Livestock Research for Rural Development 19 (7) 2007 | Guide for preparation of papers | LRRD News | Citation of this paper |
The peels of four varieties of citrus fruits namely Citrus sinensis (Washington), Citrus sinensis (Ibadan), Citrus limonum and Citrus qurantifolia were sun-dried and milled to obtain citrus fruit peel meal (CFPM). The CFPM of each variety was subjected to phytochemical screening to detect the presence of phytonutrients.
Phytochemical screening showed that each of the peels contained tannin, saponin, phytate, oxalate, flavonoids and limonene. Whereas, the variation of each of these phytonutrients between the peel meals was significantly different (p<0.01) except for tannin (p>0.05), they were at low concentrations and below the levels reported in literature to be toxic to livestock species.
Animal studies are however recommended to determine at what level limonene becomes toxic to farm animals.
Keywords: Citrus fruit peel, livestock production, phytonutrients
The shortage of good quality feeds needed to sustain livestock growth, especially during the dry season has been a major challenge to the industry in the developing countries. Thus crop residues, agro-industrial by products and non conventional feed resources which abound during the dry season are being evaluated to access their nutritive potential to support livestock productivity. Several factors have been generally identified as limiting to the utilization or high incorporation of non conventional feedstuffs in livestock feed. These include low protein content (Gohl 1981), high fibre (McDonald et al 1988), amino acid imbalance and presence of anti-nutritional factors (Tacon and Jackson 1985). Anti-nutritional factors have significant negative effects on livestock production. These effects include reduction in palatability, digestibility and utilization of ration, intoxication of different classes of livestock, resulting in mortality or decreased production of animal and reduction in the quality of meat, egg, and milk products due to the presence of hazardous residues (Amuchie 2001).
A number of agro-industrial by-products or wastes like citrus
pulp, citrus meals, citrus seed meal, citrus molasses and citrus
peels are generated from fresh citrus after the main products of
interest have been removed or extracted during processing or peeled
for direct human consumption as in the case of developing
countries. Clusters of peel of the sweet orange are usually noticed
on streets and along major roads in Nigeria because government and
orange retailers have no strategic disposal programme thus becoming
an environmental problem. Ipinjolu (2000) has suggested that
rather than discarding the orange peels, they can be sun-dried and
then milled in grinding machine to fine particle to obtain the
orange peel meal which can be included in fish diets. Sweet orange
fruit rind (peel) meal has been observed to be a source of calorie
and protein comparable with maize (Oluremi et al 2006). The peel
contains oil sacs and the oil is composed of 91-94% d-limonene and
2.0-2.1% β-myrcene as a minor constituent (Arizona Chemical
1999). Polymetholated flavones are also a class of compounds found
in citrus peel and produce no negative side effects in the animals
fed the polymetholated flavones containing diets (Davis 2004). The
objective of this study is to determine the phytonutrients in the
peel of some common varieties of citrus and to show their dietary
implication in livestock production.
Four varieties of citrus fruit namely Citrus sinensis:
Washington variety (CSW), Citrus sinesis: Ibadan varieties
(CSI), which are both sweet orange varieties, Citrus
limonum: Lemon (CL) and Citrus qurantifolia: lime (CQ)
were purchased from the wholesale citrus fruits depot in the
University town of Makurdi. The outer cover of the fruits
otherwise called flavedo which contains chromoplasts and oil sacs
were carefully peeled to minimise the inclusion of albedo which is
an inner layer of spongy white tissue. The peels obtained from
each of the four citrus fruits were sun-dried until they become
crispy, a process which took 48 hrs for Citrus sinensis
(Washington), Citrus sinensis (Ibadan) and Citrus
qurantifolia and 72hrs for Citrus limonum. Dried peels
were ground with a Hammer Milling machine having a screening sieve
of 1mm pores to obtain the citrus fruit peel meal (CFPM).
Homogenous sample of each of the peel meals of the Washington
variety (CSWM), Ibadan variety (CSIM), lime (CLM) and lemon (CQM)
the four citrus fruits was subjected to phyto-chemical analysis for
qualitative and quantitative determinations of phytonutrients
(Harborne 1973; Sofowora 1993 and Trease and Evans 1989). The
quantitative data obtained was statistically analysed using one way
Analysis of Variance described in the Minitab Statistical Software
(1991).
The phytochemical screening of the citrus fruit peel meal samples revealed the presence of limonene, tannin, saponin, phytate, oxalate and flavonoid in all the citrus fruit peel meals (Table 1).
Table 1. Phytochemical screening of Citrus fruits peel meals |
||||
Compound |
Citrus Fruit Peel Mea |
|||
CSWM |
CSIM |
CLM |
CQM |
|
Tannin |
++ve |
++ve |
++ve |
++ve |
Saponin |
++ve |
++ve |
++ve |
++ve |
Phytate |
+ve |
+ve |
+ve |
+ve |
Oxalate |
+ve |
+ve |
+ve |
+ve |
Flavonoid |
++ve |
++ve |
++ve |
++ve |
Limonene |
++ve |
++ve |
++ve |
++ve |
+ve=present, ++ve=highly present |
The level of each of these compounds was highly significantly different (p<0.01) between the peel meals of the different citrus fruits with the exception of tannin which did not differ significantly (p>0.05) as shown in Table 2. It was also observed that the levels of saponin, phytate oxalate and flavonoid in the peels were significantly higher (P<0.01) in the two sweet orange varieties (Washington and Ibadan) than in CLM and CQM.
Table 2. Phytonutrients in Citrus fruits peel meals (%) |
|||||
Compound |
Citrus Fruits Peel Meals |
||||
CSWM |
CSIM |
CLM |
CQM |
SEM |
|
Tannin |
0.463 |
0.523 |
0.477 |
0.433 |
0.057ns |
Saponin |
0.043a |
0.037b |
0.034c |
0.030d |
0.001** |
Phytate |
0.077b |
0.082a |
0.066c |
0.062d |
0.002** |
Oxalate |
0.048a |
0.043b |
0.036c |
0.033d |
0.002** |
Flavonoid |
0.045a |
0.034b |
0.025c |
0.028c |
0.002** |
Limonene |
1.275b |
1.350ab |
1.240b |
1.555a |
0.054** |
a,b,c,d Means with different superscripts on the same row are highly significantly different (p<0.05). nsNot significantly different (p>0.05). SEM=Standard error of mean. |
Tannin which usually gives rise to a dry, pickery, astringent sensation in the mouth was in the range of 0.433-0.523% in the citrus fruit peel meals. This is lower than 1-20% commonly found in cereals and legumes reported to have depressed the growth rate, resulted in a poor feed efficiency ratio and increased the amount of food required per unit weight gain in non-ruminants (Price and Butler 1980). However, in ruminants, dietary condensed tannins of 2-3% have been shown to impart beneficial effects because they reduce the wasteful protein degradation in the rumen by the formation of a protein tannin complex (Barry 1987).
The concentration of saponin in the peels of the citrus fruits was between 0.030 and 0.043%. Saponins are bitter and reduce the palatability of livestock feeds. Among the effects of saponin on animals are growth inhibitions in swine and poultry, reduced palatability of food and in increased excretion of cholesterol concentration (Malinow et al 1987). The saponin content of the peel meals were observed to be appreciably below 3% which was reported by Kumar (1991) to be responsible for cattle losses when they grazed on alfonibrilla (Drymaria arenaroides) and thus may not be hazardous to livestock.
The level of phytate in the peels of the citrus fruits range between 0.062 and 0.082%. This is observed to be low when compared with phytate content of 146 and 353mg % in maize, 206 and 280mg% in sorghum, 14mg % in potato (Concon 1988), 624mg %, 855mg % and 637mg % in cassava, cocoyam and yam, respectively (Marfo and Oke 1988). Phytate presence is largely blamed for the complexing of dietary essential minerals in legumes and cereals and rendering them poorly available to monogastric animals. It is apparent that phytate content of the citrus fruits peel meals is safe for livestock consumption.
Oxalate was detected in the citrus fruit peel meal and its concentration was between 0.033 and 0.048%. Like phytate, oxalate can decrease the availability of dietary essential minerals such as Ca. At high concentrations, oxalate causes death in animals due to its corrosive effects (Kumar 1991). In small amounts, it causes a variety of pathological disorders including hyperoxaluria, pyridoxine deficiency, and calcium oxalate stones. The oxalate level in CFPM seems low when compared with 0.7%, 0.275% for cocoa and beet roots, respectively (Gontzea and Surtzescu 1968; Concon 1988).
Flavonoids were detected in citrus fruits peel meals with phytochemical screening. Quantitatively, the amount present was between 0.025 and 0.045%. Flavonoids have been reported to function as pigments and antioxidants (Kumar 1991) and can inhibit enzymes in mammals (Hollman 1997). The most important flavonone in oranges is hesperidin which has been reported to lower high blood pressure as well as cholesterol in animal studies and have strong anti-inflammatory properties (CSIRO 2004).
The level of limonene found in citrus fruits peel meals was in
the range of 1.240 - 1.555%. Citrus seed meal has been reported to
contain limonene which is toxic to pig and especially to poultry
(Serres 1999). While orange peel has been included in the diet of
ruminant especially in those areas where its production is high
(Megias et al 1993), the presence of limonene may be a limitation
to its use in raising monogastric animals. Thus far, nutritional
trials with monogastric animals have shown that the meal of sun
dried peels of Citrus sinensis can replace dietary maize in
broiler diet up to 20% (Agu 2006), and 40% in rabbit (Oluremi et al
2005), without any adverse effect on their performance.
Nutrition quality of feeds is critical in livestock development. The phytochemical examination of citrus fruits peel meals of Citrus sinensis (Washington variety), Citrus sinensis (Ibadan variety), Citrus limonum and Citrus qurantifolia has shown that they contain tannin, and saponin, phytate, oxalate, flavonoid and limonene in varying highly significant amounts (p<0.01). It was observed that their concentrations in CFPM were lower than the levels at which these chemical compounds have been reported be harmful to farm animals.
The effect the presence of limonene which has been reported to
be toxic to pig and especially poultry should be investigated to
determine at what level it becomes toxic to various livestock
species.
Agu P N 2006 Nutritional Evaluation of sweet orange (Citrus sinensis) Peel as a Feed Resource in Broiler production. Unpublished M.Sc. Thesis. Department of Animal Production, University of Agriculture, Makurdi. Benue State. Nigeria.
Amuchie E C Jr 2001 Antinutritional factors in feeds and their effects on Livestock Production. Seminar present to the Department of Animal Production. Universityof Agriculture, Makurdi, Benue State. Nigeria
Arizona Chemical 1999 Private Communication to the Flavour and Frangance High Production Volume Chemical Consortia. Unpublished Report.
Barry T N 1987 Secondary Compounds of forages in Nutrition of herbivores. Hacken J B and Termouth J H (editors). AP Suyndey. Pp. 91-120.
Concon J M 1988 Food Toxicology Parts A and B. Marcel Dekke, New York.
CSIRO 2004 The Commonwealth Scientific and Industrial Research Organisation Report. February 26; 2004.
Davis 2004 Tangerine peels may lower Cholesterol. Journal of Agricultural and Food Chemistry May 12th,2004.
Gohl B 1981 Tropical Feeds. FAO Animal Production Health Series 12. p. 529.
Gontzea I and Surtzescu P 1968 Natural anti-nutritive substances in food stuffs and forages. Kargel, Basel.
Harborne J B 1973 Pyhtochemical Methods. A guide to modern Techniques of Plant Analysis. Chapman A and Hall. London.
Hollman P C H 1977 Bioavailability of flavonoids. European Journal of Clinical Nutrition 51: 566-569.
Ipinjolu J K 2000 Performance of juvenile orange koi carp (Cyprinucarpio leanneanus) fed diets supplemented with sweet orange peel meal: Body composition, nutrition, utilization and skin pigmentation. Sokoto Journal of Veterinary Science 2000: 228-229.
Kumar R 1991 Antinutritional Factors, the Potential risks of toxicity and methods to alleviate them. Proceeding of FAO Expert Consultation held at the Malaysian Agricultural Research and Development Institute, Kuala Lumpur, Malaysia. October 14th-18th, 1991.
Malinow M R, Concon W E, Mclaugblin P, Tafford C, Lin D S, Livingstone A L, Kohler G O and McMulty W P 1987 Cholesterol and bile acid balance in Macasa fascicularis. Effects of alfalfa saponin. Journal of Clinical Invest. 67: 156-164.
Marfo E K and Oke O L 1988 Changes in phytate content of some tubers during cooking and fermentation (Personal communication).
McDonald R, Edwards R A and Greenhalgh J F D 1988 Animal Nutrition. Longman, London. UK. 4th edition. Pp.31-36.
Megias M D, Matiniz T A, Gallego J A and Munez S M 1993 Chemical changes during the ensiling of orange peel. Animal Feed Science and Technology 43: 269-274.
Minitab Statistical Software 1991 Rehearse 8.21. Minitab Inc., State College, P.A.
Oluremi O I A, Igyu A D and Abu F F 2005 Response of growing rabbits to dietary replacement of maize with sweet orange (Citrus sinensis) Rind. Production Agriculture and Technology 1(1): 130-136.
Oluremi O I A, Ojighen V O and Ejembi E H 2006 The nutritive potential of sweet orange (Citrus sinesis) in Broiler Production. International Poultry Science 5(7):613-617.
Price M L and Butler L G 1980 Tannin and Nutrition. Purdue University Agricultural Experimental Station. No. 272, West Lafayette, IN.
Serres H 1999 Manual of Pig production in the Tropics. CABS Publishing in Association with CTA. Biddles Ltd. Guild for Kings Lynn London: 101.
Sofowora A 1993 Medical plants and Traditional Medicine in Africa. Chichester John, Willey and Son, New York: 256.
Tacon A G J and Jackson A 1985 Utilization of conventional and unconventional protein resources in practical feed nutrition and feeding in fish.Academic Press, London, Pp. 119-145.
Trease G E and Evans W C 1989 A textbook of Pharmacognosy. Bailliene Tyndall Ltd, London: 53.
Received 22 April 2007; Accepted 6 May 2007; Published 6 July 2007