16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/12324
The antioxidant compounds in rat experimental diets based on
plant materials from organic, low-input and conventional
agricultural systems
Wiśniewska, K.1, Rembiałkowska, E.1, Hallmann, E.1, Rusaczonek, A.2, Lueck, L.3,
Leifert, C.3
Key words: rat feed, organic, conventional, low input, polyphenols
Abstract
Results presented in this paper are part of a study that investigates the effect of four
production systems on health effects in rats. This study was aimed to evaluate
differences in the levels of flavonols, total polyphenols, beta-carotene and lutein which
are well known antioxidants in four rat feeds. Raw plant materials were produced
according to four different agricultural systems: organic farming (without synthetic
pesticides and mineral fertilizers), low-input 1 (organic plant protection was used in
combination with mineral fertilizers), low input 2 (conventional pest management and
organic fertilizers were used) and conventional farming (synthetic pesticides and
mineral fertilizers were used). The results indicate that rat feed prepared from the
organically produced plants contained more antioxidant compounds, especially total
polyphenols, flavonols and lutein. Rat feed produced for feeding experiments varied
significantly in a series of key phytochemicals and therefore have the potential to
produce different health effects in the subsequent feeding trials.
Introduction
In opinion of many consumers organic farming may supply safer and healthier food
products than conventional farming. There is quite a lot of evidence that organic plant
products contain more vitamin C, polyphenols, iron, magnesium, phosphorus as well
as less nitrates, nitrites and pesticides residues than conventional ones (Leclerc 1991,
Rembiałkowska 2003). However, there are almost no papers about the composition of
the processed organic foods and the presented experiment is the only one comparing
the exact composition of the rat feed based on organic, low input and conventional
crops. The analysed feeds are used in the experiment comparing the health
parameters of rats; the results are published separately.
In 2006 a rat feeding trial was established at to assess the impact of four production
systems and their two management components -fertility management and crop
protection- on the general health and immune status in rats (Baranska et al 2007).
Prerequisite for this trial is that food is supplied that varies in its properties depending
on the management factors and that this variability is high enough to produce
differences in the feeding experiment as well.
Several groups of plant metabolites are thought to contribute to the potential health
effects of organic food. For instance polyphenols and especially flavonoids have a role
in prevention of cardiovascular disease and carcinogenesis (Czeczot, 2000). Because
organic production systems do not use synthetic pesticides plants have to rely on their
own defense strategies against insects and pests. A common strategy is to produce
more phytochemicals. Consequently, the use of organic agriculture may be a way to
increase the phytochemical content of plant foods (National Organic Program 2004).
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/12324
The aim of this study is to assess whether rat feed produced from grain and
vegetables from four different management systems varied in key phytochemical that
potentially affect health in the subsequent rat study.
Materials and methods
Barley, potatoes, carrots and onions were produced in the Nafferton factorial systems
comparison (NFSC) at the University of Newcastle’s Nafferton Experimental Farm,
Northumberland, UK in 2006. Conventional crop protection was applied according to
the British Farm Assured standards, and organic crop protection according to Soil
Association organic farming standards. Under conventional fertility management
mineral fertilizers are applied, and composted manure is used under organic fertility
management. The combination of the two factors results in four factor combinations:
organic fertility and crop protection management (OF-OP), organic fertility
management and conventional crop protection (OF-CP), conventional fertility
management and organic crop protection (CF-OP) and conventional fertility
management and crop protection (CF-CP). Samples from these factors combinations
(four replicates, n=16) were dried at moderate temperature in order to keep their
nutritive value. Rat feed based on these materials was produced according to the
nutritional recommendations for rat feeding trials. Compositional analysis of four
above mentioned rat feeds were done in 2007 in the Division of Organic Foodstuff,
Warsaw Agricultural University. They include: dry matter analysis by scale method
(PN-91/R-87019), flavonols analysis by Christ – Müller methods described by
Strzelecka et. al (1978), total polyphenols analysis by Folin – Ciocalteau colorimetric
methods described by Singleton and Rossi (1965), beta-carotene and lutein analysis
by liquid column chromatography described by Saniawski and Czapski (1983),
antioxidant activity analysis by colorimetric method described by Re et al. (1999). The
results of these qualitative characteristics of each of the different rat feeds were
statistically evaluated using Statgraphics 5.1 program ANOVA.
Results and discussion
As shown in tab. 1, all examined rat feeds contained similar levels of dry matter and
differences were not statistically significant. Organic vegetables often contained more
dry matter then conventional ones (Rembialkowska 2003, Rembialkowska 2004).
Obviously the preparation procedure of the feeds (drying, mixing, cooling, pelleting)
reduced differences that might have been present previously.
Total polyphenols content of the rat feed varied considerably between the
experimental treatments (Tab. 1). The highest level was observed in organic rat feed
(OF-OP), and the lowest in conventional (CF-CP) rat feed. Feeds from low-input
systems CF-OP and OF-CP have levels lower than the organic but higher than the
conventional feed. Both the fertility management and crop protection as well as their
interaction had an significant effect on the polyphenols status of the experimental
diets. The low-input version with pesticides and without fertilizers contains slightly
more polyphenols than that one with fertilizers. The lack of synthetic pesticides and
mineral fertilizers seems to have stimulated the polyphenol production.
The total content of flavonol was the highest in the organic feed and the lowest in the
CF-CP feed. Similar levels were observed in feeds from two low-input system (OF–
CP, CP-OF). Both, fertility management and crop protection had an significant effect
on the flavonol content of the feed. The results confirm a generally found tendency to
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/12324
higher flavonoids content in the organically produced plant materials (Rembialkowska
2004).
Table 1: The levels of: dry matter, polyphenols, flavonols, beta-carotene, lutein
and antioxidant activity in rat feeds from four management systems
ANOVA
Mean
P-value
Parameter
Main Effects
OF-OP
OF-CP
CF-OP
CF-CP
Fertilizer
Health
Interactions
Dry
matter
g/100g d.m.
90.02
89.85
89.66
89.95
0.76
0.56
0.29
Polyphenols
mg/100g d.m.
2166.9
1575.6
1530.3
1137.8
< 0.0001
<0.0001
0.05
Flavonls
mg/100g d.m.
3.39
3.00
2.97
2.31
0.03
0.02
0.55
Beta-carotene
mg/100g d.m.
0.82
0.82
0.80
0.72
0.68
0.58
0.73
0.41
0.33
0.38
0.24
0.04
0.25
0.54
28.59
28.06
28.16
27.71
0.07
0.13
0.91
Lutein
mg/100g d.m.
Antioxidant
activity
uM Trolox/1g.
There were no significant differences in beta-carotene concentration between the
treatments.
Lutein was identified as an important carotenoid in the feeds. The highest level of
lutein was found in organic rat feed (OF-OP) and the lowest level in the conventional
one(CF-CP). The two other rat feeds were less abundant in this compound and similar
in this respect (Tab. 1). Statistical analysis showed that the lutein content was only
affected by the fertility management.
There were no significant differences in the antioxidant activities of rat feeds from the
organic, conventional, and low-input cultivations.
The composite rat feed that contained barley, potatoes, carrots and onions produced
in the four management systems contained significantly different levels of
polyphenols, flavonols and lutein. Both, fertility management and crop protection
caused these differences but fertility management seems to have a stronger impact.
The results shown represent the second batch of rat feed used in the feeding trial and
confirm trends observed in the first batch analysed (Rembialkowska et al 2007).
16th IFOAM Organic World Congress, Modena, Italy, June 16-20, 2008
Archived at http://orgprints.org/12324
Conclusions
1) Rat feed produced for feeding experiments varied significantly in a series of key
phytochemicals and therefore have the potential to produce different health effects in
the subsequent feeding trials.
2) Rat feeds prepared from the organically produced plants contained more
antioxidant compounds, especially flavonoids total polyphenols and lutein.
Acknowledgments
This study was supported by the EU project QualityLowInputFood FOOD-CT-2003506358 and by the Polish Ministry of Science and Higher Education.
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