FUTURE PROSPECTS OF PEEL MEALS IN POULTRY DIETS–AN OVERVIEW

Pashu Sandesh, 09 May 2022

Dr T.Susmita, Assistant Professor, Poultry Science,

Dr C.Anil Kumar, Assistant Professor, Animal Nutrition, 

Livetstock Farm Complex,

 NTR College of Veterinary Science Gannavaram, KRISHNA DISTRICT, A.P, INDIA 521101

INTRODUCTION

Increased demand for chicken products has impacted feed supply and cost. Researchers have been interested in the possibilities of locally available, less competitive, and low-cost feed components. Several root/tuber and fruit peels have been investigated for use in poultry diets, with variable degrees of success. The inefficient use of peel meal by poultry is due to high fibre, low nutrient density, and the presence of anti-nutritional compounds. Peel meal inclusion levels in chicken diets are influenced by plant cultivar, age, agronomic practices, peel processing technique, breed, and age of birds.

The development of technologically and economically viable strategies to convert by-products, stabilisation and subsequent processing to recover some potential ingredients for use in feeds and food additives, would significantly improve the food industry's long-term sustainability and competitiveness. Pineapple peels, jackfruit rinds, and banana peels are the most common fruit peels. 

Feed availability and cost of feeds are directly affected by the increase in poultry farming. Maize, a traditional chicken energy source, is being aggressively pursued by the food and biofuel industries, resulting in restricted availability or exorbitant prices for chicken feed. Due to increased demand for broiler diets, maize prices are steadily rising. Researchers are exploring other energy sources to replace part of the maize in poultry diets. 

The peel/rind of pineapple, jackfruit, banana, watermelon, starchy roots and tubers, such as cassava and sweet potato, have been included in the poultry diets for economic reasons and nutritional demands. During the preparation of roots and tubers, as well as other fruits for culinary and industrial purposes, large volumes of peels are produced, which have a low economic value and may provide disposal issues in most producing nations. Hence, the potential for using various fruit wastes in the form of peel meal in poultry diets is summarised here.

Banana peel

Banana peels include a wide range of nutrients. Although banana peel protein content is low (1–100 g/kg), it is abundant in essential amino acids. The metabolisable energy content ranges from 2700-3300 Kcal/Kg. The crude fibre content of the peel varies between 149 and 500 g/kg. High quantities of macro-and microminerals, crude fat, and polyunsaturated fatty acids are also found in banana peels (especially linoleic and -linolenic acid).

Polyphenols including gallocatechin and dopamine have been found in the banana peels. Few studies have shown a gallocatechin concentration of 160 mg/100 g dry weight of banana peel and these Catechins have antimicrobial, antioxidant, and cholesterol-lowering effects. Feeding banana peels reduces total cholesterol, LDL cholesterol, and VLDL cholesterol. The principal anti-nutritional component in banana peel has been identified as tannins.

Cassava peel

Cassava peel has a lot of fibre, ranging from 140 to 340 g/kg, with non-starch polysaccharides accounting for the majority of it. Cassava peel has been reported to contain 680–700 g/kg of soluble sugar and 3–20 g/kg of crude fat, respectively. Cassava peel meal has a low-calorie value due to its low fat and high fibre content. Another difficulty that prevents the efficient use of cassava peel meal as chicken feed is dustiness, which may be mitigated by adding fat to the diet. Cassava root products are deficient in carotene and carotenoids, hence supplements containing these pigments must be added to cassava root product diets to keep egg yolk and broiler skin colours consistent.

Citrus peel 

Citrus peel is a waste product of the citrus industry. The fruit's peel is an edible component that is high in nutrients such as vitamin C, essential oils including terpenes and aliphatic sesquiterpene, and dietary fibre. They also have carotenoids, organic acids (citric acid and ascorbic acid), minerals, and a variety of active phytochemicals (coumarins and flavonoids such as naringin, naringenin, hesperidin, neohesperidin, rutin, hesperetin, nairutin, and tangeretin; that aid in antibacterial, insecticidal, disinfecting activities, anti-inflammatory and anticarcinogenic properties. Though citrus peel is having low crude protein per cent of 5.46-6.4, it is used in the poultry diets for its other phytochemical properties. 

Onion peel

Onion peel is a by-product of the vegetable processing industry that is high in dietary fibre and polyphenolic antioxidants, particularly quercetin and flavonoids. These flavonoids help to prevent oxidative stress, which is a risk factor for cardiovascular and neurological illnesses. The antioxidant, anti-inflammatory, antibacterial, and anticarcinogenic properties of onion flavonoids are well-known. 

Papaya peel

Papaya (Carica papaya) peel has a protein composition similar to maize, however, it is higher in fibre and lowers in fat. Papaya peel is similar to most fruit peels in terms of soluble carbohydrate content. Papaya is strong in proteolytic enzymes (papain and chymopapain), as well as vitamins, minerals, and beta-carotene. Antihelmintic, antibacterial, and anticoccidial effects of papaya peel are assumed to be due to the presence of polyphenols, particularly catechins. The antinutritive compounds in papaya peel are phenolic substances such as tannins, alkaloids, saponins, and flavonoids. 

Sweet potato peels

The sweet potato peel (Ipomoea batatas L) has a lot of calories, moderate crude protein 36–46 g/kg, crude fibre 38–70 g/kg and Metabolizable energy was found to be around 2700 kcal/kg. Sweet potato peels are abundant in carotenoids, they reduce the need for pigment supplements to keep egg and skin colour consistent. 

Depending on the cultivar, sweet potatoes have been shown to possess phenolic compounds and protease inhibitors in varying levels. The composition of sweet potato products is influenced by soil water level, physiological properties, storage conditions.

Yam yam

Peeled yam Yam (Dioscorea rotundata) is an average source of energy, with a metabolisable energy level of approximately 2,700 kcal/kg. The crude protein content of yam peel is equivalent to that of most cereal grains estimated to be between 91.4 and 127 g/kg, with a decent balance of important amino acids. Yam peel has been shown to have a high starch content and digestibility. Yam peel, like cassava, is a poor source of carotenoids.

The nutritional and anti-nutrient contents of selected root and fruit peels are mentioned in Tables 1 and 2, respectively. The dietary inclusion of the fruit peels is mentioned in Table 3

 

Table 1 Nutrient contents of root and fruit peels

Nutrient

Cassava peel

Yam peel

Sweet potato peel

Citrus pulp

Banana peel

Papaya peel

Sugar beet pulp

Crude protein

38

 (32-44)

109.2

(91.4–127)

41.2 

(36–46.4)

68 

(62–74)

50.5 

(1.0–100)

87.5 

(68.9–106)

96

Crude fibre

230 

(120–340)

89.5 

(84–95)

54 

(38–70)

129 

(123–135)

228.5 

(140–317)

213.6

 (96.7–330.5)

190

Crude fat

18.2 

(3.4–33)

6 

(10–12)

80.5 

(41–120)

45.5

 (37–71.9)

65 

(48–82)

13.4

 (2.3–24.4)

14.5

Ash

57.7 

(14.4–101)

83 

(68–98)

52.8 (45.6–60)

64.5 

(47–81.9)

174.5 

(163–186)

75

 (31.5–118.5)

55.1

MORE

710

712.5 

(683–742)

735 

(720–750)

636.5 

(627–646)

393

644

549.5

ME (Kcal/kg)

2686

3000

2930

2724

2790

1530

700

 

Table 2 Anti-nutritional factors in selected root and fruit peels/pulps

Antinutrients

Cassava peel

Yam peel

Sweet potato peel

Citrus pulp

Banana peel

Papaya peel

Cyanogenic glucoside

**

Phenolic compounds

**

**

**

**

**

Alkaloids

**

Phytate

*

Protease inhibitors

*

*

**

Amylase inhibitors

*

Oxalate

**

Saponins

*

(**major factor; *reported; –not analysed)

 

Table 3. Recommendations of selected peels/pulps in broiler diets

 

Peel meal

Inclusion level

Processing

References

Cassava

270 g/kg diet

Sun-dried

Tewe and Egbunike (1992)

 

200 g/kg diet

Sun-dried

Obioha et al. (1984)

 

200–300 g/kg diet

Parboiled

Salami (2000), Salami and

 

 

 

Odunsi (2003)

Yam

200 g/kg diet—laying quails

Sun-dried

Edache et al. (2012)

Sweet potato

200 g/kg diet

Sun-dried

Apata and Babalola (2012)

 

190 g/kg diet—laying quails

Sun-dried

Edache et al. (2016)

Sugar beet pulp

23g/kg—Japanese laying quails

Sun-dried

Pettersson and Razdan (1993)

Citrus

100 g/kg diet

Sun-dried

Yang and Chung (1985)

 

50–120 g/kg diet

Sun-dried

Mourao et al. (2008), Nazoket al. (2010)

Onion peel meal

20g/kg diet

Sun-dried

An BK et al. (2015), Adeymi KD et al. (2021)

Papaya

90 g/kg diet—growing pullets

Sun-dried

Fouzder et al. (1999)

 

Peels in the Future

Peels are nutritionally moderate, making them a good supplement to poultry diets. This, together with advancements in processing technology to reduce anti-nutritive components, would increase the value of peels in chicken feed.  Peels will be easily accessible if correctly processed and conserved.

Due to the growing market and availability of feed additives (exogenous enzyme products, amino acids, antioxidants, anti-nutrient binding agents) and feed industry research interest in probiotics, the future use of peels appears to be brighter. 

Alternative, less expensive components for chicken feeding should be researched in order to reduce food-feed competition. Increased production of root/tuber and fruit crops to meet increased global demand for food and industrial applications, as well as ongoing research into higher yields and planting and harvesting time flexibility, will make their peel more available year-round. Seasonality in availability, high fibre content, and the presence of antinutrients are all factors that make it difficult for poultry to effectively consume peels. The high moisture content of peels makes processing much more difficult in humid tropical environments where these by-products are widely available.

Peel meals' future application in on-farm chicken feed production is brighter because of the rising market and availability of feed additives (exogenous enzyme products, amino acids, antioxidants, antinutrients binding agents) and feed industry research interest in probiotics. 

Dietary adjustments, such as complementing meals with suitable exogenous enzyme preparations, have been shown to reduce the negative effects of NSPs, according to studies. Enzymes can be employed to target antinutrients in certain feed components, allowing chickens to absorb more nutrients from the meal and hence improve feed efficiency. Because of increased feed efficiency and bird uniformity, adding enzymes to fibrous diets improved litter quality while reducing feed expenditures. There are presently several complex enzymes, each of which targets specific elements in the meal, resulting in improved nutritional availability, as opposed to single enzyme activity. These enzyme products might be used to boost the usage of peel meals while also lowering feed costs.

Conclusion

Peels use in chicken diets is restricted due to high fibre and anti-nutritional component concentrations. Increased affordability of commercial feed additives such as enzyme cocktails will assist poultry in making better use of these by-products. More study on feed systems that optimise hen peel utilisation, save feed costs and may reduce environmental concerns is required.

 

References

Alagawany, M., & Attia, A. (2015). Effects of feeding sugar beet pulp and avizyme supplementation on performance, egg quality, nutrient digestion and nitrogen balance of laying Japanese quail. Avian Biology Research8(2), 79– 88. https://doi.org/10.3184/175815515X14274754281188

Anhwange, B. (2008). Chemical composition of Musa sapientum (banana) peels. Journal of Food Technology6(6), 263– 266.

Apata, D. F., & Babalola, T. O. (2012). The Use of cassava, sweet Potato and cocoyam, and their by-products by non-ruminants. International Journal of Food Science and Nutrition Engineering2(4), 54– 62. https://doi.org/10.5923/j.food.20120204.02

Aro, S. O., Aletor, V. A., Tewe, O., & Agbede, J. O. (2010). Nutritional potentials of cassava tuber wastes: A case study of a cassava starch processing factory in south-western Nigeria. Livestock Research for Rural Development22(11), Article #213. http://www.lrrd.org/lrrd22/11/aro22213.htm

Bokanga, M. (1994). Processing of cassava leaves for human consumption cassava safety. Acta Horticulturae375, 203– 207. https://doi.org/10.17660/ActaHortic.1994.375.18

Bruinsma, D. H., Witsenburg, W. W., & Wurden, W. (1983) Selection of technology for food processing in developing countries. Publication of the International Course in Food Science and Nutrition. Wageningen, The Netherlands: Centre for Agricultural Publishing and Documentation.

Cadavid, L. F., El-Sharkawy, M. A., Acosta, A., & Sanchez, T. (1998). Longterm effects of mulch, fertilization and tillage on cassava grown in sandy soils in northern Colombia. Field Crops Research57, 45– 56. https://doi.org/10.1016/S0378-4290(97)00114-7

Camilla Govoni, Davide Danilo Chiarelli, Alice Luciano, Matteo Ottoboni, Simge Nur Perpelek, Luciano Pinotti, Maria Cristina Rulli, Global assessment of natural resources for chicken production, Advances in Water Resources, 10.1016/j.advwatres.2021.103987, 154, (103987), (2021).

Cardoso, A. P., Estevao, M., Mario, E., Fernando, M., Julie, C., & Haque, M. R. (2005). Processing of cassava roots to remove cyanogens. Journal of Food Composition and Analysis18, 451– 460. https://doi.org/10.1016/j.jfca.2004.04.002

Carrol, K. K., Kurowska, E. M., & Guthrie, N. (1999). Use of citrus limonoids and flavonoids as well as tocotrienols for the treatment of cancer. International Patent WO 9916167.

Dairo, F. A. S. (2011). Utilization of ensiled metabolizable mixture of cassava peel and caged layers’ manure as energy source in broiler diets. African Journal of Food, Agriculture Nutrition and Development11(5), 5110– 5124.

Dayal, A. D., Diarra, S. S., Lameta, S., Devi, A., & Amosa, F. (2018). High cassava peel meal-based diets with animal fat and enzyme for broilers. Livestock Research for Rural Development30(6), 99.

Diarra, S. S. (2015). Response of Growing Pullets to Cassava Copra Meal-based Diets Supplemented with Exogenous Enzyme and Essential Amino Acids in Samoa. Malaysian Journal of Animal Science18(1), 67– 76.

Diarra, S. S., Igwebuike, J. U., Kwari, I. D., Sinodo, S., Babangida, A., Ahmadu, U., … Jibrin, M. (2012). Evaluation of yam-sweet potato peels mixture as source of energy in broiler chicken diets. ARPN Journal of Agriculture and Biological Sciences7(7), 497– 502.

Diarra, S. S., Sandakabatu, D., Perera, D., Tabuaciri, P., & Mohammed, U. (2014). Growth performance, carcass measurements and organs weight of broiler chickens fed cassava copra meal-based or commercial finisher diets in Samoa. Asian Journal of Poultry Science8, 16– 22. https://doi.org/10.3923/ajpsaj.2014.16.22

Diarra, SS. Peel meals as feed ingredients in poultry diets: Chemical composition, dietary recommendations and prospects. J Anim Physiol Anim Nutr. 2018; 102: 1284– 1295.

Donado-Pestana, C. M., Salgado, J. M., de Oliveira Rios, A., dos Santos, P. R., & Jablonski, A. (2012). Stability of carotenoids, total phenolics and in vitro antioxidant capacity in the thermal processing of orange-fleshed sweet potato (Ipomoea batatas Lam.) Cultivars grown in Brazil. Plant Food for Human Nutrition67, 262– 270. https://doi.org/10.1007/s11130-012-0298-9

dos Santos, C. M., de Abreu, C. M. P., Freire, J. M., Queiroz, E. R., & Mendonça, M. M. (2014). Chemical characterization of the flour of peel and seed from two papaya cultivars. Food Science and Technology (Campinas)34(2), 353– 357. https://doi.org/10.1590/fst.2014.0048

Duwa, H., Saleh, B., Lamido, M., & Saidu, A. (2014). Growth, haematological and serum biochemical indices of broiler chickens fed banana peel meal as replacement for maize in the semi-arid zone of Nigeria. Journal of Animal Feed Research4, 121– 126.

Edache, J. A., Tuleun, C. D., Yisa, A. G., & Muduudtai, R. U. (2016). Replacement value of sweet potato (Ipomea batatas) peel meal for maize on short term laying performance of Japanese quails (Coturnix japonica)International Journal of Scientific and Applied Research1(1), 77– 81.

Edache, J. A., Yisa, A. G., & Okpala, E. J. (2012). Effects of replacing maize with yam peel on short term laying performance of Japanese quails (Coturnix coturnix japonica). Pakistan Journal of Nutrition11(7), 614– 617.

Eggum, O. L. (1970). The protein quality of cassava leaves. British Journal of Nutrition24, 761– 769. https://doi.org/10.1079/BJN19700078

FAO (2013). Food and Agriculture Organization of the United Nations, Statistical Database FAOSTAT. http://faostat.fao.org/; (accessed 14. 12.14).

Farahat, M., Abdallah, F., Abdel-Hamid, T., & Hernandez-Santana, A. (2016). Effect of supplementing broiler chicken diets with green tea extract on the growth performance, lipid profile, antioxidant status and immune response. British Poultry Science57(5), 714– 722.

Faramarzi, M., Lashkarboloki, M., Kiaalvandil, S., & Iranshahi, F. (2012). Influences of Different Levels of Sweet Potato Peels on Growth and Feeding Parameters and Biochemical Responses of Cyprinus carpio (Cyprinidae). American-Eurasian Journal of Agriculture and Environmental Sciences12(4), 449– 455.

Fouzder, S. K., Chowdhury, S. D., Howlider, M. A., & Podder, C. K. (1999). Use of dried papaya skin in the diet of growing pullets. British Poultry Science40(1), 88– 90. https://doi.org/10.1080/00071669987881

Friedman, M. (2007). Overview of antibacterial, antitoxin, antiviral and antifungal activities of tea flavonoids and teas. Molecular Nutrition and Food Research51, 116– 134. https://doi.org/10.1002/(ISSN)1613-4133

Funmilayo, S. M., & Ayodele, A. E. (2011). Effect of replacement of yam (Dioscorea spp) peel meal for maize (Zea mays) on growth performance, carcass characteristics and blood chemistry of finisher broilers. Journal of Agriculture and Biological Sciences2(1), 18– 21.

G K Duskaev, S G Rakhmatullin, G I Levahin, Effect of Quercus cortex extract on carcass and meat quality traits of broilers, IOP Conference Series: Earth and Environmental Science, 10.1088/1755-1315/624/1/012161, 624, 1, (012161), (2021).

Gohl, B. (1982). Les aliments du betail sous les tropiques. Roma, Italy: FAO, Division de Production et Santé Animale.

Gramza, A., Korczak, J., & Amarowicz, R. (2005). Tea polyphenols- their antioxidant properties and biological activity – a review. Polish Journal of Food and Nutrition Sciences14(55), 219– 235.

Islam, S. N., Nusrat, T., Begum, P., & Ahsan, M. (2016). Carotenoids and β-carotene in orange fleshed sweet potato: A possible solution to vitamin A deficiency. Food Chemistry199, 628– 631. https://doi.org/10.1016/j.foodchem.2015.12.057

Lin, Y. H., Huang, T. C., & Huang, C. (1988). Quality improvement of sweet potato (Ipomoea batatas L. Lam) roots as feed by ensilage. British Journal of Nutrition60(1), 173– 184. https://doi.org/10.1079/BJN19880086

Maeda-Yamamoto, M., Kawahara, H., Tahara, N., Tsuji, K., Hara, Y., & Isemura, M. (1999). Effect of tea polyphenols on the invasion and matrix metalloproteinases activities of human fibrosarcoma HT1080 cells. Journal of Agricultural and Food Chemistry47, 2350– 2354. https://doi.org/10.1021/jf9811525

Makkar, H. P. S., Francis, G., & Becker, K. (2007). Bioactivity of phytochemicals in some lesser-known plants and their effects and potential applications in livestock and aquaculture 

Martillotti, F., Bartocci, S., & Terramoccia, S. (1996). Guida all'alimentazione dei ruminanti da latte. Rome, Italy: INEA.

Martinez-Pascual, J., & Fernandez-Carmona, J. (1980). Citrus pulp in diets for fattening lambs. Animal Feed Science and Technology5, 11– 22. https://doi.org/10.1016/0377-8401(80)90006-1

Mateos, G. G., Jiménez-Moreno, E., Serrano, M. P., & Lázaro, R. P. (2012). Poultry response to high levels of dietary fibre sources varying in physical and chemical characteristics. The Journal of Applied Poultry Research21(1), 156– 174. https://doi.org/10.3382/japr.2011-00477

Medoua, G. N., Lape Mbome, I., Agbor-Egbe, T., & Mbofung, C. M. F. (2007). Antinutritional factors changes occurring in trifoliate yam (Dioscorea dumetorum) tubers after harvest. Food Chemistry102, 716– 720. https://doi.org/10.1016/j.foodchem.2006.06.005

Midau, A., Augustine, C., Yakubu, B., Yahaya, S. M., Kibon, A., & Udoyong, A. O. (2011). Performance of broiler chicken fed enzyme supplemented cassava peel meal based diets. International Journal of Sustainable Agriculture3(1), 1– 4.

Moghazy, M. E. S. E., & Boushy, A. E. (1982). Some neglected poultry feedstuffs from vegetable and fruit wastes. World's Poultry Science Journal38(01), 18– 27. https://doi.org/10.1079/WPS19820002

Mokbel, M. S., & Hashinaga, F. (2004). Effect of heat, calcium chloride and modified atmosphere on the shelf life of banana fruits. Food Preservation Science30, 179– 184.

Morgan, N. K., & Choct, M. (2016). Cassava: Nutrient composition and nutritive value in poultry diets. Animal Nutrition2, 253– 261. https://doi.org/10.1016/j.aninu.2016.08.010

Mourao, J. L., Pinheiro, V. M., Prates, J. A. M., Bessa, R. J. B., Ferreira, L. M. A., Fontes, C. M. G. A., & Ponte, P. I. P. (2008). Effect of dietary dehydrated pasture and citrus pulp on the performance and meat quality of broiler chickens. Poultry Science87, 733– 743. https://doi.org/10.3382/ps.2007-00411

Nagarajaiah, S. B., & Prakash, J. (2011). Chemical composition and antioxidant potential of peels from three varieties of banana. Asian Journal Food and Agro-industry4, 31– 46.

Nazok, A., Rezaei, M., & Sayyahzadeh, H. (2010). Effect of different levels of dried citrus pulp on performance, egg quality, and blood parameters of laying hens in early phase of production. Tropical Animal Health and Production42(4), 737– 742. https://doi.org/10.1007/s11250-009-9481-x

Negesse, T., Makkar, H. P. S., & Becker, K. (2009). Nutritive value of some non-conventional feed resources of Ethiopia determined by chemical analyses and an in vitro gas method. Animal Feed Science and Technology154, 204– 217. https://doi.org/10.1016/j.anifeedsci.2009.09.010

Ngiki, Y. U., Igwebuike, J. U., & Moruppa, S. M. (2014). Utilisation of cassava products for poultry feeding: A review. International Journal of Science and Technology2(6), 48– 59.

NRC (2012). Nutrient requirements of swine, 11th revised ed. Washington, DC: National Academy Press.

Obioha, F. C., Azubuike, G. O., Ene, L. S. O., Okereke, H. E., & Okoli, O. O. (1984). The effect of partial replacement of maize with cassava peel on layer performance. Nutrition Report International30, 1423– 1429.

Odunsi, A. A., Onifade, A. A., & Oyewole, S. O. (2001). Utilization of cassava peel meals with or without sheabutter fat in diets of egg-type chickens. Indian Journal of Animal Science20, 31– 36.

Ogbo, F. C. (2006). Assessment of some locally developed technologies for shortening the retting time of cassava. African Journal of Biotechnology5, 775– 777.

Ojabo, L. D., Oluremi, O. I. A., & Uza, D. V. (2014). Effect of feeding sun-dried sweet orange (Citrus sinensis) fruit peel on pullet chick performance. Research Opinions in Animal and Veterinary Sciences4(9), 484– 488.

Omole, A. J., Ayodeji, I. O., & Raji, M. A. (2004). The potential of peels of mango, plantain, cocoyam and pawpaw as diets for growing snails (Archachatina marginata). Livestock Research for Rural Development16, 102.

Onyimonyi, A. E., & Ugwu, S. O. C. (2007). Bioeconomic indices of broiler chicks fed varying ratios of cassava peel/bovine blood. International Journal of Poultry Science6(5), 318– 321. https://doi.org/10.3923/ijps.2007.318.321

Osagie, A. U. (1992). The yam tuber in storage (pp. 107– 173). Benin City, Nigeria: Post-Harvest Research Unit, University of Benin.

Oyebimpe, K., Fanimo, A. O., Oduguwa, O. O., & Biobaku, W. O. (2006). Response of broiler chickens to cassava peel and maize offal in cashew nut meal-based diets. Archivos de Zootecnia55, 301– 304.

Ravindran, G., & Ravindran, V. (1988). Changes in the nutritional composition of cassava (Manihot esculenta Crantz) leaves during maturity. Food Chemistry27, 299– 309. https://doi.org/10.1016/0308-8146(88)90014-3

Ravindran, V. (1991). Preparation of cassava leaf products and their use as animal feeds. In D. Machin & S. Nyvold (Eds.), Roots, Tubers, plantain and bananas in animal feeding, Vol. 95 (pp. 111– 125). Rome, Italy: Food and Agriculture Organisation.

Ravindran, V. (2011). Poultry feed availability and nutrition in developing countries-advances in poultry nutrition. Rome, Italy: Food and Agriculture Organization. Retrieved from http://www.fao.org/docrep/013/al707e/al707e00.pdf