The use of cassava leaf silage as a feed supplement in diets for ruminants and its introduction to smallholder farmers

Marjuki, H E Sulistyo, D W Rini, I Artharini, Soebarinoto and R Howeler*

Animal Nutrition Department, Faculty of Animal Husbandry, Brawijaya University, Malang, Indonesia - 65145
* The International Center for Tropical Agriculture (CIAT), Chatuchak, Bangkok, Thailand - 10900
marjuki4663@yahoo.com

Abstract

Introduction of cassava leaf silage making to smallholder farmers and its feeding to ruminants in cassava crop growing areas were investigated through laboratory and on-farm feeding trials, extension services and training. This with the aim to evaluate the response of the ruminants on cassava leaf silage feeding and the adoption of the technology by farmers.

Fifteen male sheep aged 6-8 months with an initial body weight of 15.8 + 2.6 kg were used in a laboratory feeding trial and allotted to 3 treatments with 5 replications in a randomized block experiment design. The sheep were fed on chopped elephant grass and three different levels of cassava leaf silage as treatment. The three levels of supplementation of casava leaf silage (DM in % of body weight) were: 0, 0.75, and 1.5, which represented treatments A, B, and C, respectively, and the rest of the feed was elephant grass to reach a total DM intake in % of body weight of 5. The individual sheep was weighed every second week to measure their body weight changes. An on-farm feeding trial was conducted in collaboration with the farmers as target persons.

The results showed that feeding increasing amounts of cassava leaf silage as a feed supplement for sheep significantly increased digestible crude protein (CP) intake and nitrogen retention, and this was also associated with an increase in average daily weight gain from 41.4 to 45.0 and 50.0 g/head/day, respectively, on treatments A, B and C. Cassava leaf has been commonly used as a feed for ruminant animals by smallholder farmers, but only during the cassava crop harvesting season, where the leaf was abundantly available. It was fed in fresh form, either as single or combined feed. Preservation of forages including cassava leaf in the form of hay or silage was not well known by the farmers in this study. The farmers showed good response on the introduced technology of cassava leaf silage making and feeding to their ruminant livestock. They noticed that cassava leaf silage showed higher palatability over the forages they have normally used to feed their livestock. The farmers have practiced the technology, but they lack equipments, especially chopping machine for a larger scale application of the technology.

Keywords: cassava leaf, intake, nitrogen retention, ruminants, weight gain

Introduction

Cassava is one of the major crops planted in Indonesia after rice. It is cultivated throughout the country with Lampung and East Java as the two major cassava-producing provinces. The total area of cassava cultivation in Indonesia in 2003 was over 1.24 million ha, with a total production of 18.5 million ton cassava. Indonesia is the fifth largest cassava producer in the world after Brazil, Thailand, Nigeria, and Zaire or the second of the largest cassava producer in Asia after Thailand (O’Hair 1995, FAOSTAT 2006).

Cassava is cultivated in Indonesia mainly for food and tapioca flour, but recently it is also widely used in livestock feeding. Almost all parts of the cassava plant including its by-products are used as livestock feed. Cassava leaves are the most common part of cassava used as feed by farmers in the villages. It contains quite high crude protein up to 25 % on dry matter (DM) basis, a nutrient which is generally deficient in feeds for livestock in the tropics. Thus, it can potentially be used as a protein source for livestock. However, cassava leaf production is only concentrated during cassava tubers harvest, thus, these are abundantly available only in short periods of time. Feeding such high protein forage as a single feed to ruminants, as commonly practiced by farmers during the season when casave leaf is abundantly available, is not an efficient feeding practice. This because the excess protein consumed by ruminants will be excreted mainly in the urine and feces, and it requires a lot of  energy for the animal to metabolize and excrete the excess protein intake in this way (McDonald et al 1988). As other forages, cassava leaf can not stand for long time without any treatment, consequently the excess of cassava leaf are sometimes left in the field underutilized.

Preservation of the excess of cassava leaf available, such as through silage making, will maximize and improve the efficiency of the excess cassava leaf utilization as feed. As silage, the excess of cassava leaf available can be stored and utilized for a longer period of time as a protein feed supplement.  Hang (1998), Kayouli and Lee (2000), Ly and Rodríguez (2001) reported that silage making is an appropriate method to conserve cassava leaf as feed. Feeding cassava leaf silage has been reported to increase livestock productivity including milk yield (IITA Annual Report 2004, Kavana et al 2005), body weight gain (Nhi et al 2001, Bunyeth and Preston 2006).  

To improve utilization of cassava leaf as feed it was introduced cassava leaf silage making and its feeding to ruminant to smallholder farmers in cassava crops growing area through laboratory and on-farm feeding trial, extension services and training. This research aimed to evaluate the response of ruminants on cassava leaf silage feeding and the adoption of the technology by farmers

Methodology 

Laboratory feeding trial

This experiment was conducted at the Livestock Research Station, Faculty of Animal Husbandry, Brawijaya University, Malang, Indonesia for two months including two weeks of adaptation period.

Fifteen male sheep aged 6-8 months with an initial body weight of 15.8 + 2.6 kg were allotted to 3 treatments with 5 replications in a randomized block experiment design. The sheep were blocked into 5 based on their initial body weight and put in individual metabolism cages equipped with plastic net and plastic sheet underneath to facilitate separately collection of urine and feces.

Feed composed of chopped elephant grass and supplemented with three different levels of cassava leaf silage as treatment were given. The three levels of supplementation of cassava leaf silage (DM in % of body weight) were 0, 0.75,  and 1.5% which represented for treatment A, B, and C, respectively and the rest feed was elephant grass to reach a total amount of feed DM offered of 5% body weight of individual sheep. The individual sheep was weighed every second week to measure their body weight changes. The amount of feed offered was adjusted every second week based on the actual weight of the individual sheep, and drinking water was offered ad libitum.

During the experiment, daily amount of feed offered and refused, feces and urine excreted by individual sheep were weighed and their samples were taken for proximate analysis of DM, organic matter (OM) and crude protein (CP) content to measure feed intake, feed digestibility and nitrogen retention. DM, OM and CP content of the feeds used in this experiment are presented in Table 1.

Cassava leaf silage was prepared according to the procedure below :

1.     Cassava leaf including young stems, petioles and leaf were harvested from farmer’s cassava field when the tubers were being harvested.

2.     The leaf were spread out on a roofed and well ventilated floor for a night to let them be wilt, then chopped using a hand operated chopping machine.

3.     The chopped cassava leaf was weighed and then thoroughly mixed with wet cassava waste at a weight ratio of 4 parts of the chopped cassava leaf : 1 part of wet cassava waste.

4.     The mixture was then put in polypropylene plastic bag of 60 cm width by 100 cm length and compacted to expel air from the bag.

5.     The bags were then tightened using rubber bands and stored for three months.

Introduction of cassava leaf silage making to farmers

Introduction of cassava leaf silage making to farmers was conducted in the dry land area, where most of farmers grow cassava crops. The activity aimed to evaluate the response of ruminants on cassava leaf silage feeding and the adoption of cassava leaf silage making and its utilization as a feed supplement in diets for ruminants by farmers..

Survey of utilization of cassava leaf as a feed by farmers

The activity was started with a survey, which focused on the utilization of cassava leaf as a feed. Seventeen sheep, goat, or cattle rearing farmers either with or with no cassava crops on their land were interviewed using a structured questionnaire covering feeding practices for the livestock, did they use cassava leaf as feed for their livestock, why, when and how, percentage in the ration (mixed with other feeds or alone),  how did they get the cassava leaves to feed, when was there an excess of cassava leaf production during harvesting season of cassava crops, how did they utilize the leaves, and had they ever heard about cassava leaf preservation as a feed, if yes, from where (source of the information) and what was their response and did they practice the technology, if no, we explained how to and observed their response.

Extension  services and demonstration plot for cassava leaf silage making and feeding to ruminant livestock

After the survey, all the interviewed farmers were invited for a meeting which aimed 1) to clarify the survey data, 2) to give extension services to the farmers on cassava leaf preservation method as feed, and 3) to talk about the next plan for training of cassava leaf silage making and demonstration of utilization of cassava leaf silage as a feed supplement in diets for ruminants including sheep, goat and cattle reared by the farmers. During the extension services, the advantages of using cassava preserved leaf as a feed and how to practice the technology was explained, and samples of ready made cassava leaf silage to the farmers were shown. The extension services was continued with training of farmers on cassava leaf silage making and demonstration of cassava leaf silage feeding to ruminants. Same procedure of cassava leaf silage making as in the previous experiment was applied.

Demonstration of feeding cassava leaf silage was conducted for two weeks at the farms of four farmer’s, who were rearing sheep or goats (2 to 4 heads per farm) and two others farmers who were rearing cattle (two heads per farm). The demonstration was designed especially to show to the farmers the palatability of cassava leaf silage for their livestock. Cassava leaf silage was given fresh as a feed supplement to the basal diet normally given by the farmers at a level of approximately 3 % pe day of total body weight of sheep, goats or cattle in the flock. During the demonstration, the response of the livestock and the farmers on feeding cassava leaf silage was observed.

Results and discussions 

Laboratory feeding trial

Cassava leaf silage and its palatability by sheep

As presented in Table 1, DM and CP content of cassava leaf silage used in this experiment were 33.4 % and 16.5 % DM, respectively, which were in the same range as reported previously by Nhi et al (2001). DM content of the silage was higher than those contained in its fresh ? components, cassava leaves and cassava waste. This was mostly due to water evaporation during the silage making process, especially during wilting time. While higher OM and lower CP content of the silage as compared to those in cassava leaf was due to dilution of the nutrients by cassava waste.

The first time the cassava leaf silage was fed to the sheep in this experiment, some sheep immediately consumed the silage, but most of the sheep needed a period of 4 to 7 days of adaptation before the normal consumption was reached, where refusal rate was no more than 10% of offered feed. Thereafter, all sheep entirely consumed the cassava leaf silage given, except some sheep which consumed only the leaf and softer stem parts but left over the harder stem and petiole parts of the silage. Data for refusal rate of cassava leaf silage by sheep are presented in Table 2.

Feed intake and weight gain of sheep supplemented with cassava leaf silage

Data on the effects of cassava leaf supplementation on feed intake and bodyweight gain are presented in Table 2.

The data showed that although DM and digestible OM intake was highest on treatment A (no casava leaf silage supplementation), digestible CP intake in this treatment was, however, the lowest on this treatment. Inclusion of cassava leaf silage in the ration therefore improved the  CP content and digestibility of the ration significantly, as expected since CP content of cassava leaf silage was twice as high as CP content of the elephant grass. In addition, nitrogen retention also increased with increasing protein intake from treatment A to treatments B and C.  The significant increases in digestible CP intake and nitrogen retention from treatment A to treatments B and C due to cassava leaf silage supplementation were also associated with an increase of average daily weight gain from 41.4 to 45.0 and 50.0 g/head/day, respectively.

Thus, cassava leaf silage has potential as a protein feed supplement to improve livestock productivity. As stated by Preston and Leng (1987), protein is the nutrient most often deficient, and this deficiency can hamper livestock productivity in the tropics. Cassava leaf silage thus has the potential to serve as a protein bank to correct nutrient deficiency, especially during the dry season where most of ruminant livestock are fed low protein diets based predominantly on crop-residues and native grass.

Introduction of cassava leaf silage making to farmers

Farmers view of cassava leaf as a feed for ruminant livestock

The survey data showed that cassava leaf is a common forage fed to either sheep, goats or cattle in the area of study. All farmers surveyed fed cassava leaf to their livestock, especially during the cassava crop harvesting season. Their main reasons were that during this period, cassava leaf was much easier and faster to collect as compared to other forages (stated by 16 out of 17 farmers surveyed), mainly during cassava crops harvest in the dry season where other forages were available in limited amounts. Fifteen farmers stated that cassava leaf also showed good palatability and only 4 farmers who argued to select cassava leaf as feed due to its good effect on livestock performance, including body condition score and shiny hair. The last argument may be due to the fact that the other farmers did not actually notice the effect of feeding a certain feed like cassava leaf on the performance of their livestock, since the farmers fed their livestock long-term not with only one single feed, but rather mixed with other forages.

All farmers fed cassava leaf to their livestock in fresh condition just few hours after harvested from the field. Cassava leaf were fed as whole and un-chopped, including softer stems, leaf and petioles. Mostly the farmers fed cassava leaf as a single feed especially to goats and sheep, but sometimes leaves were also mixed with other forages mainly to cattle.

Cassava leaf is a by-product of cassava crops when the tubers are being harvested. It is free of cost forage as other agriculture by-products such as rice straw, maize tops or sugar cane tops. Not only the owners who can get the forage, but also other farmers especially their neighbours and relatives.  But, there is a local informal rule that before the other farmers can get the forages, they must help the cassava crop owner to pull cassava tubers out. The amount of cassava leaf which they can collect is usually as much as the cassava crop they have pulled out, that is generally one to two bundles of 25 to 30 kg per bundle per farmer. Sometimes workers who are paid for harvesting the tubers also bring the forages home for their livestock. Thus, almost no cassava leaf are left in the field, except when big areas of cassava are being harvested at the same time, hence some of the excess cassava leaf are not utilized but left in the field. This is especially so when the cassava harvest season is at its peak or when the cassava crop harvest is in the rainy season where other forages are also available in abundance.

Feeding cassava leaf was not done every day for long term periods by the farmers. The feeding depends mainly on the availability of cassava leaf around the farmers’ farms. Cassava leaf is available only during the cassava crop harvest in the season, which is from July to January or February, with its peak in October and November. The farmers generally collected cassava leaf for only one or two days feeding or one to two bundles of 25 to 30 kg per bundle per day. It is not common for farmers to prune cassava leaf as feed.

Different from utilization of fresh cassava tubers as feed where the farmers prefer to use sweet variety cassava tubers, there is no farmers’ preference for cassava leaf varieties as feed for their livestock. But to reduce the risk of poisonous effects on livestock from the bitter cassava leaf variety, the farmers wilt the cassava leaves for a few hours prior to feeding to livestock especially for the first times of feeding.

No farmers stored or preserved cassava leaf as feed neither as hay nor silage. Lack of information and knowledge about the technologies are their main reasons for not doing this. Introduction of the technologies especially cassava leaf silage making through personal communication, extension services, training and establishment of demonstration plots got good response from the farmers.

Demonstrations of feeding cassava leaf silage to ruminants

Most of sheep, goats and cattle in the area of study are reared by smallholder farmers with an average ownership of 2 to 5 heads of sheep or goats or 1 to 2 heads of cattle per farm. Feeds for the livestock are every day collected from communal lands, especially from forest and rice fields or other agricultural lands under cut and carry systems. Most of feeds collected for sheep and goat feeding are native grasses, tree leaves, especially calliandra, gliricidia, thitonia,  and sometimes crop-residues such as maize tops, ground nut leaves, sweet potato vines and cassava leaves. In addition, rice straw and sugar cane top are also used as cattle feed. Concentrate feed are almost never given to livestock by farmers. Nutrient content of the feeds commonly used by farmers for cattle, sheep and goats as compared with cassava leaf silage is presented in Table 3.

It can be seen from Table 3 that cassava leaf either fresh or as silage is a good protein source with crude protein contents comparable to that of leaves, especially leguminous one and higher than the crude protein content of grasses and crop residues.

Plots for demonstration of feeding cassava leaf silage as feed supplement to cattle, sheep and goats revealed that all cattle, some sheep and goats immediately consumed all parts of the cassava leaf silage, including stems and petiole, even when cassava leaf silage was given for the first time. However, as in the laboratory feeding trial, most of the sheep and goats needed a few days of adaptation before they were willing to consume all the silage. Some sheep and goats selected only the leaf part of silage and left the harder stems and mostly petioles. When grass and casava leaf silage were fed together, the goats preferred to consume the casava leaf silage first rather than the grass (Figure1).  

The farmers noticed that cassava leaf silage was highly palatable for their livestock. In principle, they were interested in adopting the technology especially to preserve cassava leaf harvested in the rainy season as the other forages are also abundantly available, and some farmers did not use cassava leaf harvested in the rainy season as feed. There is an issue among the farmers that cassava leaf harvested in the rainy season may be more poisonous to livestock than those harvested in the dry season. Thus, most of cassava leaf harvested in the rainy season are left in the field underutilized. Preservation of the excess of cassava leaf in the form of silage can reduce the risk. Tewe (1992), Limon (1992), Ty et al (2001), Kavana et al (2005), Borin et al (2005) reported that ensiling has been as an effective way of reducing the content of cyanide (HCN) which is a poisonous agent for livestock contained in cassava leaves. Kavana et al (2005) reported that ensiling the mixture of cassava leaves and chips in 4 : 1 ratio reduced level of HCN from critical harmfull level of 289 to a save level of 20 mg/kg in DM basis after 3 months. Gómez (1991), Harris and Shearer (2003) stated that HCN in animal feeds at level of 100 to 150 ppm is possibly hazardous and at level of higher than 150 ppm is dangerous for animal.

However, to make larger quantities of cassava leaf silage for longer period of feeding, the farmers need some supporting equipments especially chopping machines instead of chopping manually using a knife, which is very labour intensive. In addition, some farmers who have no land or cassava crops speculated that cassava leaf silage making could change the existing sharing system with regards to utilizing cassava leaf as feed among farmers when the cassava crops are being harvested. The owners of cassava crops may turn to utilize most of the cassava leaf harvested for their own livestock.

Conclusion 

·     The use of cassava leaf silage as a protein feed supplement improved sheep performance.

·     Cassava leaf silage was highly palatable for sheep.

·     The farmers were interested in adopting the technology of cassava leaf preservation as a feed, especially silage making.

Acknowledgements 

The authors wish to acknowledge the Australian Centre for International Agricultural Research (ACIAR) for the financial support and the International Center for Tropical Agriculture (CIAT) for their assistance in organizing this project. To all farmers who participated in this project, we would also like to convey our sincere gratitude.

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Received 30 January 2008; Accepted 22 February 2008; Published 10 June 2008

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