Acta agriculturae Slovenica, suplement 2 (september 2008), 99–105. 
 
16th Int. Symp. “Animal Science Days”, Strunjan, Slovenia, Sept. 17–19, 2008. 
  
Agris category codes: L02, L50 COBISS Code 1.08 
INFLUENCE OF ACORN INTAKE ON BLOOD LIPID PROFILE AND LONGISIMUS 
MUSCLE CHARACTERISTICS OF BLACK SLAVONIAN PIG  
Krešimir SALAJPAL a), Danijel KAROLYI a), Marija ĐIKIĆ a), Vesna KANTURA b), Goran 
KIŠ a) and Željko SINJERI c) 
a) Univ. of Zagreb, Fac. of Agriculture, Dept. of Animal Science, Svetošimunska c. 25, HR-10000 Zagreb, Croatia, 
e-mail: ksalajpal@agr.hr 
b) Univ. of Zagreb, Fac. of Veterinary Medicine, Heinzelova 55, HR-10000 Zagreb, Croatia 
c) Central clinical laboratory, General hospital “Dr. T. Bardek”, HR-48000 Koprivnica, Croatia 
ABSTRACT 
The beneficial effect of acorn on blood lipid level could be linked with presence of both high 
tannin content (70.10 g/kg DM) and high amounts of unsaturated fatty acids (more than 80%) 
such as linoleic (43.38%), oleic (30.52%) and alpha linolenic (4.58%) acid. In this study the 
influence of ad libitum acorn intake on blood lipid profile and longissimus muscle (MLD) 
composition of Black Slavonian pig were investigated and compared with the effects of 
commercial corn based diet. Acorn consumption in last three weeks of fattening period had a 
decreasing effect on triglyceride and total cholesterol concentration in blood without adverse 
effect on liver function. Compared with the intake of corn based diet, the intake of acorn resulted 
in 11% (0.22 mmol/l) lower total cholesterol (P < 0.05) concentration and 48% lower (0.20 
mmol/l) triglycerides concentration (P < 0.01). In addition, there was no observed statistically 
significant differences (P > 0.05) among finishing diets for any histochemical characteristics, 
except for diameter of intermediate fast-twitch oxidative-glycolytic (FOG) fiber types (58.10 µm 
and 51.67 µm in acorn and corn based fed pigs, respectively; P < 0.01). The trend toward lower 
proportion (10.80 vs. 12.36%) and smaller diameter (59.36 vs. 64.57%) of red slow-twitch 
oxidative (SO) fiber types (P < 0.08) was observed in acorn than in corn-based fed pigs.  
Key words: pigs / breeds / Black Slavonian pig / animal nutrition / acorn / Quercus robur / histochemical 
characteristics / blood lipids / longissimus dorsi 
VPLIV ZAUŽIVANJA DOBA NA MAŠČOBE V KRVI IN ZNAČILNOSTI DOLGE 
HRBTNE MIŠICE PRI ČRNEM SLAVONSKEM PRAŠIČU 
IZVLEČEK 
Ugoden vpliv doba na nivo maščob v krvi je lahko povezan s prisotnostjo velike vsebnosti tanina 
(70,10 g/kg SS) in velike količine nenasičenih maščobnih kislin (več kot 80 %), kot so linolna 
(43,38 %), oleinska (30,52 %) in alfa linolenska (4,58 %). V raziskavi smo preučevali in 
primerjali vpliv ad libitum zauživanja doba na profil lipidov v krvi in na sestavo dolge hrbtne 
mišice (MLD) pri prašičih črne slavonske pasme z vplivom komercialne krmne mešanice. Z 
zauživanjem doba v zadnjih treh tednih pitanja se je zmanjšala vsebnost trigliceridov in 
skupnega holesterola v krvi brez škodljivega vpliva na delovanje jeter. V primerjavi z 
zauživanjem komercialne krmne mešanice je zauživanje doba povzročilo 11 % (0,22 mmol/l) 
manjšo koncentracijo skupnega holesterola (P < 0,05) in 48 % (0,20 mmol/l) manjšo 
koncentracijo trigliceridov (P < 0,01). Pri histokemičnih lastnostih med krmama ni bilo opaziti 
nobenih statistično značilnih razlik (P > 0,05), razen za lastnost premer vmesnih hitrih 
oksidativno glikolitičnih (HOG) mišičnih vlaken (58,10 µm pri prašičih, krmljenimi z dobom in 
51,67 µm pri prašičih, krmljenimi s komercialno krmo; P < 0,01). Pri rdečih počasnih 
oksidativnih (PO) mišičnih vlaknih smo opazili trend (P < 0,08) k manjšemu deležu (10,80 proti 
http://aas.bf.uni-lj.si 
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
100 
12,36 %) in manjšemu premeru (59,36 proti 64,57 %) pri prašičih, krmljenimi z dobom, v 
primerjavi s prašiči, krmljenimi s komercialno krmo. 
Ključne besede: prašiči / pasme / črni slavonski prašič / prehrana živali / dob / Quercus robur / histokemične 
lastnosti / krvne maščobe / longissimus dorsi 
INTRODUCTION 
Recent study showed that the meat and meat products (dry-cured products) obtained from 
pigs reared traditionally in outdoor production system have a higher technological and nutritional 
value. Its has been characterized by high tocopherol content in tissues as a result of the intake of 
pasture (Cava et al., 2000), high content of monounsaturated fatty acids (MUFA) from acorn 
(Cava et al., 1997), high content of total iron and higher oxidative capacity of the muscles as a 
results of physical exercise performed by these animals in extensive system (Lawrie, 1998). In 
the past, acorn grazing was a cost-effective energy source in fattening of Black Slavonian pigs, 
and grazing in oak woodland was constituent part of traditional production system. In the recent 
years with popularization of free range and/or organic pig production, acorn grazing is again a 
common practice. Previous studies reported that in spite of their relatively high carbohydrates 
content, acorns contain low crude protein (CP ranged from 30 to 40 g/kg DM) and variable 
amounts of lipids and various sterols (EE ranged from 15 to 60 g/kg DM; Leon-Camacho et. al., 
2004; Lopes and Bernardo-Gil, 2005; Margaletić, 2001). Acorn is a rich source of cholesterol-
neutral oleic acid (Estevez et al., 2004; Cava et al., 1997) and contain a noticeable amount of 
alpha linolenic acid (Karolyi et al., 2007; Petrović et al., 2004), an n-3 polyunsaturated fatty acid 
(PUFA), which is important in eicosanoid synthesis and has beneficial effects on serum 
triglyceride and HDL-cholesterol level (Simopoulos, 1991). In addition acorns contain various 
biologically active phenolic compounds such as tannins, gallic and ellagic acid, and different 
galloyl and hexahydroxydiphenoyl derivatives (Cantos et al., 2003; Rakić et al., 2006) which are 
known for their role in regulation of blood lipid level. Specifically, they can reduce total plasma 
cholesterol level as well as LDL-cholesterol level decreasing the activity of 3-hydroxi-3-
methylglutaryl coenzyme A (HMG-CoA) reductase and Acyl CoA-cholesterol-o-acyltransferase 
(ACAT), the key enzymes in cholesterol biosynthesis and their esterification in the blood. 
Furthermore, tannins can inhibit the accumulation of macrophage-lipid complex on the 
endothelian wall of artery and may prevent atherosclerosis (Chung et al., 1998). Influence of 
finishing diet of acorn or corn based diet on fatty acid profile of longissimus muscle of Black 
Slavonian pigs was presented previously (Karolyi et al., 2007). In this study, the influence of 
acorn intake on blood lipid profile and longissimus muscle (MLD) composition were 
investigated and compared with the effects of commercial corn based diet.  
MATERIAL AND METHODS 
Animals and diets 
The study was performed on 10 pigs of the local Black Slavonian (BS) breed. All animals 
were reared in outdoor production system and maintained under same management and feeding 
programme. The examined pigs were reared on pasture utilizing nature resources with the 
addition about of 0.5 kg of concentrate daily per pig. In addition, last two mounts pigs were 
fattened in piggery with corn based mixture (Table 1.). Three weeks before slaughter pigs are 
randomly divided into two groups, the experimental (E) group were fed acorn from Slavonian 
oak (Quercus robur L.) Ad libitum and second one (Control group, C) were continued to be fed 
mixture diets, about 2 kg daily per pig. At the slaughter pigs were on average 154 ± 22 kg and 18 
Salajpal, K. et al. Influence of acorn intake on blood lipid profile … characteristics of Black Slavonian pig. 
 
101
mounts of age. The chemical composition of finishing diets (acorn and concentrate) was 
determined with standard procedures according A.O.A.C. (1990) methods.  
 
Table 1. Chemical composition and fatty acid profile of finishing diets 
 
Finishing diets  
Acorn Concentrate 
% Dry matter a (DM) 61.5 88.2 
% Crude protein a (CP) 3.4 16.2 
% Ether extract a (EE) 1.8 3.2 
% Crude fiber a (CF) 8.9 2.4 
% Nitrogen free extract a (NFE) 84.7 73.1 
% Ash a 1.2 5.1 
% FAMEs b    
C14 0.15 0.14 
C16 18.09 17.54 
C16:1 0.29 0.95 
C17 0.12 1.05 
C18 1.32 2.36 
C18:1 (n-9) 30.52 24.85 
C18:2 (n-6) 43.38 50.18 
C18:3 (n-3) 4.58 1.92 
C20:1 (n-9) 0.37 0.27 
% Tannins a 7.01 - 
a Expressed as % of dry matter; b Expressed as % of fatty acid methyl esters 
Collection and analysis of blood samples 
Blood samples were collected from each of animal from experimental (E) group and control 
(C) group before exsanguinations. Samples were taken from the jugular vein using commercial 
vacutainer system and serum collection tube for blood lipid profile analyses. Serum triglyceride, 
total cholesterol, HDL-cholesterol and LDL-cholesterol concentration were measured using the 
automated biochemistry analyzer Olympus AU 400 (Olympus Diagnostica Gmbh, Hamburg, 
Germany) and Olympus AU® Series Reagents.  
Meat quality, histochemical characteristics and fatty acid analysis 
On the Longissimus dorsi muscle the initial (pHi) and the ultimate (pHu) pH were taken at the 
last rib level using Testo 230 portable pH meter (TESTO, Germany) with penetration electrode 
(type 13) 45 min and 24 h post mortem. On the same place, after 24 h muscle colour (CIE L* a* 
b*) was measured on the fresh cut surface of cross section after approximately 5 minutes of 
blooming time using a Minolta Chromameter CR-410 (Minolta Camera Co. Ltd. Japan). In the 
addition, 30–45 min after slaughtering muscle sample for histochemical analysis was taken from 
middle portions of m. longissimus dorsi (MLD) at the last rib level of each animal. The 
histochemical profile was determined by staining 8 µm transverse serial sections for SDH 
activity and with myosin ATPase method at different pH. Diameter and proportions of muscle 
fibre types were analysed on two different pieces of each muscle samples and more than 200 
muscle fibres per sample were analysed. The muscle fibre diameter was measured on cross-
sections of individual muscle fibres using a Nikon microscope and a Leitz microscale with 10 
µm divisions. Muscle sampling and fatty acid profile analysis of MLD was described previously 
by Karolyi et al. (2007).  
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
102 
Data analysis 
The Student t-test for independent variables (PROC TTEST; SAS, 1999) was used to compare 
the blood lipid data and histo-chemical characteristics of MLD from two finishing diet groups.  
RESULTS AND DISCUSSION 
The influence of acorn (Quercus robur L.) consumption on blood lipid profile and some 
blood constituents are shown in Table 2. 
 
Table 2. Influence of acorn (Quercus robur L.) intake on blood lipid level and some blood 
constituents 
 
Finishing diets  
 Concentrate 
 (SD) 
Acorn 
(SD) 
 
Significance 
Triglycerides (mmol/l) 0.42 (0.07) 0.22 (0.03) 0.001 
Total cholesterol (mmol/l) 2.01 (0.13) 1.79 (0.08) 0.05 
HDL-cholesterol (mmol/l) 0.83 (0.12) 0.77 (0.15) NS 
LDL-cholesterol (mmol/l) 1.20 (0.12) 1.14 (0.09) NS 
Glucose (mmol/l) 5.37(0.72) 5.06 (0.61) NS 
ALT (U/L) 59.60 (2.51) 43.25 (4.11) 0.01 
AST (U/L) 46.20 (7.66) 50 (11.17) NS 
GGT (U/L) 21.20 (6.02) 25.00 (4.24) NS 
NS = Non Significant (P > 0.05) 
 
As shown in Table 2. Ad libitum acorn consumption during the three weeks before slaughter 
resulted in 11% (0.22 mmol/l) lower total cholesterol (P < 0.05) concentration and 48% lower 
(0.20 mmol/l) triglycerides concentration (P < 0.01) compared with the intake of corn based diet. 
The blood lipids level, especially cholesterol and triglycerides, are the most related to types of 
lipids in feed and presence of biologically active compounds with strong influence on lipid 
metabolism such as tannins (Park et al., 2002; Yugarani et al., 1992). Tannins are phenolic 
compounds commonly found in fruits of many plant and non-toxic when are orally administrated 
to a mouse and rats at a dose of less than 5 000 mg/kg or in humans at dose of 500 mg/kg of body 
weight. The analyses of Quercus robur L. acorn from 43 locations in Croatia (Margaletić, 2001) 
suggest that acorn is tannin reach fruits with variation between 45 and 85 g/kg DM. Acorn used 
in our study contained a 70.10 g tannin /kg DM, and we presume that at Ad libitum consumption 
(> 2 kg/pigs/day) of acorn, the tannin daily intake was more than 500 mg/kg body weight. At this 
tannin intake we could not expected some adversely effect on liver function what is supported 
with results of serum enzymes activity of ALT, AST and GGT which was within physiological 
range for pigs (Kaneko, 1997). The previous study (Park et. al., 2002) reported that tannin 
supplementation decrease plasma total cholesterol and triglyceride level and increase HDL-
cholesterol/total-cholesterol ratio. The same authors were found lower activity of 3-hydroxy3-
methyl-glutaryl–coenzyme A (HMG–CoA) and acyl-coenzyme A cholesterol acyltransferase 
(ACAT), the key enzymes involved in cholesterol synthesis and their esterification in the blood 
(Bocan et al., 1998). Yugarani et al. (1992) noted that tannin is able to reduce LDL-cholesterol 
and triglyceride without affecting the HDL-cholesterol level. In this study, acorn intake did not 
influence HDL-cholesterol or LDL-cholesterol level. In addition, the beneficial effect of acorn 
on blood lipid profile could be linked with fatty acid composition of acorn. General is accepted 
that unsaturated fatty acids have beneficial effect on blood lipid level, especially n-3 fatty acids 
which have been linked to a wide-range of health benefits, including reduced risk of elevated 
Salajpal, K. et al. Influence of acorn intake on blood lipid profile … characteristics of Black Slavonian pig. 
 
103
blood lipid level-related disease such as hyperlipidemia, atherosclerosis, angina pectoris, stroke 
and hepatic disease (Simopoulos, 1991). Previous has been reported that diet reach in oleic acid 
(Rebollo et al., 1998) and n-3 fatty acids (alpha linolenic, DHA, DPA, EPA; Kelley et al., 2007; 
Ni Eidhin et al., 2003; Tholstrup et al., 2004;) reduces plasma triglyceride, total cholesterol, and 
LDL-cholesterol levels and improve the HDL-cholesterol/total cholesterol ratio. In comparison 
to corn based finishing diet (Table 1), acorn had higher proportion of oleic (30.52 vs. 24.85%) 
and alpha linolenic (4.58 vs. 1.92%) acid and lower proportion of linoleic acid (43.38 vs. 
50.18%). These findings could explain lower triglycerides and total cholesterol level in pigs fed 
acorn than in pigs fed corn based diet. In our study differences in HDL- and LDL-cholesterol 
concentration was not observed possible due to short fattening period and small number of 
animals in trial. In addition to influence on blood lipid profile, dietary fatty acid composition has 
a strong influence on fatty acid profile of tissues (Moloney, 2002). It has been reported that high 
oleic acid content in tissues from Iberian pigs raised on woodland pasture is a result of the large 
amounts of oleic acid in the acorn (more than 60%; Cava et al., 1997; Estevez et al., 2004). 
Furthermore, Rebollo et al. (1998) found reduction in the plasma levels of cholesterol, 
triglycerides and LDL-cholesterol in humans after consumption the fat from acorn-fed Iberian 
ham which have high content of oleic acid (60% of total fat). The results of the influence of 
acorn of Slavonian oak (Quercus robur L.) intake on fatty acid profile and meat quality traits of 
longissimus muscle has been presented previously in works by Karolyi et al. (2007). Feeding 
acorn Ad libitum during the last three weeks of fattening period increased the content of alpha 
linolenic acid (C18:3 n-3) in the longissimus muscle (0.37 vs. 0.12%, P < 0.01) and consequently 
decreased the n-6/n-3 ratio (24.1 vs. 69.3, P < 0.01) in comparison to concentrate fed pigs. 
Muscle pH as well lightness (L*) and redness (a*) were not affected by acorn consumption while 
the yellowness (b*) was a higher (P < 0.05) in pigs fed corn-based diets than in pigs fed acorn 
(6.18 vs. 3.15). Generally high intramuscular fat content (Table 3.) without statistically 
significant differences between groups was observed in both acorn and corn based fed pigs (6.6 
and 7.2%, respectively).  
 
Table 3. Histochemical characteristics and meat quality traits of m. longissimus dorsi (MLD) 
from pigs fed acorn and mixture finishing diets 
 
 
a Expressed as percent of dry matter; Lipids profile of IMF was presented in Karolyi et. al. (2007); NS = Non 
Significant (P > 0.10) 
Finishing diets 
Fibre type Concentrates  
(SD) 
Acorn  
(SD) 
Significance 
Percentage 
    SO 12.36 (0.54) 10.80 (0.54) 0.08 
    FOG 19.00 (1.01) 19.10 (1.01) NS 
    FG 68.64 (1.04) 70.10 (1.04) NS 
Diameter (µm) 
    SO 64.57 (1.81) 59.36 (1.81) 0.08 
    FOG 58.10 (1.23) 51.67 (1.23) 0.01 
    FG 67.93 (1.42) 68.49 (1.42) NS 
Meat quality traits 
    pHi 6.11 (0.19) 6.25 (0.38) NS 
    pHu 5.88 (0.12) 5.86 (0.07) NS 
    Lightness (L*) 50.51 (3.93) 49.35 (6.61) NS 
    Redness (a*) 20.30 (0.70) 19.74 (1.95) NS 
    Yellowness (b*) 6.18 (2.08) 3.15 (1.07) 0.01 
Dry matter, % 30.08 (2.16) 29.74 (1.42) NS 
Intramuscular fat a 7.19 (2.81) 6.55 (1.56) NS 
Acta agriculturae Slovenica, suplement 2 (september 2008). 
 
104 
High potential for intramuscular fat deposition is characteristics of the many native pig breeds 
such as Black Slavonian (Senčić et al., 2005), Mangalitza (Szente et al., 2004) or Iberian pig 
(Lopez-Bote, 1998). Lipid composition is one of the main characteristics related to meat quality 
affected by muscle fiber type (Andres et al., 2001). It is usually accepted that muscles showing 
an oxidative metabolism should have higher lipid content, due to their ability to use fatty acids as 
an energy source. Therefore, a higher amount of intramuscular fat content implies a higher 
proportion of oxidative fiber. In spite of this, the absence of differences in IMF content was 
reflecting on fibres type composition of MLD. As shown in Table 3 there were no significant 
differences (P < 0.05) between pigs of two finishing diets for any histochemical characteristics, 
except for diameter of FOG fiber type. However, the tendency to lower proportion (10.80 vs. 
12.36%) and smaller diameter (59.36 vs. 64.57%) of SO fibre type (P < 0.08) was observed in 
acorn fed than in corn-based fed pigs.  
CONCLUSIONS 
Present study shown that Ad libitum consumption of acorn of Slavonian oak (Quercus robur 
L.) in the short pre-slaughter fattening period can cause positive changes in blood lipid profile 
such as decreasing of triglycerides and total cholesterol concentrations without adversely effect 
on liver function in Slavonian pigs. In addition, the considerable amounts of alpha linolenic acid 
in acorn could have beneficial effect on the n-6/n-3 ratio in the meat. On the other hand, three 
weeks of fattening period with acorn did not influence on differences in IMF or in diameter and 
proportion of each muscle fiber types.  
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