Acta agriculturae slovenica, suplement 1(avgust 2004). 
 
82 
INTRODUCTION 
Animals housed in intensive breeding system (wire cages) are hold in a barren environment, 
in which they are restricted to express their natural behaviour. Conventional wire cage system 
prevents rabbits to perform their natural behaviour, such as rearing up on the hind legs, digging, 
foraging and nearly all locomotors activities (Gunn and Morton, 1995). Their gnawing 
possibilities are very limited as well (Maertens and Van Oeckel, 2001). 
Rabbits need to gnaw due to continuous growth of their incisor teeth. Gnawing is also 
connected with digestive process and nervous system. It is well known that stress can influence 
the excreting of hormones and enzymes and consequently the digestive process and the 
appearance of digestive disturbances in rabbits.  
Wire cage systems can be enriched with straw or hay, grass, branches with leaves and 
gnawing sticks, which enable rabbits to perform their natural activities (Lidfors, 1997) and 
mitigate the effect of stressors (Berthelsen and Hansen, 1999). Stauffacher (1992, cited in 
Lidfors, 1997) found out that in semi-natural enclosure rabbits spent about 20 % of the time 
chewing on wood branches. He suggested that rabbits should have gnawing sticks also in their 
cages. 
There are only few studies in literature described the influence of cage or pen enrichment. 
Mirabito et al. (2000) studied the presence of a wooden stick or hay in caged rabbit fatteners and 
no deterioration of performances was observed in cages with enrichment. Maertens and Van 
Oeckel (2001) studied the addition of gnawing wooden stick in pens with 30 rabbits and they 
observed decrease of aggressiveness (fighting between rabbits). Daily weight gain and slaughter 
weight were higher in caged rabbits, while there were no differences between pen housed rabbits 
with or without the gnawing stick. Luzi et al. (2003b) found no significant effect on rabbits 
fattening traits when wooden sticks were added to the cages with 2, 3 or 4 animals per cage. 
Among carcass traits rabbits with environmental enrichment exhibited lower redness (a*) and 
higher content of water in the meat. The reduction of abnormal behaviours, increased growth and 
higher carcass weight were reported by Luzi et al. (2003a) when wooden stick was added to the 
cages with 8 fattening rabbits in semi plein air conditions. Authors stated that this improvement 
may indicate an improvement in welfare conditions in intensive rabbit breeding.  
The inclusion of sawdust in the feed of rabbits can improve digestive process and utilisation 
of other nutrients; better resistance to coccidiosis was also found (Koritnik and Banožić, 1974). 
Meat of rabbits with added sawdust had no unfavourable taste or smell. The authors recommend 
pine, fir and spruce sawdust and dissuade from oak sawdust due to its unpalatability. 
The objective of our experiment was to study the effect of addition of wooden sticks to 
individual wire cages as an environmental enrichment on carcass quality of fattening rabbits. 
Rabbits may prefer different kind of wood so we used oak, lime and Norway spruce sticks. In the 
first part of this study the behaviour and fattening traits were also observed (Jordan et al., 2004).  
MATERIAL AND METHODS 
The research took place in autumn and lasted nine weeks. 48 male New Zealand White rabbits 
of Slovenian meat line SIKA (paternal line) were weaned at 35th day of age. At the age of 38 
days animals were housed individually in wire cages, equipped with a feeder and nipple drinker. 
They were fed ad libitum with the complete feed mixture for fattening rabbits (170 g CP/kg, 140 
g CF/kg, 10.4 MJ DE/kg). The ambient temperature varied from 21 to 25 °C, relative humidity 
between 35 and 57 % and 12 hours light: 12 hours dark schedule was used. According to the type 
of wooden stick fixed horizontally in the rabbit’s cage right after the individual housing, animals 
were allotted to four groups, 12 rabbits in each. As a material for gnawing the first group 
Kermauner et al. The influence of environmental enrichment … carcass quality of individually caged rabbits. 83
received oak sticks (OAK), the second lime (LIME) and the third Norway spruce sticks 
(SPRUCE). The control group (CONTROL) was without wooden sticks.  
Animals were slaughtered at 103rd day of age and slaughter weight, warm carcass weight 
(excluding head and lower parts of legs, including liver and kidneys), weight of liver, kidneys, 
separate digestive organs (with their content) and fat on digestive tract were measured. The 
proportions (%) of liver, kidneys and separate digestive organs with respect to the slaughter 
weight were calculated. Cold carcass weight without kidneys and liver was recorded 24 h after 
slaughter. After that kidney fat was removed and meat colour and pH24 were measured on the 
cross section between last thorax and first lumbar vertebra. The observations of behaviour and 
fattening traits are described in Jordan et al. (2004). 
Statistical analysis was performed by SAS statistical package (SAS, 2001) with GLM 
procedure. Effects of mother and group as fixed effects and slaughter weight as independent 
variable were included in the model. For the analyses of proportions of internal and digestive 
organs the regression on slaughter weight was removed from the model for it was not significant. 
In this study only results for the effect of group are presented since this effect was the main 
objective of our research. 
The mortality rate was 8.3 % (4 rabbits: two in the OAK and one rabbit in the LIME and in 
the SPRUCE group), which is in intensive breeding systems within usual limits.  
RESULTS AND DISCUSSION 
There are only few carcass traits which are influenced by environmental enrichment with 
gnawing stick (Table 1). Differences between CONTROL and three enriched groups were not 
significant, what is in accordance with the results of Luzi et al. (2003b), Jordan et al. (2002) and 
Maertens and Van Oeckel (2001). On the contrary Luzi et al. (2003a) found higher slaughter, 
warm and chilled carcass weights when gnawing sticks were added to cages with 8 animals.  
 
Table 1. The influence of environmental enrichment on carcass characteristics 
 
GROUP 
CONTROL OAK LIME SPRUCE  
LSM SE LSM SE LSM SE LSM SE 
Slaughter weight (SW), g 3551.60 103.91 3368.33 113.56 3348.20 106.67 3406.97 112.22
Carcass weight, g 1911.29 26.40 1949.05 27.98 1872.72 26.41 1897.44 27.56
Dressing percentage, % 55.91ab 0.80 57.10a 0.85 54.65b 0.80 55.36ab 0.84
Chilling carcass weight, g 1779.73 27.09 1816.53 28.71 1744.72 27.1 1773.31 28.28
Drip loss, % 6.89 0.27 6.78 0.29 6.85 0.27 6.61 0.28
g 53.44 4.32 59.72 4.58 50.58 4.32 52.43 4.51Kidneys fat 
%/SW 1.63 0.13 1.72 0.15 1.39 0.14 1.49 0.14
g 91.04 3.17 93.11 3.36 93.33 3.17 85.28 3.31Liver 
%/SW 2.63 0.10 2.74 0.11 2.75 0.10 2.52 0.11
g 18.73 0.53 18.47 0.56 18.48 0.53 18.68 0.55Kidneys 
%/SW 0.54 0.02 0.55 0.02 0.55 0.02 0.56 0.02
a, b values with different superscripts differ significantly (P≤0.05) 
 
Dressing percentage was higher than established by Žarn (1997), Kermauner and Štruklec 
(1999) and Kermauner and Žgur (2002) in rabbits of SIKA male line and much lower than found 
by Dal Bosco et al. (2002), who reported 60.1 % dressing percentage (with head). 
The proportions of liver in our experiment were lower than reported by Maertens and Van 
Oeckel (2001) and also lower than in our previous experiments with SIKA male line (Kermauner 
Acta agriculturae slovenica, suplement 1(avgust 2004). 
 
84 
and Štruklec, 1999; Kermauner and Žgur, 2002); they were much lower from the results of Dal 
Bosco et al. (2002), who measured 5.29 % of liver. The proportions of kidneys were comparable 
with the results of Kermauner and Štruklec (1999) and Kermauner and Žgur (2002) for SIKA 
male line and lower than found by Dal Bosco et al. (2002). The proportion of kidneys fat was 
comparable with Luzi et al. (2003b) and lower than found by Dal Bosco et al. (2002) and 
Kermauner and Žgur (2002), although their rabbits were younger (85 and 90 days of age).  
Comparison of different types of wood used for gnawing stick shows that despite regression 
on slaughter weight rabbits from OAK group had higher dressing percentage than rabbits from 
LIME group. In SPRUCE group the weight of liver was in tendency higher than in OAK and 
LIME groups, while proportions of liver did not differ among groups. 
Enrichment of cages and different types of wooden sticks had no significant influence on 
weights and proportions of separate digestive organs.  
 
Table 2. The influence of environmental enrichment on meat characteristics 
 
GROUP 
CONTROL OAK LIME SPRUCE  
LSM SE LSM SE LSM SE LSM SE 
 pH24 5.58 0.04 5.53 0.04 5.63 0.04 5.62 0.04 
 CIE1 L* 57.76ab 0.78 59.40ac 0.85 59.71c 0.79 57.05b 0.84 
 a* 4.65a 0.37 4.66a 0.39 4.02ab 0.38 3.73b 0.39 
 b* 1.56 0.21 1.96 0.23 1.57 0.21 1.10 0.22 
a, b values with different superscripts differ significantly (P≤0.05) 
1) Difference between LIME and CONTROL is only important (P=0.0950) 
 
Enrichment of cages with wooden sticks influenced the characteristics of meat: meat from 
CONTROL group had a less pale colour than LIME group and it was redder (a*) then from 
SPRUCE group. This is in accordance with Luzi et al. (2003b), who also found higher redness of 
rabbits’ meat of in conventional pens in comparison with pens enriched with wooden sticks.  
The lightness of meat in our study is comparable then in SIKA male line (Kermauner and 
Žgur, 2002), while Dal Bosco et al. (2002) and Luzi et al. (2003b) observed darker colour of 
meat. The redness and yellowness of meat in our experiment differ from our previous studies on 
SIKA male line, where less red and more yellow colours were observed (Kermauner and Žgur, 
2002). Similarly Luzi et al. (2003b) established different colour as well (less red and yellow 
colour than in our experiment), while Dal Bosco et al. (2002) found comparable a* and b* 
values. 
pH24 value of meat was not influenced by environmental enrichment, what confirms the 
results form Luzi et al. (2003b), although they found higher pH value (about 5.80). pH24 values 
of meat in our experiment are comparable with SIKA rabbits (Kermauner and Žgur, 2002) and 
Dal Bosco et al. (2002).  
Comparison of different types of wood used for gnawing stick shows some differences in 
meat characteristics between three enriched groups: pH24 of meat from OAK group was in 
tendency lower than in LIME group. The colour of meat from SPRUCE group deviate from 
other enriched groups: it was darker than from OAK and LIME groups and less red and in 
tendency less yellow than meat from OAK group.  
In the first part of our study Jordan et al. (2004) found the highest frequency and duration of 
wood gnawing in SPRUCE group. Also the amount of gnawed material tended to be higher in 
SPRUCE group in comparison with other two enriched groups (OAK 4.39, LIME 5.12, 
SPRUCE 6.30 g, P≤0.10). We presume that intensive gnawing of spruce wood probably affect 
the colour of rabbit meat, but further studies are required to specify this effect. 
Kermauner et al. The influence of environmental enrichment … carcass quality of individually caged rabbits. 85
CONCLUSIONS 
The addition of wooden stick to wire cages had no important influence on carcass 
characteristics. Among three enriched groups with different kind of wood only meat of rabbits 
with spruce stick partly exhibited different colour: meat from SPRUCE group was darker than 
from OAK and LIME groups and less red and in tendency less yellow than meat from OAK 
group.  
ACKNOWLEDGEMENT 
This study was a part of a research project funded by research grants from Ministry of 
Education, Science and Sport of Slovenia. We would like to thank Monika Turk and Alenka 
Kočevar for their technical assistance.  
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