Feed selection and growth performance of local chickens offered different carbohydrate sources in fresh and dried form supplemented with protein-rich forages

Kong Saroeun

Center for Livestock and Agriculture Development,

PO. Box 2423, Phnom Penh 3, Cambodia
saroeunkb@celagrid.org

3. General discussion

3.1 Small scale poultry production in developing countries

Poverty, hunger and malnutrition are common among smallholder families in developing countries. Most poor people rely on agricultural work to support their families. Evaluation reports from a number of integrated development projects in developing countries indicated that scavenging village chickens play a significant role in poverty alleviation and enhancing gender equity among the disadvantaged communities (Saleque 1996). Alders et al (2009a) also reported that village chickens play an important role in poverty alleviation and HIV/AIDS mitigation. Backyard chicken raising in villages continues to provide a fairly substantial proportion of the domestic meat consumption, although commercial poultry production has become a successful and highly competitive enterprise. About 90-95 % of the rural households in developing countries raise some indigenous chickens, ranging from 5-50 birds per household, and these chickens offer a short term or current savings account for daily petite cash needs (Chantalakhana and Skunmun 2002, CelAgrid 2006). Chicken production becomes part of the whole farming system. The type of chickens kept and managed is highly influenced by various biological, cultural, social and economic factors. In most developing countries chickens scavenge within the village boundaries. Their nourishment depends on the feed available in the village, their health and the local disease situation. Village chicken improvement programs also have the potential to contribute to each of the development goals and to improve the situation of the most vulnerable families in developing countries (Ahlers et al 2009b).

In Cambodia, the village chicken has an important role for supplying meat for the provincial town and city markets, and the meat is usually preferred by local food processors, such as local restaurants, and street grills sellng roasted chicken. According to Asia DHRRA (2008), 11 tonnes of chicken meat per day are supplied and consumed in Phnom Penh City. About 80% are free range chickens raised by smallholder farmers, and 20 % comes from farming entrepreneurs who use modern technology (standard housing and management) and concentrate feed. This production is considered as a part of small farmers’ income generation, because this activity does not require as much time and effort as to take care of other livestock. The farmers just give some locally available feeds, such as paddy rice, rice bran, broken rice, termites, water spinach or kitchen waste after or before freeing their chickens to scavenge for more feed (CelAgrid 2006). Besides their own household consumption, the small farmer is able to supply chickens for sale, on average 4 times and in total 100 head per year (Asia DHRRA 2008).

3.2 Feed preferences and the cafeteria system for poultry

The method of cafeteria or free-choice feeding of poultry offered a selection of different feed ingredients was first recognized more than 50 years ago (Winter and Funk 1951) and was popular before knowledge regarding formulation of complete diets had reached its present high standard. This method gives the birds the opportunity to select nutrients, particularly protein and energy, according to their physiological demands (Emmans 1978). Related to the expenditure, the use of this feeding system may thus reduce feed processing costs, for example for grinding, mixing and many of the handling procedures associated with mash production which are in fact unnecessary (Kiiskinen 1987; Tauson et al 1991). An additional advantage is that each bird is able to select the optimum amount of each of the components to satisfy its own nutrient requirements and the consequent increase in efficiency would represent additional savings (Emmans 1979; Hearn 1979; Belyavin 1994). Pousga et al (2005) reported that free choice feeding is an infinitely more natural and delicate system of feeding. Each bird can accurately select its balance of nutrients to meet its particular physiological requirement. As long as the hens are given the opportunity to make clear and easy nutritional choices, they will be healthy and productive. Okitoi et al (2009) reported similarly that scavenging chickens given access to a cafeteria feeding system consumed diverse scavengeable food resources, that can be grouped into animal, vegetable, sand-grit and the components of animal origin that contribute essential amino acids (eg: lysine, tryptophan, methionine and cystine) to the diet. Those of vegetable origin contributed more energy, and while feeding on a range of animal and vegetable components, the appetite for essential amino acids seems to drive scavenging chicken preferences. The farmer may prefer the practice of this system because they could have access to cheap cereal grains and suitable protein concentrate sources to mix on farm (Tauson et al 1991), as well as locally available green forages, and thus have no need of a grinding machine.

3.3 Green forages for local chickens

Green forages have a great potential and role in the nutrition of all kinds of animals raised by small farmers in rural areas, especially for ruminants. The products (eg. duckweed, water spinach) and byproducts (eg. cassava leaf, taro leaf and sweet potato leaf) from the green forages are locally available and have low cost for farmers to use as feeds for animals. Moreover, they are also a good source of nutrients (Table 1 and 2), including protein, vitamins and minerals. Village chickens prefer to consume them during scavenging, and as reported by Okitoi et al (2009) green vegetables and grass are often found in the crop contents of these chickens.

3.3.1 Duckweed (Lemna spp)

Duckweed is a group of small floating aquatic plants found in natural ponds, lakes and flooded rice fields. It can be grown to recycle nutrients from waste water and it provides a good source of proteins and can be utilized for the production of certain products, such as animal feed and fuel ethanol (Cheng and Stomp 2009). This plant grows rapidly and gives high yields with high protein content, low fiber content and high mineral content. Moreover, it is non-toxic and is only attacked by a few known pests. The annual dry matter (DM) yield of duckweed is 10-30 t/ha (Huque 1998).

Chemical composition and utilization of duckweed in chicken diets

Duckweed has high nutritional value and high productivity (Hillman and Culley 1978) but the crude protein content of duckweeds depends mainly on the N content of the water upon which they grow, and there are also some variations in amino acid content of duckweed proteins. Moreover, duckweed has less cell wall materials than other aquatic plants. The crude protein content of duckweed can be as high as 39.3 % in dry basis (Bui Xuan Men et al 1996) and is rich in essential amino acids. So, there is a good prospect of using duckweed as a protein source for poultry. 

Recent studies have demonstrated that replacing a protein source with duckweed meal in conventional diets for young broiler chickens can retard chicken growth as its inclusion levels increases (Haustein et al 1992b, 1994), whereas layers still produced efficiently (Haustein et al 1988) and older broiler birds had excellent growth characteristics when fed relatively high levels of duckweed meal. Skillicorn et al (1993) reported that duckweed meal can be fed to layers at up to 40% of total feed with satisfactory results. This indicates that duckweed of known chemical composition can be used in least-cost ration formulations for both poultry meat and egg production. However, the lower growth performance of local chickens fed on duckweed is not a big issue for smallholder farmers, as their aim is not the maximization of growth but optimum economic returns.

3.3.2 Water spinach (Ipomoea aquatica)

Water spinach is the most common plant species grown in wetlands in terms of aquatic vegetable production. This production requires relatively easy growing techniques with lower labor costs compared to other cultivated plants. In Cambodia, besides growing on inland waterways, this aquatic plant is commonly cultivated all year round in the surrounding wetlands or in the lakes around Phnom Penh where it is used to treat the urban domestic wastewater. It is a primary source of nutrients (Khov Kuong et al 2007) because it has high potential to convert efficiently the nitrogen in the effluent into edible biomass with high protein content (Kean Sophea and Preston 2001). Water spinach is usually consumed by both people and animals. It is also easily available, growing naturally in ponds, flooded fields and lagoons, and is more abundant in the rainy season. There are two types of water spinach, aquatic and inland varieties, commonly cultivated by farmers. Stems are commonly used as planting materials for the aquatic variety while commercial seeds as used for the inland variety. When water is not a constraint, the aquatic water spinach has the capacity to produce foliage for longer periods.

Chemical composition and utilization of water spinach in chicken diets         

Water spinach is a good source of protein and can be used as feed for all kinds of animal and for humans. The foliage contains protein in the range of 23.6 % in dry season and 27.6 % in wet season (Nguyen Nhuy Xuan Dung 1996) and is also a good source of trace minerals (mg/kg): Zn, 5.03; Mn, 22.2; Cu, 1.37 and Fe, 75.3 (NIAH, 1995) and is rich in vitamins A and C. The nutrients concentrate mainly in the leaves. Umar et al (2007) reported that the mineral element contents in the leaves were high with remarkable concentrations of K and Fe. Also the leaves contain moderate concentrations of Na, Ca, Mg and P, with low Cu, Mn and Zn contents.

In rural regions, water spinach is commonly used by smallholders to feed to their scavenging poultry as a supplement mixed with rice bran. Using water spinach for local chickens indicates that it is also the preferred foliage to provide protein and vitamins for growing chickens (Experiment 1). Nguyen Thi Thuy and Brian Ogle (2004) reported that when chickens had access to the green feeds such as water spinach or duckweed, the color of the skin and the egg yolk were improved, which makes the products more attractive to consumers.

3.3.3 Taro leaf (Colocasia esculenta)

In Cambodia, taro can be found in most parts of the country, particularly along the Great Lake and Mekong River. Farmers grow taro for its edible corms (root) and vegetable stems. The yield of the corms and foliage is high. Taro leaf which is not used as human feed can be a potential protein source for animals due to the good nutritional quality of the leaves. FAO (1993) reported that taro leaf (in DM basis) has 25.0% crude protein, 12.1% crude fiber, 1.74% Ca and 0.58% P, and thus  can be a good alternative feed for village chickens. 

Chemical composition and utilization of taro leaf in chicken diets

The taro leaf is rich in protein, with about 23% crude protein on a dry weight basis. It is also a rich source of calcium, phosphorus, iron, vitamin C, thiamine, riboflavin and niacin, which are important constituents of human and animal diets. The fresh taro lamina (leaf) has about 20% dry matter, while the fresh petiole has only about 6% dry matter (Onwueme 1999). According to Rodriguez et al (2006), fresh leaves of Xanthosoma sagittifolium (a member of the taro family) contain 24.8 % crude protein. Leterme et al (2005) also reported that Xanthosoma leaf had high amino acid content and a good balance of amino acids.

In rural areas, people usually use taro leaves for food by boiling or preparing in various ways and mixing with other condiments. In the coastal zone of Cambodia, taro leaves after cooking are used by smallholders as extra feed for their scavenging pigs (Kong Saroeun et al 2007). Until now, there seems to be no research on the use of taro leaf for poultry, and a recent study demonstrated that using fresh chopped taro leaf for chicken had a negative effect on the intake of the birds (Experiment 1) because they did not eat the leaves, probably due to the high calcium oxalate content in the fresh leaf. 
 

Anti-nutritional factors in taro leaf

The leaves of taro are rich in protein but contain calcium oxalate, which appears to be a limiting factor for its use as animal feed (Tiep et al 2006). Savage and Dubois (2006) reported that the soluble oxalate content of the raw leaves was 236 mg oxalate/100 g fresh matter. This soluble oxalate content can be reduced by soaking or cooking. Soaking for 18 h can reduce the soluble oxalate content by 26%. During the soaking treatment the insoluble oxalate (calcium oxalate) content of the leaves remained constant (mean 171 mg oxalate/100 g wet matter). Boiling the leaves resulted in a 36% loss of soluble oxalates, while the soluble oxalate content of baked tissue was very similar to the raw tissue. The mean insoluble oxalate content of the raw, boiled and baked tissue was 226 mg oxalate/100 g fresh matter. Overall, boiling the taro leaves was shown to be an effective way of reducing the soluble oxalate content of the tissue. Besides, calcium oxalate content in taro leaf can also be reduced by sun-drying and ensiling as reported by Pheng Buntha (2008) and these processes reduced calcium oxalate from 3.08 % in DM in the fresh leaf to 1.1 % after sun-drying and 0.11 % after ensiling. 

3.4 Carbohydrate feeds for local chicken

In chickens, energy is required in varying amounts for all metabolic purposes, so a deficiency of energy affects most aspects of  the productive performance of poultry. If the available energy concentration of the diet is changed, birds maintain constant energy intakes by changing their feed intakes (Rose 1997). Therefore, energy feed is required for chickens for supporting activities during scavenging and for productive performance. Locally available resources are useful as energy feed when they are abundant and inexpensive.

3.4.1 Cassava root (Manihot esculenta Crantz)

In developing countries, especially in the rural areas, farmers grow cassava as a subsistence crop and use it as the main source of their food and as livestock feed,  as well as a source of cash income. However, cassava yields might be low in traditional systems because of the shortage of high yielding varieties and the use of inappropriate agronomic techniques. In Cambodia, the production, yield and harvested areas of cassava are low compared to the other Asian countries. Generally, the harvesting period of cassava is 6-8 months after planting, and without fertilization yields of cassava range from 4-6 tons/ha (Khieu Borin and Frankow-Lindberg 2005). Normally, the crop has a high yield potential and can withstand poor soil and drought, and yields are 25 to 60 tons/ha, depending on variety and cultivation practice (FAO 2008).

Chemical composition and utilization of cassava root in chicken diets

Cassava root is rich in energy, with a little ascorbic acid, but is low in fat, minerals, other vitamins, and especially proteins. The carbohydrate of cassava is an excellent digestible starch. In cassava root, amino acids are not balanced. Several sulfur-containing amino acids are limiting and excess arginine contributes to the imbalance (Silvestre & Arraudeau 1983). Normally, fresh cassava roots are fed to cattle and pigs, either raw or in the boiled form. However, feeding fresh roots may cause cyanide toxicity, depending on the cyanide content in the roots (Mathur et al 1969). For storage, as well as when feeding to poultry, it is advisable to dry it and bring down the moisture level to about 10%. Cassava has been used as animal feed in the fresh form or dried. In the semitropical zone, whole or peeled cassava is often offered to sheep, goats and pigs. In small scale pig or poultry raising, it is used fresh or boiled and mixed with other products such as maize, sorghum and broken rice (Silvestre & Arraudeau 1983).

Anti-nutritional factors in cassava root

Whole fresh cassava root contains cyanogenic glycosides of two types, primarily linamarin (93%) and some lotaustralin (7%). Linamarin is chemically similar to glucose but is converted to cyanide (ion) in the presence of linamarase, a naturally occurring enzyme in cassava. Linamarin in cassava can vary from 2 to 395 mg/100 kg of fresh cassava root, depending on the variety (Yeoh and Yruong 1993). In the whole plant, both linamarin and lotaustralin are synthesised from the amino acids.

            L-valine    ---------------------------------------->   Linamarine

            L-isoleucine   ------------------------------------->   Lotaustraline

           Cyanogenic glucoside  ---------------- ^{Linamarase --->}  Glucose  +  Aglycon

           Aglycon  ----------------------^{Hydroxynitrilyase-------->}  HCN + Aldehyde or Acetone

Fresh cassava root contains 0.44 mg HCN/g (Udedibie et al 2004), while the meal form contains less than 40 mg/kg and can be fed to broiler chicks at 500 g/kg without any adverse effects (Panigrahi et al 1992). A later study by Panigrahi (1996) suggested that low-cyanide cassava root meals may be incorporated in nutritionally-balanced poultry diets at between 500 and 600 g/kg without any reduction in weight gain or egg production. However, an excess of cyanide content at 100 mg/kg diet appeared to adversely affect broiler performance, and laying hens may be affected by levels as low as 25 mg total cyanide/kg diet (Panigrahi 1996).

3.4.2 Sweet potato tuber (Ipomoea batatas (L.) Lam)

Sweet potato tubers are grown in many places by rural smallholders in order to obtain starchy tubers for food and some cash. The small tubers and leftovers from selling in local markets are an alternative for feeding to animals such as pigs and poultry. The remaining foliage from harvesting the tubers can also be used as a protein feed for all kinds of animal. The productive potential of sweet potato tubers can reach from 24 to 36 t/ha/crop of roots (Morales 1980) and the foliage production can vary from 4.3-6 t DM/ha/crop (Ruiz et al 1980). 

Chemical composition and utilization of sweet potato tuber in chicken diets

The main nutritive component in sweet potato is its starch content, and it is also a source of vitamins. Sweet potato tubers have a low content of protein, fat and fiber, but the high nitrogen free extract fraction in the tuber is indicative of its potential value as an energy source. Carbohydrates in sweet potato tubers generally make up between 80-90% of the dry weight of the roots. However, the uncooked starch of the sweet potato is very resistant to hydrolysis by amylase (Cerning Beroard and Le Dividich 1976). Amino acid analysis of sweet potato tubers indicates them to be of good nutritional quality but deficient in total sulfur amino acids and lysine (Fuller and Chamberlain 1982).

Sweet potato tuber and foliage have been evaluated as feed for poultry. Turner et al (1976) examined various diets consisting of cooked sweet potato as a supplement for poultry. Chicks fed on a starter feed reached slaughter weight sooner than when fed on sweet potato diets. However, with the latter, the broilers had a higher dressing out percentage. Yoshida and Morimoto (1958) reported the carbohydrate fraction in sweet potato to be about 90 % digestible in chicks. Tewe (1994) reported that using sun-dried and oven-dried sweet potato replacing maize at 0, 50, and 100% in broiler rations reduced body weight gain and nutrient utilization when compared with the maize-based control diet. The broiler performance was better with the oven-dried rations, and it can replace maize at up to 50% in broiler rations. Performance was optimal at 30% replacement of maize with sweet potato.

Anti-nutritional factors in sweet potato tuber

Sweet potatoes contain trypsin inhibitors, ranging from 90 % in some varieties to 20 % in others (Lin & Chen 1985) which may reduce the ability of animals to utilize protein if eaten raw. These anti-nutritional factors also caused low dry matter digestibility and low metabolizable protein and energy values, even when the rations contained adequate and high quality proteins in animal feed (Gerpacio et al 1978). However, these trypsin inhibitors do not survive cooking and are of no consequence in cooked tubers (Collins 1995). Preheating can also destroy or reduce these trypsin inhibitors. Therefore, cooking is necessary on account of two factors, starch digestibility and the presence of trypsin inhibitor. Sasi Kiran and Padmaja (2003) reported that when sweet potato tuber was cooked, between 17 and 31 % trypsin inhibitor activity remained and when it was prepared into flour, only 5-12 % trypsin inhibitor activity was found.   

3.4.3 Banana fruit (Musa acuminata Colla)

In the uplands of Cambodia and Laos, the banana is usually grown by farmers and sold for cash. The fruits are sold at a low price, especially those fallen from the bunch, and are bought to use as monkey or human feed, for example as roasted banana and banana rice cake. Farmers get less benefit if they sell these undesirable bananas, but they can be processed for use as animal feed. Feeding bananas to animals has been relatively neglected. This is largely because bananas are principally a human food, but is also partly attributable to the fact that their value as animal feed has not been adequately studied (Chenost et al 1969; FAO 1969). FAO (1975) reported that an estimated 7 to 10 million tons of the 36 million ton world banana production per year (20 to 30 %) could be recovered for use as animal feed.

Composition and utilization of banana fruit for poultry

The composition of all banana varieties is determined chiefly by degree of ripeness. Bananas have high water content (78 to 80 %), and in the green state, at which they are generally picked and packed, the dry matter consists mainly of starch (72 %), which on ripening changes into simple sugars (saccharose, glucose and fructose). The cellulose content is low (3 to 4 %) and most of it is found in the skin. The inorganic fraction is poor, with low levels of Ca and P, but it is rich in K. Whether green or ripe, the banana has low protein content and is deficient in lysine and in the sulphur-containing amino acids (2.3– 2.9 g/16 g N) (Le Dividich et al 1976).

In banana exporting countries, large quantities of rejected bananas are often available for animal feed. Banana fruits were seen to be used for pig feeding in the fresh and ripe form (Le Dividich and Canope 1975). They can also be used for ruminant feeding in the form of pulp flour, or fresh or ensiled fruit (Thivend et al 1972; Spiro 1973; Rihs et al 1975). There seems to be little or no research on the use of fresh banana fruit for poultry. From personal observations, chickens eat banana if they find it on the ground. Banana in the form of meal has been used in poultry diets, but high levels tend to depress growth and reduce feed efficiency (Sharrock 1996).

Anti-nutritional factors in banana fruit

While banana is generally harmless to humans and animals, it does contain substances that are harmful when ingested in high quantities. The substances found in banana are tannins (3.40 mg/g), oxalate (4.50 mg/g) and phytate (2.88 mg/g). However, the concentration of these anti-nutrients is not particularly high, which means it needs little or no processing before it is used for human and animal feed (Onibon et al 2007). Moreover, tannins in banana are only slightly polymerized in the green fruit and therefore inhibit the action of enzymes. In the ripe fruit, however, polymerization is higher (Le Dividich et al 1976).

4. Conclusions
 

·         Most smallholders in developing countries raise indigenous chickens, and these scavenging village chickens play a significant role in poverty alleviation.

·         The cafeteria feeding system is a popular method for scavenging chickens, which gives them the opportunity to select nutrients according to their physiological demands.

·         Providing available carbohydrate feeds, such as cassava root, sweet potato tuber and banana fruit for scavenging birds provides energy to support their activities in searching for their required food.

·         Some green forages, such as duckweed, water spinach and taro leaf are also important in the scavenging system as they provide protein, minerals and vitamins to enhance the growth of the scavenging chicken.

5. Acknowledgements

I wish to thank and express my appreciation to the MEKARN project, financed by Sida/SAREC, for supporting my research. I also express my sincere gratitude to my supervisors, Professor Brian Ogle, MEKARN International Coordinator, Dr. Thomas Preston, Director of UTAF, Colombia and Adviser to MEKARN and Dr. Khieu Borin, Director of CelAgrid, for their patient and valuable guidance and advice during my experiments and for their help in correcting my thesis. Acknowledgements are also expressed to all lecturers during the MSc courses.

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