Acta agriculturae Slovenica, suplement 2 (september 2008), 117–122. 
 
16th Int. Symp. “Animal Science Days”, Strunjan, Slovenia, Sept. 17–19, 2008. 
  
Agris category codes: L02 COBISS Code 1.08 
THE EFFECT OF TANNINS PARTLY BOUNDED ON PROTEINS ON PRODUCTION 
AND SLAUGHTER PARAMETERS IN GROWING RABBITS 
Ajda KERMAUNER 
a) Univ. of Ljubljana, Biotechnical Fac., Dept. of Animal Science, Groblje 3, SI-1230 Domžale, Slovenia,  
e-mail: ajda.kermauner@bfro.uni-lj.si 
ABSTRACT 
Production traits of 144 rabbits (104 male and 40 female) of Slovene sire SIKA line were 
recorded from weaning (31 days of age) to slaughter (73 days). Rabbits were allotted to 5 groups 
in two trials: control, F-0.3 (added 0.3% of Famatan®), TA-0.19 (added 0.19% of TA), TA-0.25 
(added 0.25% of TA) and TA-0.5 (added 0.5% of TA). TA preparation is experimentally 
produced by Tanin Sevnica d.o.o. in extraction procedure of their commercial product 
Farmatan® (water extract from sweet chestnut (Castanea sativa Mill.) wood), where only a part 
of tannins was bounded by whey proteins. Statistical analysis was performed by SAS statistical 
package (SAS, 1999) with GLM procedure. The addition of 0.5% TA (TA-0.5) increased feed 
intake and weight gain during the most critical period (3 weeks after weaning) in comparison 
with Control group. The addition of 0.25% of TA (group TA-0.25) increased weight gain and 
live weight of rabbits during the entire trial in comparison with Control group. There were no 
differences between groups in feed intake and FCR during the entire trial. Rabbits from all 
groups with added TA (TA-0.19, TA-0.25 and TA-0.5) had significantly higher proportion of 
liver than Control rabbits. This can indicate higher burdening of liver where TA was added, but 
this influence has to be examined on greater number of experimental animals. The influence of 
added tannins (Farmatan® or TA) on other slaughter parameters was not explicit. 
Key words: rabbits / animal nutrition / tannins / production parameters / carcass traits 
VPLIV TANINOV, DELNO VEZANIH NA BELJAKOVINE, NA PITOVNE IN KLAVNE 
LASTNOSTI RASTOČIH KUNCEV 
IZVLEČEK 
Merili smo pitovne lastnosti 144 kuncev (104 samcev in 40 samic) slovenske očetovske linije 
SIKA od odstavitve (31. dan starosti) do zakola (73. dan). Kunce smo razdelili v 5 skupin v dveh 
poskusih: kontrolno, F-0,3 (dodatek 0,3 % Famatana®), TA-0,19 (dodatek 0,19 % TA), TA-0,25 
(dodatek 0,25 % TA) in TA-0,5 (dodatek 0,5 % TA). Pripravek TA poskusno proizvaja Tanin 
Sevnica d.o.o., kjer se je v postopku ekstrakcije njihovega komercialnega produkta Farmatan® 
(vodni ekstrakt lesa navadnega kostanja (Castanea sativa Mill.)) del prisotnih taninov vezal na 
sirotkine beljakovine. Podatke smo obdelali s proceduro GLM v statističnem paketu SAS (SAS, 
1999). Dodatek 0,5 % TA (TA-0,5) je povečal zauživanje krme in dnevni prirast v najbolj 
kritičnem obdobju prvih 3 tednov po odstavitvi v primerjavi s kontrolno skupino. Dodatek 
0,25 % TA (skupina TA-0,25) je povečal priraste in telesno maso v celotnem poskusu v 
primerjavi s kontrolno skupino. V celotnem poskusu ni bilo razlik med skupinami v zauživanju 
in izkoriščanju krme. Kunci iz vseh skupin z dodanim TA (TA-0,19, TA-0,25 in TA-0,5) so 
imeli povečan delež jeter v primerjavi s kontrolno skupino, kar lahko kaže na povečano 
obremenitev jeter, vendar bi to morali preveriti na večjem številu živali. Vpliv dodanih taninov 
(Farmatan® ali TA) na druge klavne kazalnike ni bil jasno izražen. 
Ključne besede: kunci / prehrana živali / tanini / pitovne lastnosti / klavne lastnosti 
http://aas.bf.uni-lj.si 
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
118 
INTRODUCTION 
In intensive rabbit breeding the mortality rate is often very high and leads to high economic 
losses (Cheeke, 1987). The predominant reasons of mortality in growing rabbits are digestion 
disturbances, which are the consequence of unbalanced microbial population (dysbiosis) in 
caecum, caused by inadequate nutrition. To stabilise the caecal microbial fermentation various 
feed additives could be used. Among these, (poly)phenolics, especially tannins, have great 
potential. Published results showed that tannins influences microbial activity in caecum (Štruklec 
et al., 1993), improve production results (Štruklec and Kermauner, 1994) and reduce mortality in 
rabbits (Štruklec et al., 1993; Atta and Mouneir, 2005; Maertens and Štruklec, 2006).  
In Slovenia and some other European countries the sweet chestnuts (Castanea sativa Mill.) 
wood extract (CWE), containing mostly hydrolysable tannins, is frequently used in intensive 
rabbit breeding to control digestive disturbances. Tannins form complexes with proteins 
(Mangan, 1988; McLeod, 1974), thus forming a thin layer of nonsolvent proteins on the surface 
of intestinal mucous membrane, which protects brush border from microbial colonisation, 
appeases peristaltics in the case of inflammation and prevents the dehydration (Farmatan, 1998). 
Tannins form also complexes with amino acids, polysaccharides, metal ions, vitamins, bacterial 
cell membranes and enzymes involved in protein and carbohydrate digestion; these complexes 
are more or less stable (Makkar, 2003). Formation of such complexes can provoke negative 
effects in upper part of gastro-intestinal tract (GIT): reduces digestibility of nutrients and harms 
mucous membrane of small intestine, especially when higher concentrations of tannins are used. 
On the contrary, in lower part of GIT tannins can have favourable effects, because they could 
directly affect the activity of microbes by binding on their cell membranes (Butter et al., 1999; 
McSweeney et al., 2001). To take advantage of positive effects and to reduce or eliminate the 
negative effects, tannins should be in such form, that they would not interfere with digestion in 
the upper GIT, but react specifically only in the large intestine. To investigate this possibility we 
used preparation with working name TA, originating from experimental production process, 
where tannins from CWE were partly bounded to whey proteins. The aim of the study was to 
investigate if this complex between CWE and proteins (preparation TA) can have the same effect 
on production and some slaughter traits of rabbits as tannins in usually used form (CWE as 
commercial product Farmatan®).  
MATERIAL AND METHODS 
Feeds and animals 
Feed mixtures were prepared according to the recommendations for weaned rabbits 
(Maertens, 1995; (De Blas C. and Mateos G.G. 1998); Gidenne, 2003; Kermauner, 2005). All 
mixtures were prepared and peleted in Jata Emona, Novo mesto, Slovenia, chemical analyses 
were performed on Dept. of Animal Science, Biotechnical Faculty, University of Ljubljana. TA 
preparation is experimentally produced by Tanin Sevnica d.o.o. in extraction procedure of their 
commercial product Farmatan®, where only a part of tannins was bounded by whey proteins. 
Farmatan® is a natural product, produced by water extraction from sweet chestnut (Castanea 
sativa Mill.) wood. It is based on tannins, 85% of which are from a group of hydrolysable 
tannins and 15% from condensed tannins. Farmatan® contains about 75% of tannins, the rest are 
natural sugars. Chemical analysis of experimental feeds is shown in Table 1. 
After 3 days of restrictive feeding weaned rabbits were fed ad libitum. Drinking water was 
also ad libitum. Temperature in the trial room was between 17–24 °C, humidity between 56 and 
Kermauner, A. The effect of tannins partly bounded on proteins on production … in growing rabbits. 
 
119
85%. Animals were weighted and examined every trial week, when their health status was 
recorded as well.  
 
Table 1. Chemical composition of experimental feeds 
 
Component, g/kg DM Control F-0.3 TA-0.19 TA-0.25 TA-0.5 
Dry matter (DM), g/kg 906.0 916.1 914.9 917.4 917.0 
Crude proteins 189.2 191.4 190.4 188.5 190.2 
Crude fat 41.0 46.6 45.9 47.3 46.8 
Crude fibre 198.0 211.2 208.8 213.2 211.0 
Crude ash 99.2 93.6 85.0 82.4 85.1 
N-free extractive 472.7 457.3 470.0 468.6 467.0 
NDF 363.6 383.1 379.5 372.9 371.6 
ADF 231.8 243.6 234.4 232.4 232.0 
ADL 46.6 48.4 48.5 50.4 50.5 
Calcium 12.1 11.1 9.8 9.7 9.6 
Phosphorus 6.5 6.0 6.4 6.6 6.6 
Magnesium 3.7 3.6 3.6 3.6 3.6 
Potassium 14.6 15.1 15.0 15.2 15.1 
Sodium 2.2 2.2 2.5 2.3 2.2 
Digestible energy, MJ/kg * 10.2 10.2 10.2 10.2 10.2 
* calculated from tables (Schlolaut, 1982; Villamide et al., 1998) 
 
144 rabbits (104 male and 40 female) of Slovene sire SIKA line for meat production were 
weaned on 31st day of age and allotted to 5 groups in two trials: 
– Control: without added tannins (n = 36),  
– F-0.3: with addition of 0.3% of Farmatan® (powder) (n = 12), 
– TA-0.19: with addition of 0.19% of TA preparation (n = 36), 
– TA-0.25: with addition of 0.25% of TA preparation (n = 36), 
– TA-0.5: with addition of 0.5% of TA preparation (n = 24). 
Experiment lasted from 31st to 73rd day of age, when rabbits were slaughtered and slaughter 
parameters were recorded.  
Measurements and statistics 
During the experiment, feed intake and weight of rabbits were recorded weekly. Average feed 
intake, daily weight gain (DWG) and feed conversion ratio (FCR) was calculated each week and 
during the entire trial. Slaughter weight, warm carcass weight (without head and distal parts of 
legs, including liver and kidneys), weight of liver, kidneys and separate digestive organs (with 
their contents) were measured at slaughter and the proportions with respect to the slaughter 
weight were calculated. pH values in separate parts of digestive tract (stomach, duodenum, 
ileum, caecum) were also measured. Mortality and morbidity were observed daily. 
Statistical analysis was performed by SAS statistical package (SAS, 1999) with GLM 
procedure. Effects of experiment, feed and sex as fixed effects and weaning weight as 
independent variable (only in the case of live weight) were included in the model. Differences 
between groups were tested with t-test. Statistical analysis of mortality and morbidity was 
performed with CATMOD procedure (SAS, 1999). 
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
120 
RESULTS AND DISCUSSION 
The effect of added tannins 
Morbidity and mortality were low in both experiments, only 2 rabbits died during the second 
experiment. Both animals were from group TA-0.5 (8.33%), but differences between groups 
were not statistically proved. 
Significant differences in production parameters appeared mostly in the first part of the 
experiment (from 31st to 52nd day of age, Table 2). During this period rabbits with the highest 
addition of TA (TA-0.5) consumed more feed and had better daily weight gain (DWG), while 
during the entire trial (31–73 day) better DWG and higher live weight (Table 2 and 3) were 
observed in rabbits from group TA-0.25. There were no significant differences between groups 
in feed conversion efficiency (FCR) (Table 2).  
 
Table 2. Production parameters of rabbits during experiment 
 
Parameter Control n = 36 
F-0.3  
n = 12 
TA-0.19  
n = 36 
TA-0.25  
n = 36 
TA-0.5  
n = 22 
Feed intake 31–52 days 118.59 ab 117.98 ab 114.0 a 119.32 ab 124.15 b 
Feed intake 31–73 days 137.44 137.38 134.19 138.57 137.04 
DWG 31–52 days 48.50 a 48.21 ab 47.75 a 48.80 ab 51.10 b 
DWG 31–73 days 41.43 a 42.94 ab 42.61 ab 43.67 b 43.72 ab
FCR 31–52 days 2.45 2.44 2.40 2.44 2.42 
FCR 31–73 days 3.20 3.13 3.09 3.14 3.12 
a, b values with different superscripts differ significantly (p≤0.05) 
 
Table 3. Average live weight of rabbits during trial weeks 
 
Age, days Control n = 36 
F-0.3  
n = 12 
TA-0.19  
n = 36 
TA-0.25  
n = 36 
TA-0.5  
n = 22 
31    720    722    720    724    720 
38 1 057 1 064 1 052 1 060 1 070 
45 1 416 ab 1 410 ab 1 404 a 1 410 ab 1 447 b 
52 1 738 a 1 734 ab 1 723 a 1 749 ab 1 794 b 
59 1 948 ab 1 951 ab 1 939 a 1 973 ab 2 002 b 
66 2 255 2 282 2 259 2 301 2 311 
73 2 489 a 2 540 ab 2 516 ab 2 565 b 2 556 ab 
a, b values with different superscripts differ significantly (p≤0.05) 
 
Differences between groups were expressed only in some slaughter traits (Table 4). Carcass 
weight of rabbits from TA-0.25 group was higher than in Control group. Group with added 
Farmatan® had lower percent of fat on GIT, but only the difference between F-0.3 and TA-0.25 
was significant. The proportion of fat on GIT is very well correlated with the proportion of 
kidney fat, so we can assume that the rabbits from Farmatan® group were not so fatty. Rabbits 
from all groups with added TA preparation (TA-0.19, Ta-0.25 and TA-0.5) had significantly 
higher proportion of liver than Control rabbits. This can indicate higher burdening of liver where 
TA was added, but this influence has to be examined on greater number of experimental animals. 
 
Kermauner, A. The effect of tannins partly bounded on proteins on production … in growing rabbits. 
 
121
Table 4. Slaughter parameters of 73 days old rabbits 
 
Parameter Control n = 36 
F-0.3  
n = 12 
TA-0.19  
n = 36 
TA-0.25  
n = 36 
TA-0.5 
n = 22 
Slaughter weight (SW), g 2 494 2 547 2 521 2 575 2 569 
Carcass weight, g 1 343 a 1 373 ab 1 361 ab 1 396 b 1 392 ab 
Dressing percentage, % 53.87 53.91 53.99 54.21 54.18 
Liver, % SW 3.09 a 3.15 ab 3.35 b 3.34 b 3.33 b 
Kidney, % SW 0.59 0.61 0.60 0.61 0.62 
Spleen, % SW 0.069 0.060 0.065 0.064 0.060 
Stomach, % SW 5.09 5.25 5.21 5.15 4.98 
Small intestine, % SW 3.40 3.44 3.45 3.45 3.35 
Caecum, % SW 5.54 5.46 5.40 5.55 5.58 
Large intestine, % SW 2.43 2.38 2.37 2.26 2.30 
Gasto-intestinal tract (GIT), % SW 16.46 16.53 16.43 16.41 16.22 
Fat on GIT, % SW 0.89 ab 0.78 a 0.92 ab 0.93 b 0.92 ab 
pH in stomach 1.91 2.04 1.93 1.77 2.12 
pH in duodenum 6.20 6.38 6.39 6.07 6.14 
pH in ileum 7.33 7.44 7.40 7.36 7.36 
pH in caecum 6.30 6.32 6.27 6.32 6.31 
a, b values with different superscripts differ significantly (p≤0.05) 
The effects of experiment and sex 
When statistical analysis of joined data from both experiments was performed, the effects of 
experiment and sex were also included in the model. Production traits differed between 
experiments: in the second trial rabbits had higher daily weight gain (1st exp.: 41.93, 2nd exp. 
43.81 g/day, P = 0.0401) and reached higher live weight at the end of experiment (73 days of 
age: 1st exp.: 2 495, 2nd exp. 2 572 g, P = 0.0392), while in feed intake and FCR during entire 
trial differences were not significant (feed intake: 1st exp.: 134.97, 2nd exp. 138.87 g/day, NS; 
FCR: 1st exp.: 3.16, 2nd exp. 3.11, NS). Slaughter parameters did not differ between experiments 
as well.  
The growth of rabbits was probably affected by environmental conditions, especially by 
temperature, which was rather high at the end of the first trial (last two weeks between 21 and 25 
oC). These high temperatures depress feed intake and the growth of rabbits as well.  
The effect of sex was mainly expressed when slaughter traits were considered: male rabbits 
had lower proportion of small intestine (males 3.30, females 3.53%, P = 0.0162), large intestine 
(males 2.26, females 2.43%, P = 0.0710) and whole GIT (males 16.05, females 16.77%, 
P = 0.0110) and consequently better dressing percentage than female rabbits (males 54.28, 
females 53.79%, P = 0.0730). We know that caecum of female rabbits reaches higher weight at 
the same age than the caecum of male rabbits from literature (Lopez et al., 1988; Kermauner and 
Štruklec, 1996), but this was not found in our experiment. Kermauner and Žgur (2002) found 
similar differences between sexes for proportion of large intestine.  
In production traits the only difference was found in daily weight gain during the entire trial: 
male DWG was higher than that of females (males 43.75, females 42.00 g/day, P = 0.064). 
CONCLUSIONS 
The addition of tannins, partly bounded on proteins (TA preparation) had favourable effect on 
production parameters of growing rabbits: 
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
122 
– The addition of 0.5% TA (TA-0.5) increased feed intake and weight gain during the most 
critical period 3 weeks after weaning in comparison with Control group. 
– The addition of 0.25% of TA (group TA-0.25) increased weight gain and live weight of 
experimental rabbits during the entire trial in comparison with Control group. There were 
no differences between groups in feed intake and FCR during the entire trial. 
– Rabbits from all groups with added TA (TA-0.19, TA-0.25 and TA-0.5) had significantly 
higher proportion of liver than Control rabbits. This can indicate higher burdening of 
liver where TA was added, but this influence has to be examined on greater number of 
animals. 
– The effect of added tannins (Farmatan® or TA) on other slaughter parameters was not 
explicit. 
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