Acta agriculturae slovenica, suplement 1(avgust 2004), 173–178. 
12th Int. Symp. “Animal Science Days”, Bled, Slovenia, Sept. 2–4, 2004. 
Original scientific article 
Izvirni znanstveni prispevek 
EFFECT OF ACORN (Quercus robur) INTAKE ON FAECAL EGG COUNT IN 
OUTDOOR REARED BLACK SLAVONIAN PIG 
Krešimir SALAJPAL a), Danijel KAROLYI b), Relja BECK c), Goran KIŠ d), Ivan VICKOVIĆ e), 
Marija ĐIKIĆ f) and Damir KOVAČIĆ g) 
a) Univ. of Zagreb, Fac. of Agriculture, Dept. of Animal Science, Svetošimunska 25, HR-10000 Zagreb, Croatia, 
Ass. 
b) Same address as a), Ass., M.Sc. 
c) Univ. of Zagreb, Fac. of Veterinary Medicine, Dept. of Parasitology, Heinzlova 55, HR-10000 Zagreb, Croatia, 
Ass. 
d) Univ. of Zagreb, Fac. of Agriculture, Dept. Animal Nutrition, Svetošimunska 25, HR-10000 Zagreb, Croatia, Ass., 
M.Sc. 
e) Croatian Veterinary Institute, Dept. of Transmissible Spongiform Encephalopathies and Pathology of Ruminants, 
Savska 143, HR-10000 Zagreb, Croatia, Ass. 
f) Same address as a), Prof., Ph.D., M.Sc. 
g) Univ. of Zagreb, Fac. of Agriculture, Dept. of Agricultural Marketing, Svetošimunska 25, HR-10000 Zagreb, 
Croatia, Assist.Prof., Ph.D., M.Sc. 
ABSTRACT 
Chemical composition of the acorn (Quercus robur), tannin content and its ability to influence 
the faecal egg count output reduction in the Black Slavonian Pig reared in outdoor production 
system were investigated. A total of 20 Black Slavonian Pigs with naturally acquired parasite 
were randomly divided into experimental (E) and control (C) group. The pigs in experimental 
group were fed an acorn Ad libitum and the pigs of the control group were given only 2 kg of 
concentrate. The faecal egg count (FEC) was assessed by individual pig before and after acorn 
consumption. Faecal egg count reduction percentage (FECR%) was calculated separately for 
large roundworm (Ascaris suum) and other gastrointestinal parasites (Oesophagostomum spp., 
Strongyloides and Hyostrongylus sp.). The results demonstrate that acorn is tannin rich forage 
(65.6 g kg–1) which can reduce FEC output of pigs parasitised with gastrointestinal nemathodes. 
The reduction in total faecal egg count output in acorn fed pigs was 96.01%. FECR% for A. 
suum and other nematodes of the gastrointestinal tract (Oesophagostom spp., Strongyloides and 
Hyostrongylus sp.) was 96.56% and 93.55%, respectively. These results would imply that the 
gastrointestinal nematode population was highly sensitive and responsive to the effect of acorn 
tannin in feed. Therefore, the acorn grazing has the potential of aiding in the control of the 
gastrointestinal parasites in the outdoor reared Black Slavonian Pig and consequently results in 
reduced need for anthelmintic treatment. 
Key words: pigs / breeds / Black Slavonian Pig / outdoor system / acorn / Quercus robur / tannin / parasites  
VPLIV ZAUŽIVANJA DOBA (Quercus robur) NA ŠTEVILO JAJČEC V BLATU ČRNIH 
SLAVONSKIH PRAŠIČEV, REJENIH NA PROSTEM 
IZVLEČEK 
Proučevali smo kemično sestavo doba (Quercus robur), vsebnost tanina in njegovo sposobnost 
zmanjševanja izločenih jajčec z blatom pri črnih slavonskih prašičih, rejenih na prostem. Skupno 
20 črnih slavonskih prašičev, okuženih s zajedavci, ki se običajno pojavljajo, smo naključno 
razdelili v poskusno (E) in kontrolno (C) skupino. Prašiči v poskusni skupini so bili krmljeni po 
volji z dobom, medtem ko so prašiči v kontrolni skupini dobivali le 2 kg koncentratov na dan. 
http://www.bfro.uni-lj.si/zoo/publikacije/zbornik/suplementi/index.htm
Acta agriculturae slovenica, suplement 1(avgust 2004). 
 
174 
Število jajčec v blatu (FEC) smo določili pri vsakem prašiču pred in po zauživanju doba. 
Zmanjšanje števila jajčec v blatu (FECR%) smo izračunali ločeno za gliste (Ascaris suum) in 
druge želodčne in črevesne zajedavce (Oesophagostomum spp., Strongyloides and 
Hyostrongylus sp.). Rezultati so pokazali, da je dob s tanini bogata krma (65,6 g kg–1), ki lahko 
zmanjša izločanje FEC pri prašičih, okuženih z želodčnimi in črevesnimi zajedavci. FECR% pri 
prašičih, krmljenih z dobom, je znašalo 96,1 %. FECR% za A. suum in druge zajedavce 
prebavnega trakta (Oesophagostom spp., Strongyloides and Hyostrongylus sp.) je bilo 96,56% 
oziroma 93,55%. Ti rezultati kažejo, da je populacija zajedavcev v prebavnem traktu zelo 
občutljiva na vpliv dobovega tanina v krmi. Tako predstavlja paša doba veliko možnost pri 
kontroli zajedavcev prebavnega trakta pri reji črnih slavonskih prašičev na prostem in zmanjšuje 
uporabo antihelmentikov. 
Ključne besede: prašiči / pasme / črna slavonska pasma / reja na prostem / dob / Quercus robur / tanin / zajedalci 
INTRODUCTION 
Black Slavonian Pig production in East Croatia is an outdoor grazing system, which includes 
utilisation of natural resources of pasture and oak woodland with the supplement of a small 
amount of corn seed or some other cereal. In contrast to an indoor system, pigs are more exposed 
to parasite infection with an extensive spectrum and higher prevalence of helminth infection. 
Infections caused by gastrointestinal parasites continue to decrease animal productivity in all 
livestock species worldwide (Gill and Le Jambre, 1996). Various types of swine worms reduce 
growth rate and feed efficacy, damage tissues and predispose pigs to infection by other disease 
agents. The most prevalent internal parasites in pigs reared outdoors are coccidia (Isospora), 
whipworm (Trichuris suis), nodular worm (Oesophagostomum spp.), large roundworm (Ascaris 
suum) and intestinal threadworm (Strongyloides ) (Cabaret, 2003). 
Grazing management and chemotherapy are the classical methods of gastrointestinal 
nematode control. The increasing resistance of gastrointestinal nemathodes to anthelmintic drugs 
(Hertzberg and Bauer, 2000), concerns over possible chemical residue, environmental impact, as 
well as the cost of treatment, increases interest for alternative control methods. 
One of the recent no-drug recommendation methods is the consumption of plants rich in 
condensed tannin. The condensed tannin (CT) is the most common type of tannin found in 
different plant parts of different plant species. Plant parts containing tannins include bark, wood, 
fruit, fruit pods, leaves, roots and plant galls. 
Forages rich in condensed tannin have been found to improve performance of animals that 
had high faecal parasite egg counts (Niezen et al., 1998), reduce egg output and worm burden in 
general (Butter et al., 2000). The tannin content has a direct toxic effect on parasites and/or on 
the parasite fecundity (Hoskin et al., 2000), thus it may decrease hatch rate and larval 
development in faeces. Also, it affects the survival and migration of the infective larvae in the 
sward (Scales et al., 1994) and consequently reduces pasture contamination and ingestion of 
infective larvae. By grazing in oak woods, especially during season when alternative forage 
availability is scarce, pigs may consume huge amounts of tannin rich plant material.  
The aim of this study was to define the chemical composition of the acorn (Quercus robur) 
with an accent on tannin content and its ability to influence the faecal egg count output reduction 
in the Black Slavonian Pig reared outdoors. 
Salajpal, K. et al. Effect of acorn (Quercus robur) … faecal egg count in outdoor reared Black Slavonian Pig. 175
MATERIALS AND METHODS 
Animals and trial design 
A total of 20 Black Slavonian Pigs were used in this study. All of the animals were between 
18 and 20 months old, reared in an outdoor production system and maintained under same 
management and deworming programme. The animals were weaned at three months of age, with 
deworming taking place in the following two weeks with 7.5 mg of Levamisole (Nilverm 7.5%, 
Veterina d.o.o., Croatia) per kg of body weight. The examined pigs were reared on pasture 
utilizing natural resources with the addition about of 2.0 kg of concentrate per pig. A kg of 
concentrate had 12.5 MJ ME and 13.0% crude protein (CP). 
The 30 days before the start of the experiment, the pasture was divided into two same parts. 
The studied population was randomly divided into experimental (E) and control (C) group. Each 
group contained ten animals and was placed on the one of this pasture. In the next 30 days pigs 
were established a new “packing order” in the groups and were adapted to their enviroment. 
After the adaptation period, the pigs of the experimental group were fed acorn Ad libitum and 
the pigs of the control group were given only about 2 kg of concentrate daily per pig during the 
next 28 days.  
Acorn analysis 
Acorn was analysed (Table 1.) for dry matter (DM), crude protein (CP), ether extract (EE), 
crude fibre (CF), ash and nitrogen-free extract (NFE) with standard procedures according to 
A.O.A.C. (1984).  
Tannin content was determined colorimetrically following the A.O.A.C. method (1984). 
Metabolisable energy (ME, MJ/kg DM) was estimated according to DLG (1991). 
Parasitological parameters 
In both experimental and control group, faeces were collected directly from the rectum of the 
pigs on day one of acorn consumption (pre-treatment sample) as well as 28 days later (post-
treatment sample). Individual samples were obtained. Faecal egg counts (FECs) were carried out 
using a modified McMaster method with saturated sodium chloride as the flotation fluid 
(Whitlock, 1948). Total FECs were performed separately for large roundworm (Ascaris suum) 
and other gastrointestinal parasites (Oesophagostomum spp., Strongyloides and Hyostrongylus 
sp.). 
Data analysis 
All egg counts were transformed to the natural logarithm ln (FEC+1) to correct heterogeneity 
of variance and to produce approximately normally distributed data. After transformation the 
difference between the post-treatment eggs per gram value (EpG) in the experimental and the 
control group was calculated using t-test. The effect of EpG variation in control group during the 
experimental period was analyzed by the transformed pre- and post-treatment EpG value, using a 
paired t-test (SAS, 1999).  
The faecal egg count reduction percentage (FECR%) was calculated according to the 
following formula (Anderson et al., 1988): 
FERT% = 100 {1 – [(expX 2,2 / expX2,1) × (expX1,1 / expX1,2)]} 
X1,1 = mean value of the logarithmically transformed pre-treatement EpG value in the control group 
Acta agriculturae slovenica, suplement 1(avgust 2004). 
 
176 
X1,2 = mean value of the logarithmically transformed post-treatement EpG value in the control group 
X2,1 = mean value of the logarithmically transformed pre-treatement EpG value in the experimental group 
X2,2 = mean value of the logarithmically transformed post-treatement EpG value in the experimental group 
RESULTS AND DISCUSION 
The chemical composition of acorn (Quercus robur), including dry matter (DM), crude 
protein (CP), ether extract (EE), crude fibre (CF), ash, nitrogen-free extract (NFE) and tannin 
content is given in table 1.  
 
Table 1. Chemical composition of acorn (Quercus robur)  
 
Chemical composition, g kg–1 of DM  
 
Dry 
matter 
(DM) 
Tannin Crude 
protein 
(CP) 
Ether 
extract 
(EE) 
Crude 
fibre 
(CF) 
Nitrogen-
free extract 
(NFE) 
Ash MJ ME 
Acorn 
(Quercus robur) 662.00 65.60 44.56 35.97 92.30 809.67 17.50 7.47 
 
The results of chemical composition of acorn suggest that acorn is tannin rich forage 
(65.6 g kg–1). The effect of tannin rich forage on faecal egg count reduction percentage depends 
on tannin concentration in them. Beneficial effects of CT in forages for FEC in sheep and goat 
occur in the range 45 to 55 g of CT kg–1 of DM (Min and Hart, 2003). 
The tannin content of the acorn from different climates has previously been observed 
(Saffarzadeh et al., 2000) and the results show that the tannin content of the acorn from tropical, 
Mediterranean and cold climate was 49 g kg–1, 48 g kg–1 and 44 g kg–1, respectively. Similar to 
our result, Margaletić (2001) found 45 to 85 g kg–1 tannin content in the acorn from different 
parts of Croatia.  
Influence of the acorn consumption on the pre- and post-treatment FECs and FECR% results 
in Black Slavonian pigs are given in Table 2. 
 
Table 2. Mean value and range of faecal egg count (FEC) before and after acorn consumption 
and faecal egg count reduction percentage (FECR%) 
 
Experimental group Control group 
Mean FEC, range Mean FEC, range  
Pre-treatment Post-treatment Pre-treatment Post-treatment 
FECR% 
A. suum 
110.4 
(7–420) 
0.6 a 
(0–2) 
104.1 
(2–351) 
111.1 b 
(7–438) 96.56 
GIP* 
160.2 
(20–327) 
9.2 a 
(0–18) 
172.6 
(12–315) 
152.7 b 
(20–411) 93.55 
Total 270.60 (50–507) 
9.80 a 
(0–18) 
276.7 
(34–497) 
263.8 b 
(48–567) 96.01 
a,b = for rows values with different letters are significantly different (P<0.001), 
* = Other gastrointestinal parasites (Oesophagostomum spp., Strongyloides and Hyostrongylus sp.). 
 
The total pre-treatment FEC of the experimental group was 270.6 EpG with range of 50–507. 
Following acorn consumption FEC decreased to final post-treatment mean value of 9.8 EpG with 
Salajpal, K. et al. Effect of acorn (Quercus robur) … faecal egg count in outdoor reared Black Slavonian Pig. 177
range of 0–18. In the same time, the total pre-treatment and post-treatment FEC of control group 
was 276.7 EpG with range of 34–497 and 263.8 EpG with range of 48–567, respectively.  
Because some variations between groups pre-treatment EpG value and variation in eggs 
excretion over time is possible, in the FECR% calculation, pre- and post-treatment FEC values 
as well as the control group were included.  
The FECR% result (Table 2.) showed 96.01% reduction in total faecal egg count output in 
acorn fed pigs. These results are in agreement with similar findings in sheep and goats grazing 
on condensed tannins rich pastures (Niezen et al., 1995). Max et al. (2003) founded 91% of 
faecal egg reduction and 80% reduction in total worm burden were observed in lambs drenched 
with Quebracho extract (from the bark of the tropical dycotiledon Schinopsis spp.).  
The effect of tannin on the FEC and worm burden could be explained by the precipitation of 
proteins on the cuticule or in the digestive tract of the worm (Butter et al., 2000). Tannin induced 
protein precipitation is highest at the pH values near the isoelectric point of protein molecules. 
Therefore, it is fair to presume that gastrointestinal parasites residing in the portion of the gut 
where such conditions predominate would be the most susceptible to the effect of tannin. 
A. suum is the most common parasite of pigs and is typically present in the intestinal lumen, 
in direct contact with intestinal content. Therefore, FECR% for A. suum and other nematodes of 
the gastrointestinal tract (Oesophagostom spp., Strongyloides and Hyostrongylus sp.) was 
calculated separately. For A. suum and for other GIP, a 96.56% and 93.55% reduction in faecal 
egg count was calculated, respectively. This percentage would imply that the gastrointestinal 
nematode population in the pigs was highly sensitive and responsive to effect of acorn tannin in 
feed. 
CONCLUSIONS 
The study indicated that acorn (Quercus robur) is a relatively tannin rich forage (65 g kg–1 of 
DM). Also, the results demonstrate that Ad libitum acorn consumption can reduce total faecal 
egg count output (96.01%) in pigs infected with A. suum and other gastrointestinal parasites. 
Therefore, the acorn grazing has the potential of aiding in the control of the gastrointestinal 
parasites in the outdoor reared Black Slavonian Pig and consequently result in reduced need for 
anthelmintic treatment. 
ACKNOWLEDGEMENTS 
This work was supported by Ministry of Science, Education and Sports, Project number TP-
01/0178-40. The autors would like to thank members of PZ ¨Kulen Šokac¨ for their cooperation 
and help with this project. 
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